Seismc Performance Of Reinforced Concrete Square Columns Under Near-field Earthquake

In recent years,a series of near-field earthquakes occurred near the city area have caused a large number of casualties and property losses,which makes the special response of near field structures under near-field earthquake pluse attract increasing attention.The existing column tests considering near-fault groud motion are usually constructed on a shake table or carried through pseudo-dynamic tests,which require a extremely high level of test equipment and facilities.Against this backgroud,this study is intended to develop a low-cyclic loading history in the characteristics of nera-fault groud motion pluse,and simulate the effect of ground motion on the seismic behavior of columns with small shear-span ratio through low cyclic.Four large-scale RC columns are designed and tested.In this study,a integrated measurement programme is developed.The diplacement due to flexure,shear and bar slip is separated from total displacement.The differences of hysteretic curve,envelop curve,distribution of transverse stress and strain,strength degradation and ductilties between different loading histories are investigated.The results show that the peak strength,ductility factors and cumulative consumption of energe are barely affected by loading history.The total displacement of columns under horizontal load consists of three parts which are flexured displacement,shear diplacement and bar slip displacement.It’s hard to separate those values from each other during the test,especially the shear displacement.It comes about that is little experiment data about shear displacement and it is really hard to simulate the horizontal load-shear diplacement envelop of columns through test data.The emphasis of theoretical analysis part of this paper is exploring a relatively simple model to simulate the lateral load-shear displacement envelop.Because the value simulated by Modified Compression Field Theory(MCFT) agree well with the curve from tests.It can be said that MCFT is able to accurately simulate the shear behavior of column.Investigating the effects of parameters on horizontal load-shear displacement envelope through MCFT simulation, the model of horizontal load-shear diplacement can finally be obtained by regression analysis.