Nonlinear Dynamic Analysis To RC Frame In 0.15g And 0.30g Regions Of Design Basic Ground Motion Acceleration

According to the refined ground motion parameter districted-figure,7.5 and 8.5 regions of earthquake intensity category are added in new seismic design code of China. It is worthy to analyze systemically what is the characteristic in internal force combination or reinforced design to frames of two regions and what is the difference in results while taking 7,8 and 9 regions into account.On the base of codes in 1989,a series of seismic measures are improved in new codes,such as limit of inner-storey drift angle,minimum reinforced rate,column-beam moment magnification coefficient and moment magnification factor at the column base,etc. It is also necessary to verify by nonlinear dynamic analysis whether the measures above are effective and whether the anticipative earthquake-resistance aims can be achievable for frames in 7.5 and 8.5 regions.It begins with designing two representative reinforced concrete public frames according to new codes in this paper,and carries out nonlinear dynamic analysis by inputting ground motions at the intensity of intermediate earthquake and rare earthquake actions. The slab-bars effect on yield strength of beams is involved in analysis. The conclusions are as following:(a) The element dimensions of frames in 7.5 regions are determined mainly by axial compressive ratio. The reinforcements in most columns are dominated by the minimum reinforcement rate. And the element dimensions of frames in 8.5 region are determined by both axial compressive ratio and maximum inner-storey drift angle. The minimum reinforcement rate has little effect on reinforcement in columns.(b) When considering the bars in slab participate in beams against negative flexure,four or six times slab-thickness on each side of web can be defined as the effective flange width of slab by intermediate or rare earthquake actions.(c) There are no plastic hinges in frames of 7.5 regions by intermediate earthquake action. And favorable general seismic capacity behaves in rare earthquake action. The whole structure forms a relatively exhaustive "beam-hinges plastic mechanism ". It demonstrates that the seismic measures in low intensity regions,mainly means minimum reinforcement rate,is effective and even excessive strict.(d) The structure in 8.5 region demonstrates a favorable response under earthquake action and forms a well energy-consuming mechanism. It indicates that the seismic measures to 8.5 region is effective and can achieve anticipative seismic aims.(e) Since the results demonstrate a relatively unfavorable response at column basein 7.5 region structure and in column-tapered of 8.5 region structure,it is necessary to strengthen some involved seismic measures to better the unfavorable response.