Incremental Dynamic Analysis–Based Procedure for the Development of Loading Protocols

Abstract

Seismic assessment is of critical importance for structures in regions where earthquakes are prevalent. Such assessment in terms of determining the inelastic capacity of structures is often performed in laboratories of universities, government, and industry through quasi-static cyclic testing programs. In these programs, selecting an appropriate loading protocol is crucial for achieving an accurate assessment of inelastic capacity. Appropriate loading protocols need to be representative of the seismic demands to which a structural component may be subjected during seismic events. A standard loading protocol available in the literature may not necessarily yield a meaningful response. For the quasi-static cyclic test program, a loading protocol should be developed specifically for the site, structural component, or system. In this study, an incremental dynamic analysis–based approach is introduced to develop component-specific quasi-static cyclic loading protocols, which is illustrated for a single-column-reinforced concrete bridge bent in Vancouver, British Columbia. Here, different target displacement ductility demand levels, that is, 2, 4, and 8, and different sources of earthquakes, that is, crustal, intraplate, and subduction earthquakes, were considered. The number of inelastic cycles and cumulative ductility damage were the primary target demand parameters in the loading protocol development. Conventional loading protocols were found unrealistically more damaging than those proposed for crustal and intraplate earthquakes. The proposed loading protocols for subduction earthquakes were consistent with those developed by other researchers for the same but employed the classical constant ductility design approach to achieve the target displacement ductility levels.