Load sharing and system factors for light-frame wall systems.

摘要

A considerable amount of research has focused on load-sharing and system effects in repetitive-member wood floor systems subject to transverse loading. However, relatively few studies have been conducted to investigate load-sharing and system effects in repetitive-member wall systems which may be subject to combined transverse and gravity (vertical) loading, and which may have different boundary conditions from floors. This research investigates load-sharing and system effects in light-frame wood wall systems and seeks to develop repetitive-member system factors for codified design that rationally account for load sharing and other system effects. These factors are intended for use in the design of individual wall members, much as repetitive-member factors are used in the design of parallel-member floor and roof systems. As part of this research, an analytical model was developed to account for partial composite action, two-way action, and openings in the wall system. The model was validated using experimental test results and was shown to be able to predict reasonably well the response of light-frame wall systems. The model was then incorporated into a Monte Carlo simulation to perform reliability analyses of light-frame wall systems. Since the structural model is complex, and including a time-history analysis within the time-dependent simulation was not computationally practical, the load combination issue was considered separately from the reliability analysis. Sensitivity studies were conducted to investigate how different system parameters affect strength and reliability of light-frame wall systems. The reliability of light-frame wall systems was next evaluated using a portfolio of representative light-frame wall systems designed according to current code provisions. This portfolio approach was also used in evaluating system factors for light-frame wall systems. Thus, two different approaches (a reliability-based approach and a strength-ratio approach) were considered for developing system factors for member-design to account for load sharing, partial composite action and other system effects. Using the strength-ratio approach, a new framework for system factors (i.e., partial system factors) is suggested in which the effects of partial composite action, load sharing, load redistribution and system size (number of members) are treated separately.