Research On The Designing Method Of Hinge-supported Truss With Buckling Restrained Braces At Base-Hinged Frame System

Industrialized construction is an irreversible development trend of the construction industry in the future,in which China has made certain progress in recent years.However,the low degree of standardized construction and stagnating productivity still hinder the all-round development of industrialized construction.In the use of traditional frame structures,we need to consider the combined effect of horizontal and vertical loads,as well as complex stress,which are unfavorable for the standardization and modularization of components,the weight reduction of components,and field installation.Therefore,to meet the development needs of the construction industry,this paper adopted a new separate bearing system,that is,a Hinge-Supported Truss with Buckling Restrained Braces(BRBs)in Base(HTBB)-Hinged Wall system.The structure bears horizontal loads and controls its deformation pattern through hinged trusses with BRBs at its bottom,and bears gravity loads with hinged walls.The use of such a structural system can unify the stress conditions for pillars and facilitate the standardized and modularized production of components;HTBBs,with excellent performance and structural damages concentrated in BRBs,can be replaced easily and quickly after an earthquake to restore the normal use of a building.This paper analyzed the performance of the structural system and presented a design method based on the response spectrum,results of which were verified through a vibration table test and a numerical simulation.Specific research content and results are listed below:(1)The Hinge-Supported Truss with BRBs in Base structural system was described in terms of its composition and working pattern,and in the context of real projects,a nonlinear analysis was conducted on the structure in a finite element model built with SAP2000.Results show that the structure has inter-story displacement angles that meet standard requirements and relatively even inter-story displacements,the deformation pattern of which is controlled with the introduction of HTBBs,to avoid the occurrence of concentrated plastic damages.Moreover,the structure with BRBs can provide lateral rigidity in small earthquakes and a good hysteretic dissipation capacity in large earthquakes.As there was a considerate increment in the internal force of hinged trusses after BRBs yielded,internal force responses of the structure after yielding were studied,to present a Seismic Intensity Superposition Method.In accordance with the Code for Seismic Design of Buildings of China,a design method based on the elastic response spectrum was presented,to divide the structure into ESCS and PHCS and then conduct a spectral analysis and superposition,the results of which show that the design method can contain the axial force generated by most seismic waves,so is of great value to engineering application.(2)The prototype structure was scaled for the seismic simulated vibration table test,and according to test requirements,basic parameters were determined,the similarity ratio of this test was deduced,and artificial added mass needed was calculated.Components were selected and laid out in the test model structure,and key nodes and BRBs were mainly designed.As required,3 seismic waves were selected and their loading sequence and working conditions were determined.Acceleration sensors,displacement sensors and strain gauges were reasonably arranged.(3)According to the vibration table test,the test data of the HTBB-Hinged Wall structural system was analyzed.No obvious damage to the structure was observed in the test,which suggested that upper hinged trusses retained elasticity.It also proves that the design method adopted in this paper is safe and reliable.Through white noise scanning,it was found that the frequency of the structure did not change obviously in small earthquakes,but decreased after moderate earthquakes,with increases in the damping ratio,which meant that BRBs started hysteretic energy dissipation to protect the main structure.The maximum value of the acceleration amplification coefficient reduced with the increase of PGA and increased with the rise of floors.The maximum horizontal displacement expanded with the increase of PGA and the rise of floors,and the inter-story displacement angle also met relevant restrictions.The structural internal force also grew with the increase of PGA,but obviously slowly after BRBs yielded.(4)A finite element model was built with SAP2000,to which seismic waves actually output by the vibration table were input as loads.The maximum values of horizontal displacements,internal force responses,and the BRB axial force were basically consistent with the trend of test results,though slightly different in values.The differences might result from the effect of ambient noises.