Seismic Upgrade of Interior Beam-Column Subassemblages with HPFRC Jackets
J., Shannag, M. . 2005
Simulated seismic load tests on reinforced concrete gravity loaddesigned (GLD) reinforced concrete frames, with interior beam-column (B-C) joints of non-optimal reinforcing details to resist earthquake are described. The interior B-C joint lacked transverse reinforcement, column lap-splices and continuous bottom beam reinforcement. In this investigation ten 1/3-scale interior beam-column subassemblages were subjected to reversed cyclic loading under no axial column load or under low level of axial load. The joints of these subassemblages were typical in geometry and reinforcement detailing to an interior B-C subassemblage of a prototype Jordanian building frame designed before 1970 only for gravity loads. Some of these subassemblages were tested after strengthening using high performance fiber reinforced concrete (HPFRC) 25 mm thick jacket, all around the joint column regions. The test results indicated that the seismic behavior of upgraded specimens was improved substantially compared to reference ones; higher load levels were attained, larger energy dissipation was observed, and slower stiffness degradation was also noted. The upgraded beam-column subassemblages failed as a result of “plastic hinges” in the beams, whereas excessive damage to joint region of the reference specimen lead to failure. Within the range of the axial loads used in this study, the jackets containing hooked steel fibers (HSF) provided a better confinement and more ductility to the joint region compared to the jackets containing brass-coated steel fibers (BCS).
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