Dynamically loaded light-frame wood stud walls: experimental verification of an analytical model

Light-frame wood structures may deform well beyond the elastic limit when loaded by dynamic forces such as earthquakes and sea wave impacts. This paper reports the results of an investigation into the response effects of structural modeling assumptions typically made in the design of light-frame wood structures. Two dimensional and three dimensional models based on previous research were developed to simulate such responses and examine the validity of such models. The models utilize the finite-element method and include options of nonlinear connection properties, elastic constitutive laws of wood material, large deformations, contact forces, and inertial forces. The models were subjected to an estimate of the impact load imparted by a rapidly moving sea wave. To validate the models, the results of a wave-channel experiment of a full-scale wall were used wherein the wall was instrumented with reaction load cells, displacement transducers, and strain gauges on plywood sheathing and wood framing. A closed-loop hydraulic system utilizing a time varying loading function generated the wave trains. The resulting reactions, deformations, and strains were recorded as functions of time while high-speed cameras visually recorded the failure modes and wall behavior. Material tests were conducted before and after testing to record both the observed member properties and the localized section properties. Connection tests were conducted to provide the ultimate strengths for input in the finite element model. Reasonable agreement between the experimental and analytical results over the duration of the analysis depended on the model and model assumptions as well as the result of interest. The three dimensional model captured observed failure modes including rigid-body motions after connection failures and may reliably be used to analyze similar nonlinear systems loaded well beyond the elastic limit.