Research On Seismic Behavior Of The Special-shaped Column Frames Strengthened In The Bottom

Reinforced concrete (RC) frame structure with special-shaped columns (SSC) get widely applied in residential buildings due to its well architectural functions and reasonable structural layouts.At the same time multilayer residence with commercial network on the first floor is widely uesd in small urban because of its social and economic benefits.But masonry structure with frame-shear wall at the bottom is a structure form which is rigid on the top and flexible on the bottom,this goes against to its seismic design.So special-shaped column frames with bottom strengthened measures should be used in multilayer residence with commercial network on the first floor.This structure form can not only remedy the shortcomings of rectangular column frames when it is applied to residence buildings,but also improve the seismic behavior and overcome the underlying weakness when height between first floor is increased.So far theoretical and experimental research on general special-shaped columns are carried systemic and mature.But the research and evaluation of seismic performance on special-shaped column frames strengthened in the first or two floors can not meet the requirements of engineering application.So the paper compared the control effects of underlying weakness between the five cmmon strengthened measures.Two measures, such as special-shaped columns with bottom rectangle column or wide flange special-shaped column are selected for their applicability in multilayer residence with commercial network on the bottom.According to the maximum height and every site conditions of the special-shaped columns in seismic regions of intensity7and8.Analyzing models of Special-shaped column frames strengthened in the first or two floors were built. Firstly, the comparisons of elasto-plastic time-history analysis between bottom strengthened model and general special-shaped model in intensity7were carried on under frequent and rare earthquakes.The results show that special-shaped column frames strengthened in the bottom can overcome underlying weakness. The storey stiffness are distributed more evenly as the strengthened measure is taken in the first or two floors.The adverse effect brought by the float of the weak story could be removed and the seismic behavior of the whole Frame structure could be improved.Then,by increasing the the height of first floor and length-width ratios of column limb from the former model, time-history analysis were carried on the rare earthquakes in intensity8.The optimal height of first floor to overcome underlying weakness and the reasonable storey stiffness ratio between the first and second floor are proposed by the comparison of the analysis results.