| In recent years,with the development of housing industrialization in China,the assembled steel structures have been promoted due to their excellent seismic performance,light weight and environmental-friendly performance.However,there are still many problems such as low level of fabrication,lack of standardized application and poor building wall systems,which have restricted the promotion and application of assembled steel structures when it was applied in residential buildings,especially in high-rised buildings.In order to deal with these problems,a new steel structure residential system named assembled special-shaped multi-box column steel braced frame system(AMCSBF)was proposed in this paper.AMCSBF system is composed of steel special-shaped multi-box columns,top-ring and bottom-through-diaphragm joint connecting H-shaped beam,large precast concrete wall panel,concrete composite slabs with steel-bar truss and so on.AMCSBF has the advantages of high level of factory fabrication,less on-site welding,efficient construction and high integration,so it would be a promising residential system.Nevertheless,the research on the seismic performance and design theory for the AMCSBF structures were insufficient,which restricts its promotion and application.Therefore,the key problems of the seismic performance and design theory of AMCSBF structures would be investigated in this paper to provide the theoretical foundation for promotion and application.The main research contents and achievements are as follows:(1)The joint is the key component to transfer the moment in the AMCSBF structures,which has dominant influence on the capacity and seismic performance of the structures.Therefore,based on the principle of strong-joint and weak-component,9 specimens were designed to investigate the seismic behaviour of top-ring and bottom-through-diaphragm joint connecting the special-shaped multi-box column and H-shaped beam under the cyclic loading.The influence of the thickness of column,the height of beam section,the top-ring plate modified with vertical plate,the shape of column cross-section and the RBS beam section configuration were taken into consideration.The failure modes,transfer mechanisms,rotation capacity and energy dissipation of these specimens were analyzed.The experimental results indicated that except the joint characterized with RBS,the positions of break and plastic hinge were occurred at the end of beam for this joint.This type of failure modes included the fracture of the weld between beam and ring plate and the weld between ring plate and column.For the RBS specimens,its failure mode was the fracture at the RBS area.The capacity of the joint was significantly influenced by the height of beam section,and the thickness of column.However,the influence of other parameters can be ignored.The stable hysteretic curve showed that the joint exhibited excellent energy dissipation.In addition,the rotation capacity of this new joint can satisfy the seismic design requirements of the Chinese code for seismic design of building.(2)The finite element modeling(FEM)of joint was developed by ANSYS to simulate the test process.It was validated by the experimental results,and the behavior during the cyclic loading was studied and analyzed,which included the stress distribution and transfer mechanism of ring plate,through-diaphragm plate and panel zone.It can be found that the box directly connected with beam carried the almost all moment transmitted from the beam,while the moment carried by other boxes was quite small and can be ignored.In addition,parametric study were conducted to examine the influence of key parameters on the capacity and seismic behavior.The results showed that the capacity and stiffness of this type joint were influenced by the thickness and overhang length of the ring plate and through-diaphragm plate,the thickness of the column.However,the influence of the axial compression ratio of column was insignificant.The formula was derived to predict the strength of joint based on the yield line theory.Comparing with the test results,FEM,and the Chinese technical specification for steel structure of tall building,it can be found that the proposed formula provides better predictions to test results than the specification does,which means the proposed formula was more reasonable and accurate.Finally,the design method and detailed requirements were presented.(3)The formula to determine the initial stiffness of the top-ring and bottom-throughdiaphragm joint was established according to theoretical analysis and numerical fitting method.The models to calculate the relationship between moment and rotation(M-θ)under the monotonic loading and the cyclic loading were proposed on the basis of the research results above and the FEM results.The relationship of M-θ results calculated by two models were in coincidence with that of FEM.In general,both models can be used for the elastic-plastic analysis of structure.(4)To deal with the connection problem between the large precast concrete wall panel and the assembled steel residential structures,two types of flexible connection were proposed for the cladding wall panel and infill wall panel,respectively.The flexible connection for the cladding wall was under complicated loading and its behavior was analyzed.The design method and parameter values of this connection were given.Moreover,in order to study the influence of precast concrete wall panel on the dynamic characteristics of assembled steel residential structures,field tests of two steel structures using precast concrete wall panel were conducted.It was shown that the periodic reduction coefficient given by Chinese technical specification for steel structure of tall building is relatively large for assembled steel residential structures with large precast concrete wall panel.In order to not underestimated the seismic effect in seismic design of assembled steel residential structure with large precast concrete wall panel,it is suggested that the period reduction coefficient should be taken as 0.7～0.8 for the panel flexibly connected the structure.However,for panels rigidly connected the structure,the large precast concrete wall panel should be modelled as structural component in the structure analysis model.(5)The strength reduction factor R on AMCSBF structures was analyzed by combining the pushover and capacity spectrum method(CSM).The structures were chosen with different heights,and the M-θ relationship model of new joint was incorporated in the structural model.Based on the analysis,the value of strength reduction factor R was suggested to be 3.6 to calculate the seismic force in the design.The modified horizontal seismic coefficient was then suggested based on the proposed R.(6)A high-rise residential project employing the AMCSBF system was given as an engineering case.Design and assembly process of this system were introduced in terms of the structural system and the enclose wall.This case indicated the proposed system had good feasibility and application prospect. |
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