The Study Of Seismic Damage Mechanism Of Steel Structure Considering The Effect Of Damage Accumulation

Under strong seismic action, the serious damage and collapse of building are the main reasons causing huge economic losses and casualties. However, in the previous research, the consideration of cumulative damage and failure criterion is not involved in the numerical analysis of building under the earthquake, so it certainly affected the calculation accuracy of seismic response of building.This paper studied the damage mechanism of steel structure under strong seismic action by using the continuum damage mechanics(CDM) and the development of micro-crack theory. The damage induce the reduction of material yield strength and stiffness in macroscopic view, so it can be considered by using the damage factor in the steel constitutive; the damage derives from unrecoverable material deformation, it can be associated with irreversible plastic deformation by the definition of damage evolution equation.The main work and conclusions of this thesis including following points:(1)Based on the existing non-linear continuum damage mechanics and the development of micro-crack theory, the damage factor and failure criteria are introduced to Krieg & Key material constitutive model, which can be used to represent the reduction of steel modulus and strength caused by strong seismic action, LS-DYNA is employed to analyze the dynamic response of a steel column under seismic actions, and the theory of material model is complied as the subroutines. A existing seismic test of steel column is numerically simulated, and the agreement between the numerical results and measured results verified the reliability of the constitutive model with the damage scalar and failure criterion.(2)The steel material is described as the Krieg & Key material constitutive mode, and the damage evolution and the damage mechanics of steel member under strong seismic action are demonstrated in this thesis. The numerical results the consideration of mechanical damage of steel material would significantly reduce the vertical capacity of steel column, and amplify the peak top displacement and residual deformation. The mechanical damage also affects the nonlinear energy-consuming capacity. (3)Three buildings with 3-story, 9-story and 20-story steel frames respectively is numerical modeled, the steel material is described as the Krieg & Key material constitutive mode and the damage evolution and the damage mechanics of steel frame are demonstrated in this thesis. According the results of seismic analysis of these model, it is concluded that for most multi-storied buildings, the most common damage pattern begins with buckling and damage of the steel beams in lower floors, and the columns start to bearing buckling the following phase, which is the underlying reason of the begin of a catastrophic collapse of the whole building...