Sheathing Braced Design of Wall Studs July 2011 Update. for

Transcription

1 Civil Engineering at JOHNS HOPKINS UNIVERSITY Sheathing Braced Design of Wall Studs July 2011 Update for AISI Committee on Framing Standards Design Methods Subcommittee Cleveland, OH

2 overview! Previous findings on sheathed walls in compression! New work on fastener demands! New experiments on sheathed stud in compression + bending

3 Wall Bracing a) All steel b) Sheathed wall (no bridging)

4 Compression testing (full-scale walls)

5 Observed failure modes Bare-Bare: FT OSB-Bare: FT OSB-Gyp: L + D Gyp removed in picture OSB-Gyp: L OSB-OSB: L

6 Full-scale wall tests (P-!) Comparison betw een different boards combination BARE-BARE.txt 1-OSB-BARE.txt 11-GYP-GYP.txt 3-OSB-GYP.txt 9-OSB-OSB.txt 80 load (kip) position (in)

7 Comparison to design methods 1 AB E&!!!F E&!!!& :092:5K20J LC> LC> MEN..= O 4.= 4.= C.<*)I0:.P)+-J?..QER R8:0..( ( 7),5-8*.92:0-123.; - <=5>9? "! &' &! AISI-S Proposed Proposed 1-sided MEN..= O 4.= 4.= C.<*)I0:.P)+-J?..LC> LC>..( ( MEN..= O 4.= 4.= C.<*)I0:.P)+-J?..QER LC>..( ( MEN..= O 4.= 4.= C.<*)I0:.P)+-J?..QER QER..( ( R8:0 QER.<()*+,-? LC> LC>.<()*+,-? QER LC>.<()*+,-? QER QER.<()*+,-? R8:0 QER.<S8**? LC> LC>.<S8**? QER LC>.<S8**? QER QER.<S8**? ' AISI-S100-07!.! "! #! $! %! &!! &"! &#! &$! &%! "!! ()*+,-./

8 Project timeline! Apr 2008 Report on Existing Design Methods Idea for separation of local and diaphragm stiffness! Oct 2008 Completion of walls testing rig, Phase 1 planning Reliability investigation for 2a fastener spacing rule! Apr 2009 Fastener stiffness (Winter) tests completed Single column testing completed! Aug 2009 Majority of full-scale wall tests completed! Feb 2010 Full-scale wall tests completed Strip test demonstrating local vs. diaphragm! July 2010 Design method realized and compared Formulas for k xd, k x!, k y derived Beam-column testing matrix, materials ordered! Feb 2011 Formalization of design method Work on fastener demands! Aug 2011 Final report on sheathed walls in compression! Fall 2011 Test report on sheathed walls in bending and compression! Feb 2011 Project closeout and beginning of ballots on walls $=0

9 Exploring fastener demand/capacity y!" x k y k x k " k x k " k y springs may differ on the two sides

10 Fastener Demands (state of knowledge)! Local buckling! Ignored probably consistent given springs not assumed to help local! Distortional buckling! Ignored problematic, usual amplification does not apply because of postbuckling, could pick an arbitrary rotation limit to get force, note this is primarily the demand on a pull-through failure mode! Global buckling! Hand calc method derived! CUFSM based method with amplification determined! Conservative simplifications possible, lead to overly large forces?! Direct torsion, shear etc.! Ignored for columns to be added for beam-columns method to do this clear! Accumulation! FE modeling underway, more questions than answers with recent findings

11 Fastener Capacity (state of knowledge) Fastener Shear AISI-S says per manufacturer table or test Tension AISI-S says per manufacturer table or test Shear + Tension No AISI provisions, expression for bolts could provide a rational answer Connections Sheathing Assembly Shear o Wood APA 2004 Panel Design Specification provides allowable stresses for plywood and OSB in shear o Gypsum Could GA be used? Bending o Wood APA 2004 Panel Design Specification provides allowable stresses for plywood and OSB in shear these could be converted and used o Gypsum GA provides strength values for gypsum Stud/Track-Fastener-Sheathing o Tilting, Bearing, Edge tear out, Pull-out, Pull-through AISI-S NDS-2005 (Bearing eq. for wood alone) + APA E830D (limited set of values for plywood-to-steel) and Gypsum (?) o Test Stud-Track-Sheathing by Fastener o Addition of steel may strengthens the assembly but fastener may have greater demands!!! Tested capacities of sub-assemblies (Winter test, rotation test, composite test) provide the easiest assembly capacity predictions Mashup with wood and gypsum places many of the capacity calculations outside of AISI and requires the use of NDS, or more often manufacturer and other data Best path forward is not 100% clear to me in our timeframe

12 New modeling exploring fastener demands

13

14 k y k x k " k x k " k y

15 x Pre-peak! k y k x k " k x k " k y Peak!

16 Sum of x fastener force on field stud

17 Analytical model can predict

18 Fastener/Connections State of knowledge!!!!! Empirically we observed that in all tested specimens the member limit states, not the fastener or sheathing limit states controlled (this does not imply sheathing undamaged, but capacities are consistent with member limit states not fastener limit states) Testing conducted for k x and k " (and potentially k y ) include fastenersheathing limit states (screw shear, edge tear out, pull through, etc.) and could be used for fastener-sheathing capacities We have derived expressions for the amplification of demands in global torsion (these are new). Twist amplification takes same form as flexural amplification, but due to distance from shear center can result in higher fastener demands. Implementation involved. These expressions are now verified ABAQUS shell element models, loaded to collapse, provide fastener demands with all the messy nuances. Fastener demands can become large near peak (particularly due to local buckling) but this is ok because we are not asking fasteners to restrict this mode. All the pieces are in place for a design method including fastener demand and capacity simplification is still needed particularly for demand.

19 Key to Proposed Member Design! Sheathing Restraint y!" x k y k x k " k x k " k y springs may differ on the two sides

20 Sheathed Walls Overview of Proposed Specification Changes/Additions (21 Feb 2011) Determine springs to account for sheathing restraint Member Capacity k x k x k y k! " k! " k y k x is determined from k xd and k x! o k xd Diaphragm stiffness! Formula (new S210/211 or S100?)! Material Test for G (e.g., ASTM D ) o k x! Local stiffness k! Test (new TS?)! Lowerbound formula (new S210/211 or S100?) k y x, k y, k "# o Test (ASTM E72?) + Conversion (ASTM-E72? + new S210/211) Test or formula o Lowerbound formula (new S210/211) k! (AISI-S210-10) o Test (modify - AISI S901-08) o Formula (S210/S211) Elastic Buckling DSM AISI-S100 App. 1 (Note, Fixed-Fixed) Global (P cre ) o Formula (new S100 C4 formulas) o CUFSM 3 at KL (DSM Guide/App.1 Comm.) o CUFSM 4 (new App.1 Commentary) o FEM/ABAQUS Distortional P (P crd ) o Formula (S100 C4.2) o CUFSM 3! D boost (new App.1 Commentary) o cr!, P CUFSM 4 crd, P (new App.1 cre Commentary) Formula, o FEM/ABAQUS CUFSM, FEM Local (P cr! ) (ignore springs) o Formula element only (DSM Guide/App.1 Comm.) o Formula with interaction (DSM Guide/App.1 Comm.) o CUFSM 3 or 4 (new App.1 Commentary) Strength DSM AISI-S100 App. 1 Global (P ne ) o Formula (S100 Eq ) Distortional (P nd ) o Formula (S100 Eq ) Local-Global (P n! ) P n!, P nd, P ne o Formula (S100 Eq ) P n =min(p ne, P nd, P n! ) Elastic Buckling Main Spec. AISI-S100 Global (F e ) o Formula (new S100 C4 formulas) o Rational Analysis (see DSM F e =P cre /A g ) Distortional (F d ) o Formula (S100 C4.2) o Rational Analysis (see DSM F d =P crd /A g ) Local (F cr ) o Formula element only (AISI-S100 k s in Ch. B) Strength Main Spec. AISI-S100 F cr, F d, F e Formula, rational analysis Distortional (P n ) o Formula (S100 C4.2) Local-Global (P n ) o P n =A e F n, A e =f(f cr ), F n =f(f e ) (S100 C4.1) P n =min(p n,c4.2, P n,c4.1 ) P n =A e F n, P n =P nd

21 Sheathed Walls Overview of Proposed Specification Changes/Additions (21 Feb 2011) Determine springs to account for sheathing restraint k x k y k! " k x is determined from k xd and k x! o k xd Diaphragm stiffness! Formula (new S210/211 or S100?)! Material Test for G (e.g., ASTM D ) o k x! Local stiffness! Test (new TS?)! Lowerbound formula (new S210/211 or S100?) Member Capacity k x k! " k y k y o Test (ASTM E72?) + Conversion (ASTM-E72? + new S210/211) o Lowerbound formula (new S210/211) k! (AISI-S210-10) o Test (modify - AISI S901-08) o Formula (S210/S211) Elastic Buckling DSM AISI-S100 App. 1 (Note, Fixed-Fixed) Global (P cre ) o Formula (new S100 C4 formulas) o CUFSM 3 at KL (DSM Guide/App.1 Comm.) o CUFSM 4 (new App.1 Commentary) o FEM/ABAQUS Distortional (P crd ) o Formula (S100 C4.2) o CUFSM 3! D boost (new App.1 Commentary) o CUFSM 4 (new App.1 Commentary) o FEM/ABAQUS Local (P cr! ) (ignore springs) o Formula element only (DSM Guide/App.1 Comm.) o Formula with interaction (DSM Guide/App.1 Comm.) o CUFSM 3 or 4 (new App.1 Commentary) Strength DSM AISI-S100 App. 1 Global (P ne ) o Formula (S100 Eq ) Distortional (P nd ) o Formula (S100 Eq ) Local-Global (P n! ) o Formula (S100 Eq ) P n =min(p ne, P nd, P n! ) Elastic Buckling Main Spec. AISI-S100 Global (F e ) o Formula (new S100 C4 formulas) o Rational Analysis (see DSM F e =P cre /A g ) Distortional (F d ) o Formula (S100 C4.2) o Rational Analysis (see DSM F d =P crd /A g ) Local (F cr ) o Formula element only (AISI-S100 k s in Ch. B) Strength Main Spec. AISI-S100 Distortional (P n ) o Formula (S100 C4.2) Local-Global (P n ) o P n =A e F n, A e =f(f cr ), F n =f(f e ) (S100 C4.1) P n =min(p n,c4.2, P n,c4.1 )

22 Member Design Approach - Directions As summarized on the previous slides, general method is:! Analysis-based! Traditional/formulaic! Closed-form! Programmable! Long! Computational/FSM! Simplest to start! Analysis requires modest interpretation! Spring stiffness! Test or formula? An alternative for COFS Prescriptive or other COFS?! Tabled! Fully detailed wall! Full intermediate analysis details provided! Final strength provided This approach may lead to regimes where strength may be simplified. Still need AISI/PMTG input on details to be tabled, not too many details

23 AXIAL + BENDING

24 Test Matrix (Single Sheathed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

25 Experimental Setup

26

27 Specimen Design Fastener Plan Sensor Layout

28 Specimen Detail: End Fixities

29 Specimen Detail: Stud to Track

30 OSB-OSB

31 !"# $$ %&'()**+,-./0 1 2%3 )*#+4"./0 /5+ 6/789& )4+4:;'/5+ 2/6 )*+*"#'/5+ <=%76 ) 4+#4>'68? '3'*4'%&'1 4 2%3 ' 4 *4 ;4 1'2=285&'@./0 /5+A ('%3/%B'B=%6'@./0A ;- ;4 *- *4 -!"# $$ %&'()**+,-./0 '1 2%3 )*#+4"./0 /5+ ' ('%3/%B'B=%6'@./0A ;- ;4 *- *4-6/789& )4+4:; 6/789& 2%9D/58 ' E'D=7/F+'B=%6'@./0A ; *+- * 4+- 2/6 )*+*"# 4 ' 4 4+* 4+; 4+" 4+, '%3/%B'6/C0+'@/5+A * *+- 2/6 'C/68'6/C0+'@/5+A

32 Gypsum-Gypsum

33 !"# $$ %&'()**+,*-./ 0 1%2 )**+34-./ & )#+#,4' )#+33:'.5+ ;<%76 ) #+*=>'68? '2'*#'%&'0 # 1%2 ' # *# "# 0'1<185&'@-./.5+A ('%2.%B'B<%6'@-./A "= "# *= *# =!"# $$ %&'()**+,*-./ '0 1%2 )**+34-./.5+ ' ('%2.%B'B<%6'@-./A "= "# *= *# = 6.789& )#+#, & 1%9D.58 ' E'D<7.F+'B<%6'@-./A " *+= * #+= 1.6 )#+33: # ' # #+* #+" #+4 #+: '%2.%B'6.C/+'@.5+A # # #+= * *+= 1.6 'C.68'6.C/+'@.5+A

34 OSB-Gypsum

35 Gypsum-OSB

36 Bare-OSB OSB-Bare

37 Bare-Bare

38 P-M Space (as of a few days ago!) OO OG GG OO OG or GO GG OB or BO BB Local Only P/P ynom OB BB GG OG GG OO OO OG GO BO OO BB OB GG OG BB OO GG OG M/M ynom

39 Needs! Details on subset of sheathed walls to be Tabled up: Stud, length, spacing, sheathing, fastener, spacing, etc.! Guidance of committee on where best to introduce the fastener stiffness values and the overall methodology (in COFS, in COS, in wall stud? Floor and roof??) How to ballot all this??! Feedback on how to handle fastener capacity issues that begin to have scope outside of current AISI (a smaller detail, but concerning) Conclusions! Design methods for sheathed walls is ready to go for generating ballots and details that the committee can consider! Tabled solutions and completed beam-column tests next meeting (single column tests will be complete, full walls unsure/unlikely, trying to get an unpaid master s student)! Project closeout next meeting