Realization of rational failure mechanism for the RC frame structure

To improve the seismic performance of RC frame structure under strong earthquake,the effectiveness of the provisions to ensure the "strong-column-weak-beam" failure mechanism in current Chinese seismic design code is examined,and some effective measures to realize rational failure mechanism are studied.Based on the flexibility method on OPENSEE platform,the fiber model can be used to simulate the biaxial bending behavior of columns under variable axial load and the deterioration phase of the structural response.A 6-story regular frame structure located in each fortification intensity region was designed according to the current seismic design code and studied using the nonlinear pushover analysis to investigate the failure mechanism of the structure.The analysis results were compared with the actual structural damage phenomena observed in Wenchuan Earthquake.The minimum requirement of ensuring the plastic hinge formation mostly in beams was discussed.The analysis results indicated that few plastic hinges were developed in the frame structure in the region of seismic fortification intensity 6.In seismic fortification region 7 and 8,plastic hinges were mainly formed in columns and lateral drift mechanism was developed,leading to inadequate seismic resistance of the structure.The plastic hinge formation mostly in beams was only realized in the frame structure located in seismic fortification region 9.It is proposed that increasing the strong column-weak beam coefficient,reducing the axial load ratio and increasing the design seismic force for small earthquake can help realize the expected failure mechanism that plastic hinges are mainly formed in beams.