Off-centre anchoring of AZ sheet pile walls. Steel Sheet Piling

Transcription

1 O-centre nchoring o Z sheet pile wlls Steel Sheet Piling

2 Introduction The Z-section sheet piles o the Z series mrketed b rcelor Proil uxembourg dier rom the Z-section sheet piles o competitors nd rom U-section sheet piles in the ollowing ws: the combintion o the dvntgeous Zproile nd the time-proven rssen interlock mke them n economicl solution with superior sectionmodulus-to-weight rtio; the vourble position o interlocks on the outer side, on the extreme ibre, overcomes the problem o trnsmission o sher orce in the interlock, mking crimping unnecessr to gurntee mximum strength. In prctice, however, when sheet piles re to be tied bck, it is not uncommon or U-section piles to be preerred. This choice ismde or detiling resons: with U-section sheet piles both wling bolts nd tie rods cn be centred on the bck o the pile. n economicl solution or nchoring Z piles To enble ull dvntge to be tken o the Z series sheet piles under the most economicl globl conditions, rcelor Proil uxembourg hs developed inncill ttrctive lterntive solution: o-centre nchoring. This solution combines the outstnding sttic properties o Z sheet piles with the simplicit o the nchorges used with Upiles. It simpl involves putting the bolts or tie rods through one o the lnges longside the interlock: this voids the problem o mking hole through the interlock nd using complex bering plte. n economicl solution or nchoring Z sheet piles nchoring o U-section sheet piles I Z-section piles re used, the interlock running down the centre o the trough results in conservtive mesures being dopted, with wlings being ixed with two bolts, thereb incresing mteril costs nd the complexit nd cost o instlltion. I tie rods re to be centred on the trough, the hve to pss through the interlock. This requires specil bering plte with welded shims to bridge the interlock ridge. I the wter tble behind the sheet piles reches the line o tie rods, the hole through the interlock might impir wtertightness. The dvntge o o-centre nchoring is tht it mobilizes the high strength o Zpiles without hving hole through the interlock. The economic dvntges re obvious: o-centre ixing o wlings with single bolt reduces mteril nd instlltion costs, o-centre positioning o tie rods mkes it possible to use plin bering pltes, nd hving hole in the lnge rther thn through the interlock mens chieving eective wterprooing ceses to be problem. Trditionl nchoring o Zpiles 1

3 Reserch project Until now no design regultions hve ddressed the possibilit o o-centre nchoring o Z-section piles. In close collbortion with the Deprtment o Steel Construction o the RWTH in chen, rcelor thereore undertook vst reserch project to nlze the behviour o sheet piles with o-centre nchoring nd to determine the corresponding design rules. This reserch project comprised the ollowing steps: experimentl studies on Zpiles subject to ocentre loding, inite-element modelling bsed on the test results, nlsis o the behviour o double sheet pile (in wll) subject toeccentric loding, drting o design method. The results o the stud were consigned to inl detiled report [1] nd re summrized here or prcticl ppliction. Double Z18 sheet pile ter test hdrulic clinder ws used to ppl orce representing the nchor orce to n o-centre bering plte. or technicl resons the test could onl be crried out on one double-pile unit t time. To simulte lterl continuit, the two piles were cross-brced. The photos o Z18 double piles ter the test ttest to the ductile behviour obtined with this solution. inite-element model clibrtion nd simultions The test results were used to clibrte initeelement model which ws then used or prmetric studies. The inite-element simultions were run t the RWTH Deprtment o Steel Construction. This mde it possible to more precisel consider the boundr conditions pertining to continuous sheet pile wll, conditions which could onl be prtill tken into ccount in the phsicl tests. Experimentl studies The tests on Zpiles where crried out t the RWTH Institute oerrous etllurg. Boundr conditions o double Z pile In principle the locl eccentric orce cn, using simple model, be broken down into smmetricl component nd n ntismmetricl component. smmetricl ntismmetricl Double Z18 sheet pile during test Smmetricl nd ntismmetricl components o orce

4 The deormtions observed during the phsicl tests were conirmed b the inite-element studies. Consequentl, the stud determined the perormnce o the cross-section resulting in reduced moment resistnce or dierent eccentricit ctors ex imposed b the boundr conditions. Deormtion under eccentric orce Stud o moment resistnce Other phsicl tests were lso crried out, nd inite-element simultions o interlock behviour under horizontl tensile orces were run. Deormtion or dierent prmeters The importnce orottion is ected b dierent prmeters such s the spn nd the stiness o the soil behind the sheet pile wll. Stud o interlock strength Development o design method Rottion due to the ntismmetricl component o the orce (highl exggerted) The prmetric studies exmined severl limit sttes tht might rise with eccentric loding under ctul boundr conditions: 1. moment resistnce o the cross-section t the point o ppliction o eccentric orce,. interlock resistnce (declutching), The nlsis o test results nd inite-element prmetric studies served to develop design method tking ccount o boundr conditions nd indirect ctions to which double Zsheet pile is subject under locl eccentric loding. This method complies with Europen stndrd EN nd covers both locl nlsis nd the eect on overll resistnce. The design method or bering pltes proposed below is bsed not onl on the tests described bove but lso on nother stud on the determintion o bering plte sizes [], lso crried out b the RWTH Deprtment o Steel Construction.. sher resistnce (punching sher resistnce) o lnge nd tensile resistnce o web under locl nchor orce.

5 Design method nd prmeters NB: O-centre nchoring cn lso be used in the cse oinclined tie rods; the design rules given here concern onl the horizontl component o nchor orce, however. Procedure: Choose dimensions nd check bering plte Determine eccentricit ctors or ech nchor point nd check resistnce to locl orces Determine reduction coeicients or ech nchor point nd check sheet piling t the nchor level nd generll. Choice o bering plte dimensions Bering plte position The dimensions o the bering plte must be chosen within the limits given below: NB: The nchor nd/or bolt must in ll cses be in the lnge with the overling interlock. Width: b c b b c ength: h. 5 b Thickness: t 40mm t d / wrong right where : b c width oz pile lnge (between illet tngent points) (c Tb. ) t lnge thickness nominl dimeter o bolt or tie rod d Tb. 1: Nominl Bering plte hole dimeters (or guidnce onl) φ dimeter d SW d d mm mm mm (Dimensions rom []) right Right positioning o bering plte d s b s Swivel plte rom [] 4

6 Bering plte check Note : The ollowing expressions re rom report []. NB: The design rules given here lso ppl to inclined tie rods; however, the concern onl the horizontl component o nchor orce. In the cse o inclined tie rods, detil ppropritel to introduce the verticl component into the sheet pile wll, nd mke the necessr dditionl checks. I lignment brckets re required (when the ngles o inclintion re steep), their ppliction must be studied cse b cse. Bering pltes must be checked in bending. There m be severl dierent situtions: nchor without wling (possibl using swivel plte ) bolted wling Ë Ë Ë C Ë B Ë D severl sheet piles nchored together, sunit (possibl using swivel plte ) I there is no wling, there must be n nchor in ech trough. with nut with nut with nut with swivel plte B nchor in ech double pile trough (no wling) nchorge without wling Bering plte check cses & B : no wling, or wling with bolts 4 t Rd, pl ( b φ) X X B with nut: with swivel plte: X h X h d ' I single tie rod is to nchor severl double piles, the o-centre bering plte must be checked in ccordnce with Cor D. The bering pltes or wling bolts must be checked in ccordnce with. 5

7 (double pile) (double pile) (double pile) (wler) (n-1 ) (double pile) (bolt) (double pile) (tie rod) n + (double pile) (double pile) (wling) (bolt) (double pile) Bolt nd nchor orces to be considered with nut bolt ixing bolt ixing with swivel plte C D nchoring o severl double piles Here: (n) with nut nchoring o severl double piles Here: (n) with swivel plte Bering plte check cses C & D : nchorge o severl double piles (n>1) C D 4 n t Rd, pl ( b φ) X with nut: with swivel plte: n 1 h X h X nchors with bolted wling d ' + + X ( n 1 )( s d ') n 1 ( n 1 ) n 1 s where: or & : horizontl component o the nchor orce per double pile dditionl check: C B D or & : horizontl component o the nchor orce per tie rod b,h,t width /length /thickness o bering plte ield strength obering plte d ' lod spred dimeter d SW bolt hed size (spnner size) φ ( d + φ )/ SW or & (with nut): dimeter o hole in bering plte n number o double piles to be nchored s distnce between wling members π C ( d SW φ ) B D ür & (with swivel plte): d s ( b φ ) X where: d S dimeter o semi-clindricl lugs ( 50 mm []) b x min {b S ;b } b S width oswivel plte 6

8 Eccentricit ctor ex, i tnchor point i NB: Ithere ismore thn one level o nchors, ex must be determined seprtel or ech level. The distnce between the top nchorlevel nd the top o the sheet piles must be t lest 1.0 m. evel 1 k S1 1 1 h 1 Eccentricit ctor: α ex, i C C Sm, i nt k S h where: C Sm i h,, k s, i i i i evel or: h, i i < with: i 4 4 EI k s, i, i C k or: Sm, i s, i i h i nchor levels tobe considered where: ex, i eccentricit ctor (dimensionless) C Sm, i stiness o the sstem [N/m ] i h, i elstic length otie rod [m] distnce rom nchor level to top o pile [m] C nt torsionl stiness o sheet pile [N/m ]( rom Tb. ) EI lexurl stiness o sheet pile wll [Nm /m] ( rom Tb. ) k s, i modulus o soil rection t the nchor point in question (verge over length i )[N/m ]( c guideline vlues in Tb. ) Tb. : Guideline vlues or modulus o soil rection k S Ground tpe k S N/m Pet Cl,silt cl,snd/silt cl 5 Silt 10 Snd loose, modertel compct, compct 40, 80, 150 Grvel 100 NB: Ithe soil is strtiied, men vlue or k S tthe nchor level must be ound. 7

9 Tb. : Design prmeters or Z sheet piles with o-centre nchors Sheet piles lnge width Plte width Double pile width lnge thickness Web thickness cm/m Interlock chrcteristic Clssiiction speren

10 Check o resistnce o Z sheet pile wll to locl orce The design resistnce o sheet piling to locl orce (t ech o-centre nchor point) must be checked., i R Rd, Ex, Z min ( R ; R ; R ) ock, Rk V, Rk tw, Rk where: R ( h + b ) t (1 + α ex, ) V, Rk i punching sher resistnce o lnge In the expressions bove:, i Bnchor orce pplied, per double pile nchor orce pplied (horizontl component) ( per liner metre ) B width odouble pile ( rom Tb. ) K interlock chrcteristic coeicient ( rom Tb. ) t,t W lnge thickness /web thickness ( rom Tb. ) b,h width /length obering plte, u ield strength /ultimte tensile strength o Z sheet piles ( rom Tb. 4) ex, i eccentricit ctor t nchor point concerned R R NB: ock, Rk h t ( h ( 1 + α ex, ) tw, Rk W i + b ) K u 1 1 α tensile resistnce o web ex, i interlock resistnce or the interlock resistnce R ock, Rd,tke u (ultimte tensile strength). Tb. 4:Zsheet pile steel grdes Grde Yield strength Ultimte tensile (s per EN 1048) strength u [N/mm ] [N/mm ] S40 GP S70 GP S0 GP S55 GP S90 GP S40 GP NB: or,tke the horizontl component o the nchor orce introduced into the double pile (c digrm on pge 7). Note: The expressions bove, especill K,re derived rom equtions (5.), (5.4), nd (5.5) in document [1]. Reduction coeicients ex, i tnchor point i t the nchor point i considered: β ex, i 1 (1 α ex, i ) C Ex, i where: ex, i reduction coeicient t nchor point i ex, i eccentricit ctor t nchor point, i horizontl component o nchor orce pplied ( per liner metre osheet pile wll) ield strength oz sheet pile ( rom Tb. 4) C Ex chrcteristic vlue or trnsverse bending o sheet pile ( rom Tb. ) I there ismore thn one level o nchors, ex, i must be determined seprtel or ech level. Note: In the cse oretining wlls combining o-centre nchors nd centred nchors or brces, tke ex 1.0 t centred nchor or brcing points. 9

11 Check o bending moment nd sher cpcit o sheet piling t nchor point Clsses 1 nd : c, Rd β ex, i W pl, Net W pl, Net W pl, Gross r W, pl r W, pl φ Clss : c, Rd β ex, i W el, Net W el, Net W el, Gross r W, el r W, el φ nd: V V Rd β ex, i V nd lso, or: V V Rd > 0. 50: -V interction: V, Rd β ex, i W pl, Net ρ V 4 t w' sinα where: V 1 ρ V Rd In the expressions bove: V bending moment in cross-section considered [knm/m] sher orce incross-section considered [kn/m] W el,w pl elstic/plstic section modulus o Z sheet pile [cm /m] (rom Tb. ) V sher re o Z sheet pile [cm /m] (rom Tb. ) ngle o Z sheet pile web [ ] (rom Tb. ) ield strength oz sheet pile (rom Tb. 4) r W φ ex,, i t w reduction coeicient (dimensionless) to tke ccount o reduction o cross-sectionl re t nchor point dimeter o hole in Z sheet pile [m] reduction coeicient totke ccount o eccentricit t nchor point. t w /B[cm/m] 10

12 Checks o generl sections o sheet pile wll Simpliied, tking: ex, min ex, i Clsses 1 nd : Clss : nd: V Sd Sd Sd V Rd c, Rd c, Rd β β β ex, ex, ex, W W ore precise determintion o ex, in generl sections pl el V On condition tht there isno other reduction in cross-sectionl re, the gross section modulus vlues cn be used. To check generl sections (bove, below, nd between nchorges), nd to simpli mtters while still sting on the se side, the smllest o the vlues or ex, i tdjcent nchor points cn be tken or ex,.ore vourble vlues cn be determined s explined below. ore vourble reduction coeicients, ex,,cn be determined or generl sections b tking ccount o: the distnce between the nchor point nd the section considered; where pplicble, the distnce between two djcent lers o nchors; nd the cross-section with the mximum bending moment. ) Single nchored sheet pile wlls, or sections bove the top nchor ler /below the bottom nchor ler mximum moment or Ex x : β ex, 1, 0 x β ex, 1.0 β ex,i Ex / mximum moment or x < Ex : interpoltion between ex, i nd ex, 1,0 x Ex / β ex, 1.0 where: x distnce between nchor point nd section with mximum moment (in generl section) Ex reerence length osheet pile ( rom Tb. ) Zone o reduction in bending moment resistnce b) ultiple nchored sheet pile wlls, between djcent nchor lers 1 nd Zone o reduction in bending moment resistnce in the cse o severl lers o o-centre nchors where: distnce between the two djcent lers o nchors ) Extreme cse (lrge distnce): Ex mximum moment or x 1 _< Ex / -zone (1)-: liner interpoltion between ex, 1 & ex, 1,0 mximum moment in zone (): ex, 1,0 mximum moment or x _< Ex / -zone () -: liner interpoltion between ex, & ex, 1,0 11

13 B) Norml cse: Ex Ex / mximum moment or x 1 _< Ex /-zone (1) -: liner interpoltion between ex, 1 & β mximum moment in zone (): liner interpoltion between, 1 &, mximum moment or x _< Ex /-zone () -: liner interpoltion between ex, & + ( 1 β ex, 1 ) (, 1 β ex,1 Ex + ( 1 β ex, ) (, ex, Ex C) Extreme cse (short distnce): < Ex / In ll o generl section: liner interpoltion between ex, 1 & ex, β β 1 ) 1 ) 1

14 Exmple o design Sstem nd ction eects Sstem Results o numericl clcultion (design vlues) It is proposed to nchor ever second double pile. It is proposed to instll horizontl tie rods: smooth brs with threded upset ends, with swivel plte to cter or possible settlements. Intermedite double sheet piles will be bolted to wling consisting o two 00 mm chnnel sections set 160 mm prt. Choice o bolt, tie rod, nd bering plte dimensions Wling: 1, kn/double pile choice: bolt d,5 (no clcultion) choice: plte b /h /t 140 /0 /40 mm /S55JR nchor: 1, kn /double pile choice: tie rod d,0 (no clcultion) choice: plte b /h /t 140 /0 /85 mm /S55JR In this exmple no check is crried out or the bolts nd tie rods. It is ssumed tht the steel grde chosen will withstnd the criticl design orces. 1

15 Bering plte dimension check b b c 14mm 140 mm 0,90 b c 19 mm Bolt bering pltes: h t 0 mm,5 b 50 mm t 6 mm 40 mm mint 40 mm d / 19 mm Tie rod bering pltes: t 85 t 6 mm mm min t 40mm d / 5mm where: 1,0 Check o bolt bering plte in bending With: nd (tpe ): d, 5 " , 0 4 t 4 40 Rd, pl > X 147 ( b φ ) X ( ) kn 461kN φ 60 mm d ' 7 X h d ' mm mm dditionl check: π π 55 ( d φ ) ( ) 149 kn > 461 kn SW ,0 Check o tie rod bering plte in bending With : n s 160 mm nd (Tp D ): d,0 " 4 n n 1 φ 81 mm , 0 ( b φ ) X ( ) kn 9 kn Rd, pl > X ( n 1 ) h + X n 1 t s mm dditionl check: d s ,0 ( b φ ) 50 ( ) 1047 kn > 9 kn 14

16 Determintion o eccentricit ctor Z-Proil: Z6 EI 17,88 Nm / m C nt 15,15 N / m Ground t nchor level: modertel compct snd nchor level: h, 0 m k s 80 N / m EI h i 4 4 1, 7 m 1,75 1, 00 k s α i C k 75 N / m Sm s i ex 1 C 1 + C Check othe resistnce othe Z6 pile to locl orces R ock, Rk ( h + b ) K u ( ),7 759 kn 1 α ex ,6 70 R V, Rk ( h + b ) t (1 + αex ) ( ) 18 (1 + 0,6) 174 kn R tw, Rk h t W (1 + αex ) 0 14 (1 + 0,6) 111 kn 1000 ( R ; R ; R ) min ock, Rk V, Rk tw, Rk kn R Rd, Ex, Z 759 kn 1,0 Sm nt 0,6 Note: This check isvlid or bering pltes or both bolts nd nchors since their dimensions b nd h re the sme. Reduction coeicient ex tnchor point β ex Check o ction eects t nchor point lthough the sheet pile cn be deemed to be clss 1- under EN 199-5, to be on the se side the check is crried out or the elstic moment resistnce. with: 66 1 (1 α ex ) 1 (1 0,6) 0,96 C 9,60 55 Z sheetpile: Z 6 / S 70 GP φ 81 mm Ex (it is ssumed tht the most criticl condition is tht corresponding to the gretest reduction in the sectionl re, t the level o the nchor). W el Net W el Gross r W el 600 (1.0 1, 0,081) 1 cm / m,,, W el 600 cm / m V 94, cm / m V 70 c, Rd β ex, W el, Net 0, knm / m > 19kNm/m ( ) ,0 V Rd V 94, 70 0, kn / m 80 kn/m, 10 1,0 > V β ex ( ) 0, 0 0, 50 V Rd ( ) 15

17 Check o ction eects in generl sections To simpli mtters (with ex, ex, ): 70 c, Rd β ex, W el 0, knm / m < 965 knm/m ,0 With more precise vlue or Ex, : x 6,60m (distnce between tie rod nd section with mximum moment): Ex 6, 0 m x > Ex m,0 β 0, 1, ex 70 c Rd β ex, W el 1, knm / m ,0, > 965kNm/m ( ) Note: With ex, ex, nd tking the plstic moment resistnce, the check would lso be met: _< c, Rd 1088 knm /m>965 knm/m. oreover, ssuming ex, 1,0 the result is even _< c, Rd 11 knm /m>965 knm/m. ront bering plte: 140x0x40 /S55JR Wling: U00 s160 Swivel plte: 160x160x50 /S55JR Tie rod: Bolt: Bering plte: 140x0x85 /S55JR Rer bering plte: 140x0x45 /S55JR Sstem digrm Bibliogrph [1] Exzentrische steinleitung in Z-Bohlen, Endbericht mit Bemessungskonzept, ehrstuhl ür Sthlbu, RWTH chen, November 00 [] Bestimmung der nkerplttenbmessungen bei Spundwndbuwerken, Endbericht, ehrs. ür Sthlbu, RWTH chen, ebrur 004 [] nchorge ctlogue, nker Schroeder, itions [4] Steel Sheet Piling Generl Ctlogue [5] EB, Empehlungen rbeitsusschuss Bugruben [6] DIN 18800, Sthlbuten, Deutsches Institut ür Normung, November 1990 [7] EN199-5, Eurocode : Design o Steel Structures, Prt 5: Piling 16

18 Sheet Piling rcelor Commercil RPS S.à r.l. 66, rue de uxembourg -41 Esch-sur-lzette (uxembourg) Tel x E-mil [email protected] E