Load-Duration Behavior of Wood Connections

摘要

The time-effect factors lambda, used in design to account for the load-duration effect were developed through long-term testing of wood members in flexure, yet they are applied to wood connections as well. This study examines time-effect factors for steel-doweled wood connections. In this study, long-term tests were performed on small-scale wood connection specimens, and the resulting time-to-failure data were used to calibrate two cumulative damage (CD) models. A numerical approach was developed for calibrating existing CD models to the test data. Step load tests also were performed on full-scale bolted connection specimens and the results were compared to the results predicted by the CD models fit to the long-term data. The calibrated CD models were then used in a relatively simple procedure to determine an approximate lambda for steel-doweled wood connections ASCE-16 stipulates a lambda of 0.80 for both snow load and occupancy live load. The best fitting models for the long-term test data produced 7 and 14 day lambda's, representative of live and snow load, respectively, between 0.68 and 0.70 for the CD model used in the United States code development and 0.74-0.78 for a model used in Canada. The models which fit step-load test results the best produced a range of 0.86-0.88.