Seismic Performance of Gypsum Walls: Experimental Test Program

Seventeen experimental tests were conducted to meet the required research objectives of determining the cost-damage relationship and engineering characteristics of residential gypsum wallboard partition walls. Specimens were 8-foot high and 16-foot long, double-sided with 1/2” gypsum wallboard. Test variables included: fastener type and spacing, loading protocol, top-of-wall boundary condition, method of attaching the wallboard to the top sill, wall opening layout, innovative construction methods, influence of door and floor trim, and repair strategies. Instrumentation measured applied load, lateral deflection at the top of the wall, lateral deflection at the bottom of the wall, shear distortion of the piers, and uplift at the door trimmers.

Findings include a distinct change in strength for walls built with various fastener types and wall penetration layouts. Damage patterns begin with the initiation of cracks at the wall penetrations and cracking of the paint over a few fastener heads, usually initiating at drift levels near 0.25%. Maximum loads are sustained at drifts of approximately 1 to 1.5%. At this point, one of two failure modes initiates. The first failure mode seen was loosening of the wallboard from the framing by pulling fastener heads through the back of the wallboard. The second failure mode included failure of the taped wall joints and racking movement of the individual wallboard panels. Strength degradation may be severe or more gradual for different walls. Monotonic loading protocols closely predict the cyclic force-displacement backbone relationship. The overall behavior and levels of damage appears to be related to the rigidity and geometry of the boundary elements of the wall. Rigid restraint from the intersecting walls appears to significantly increase the lateral strength and stiffness.

Cost-damage relationships appear to be similar to a step-function. The cost of repair seems closely related to the number of tradesmen required for repair work. While a single multi-skilled contractor can repair minor cracking, larger levels of damage may require demolition crews, drywall crews, carpenters and paint crews. Total loss of economic value of the wall appears to occur at drifts of approximately two percent.