1 Introduction to the Recommendations and their Application Principles

Transcription

1 1 Introuction to the Recommenations an their Application Principles 1.1 National an International Regulations for Piling Wors (1) Since the implementation ofdin EN : : Eurocoe 7: Geotechnical Design Part 1: General Rules, pile analysis an esign in Germany is governeby Section 7ofEurocoe EC7-1 (Eurocoe 7), in conjunctionwith DIN1054: : Subsoil Verification of the Safety ofearthwors an Founations Supplementary Rules tothe German version DIN EN , anthe National Annex to EC 7-1, namely DINEN1997-1/NA: : National Annex Nationally Determine Parameters Eurocoe 7: Geotechnical Design Part 1: General Rules. These three coorinate ocuments are summarise in the German Eurocoe 7 Hanboo,Volume1[44]. Note: In case amenments or corrections are mae to the stanars inclue in the German Eurocoe 7 Hanboo, Volume 1[44], the changes must be aopte even when not yet incorporate in [44]. (2) In aition, the iniviual pile systems are governe by the following execution stanars: DINEN1536: DINSPEC18140: DINEN12699: DINSPEC18538: DINEN14199: DINSPEC18539: DINEN12794: DINEN1993-5: Execution of special geotechnicalwors Bore piles. Supplementary provisions to DINEN1536. Execution ofspecial geotechnical wors Displacement piles. Supplementary provisions to DINEN Executionofspecialgeotechnicalwors Micropiles. Supplementary provisions to DINEN Precastconcrete proucts Founation piles. Designofsteel structures Part 5: Piling. (3) Because iaphragm wall elements are often employe in the same way as pile founations, the respective execution stanar must also be consiere: DINEN1538: in conjunction with: DIN4126: Execution of special geotechnical wors Diaphragm walls Stability analysis of iaphragm walls. Recommenations on Piling EAPfähle. Eitors: German Geotechnical Society (DeutscheGesellschaft für Geotechni e.v.) 2014 Ernst &Sohn GmbH&Co. KG. Publishe 2014 by Ernst&Sohn GmbH&Co. KG. 1

2 (4) In aition, several ISO stanars are being compile for a number of special topics relating topiles. They are however not liely tobeimplemente as builing regulations in Germany.Currently,these inclue: DIN EN ISO : 2 Geotechnical investigation an testing Testing of geotechnical structures Part 1: Pile loa test bystatic axially loae compression. On a national basis, the regulations in Section 9 shoul be aopte for static pile testing. 1.2 Types of Analysis an Limit States using the Partial Safety Factor Approach New stanars generation an their application to pile founations (1) By European Commission ecision national builing esign an execution stanars either alreay have been or will in future be replace by European stanars. Actually numerous European stanars have been publishe for geotechnical esignan execution ofspecial geotechnical wors. (2) The European stanars governing pile executionare liste in 1.1. (3) Analysis an esign of pile founations is ealt with in the European stanar DIN EN : Geotechnical Design (Eurocoe 7) in conjunction with DIN 1054 an DIN EN /NA, see 1.1. These three stanars were implemente by the German Builing Authorities for use in Germany as of (4) Until the time of implementation ofthe Eurocoes asbining builing regulations a new generation of national stanars using the partial safety factor approach serve as temporary solution for all fiels of structural engineering. The following stanars inparticular represente the governing stanars forpile founations: DIN : : DIN1054: : DIN18800: : DIN : : Basis of structural esign; Verificationofthe safetyofearthwors anfouna- tions; Steel structuresan; Concrete, reinforcean prestresse concretestruc- tures Part 2: Concrete Specification, properties, prouctionan conformity Applicationrules for DINEN (5) These Recommenations on Piling (EA-Pfähle) are base on the stanars liste in 1.1 above an, for esign in particular, on Eurocoe EC 7-1, in conjunction with DIN1054 an thenaasstipulate in 1.1 (1).

3 1.2.2 Actions, effects an resistances (1) The partial safety factor approach has its origins in probability theory, as use to specify the requisite safety factors from a probabilistic perspective. In contrast to this, with the implementation of DIN 1054: , the new geotechnical stanars generation follows a more pragmatic split of the previously common global safety factors into partial safety factors for actions or effects, an partial safety factors for resistances. (2) The basis for stability analyses is represente by the characteristic values for actions an resistances. The characteristic value, represente by the inex, is avalue of which the specifie probability isassume nottobeexceee or fallen short of uring the reference perio, taing into consieration the esign woring life of the structure or the corresponing esign situation. Characteristic values are generally specifie base on testing, measurements, analyses or empiricism. (3) If the internal or external pile capacity nees to be analyse, the effects at the pile heaoratgiven epths are require: As action effects, e.g. normalforce,shear force,bening moment; As stresses, e.g. compression, tension, bening stress, shear stress orequivalent stress. In aition, further effectsofactions can occur: As ynamicorcyclic loas; As change to the structural element, e.g. strain, eformationorcrac with; As change in the position ofisolate piles orpile groups, e.g. isplacement, settlement,rotation. (4) The cross-section an the internal resistance ofthe material are the governing factors in the esign of iniviual components. Specific stanars are to be applie for this purpose. (5) The characteristic values of the effects are multiplie by partial safety factors, those of resistances are ivie. The values acquire in this way are esignate as esign values of effects or resistances respectively an are characterise by the inex. For stability analyses, ifferent limit states are istinguishe,also see 1.2.3, an 3.1.1(4). (6) In aition to actions, esign situations are also taen into consieration for pile analyses, similar to other structural elements. To this en the previous loaing cases LC 1, LC 2 an LC 3, aopte for use in analysis accoring to DIN 1054: , have been converte to esign situations for use in analyses after DIN EN (EC 7-1) an DIN 1054: , an DIN EN 1990 as follows: BS-P(persistent(esign) situation); BS-T (transient(esign) situation) an; BS-A(acciental (esign)situation). 3

4 In aition, there is the seismic esign situation BS-E. More etaile information isgiven in theec7-1 German Hanboo [44] an in[133] Limit states an national application of the EC 7-1 German Hanboo (1) The term limit state isusewith two ifferentmeanings: a) In soil mechanics, the state of the soil in which isplacements of iniviual soil particles against each other are so great that the mobilisable shear strength achieves its greatest values in either the entire soil mass, or at least in the region of afailure plane, isnown as the limit state of plastic flow. It cannot become greater even if more movement occurs, but coul become smaller. The limit state of plastic flow characterises the active earth pressure, passive earth pressure, bearing capacity, external pile failure, slope stability, anglobal stability. b) Asecon limit state in the sense ofthe new safety factor approach isastate of the loa-bearing structure where, if exceee, the esign requirements are no longer fulfille. (2) The following limit states are ifferentiate using the partial safety factor approach: a) The ultimate limit state is a conition of the structure which, if exceee, immeiately leas to a calculate collapse or another form of failure. It is referre to as ULS in EC 7 an DIN1054. Further istinguishing is escribein(5). b) The serviceability limit state is a conition of the structure which, if exceee, no longer fulfils the conitions specifie for its use. It is referre to as SLS in EC 7an DIN1054. (3) For ultimate limit state analysis (ULS), Eurocoe EC 7-1 provies three options. With one exception (see (6) an (9)), the supplementary rules of DIN1054 for use ingermany are base on Analysis Metho 2ofEC7-1. The partial safety factors are applie to both, effects an resistances. To ifferentiate this from the other permitte scenario, in which the partial safety factors are not applie tothe effects but to the actions, this proceure is esignate as Analysis Metho 2* in [133], also see the EC 7-1 Hanboo [44]. (4) The National Annex to EC 7-1 an DIN 1054 represent a formal lin between EC 7-1 an national German stanars, see EC 7-1 German Hanboo [44]. In DIN 1054 an the National Annex it is state which of the possible analysis methos an partial safety factors are applicable in the respective national omains. In aition, the applicable, supplementary national coes may also be given. The supplementary national coes may not contraict EC 7-1. Moreover, the National Annex may not repeat information alreay given in EC

5 (5) Eurocoe EC 7-1 istinguishes the following suborinate limit states of the ultimate limit state (ULS): a) EQU: Loss of equilibrium of the structure, regare as a rigi boy, or the groun. The esignation iserive from equilibrium. b) STR: Internalfailure or very largeeformations of the structure or its structural elements, where the strength of the materials governs the resistance. The esignation is erive from structural failure. c) GEO: Failure or very large eformation of the structure or the groun, where the strength of the soil or roc governs the resistance. The esignation iserive from geotechnical failure. ) UPL: Loss of equilibrium of the structure orthe groun ue to buoyancy or water pressure.the esignation iserive from uplift. e) HYD: Hyraulic groun failure, internal erosion of or piping in the groun, cause by a flow graient. The esignation is erive from hyraulic failure. (6) In the terminology of the EC 7-1 German Hanboo [44] the GEO limit state is sub-ivie into GEO-2 an GEO-3: a) GEO-2: Failure or very large eformation of the groun in conjunction with the calculation of the action effects an the imensions, i.e. when utilising shear strength for passive earth pressure, for sliing resistance an bearing resistance, an when analysing eep slie surface stability for anchore retaining walls, an for base resistance an sin friction of pile founations. The GEO-2 limit state calculation follows Analysis Metho 2*, see(3), as outline inthe EC 7-1 GermanHanboo [44]. b) GEO-3: Failure or very large eformation of the groun in conjunction with the analysis of the overall stability, i.e. when utilising the shear strength for analysis of the safety against slope failure an global failure an, normally, when analysing slope stabilisation measures, incluing consieration of structural elements, e.g. anchors or piles. The GEO-3 limit state calculation follows Analysis Metho 3 as outline in the EC 7-1 German Hanboo[44]. (7) The EQU, UPL an HYD limit states escribe the loss of static equilibrium. These inclue: a) Safetyanalysis against overturning (EQU); b) Safety analysis against buoyancy or uplift, e.g. of a tension pile group (UPL); c) Safetyanalysis against hyraulic heave (HYD). (8) The limit states EQU, UPL an HYD involve actions only, but no resistances. The governing limit state conition is: F = F γ G γ = G ; (1.1) st stb 5

6 i.e. the estabilising actions F,multiplie by the partial safety factor γ st 1,0, may only beaslarge asthe stabilising action G,multiplie bythe partial safety factor γ stb <1,0. (9) The GEO-2 limit state escribes the failure of structures an structural elements or the failure ofthe groun. It inclues: a) Analysis of the bearing capacity of structures an structural elements subjecte to loas fromthe groun or supporte by the groun; b) Analysis of the bearing capacity of the groun to emonstrate that it is not exceee, e.g. passive earth pressure, bearing resistance, pile resistance or sliing resistance. The analysis to emonstrate that the bearing capacity of the groun is not exceee is performe exactly as for any other construction material. The limit state conition isalways the governingconition: 6 E = E γ R γ = R ; (1.2) F R i.e. the characteristic effect E,multiplie bythe partial safety factor γ F for actions or strains, may only become aslarge as the characteristic resistance R, ivie bythe partial safety factor γ R. (10) The GEO-3 limit state is a peculiarity of earthwors an groun engineering.itescribesthe loss of overallstability. It inclues: a) Analysis of safety against slope failure; b) Analysis of safety against global failure. The limit state conition isalwaysthe governing conition: E R ; (1.3) i.e. the esign value E of the effects may only become as large as the esign value of the resistance R.The geotechnical actions an resistances are etermine using the esign values forshear strength: tanϕ = tanϕ γ an c = c γ an,respectively (1.4a) c tanϕ tanϕ ϕ γ u, = an u, ϕ u, u, c c = c γ ; (1.4b) i.e. the friction tan ϕ an the cohesion c are reuce from the outset using the partialsafety factors γ ϕ an γ c. (11) The serviceability limit state (SLS) escribes the state of a structure or structural element at which the conitions specifie for its use are no longer met, but without loss of its bearing capacity. The analysis is base on the anticipate isplacements an eformations being compatible with the purpose of the structure.

7 1.2.4 Transitional regulations for applying of the Recommenations on Piling in conjunction with the EC7-1 German Hanboo (1) These Recommenations on Piling are base on the provisions of the EC 7-1German Hanboo[44]. (2) Aecisive ifference between the provisions of the EC7-1 German Hanboo [44] an DIN 1054: is the specification of ifferent partial safety factors γ P (lower) an the correlation factors ξ (higher) for pile founations. Overall, however, γ P an ξ result inacomparable magnitue onthe resisting sie, lie DIN 1054: ,see [59]. (3) The existing limit states to DIN 1054: are replace as follows in the EC7-1 German Hanboo [44]: a) The previous GZ 1A limit state to DIN 1054: correspons without restrictions to the EQU, UPL an HYD limit states as in the EC 7-1 German Hanboo[44]. b) The previous GZ 1B limit state to DIN 1054: correspons without restrictions to the STR limit state as in the EC 7-1 German Hanboo [44] as the internal pile capacity (material strength). In aition, there is the GEO-2 limit state as in the EC 7-1 German Hanboo [44], in conjunction with the external esign of the founation elements, e.g. the external pile capacity. c) The previous GZ 1C limit state as in DIN 1054: correspons to the GEO-3 limit state as in the EC 7-1 German Hanboo [44], in conjunction with the analysis of the overall stability, i.e. when utilising the shear strength for analysis of safety against slope failure an global failure. 1.3 Planning an Testing Pile Founations (1) These Recommenations use the terms esigner (planner) as the EC 7-1 German Hanboo[44]an theec7-2 German Hanboo [45]. (2) The esigner shoul consult a specialist pile founation planner if not in possession of the requisite nowlege an experience for pile founation planning. (3) A geotechnical esign report must be compile for pile founations in accorance with the EC 7-1 German Hanboo [44], which must mae reference to the groun investigation report in accorance with the EC 7-2 German Hanboo [45]. (4) Pile founations are classifie as either Geotechnical Category GC 2 or Geotechnical Category GC3.See 3.2 an the EC7-1 German Hanboo [44] for classification criteria. (5) Where pile founations are classifie as Geotechnical Category GC 3, a geotechnical expert with requisite experience must be consulte uring the 7

8 structural engineering appraisal of the groun investigation report an the geotechnical esign report. In particular, the geotechnical expert shoul verify the groun moel, the soil parameters an the esign approach, an, in agreement with the inepenent verifier, shoul carryout comparativeanalyses. (6) The execution of pile founations shoul be supervise by a specialist planner or a geotechnical expert with the requisite experience an specialist nowlege of pile founations. Where pile founations are classifie as Geotechnical Category GC 3, the expert mentione in(5) must also beconsulte to chec the etaile esign an to supervise the pile execution wors. 8