| The mining of underground resources causes the movement and deformation of the ground surface,and generates additional internal forces and deformation in the ground buildings,resulting in varying degrees of damage and destruction to the buildings.Anti-deformation buildings are an important measure to deal with coal mining under buildings in mining areas.With the widespread use of steel structure buildings,they have been widely used and promoted in areas with surface deformation.The steel frame structure is a type of structural system suitable for ground buildings in mining areas because of the characteristics of environmental protection,good resistance capacity to ground deformation,light weight,high degree of assembly,short construction period,large effective use area,and re-usability,etc.The distribution of coal resources in China is highly overlapped with seismic fortification areas,buildings in mining areas should have not only excellent resistance capacity to ground deformation but also stable seismic performance.The steel frame structure has excellent resistance capacity to ground surface deformation,but its seismic resistance capacity is limited due to low lateral stiffness.Concentrically braced steel frames can improve the seismic resistance capacity of buildings to a certain extent,but concentrically braces have buckling problems under compression.Buckling-restrained braces can effectively avoid the occurrence of buckling,and it is of great practical significance to study whether buckling-restrained braced steel frames can meet the "dual resistance" requirements of earthquake and ground deformation.In this paper,comprehensive use of experimental study,numerical simulation and theoretical analysis to carry out a systematic and comprehensive study on the anti-deformation and seismic performance of steel frames structure with cold-bending channel-angle buckling-restrained braces.At the component level,the performance and values of structural parameters of cold-bending channel-angle buckling-restrained braces were analyzed and the design method of braces was proposed.At the structural system level,the performance of steel frames with cold-bending channel-angle buckling-restrained braces under separate ground deformation,separate earthquake and earthquake-ground deformation combined action was systematically studied,and anti-deformation design suggestions and displacement-based seismic design methods of this structural system were proposed.The main research contents were as follows:(1)A novel buckling-restrained brace was proposed and the pseudo-static test on its seismic performance was carried out.A novel cold-bending channel-angle buckling-restrained brace(CCA-BRB)was proposed,the inner core of which was cruciform cross-section,and the external constraint member was composed of two cold-bending channels and four cold-bending angles via welding.The pseudo-static test of three brace specimens was completed,and the hysteretic performance(hysteresis curve,skeleton curve),mechanical properties(compression strength adjustment factor,secondary stiffness,post-yield ratio),deformation properties(ductility coefficient,cumulative plastic deformation)and energy dissipation performance(energy dissipation coefficient,equivalent viscous damping ratio)were quantitatively analyzed,and the seismic performance and effectiveness of braces were comprehensively evaluated.(2)The influence of structural parameters on the overall performance of CCA-BRBs was studied,and recommended values of structural parameters were given.Numerical models of CCA-BRBs were established using ABAQUS software,the feasibility and accuracy of numerical modeling method were verified by comparing numerical results with pseudo-static test results,and the influence laws of structural parameters such as constraint ratio,gap,width-thickness ratio and initial defect on the overall performance of CCA-BRBs were studied.The recommended values of corresponding parameters were given based on the analysis results.(3)Anti-deformation performance of buckling-restrained braced steel frames under different ground deformations were studied.Through numerical simulation,the change laws of additional internal forces and deformations of buckling-restrained braced steel frames,concentrically braced steel frames and pure steel frames under ground horizontal deformations(horizontal tension and compression)and ground vertical deformations(uneven settlement,positive and negative curvature deformation)were systematically studied,respectively.The anti-deformation mechanism of buckling-restrained braced steel frames were discussed,and the anti-deformation abilities of the three types of structural systems were compared and analyzed,and the recommendations on the selection of structural systems located in different mining areas were given.The analysis results showed that three types of structural systems had excellent anti-deformation performance,additional internal forces were mainly concentrated on the beams and columns of first and second floors,the moment of bottom frame beams could be significantly reduced due to the addition of braces and anti-deformation performance of steel frames could be improved,the change of brace stress was mainly concentrated at the bottom of steel frames,structure's serviceability would be significantly influenced due to obvious horizontal displacements of the three types of structural systems caused by the affects of uneven settlement,and horizontal displacement was an important controlling factor in the structural design.(4)Seismic performance of buckling-restrained braced steel frames under single earthquake action and earthquake-ground deformation interaction was studied.First,the dynamic time history analysis under rare earthquakes was carried out,response change laws of buckling-restrained braced steel frames under rare earthquake action were discussed from the perspective of yield mechanism,seismic mechanism,storey shear force and storey displacement,and compared with concentrically braced steel frames and bare steel frames.Secondly,the incremental dynamic time history analysis of buckling-restrained braced steel frames was carried out,distribution laws of storey shear force and storey displacement under different seismic acceleration peaks and the collaborative working mechanism between buckling-restrained braces and steel frames were studied.Finally,seismic performance of buckling-restrained braced steel frames under the disturbance of ground deformation was studied based on the damage theory,the corresponding seismic performance levels were defined based on the storey drift angle and the improved Park-Ang damage model,respectively,and the storey drift angle or the overall damage index-peak ground acceleration correlation curves of buckling-restrained braced steel frames were proposed under the influence of uneven settlement,and the quantitative evaluation of the influence of ground deformation on the seismic performance of buckling-restrained braced steel frames with different heights and different brace layouts were completed.(5)Design method of CCA-BRBs,anti-deformation design recommendations and seismic design method of buckling-restrained braced steel frames were proposed.First,design method of CCA-BRBs was proposed at two levels from the design of inner core(including length of yield segment,cross-sectional area and dimension)and external constraint member(including gaps,length and cross-sectional dimension),and a design example was given to provide reference for CCA-BRB's design.Secondly,anti-deformation design recommendations of buckling-restrained braced steel frames in mining area were put forward from three levels:layout principles,anti-deformation design and anti-deformation measures.Finally,with the steel frame remaining elastic and non-yielding under rare earthquakes as the design goal,a seismic design method based on the elastic displacement design spectrum of buckling-restrained braced steel frames was proposed.The method took the yield displacement of steel frames as the target displacement and used the equivalent single-degree-freedom elastic displacement design spectrum to determine the target period of buckling-restrained braced steel frames,thereby determining cross-sectional area of yield segment of the inner core,and then completing the CCA-BRB's design according to CCA-BRB design method.The design method was verified by a design example,which provided reference for the design of buckling-restrained braced steel frames in engineering practice.This paper contains 139 graphs,49 tables and 281 references... |
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