Modeling and Seismic Behavior of Nonductile Concrete Frame Structures and Retrofit Implications
Appears on pages(s):
ductility; earthquake-resistant structures; frames; reinforced concrete; renovating; Design
A rational retrofit of a non-ductile RC frame structure requires an assessment of its seismic behavior as limited by the strength and ductility capacity of its critical regions. From this assessment, the critical regions can be prioritized for retrofit. This paper presents part of the research at Lehigh University that is investigating the seismic performance of non-ductile RC frame structures and developing retrofit strategies. The paper describes the design of 12-story and three-story prototype non-ductile RC frame structures, modeling of these structures for inelastic static analyses, their seismic behavior as obtained from these analyses, and the implications of this behavior on their retrofit. The seismic behavior of the prototype structures was controlled by the non-ductile behavior of their critical regions. Critical column end regions must be retrofit to increase the global ductility capacity. However, such a retrofit would not significantly increase the base shear capacity of the 12-story structure; pullout regions at the beam-column joints must be retrofit to increase the base shear capacity of this structure. Possible non-ductile behavior within the beams is not considered to be critical to the base shear or global ductility capacity of the prototypes. However, if the pullout regions are retrofit to increase their ultimate moment/rotation capacity, the other regions in the beams should be carefully evaluated.