Study On Seismic Performance Of RC Mega Frame-glued Laminated Timber High Rise Structure

Modern timber structure buildings has the advantages of green environmental protection,rapid construction and natural habitability.In this paper,a new RC mega frame-glued laminated timber high rise hybrid structure is proposed here,in which the mega-frame structure with higher lateral stiffness is adopted as the super-structure,while the lightweight glued laminated timber(Glulam)structure is used as the sub-structure.Then,numerical analysis was carried out the investigate seismic performances of the new hybrid structure by using nonlinear analysis software-Perform 3D.On this basis,strengthening measures of lateral stiffness resistance and energy dissipation of timber sub-structure were further studied.Finally,reverse-cyclic tests were performed on three glulam braced frame to investigate seismic performance of sub-structure units for a certain practical basis and reference of engineering application of the new high-rise hybrid timber structural system.The main researches and conclusions are as follow:(1)In order to investigate seismic performance of the novel high-rise glulam structural system,a finite element model of super high-rise glulam building based on RC mega frame with regular plane layout is established as a research prototype.Comparative study on the earthquake resistant performances of the structure was carried out,including top story displacement,base shear,story drift and component damage.Results show that overall performances of the whole structure meet the specification requirements under rare earthquake actions equivalent to 7-degree aseismic fortification.However,under 8-degree rare earthquake actions,an average of 32.74% of the connections between super-structure and sub-structures damaged.The failure of connections results in a large relative lateral displacement between the super-structure and sub-structures.(2)To strengthen timber frame sub-structure,K-braces and medal dampers were equipped.And seismic performances of the structure under strong earthquake actions were investigated through studying top story displacement,base shear and component damage of each sub-structure in the mega-structure.Conclusions are as follows: lateral stiffness of frame with K-braces is enhanced,lateral-drift of sub-structure decreased by 24.8% on average.After installing metal dampers,the top story displacement,base shear force and maximum story drift of sub-structures reduce under strong earthquake actions.The number of the damaged connections between mega and sub-structure decrease by 14%,and damage in braces improves by 71.8%.Therefore,K-braces are effectively protected by metal dampers,RC mega frame-braced timber high rise hybrid structure equipped with metal damper obtains better seismic performances.(3)To further study lateral resistance of glued laminated timber frame structures with K-braces,reverse-cyclic tests were performed on three 1/2-scale one story,one bay glulam braced frame to investigate seismic performance of sub-structure units.Then experimental phenomena,hysteretic curves,skeleton curves,ductility,stiffness degradation and energy dissipation were obtained and studied.Results showed that much fuller hysteresis loop of timber braced frame specimen with metal damper can be found,and the ductility coefficient is 2.68%?19.2% higher than the original K-braces system timber frame.The metal damper can significantly improve seismic damage of timber members existing in the original frame and effectively protect K-braces and timber frame.Therefore,two seismic defense systems,metal damper as the first defense line and timber braced-frame as the second,are formed.