Comparison of ASD and LRFD Codes for Wood Members. III: Connections
Publication: Practice Periodical on Structural Design and Construction
Volume 5, Issue 2
Abstract
A study was conducted to evaluate the two design codes currently in use for the design of mechanical connections subjected to both lateral and withdrawal loading in wood structures. The allowable stress design (ASD) code and the new reliability-based code using the load and resistance factor design (LRFD) format were evaluated to see which offers the greatest efficiency (i.e., economy) with respect to the design of mechanical fasteners. When the allowable dead load plus live load (due to floor occupancy, snow, wind, and seismic activity) combinations were calculated in each format, comparisons revealed that the LRFD code proved to be more economical over a wider range of the two relevant input variables [dead-to-live load ratio (N) and effect of time under load]. When snow or floor live load governed the design, the LRFD format was always optimal. The amount of increase in load-carrying capacity exceeded 40% for floor live load with very small values of N. In the more commonly seen range of load ratios, the magnitude of increased capacity associated with the LRFD format was approximately 10–15%. The LRFD was also more efficient for wind and seismic loading for N < 3 and 4, respectively. For greater N values, the ASD was more advantageous. However, even when N approached 10 (well above the most common applications), the advantage derived from using the ASD format never exceeded 5%.
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Published In
Practice Periodical on Structural Design and Construction
Volume 5 • Issue 2 • May 2000
Pages: 66 - 69
History
Received: Oct 28, 1998
Published online: May 1, 2000
Published in print: May 2000
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