| Canton is rich in historical architectural resources,among which there are a large number of ancestral halls.As a result of the long-term erosion of the external environment,a large number of ancestral hall buildings were damaged to varying degrees and they are in urgent need of protection and repair.In the wooden structure,tenon-mortise joints are the key part of the structure and are easy to be damaged,which has a great influence on the mechanical performance of the structure under seismic response.Relying on the self-developed Queti-type dampers,this project carried out non-destructive strengthening of ancient buildings in Caoton to explore the seismic performance before and after strengthening,which aimed to provide theoretical basis and design reference for the restoration of historical heritage.(1)The material properties of merbau wood and butyl rubber were tested,and the manufacture,experimental research and finite element analysis of Queti-type dampers were carried out on the basis of material properties tests.The results show that,the Queti-type dampers are basically in an elastic state in the process of loading,and the generation of hysteretic loop is mainly related to the viscoelasticity of rubber.The heel of the damper farthest from the hinge point is most prone to damage and should be locally strengthened.The finite element analysis of rubber with elastic and viscoelastic materials can better simulate the skeleton curve,failure morphology and stress development of the damper.(2)Two wooden frames with different structures were used to carry out low-cycle reversed loading tests,and then the two specimens were strengthened in situ with Queti-type dampers to continue the low-cycle reversed loading tests.By analyzing and comparing the phenomenon,hysteretic curve,skeleton curve,strength degradation,stiffness degradation and strain characteristics of the two specimens before and after strengthening,the effect of dampers strengthening on the seismic performance of damaged wood structures was studied.The results show that,Queti-type dampers can make up for the initial defects caused by plastic deformation and provide better initial stiffness,and when the tenon-mortise joints begin to close,the stiffness of the joints increases again,which increases the ultimate bearing capacity and energy dissipation capacity of the joints.(3)Based on the finite element analysis of the specimens,the parametric analysis of beam height h,column diameter D and beam tenon width t were carried out on the basis of determining that ABAQUS can effectively simulate the damage effect,hysteretic curve,skeleton curve,failure shape and stress of the specimens.The results show that,The yield moment and ultimate moment of wood structure joints strengthened by Queti-type dampers increase with the increase of beam height h and column diameter D,and the yield moment increases at first and then decreases with the increase of beam tenon width t.When the beam tenon width is about 0.4D,the yield moment of the joints is the largest and the failure form is reasonable.Finally,the moment-rotation relationship of wood structure joints strengthened by dampers was obtained by machine learning algorithm.(4)Based on the force analysis of the semi-structure of the specimen strengthened by damper,the theoretical calculation formula of moment-rotation angle of hoop-tenon joints strengthened by dampers is derived and its correctness is verified.Based on the analysis of the factors affecting the theoretical formula of moment-rotation of joints,it is found that with the increase of beam height h,column diameter D,tenon width t,friction coefficient μ,unilateral extrusion width b and rubber radius a of damper,the ultimate bending moment and initial stiffness of joints also increase.Finally,the theoretical calculation formula of joint is simplified to obtain the mechanical calculation models of double-lines with the characteristic points of yield point and limit point. |
PDF Full Text Request