Effects of variation in loading protocol on the strength and deformation capacity of ductile reinforced concrete beams

摘要

Understanding the impact of prior earthquake damage on residual capacity is important for postearthquake damage assessment of buildings; however, interpretation of such impact is challenging when based on tests using traditional reversed-cyclic loading protocols. A new loading protocol, consisting of a dynamic earthquake displacement history followed by quasi-static reversed-cyclic loading to failure, is presented as an alternative to traditional simulated seismic loading protocols. Data are analyzed from a set of 12 nominally identical ductile reinforced concrete beams that were tested by using variations of this protocol and traditional reversed-cyclic and monotonic protocols. Differences in the cycle content of the earthquake displacement histories applied to the test specimens allowed for the effects of load history variation below 2.2% drift to be isolated. It is found that such variation had no effect on the beam deformation capacities. The effects of dynamic loading rates are also analyzed and compared against control quasi-static specimens. Relative strength increases due to dynamic loading are found to be more significant at yield than at ultimate. Dynamic loading rates led to modest reductions in the beam deformation capacities, but the presence of causality between these variables remains uncertain.