The Analysis For Lateral Aseismic Deformation Capacity Of A 4-story RC Model Frame

The lateral deformation capacity of structure is a key parameter to evaluate the structural aseismic performance. So the current seismic code (2001) enacted the requirements with regard to the tolerance of elastic inter-story drift (ED in abbr.) and elasto-plastic inter-story drift (EPD in abbr.). Unlike the previous seismic codes (1964,1974 & 1978) without any requirement for ED and EPD, the seismic code (1989) had firstly stipulated the tolerance of 1/450 (or 1/550 for the consideration of filled wall) for ED and that of 1/50 for EPD to satisfy the target of no damage under minor earthquake and no collapse under major earthquake, while the corresponding values in the seismic code (2001) are 1/550 and 1/50 respectively. By reviewing the related reference, it is found that the 1/50 for EPD was reasonable and different view on the tolerance of ED was proposed for seldom usage of 1/550 as ED. According to the principle of proper stiffness for structure, it is not always advantageous to control seismic design by 1/550 for ED tolerance as the possibility of no obvious plastic deformation under major earthquake.The shaking table test of a 4-story large-scale reinforced concrete model frame indicated that the model structure has abundant capacity of lateral seismic deformation. Therefore, simulation for the shaking table test of the model by 3D FEM program is processed here. A series of inelastic dynamic analysis under EL-Centro wave and Shanghai artificial wave with different peak values (from 0.05g to 0.20g) were done. Meanwhile, Pushover Analysis for the model frame was executed as well. The analytical results indicated that the inter-story drift of the model frame reached 1/34 without structural collapse. Though the maximum value of EPD got from the FEM analysis is less than the value of shaking table test, it is shown that the RC model frame has enough lateral seismic deformation capacity. On the other hand, the inter-story drift for the model with slight damage was determined as 1/260 from the numerical calculation, which was some different from 1/550, the tolerance of ED by the seismic code (2001).Based on the above work, it can be concluded that the ED tolerance of 1/550 issome unreasonable while the EPD tolerance of 1/50 can be accepted. Therefore, suggestion is given here that the ED tolerance of 1/550 should not be strictly implemented if the EPD can be proved to strictly meet the tolerance of 1/50 (to guarantee no collapse under major earthquake). Anyway, the ED tolerance of 1/350 should not be exceeded.