Study On The Seismic Behavior Of Prefabricated Frame Steel Structure Considering Soil-Structure Interaction

"13th Five-Year Plan" clearly pointed out that the construction industry should promote green building and green construction technology.The assembly process of steel frame structure can achieve the effect of developing energy saving and environmental protection industry and resolving excess capacity,which is becoming a hot spot in engineering research.The problems of low stiffness and poor integrity of prefabricated steel frame structures have become the priority research contents for academic researchers.However,in the current engineering practice,structure and soil are considered separately,and the influence of the interaction between structure and soil on the structure is not elaborated in detail.In particular,there are widely soft soils distributed in China,and their impact on the seismic performance of prefabricated steel frame structures under earthquakes requires deeper studies.This article is based on the previous studies of the soil-structure interaction(SSI)system.The soil constitutive model is set as ?Drucker-Prager? and the infinite element element is applied as the soil truncation boundary to establish the soft soil foundation model.The double-web-bottom angle steel joint is selected as the semi-rigid node of the prefabricated frame.The stiffness degradation model of the joint is chosen,and the ?Connector?element is used to describe the characteristics of the model.An integral prefabricated steel frame is finally constructed.The soft soil foundation model and the prefabricated steel frame model are combined to create a soft ground-prepared steel frame interaction system(herein referred to as the RR system)and establish a rigid foundation-prepared steel frame interaction system(GR system),soft ground-prefabricated frame interaction system(RG system)and rigid ground-rigid-joint frame interaction system(GG system).Detailed analysis of the four types of systems was conducted to study the changes of dynamic characteristics under SSI effect and structural assembly conditions.Dynamical time history analyses are performed on the four types of systems to reveal the influence of SSI effect.Static elasto-plastic analyses of the four types of systems are carried on to grasp the plasticity development rules and the overall mechanical properties of the structure subjected to the SSI effect and structural assembly.Comparing the results of the four types of systems,it is indicated that the introduction of fabricated nodes in the rigid frame leads to a significant reduction in the structural stiffness,and the natural vibration frequency reduces more than 22%;the structural natural vibration periods between the natural vibration period of rigid ground system and the SSI system are quite different for the first five orders.The vibration modes of the superstructure in rigid foundation systems and SSI systems are also in great difference.Comparing the dynamical time history analysis results of four types of systems,it can be seen that:(1)The SSI effect leads to an increase in the displacement angles between structure layers and the peak values of the peak displacements.The maximum amplification factor reaches 2.02 and 2.01 respectively.The vertex velocity response is uncertain.For the structure vertex acceleration and bottom shear force,the overall performance of the statement is in a decreasing trend,but as the structure height increases,its decreasing trend gradually is weakened.In the 20-story frame,the phenomenon of amplification may be enlarged.(2)The impact of structural assembly on the structural dynamic response is similar to that of the SSI effect.The inter-story displacement angle and the peak displacement of the vertex show an increasing trend.The magnification factor can reach to 2.0 and 2.16.The vertex velocity response is complex and there is no obvious law.The acceleration at the vertex and the total shear at the bottom of the lower structure will tend to shrink,while the increase in shear may occur in mid-rise buildings.(3)When considering the influence of SSI effect and structure assembly simultaneously,the displacement response of the superstructure will be exacerbated,and the reduction effect on the peak acceleration peak and bottom shear peak will be amplified.Comparing the results of the pushover analysis of the four types of systems,it is indicated that both the SSI effect and structural assembly lead to a reduction in the lateral stiffness of the structure,which is reduced by 35.26% and 18.75% respectively,however,it also enlarges the limit displacement of the vertex when the structure appears plastic.The structural assembly and SSI effects have no significant effect on the development mode of the structural plastic hinges,and the plastic regions appear from beam to column and from low to high in order.The simultaneous effects of structural assembly and SSI effects will aggravate the amplifying effect of the two on the structural response.Compared with the GR system only considering the structural assembly and the RG system considering only the SSI effect,the lateral stiffness of the RG system is reduced by 27.42% and 8.90%.When considering the structure's assembly and SSI effects separately,the inter-layer displacement angles of the structures are enlarged to 0.019 and 0.02.When considering the impact of structural assembly and SSI effects,the peak value can reach 0.023.Therefore,considering the structure assembly and the SSI effect will aggravate the structural response,and when both are taken into account,the structure will be in a more unfavorable state.