This thesis presents a numerical study of the influence of varying story strength on the seismic performance of multi-story wood-frame shear wall buildings. In the prior FEMA P695 studies of these buildings, the non-simulated collapse limit-state was exceeded primarily in the first story. This observation raised interest in quantifying the influence of varying strength from story to story on seismic response. In this study, four distributions of strength are used as bounding cases. The Parabolic strength distribution (1) results from the ELF vertical force distribution method in ASCE 7 that assigns forces to each level based on weight and story height. The Triangular strength distribution (2) results from an assumed vertical force distribution that assigns lateral forces based on the seismic weight at each level. The Constant strength distribution (3) results from an assumed vertical force distribution that assigns a concentrated lateral force at the uppermost level based on the total seismic weight of all levels. The Baseline distribution (4) reflects a realistic vertical strength distribution resulting from the ELF vertical force distribution method. The FEMA P695 methodology, which quantifies seismic performance via adjusted collapse margin ratios, is employed in this study. The analytical models include P-Delta effects and utilize the 10-parameter hysteresis CASHEW model. It is observed that the Parabolic strength distribution allows for dissipation of energy over the height of the building, has less collapse risk than other strength distributions studied, and reduces occurrence of concentrated deformations in a single story from the onset of applied lateral force. / MS / Multi-story wood-frame buildings are becoming increasingly common, especially in areas like the western United States. Past earthquakes have shown that multi-story wood-frame buildings that have a soft and weak first story relative to upper stories are vulnerable to collapsing on the first story. This vulnerability has raised interest in understanding how the relative strength of each story of a wood building affects its performance in an earthquake. This thesis studies four strength distribution cases. The first three cases are called the Parabolic, Triangular and Constant strength distributions named after the shape of the building’s story to story strength profile. For example, the Triangular case has the least amount of strength on the top story, which increases linearly in the lower stories down to the first story, which has the greatest strength. The fourth case, called the Baseline case, is based on actual building designs. All four strength distribution cases have the same first story strength. Two evaluation methods are used to test the strength distribution cases. The first, known as a pushover analysis, applies lateral forces to the building until the roof reaches a specified displacement. The second, called an incremental dynamic analysis, subjects the building to increasingly intense earthquakes until a certain amount of displacement is reached in any story. The results of these analyses showed that the Parabolic strength distribution most effectively used the strength available in every story of the building to delay the onset of collapse and to distribute the location of the collapse story.

A nonlinear automated parameter fitted analytical model that numerically predicts the load-displacement response of wood frame shear walls subjected to static monotonic loading with and without vertical load is presented. This analytical model referred to as Analytical Model of wood frame SHEar walls subjected to Vertical load (AMSHEV) is based on the kinematic behavior of wood frame shear walls and captures significant characteristics observed from experimental testing through appropriate modeling of three failure mechanisms that can occur within a shear wall under static monotonic load: 1) failure of sheathing-to-framing connectors, 2) failure of vertical studs, and 3) uplift of end studs from bottom sill. Previous models have not accounted for these failure mechanisms as well as the inclusion of vertical load, which has shown to reveal beneficial effects such as increasing the ultimate load capacity and limiting uplift of the wall as noted in experimental tests. Results from the proposed numerical model capture these effects within 7% error of experimental test data even when different magnitudes of vertical load are applied to predict the ultimate load capacity of wood frame shear walls.