The Numerical Simulation Studies On Seismic Performance Of Wide Coupling Beam With Small Span-to-death Ratio

As the foremost anti-seismic defense in RC seismic wall structures,the bearing capacity and ductility of coupling beam show important meanings to ensure the anti-seismic ability of structures.In the engineering design,problems such as small span-depth ratio(??2.5),shortage of shear capacity,or over-limit of codes usually occur;the basic anti-seismic requirement of "strong shear capacity and weak bending capacity" cannot be satisfied if valid methods are not taken.Wide coupling beam is one of the methods to solve the problems of shortage of shear capacity and over-limit of codes.This paper analyzes the feasibility and anti-seismic ability of wide coupling beam by numerical simulation,and the main work and conclusions are as follow:(1)Based on the calibration method,UStee102 the reinforced bar model developed by Tsinghua University is applied,and the concrete damage plasticity model and parameters are determined through the numerical simulation of the existing test results.(2)By analyzing many specimens of wide coupling beam in different section width and detailing in pseudo-static numerical simulation,the results show that the wide coupling beam is much better than general RC coupling beam in capacity and dissipation,also in the anti-seismic ability and construction convenience.(3)The numerical simulation of parameter analysis is carried out for the factors,such as the span-depth ratio,the section width,detailing and regional confined concrete,that may affect the seismic performance of the beam.The results show that:?Wide coupling beam can effectively solve the problem of insufficient shear strength and over-reinforced situation.?Under the same circumstances,with the increase of cross-height ratio,wide coupling beam tends to reach the mechanics behavior of the frame beam,although the shear capacity has declined,but there is significant improvement in its ductility.? At the same situation,increasing the section width can improve the anti-seismic ability of wide coupling beam.?Compared with general coupling beam,eccentric detailing will decrease the mechanics ability and dissipation of wide coupling beam.(4)Parameterization analysis by using regional confined concrete to improve wide coupling beam shows:?Increasing stirrups in regional confined concrete can improve the ductility and dissipation of coupling beam.?In the condition of the same volumetric stirrup ratio,decreasing the spacing of stirrup is more useful than increasing the diameter of stirrup in shear capacity,ductility and dissipation.(5)Based on the research,this paper gives the suggestions as follow:?When the method of regional constraint is applied to improve the performance of wide coupling beam,the stirrup spacing is an important factor affecting regional constraint.So in the same stirrup rate,fine and dense stirrup to enhance performance of wide beam is more obvious.?When structural measures should be added to the design of wide coupling beam,the shear resistance of the joints of the wide coupling beams and the tensile properties in the shear walls should be strengthened so as to ensure the reliability of the joints.?When the joint connection is guaranteed to work effectively,the increasing in length of detailing can improve the seismic performance of wide coupling beam.Particularly,the longitudinal reinforcement in the section width should ensure anchoring length when the lap length is not enough,and reinforcement of small diameter out of the width should be set in the detailing.?In the engineering,the content of reinforcement,especially for the stirrups in wide coupling beam with small span-depth ratio is less enough,but they are important for the seismic performance.The increase of content of stirrups and using thin and small spacing stirrup with combined stirrups are suggested.