Rationality Review On Failure Mode Of RAC Frame Structures Based On Energy Dissipation Characteristics

The mainly damage phenomenon of RC frame structures observed in WenchuanEarthquake is that plastic hinges were mainly formed in columns rather than beams.This failure mode of RC frame structures is contradict obviously with the code forseismic design. Failure mode is an important factor affecting the structures’ energydissipation capacity, and a reasonable failure mode should have good capacity of energydissipation. This paper is mainly aim to evaluate the energy characteristics of failuremode of RC frame structures.The main content herein is as follows：①Comparing with the time history analysis, this paper will contrast and analyzethe two simplified caculated methods of hysteresis energy which are used extensive.②Combining the proposed failure modes of RC frame structure by domestic andforeign seismic codes with damage phenomenon observed in Wenchuan Earthquake,this paper designs fourteen failure modes of RC frame structure and analyzes thembased energy characteristics.③To evaluate the energy dissipation capability and the energy reserves of failuremodes, this paper put forward the factor of capability in energy dissipation as the energyindex. Based on the nonlinear static analysis and the factor of capability in energydissipation, here evaluates the fourteen failure modes of RC frame structure integrated.Based on the above research, the main conclusions are as follows:①Method A’s equivalent results is satisfy the requirement of accuracy when thestructure is suffered rare earthquake. But the greater the intensity of a earthquake, theworse the accuracy. Method B’s equivalent results is very good and have a more widersuitable scope. For general structures, using two modes usually can get a fair result. Asto high-rise structures, we suggest consider more modes to get the more correct results.②In the failure mode “ends of beams and columns”, beams and bottom pillars arethe main energy-consuming components, bottom stories are the main energy-consumingstories. The greater the intensity of a earthquake, the higher the percentage of energydissipation of columns and top stories.③As for the failure mode “ends of beams”, it has good ductility deformationability、strength and energy dissipation capacity. It’s a reasonable failure mode for RCframe structure. Based on the failure mode “ends of beams”, columns at the bottom all hinged does not significantly increase hysteretic energy of structure while the ductiledeformation, strength, and energy dissipation capacity has significantly dropped.④The failure modes “ends of beams and central cylinders” and “ends of beams”have similar earthquake reaction (value of hysteresis energy, energy dissipationcapacity,ductility deformation ability and etc). Based on the failure mode “ends ofbeams” allows hinges formed in the ends of central cylinders will not affect obviouslythe energy dissipation capacity and ductility deformation ability of structures.⑤With the increase of ground motion intensity, cylindrical hinge mechanism ofenergy dissipation well in beam-hinge mechanism. Cylindrical hinge mechanism,however, has poor ductility deformation capacity and energy dissipation capacity.⑥The factor of capability in energy dissipation is a viable energy dissipationindex which can better reflect the energy dissipation capability and the energy reservesof structures.