| The principle of frictional energy dissipation has many uses.In modern building structures,it is used to control the seismic response of structures and to install frictional dampers in some key parts of structures(such as joints,braces,shear walls,etc.).Then the energy input into structures can be dissipated by the frictional hysteretic deformation generated by dampers,so as to reduce the seismic response of main structures and avoid the seismic action of structures.Damage or collapse occurs below,which endangers the safety of human life and property.From the study of friction dampers at home and abroad,it can be seen that friction damper is an effective energy dissipation absorber for structures.There are many types of friction dampers,such as Pall friction dampers and energy dissipating restraint.Rotational friction damper is a new type of friction damper.Its connection mode is simple and changeable.It can be changed according to building requirements.It has simple cost and stable friction force.At present,there are few studies on rotational friction dampers in China,and the hysteretic performance of rotational friction dampers is not thorough enough,so it is difficult to popularize the application of rotational friction dampers.In this paper,experimental study and finite element numerical simulation analysis of rotational friction dampers are carried out.The main research contents include:(1)By changing the friction material,the pre-tightening force of high-strength bolts and the number of elements of rotational friction dampers,six specimens of rotational friction dampers were designed.Static repeated loading was carried out on the specimens.The experimental phenomena of six specimens were analyzed.The rotational friction under different parameters of friction material,pre-tightening force of high-strength bolts and the number of elements was studied.Hysteretic performance of friction damper.The experimental results show that:? the friction phenomena of different friction materials are different,and the asbestos-free organic friction materials are mainly adsorption phenomena;the friction materials of Al-Mg alloy and CuZn alloy are mainly plough groove phenomena and stress hardening phenomena;? the hysteresis curves of the specimens are rectangular and full,showing good energy dissipation capacity and idealrigidity-plasticity property.Among the three friction materials,Al-Mg alloy has the largest friction force,followed by Cu-Zn alloy,and asbestos-free organic matter has the smallest friction force.? The loss of pre-tightening force of high-strength bolts in rotational friction dampers is related to the magnitude of initial pre-tightening force of high-strength bolts and friction materials.? Energy dissipation capacity of rotational friction damper: Al-Mg alloy is better than Cu-Zn alloy and asbestos-free organic matter.? The asbestos-free organic materials have excellent stability of friction coefficient,which is about 0.15.The average friction coefficient of Al-Mg alloys is slightly higher than that of Cu-Zn alloys,which are all greater than 0.3.(2)Based on ABAQUS finite element software,the finite element model of six speci mens was established according to the standard size of 1:1.After comparing the test resu lts with the finite element analysis results,it was found that:? The stress of the finite ele ment model mainly distributes in the contact area between the steel plate and the friction plate,and there is partial stress diffusion along the length direction of the steel plate.The maximum stress values in the six finite element models are far less than the design value s of yield strength of materials,which indicates that the finite element model is in an el astic state and is basically consistent with that of the test specimens without obvious plas tic deformation.It shows that the stress distribution obtained by the finite element analysi s is consistent with the test results.? The finite element model agrees well with the exper imental hysteretic curve,and the finite element model can better reflect the hysteretic per formance of rotational friction damper.At the same time,the test results also verify the r eliability of the finite element model.(3)Based on the finite element model verified by experiments,the parameters of rotational friction damper are optimized.A total of 17 finite element models are established.The 17 finite element models are divided into three groups.The effects of arm length,initial angle and pretightening force of high-strength bolts on the performance of rotational friction damper are mainly considered.By changing the number of components and splicing mode of rotational friction dampers,two kinds of deformed rotational friction dampers are proposed,and two finite element models of deformed rotational friction dampers are established.The performance characteristics of three different types of rotational friction dampers are compared.The results show that: ?Increasing the arm length will reduce the friction force and energy dissipation capacity of the damper,but it can improve the stability of the friction force in the process of the damper rotation.It is suggested that when the initial angle of the rotational friction damper is set to 90°,the arm length of the damper should be between 200 mm and 250 mm.? Increasing the initial angle of the damper can improve the friction force and energy dissipation capacity of the rotational friction damper.In order to make the rotational friction damper possess certain energy dissipation ability and the friction stability in a controllable range,it is suggested that the initial angle of the damper be set between 60°and 100°.? By comparing three different types of rotational friction dampers,it can be seen that the hysteretic performance of cross-shaped rotational friction dampers is the best,followed by rhombic rotational friction dampers and L-shaped rotational friction dampers. |
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