Lateral Load Path Analysis: Practical Methods for Light-Frame Modular Structures

Abstract

The objectives of this study were to use SAP 2 v16 to investigate lateral load paths and system behaviors in a modular, light-frame wood structure by investigating different foundation configurations and to further develop and validate existing modeling techniques for shear walls according to the perforated shear wall method. The modeling methods were validated using full-scale tests conducted by previous researchers on subassemblies and rectangular and L-shaped houses. A main lateral force–resisting system and components and cladding wind loads were applied in perpendicular directions to the exterior walls. Analysis was performed for a series of foundation types to examine the effects on overall and local behaviors. The effectiveness of the different foundation schemes was evaluated. The racking shear stiffness calibration procedures implemented previously for light-framed construction were found to be applicable to modular, light-frame, shear walls also. In addition, anchorage elongation was found to substantially affect the racking shear stiffness of shear walls with aspect ratios within limits similar to those provided by the specific design provisions for wind and seismic design. For regularly shaped modular structures, assumptions that tributary areas of resisting elements for lateral loads were found to produce conservative demands when contributions from the uplift pressures of wind loads were ignored. Thousands of structures such as these have been used throughout the United States in various applications. Because wind loads have been a major contributor to the annual structural damage of light-framed wood structures and methods to evaluate load paths sufficiently are needed, this study is an important development in the design of modular buildings and the subsequent acceptance of them by building code officials.