| Under the influence of cumulative plastic deformations,the strength and stiffness of the members or connections of high-rise or super-high-rise steel structures under strong earthquake may degenerate,and the overall performance of structure may even be affected.The existing seismic criterion have good applicability to frequent earthquakes and strong earthquakes with shorter duration of structural response,however there may be some limitations to the seismic design of existing structures,members or connections for long-period ground motions.Long-period ground motions generally refer to far-field ground motions with predominant period of a few seconds to more than ten seconds.They are characterized by low peak acceleration,long duration,and enrichment long-period component.As the high-rise buildings,as well as super-high-rise buildings with long natural period,they will suffer serious damage in the face of earthquake which long-period components are prominent.Under long-period ground motions with the characteristics of long duration,the cumulative plastic deformation capacity of existing high-rise buildings,as well as especially super-high-rise structures is still uncertain.Therefore,it is an important academic subject to discover the cumulative damage degradation behavior of members or connections under long-period ground motions.In this thesis,the three-dimensional finite element model of steel frame beam-column connections in the existing experiments is established by ABAQUS.The Chaboche user subroutine UMAT is written in Fortran language,and the numerical simulation analysis is carried under the corresponding test loading system.The purpose of the analysis is to verify the reasonableness and accuracy of the user material subroutine UMAT.Then the coding subroutine called Chaboche nonlinear kinematic hardening model is used to research the hysteresis performance,the degradation characteristics,the hysteretic energy consumption,and buckling performance by exerting many kinds of loading system with the continued displacement amplitudes,and the aim to determine the damage degradation characteristics of connections under the influence of long-period ground motion action.The main research work and achievements are as follows:1.Chaboche nonlinear kinematic hardening model is established.Based on the related formula of Chaboche model and integral algorithm,the subroutine UMAT of Chaboche with kinematic hardening is written by using secondary development technology of ABAQUS’s user material subroutines.The finite element quasi-static analyses are carried through the corresponding test of non-scallop beam-column connections,and the accuracy of the UMAT material subroutines can be verified.2.The Chaboche mixed nonlinear hardening model(MIX model)makes a contribution in computational accuracy.Based on the traditional Chaboche model,the extension subroutine of mixed hardening model is written.The analysis results are verified through the test of non-scallop beam-column connections,and the results show that the simulation accuracy of the MIX model is better in terms of ultimate bearing capacity.3.The finite element quasi-static analysis of the non-scallop beam-column connections is carried under the cyclic loading systems including large displacement amplitude.In order to research the influence of long-period component under earthquake action,the coding subroutine called Chaboche mixed nonlinear hardening constitutive model is used to analyze the degradation of connections strength and stiffness systematically under different loading systems,as well as the following targets are compared,they are hysteretic behavior,damage degradation characteristics,hysteretic energy dissipation and buckling performance for the 16 loading systems including the continued displacement amplitudes.The results show that the effect degrees of different loading systems are different to the strength or stiffness of connections,and the buckling performance of the connections also changes accordingly,it can be said the changes have certain rules. |
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