Monotonic and cyclic short-term performance of nailed and bolted timber connections

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Virginia Polytechnic Institute and State University


This paper presents the results of testing to determine the appropriateness of the seismic load duration factor and to investigate the possible effect of previous load history from cyclic loading on connection reserve capacity and ductility. The single shear nail and bolt connection types tested represent common connection geometries used in wood construction in the United States. The results of two methods of fully reversing cyclic loading of connections are presented.

The first method was a load-controlled test with the applied cyclic loads acting at specified percentages above current nominal design values. The sets of specimens were then ramped to failure and the results were compared to a monotonic control set of specimens to determine if any reduction in connection capacity or ductility had occurred as a result of the cyclic loading. From the load-controlled cyclic testing, it was found that previous cyclic loading at load levels as high as twice current nominal design loads did not adversely affect connection capacity.

The second cyclic loading method was a displacement-controlled test that involved successive phases at increasing displacement levels. Each phase consisted of a peak displacement, followed by a series of three decay cycles, then by a series of three cycles at the original peak displacement, the third of which is used to determine the stabilized system. The process is repeated at increasing incremental levels of displacement. The phased displacement stabilized load-displacement curve was fit to an equivalent energy elastic-plastic system for determination of connection parameters. Results from the two cyclic test methods, and from monotonic testing, indicate that the current load duration factor for wind and seismic loading is justified.