HANDBOOK 2 DESIGN OF TIMBER STRUCTURES ACCORDING TO EUROCODE 5

Transcription

1 HANDBOOK DESIGN OF TIMBER STRUCTURES ACCORDING TO EUROCODE 5

2 Preace This hanboo maes speciic reerence to esign o timber structures to European Stanars an using proucts available in Europe. The hanboo is closely line to Eurocoe 5 (EC5), the European coe or the esign o timber structures. This hanboo is explaining the general philosophy o the Eurocoe 5 an giving the basic bacgroun or its requirements an esign rules. For better unerstaning o the Eurocoe 5 esign rules the wore examples are presente. The purpose o this hanboo is to introuce reaers to the esign o timber structures. It is esigne to serve either as a text or a course in timber structures or as a reerence or systematic sel-stuy o the subject. May 008 Authors

3 Contents 1 Introuction... 5 Design o timber structures... 6 Design values o material properties Woo ahesives Durability Ultimate limit states... 7 Serviceability limit states Connections with metal asteners Components Mechanically jointe beams Built-up columns Wore examples Literature Normative reerences

4 1 Introuction From the earliest years o recore history, trees have provie manin with oo an materials or shelter, uel an tools. Timber is one o the earliest builing materials use by our preecessors, an most o us experience a strong ainity with the beauty an intrinsic characteristics o this natural material when timber is use in the places we wor an live. Timber is the olest nown builing material capable o transerring both tension an compression orces - maing it naturally suite as a beam element. It has a very high strength to weight ratio, it is relatively easy to abricate an to join, it oten out-perorms alternative materials in hazarous environments an extremes o temperature (incluing ire), it oes not corroe an many species i etaile correctly can be very urable. The unique properties o timber have mae it a cornerstone contributor to the avance o civilisation an evelopment o society as we now it toay. Timber has been use in the construction o builings, briges, machinery, war engines, civil engineering wors an boats etc. since manin irst learnt to ashion tools. Timber is a truly remarable material. Whilst most o the structural materials we use are processe rom inite resources, requiring enormous amounts o energy an proucing signiicant green house emissions, timber is grown using solar energy, in natural soil which is ertilise by its own compost, uelle by carbon ioxie an watere by rain. Because it literally grows on trees, timber is the only structural engineering material which can be totally renewe - provie that trees are replante (plantations) or naturally regenerate (native orests) ater elling! At the same time orests provie a number o unique an varie beneits that inclue protection o our climate, water an soil an a great range o recreational unctions enjoye by the general public. Forests, orest base inustries, the services, goos an proucts they provie aect irectly the aily lie o any o the 450 M Europe s Citizen. Within the EU countries, the orests cover 140 millions hectares which accounts or 6 % o lan area on an average, ranging rom 1 % in Cyprus to 71 % in Finlan. Europe s orests are extening in area, increasing in growth rate, an expaning in staning volume. From an engineering point o view, timber is ierent rom woo. Woo is the substance o which the truns an branches o trees are mae, which is cut an use or various purposes. Timber is woo or builing. In the hans o sille proessionals who have an appreciation an unerstaning o its natural characteristics, timber has signiicant avantages over alternative structural materials, enhancing the best esigns with a sense o appropriateness, unity, serenity an warmth in achieving the marriage o orm an unction, which is simply not possible with concrete an steel. 5

5 Design o timber structures Beore starting ormal calculations it is necessary to analyse the structure an set up an appropriate esign moel. In oing this there may be a conlict between simple, but oten conservative, moels which mae the calculations easy, an more complicate moels which better relect the behaviour but with a higher ris o maing errors an overlooing ailure moes. The geometrical moel must be compatible with the expecte wormanship. For structures sensitive to geometrical variations it is especially important to ensure that the structure is prouce as assume uring esign. The inluence o unavoiable eviations rom the assume geometry an o isplacements an eormations uring loaing shoul be estimate. Connections oten require large areas o contact an this may give rise to local excentricities which may have an important inluence. Oten there is a certain reeom as regars the moelling as long as a consistent set o assumptions is use. The Eurocoes are limit state esign coes, meaning that the requirements concerning structural reliability are line to clearly eine states beyon which the structure no longer satisies speciie perormance criteria. In the Eurocoe system only two types o limit states are consiere: ultimate limit states an serviceability limit states. Ultimate limit states are those associate with collapse or with other orms o structural ailure. Ultimate limit states inclue: loss o equilibrium; ailure through excessive eormations; transormation o the structure into a mechanism; rupture; loss o stability. Serviceability limit states inclue: eormations which aect the appearance or the eective use o the structure; vibrations which cause iscomort to people or amage to the structure; amage (incluing cracing) which is liely to have an averse eect on the urability o the structure. In the Eurocoes the saety veriication is base on the partial actor metho escribe below..1 Principles o limit state esign The esign moels or the ierent limit states shall, as appropriate, tae into account the ollowing: ierent material properties (e.g. strength an stiness); ierent time-epenent behaviour o the materials (uration o loa, creep); ierent climatic conitions (temperature, moisture variations); ierent esign situations (stages o construction, change o support conitions)..1.1 Ultimate limit states The analysis o structures shall be carrie out using the ollowing values or stiness properties: or a irst orer linear elastic analysis o a structure, whose istribution o internal orces is not aecte by the stiness istribution within the structure (e.g. all members have the same time-epenent properties), mean values shall be use; or a irst orer linear elastic analysis o a structure, whose istribution o internal orces is aecte by the stiness istribution within the structure (e.g. composite members 6

6 containing materials having ierent time-epenent properties), inal mean values ajuste to the loa component causing the largest stress in relation to strength shall be use; or a secon orer linear elastic analysis o a structure, esign values, not ajuste or uration o loa, shall be use. The slip moulus o a connection or the ultimate limit state, K u, shoul be taen as: Ku Kser (.1) where K ser is the slip moulus..1. Serviceability limit states The eormation o a structure which results rom the eects o actions (such as axial an shear orces, bening moments an joint slip) an rom moisture shall remain within appropriate limits, having regar to the possibility o amage to suracing materials, ceilings, loors, partitions an inishes, an to the unctional nees as well as any appearance requirements. The instantaneous eormation, u inst, see Chapter 7, shoul be calculate or the characteristic combination o actions using mean values o the appropriate mouli o elasticity, shear mouli an slip mouli. The inal eormation, u in, see Chapter 7, shoul be calculate or the quasi-permanent combination o actions. I the structure consists o members or components having ierent creep behaviour, the inal eormation shoul be calculate using inal mean values o the appropriate mouli o elasticity, shear mouli an slip mouli. For structures consisting o members, components an connections with the same creep behaviour an uner the assumption o a linear relationship between the actions an the corresponing eormations the inal eormation, u in, may be taen as: u u + u + u (.) in in,g in,q1 in,qi ( 1 ) u u + or a permanent action, G (.) in,g inst,g e ( 1 ψ ) u u + or the leaing variable action, Q 1 (.4) in,q,1 inst,q,1,1 e ( ψ ψ ) u u + or accompanying variable actions, Q i (i > 1) (.5) in,q,i inst,q,i 0,i,i e u inst,g, u inst,q,1, u inst,q,i are the instantaneous eormations or action G, Q 1, Q i respectively; ψ,1, ψ,i ψ 0,i e are the actors or the quasi-permanent value o variable actions; are the actors or the combination value o variable actions; is given in Chapter or timber an woo-base materials, an in Chapter or connections. 7

7 For serviceability limit states with respect to vibrations, mean values o the appropriate stiness mouli shoul be use.. Basic variables The main variables are the actions, the material properties an the geometrical ata...1 Actions an environmental inluences Actions to be use in esign may be obtaine rom the relevant parts o EN Note 1: The relevant parts o EN 1991 or use in esign inclue: EN Densities, sel-weight an impose loas EN Snow loas EN Win actions EN Thermal actions EN Actions uring execution EN Acciental actions Duration o loa an moisture content aect the strength an stiness properties o timber an woo-base elements an shall be taen into account in the esign or mechanical resistance an serviceability. Loa-uration classes The loa-uration classes are characterise by the eect o a constant loa acting or a certain perio o time in the lie o the structure. For a variable action the appropriate class shall be etermine on the basis o an estimate o the typical variation o the loa with time. Actions shall be assigne to one o the loa-uration classes given in Table.1 or strength an stiness calculations. Table.1 Loa-uration classes Loa-uration class Permanent Long-term Meium-term Short-term Instantaneous Orer o accumulate uration o characteristic loa more than 10 years 6 months 10 years 1 wee 6 months less than one wee NOTE: Examples o loa-uration assignment are given in Table. 8

8 Table. Examples o loa-uration assignment Loa-uration class Permanent Long-term Meium-term Short-term Instantaneous Examples o loaing sel-weight storage impose loor loa, snow snow, win win, acciental loa Service classes Structures shall be assigne to one o the service classes given below: NOTE: The service class system is mainly aime at assigning strength values an or calculating eormations uner eine environmental conitions. Service class 1 is characterise by a moisture content in the materials corresponing to a temperature o 0 C an the relative humiity o the surrouning air only exceeing 65 % or a ew wees per year. NOTE: In service class 1 the average moisture content in most sotwoos will not excee 1 %. Service class is characterise by a moisture content in the materials corresponing to a temperature o 0 C an the relative humiity o the surrouning air only exceeing 85 % or a ew wees per year. NOTE: In service class the average moisture content in most sotwoos will not excee 0 %. Service class is characterise by climatic conitions leaing to higher moisture contents than in service class... Materials an prouct properties Loa-uration an moisture inluences on strength Moiication actors or the inluence o loa-uration an moisture content on strength are given in Chapter. Where a connection is constitute o two timber elements having ierent time-epenent behaviour, the calculation o the esign loa-carrying capacity shoul be mae with the ollowing moiication actor mo: mo mo,1 mo, (.6) where mo,1 an mo, are the moiication actors or the two timber elements. 9

9 Loa-uration an moisture inluences on eormations For serviceability limit states, i the structure consists o members or components having ierent time-epenent properties, the inal mean value o moulus o elasticity, E mean,in, shear moulus, G mean,in, an slip moulus, K ser,in, which are use to calculate the inal eormation shoul be taen rom the ollowing expressions: E G K mean,in mean,in ser,in E mean ( 1+ ) G e mean ( 1+ ) K ser e ( 1+ ) e (.7) (.8) (.9) For ultimate limit states, where the istribution o member orces an moments is aecte by the stiness istribution in the structure, the inal mean value o moulus o elasticity, E mean,in, shear moulus,g mean,in, an slip moulus, K ser,in, shoul be calculate rom the ollowing expressions : E G K mean,in mean,in ser,in E mean G mean K ser e ψ E mean ( 1+ ψ ) G e mean ( 1+ ψ ) K ser e ( 1+ ψ ) e is the mean value o moulus o elasticity; is the mean value o shear moulus; is the slip moulus; (.10) (.11) (.1) is a actor or the evaluation o creep eormation taing into account the relevant service class; is the actor or the quasi-permanent value o the action causing the largest stress in relation to the strength (i this action is a permanent action, ψ shoul be replace by 1). NOTE 1: Values o e are given in Chapter. NOTE : Values o ψ are given in EN 1990:00. Where a connection is constitute o timber elements with the same time-epenent behaviour, the value o e shoul be ouble. Where a connection is constitute o two woo-base elements having ierent time-epenent behaviour, the calculation o the inal eormation shoul be mae with the ollowing eormation actor e : 10

10 (.1) e e,1 e, where e,1 an e, are the eormation actors or the two timber elements.. Veriication by the partial actor metho A low probability o getting action values higher than the resistances, in the partial actor metho, is achieve by using esign values oun by multiplying the characteristic actions an iviing the characteristic strength parameters, by partial saety actors...1 Design value o material property The esign value X o a strength property shall be calculate as: X X γ M mo X mo (.14) γ M is the characteristic value o a strength property; is the partial actor or a material property; is a moiication actor taing into account the eect o the uration o loa an moisture content. NOTE 1: Values o mo are given in Chapter. NOTE : The recommene partial actors or material properties (γ M ) are given in Table.. Inormation on the National choice may be oun in the National annex o each country. Table. Recommene partial actors γ M or material properties an resistances Funamental combinations: Soli timber 1, Glue laminate timber 1,5 LVL, plywoo, OSB, 1, Particleboars 1, Fibreboars, har 1, Fibreboars, meium 1, Fibreboars, MDF 1, Fibreboars, sot 1, Connections 1, Punche metal plate asteners 1,5 Acciental combinations 1,0 The esign member stiness property E or G shall be calculate as: 11

11 E G E γ mean (.15) G γ M mean (.16) M E mean is the mean value o moulus o elasticity; G mean is the mean value o shear moulus... Design value o geometrical ata Geometrical ata or cross-sections an systems may be taen as nominal values rom prouct stanars hen or rawings or the execution. Design values o geometrical imperections speciie in this hanboo comprise the eects o geometrical imperections o members; the eects o structural imperections rom abrication an erection; inhomogeneity o materials (e.g. ue to nots)... Design resistances The esign value R o a resistance (loa-carrying capacity) shall be calculate as: R R γ M R mo (.17) γ M is the characteristic value o loa-carrying capacity; is the partial actor or a material property, mo is a moiication actor taing into account the eect o the uration o loa an moisture content. NOTE 1: Values o mo are given in Chapter. NOTE : For partial actors, see Table.. 1

12 Design values o material properties Eurocoe 5 in common with the other Eurocoes provies no ata on strength an stiness properties or structural materials. It merely states the rules appropriate to the etermination o these values to achieve compatibility with the saety ormat an the esign rules o EC5..1 Introuction Strength an stiness parameters Strength an stiness parameters shall be etermine on the basis o tests or the types o action eects to which the material will be subjecte in the structure, or on the basis o comparisons with similar timber species an graes or woo-base materials, or on wellestablishe relations between the ierent properties. Stress-strain relations Since the characteristic values are etermine on the assumption o a linear relation between stress an strain until ailure, the strength veriication o iniviual members shall also be base on such a linear relation. For members or parts o members subjecte to compression, a non-linear relationship (elasticplastic) may be use. Strength moiication actors or service classes an loa-uration classes The values o the moiication actor mo given in Table.1 shoul be use. I a loa combination consists o actions belonging to ierent loa-uration classes a value o mo shoul be chosen which correspons to the action with the shortest uration, e.g. or a combination o ea loa an a short-term loa, a value o mo corresponing to the shortterm loa shoul be use. Material Stanar Service class Soli timber EN Glue EN laminate timber LVL EN 1474, EN 1479 Plywoo Table.1 Values o mo Loa-uration class Permanent Long Meium action term term action action Short term action Instantaneous action 1 0,60 0,70 0,80 0,90 1,10 0,60 0,70 0,80 0,90 1,10 0,50 0,55 0,65 0,70 0,90 1 0,60 0,70 0,80 0,90 1,10 0,60 0,70 0,80 0,90 1,10 0,50 0,55 0,65 0,70 0,90 1 0,60 0,70 0,80 0,90 1,10 0,60 0,70 0,80 0,90 1,10 0,50 0,55 0,65 0,70 0,90 EN 66 Part 1, Part, Part 1 0,60 0,70 0,80 0,90 1,10 Part, Part 0,60 0,70 0,80 0,90 1,10 Part 0,50 0,55 0,65 0,70 0,90

13 OSB Particleboar Fibreboar, har Fibreboar, meium Fibreboar, MDF EN 00 OSB/ 1 0,0 0,45 0,65 0,85 1,10 OSB/, OSB/4 1 0,40 0,50 0,70 0,90 1,10 OSB/, OSB/4 0,0 0,40 0,55 0,70 0,90 EN 1 Part 4, Part 5 1 0,0 0,45 0,65 0,85 1,10 Part 5 0,0 0,0 0,45 0,60 0,80 Part 6, Part 7 1 0,40 0,50 0,70 0,90 1,10 Part 7 0,0 0,40 0,55 0,70 0,90 EN 6- HB.LA, HB.HLA 1 or 1 0,0 0,45 0,65 0,85 1,10 HB.HLA1 or 0,0 0,0 0,45 0,60 0,80 EN 6- MBH.LA1 or MBH.HLS1 or 1 1 0,0 0,0 0,40 0,40 0,60 0,60 0,80 0,80 1,10 1,10 MBH.HLS1 or 0,45 0,80 EN 6-5 MDF.LA, MDF.HLS 1 0,0 0,40 0,60 0,80 1,10 MDF.HLS 0,45 0,80 Deormation moiication actors or service classes The values o the eormation actors e given in Table. shoul be use.. Soli timber Timber members shall comply with EN Timber members with roun cross-section shall comply with EN NOTE: Values o strength an stiness properties (see Table.4) are given or structural timber allocate to strength classes in EN 8. The establishment o strength classes an relate strength an stiness proiles is possible because, inepenently, nearly all sotwoos an harwoos commercially available exhibit a similar relationship between strength an stiness properties. Experimental ata shows that all important characteristic strength an stiness properties can be calculate rom either bening strength, moulus o elasticity (E) or ensity. However, urther research is require to establish the eect o timber quality on these relationships an to ecie whether accuracy coul be improve by moiying these retationships or ierent strength classes. Deciuous species (harwoos) have a ierent anatomical structure rom conierous species (sotwoos). They generally have higher ensities but not corresponingly higher strength an stiness properties. This is why EN 8 provies separate strength classes or conierous an eciuous species. Poplar, increasingly use or structural purposes, shows a ensity/strength relationship closer to that o conierous species an was thereore assigne to conierous strength classes. 14

14 Due to the relationships between strength, stiness an ensity a species /source/ grae combination can be assigne to a speciic strength class base on the characteristic values o bening strength, moulus o elasticity an ensity. Accoring to EN 8 a timber population can thus be assigne to a strength class provie - the timber has been visually or machine strength grae accoring to the speciications o EN 518 or EN 519; - the characteristic strength, stiness an ensity values have been etermine accoring to EN 84 Determination o characteristic values o mechanical properties an ensity ; - the characteristic values o bening strength, moulus o elasticity an ensity o the population are equal to or greater than the corresponing values o the relate strength class. The eect o member size on strength may be taen into account. Table. Values o e or timber an woo-base materials Material Stanar Service class 1 Soli timber EN ,60 0,80,00 Glue Laminate EN ,60 0,80,00 timber LVL EN 1474, EN ,60 0,80,00 Plywoo EN 66 Part 1 0,80 Part 0,80 1,00 Part 0,80 1,00,50 OSB EN 00 OSB/,5 OSB/, OSB/4 1,50,5 Particleboar EN 1 Part 4,5 Part 5,5,00 Part 6 1,50 Part 7 1,50,5 Fibreboar, har EN 6- HB.LA,5 HB.HLA1, HB.HLA,5,00 Fibreboar, meium EN 6- MBH.LA1, MBH.LA,00 MBH.HLS1,,00 4,00 MBH.HLS Fibreboar, MDF EN 6-5 MDF.LA,5 MDF.HLS,5,00 For rectangular soli timber with a characteristic timber ensity ρ 700 g/m, the reerence epth in bening or with (maximum cross-sectional imension) in tension is 150 mm. For epths in bening or withs in tension o soli timber less than 150 mm the characteristic values or m, an t,0, may be increase by the actor h, given by: 15

15 h 150 h min 1, 0, where h is the epth or bening members or with or tension members, in mm. (.1) For timber which is installe at or near its ibre saturation point, an which is liely to ry out uner loa, the values o e, given in Table., shoul be increase by 1,0. Finger joints shall comply with EN 85.. Glue laminate timber Glue laminate timber members shall comply with EN NOTE: Values o strength an stiness properties are given or glue laminate timber allocate to strength classes in EN Formulae or calculating the mechanical properties o glulam rom the lamination properties are given in Table.. The basic requirements or the laminations which are use in the ormulae o Table. are the tension characteristic strength an the mean moulus o elasticity. The ensity o the laminations is an inicative property. These properties shall be either the tabulate values given in EN 8 or erive accoring to the principles given in EN The requirements or glue line integrity are base on the testing o the glue line in a ull crosssectional specimen, cut rom a manuacture member. Depening on the service class, elamination tests (accoring to EN 91 Glue laminate timber - elamination test o glue lines ) or bloc shear tests (accoring to EN 9 Glue laminate timber - glue line shear test ) must be perorme. Table. Mechanical properties o glue laminate timber (in N/mm ) Property Bening m, g, Tension t,0, g, Compresion c,0,, 7 + 1,15 t,0, l, 5 + 0,8 t,0, l, t,90, g, 0, + 0,015 t,0, l, g c,90, g, 0,45 7, t,0, l, 0,5 0,7 t,0, l, Shear 0.8 v, g,,0,, Moulus o elasticity E 0, g, mean E 0, g,05 E 90, g, mean Shear moulus g, mean 0, t l 1,05 E0, l, mean 0,85 E0, l, mean 0,05 E0, l, mean E G 0,065 0, l, mean 16

16 Density ρ g, 1,10 ρ l, NOTE: For combine glue laminate timber the ormulae apply to the properties o the iniviual parts o the crosssection. It is assume that zones o ierent lamination graes amount to at least 1/6 o the beam epth or two laminations, whichever is the greater. The eect o member size on strength may be taen into account. For rectangular glue laminate timber, the reerence epth in bening or with in tension is 600 mm. For epths in bening or withs in tension o glue laminate timber less than 600 mm the characteristic values or m, an t,0, may be increase by the actor h,given by h 600 h min 1,1 0,1 where h is the epth or bening members or with or tensile members, in mm. (.) Large inger joints complying with the requirements o ENV 87 shall not be use or proucts to be installe in service class, where the irection o grain changes at the joint. The eect o member size on the tensile strength perpenicular to the grain shall be taen into account..4 Laminate veneer lumber (LVL) LVL structural members shall comply with EN For rectangular LVL with the grain o all veneers running essentially in one irection, the eect o member size on bening an tensile strength shall be taen into account. The reerence epth in bening is 00 mm. For epths in bening not equal to 00 mm the characteristic value or m, shoul be multiplie by the actor h,given by h 00 h min 1, s h is the epth o the member, in mm; s is the size eect exponent, see below. (.) The reerence length in tension is 000 mm. For lengths in tension not equal to 000 mm the characteristic value or t,0, shoul be multiplie by the actor l given by 17

17 l 000 l min 1,1 s / where l is the length, in mm. (.4) The size eect exponent s or LVL shall be taen as eclare in accorance with EN Large inger joints complying with the requirements o ENV 87 shall not be use or proucts to be installe in service class, where the irection o grain changes at the joint. For LVL with the grain o all veneers running essentially in one irection, the eect o member size on the tensile strength perpenicular to the grain shall be taen into account..5 Woo-base panels Woo-base panels shall comply with EN 1986 an LVL use as panels shall comply with EN The use o sotboars accoring to EN 6-4 shoul be restricte to win bracing an shoul be esigne by testing..6 Ahesives Ahesives or structural purposes shall prouce joints o such strength an urability that the integrity o the bon is maintaine in the assigne service class throughout the expecte lie o the structure. Ahesives which comply with Type I speciication as eine in EN 01 may be use in all service classes. Ahesives which comply with Type II speciication as eine in EN 01 shoul only be use in service classes 1 or an not uner prolonge exposure to temperatures in excess o 50 C..7 Metal asteners Metal asteners shall comply with EN 1459 an metal connectors shall comply with EN

18 Table.4 Strength classes an characteristic values accoring to EN 8 Conierous species an Poplar Deciuous species C14 C16 C18 C0 C C4 C7 C0 C5 C40 C45 C50 D0 D5 D40 D50 D60 D70 Strength properties in N/mm Bening m, Tension parallel to grain t,0, Tension perpenicular to grain t,90, 0,4 0,5 0,5 0,5 0,5 0,5 0,6 0,6 0,6 0,6 0,6 0,6 0,6 0,6 0,6 0,6 0,6 0,6 Compression parallel to grain c,0, Compression perpenicular to grain c,90,,0,,,,4,5,6,7,8,9,1, 8,0 8,4 8,8 9,7 10,5 1,5 Shear v, 1,7 1,8,0,,4,5,8,0,4,8,8,8,0,4,8 4,6 5, 6,0 Stiness properties in N/mm Mean value o moulus o elasticity parallel to grain 5% value o moulus o elasticity parallel to grain Mean value o moulus o elasticity pepenicular to grain E 0,mean , , E 0,05 4,7 5,4 6,0 6,4 6,7 7,4 7,7 8,0 8,7 9,4 10,0 10,7 8,0 8,7 9,4 11,8 14, 16,8 E 90, mean 0, 0,7 0,0 0, 0, 0,7 0,8 0,40 0,4 0,47 0,50 0,5 0,64 0,69 0,75 0,9 1,1 1, Mean value o shear moulus G mean 0,44 0,5 0,56 0,59 0,6 0,69 0,7 0,75 0,81 0,88 0,94 1,00 0,60 0,65 0,70 0,88 1,06 1,5 Density in g/m Density ρ Mean value o ensity ρ mean

19 4 Woo ahesives At present there is one establishe EN-stanar or classiication o structural woo ahesives, namely EN 01, Ahesives, phenolic an aminoplastic, or loa bearing timber structures: Classiication an perormance requirements. The corresponing test stanar is EN 0, Ahesives or loa-bearing timber structures - Test methos. The stanars apply to phenolic an aminoplastic ahesives only. These ahesives are classiie as: - type I-ahesives, which will stan ull outoor exposure, an temperatures above 50 C; - type II-ahesives, which may be use in heate an ventilate builings, an exterior protecte rom the weather. They will stan short exposure to the weather, but not prolonge exposure to weather or to temperatures above 50 C. Accoring to EC5 only ahesives complying with EN 01 may be approve at the moment. Current types o structural woo ahesives are liste below. Resorcinol ormalehye (RF) an Phenol-resorcinol ormalehye (PRF) ahesives RF s an PRF s are type I ahesives accoring to EN 01. They are use in laminate beams, ingerjointing o structural members, I-beams, box beams etc., both inoors an outoors. Phenol-ormalehye ahesives (PF), hot-setting Hot-setting PF's cannot be classiie accoring to EN 01. Phenol-ormalehye ahesives (PF), col-setting Col-setting PF's are classiie accoring to EN 01, but the current types are liely to be eliminate by the aci amage test given in EN 0-. Urea-ormalehye ahesives (UF) Only special col-setting UF s are suitable or structural purposes. In a ire they will ten to elaminate. UF s or structural purposes are classiie accoring to EN 01 as type IIahesives. Melamine-urea ormalehye ahesives (MUF) The col set ones are classiie accoring to EN 01. They are, however, less resistant than the resorcinols, an not suitable or marine purposes. However, MUF s are oten preerre or economic reasons, an because o their lighter colour. Casein ahesives Caseins are probably the olest type o structural ahesive an have been use or inustrial glulam prouction since beore 190. Caseins o not meet the requirements o EN 01. Epoxy ahesives Epoxy ahesives have very goo gapilling properties. Epoxies have very goo strength an urability properties, an the weather resistance or the best ones lies between MUF s an PRF s. Two-part polyurethanes These ahesives have goo strength an urability, but experience seems to inicate that they are not weather-resistant, at least not all o them. 0

20 5 Durability Timber is susceptible to biological attac whereas metal components may corroe. Uner ieal conitions timber structures can be in use or centuries without signiicant biological eterioration. However, i conitions are not ieal, many wiely use woo species nee a preservative treatment to be protecte rom the biological agencies responsible or timber egraation, mainly ungi an insects. 5.1 Resistance to biological organisms an corrosion Timber an woo-base materials shall either have aequate natural urability in accorance with EN 50- or the particular hazar class (eine in EN 5-1, EN 5- an EN 5-), or be given a preservative treatment selecte in accorance with EN 51-1 an EN 460. NOTE 1: Preservative treatment may aect the strength an stiness properties. NOTE : Rules or speciication o preservation treatments are given in EN 50- an EN 5. Metal asteners an other structural connections shall, where necessary, either be inherently corrosion-resistant or be protecte against corrosion. Examples o minimum corrosion protection or material speciications or ierent service classes are given in Table 5.1. Table 5.1 Examples o minimum speciications or material protection against corrosion or asteners (relate to ISO 081) Fastener Service Class b 1 Nails an screws with 4 mm None Fe/Zn 1c a Fe/Zn 5c a Bolts, owels, nails an screws with > 4 mm None None Fe/Zn 5c a Staples Fe/Zn 1c a Fe/Zn 1c a Stainless steel Punche metal plate asteners an steel plates up to mm thicness Steel plates rom mm up to 5 mm in thicness Fe/Zn 1c a Fe/Zn 1c a Stainless steel None Fe/Zn 1c a Fe/Zn 5c a Steel plates over 5 mm thicness None None Fe/Zn 5c a a I hot ip zinc coating is use, Fe/Zn 1c shoul be replace by Z75 an Fe/Zn 5c by Z50 in accorance with EN b For especially corrosive conitions consieration shoul be given to heavier hot ip coatings or stainless steel. 1

21 5. Biological attac The two main biological agencies responsible or timber egraation are ungi an insects although in speciic situations, timber can also be attace by marine borers. Fungal attac This occurs in timber which has a high moisture content, generally between 0 % an 0 %. Insect attac Insect attac is encourage by warm conitions which avour their evelopment an reprouction. 5. Classiication o hazar conitions The levels o exposure to moisture are eine ierently in EC5 an EN 5-I Durability o woo an woo-base proucts - Deinition o hazar (use) classes o biological attac - Part 1: General. EC5 provies or three service classes relating to the variation o timber perormance with moisture content, see Chapter. In EN 5-1, ive hazar (use) classes are eine with respect to the ris o biological attacs: Hazar (use) class 1, situation in which timber or woo-base prouct is uner cover, ully protecte rom the weather an not expose to wetting; Hazar (use) class, situation in which timber or woo-base prouct is uner cover an ully protecte rom the weather but where high environmental humiity can lea to occasional but not persistent wetting; Hazar (use) class, situation in which timber or woo-base prouct is not covere an not in contact with the groun. It is either continually expose to the weather or is protecte rom the weather but subject to requent wetting; Hazar (use) class 4, situation in which timber or woo-base prouct is in contact with the groun or resh water an thus is permanently expose to wetting; Hazar (use) class 5, situation in which timber or woo-base prouct is permanently expose to salt water. 5.4 Prevention o ungal attac It is possible to reuce the ris through careul construction etails, especially to reuce timber moisture content. 5.5 Prevention o insect attac Initially, the natural urability o the selecte timber species shoul be establishe with respect to the particular insect species to which it may be expose. It is also necessary to establish whether the particular insect is present in the region in which the timber to be use.

22 6 Ultimate limit states Timber structures are generally analyse using elastic structural analysis techniques the worl over. This is quite appropriate or the serviceability limit state (which is airly representative o the perormance o the structure rom year to year). Even the ultimate limit state (which moels the ailure o structural element uner an extreme loaing conition) can be reasonably moelle using an elastic analysis. 6.1 Design o cross-sections subjecte to stress in one principal irection This section eals with the esign o simple members in a single action Assumptions Section 6.1 applies to straight soli timber, glue laminate timber or woo-base structural proucts o constant cross-section, whose grain runs essentially parallel to the length o the member. The member is assume to be subjecte to stresses in the irection o only one o its principal axes (see Figure 6.1). Key: (1) irection o grain Figure 6.1 Member Axes 6.1. Tension parallel to the grain Tension members generally have a uniorm tension iel throughout the length o the member, an the entire cross section, which means that any corner at any point on the member has the potential to be a critical location. However a bening member uner uniormly istribute loaing will have a bening moment iagram that varies rom zero at each en to the maximum at the centre. The critical locations or tension are near to the centre, an only one hal o the beam cross section will have tension, so the volume o the member that is critical or laws is much less than that or tension members. The inhomogeneities an other eviations rom an ieal orthotropic material, which are typical or structural timber, are oten calle eects. As just mentione, these eects will cause a airly large strength reuction in tension parallel to the grain. For sotwoo (spruce, ir) typical average value are in the range o t,0 10 to 5 N/mm. In EC5 the characteristic strength values o soli timber are relate to a with in tension parallel to the grain o 150 mm. For withs in tension o soli timber less than I50 mm the characteristic values may be increase by a actor h. For glulam the reerence with is 600 mm an, analogously, or withs smaller than 600 mm a actor h shoul be applie.

23 For long boars uner uniaxial tension ue consieration shoul be taen both o the size eect (length eect) an o the lengthwise variation o the tensile strength. The ollowing expression shall be satisie: σ t,0, (6.1) t,0, where σ t,0, t,0, is the esign tensile stress along the grain; is the esign tensile strength along the grain Tension perpenicular to the grain The lowest strength or timber is in tension perpenicular to the grain. In timber members tensile stresses perpenicular to the grain shoul be avoie or ept as low as possible. The eect o member size shall be taen into account Compression parallel to the grain At the ultimate limit state, the compression member will have achieve its compressive capacity whether limite by material crushing (see Figure 6.) or bucling. In contrast to the brittle, explosive ailure o tension members, the compression ailure is quiet an graual. Bucling is quite silent as it is not associate with material ailure at all, an crushing is accompanie by a crunching or cracling soun. However, in spite o the silence o ailure, any structural ailure can lea to loss or at least partial loss o the structural system an place a ris on human lie. Both moes o ailure are just as serious as the more ramatic tensile an bening ailures. Figure 6. Failure mechanisms in compression The strength in compression parallel to the grain will be somewhat reuce by the growth eects to c,0 5 to 40 N/mm. The reuction in strength epens on the testing metho. I the specimen is compresse between two sti en plates, which are restraine rom rotation, a local ailure o some ibres will lea to stress reistribution over the rest o the cross section. This will result in a higher average stress than i the specimen ha been loae via a hinge enplate. 4

24 The ollowing expression shall be satisie: c,0, c,0, σ (6.) σ c,0, c,0, is the esign compressive stress along the grain; is the esign compressive strength along the grain. NOTE: Rules or the instability o members are given in Compression perpenicular to the grain Bearing capacity either over a support or uner a loa plate is a unction o the crushing strength o the woo ibre. Where the bearing capacity is exceee, local crushing occurs. This type o ailure is quite uctile, but in some cases, ibre amage in the region o a support may cause lexural ailure in that location. The bearing capacity is a complex unction o the bearing area. Where the bearing oes not completely cover the area o timber, testing has shown a consierable increase in bearing capacity. This is nown as an ege eect. Figure 6. shows bearing ailure uner heavily loae beams. The inluence o growth eects on the strength perpenicular to the grain is small. Figure 6. Bearing eects at supports an points o concentrate loa application The ollowing expression shall be satisie: σ (6.) c,90, c,90 c,90, σ c,90, c,90, c,90 is the esign compressive stress in the contact area perpenicular to the grain; is the esign compressive strength perpenicular to the grain; is a actor taing into account the loa coniguration, possibility o splitting an egree o compressive eormation. 5

25 The value o c,90 shoul be taen as 1,0, unless the member arrangements in the ollowing paragraphs apply. In these cases the higher value o c,90 speciie may be taen, up to a limiting value o c,90 4,0. NOTE: When a higher value o c,90 is use, an contact extens over the ull member with b, the resulting compressive eormation at the ultimate limit state will be approximately 10 % o the member epth. For a beam member resting on supports (see Figure 6.4), the actor c,90 shoul be calculate rom the ollowing expressions: When the istance rom the ege o a support to the en o a beam a, h/: l h c,90, l At internal supports: l h c,90, l l is the contact length in mm; h is member epth in mm. (6.4) (6.5) Figure 6.4 Beam on supports For a member with a epth h,5b where a concentrate orce with contact over the ull with b o the member is applie to one ace irectly over a continuous or iscrete support on the opposite ace, see Figure 6.5, the actor c,90 is given by: l l e c,90,8 50 l l e is the eective length o istribution, in mm; l is the contact length, see Figure 6.5, in mm. 0,5 (6.6) 6

26 Figure 6.5 Determination o eective lengths or a member with h/b,5, (a) an (b) continuous support, (c) iscrete supports The eective length o istribution l e shoul be etermine rom a stress ispersal line with a vertical inclination o 1: over the epth h, but curtaile by a istance o a/ rom any en, or a istance o l 1 /4 rom any ajacent compresse area, see Figure 6.5a an b. For the particular positions o orces below, the eective length is given by: - or loas ajacent to the en o the member, see Figure 6.5a h l e l + (6.7) - when the istance rom the ege o a concentrate loa to the en o the member a, h,see Figure 6.5b h l e l + (6.8) where h is the epth o the member or 40 mm, whichever is the largest. For members on iscrete supports, provie that a h an l 1 h, see Figure 6.5c, the eective length shoul be calculate as: h l e 0,5 l + l s + (6.9) where h is the epth o the member or 40 mm, whichever is the largest. 7

27 For a member with a epth h >,5b loae with a concentrate compressive orce on two opposite sies as shown in Figure 6.6b, or with a concentrate compressive orce on one sie an a continuous support on the other, see Figure 6.6a, the actor c,90 shoul be calculate accoring to expression (6.10), provie that the ollowing conitions are ulille: the applie compressive orce occurs over the ull member with b; the contact length l is less than the greater o h or 100 mm: c,90 l l e (6.10) l is the contact length accoring to Figure 6.6; l e is the eective length o istribution accoring to Figure 6.6 The eective length o istribution shoul not exten by more than l beyon either ege o the contact length. For members whose epth varies linearly over the support (e.g. bottom chors o trusses at the heel joint), the epth h shoul be taen as the member epth at the centreline o the support, an the eective length l e shoul be taen as equal to the contact length l. 8

28 Figure 6.6 Determination o eective lengths or a member with h/b >,5 on (a) a continuous support, (b) iscrete supports 9

29 6.1.6 Bening The most common use o a beam is to resist loas by bening about its major principal axis. However, the introuction o orces, which are not in the plane o bening, on the beam results in bi-axial bening (i.e. bening about both the major an minor principal axes). Aitionally, the introuction o axial loas in tension or compression results in a urther combine stress eect. For beams which are subjecte to bi-axial bening, the ollowing conitions both nee to be satisie: The ollowing expressions shall be satisie: σ m,y, m,z, + m 1 (6.11) m m,y, σ σ m,z, m,y, m,z, + 1 (6.1) m,y, σ m,z, σ m,y, an σ m,z, are the esign bening stresses about the principal axes as shown in m,y, an m,z, Figure 6.1; are the corresponing esign bening strengths. NOTE: The actor m maes allowance or re-istribution o stresses an the eect o inhomogeneities o the material in a cross-section. The value o the actor m shoul be taen as ollows: For soli timber, glue laminate timber an LVL: or rectangular sections: m 0,7 or other cross-sections: m 1,0 For other woo-base structural proucts, or all cross-sections: m 1,0. A chec shall also be mae o the instability conition (see 6.) Shear When bening is prouce by transverse loaing, shear stresses will be present accoring to the theory o elasticity. Shear stresses transverse to the beam axis will always be accompanie by equal shear stresses parallel to the beam axis. For shear with a stress component parallel to the grain, see Figure 6.7(a), as well as or shear with both stress components perpenicular to the grain, see Figure 6.7(b), the ollowing expression shall be satisie: τ (6.1) v, τ v, is the esign shear stress; is the esign shear strength or the actual conition. 0

30 NOTE: The shear strength or rolling shear is approximately equal to twice the tension strength perpenicular to grain. Figure 6.7(a) Member with a shear stress component parallel to the grain (b) Member with both stress components perpenicular to the grain (rolling shear) At supports, the contribution to the total shear orce o a concentrate loa F acting on the top sie o the beam an within a istance h or h e rom the ege o the support may be isregare (see Figure 6.8). For beams with a notch at the support this reuction in the shear orce applies only when the notch is on the opposite sie to the support. Figure 6.8 Conitions at a support, or which the concentrate orce F may be isregare in the calculation o the shear orce Torsion Torsional stresses are introuce when the applie loa tens to twist a member. This will occur when a beam supports a loa which is applie eccentric to the principal cross sectional axis. A transmission mast may be subjecte to an eccentric horizontal loa, resulting in a combination o shear an torsion. The ollowing expression shall be satisie: τ (6.14) tor, shape v, with shape 1, or a circular cross section h 1+0,15 min b,0 or a rectangular cross section (6.15) 1

31 τ tor, v, is the esign torsional stress; is the esign shear strength; shape is a actor epening on the shape o the cross-section; h b is the larger cross-sectional imension; is the smaller cross-sectional imension. 6. Design o cross-sections subjecte to combine stresses While the esign o many members is to resist a single action such as bening, tension or compression, there are many cases in which members are subjecte to two o these aitions simultaneously Assumptions Section 6. applies to straight soli timber, glue laminate timber or woo-base structural proucts o constant cross-section, whose grain runs essentially parallel to the length o the member. The member is assume to be subjecte to stresses rom combine actions or to stresses acting in two or three o its principal axes. 6.. Compression stresses at an angle to the grain Interaction o compressive stresses in two or more irections shall be taen into account. The compressive stresses at an angle α to the grain, (see Figure 6.9), shoul satisy the ollowing expression: c,0, σ c,α, c,0, sin α + cos α σ c,α, c,90 c,90 c,90, is the compressive stress at an angle α to the grain; is a actor given in taing into account the eect o any o stresses perpenicular to the grain. (6.16) Figure 6.9 Compressive stresses at an angle to the grain 6.. Combine bening an axial tension The ollowing expressions shall be satisie: σ σ σ t,0, m,y, m,z, + + m 1 (6.17) t,0, m,y, m,z,

32 σ σ σ t,0, m,y, m,z, + m + 1 (6.18) t,0, m,y, m,z, The values o m given in apply Combine bening an axial compression The ollowing expressions shall be satisie: σ σ σ c,0, m,y, m,z, + + m c,0, m,y, m,z, σ σ σ c,0, m,y, m,z, + m + c,0, m,y, m,z, 1 1 (6.19) (6.0) The values o m given in apply. NOTE: To chec the instability conition, a metho is given in Stability o members When a slener column is loae axially, there exists a tenency or it to elect sieways (see Figure 6.10). This type o instability is calle lexural bucling. The strength o slener members epens not only on the strength o the material but also on the stiness, in the case o timber columns mainly on the bening stiness. Thereore, apart rom the compression an bening strength, the moulus o elasticity is an important material property inluencing the loa-bearing capacity o slener columns. The aitional bening stresses cause by lateral elections are taen into account in a stability esign. When esigning beams, the prime concern is to provie aequate loa carrying capacity an stiness against bening about its major principal axis, usually in the vertical plane. This leas to a cross-sectional shape in which the stiness in the vertical plane is oten much greater than that in the horizontal plane.whenever a slener structural element is loae in its sti plane (axially in the case o the column) there is a tenency or it to ail by bucling in a more lexible plane (by electing sieways in the case o the column). The response o a slener simply supporte beam, subjecte to bening moments in the vertical plane; is terme lateral-torsional bucling as it involves both lateral election an twisting (see Figure 6.11). Figure 6.10 Two-hinge column bucling in compression

33 Figure 6.11 Lateral-torsional bucling o simply supporte beam 6..1 Assumptions The bening stresses ue to initial curvature, eccentricities an inuce election shall be taen into account, in aition to those ue to any lateral loa. Column stability an lateral torsional stability shall be veriie using the characteristic properties, e.g. E 0,05 The stability o columns subjecte to either compression or combine compression an bening shoul be veriie in accorance with 6... The lateral torsional stability o beams subjecte to either bening or combine bening an compression shoul be veriie in accorance with Columns subjecte to either compression or combine compression an bening The relative slenerness ratios shoul be taen as: λ rel,y an λ rel,z λ y π λ z π E E c,0, 0,05 c,0, 0,05 (6.1) (6.) λ y an λ rel,y are slenerness ratios corresponing to bening about the y-axis (election in the z-irection); λ z an λ rel,z are slenerness ratios corresponing to bening about the z-axis; E 0,05 is the ith percentile value o the moulus o elasticity parallel to the grain. Where both λ rel,z 0, an λ rel,y 0, the stresses shoul satisy the expressions (6.19) an (6.0) in

34 In all other cases the stresses, which will be increase ue to election, shoul satisy the ollowing expressions: σ σ σ c,0, m,y, m,z, (6.) m c,y c,0, m,y, m,z, σ σ σ c,0, m,y, m,z, (6.4) m c,z c,0, m,y, m,z, where the symbols are eine as ollows: λ c,y y y rel,y (6.5) λ c,z z z rel,z ( ( ) ) y c rel,y rel,y (6.6) 0,5 1 + β λ - 0, + λ (6.7) ( ( ) ) 0,5 1 + β λ - 0, + λ (6.8) z c rel,z rel,z β c is a actor or members within the straightness limits: 0, or soli timber βc (6.9) 0,1 or glue laminate timber an LVL m as given in Beams subjecte to either bening or combine bening an compression Lateral torsional stability shall be veriie both in the case where only a moment M y exists about the strong axis y an where a combination o moment M y an compressive orce N c exists. The relative slenerness or bening shoul be taen as: λ rel,m m, (6.0) σ m,crit where σ m,crit is the critical bening stress calculate accoring to the classical theory o stability, using 5-percentile stiness values. The critical bening stress shoul be taen as: M π y,crit σ m,crit W E 0,05 E I G I 0,05 z 0,05 tor l W y e y is the ith percentile value o moulus o elasticity parallel to grain; (6.1) 5

35 G 0,05 is the ith percentile value o shear moulus parallel to grain; I z is the secon moment o area about the wea axis z. I tor l e is the torsional moment o inertia; is the eective length o the beam, epening on the support conitions an the loa coniguration, acccoring to Table 6.1; W y is the section moulus about the strong axis y. For sotwoo with soli rectangular cross-section, σ m,crit shoul be taen as: 0,78b m,crit E 0,05 hl e σ b is the with o the beam; h is the epth o the beam. (6.) In the case where only a moment M y exists about the strong axis y, the stresses shoul satisy the ollowing expression: σ (6.) m, crit m, σ m, m, crit is the esign bening stress; is the esign bening strength; is a actor which taes into account the reuce bening strength ue to lateral bucling. Table 6.1 Eective length as a ratio o the span Beam type Loaing type l e/ l a Simply supporte Constant moment Uniormly istribute loa Concentrate orce at the mile o the span 1,0 0,9 0,8 Cantilever Uniormly istribute loa 0,5 Concentrate orce at the ree en 0,8 a The ratio between the eective length l e an the span l is vali or a beam with torsionally restraine supports an loae at the centre o gravity. I the loa is applie at the compression ege o the beam, l e shoul be increase by h an may be ecrease by 0,5h or a loa at the tension ege o the beam. For beams with an initial lateral eviation rom straightness within the limits crit may be etermine rom expression (6.4) 6

36 1 or λrel,m 0, 75 1,56-0,75λ or 0,75 < λ 1, 4 1 or 1, 4 < λ rel,m λrel,m crit rel,m rel,m (6.4) The actor crit may be taen as 1,0 or a beam where lateral isplacement o its compressive ege is prevente throughout its length an where torsional rotation is prevente at its supports. In the case where a combination o moment M y about the strong axis y an compressive orce N c exists, the stresses shoul satisy the ollowing expression: σ m, σ + c, crit m, c,z c,0, σ m, σ c, c,0, 1 is the esign bening stress; is the esign compressive stress; is the esign compressive strength parallel to grain; c,z is given by expression (6.6). (6.5) 6.4 Design o cross-sections in members with varying cross-section or curve shape Due to the range o sizes, lengths an shapes available, glulam is requently use or ierent beams. It is rare or sawn timber to be use as tapere or curve beams because o the iiculty obtaining large size cross section material an iiculties in bening it about its major axis to give a curve longituinal proile Assumptions The eects o combine axial orce an bening moment shall be taen into account. The relevant parts o 6. an 6. shoul be veriie. The stress at a cross-section rom an axial orce may be calculate rom N σ N (6.6) A σ N N A is the axial stress; is the axial orce; is the area o the cross-section. 7

37 6.4. Single tapere beams The inluence o the taper on the bening stresses parallel to the surace shall be taen into account. Key: (1) cross-section Figure 6.1 Single tapere beam The esign bening stresses, σ m,α, an σ m,0, (see Figure 6.1) may be taen as: σ 6 M σ (6.7) b h m, α, m,0, At the outermost ibre o the tapere ege, the stresses shoul satisy the ollowing expression: σ (6.8) m,α, m,α m, σ m,α, is the esign bening stress at an angle to grain; m, is the esign bening strength; m,α shoul be calculate as: For tensile stresses parallel to the tapere ege: m,α 1 m, m, 1+ tan α + tan α 0,75 v, t,90, For compressive stresses parallel to the tapere ege: m,α 1 m, m, 1+ tan α + tan α 1,5 v, c,90, 6.4. Double tapere, curve an pitche cambere beams This section applies only to glue laminate timber an LVL. The requirements o 6.4. apply to the parts o the beam which have a single taper. (6.9) (6.40) 8

38 In the apex zone (see Figure 6.1), the bening stresses shoul satisy the ollowing expression: σ m, r m, (6.41) where r taes into account the strength reuction ue to bening o the laminates uring prouction. NOTE: In curve an an pitche cambere beams the apex zone extens over the curve part o the beam. The apex bening stress shoul be calculate as ollows: 6 M σ l (6.4) ap, m, b hap with: hap hap hap 1 4 l r r r (6.4) 1 + 1,4 tan α + 5,4 tan α (6.44) 1 ap ap 0,5-8 tanα (6.45) ap 0,6 + 8, tan α - 7,8 tan α (6.46) ap ap 6 tan α (6.47) 4 ap r r + 0,5 h in ap M ap, is the esign moment at the apex; h ap is the epth o the beam at the apex, see Figure 6.1; b is the with o the beam; r in is the inner raius, see Figure 6.1; α ap is the angle o the taper in the mile o the apex zone, see Figure 6.1. (6.48) For ouble tapere beams r 1,0. For curve an pitche cambere beams r shoul be taen as: r t r r r + < t t where in 1 or 40 in in 0, 76 0, 001 or 40 r in is the inner raius, see Figure 6.1; t is the lamination thicness. (6.49) 9

39 Key: (1) Apex Zone NOTE: In curve an pitche cambere beams the apex zone extens over the curve parts o the beam. Figure 6.1 Double tapere (a), curve (b) an pitche cambere (c) beams with the ibre irection parallel to the lower ege o the beam In the apex zone the greatest tensile stress perpenicular to the grain, σ t,90,, shoul satisy the ollowing expression: σ t,90, is vol t,90, (6.50) 40

40 with 1,0 or soli timber 0, V or glue laminate timber an LVL with V all veneers parallel to the beam axis vol 0 is is vol t,90, V 0 V 1,4 or ouble tapere an curve beams 1,7 or pitche cambere beams (6.51) (6.5) is a actor which taes into account the eect o the stress istribution in the apex zone; is a volume actor; is the esign tensile strength perpenicular to the grain; is the reerence volume o 0,01m³; is the stresse volume o the apex zone, in m, (see Figure 6.1) an shoul not be taen greater than V b /, where V b is the total volume o the beam. For combine tension perpenicular to grain an shear the ollowing expression shall be satisie: τ v, τ v, t,90, + 1 (6.5) is σ vol t,90, is the esign shear stress; is the esign shear strength; σ t,90, is the esign tensile stress perpenicular to grain; is an vol are given in expressions (6.51) an (6.5). The greatest tensile stress perpenicular to the grain ue to the bening moment shoul be calculate as ollows: 6 M σ (6.54) t,90, ap, p b hap or, as an alternative to expression (6.54), as 6 M p σ ap, t,90, p 0,6 b h b (6.55) ap p b is the uniormly istribute loa acting on the top o the beam over the apex area; is the with o the beam; M ap, is the esign moment at apex resulting in tensile stresses parallel to the inner curve ege; 41

41 with: h + + r ap p ap hap r (6.56) 0, tanα (6.57) 0,5-1,5 tan α +,6 tan α (6.58) 6 ap ap,1 tan α - 4 tan α (6.59) 7 ap ap 6.5. Notche members It is not uncommon or the ens o beams to be notche at the bottom to increase clearance or to bring the top surace o a particular beam, level with other beams or gires. Notches usually create stress concentrations in the region o the re-entrant cornes Assumptions The eects o stress concentrations at the notch shall be taen into account in the strength veriication o members. The eect o stress concentrations may be isregare in the ollowing cases: tension or compression parallel to the grain; bening with tensile stresses at the notch i the taper is not steeper than 1:i 1:10, that is i 10, see Figure 6.14a; bening with compressive stresses at the notch, see Figure 6.14b. a) b) Figure 6.14 Bening at a notch: a) with tensile stresses at the notch, b) with compressive stresses at the notch 6.5. Beams with a notch at the support For beams with rectangular cross-sections an where grain runs essentially parallel to the length o the member, the shear stresses at the notche support shoul be calculate using the eective (reuce) epth h e (see Figure 6.15). It shoul be veriie that 1,5V τ (6.60) v v, b he where v is a reuction actor eine as ollows: 4

42 For beams notche at the opposite sie to the support (see Figure 6.15b) 1,0 (6.61) v For beams notche on the same sie as the support (see Figure 6.15a) v i h x min h 1 1,5 1,1 i n 1 + h x 1 α(1 - α) + 0,8 - α h α is the notch inclination (see Figure 6.15a); is the beam epth in mm; is the istance rom line o action o the support reaction to the corner o the notch; (6.6) α n h e h 4,5 or LVL 5 or soli timber 6,5 or glue laminate timber (6.6) Figure 6.15 En-notche beams 6.6 System strength When several equally space similar members, components or assemblies are laterally connecte by a continuous loa istribution system, the member strength properties may be multiplie by a system strength actor sys. 4

43 Provie the continuous loa-istribution system is capable o transering the loas rom one member to the neighbouring members, the actor sys shoul be 1,1. The strength veriication o the loa istribution system shoul be carrie out assuming the loas are o short-term uration. NOTE: For roo trusses with a maximum centre to centre istance o 1, m it may be assume that tiling battens, purlins or panels can transer the loa to the neighbouring trusses provie that these loa-istribution members are continuous over at least two spans, an any joints are staggere. For laminate timber ecs or loors the values o sys given in Figure 6.16 shoul be use. Key: 1 Naile or screwe laminations Laminations pre-stresse or glue together Figure 6.16 System strength actor sys or laminate ec plates o soli timber or glue laminate members 44

44 7 Serviceability limit states The overall perormance o structures shoul satisy two basic requirements. The irst is saety, usually expresse in terms o loa bearing capacity, an the secon is serviceability, which reers to the ability o the structural system an its elements to perorm satisactorily in normal use. 7.1 Joint slip For joints mae with owel-type asteners the slip moulus K ser per shear plane per astener uner service loa shoul be taen rom Table 7.1 with ρ m in g/m³ an or c in mm. For the einition o c, see 8.9. Table 7.1 Values o K ser or asteners an connectors in N/mm in timber-to-timber an woo-base panel-to-timber connections Fastener type Dowels Bolts with or without clearance a Screws Nails (with pre-rilling) K ser ρ m 1,5 / Nails (without pre-rilling) ρ m 1,5 0,8 /0 Staples ρ m 1,5 0,8 /80 Split-ring connectors type A accoring to EN 91 Shear-plate connectors type B accoring to EN 91 Toothe-plate connectors: ρ m c / Connectors types C1 to C9 accoring to EN 91 1,5ρ m c /4 Connectors type C10 an C11 accoring to EN 91 ρ m c / a The clearance shoul be ae separately to the eormation. I the mean ensities ρ m,1 an ρ m, o the two jointe woo-base members are ierent then ρ m in the above expressions shoul be taen as ρ m ρ m,1ρ m, (7.1) For steel-to-timber or concrete-to-timber connections, K ser shoul be base on ρ m or the timber member an may be multiplie by,0. 7. Limiting values or elections o beams The act that variable loas (such as impose loas on loors an snow loas on roos) oten ominate in timber structures means that the election will vary consierably uring the lietime o the structure. This has to be consiere in a rational serviceability esign The components o election resulting rom a combination o actions are shown in Figure 7.1, where the symbols are eine as ollows: w c is the precamber (i applie); 45

45 w inst is the instantaneous election; w creep is the creep election; w in is the inal election; w net,in is the net inal election. Figure 7.1 Components o election The net election below a straight line between the supports, w net,in, shoul be taen as: wnet,in winst + wcreep wc win wc (7.) NOTE: The recommene range o limiting values o elections or beams with span l is given in Table 7. epening upon the level o eormation eeme to be acceptable. Table 7. Examples o limiting values or elections o beams Beam on two supports Cantilevering beams w inst w net,in w in l/00 to l/500 l/50 to l/50 l/150 to l/00 l/150 to l/50 l/15 to l/175 l/75 to l/ Vibrations In general there are many loa-response cases where structural vibrations may constitute a state o reuce serviceability. The main concern, however, is with regar to human iscomort. People are in most cases the critical sensor o vibration. Among ierent ynamic actions, human activity an installe machinery are regare as the two most important interval sources o vibration in timber-rame builings. Human activity not only inclues ootall rom normal waling, but also chilren s jumping, etc. Two critical loa response cases are inally ientiie: - Human iscomort rom ootall-inuce vibrations. - Human iscomort rom machine-inuce vibrations. 46

46 7..1 Assumptions It shall be ensure that the actions which can be reasonably anticipate on a member, component or structure, o not cause vibrations that can impair the unction o the structure or cause unacceptable iscomort to the users. The vibration level shoul be estimate by measurements or by calculation taing into account the expecte stiness o the member, component or structure an the moal amping ratio. For loors, unless other values are proven to be more appropriate, a moal amping ratio o ζ 0,01 (i.e. 1 %) shoul be assume. 7.. Vibrations rom machinery Vibrations cause by rotating machinery an other operational equipment shall be limite or the unavourable combinations o permanent loa an variable loas that can be expecte. For loors, acceptable levels or continuous vibration shoul be taen rom Figure 5a in Appenix A o ISO 61- with a multiplying actor o 1,0. Resiential loors For resiential loors with a unamental requency less than 8 Hz ( 1 8Hz) a special investigation shoul be mae. For resiential loors with a unamental requency greater than 8 Hz ( 1 > 8 Hz) the ollowing requirements shoul be satisie: w a mm/n F (7.) an v ( 1-1) b ζ m/(ns²) (7.4) w v ζ is the maximum instantaneous vertical election cause by a vertical concentrate static orce F applie at any point on the loor, taing account o loa istribution; is the unit impulse velocity response, i.e. the maximum initial value o the vertical loor vibration velocity (in m/s) cause by an ieal unit impulse (1 Ns) applie at the point o the loor giving maximum response. Components above 40 Hz may be isregare; is the moal amping ratio. NOTE: The recommene range o limiting values o a an b an the recommene relationship between a an b is given in Figure

47 Key: 1 Better perormance Poorer perormance Figure 7. Recommene range o an relationship between a an b The calculations in shoul be mae uner the assumption that the loor is unloae, i.e., only the mass corresponing to the sel-weight o the loor an other permanent actions. For a rectangular loor with overall imensions l b, simply supporte along all our eges an with timber beams having a span l, the unamental requency 1 may approximately be calculate as π l ( EI) m l 1 m is the mass per unit area in g/m²; l is the loor span, in m; (EI) l (7.5) is the equivalent plate bening stiness o the loor about an axis perpenicular to the beam irection, in Nm²/m. For a rectangular loor with overall imensions b l, simply supporte along all our eges, the value v may, as an approximation, be taen as: v 4(0,4 + 0,6 n40 ) mbl + 00 v is the unit impulse velocity response, in m/(ns ); n 40 is the number o irst-orer moes with natural requencies up to 40 Hz; b is the loor with, in m; (7.6) 48

48 m is the mass, in g/m ; l is the loor span, in m. The value o n 40 may be calculate rom: n b ( EI ) - 1 l 1 l ( EI ) b 0,5 (7.7) where (EI) b is the equivalent plate bening stiness, in Nm /m, o the loor about an axis parallel to the beams, where (EI) b < (EI) l. 49

49 8 Connections with metal asteners For timber structures, the serviceability an the urability o the structure epen mainly on the esign o the joints between the elements. For commonly use connections, a istinction is mae between carpentry joints an mechanical joints that can be mae rom several types o astener. For a given structure, the selection o asteners is not only controlle by the loaing an the loa-carrying capacity conitions. It inclues some construction consierations such as aesthetics, the cost-eiciency o the structure an the abrication process. The erection metho an the preerence o the esigner or the architect are also involve. It is impossible to speciy a set o rules rom which the best connection can be esigne or any structure. The main iea is that the simpler the joint an the ewer the asteners, the better is the structural result. The traitional mechanical asteners are ivie into two groups epening on how they transer the orces between the connecte members. The main group correspons to the owel type asteners. Here, the loa transer involves both the bening behaviour o the owel an the bearing an shear stresses in the timber along the shan o the owel. Staples, nails, screws, bolts an owels belong to this group. The secon type inclues asteners such as split-rings, shear-plates, an punche metal plates in which the loa transmission is primarily achieve by a large bearing area at the surace o the members. The loa transmission is primarily achieve by a large bearing area at the surace o the members. This hanboo eals only with the owel type asteners. Figure 8.1 Metal asteners a) nails, b) owel, c) bolt, ) srews, e) split ring connector, ) toothe-plate connector g) punche metal plate astener 50

50 8.1 Basic assumptions There is a huge variety o conigurations an esign loaings o connections Fastener requirements Unless rules are given in this chapter, the characteristic loa-carrying capacity, an the stiness o the connections shall be etermine rom tests accoring to EN 1075, EN 180, EN 181, EN 6891 an EN I the relevant stanars escribe tension an compression tests, the tests or the etermination o the characteristic loa-carrying capacity shall be perorme in tension Multiple astener connections The arrangement an sizes o the asteners in a connection, an the astener spacings, ege an en istances shall be chosen so that the expecte strength an stiness can be obtaine. It shall be taen into account that the loa-carrying capacity o a multiple astener connection, consisting o asteners o the same type an imension, may be lower than the summation o the iniviual loa-carrying capacities or each astener. When a connection comprises ierent types o asteners, or when the stiness o the connections in respective shear planes o a multiple shear plane connection is ierent, their compatibility shoul be veriie. For one row o asteners parallel to the grain irection, the eective characteristic loacarrying capacity parallel to the row, F v,e,r, shoul be taen as: F n F v,e,r e v,r F v,e,r is the eective characteristic loa-carrying capacity o one row o asteners parallel to the grain; n e F v,r is the eective number o asteners in line parallel to the grain; is the characteristic loa-carrying capacity o each astener parallel to the grain. NOTE: Values o n e or rows parallel to grain are given in an For a orce acting at an angle to the irection o the row, it shoul be veriie that the orce component parallel to the row is less than or equal to the loa-carrying capacity calculate accoring to expression (8.1) Multiple shear plane connections In multiple shear plane connections the resistance o each shear plane shoul be etermine by assuming that each shear plane is part o a series o three-member connections. To be able to combine the resistance rom iniviual shear planes in a multiple shear plane connection, the governing ailure moe o the asteners in the respective shear planes shoul be compatible with each other an shoul not consist o a combination o ailure moes (a), (b), (g) an (h) rom Figure 8. or moes (c), () an (j/l) rom Figure 8. with the other ailure moes. (8.1) 51

51 8.1.4 Connection orces at an angle to the grain When a orce in a connection acts at an angle to the grain, (see Figure 8.1), the possibility o splitting cause by the tension orce component F E sin α, perpenicular to the grain, shall be taen into account. To tae account o the possibility o splitting cause by the tension orce component, F E sin α, perpenicular to the grain, the ollowing shall be satisie: F v,e with F v,e F 90,R F (8.) 90,R max F F v,e,1 v,e, is the esign splitting capacity, calculate rom the characteristic splitting capacity F 90,R accoring to..; F v,e,1, F v,e, are the esign shear orces on either sie o the connection (see Figure 8.1). For sotwoos, the characteristic splitting capacity or the arrangement shown in Figure 8.1 shoul be taen as: he F90,R 14b w (8.4) he 1 h 0,5 wpl max 100 or punche metal plate asteners w 1 1 or all other asteners an: F 90,R is the characteristic splitting capacity, in N; w h e h b w pl is a moiication actor; is the loae ege istance to the centre o the most istant astener or to the ege o the punche metal plate astener, in mm; is the timber member height, in mm; is the member thicness, in mm; is the with o the punche metal plate astener parallel to the grain, in mm. (8.) (8.5) 5

52 Figure 8.1 Incline orce transmitte by a connection Alternating connection orces The characteristic loa-carrying capacity o a connection shall be reuce i the connection is subject to alternating internal orces ue to long-term or meium-term actions. The eect on connection strength o long-term or meium-term actions alternating between a tensile esign orce F t,e an a compressive esign orce F c,e shoul be taen into account by esigning the connection or (F t,e + 0,5F c,e ) an (F c,e + 0,5F t,e ). 8. Lateral loa-carrying capacity o metal owel-type asteners The ailure o laterally loae asteners inclue both crushing o the timber an bening o the astener Asumptions For the etermination o the characteristic loa-carrying capacity o connections with metal owel-type asteners the contributions o the yiel strength, the embement strength, an the withrawal strength o the astener shall be consiere. 8.. Timber-to-timber an panel-to-timber connections The characteristic loa-carrying capacity or nails, staples, bolts, owels an screws per shear plane per astener, shoul be taen as the minimum value oun rom the ollowing expressions: For asteners in single shear F v,r h,1,t1 (a) h,,t (b) h,1,t1 t t t t F ax,r β β 1 β β (c) 1 β t1 t1 t1 t t 4 β ( + β ) M y,r Fax,R β + β + β + () + β h,1, t1 4 h,1,t 4 β (1 + β ) M y,r Fax,R 1,05 β (1 + β ) + β + (e) 1+ β h,1, t 4 β Fax,R 1,15 M y,r h,1, + () 1+ β 4 min 1,05 h,1, 1 (1 ) (8.6) 5

53 For asteners in ouble shear: F h,1,t1 0,5 h,,t t 4 β ( + β ) M F min 1, 05 β (1 + β ) + β β Fax,R 1,15 M y,r h,1, + 1+ β 4 h,1, 1 y,r v,r β h,1, t1 with β F v,r h,, h,1, is the characteristic loa-carrying capacity per shear plane per astener; t i is the timber or boar thicness or penetration epth, with i either 1 or, see also 8. to 8.7 ; h,i, is the characteristic embement strength in timber member i; is the astener iameter; M y,r is the characteristic astener yiel moment; β F ax,r is the ratio between the embement strength o the members; is the characteristic axial withrawal capacity o the astener. NOTE: Plasticity o joints can be assure when relatively slener asteners are use. In that case, ailure moes () an () are governing. In the expressions (8.6) an (8.7), the irst term on the right han sie is the loa-carrying capacity accoring to the Johansen yiel theory, whilst the secon term F ax,r /4 is the contribution rom the rope eect. The contribution to the loa-carrying capacity ue to the rope eect shoul be limite to ollowing percentages o the Johansen part: Roun nails 15 % Square nails 5 % Other nails 50 % Screws 100% Bolts 5 % Dowels 0 % I F ax,r is not nown then the contribution rom the rope eect shoul be taen as zero. For single shear asteners the characteristic withrawal capacity, F ax,r, is taen as the lower o the capacities in the two members. The ierent moes o ailure are illustrate in Figure 8.. For the withrawal capacity, F ax,r, o bolts the resistance provie by the washers may be taen into account, see ax,r (g) (h) (j) () (8.7) (8.8) 54

54 I no esign rules are given below, the characteristic embement strength h, shoul be etermine accoring to EN 8 an EN I no esign rules are given below, the characteristic yiel moment M y, shoul be etermine accoring to EN 409 an EN Key: (1) Single shear () Double shear NOTE: The letters correspon to the reerences o the expressions (8.6) an (8.7). Figure 8. Failure moes or timber an panel connections. 8.. Steel-to-timber connections The characteristic loa-carrying capacity o a steel-to-timber connection epens on the thicness o the steel plates. Steel plates o thicness less than or equal to 0,5 are classiie as thin plates an steel plates o thicness greater than or equal to with the tolerance on hole iameters being less than 0,1 are classiie as thic plates. The characteristic loa-carrying capacity o connections with steel plate thicness between a thin an a thic plate shoul be calculate by linear interpolation between the limiting thin an thic plate values. The strength o the steel plate shall be chece. The characteristic loa-carrying capacity or nails, bolts, owels an screws per shear plane per astener shoul be taen as the minimum value oun rom the ollowing expressions: For a thin steel plate in single shear: 55

55 F v,r 0,4 t h, 1 min F 1,15 ax,r M y,r h, + 4 For a thic steel plate in single shear: (a) (b) (8.9) 4M y,r F h, t h, t1 4 min F, ax,r + 4 h, t1 Fv,R M y,r h, ax,r (c) () (e) (8.10) For a steel plate o any thicness as the central member o a ouble shear connection: h,1, t1 4M y,r F Fv,R min h,1, t h,1, t1 4 Fax,R, M y,r h,1, + 4 For thin steel plates as the outer members o a ouble shear connection: F v,r 0,5 t h,, min F 1,15 ax,r M y,r h,, + 4 For thic steel plates as the outer members o a ouble shear connection: F v,r F v,r h, t 1 t (j) () 0, 5 h,, t (l) min F, ax,r M y,r h,, + (m) 4 is the characteristic loa-carrying capacity per shear plane per astener; ax,r is the characteristic embement strength in the timber member; is the smaller o the thicness o the timber sie member or the penetration epth; is the thicness o the timber mile member; is the astener iameter; M y,r is the characteristic astener yiel moment; F ax,r is the characteristic withrawal capacity o the astener. NOTE 1: The ierent ailure moes are illustrate in Figure 8.. () (g) (h) (8.11) (8.1) (8.1) 56

56 Figure 8. Failure moes or steel-to-timber connections For the limitation o the rope eect F ax,r 8.. applies. It shall be taen into account that the loa-carrying capacity o steel-to-timber connections with a loae en may be reuce by ailure along the perimeter o the astener group. 8. Naile connections Nails are the most commonly use asteners in timber construction Laterally loae nails The ailure o laterally loae nails inclue both crushing o the timber an bening o the nail Asumptions The symbols or the thicnesses in single an ouble shear connections (see Figure 8.4) are eine as ollows: t 1 is: the heasie thicness in a single shear connection; the minimum o the hea sie timber thicness an the pointsie penetration in a ouble shear connection; t is: the pointsie penetration in a single shear connection; the central member thicness in a ouble shear connection. Timber shoul be pre-rille when: the characteristic ensity o the timber is greater than 500 g/m ; the iameter o the nail excees 8 mm. For square an groove nails, the nail iameter shoul be taen as the sie imension. For smooth nails prouce rom wire with a minimum tensile strength o 600 N/mm, the ollowing characteristic values or yiel moment shoul be use: M 0, 45 or square nails,6 0, u or roun nails y,r,6 u M y,r is the characteristic value or the yiel moment, in Nmm; is the nail iameter as eine in EN 1459, in mm; (8.14) 57

57 u is the tensile strength o the wire, in N/mm. For nails with iameters up to 8 mm, the ollowing characteristic embement strengths in timber an LVL apply: without prerille holes -0, ρ (8.15) h, 0, 08 N/mm with prerille holes ρ ρ (8.16) h, 0,08 (1-0,01 ) N/mm is the characteristic timber ensity, in g/m³; is the nail iameter, in mm. Figure 8.4 Deinitions o t 1 an t (a) single shear connection, (b) ouble shear connection For nails with iameters greater than 8 mm the characteristic embement strength values or bolts accoring to apply. In a three-member connection, nails may overlap in the central member provie (t - t ) is greater than 4 (see Figure 8.5). Figure 8.5 Overlapping nails 58

58 For one row o n nails parallel to the grain, unless the nails o that row are staggere perpenicular to grain by at least 1 (see Figure 8.6), the loa-carrying capacity parallel to the grain (see 8.1.) shoul be calculate using the eective number o asteners n e, n e n e n n e is the eective number o nails in the row; is the number o nails in a row; e is given in Table 8.1. Table 8.1 Values o e Spacing a e Not Prerille prerille a ,0 1,0 a ,85 0,85 a 1 7 0,7 0,7 a 1 4-0,5 a For intermeiate spacings, linear interpolation o e is permitte (8.17) Key: 1 Nail Grain irection Figure 8.6 Nails in a row parallel to grain staggere perpenicular to grain by There shoul be at least two nails in a connection Naile timber-to-timber connections For smooth nails the pointsie penetration length shoul be at least 8. For nails other than smooth nails, as eine in EN 1459, the pointsie penetration length shoul be at least 6. Smooth nails in en grain shoul not be consiere capable o transmitting lateral orces. As an alternative to 8..1., or nails in en grain the ollowing rules apply: In seconary structures smooth nails may be use. The esign values o the loa-carrying capacity shoul be taen as 1/ o the values or nails installe at right angles to the grain; Nails other than smooth nails, as eine in EN 1459, may be use in structures other than seconary structures. The esign values o the loa-carrying capacity shoul be taen as 1/ 59

59 o the values or smooth nails o equivalent iameter installe at right angles to the grain, provie that: the nails are only laterally loae; there are at least three nails per connection; the pointsie penetration is at least 10; the connection is not expose to service class conitions; the prescribe spacings an ege istances given in Table 8. are satisie. Note: An example o a seconary structure is a ascia boar naile to raters. Minimum spacings an ege an en istances are given in Table 8., where (see Figure 8.7): a 1 a a,c a,t a 4,c a 4,t α is the spacing o nails within one row parallel to grain; is the spacing o rows o nails perpenicular to grain; is the istance between nail an unloae en; is the istance between nail an loae en; is the istance between nail an unloae ege; is the istance between nail an loae ege; is the angle between the orce an the grain irection. 60

60 Table 8. Minimum spacings an ege an en istances or nails Spacing or istance (see Figure 8.7) Spacing a 1 (parallel to grain) Spacing a (perpenicular to grain) Distance a,t (loae en) Distance a,c (unloae en) Distance a 4,t (loae ege) Distance a 4,c (unloae ege) Angle α 0 α 60 < 5 mm: (5+5 cosα ) 5 mm: Minimum spacing or en/ege istance without prerille holes ρ 40g/m 40 g/m <ρ 500 g/m (5+7 cos α ) (7+8 cos α ) with prerille holes (4+ cos α ) 0 α (+ sin α ) -90 α 90 (10+5 cos α) ( cos α) (7+ 5cos α) 90 α α 180 < 5 mm: (5+ sin α) 180 α 60 5 mm: (5+5 sin α) < 5 mm: (7+ sin α) 5 mm: (7 + 5 sin α) < 5 mm: ( + sin α) 5 mm: ( + 4 sin α) 5 7 Timber shoul be pre-rille when the thicness o the timber members is smaller than 7 t max ρ ( 1 0 ) 400 t is the minimum thicness o timber member to avoi pre-rilling, in mm; ρ is the characteristic timber ensity in g/m³; is the nail iameter, in mm. (8.18) Timber o species especially sensitive to splitting shoul be pre-rille when the thicness o the timber members is smaller than 14 t max ρ ( 1 0 ) 00 Expression (8.19) may be replace by expression (8.18) or ege istances given by: a 4 10 or ρ 40 g/m a 4 14 or 40 g/m ρ 500 g/ m. (8.19) 61

61 Note: Examples o species sensitive to splitting are ir (abies alba), Douglas ir (pseuotsuga menziesii) an spruce (picea abies).. Key: (1) Loae en () Unloae en () Loae ege (4) Unloae ege 1 Fastener Grain irection Figure 8.7 Spacings an en an ege istances (a) Spacing parallel to grain in a row an perpenicular to grain between rows, (b) Ege an en istances Naile panel-to-timber connections Minimum nail spacings or all naile panel-to-timber connections are those given in Table 8., multiplie by a actor o 0,85. The en/ege istances or nails remain unchange unless otherwise state below. Minimum ege an en istances in plywoo members shoul be taen as or an unloae ege (or en) an ( + 4 sin α) or a loae ege (or en), where α is the angle between the irection o the loa an the loae ege (or en). For nails with a hea iameter o at least, the characteristic embement strengths are as ollows: 6

62 or plywoo: h, 0,11ρ 0, h, is the characteristic embement strength, in N/mm ; ρ is the characteristic plywoo ensity in g/m³; is the nail iameter, in mm; or harboar in accorance with EN 6-: t (8.0) 0, 0,6 h, 0 (8.1) h, is the characteristic embement strength, in N/mm ; t is the nail iameter, in mm; is the panel thicness, in mm. or particleboar an OSB: t h, 65 0,7 0,1 h, is the characteristic embement strength, in N/mm ; t is the nail iameter, in mm; is the panel thicness, in mm. (8.) Naile steel-to-timber connections The minimum ege an en istances or nails given in Table 8. apply. Minimum nail spacings are those given in Table 8., multiplie by a actor o 0, Axially loae nails Smooth nails shall not be use to resist permanent or long-term axial loaing. For threae nails, only the threae part shoul be consiere capable o transmitting axial loa. Nails in en grain shoul be consiere incapable o transmitting axial loa. The characteristic withrawal capacity o nails, F ax,r, or nailing perpenicular to the grain (Figure 8.8 (a) an or slant nailing (Figure 8.8 (b)), shoul be taen as the smaller o the values oun rom the ollowing expressions: For nails other than smooth nails, as eine in EN 1459: F ax, t pen ax,r hea, h (a) (b) (8.) 6

63 For smooth nails: F ax, t pen ax,r ax, t + hea, h ax, hea, (a) (b) is the characteristic pointsie withrawal strength; is the characteristic heasie pull-through strength; is the nail iameter accoring to ; t pen t h is the pointsie penetration length or the length o the threae part in the pointsie member; is the thicness o the heasie member; is the nail hea iameter. (8.4) The characteristic strengths ax, an hea, shoul be etermine by tests in accorance with EN 18, EN 18 an EN 1458 unless speciie in the ollowing. For smooth nails with a pointsie penetration o at least 1, the characteristic values o the withrawal an pull-through strengths shoul be oun rom the ollowing expressions: ax, 0 10 ρ 6 (8.5) hea, ρ (8.6) 6 ρ is the characteristic timber ensity in g/m³; For smooth nails, the pointsie penetration t pen shoul be at least 8. For nails with a pointsie penetration smaller than 1 the withrawal capacity shoul be multiplie by (t pen /4 ). For threae nails, the pointsie penetration shoul be at least 6. For nails with a pointsie penetration smaller than 8 the withrawal capacity shoul be multiplie by (t pen / ). For structural timber which is installe at or near ibre saturation point, an which is liely to ry out uner loa, the values o ax, an hea, shoul be multiplie by /. The spacings, en an ege istances or laterally loae nails apply to axially loae nails. For slant nailing the istance to the loae ege shoul be at least 10 (see Figure 8.8 (b)). There shoul be at least two slant nails in a connection. 64

64 Figure 8.8 (a) Nailing perpenicular to grain an (b) slant nailing 8.. Combine laterally an axially loae nails For connections subjecte to a combination o axial loa (F ax,e )an lateral loa (F v,e )the ollowing expressions shoul be satisie: or smooth nails: F F ax,e ax,r F + F v,e v,r 1 or nails other than smooth nails, as eine in EN 1459: F ax,e F v,e + F ax,r F v,r 1 (8.7) (8.8) F ax,r an F v,r are the esign loa-carrying capacities o the connection loae with axial loa or lateral loa respectively. 8.4 Staple connections The rules given in 8., except o expressions (8.15), (8.16) an (8.19) apply or roun or nearly roun or rectangular staples with bevelle or symmetrical pointe legs. For staples with rectangular cross-sections the iameter shoul be taen as the square root o the prouct o both imensions. The with b o the staple crown shoul be at least 6, an the pointsie penetration length t shoul be at least 14, see Figure 8.9. There shoul be at least two staples in a connection. The lateral esign loa-carrying capacity per staple per shear plane shoul be consiere as equivalent to that o two nails with the staple iameter, provie that the angle between the crown an the irection o the grain o the timber uner the crown is greater than 0, see Figure I the angle between the crown an the irection o the grain uner the crown is equal to or less than 0, then the lateral esign loa-carrying capacity shoul be multiplie by a actor o 0,7. 65

65 For staples prouce rom wire with a minimum tensile strength o 800 N/mm², the ollowing characteristic yiel moment per leg shoul be use: M,6 y,r 40 (8.9) M y,r is the characteristic yiel moment, in Nmm; is the staple leg iameter, in mm. For a row o n staples parallel to the grain, the loa-carrying capacity in that irection shoul be calculate using the eective number o asteners n e accoring to expression (8.17). Minimum staple spacings, ege an en istances are given in Table 8., an illustrate in Figure 8.10 where Θ is the angle between the staple crown an the grain irection. Key: (1) staple centre Figure 8.9 Staple imensions Figure 8.10 Deinition o spacing or staples 66

66 Table 8. Minimum spacings an ege an en istances or staples Spacing an ege/en istances (see Figure 8.7) a 1 (parallel to grain) or Θ 0 or Θ<0 Angle Minimum spacing or ege/en istance 0 α 60 ( cos α ) ( cos α ) a (perpenicular to grain) 0 α a,t (loae en) -90 α 90 ( cos α ) a,c (unloae en) 90 α a 4,t (loae ege) 0 α 180 ( sin α ) a 4,c (unloae ege) 180 α Bolte connections Bolts are installe into pre-rille clearance holes in the timber Laterally loae bolts The ailure o laterally loae bolts inclue both crushing o the timber an bening o the bolt General an bolte timber-to-timber connections For bolts the ollowing characteristic value or the yiel moment shoul be use: 0,,6 M y,r u, (8.0) M y,r is the characteristic value or the yiel moment, in Nmm; u, is the characteristic tensile strength, in N/mm²; is the bolt iameter, in mm. For bolts up to 0 mm iameter, the ollowing characteristic embement strength values in timber an LVL shoul be use, at an angle α to the grain: h,α, h,0, 90 sin α + cos α (8.1) h,0, 0,08 (1-0,01 ) ρ (8.) 90 an: 1, 5 + 0, 015 or sotwoos 1, 0 + 0, 015 or LVL 0, , 015 or harwoos h,0, is the characteristc embement strength parallel to grain, in N/mm ; (8.) 67

67 ρ α is the characteristic timber ensity, in g/m³; is the angle o the loa to the grain; is the bolt iameter, in mm. Minimum spacings an ege an en istances shoul be taen rom Table 8.4, with symbols illustrate in Figure 8.7. Table 8.4 Minimum values o spacing an ege an en istances or bolts Spacing an en/ege istances (see Figure 8.7) Angle Minimum spacing or istance a 1 (parallel to grain) 0 α 60 (4 + cos α ) a (perpenicular to grain) 0 α 60 4 a,t (loae en) -90 α 90 max (7 ; 80 mm) a,c (unloae en) 90 α < α < α 70 max [(1 + 6 sin α) ; 4] 4 max [(1 + 6 sin α) ; 4] a 4,t (loae ege) 0 α 180 max [( + sin α) ; ] a 4,c (unloae ege) 180 α 60 For one row o n bolts parallel to the grain irection, the loa-carrying capacity parallel to grain, see 8.1.(4), shoul be calculate using the eective number o bolts n e n n min n a 1 e 0,9 4 1 a 1 is the spacing between bolts in the grain irection; is the bolt iameter n is the number o bolts in the row. (8.4) For loas perpenicular to grain, the eective number o asteners shoul be taen as n n (8.5) e For angles 0 < α < 90 between loa an grain irection, n e may be etermine by linear interpolation between expressions (8.4) an (8.5). Requirements or minimum washer imensions an thicness in relation to bolt iameter are given in Bolte panel-to-timber connections For plywoo the ollowing embement strength, in N/mm, shoul be use at all angles to the ace grain: 68

68 h, 0,11 (1-0,01 ) ρ (8.6) ρ is the characteristic plywoo ensity, in g/m³; is the bolt iameter, in mm. For particleboar an OSB the ollowing embement strength value, in N/mm, shoul be use at all angles to the ace grain: t h, 50 0,6 0, is the bolt iameter, in mm; t is the panel thicness, in mm. (8.7) Bolte steel-to-timber connections The rules given in 8.. apply Axially loae bolts The axial loa-bearing capacity an withrawal capacity o a bolt shoul be taen as the lower value o: the bolt tensile capacity; the loa-bearing capacity o either the washer or (or steel-to-timber connections) the steel plate. The bearing capacity o a washer shoul be calculate assuming a characteristic compressive strength on the contact area o,0 c,90,. The bearing capacity per bolt o a steel plate shoul not excee that o a circular washer with a iameter which is the minimum o: 1t, where t is the plate thicness; 4, where is the bolt iameter. 8.6 Dowelle connections The rules given in except minimum spacing an ege an en istances apply. The owel iameter shoul be greater than 6 mm an less than 0 mm. Minimum spacing an ege an en istances are given in Table 8.5, with symbols illustrate in Figure

69 Table 8.5 Minimum spacings an ege an en istances or owels Spacing an ege/en istances (see Figure 8.7) Angle Minimum spacing or ege/en istance a 1 (parallel to grain) 0 α 60 ( + cos α ) a (perpenicular to grain) 0 α 60 a,t (loae en) -90 α 90 0 max (7 ; 80 mm) a,c (unloae en) 90 0 α < α < α 70 max(a,t sin α ) ; ) max(a,t sin α ) ; ) a 4,t (loae ege) 0 α 180 max( + sin α) ; ) a 4,c (unloae ege) 180 α 60 Requirements or owel hole tolerances are given in Screwe connections Screws are installe into a rille hole, by turning the screw an allowing the lutes on the threa o the screw to raw it in Laterally loae screws The eect o the threae part o the screw shall be taen into account in etermining the loa-carrying capacity, by using an eective iameter e For smooth shan screws, where the outer threa iameter is equal to the shan iameter, the rules given in 8. apply, provie that: The eective iameter e is taen as the smooth shan iameter; The smooth shan penetrates into the member containing the point o the screw by not less than 4. Where the conitions in are not satisie, the screw loa-carrying capacity shoul be calculate using an eective iameter e taen as 1,1 times the threa root iameter. For smooth shan screws with a iameter > 6 mm, the rules in apply. For smooth shan screws with a iameter o 6 mm or less, the rules o 8..1 apply. Requirements or structural etailing an control o screwe joints are given in Axially loae screws The ollowing ailure moes shoul be veriie when assessing the loa-carrying capacity o connections with axially loae screws: the withrawal capacity o the threae part o the screw; or screws use in combination with steel plates, the tear-o capacity o the screw hea shoul be greater than the tensile strength o the screw; the pull-through strength o the screw hea; 70

70 the tension strength o the screw; or screws use in conjunction with steel plates, ailure along the circumerence o a group o screws (bloc shear or plug shear); Minimum spacing an ege istances or axially loae screws shoul be taen rom Table 8.6. Table 8.6 Minimum spacings an ege istances or axially loae screws Screws riven At right angle to the grain Minimum spacing 4 Minimum ege istance In en grain 4,5 The minimum pointsie penetration length o the threae part shoul be 6. The characteristic withrawal capacity o connections with axially loae screws shoul be taen as: F n ( π l ) (8.8) 0,8 ax,α,r e e ax,α, F ax,α,r is the characteristic withrawal capacity o the connection at an angle α to the grain; n e l e ax,α, is the eective number o screws; is the outer iameter measure on the threae part; is the pointsie penetration length o the threae part minus one screw iameter; is the characteristic withrawal strength at an angle α to the grain. 4 The characteristic withrawal strength at an angle α to the grain shoul be taen as: sin α + 1,5cos α ax, ax,α, with: ax, ax,α, ax,,6 10 ρ 1,5 is the characteristic withrawal strength at an angle α to the grain; is the characteristic withrawal strength perpenicular to the grain; ρ is the characteristic ensity, in g/m. (8.9) (8.40) NOTE: Failure moes in the steel or in the timber aroun the screw are brittle, i.e. with small ultimate eormation an thereore have a limite possibility or stress reistribution. 71

71 The pull-through capacity o the hea shall be etermine by tests, in accorance with EN 18. For a connection with a group o screws loae by a orce component parallel to the shan, the eective number o screws is given by: ne n 0,9 n e is the eective number o screws; n is the number o screws acting together in a connection. (8.41) 8.7. Combine laterally an axially loae screws For screwe connections subjecte to a combination o axial loa an lateral loa, expression (8.8) shoul be satisie. 7

72 9 Components 9.1 Glue thin-webbe beams I a linear variation o strain over the epth o the beam is assume, the axial stresses in the woo-base langes shoul satisy the ollowing expressions:,c,max, m, σ (9.1),t,max, m, σ (9.) σ,c, c c,0, (9.),t, t,0, σ (9.4) σ,c,max, σ,t,max, σ,c, σ,t, c is the extreme ibre lange esign compressive stress; is the extreme ibre lange esign tensile stress; is the mean lange esign compressive stress; is the mean lange esign tensile stress; is a actor which taes into account lateral instability. Key: (1) compression () tension Figure 9.1 Thin-webbe beams The actor c may be etermine (conservatively, especially or box beams) accoring to 6.. with 7

73 l λ z 1 b c l c is the istance between the sections where lateral election o the compressive lange is prevente; b is given in Figure 9.1. I a special investigation is mae with respect to the lateral instability o the beam as a whole, it may be assume that c 1,0. The axial stresses in the webs shoul satisy the ollowing expressions: w,c, c,w, (9.5) σ (9.6) σ (9.7) w,t, t,w, σ w,c, an σ w,t, are the esign compressive an tensile stresses in the webs; c,w, an t,w, are the esign compressive an tensile bening strengths o the webs. Unless other values are given, the esign in-plane bening strength o the webs shoul be taen as the esign tensile or compressive strength. It shall be veriie that any glue splices have suicient strength. Unless a etaile bucling analysis is mae it shoul be veriie that: h w an 70b (9.8) w F v,w,e 0,5( h,t + h,c ) bw hw 1 + v,0, or hw 5bw hw 0,5( h + h ) 5 b 1 + or 5 b h 70b,t,c w v,0, w w w hw F v,w,e is the esign shear orce acting on each web; h w h,c h,t b w is the clear istance between langes; is the compressive lange epth; is the tensile lange epth; is the with o each web; v,0, is the esign panel shear strength. (9.9) For webs o woo-base panels, it shoul, or sections 1-1 in Figure 9.1, be veriie that: 74

74 τ or h 4 b 4b or h > 4 b v,90, e mean, 0,8 e v,90, e h τ mean, is the esign shear stress at the sections 1-1, assuming a uniorm stress istribution; v,90, is the esign planar (rolling) shear strength o the web; h is either h,c or h,t. b e b b w w (9.10) or boxe beams (9.11) / or I-beams 9..1 Glue thin-lange beams This section assumes a linear variation o strain over the epth o the beam. In the strength veriication o glue thin-lange beams, account shall be taen o the nonuniorm istribution o stresses in the langes ue to shear lag an bucling. Unless a more etaile calculation is mae, the assembly shoul be consiere as a number o I-beams or U-beams (see Figure 9.) with eective lange withs b e, as ollows: For I-beams b b + b (or b + b ) (9.1) For U-beams e c,e w t,e w b 0,5 b + b (or 0,5 b + b ) (9.1) e c,e w t,e w The values o b c,e an b t,e shoul not be greater than the maximum value calculate or shear lag rom Table 9.1. In aition the value o b c,e shoul not be greater than the maximum value calculate or plate bucling rom Table 9.1. Maximum eective lange withs ue to the eects o shear lag an plate bucling shoul be taen rom Table 9.1, where l is the span o the beam. 75

75 Table 9.1 Maximum eective lange withs ue to the eects o shear lag an plate bucling Flange material Shear lag Plate bucling Plywoo, with grain irection in the outer plies: Parallel to the webs 0,1l 0h Perpenicular to the webs 0,1l 5h Oriente stran boar 0,15l 5h Particleboar or ibreboar 0,l 0h with ranom ibre orientation Unless a etaile bucling investigation is mae, the unrestraine lange with shoul not be greater than twice the eective lange with ue to plate bucling, rom Table 9.1. For webs o woo-base panels, it shoul, or sections 1-1 o an I-shape cross-section in Figure 9., be veriie that: τ mean, v,90, or bw 8h 0,8 8h or b > 8h v,90, w bw τ mean, is the esign shear stress at the sections 1-1, assuming a uniorm stress istribution; v,90, is the esign planar (rolling) shear strength o the lange. (9.14) For section 1-1 o a U-shape cross-section, the same expressions shoul be veriie, but with 8h substitute by 4h. The axial stresses in the langes, base on the relevant eective lange with, shoul satisy the ollowing expressions: σ (9.15),c,,c, σ (9.16),t, σ,c, σ,t,,c,,t,,t, is the mean lange esign compressive stress; is the mean lange esign tensile stress; is the lange esign compressive strength; is the lange esign tensile strength. It shall be veriie that any glue splices have suicient strength. The axial stresses in the woo-base webs shoul satisy the expressions (9.6) to (9.7) eine in

76 Figure 9. Thin-lange beam 9.1. Mechanically jointe beams I the cross-section o a structural member is compose o several parts connecte by mechanical asteners, consieration shall be given to the inluence o the slip occurring in the joints. Calculations shoul be carrie out assuming a linear relationship between orce an slip. I the spacing o the asteners varies in the longituinal irection accoring to the shear orce between s min an s max (< 4s min ), an eective spacing s e may be use as ollows: s 0,75 s + 0, 5 s (9.17) e min max NOTE: A metho or the calculation o the loa-carrying capacity o mechanically jointe beams is given in Chapter Mechanically jointe an glue columns Deormations ue to slip in joints, to shear an bening in pacs, gussets, shats an langes, an to axial orces in the lattice shall be taen into account in the strength veriication. NOTE: A metho or the calculation o the loa-carrying capacity o I- an box-columns, space columns an lattice columns is given in Chapter

77 10 Mechanically jointe beams 10.1 Simpliie analysis Cross-sections The cross-sections shown in Figure 10.1 are consiere Assumptions The esign metho is base on the theory o linear elasticity an the ollowing assumptions: the beams are simply supporte with a span l. For continuous beams the expressions may be use with l equal to 0,8 o the relevant span an or cantilevere beams with l equal to twice the cantilever length the iniviual parts (o woo, woo-base panels) are either ull length or mae with glue en joints the iniviual parts are connecte to each other by mechanical asteners with a slip moulus K the spacing s between the asteners is constant or varies uniormly accoring to the shear orce between s min an s max, with s max < 4 s min the loa is acting in the z-irection giving a moment M M(x) varying sinusoially or parabolically an a shear orce V V(x) Spacings Where a lange consists o two parts jointe to a web or where a web consists o two parts (as in a box beam), the spacing s i is etermine by the sum o the asteners per unit length in the two jointing planes Delections resulting rom bening moments Delections are calculate by using an eective bening stiness (EI) e, etermine in accorance with

78 Key: (1) spacing: s 1 slip moulus: K 1 loa: F 1 () spacing: s slip moulus: K loa: F Figure 10.1 Cross-section (let) an istribution o bening stresses (right). All measurements are positive except or a which is taen as positive as shown. 79

79 10. Eective bening stiness The eective bening stiness shoul be taen as: e E i i + γ i i i i i 1 ( EI) ( I E A a ) (10.1) using mean values o E an A b h (10.) i i i b h i 1 I i i (10.) γ 1 (10.4) γ i 1 π E i Ai s /( i K i l ) + or i 1 an i a γ E A ( h + h ) - γ E A ( h + h ) Σ i 1 γ E A i i i -1 where the symbols are eine in Figure K i K ser,i or the serviceability limit state calculations; K i K u,i or the ultimate limit state calculations. For T-sections h 0 (10.5) (10.6) 10. Normal stresses The normal stresses shoul be taen as: γ i Ei ai M σ i (10.7) ( E I ) e 0,5E h M i i σ m,i (10.8) ( E I) e 10.4 Maximum shear stress The maximum shear stresses occur where the normal stresses are zero. The maximum shear stresses in the web member (part in Figure 10.1) shoul be taen as: τ,max γ E A a + 0,5 E b h V (10.9) b ( E I) e 10.5 Fastener loa The loa on a astener shoul be taen as: γ E A a s F ( EI) e i i i i i i V (10.10) i 1 an, respectively; s i s i (x) is the spacing o the asteners as eine in

80 11 Built-up columns 11.1 General Assumptions The ollowing assumptions apply: the columns are simply supporte with a length l; the iniviual parts are ull length; the loa is an axial orce F c acting at the geometric centre o gravity, (see 11..) Loa-carrying capacity For column election in the y-irection (see Figure 11.1 an Figure 11.) the loa-carrying capacity shoul be taen as the sum o the loa-carrying capacities o the iniviual members. For column election in the z-irection (see Figure 11.1 an Figure 11.) it shoul be veriie that: σ c,0, c c,0, (11.1) F c, σ c,0, (11.) Atot A tot is the total cross-sectional area; c is etermine in accorance with 6.. but with an eective slenerness ratio λ e etermine in accorance with sections Mechanically jointe columns Eective slenerness ratio The eective slenerness ratio shoul be taen as: A tot λ e l (11.) Ie with I ( EI ) E e e (11.4) mean where (EI) e is etermine in accorance with Chapter Loa on asteners The loa on a astener shoul be etermine in accorance with Chapter 10, where 81

81 V Fc, 10 c Fc, λe 600 Fc, 60 c c or λ < 0 e or 0 λ < 60 e or 60 λ e (11.5) 11.. Combine loas In cases where small moments (e.g. rom sel weight) are acting in aition to axial loa, 6.. applies. 11. Space columns with pacs or gussets Assumptions Columns as shown in Figure 11.1 are consiere, i.e. columns comprising shats space by pacs or gussets. The joints may be either naile or glue or bolte with suitable connectors. The ollowing assumptions apply: the cross-section is compose o two, three or our ientical shats; the cross-sections are symmetrical about both axes; the number o unrestraine bays is at least three, i.e. the shats are at least connecte at the ens an at the thir points; the ree istance a between the shats is not greater than three times the shat thicness h or columns with pacs an not greater than 6 times the shat thicness or columns with gussets; the joints, pacs an gussets are esigne in accorance with 11..; the pac length l satisies the conition: l /a 1,5; there are at least our nails or two bolts with connectors in each shear plane. For naile joints there are at least our nails in a row at each en in the longituinal irection o the column; the gussets satisies the conition: l /a ; the columns are subjecte to concentric axial loas. For columns with two shats A tot an I tot shoul be calculate as A tot A (11.6) ( ) + b h a a Itot (11.7) 1 For columns with three shats A tot an I tot shoul be calculate as 8

82 I A tot A (11.8) tot ( ) ( ) b h + a h + a + h (11.9) 1 Figure 11.1 Space columns 11.. Axial loa-carrying capacity For column election in the y-irection (see Figure 11.) the loa-carrying capacity shoul be taen as the sum o the loa-carrying capacities o the iniviual members. For column election in the z-irection applies with n λ e λ + η λ1 (11.10) λ λ 1 is the slenerness ratio or a soli column with the same length, the same area (A tot ) an the same secon moment o area (I tot ), i.e., λ l Atot / I tot (11.11) is the slenerness ratio or the shats an has to be set into expression (11.10) with a minimum value o at least 0, i.e. 8

83 l1 λ 1 1 h (11.1) n is the number o shats; η is a actor given in Table Table 11.1 The actor η Pacs Gussets Glue Naile Bolte a Glue Naile Permanent/long-term 1 4,5 6 loaing Meium/short-term 1,5 4,5 loaing a with connectors 11.. Loa on asteners, gussets or pacs The loa on the asteners an the gussets or pacs are as shown in Figure 11. with V accoring to section The shear orces on the gussets or pacs, see Figure 11., shoul be calculate rom: T V l 1 (11.1) a1 Figure 11. Shear orce istribution an loas on gussets or pacs 84

84 Wore examples 1 Column with soli cross-section Column with cross-section 100 x 100 mm, bucling length l 000 mm. Timber o strength class C accoring to EN 8 ( c,0, 0 MPa an E 0, MPa ). Design compressive orce N 0 N ( meium-term ). Service class 1. Design compressive strength c,0, c,0, 0 mo 0,8 1, MPa γ 1, Design compressive stress M σ c,0, N A 0 10,0 MPa Slenerness ratio le λ i 000 0, ,8 Bucling resistance σ c,crit π c,crit E 0,05 λ c,0, 0 λrel 1,8 σ 6, ,14 6,1 MPa 10,8 ( ) ( ) 0,5 1 0, 0,5 c rel rel 1 0, 1,8 0, 1,8 + β λ + λ + +,7 c 1 rel + λ 1, 7 +, 7 1,8 0,9 Veriication o ailure conition σ c c,0, c,0, 1,0 0,9 1,4 0,8 < 1 85

85 Beam with soli cross-section Simply supporte timber beam with cross-section 50 x 00 mm, clear span l 500 mm. Timber o strength class C accoring to EN 8 ( m, MPa, v,,4 MPa, E 0, MPa ). Design uniormly istribute loa o Nm -1 ( meium-term ). Service class 1. Design bening an shear strength m, v, m,,0 mo 0,8 1,5 MPa γ 1, M v,,4 mo 0,8 1,48 MPa γ 1, M a) Bening ( beam is assume to be laterally restraine throughout the length o its compression ege ) Veriication o ailure conition σ m, m, σ M q l m, , MPa W 8 W < 1,5 MPa b) Bening ( beam is not assume to be laterally restraine throughout the length o its compression ege ) Bucling resistance σ λ m,crit rel,m crit 0,05 0,78 b E 0, ,4 MPa hl 00 (0, ) m,crit e m, 1,06 σ 18,4 1,56 0,75 λ 1,56 0,75 1,06 0,76 rel,m crit m, 0, 76 1,5 10, MPa Veriication o ailure conition σ σ m, crit m, M 1 q l m, 9, MPa < 10, MPa W 8 W

86 c) Shear cr v, 0,67 1,48 0,99 MPa cr 0, 67 is taing into account cracs cause by too rapi rying Veriication o ailure conition τ τ v, cr v, V A ,5 MPa 0,99 MPa v, < Step joint Joint o a compression member with cross-section 140 x 140 mm, see Figure below ( cutting epth is 45 mm, shear length in chor 50 mm an β 45 ). Design values o timber properties are c,0, 11,0 MPa, c,90,,1 MPa, v, 1, MPa ). Design compressive orce N 55 N. Design compressive strength at an angle to the grain c,α, c,0, c,90 c,90, c,0, sin α + cos α 11,0 sin,81 11,0,5 o + cos,5 o 7,7 MPa 87

87 Veriication o ailure conitions N cos α 5510 cos,5 σ c,α, bt τ v, z z N cosβ cos 45 bl o o 7,45 MPa < 7,7 MPa 1,11 MPa < 1, MPa 4 Timber-rame wall The walls assembly presente in Fig. 1 is subjecte to the total esign horizontal orce F H,,totx 5 N (short-term) acting at the top o the wall assembly. F H,,tot F H, h n tot b b timber rame F i,t,e b y F i,c,e F F H,,tot H, z t n sheathing boar Figure 1: Example o the wall assembly. The single panel wall element o actual imensions h 6.5 cm an b 15 cm is compose o timber stus (x9x9 cm an 1x4.4x9 cm) an timber girers (x8x9 cm). The plywoo sheathing boars o the thicness t15 mm are ixe to the timber rame using staples o Φ1.5 mm an length l 5 mm at an average spacing o s 75 mm (Fig. ). 88

88 y i A t, E t y A b, E b y i t a i 58 b 15 cm Figure : Cross-section o the single wall element. Material properties or the timber o quality C are taen rom EN8 an or the Sweian plywoo boars (S-plywoo) rom Stec»Holzwerstoe Sperrholz, Holzbauwere: Bemessung un Baustoe nach Eurocoe 5, Step 1«, All material properties are liste in Table 1. Table 1. Properties o use materials. E 0,m m, t,0, c,0, ρ ρ m [N/mm ] [N/mm ] [N/mm ] [N/mm ] [g/m ] [g/m ] C S plywoo * * The values are given or 1 mm typical thicness o the boar. a.) Characteristic astener yiel moment.6.6 M y,r Nmm b.) Characteristic embement strength in plywoo: in timber: h,1, 0.11 ρ h,, 0.08 ρ N / mm 4.54 N / mm c.) Lateral characteristic capacity o an iniviual astener (t 1 15 mm, t 0 mm) Lateral characteristic loa-carrying capacity per staple per shear plane shoul be consiere as equivalent to that o two nails with the staple iameter: F 1,R h,1, t N 89

89 F F F F F,R h,, t N h,1, t1 t t t t F ax,r β + β N 1 t 1 t + β 1 t β + 1 t + β ( ) M h,1, t1 β + β y,r Fax,R 1.05 β ( 1+ β ) + β + + β h,1, t N 4 ( ) M h,1, t β + β y,r Fax,R 1.05 β (1+ β ) + β + + β h,1, t N 1.15 β Fax,R M y,r h,1, + 1+ β N v,r,r,r,r F,R N.) Characteristic racing loa-carrying capacity o one wall panel (Eurocoe 5-1-1; Metho A) F,R bi ci Fi,v,R N s 7.5 bi 15 c ; b0 b 6.5 i 0 h N e.) Characteristic racing loa-carrying capacity o the wall assembly (the wall element with the opening is not consiere) Fv,R Fi,v, R N 7.74 N.) Design racing loa-carrying capacity o the wall assembly ( mo 0.9) F F γ v,r v,r mo M g.) Ultimate limit state criteria F v,r > F H,, tot 6.1 N > 5.0 KN 6.1 N h.) Design external orces in the supports (Fig. 1) FH, h Fi,c,E Fi,t,E 6.5 N b 15 90

90 5 Single tapere beam Assessment o a single tapere beam (Fig. 10.1). Material: glue laminate timber (GL 4h), service class 1. Characteristic values: Dea loa g 4,5 Nm -1, snow s 4,5 Nm -1. Materials an geometrical characteristics o the beam: Fig Scheme o the single tapere beam Span: L 1 m Depth o the beam at the apex: h ap 100 mm Angle o the taper: α 0 With o the beam: b 140 mm Precamber o the beam: w c 0 mm m,g, 4 MPa v,g,,7 MPa c,90,g,,7 MPa t,90,g, 0,4 MPa E 0,mean,g MPa The beam is prevente against lateral-torsional bucling. Design bening strength m, g, 4 m, g, mo 0,9 17, 8 MPa γ M 1,5 Design shear strength v, g,,7 v, g, mo 0,9 1, 94 MPa γ M 1,5 Design compressive strength perpenicular to the grain c,90, g,,7 c, 90, g, mo 0,9 1, 94 MPa γ M 1,5 Basic combination o the loa q 1,5g + 1,5p 1,54,5 + 1,54,5 1,85 Nm -1 Shear orce at a support L 1 V q 1,85 76, 95 N Depth o the beam at the support 0 hs hap tgα L 1, tg 1 0, 571 m 91

91 Veriication o ailure conitions a) Shear at support V 76,95 10 τ v 1,44 MPa 1, 94 MPa, bh < 0 b) Bening at critical cross-section Critical cross-section position L 1 x,87 m hap 1, h 0,571 s Depth o the beam at critical cross-section hap 1, hx 0, 774 m hap 1, h 0,571 s Bening moment at critical cross-section q x 1,85,87 M V x 76,95,87 01, 76 Nm Stress at critical cross-section 6M σ m,0, σ m, α, bh σ σ σ m, o, m, g, m,0, x , ,4 MPa < 17, 8 MPa m, α, m, α m, g, m, 1+ 1,5 1 allowe m, α 0 0 g, m, g, v, g, tgα + c,90, g, tg α 17,8 1+ tg 1,5 1, ,8 + tg 1,94 0,911 σ m,α, 14,4 MPa < 0,911 17,8 15, 74 MPa allowe c) Delection wm u w 0 Coeicient u see Fig hs + hap 0, , h0 0,886 m hap 1,,10 u 1,1166 h 0,571 s e 0,6 9

92 Fig. 10. Coeicient u c1) Instantaneous election g L 5 4, w g u 1, E I inst, 14, 4 y mm s L 5 4, winst, s u 1, , 4 mm 84 E I w inst w inst, g + w inst, s c) Final election w w 1+ w y L L 14,4 + 14,4 8,84 mm < allowe ( e ) 14,4 ( 1+ 0,6), mm ( + ) 14,4 ( ,6) 14, mm in, g inst, g 07 in, s winst, s 1 ψ e 4 L L w in w in, g + w in, s, ,4 7,49 mm < allowe 0 50 c) Net inal election L L wnet, in w in wc 7,49 0 7,49 mm < allowe

93 6 Double tapere beam Problem: snow: 7,0 N/m ea weight (incluing beam):,0 N/m h 0 L c h c α h ap L/ L/ h mm h ap 1100 mm L 0000 mm with o beam: b 190 mm Glulam: GL6c m, 6 MPa v,,8 MPa c,90,, Mpa t,90, 0, 5 MPa Loa uration: short term p 1,5 7,0 + 1,,0 1,9 N/m Service class: mo 0,9 Assumption: Lateral torsional bucling is prevente by suicient transverse bracing ( crit 1 ) Ultimate limit state Design strength: mo 0,9 0,7 m, 0, 7 6 5, 9 MPa γ 1, 5 M v, 0,7,8,74 MPa; c,90, 0, 7,, 8 MPa; t,90, 0, 7 0,5 0,6 MPa Critical section with respect to bening, or a uniormly istribute loa, is at istance L L( h h ) 0000( ) 5450 mm rom the support, where c 0 ap h h + ( h h ) L / L mm c 0 ap 0 c Also: tan α ( hap h0 ) /(0,5 L) ( ) / ,05 Nominal bening stress at critical section: σ 6 M 0,5 pl ( L L ) 1,9 5,45(0 5,45) 10 1, MPa c c c m, α, Wc bhc / Veriication o ailure conition, (6.8), σ m, α, m, α m, where the stress moiication actor ue to compression at the tapere ege is eine by (6.40): m, α 1 0,95 m, m, 1+ tanα + tan α 1,5 v, c,90, 94

94 Hence m, α m, 0, 95 5,9 4, 7 MPa > σ m, α, 1, MPa At the apex, the bening stress is eine by (6.4): 6M ap, m, l bhap σ where + α + α l 1 1,4 tan 5, 4 tan 1,084 61,9 0 / 8 6 σ m, 1, , The requirement, (6.41), is: σ,, m r m MPa Since r 1, 0 (see 6.49) the bening stress at apex is well below the limit. Largest tensile stress perpenicular to grain is eine by (6.54): 6M ap, t,90, p bhap σ where 5 0, tanα 0, 01 (see 6.56) 61,9 0 / 8 6 σ t,90, 0, , The esign requirement is, (6.5), τ σ p MPa t,90, + + < v, is vol t,90, 0 0,17,74 1, 40,5 0,6 0,6 1 The volume actor, vol, has been etermine by (6.51) with V 0,19 1,1 1,1 0, m. The shear stresses shoul, accoring to the current version o the coe, not excee the shear strength τ. However, a moiication to the coe, reucing the with o the section by a cracing actor cr, will most liely be mae in the near uture. The value or glulam is 0,67. For a rectangular section this means that the shear stress shoul not excee cr τ 0, 67, 74 1,8 MPa cr Maximum shear stress, at the support, V τ 1,70 MPa < A Conclusion: All strength requirements are satisie. Serviceability limit state 1,8 MPa Maximum isplacement or this beam, ue to a uniormly istribute loa, is (by a computer analysis) oun to be 1,6 times that o a corresponing beam with uniorm height equal to h 1100 mm. For GL6c: E MPa. From Section.1.: ap w inst 4 5 p , 6 10,96 p /1 w w (1 + ) + w (1 + ψ ) net, in inst, G e inst, Q,1 e w net, in 10,96 (1 + 0,8) + 10, 96 7(1 + 0, 0,8) 9,5 + 89, 0 18,5 mm 95

95 In other wors, w, L /155, which is well above the recommene value o table 7.. Conclusion: net in The isplacement may, epening on the type o builing, be too large. It may be consiere to prouce the beam with a precamber o, say 100 mm. 7 Moment resisting joint Design an assessment o moment resisting joint in the corner o the three-hinge plane rame. Material: glue laminate timber (GL 4h), service class 1. Geometrical characteristics o the rame: ,5º Span: L 5 m Depth o the rater: h R 1480 mm With o the rater: b R 00 mm Depth o the column: h C 1480 mm With o the column: b C 10 mm Angle o the rater: α Material properties (characteristic values): m,g, 4 MPa v,g,,7 MPa ρ 80 g/m Design bening strength m, g, 4 m, g, mo 0,9 17, 8MPa γ M 1,5 Design shear strength v, g,,7 v, g, mo 0,9 1, 94MPa γ 1,5 M Dowels: Steel grae S5 4 mm (4.6): u, 400 MPa Internal orces at the corner: Column: M Nmm V,C N N,C N Rater: M Nmm V,R N N,R N Design o owel joints: 96

96 Outer circle: r1 0.5h mm r mm Insie circle: r r mm r 54 mm Number o owels in circles: π r1 π 644 n s n 1 8 π r π 54 n. 8 s n Loa o owels: Loa o owel in column an rater o the rame ue to bening moment: r FM M N n1r1 + nr Loa o owel in column o the rame ue to shear an normal orce: V, C FV, C N n + n N, C FN, C N n1 + n 8 + Loa o owel in rater o the rame ue to shear an normal orce: V, R FV, R N n + n N, R FN, R N n1 + n 8 + Total loa o owel in the axis o the rater an column o the rame: ( F + F ) + F ( ) + ( ) 7.9 N F, C M V, C N, C 10 ( F + F ) + F ( ) + ( ) 7.71 N F, R M V, R N, R 10 97

97 Shear orce in column an rater in joint: 6 M n1r1 + n r VM n1r1 nr π + π + V, C FV,, C VM N V, R FV,, R VM N N The mechanical properties o owels: Embeing strength in ibres irection (characteristic value): h, 0, 0,08 1 0,01 ρ ( ) ( ) MPa a) Carrying capacity o owel in column axis: Angle between loa an timber ibres: FM + FV, C α 1 arctg arctg 8. 7 FN, C π α α α ( ) 6. Embeing strength (characteristic value): h,0,.68 h, 1, MPa sin α + cos α 1.71sin cos h,0,.68 h,,. 49 MPa 90 sin α + cos α 1.71sin 6. + cos 6. h,,.49 β h,1, Yiel moment (characteristic value):.6.6 M y, R 0. u, t1 10mm, t 00mm Nmm 98

98 ) ( ) ( ) ( 4 ) ( , min, * *,,1,, *, 1,1,, 1,1,,, 1,1,,, R ax R ax h R y R ax h R y h h h C R v F N F M N F t M t N t N t F β β β β β β β β N F F M R v C R v, mo,, γ b) Carrying capacity o owel in rater axis: Angle between loa an timber ibres: ,, arctg F F F arctg R N R V M α α 1 α π α Embeing strength (characteristic value): MPa h h cos 1. sin cos sin ,0, 1,, + + α α MPa h h cos 8. sin cos sin 90,0,,, + + α α ,1,,, h h β t 10mm 1, mm t 00

99 ) ( ) ( ) ( 4 ) ( , min, * *,,1,, *, 1,1,, 1,1,,, 1,1,,, R ax R ax h R y R ax h R y h h h R R v F N F M N F t M t N t N t F β β β β β β β β N F F M R v R R v, mo,, γ Veriication o ailure conitions: a) Carrying capacity o the joint o rame column an rater assessment: - Column: N F N F C R v C,,, allowe - Rater: N F N F R R v R,,, allowe b) Shear stress in rame column an rater assessment: - Column: MPa MPa h b F g v C V C v ,,,,, τ allowe - Rater: MPa MPa h b F g v R V R v ,,,,, τ allowe

100 17 Joint transmitting incline orces Problem: Determine the largest esign orce F that can be transmitte by means o bolts with a characteristic tensile strength o u, 800 MPa. Other problem characteristics are: - Timber quality: C0 (all members): ρ 80 g/m - Loaing is short term, an service class is Minimum spacing as well as ege an en istances suggest 4 bolts, an with respect to the iagonal, in which the orce is parallel to grain, we nee a total with o at least , where is the bolt iameter. Hence 14 mm is the largest bolt iameter possible. For asteners in ouble shear in timber-to-timber connections the characteristic loa-carrying capacity per shear plane is etermine by the ailure moes g, h, j an o Eq. (8.7). The yiel moment or one bolt is: M Nmm,6,6 y, R 0, u, 0, We irst consier the orce F which is parallel to grain in the iagonal, but orms an angle o 45 egrees with the grain o the chor. With 90 1,5 + 0, 015 1,5 + 0, 1 1, 56 we in the ollowing characteristic embement strengths (se Eqs (8.) an (8.1)): h,, 0, 08(1 0, 01 ) ρ 0, 080, ,8 MPa (iagonal) 6,8 0,9 MPa (chor) sin α + cos α 1,56 0,5 + 0,5 h,, h,1, 90 h,, β h,1, 1,8 101

101 Disregaring the rope eect, the ormulas o (8.7) give the ollowing characteristic capacities per bolt an shear plane: g: N h: 9005 N j: 950 N : 1415 N The capacity is governe by ailure moe h, an since this moe is inepenent o the axial withrawal capacity, the rope eect oes not come into play. In orer to etermine the eective number o bolts we nee to now the istance a 1 (see igure). With reerence to the igure we choose the ollowing istances: a 4t(1) 55 mm > ( + sin45) 48 mm a c() 78 mm > 4 56 mm a 4c(1) 50 mm > 4 mm a 1() 11 mm > 5 70 mm a () 60 mm > 4 56 mm a 4c() 44 mm > 4 mm a e () min, min 1,7, 1,7, an the characteristic 1 capacity o the entire connection is: F () (1,7 ) ,0 N 0,9 1() Hence, with n : n n 4 n { } Accoring to 8.1. (5) we also nee to chec the loa-carrying capacity o the horizontal component o the orce F. This problem is eine by a orce 0,71F in the chor (parallel to grain) being transmitte to the iagonal: With n an a a 85 mm, we in: n (1) 1,54 1(1) () e We also nee to compute new capacities per bolt an shear plane, since the orce is now parallel to the chor grain, but acts at an angle o 45 egrees in the iagonal. Hence:,1, 6,8 MPa an,, 0, 9 MPa h h h,, β Again, isregaring the rope eect, the ormulas o (8.7) now give the ollowing characteristic capacities per bolt an shear plane: h,1, g: N h: 705 N j: 100 N : 1415 N 0,78 Again, ailure moe h governs, an we now in the capacity o the entire connection to be: F (1) (1,54 ) 705 /0, ,0 N Although there is little in it, it is the horizontal component o F that governs the capacity. With mo 0,9 an γ M 1, we in the esign capacity o the connection to be mo F F 61,0 0,9 /1, 4, N γ M The characteristic splitting capacity o the connection is, accoring to (8.4), he F90, R 14bw 14 (48) ,5 N he h 198 I we assume that the vertical component o F, that is 0,71 61,0 4, N, is ivie into two equal shear orces on each sie o the connection, splitting is no problem, but we o not have suicient inormation about the problem to mae this claim. 10

102 Literature Breyer, D. E.: Design o Woo Structures, McGraw-Hill Boo Company, 1980 Kollmann, F. P.; Côté, W. A.: Principles o Woo Science an Technology, Volume Ι: Soli Woo, Springer-Verlag, Berlin 1967 Timber Engineering, Centrum Hout, 1995, ISBN Normative reerences Eurocoe 5 Design o timber structures - Part 1-1: General rules an rules or builings Eurocoe 5 Design o timber structures - Part 1-: Structural ire esign Eurocoe 5 Design o timber structures - Part : Briges ISO stanars: ISO 081:1986 Metallic coatings. Electroplate coatings o zinc on iron or steel ISO 61-:1989 Evaluation o human exposure to whole-boy vibration. Part : Continuous an shoc-inuce vibrations in builings (1 to 80 Hz) EN stanars: EN 00:1997 EN 01:199 EN 1-4:1996 EN 1-5:1997 EN 1-6:1996 EN 1-7:1997 EN 5-1:199 EN 5-:199 EN 5-:1995 Oriente Stran Boar (OSB) Deinition, classiication an speciications Ahesives, phenolic an aminoplastic or loa-bearing timber structures; classiication an perormance requirements Particleboars Speciications. Part 4: Requirements or loabearing boars or use in ry conitions Particleboars Speciications. Part 5: Requirements or loabearing boars or use in humi conitions Particleboars Speciications. Part 6: Requirements or heavy uty loa-bearing boars or use in ry conitions Particleboars Speciications. Part 7: Requirements or heavy uty loa-bearing boars or use in humi conitions Durability o woo an woo-base proucts einition o hazar classes o biological attac. Part 1: General Durability o woo an woo-base proucts einition o hazar classes o biological attac. Part : Application to soli woo Durability o woo an woo-base proucts Deinition o hazar classes o biological attac. Part : Application to woobase panels 10

103 EN 50-:1994 EN 51-1:1995 EN 8:199 EN 85:001 EN 87:001 EN 409:199 EN 460:1994 EN 594:1995 EN 6-:1997 EN 6-:1997 EN 6-4:1997 EN 6-5:1997 EN 66-1:1996 EN 66-:1996 EN 66-:1996 EN 91:1999 EN 1075:1999 EN 180:1999 EN 181:1999 EN 18:1999 EN 18:1999 Durability o woo an woo-base proucts Natural urability o soli woo. Part : Guie to natural urability an treatability o selecte woo species o importance in Europe Durability o woo an woo-base proucts Preservative treate soli woo. Part 1: Classiication o preservative penetration an retention Timber structures Test methos. Determination o embeing strength an ounation values or owel type asteners Finger jointe structural timber. Perormance requirements an minimum prouction requirements Glue laminate timber Prouction requirements or large inger joints. Perormance requirements an minimum prouction requirements Timber structures Test methos. Determination o the yiel moment o owel type asteners Nails Durability o woo an woo-base proucts Natural urability o soli woo Guie o the urability requirements or woo to be use in hazar classes Timber structures Test methos Racing strength an stiness o timber rame wall panels Fibreboars Speciications. Part : Requirements or harboars Fibreboars Speciications. Part : Requirements or meium boars Fibreboars Speciications. Part 4: Requirements or sotboars Fibreboars Speciications. Part 5: Requirements or ry process boars (MDF) Plywoo Speciications. Part 1: Requirements or plywoo or use in ry conitions Plywoo Speciications. Part : Requirements or plywoo or use in humi conitions Plywoo Speciications. Part : Requirements or plywoo or use in exterior conitions Timber asteners Speciications or connectors or timber Timber structures Test methos. Testing o joints mae with punche metal plate asteners Timber structures Test methos Loa bearing naile joints Timber structures Test methos Loa bearing staple joints Timber structures Test methos Withrawal capacity o timber asteners Timber structures Test methos Pull through testing o timber asteners 104

104 EN 1990:00 Eurocoe Basis o structural esign EN :00 Eurocoe 1: Actions on structures Part 1-: General actions Densities, sel-weight an impose loas EN Eurocoe 1: Actions on structures Part 1-: General actions Snow loas EN Eurocoe 1: Actions on structures Part 1-4: General actions Win loas EN Eurocoe 1: Actions on structures Part 1-5: General actions Thermal actions EN Eurocoe 1: Actions on structures Part 1-6: General actions Actions uring execution EN Eurocoe 1: Actions on structures Part 1-7: General actions Acciental actions ue to impact an explosions EN 10147:000 EN 171:001 EN 1986 EN EN EN 1450 EN 1479 Speciication or continuously hot-ip zinc coate structural steel sheet an strip Technical elivery conitions Timber asteners Characteristic loa-carrying capacities an slip mouli or connector joints Woo-base panels or use in construction Characteristics, evaluation o conormity an maring Timber structures Glue laminate timber Requirements Timber structures Strength grae structural timber with rectangular cross-section Part 1, General requirements Timber structures. Prouction requirements or abricate trusses using punche metal plate asteners Laminate veneer lumber (LVL) Speciications, einitions, classiication an requirements EN 1458 Timber structures Fasteners an woo-base proucts Calculation o characteristic 5-percentile value an acceptance criteria or a sample EN 1474 Timber structures Structural laminate veneer lumber Requirements EN Strength grae structural timber with roun cross-section Requirements EN Timber structures Connectors Requirements EN 1459 EN 6891:1991 EN 8970:1991 Timber structures Fasteners Requirements Timber structures. Joints mae with mechanical asteners. General principles or the etermination o strength an eormation characteristics Timber structures. Testing o joints mae with mechanical asteners; requirements or woo ensity (ISO 8970:1989) 105