Sources of Nonlinear Deformations in Light Frame Wood Shear Walls

摘要

The wood shear wall deflection formula as specified in the IBC Eq. (23-2) is critical in understanding the diaphragm rigidity, inter-story drift and serviceability issues resulting from excessive drift. The formula has four deflection components which are derived independently and superimposed to get the overall deflection under a given loading. Under static loading a shear wall system acts as a combined unit which is composed of framing, sheathing, nailing, and hold-down connections. As observed in experiments the response of the system under such a loading is non-linear and coupled and hence cannot be simply broken into simpler components as specified in the equation. This paper presents a parametric study of these components for various shear walls. A virtual work based methodology is utilized to uncouple these components under static loading. It is shown that each component contribution is nonlinear and not just the nails as specified in the formula. The nonlinearity arises due to the nature of the problem which is not represented in the simplified formula. It is also found that the simplified formula is conservative for deflection calculation of shear walls but may not be conservative for computing wood diaphragm flexibility.