Sheathing Braced Design of Wall Studs July 2010 Update for AISI Committee on Framing Standards Design Methods Subcommittee Toronto, ON Civil Engineering at JOHNS HOPKINS UNIVERSITY

Overview Performance of sheathed walls Development of design method Current work Work plan and summary

a) Bare wall with bridgingb) Sheathed wall, no bridging track stud bridging board Wall Bracing

Compression testing (full-scale walls)

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

Full-scale wall tests (P-  )

Overview Performance of sheathed walls Development of design method Current work Work plan and summary

a) Bare wall with bridging b) Sheathed wall, no bridging c) Single column d) Spring-column model track stud bridging board e) Springs on the cross-section Sheathed Wall - Idealization

Comparison to design methods AISI-S AISI-S AISI-S Proposed Proposed 1-sided

board Sheathing Restraint - Bracing x minor-axis bending global torsion y major-axis bending  local torsion (distortional buckling)

board Sheathing Restraint - Source x fastener tilting/bearing in series with sheathing diaphragm stiffness y fastener tilting/bearing in series with sheathing bending stiffness  fastener pull-out in series with sheathing bending stiffness

board Sheathing Restraint - Determination x fastener-board test in addition to sheathing diaphragm equation and “APA” values y fastener tilting/bearing in series with sheathing bending stiffness via “APA” values  Fastener-board test (completed) in series with sheathing bending stiffness equation and “APA” values

and Flexural- torsional buckling Weak axis global buckling Local buckling Distortional buckling Sheathing Restraint - Impact One-side sheathing only

Sheathing Restraint - Impact One-side sheathing only

Sheathing Restraint - Prediction One-side sheathing only Or you can go back to the classical methods to find the global buckling load

Sheathing Restraint - Prediction One-side sheathing only Or you can go back to the classical methods to find the global buckling load

Sheathing Restraint - Impact One-side sheathing only pin fix pin fix pin fix

K=0.5 K=1 a) Contact stud and track End conditions (comparison to unsheathed specimens)

Sheathing Restraint - Impact One-side sheathing only pin fix pin fix pin fix k y lowerbound Add bending stiffness of sheathing, but non- composite k y upperbound Fully composite bending stiffness + “Ad 2 ” stiffness Fixed end conditions k x, k , and k y (lowerbound) found to be consistent with tests

Now, considering again all cases… AISI-S AISI-S AISI-S Proposed Proposed 1-sided

Design Method Outline Determine sheathing restraint – x, fastener-stiffness test + equations and “APA” for sheathing – y, equations and “APA” for sheathing or composite test? – , rotation test or COFS table, + eqn’s and APA for sheathing Determine Member Strength –Global, add k x, k y, k  springs to classical equations or FSM, to find F e (main Spec.) P cre (DSM) then launder through the column curve to get F n (main Spec.) P ne (DSM) –Local, ignore spring restraints, determine local-global capacity A e F n (main Spec.) P n (DSM) –Distortional, use k  classical, or k x and k  rational/FSM, to find F d (main Spec. C4.2) P crd (DSM) then launder through the distortional strength curve to get P n (main Spec. C4.2) P nd (DSM) Check Fastener Demands

Overview Performance of sheathed walls Development of design method Current Work Work plan and summary

Modeling (for fastener demands) imperfections…

Example fastener forces 0.5%P n further analysis and comparison with analytical predictions underway

y

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Overview Performance of sheathed walls Development of design method Current Work Work plan and summary

Basic summary of work plan Literature summary –existing methods –existing predictive capabilities Computational modeling –to support testing –to support design method creation Phase 1 testing –8’ wall, single stud type, different sheathing configurations, axial only –Fastener translational stiffness/strength tests –Single column with sheathing tests Phase 2 testing –Axial + bending tests, 8’ wall, final details TBD –Axial + bending single member tests, w/ sheathing Development of new design methods –identify limit states, potential design methodologies, calcs, examples red = added to initial work plan

Basic summary of work products Literature summary –existing methods (summary report, corrections to Simaan and Peköz) –existing predictive capabilities (Mathcad form) Computational modeling –to support testing (CUFSM and ABAQUS) –to support design method creation (r eliability study on 2a, fastener spacing studies, fastener demands in bending due to torsion begun) Phase 1 testing –8’ wall, single stud type, different sheathing, axial only (report and paper posted) –Fastener translational stiffness/strength tests (report and paper posted) –Single column with sheathing tests (report and paper posted ) Phase 2 testing –Axial + bending tests, 8’ wall, final details TBD (materials ordered) –Axial + bending single member tests, w/ sheathing (materials ordered) Development of new design methods –identify limit states, potential design methodologies, calcs, examples red = added to initial work plan blue = comment on work product