Collapse Modes Of High-rise Irregular Steel Frame Structures Under Strong Earthquakes

In recent years,with the growth of high-rise buildings and large span public buildings,more and more attention has been paid to the collapse of structures.How to accurately reflect the collapse mode of irregular high-rise steel frame structure under earthquake.It has become a subject.In this paper,I analyse the collapse process of irregular high-rise steel frame structure by ANSYS and LS-DYNA software.The main contents and conclusions of this paper are as follows:(1)Through the modal analysis of the irregular high-rise steel frame structure,the first frequency of "with floor" model is 0.63543HZ and "no floor" model first frequency is 0.65971 HZ.The base frequency is small indicating the overall stiffness of the structure is large.The structure meets the irequirements of structural integrity and rationality.The first order vibration modes are dominated by translational motion,which shows that the structure is affected greatly by lateral vibration and the vertical vibration modes are not obvious.(2)Through the nonlinear dynamic analysis of irregular high-rise steel frame structure,the maximum drift of the "with floor" model occurred in the second layer.Under 350gal Elcentro wave,the maximum storey drift is 0.0412m and the maximum drift angl is 1/80.It does not exceed the limit of interlayer displacement angle of 1/50.The "no floor" model the maximum drift occurred in the second layer.Under 350gal Elcentro wave,the maximum storey drift is 0.02m and the maximum drift angl is 1/164.It also does not exceed the limit of interlayer displacement angle of 1/50.The shape of the each layer maximum acceleration curve like "S",and the maximum acceleration appears at the top layer.(3)Through the collapse analysis of irregular high-rise steel frame structure,It can be found that the the bottom column of "with floor" began to fail under the three waves.Under the three kinds of seismic waves,the total number of failure members is 3.47%,3.39%and 3.3%respectively.It can be found that the the bottom column of "no floor" began to fail under the three waves.Under the three kinds of seismic waves,the total number of failure members is 2.75%,3.57%,2.93%respectively.The failure of the bottom column also leads to the overall collapse of the structure,and the collapse mode of the irregular high-rise steel frame structure is defined as the dynamic buckling failure.It can be found the three vertex displacement curve under three waves.The vibration range and the time of structure collapse can be obtained from the structural collapse vertex displacement curve in X and Y direction under the three waves.The time of the structure collapse can be clearly seen from the vertex displacement curve in Z-direction.The three-direction acceleration curve of the structure can be obtained under the three kinds of waves,and the collapse time of the structure can be judged from the curve.