| Steel structure systems are widely used in construction,super high-rise and large-span structures due to their light weight,good seismic performance and high economic benefits.However,under the action of extreme loads such as earthquakes and typhoons,the steel structure system may still be partially damaged or even collapsed eventually.In this process,there are a large number of geometric nonlinearities and material nonlinearities.Therefore,the non-linear steel frame structure Linear analysis is very necessary.In the finite element software ABAQUS,fiber beam elements or shell elements can be used to simulate the nonlinear mechanical behavior of steel frames.However,fiber beam elements cannot simulate the local buckling of members and the damage and degradation of materials.The calculation results have large errors.The calculation accuracy is high and the calculation result is accurate,but it takes a long time and the calculation efficiency is low.Therefore,this article will propose a complete set of nonlinear numerical calculation methods for steel frame structures that can take into account many factors(such as strength and stiffness damage degradation,local buckling,etc.)and have high calculation efficiency,which is the ultimate bearing capacity of steel frame structures.Calculations provide precise analysis tools.The main research contents are as follows:1.Starting from the component level,using the finite element software ABAQUS,the shell element model of the component is established to simulate the hysteretic behavior of180 different slenderness ratios,diameter-thickness ratios and axial compression ratios of round steel pipe components,and to study and explore the slenderness ratio and diameter thickness.The influence of ratio and axial compression ratio on different hysteretic performance parameters of round steel pipe members,and the corresponding regression formula is proposed to predict the hysteretic performance parameters.2.A hysteretic degradation model based on regression formula prediction and artificial neural network prediction is respectively proposed.The hysteretic degradation model is composed of a skeleton curve part,an elastic unloading part and a Bauschinger part.The model considers the degradation of strength and stiffness from the perspective of energy dissipation.Based on these two models,the hysteresis curves of the internal and external components of the sample set were simulated,and the calculation results of the finite element model were compared to verify the accuracy and generalization ability of the hysteretic model.3.A model of plastic hinge plane beam-column element considering damage degradation is proposed,and the corresponding numerical calculation program is developed based on Matlab.The model considers the effect of cyclic strain hardening,the effect of kinematic hardening,and the effect of strength damage degradation.For the geometric nonlinearity of the plane frame structure,the co-rotation coordinate method is used to deal with.The validity and accuracy of the model are verified by comparison with the test results in some documents.Finally,the horizontal ultimate load-bearing capacity and strength degradation characteristics of the multi-layer plane steel frame are calculated using the method proposed in this paper.4.The plastic hinge model is extended to the space steel frame structure for nonlinear analysis,a plastic hinge space beam-column element model considering damage degradation is proposed,and a numerical calculation program is developed based on Matlab.The proposed spatial element plastic hinge model also considers the cyclic strain strengthening effect,the kinematic hardening effect,and the strength damage degradation effect caused by local buckling or stress-strain softening,and the failure judgment criterion of this model is defined based on the joint cumulative plastic displacement.Finally,experiments and calculation examples verify the effectiveness and accuracy of the proposed model. |
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