| Energy dissipation technology is a way of passive seismic control of Engineering structures.The installation of friction dampers in structures is an effective means to reduce seismic response.It has the advantages of obvious energy dissipation effect,convenient fabrication and processing,and economic and environmental protection.Recently,scholars at home and abroad pay more attention to it.In the past 30 years,scholars have done a lot of research on the test,theoretical analysis and design control of various friction dampers.For Pall friction dampers,slotted bolted friction dampers and rotational friction dampers,a lot of researches has been carried out abroad and entered into industrial production and application.At the same time,the field of friction dampers in China is still in the stage of academic research,especially the rotational friction damper.It is still in the stage of numerical simulation and theoretical discussion.In this paper,theoretical analysis,experimental study and finite element simulation of seismic performance of rotating friction dampers and braced structures with friction energy dissipation are carried out.The main research contents and conclusions are as follows:(1)The frictional theoretical calculation formula of L-type,rhombic-type and mutual-type rotational friction dampers are deduced by Coulomb friction formula,and the factors affecting the rotational friction such as the size of dampers,the size of friction discs and the initial angle are analyzed.Based on the knowledge of structural mechanics and small deformation theory,the restoring force of frame with rotational friction dampers is obtained.The results show that:(1)the ratio of the rotational friction force of L-type,rhombic-type and mutual-type rotary friction dampers is 1:2:2.8;(2)the hysteretic curve of mutual-type rotary friction dampers is the most stable,and the instability coefficient is only 1.02;(3)for L-type dampers,the friction force decreases gradually with the increase of the arm length of dampers.The larger the arm length,the smaller the reduction range;(4)Increasing the initial angle,friction increases significantly,but also brings about instability of friction;(5)Increasing the friction pad of internal diameter and external diameter will increase the rotational friction of friction damper,but the effect of increasing friction is not obvious.(2)In order to address the mechanical properties and stability of rotational friction dampers under different friction materials and bolt pretension,nine rotational friction dampers were designed with three different friction materials.The rotational frictional mechanism,hysteresis behavior,friction force and bolt pretension of rotational friction dampers were compared and analyzed.Low cycle cyclic loading tests were carried out.The theoretical analysis of the rotational friction damper is carried out,and obtained the frictional theoretical calculation formula of the rotational friction damper.The restoring force model of the damper is fitted by the rigid-plastic model.The results show that:(1)The frictional effect of metal materials is composed of ploughing effect and adhesive effect,and the main effect of asbestos-free organic matter is adhesive effect;(2)The hysteretic curves of dampers are full and close to rectangular,showing good energy dissipation capability;(3)The frictional force of copper-zinc alloy and aluminum-magnesium alloy friction materials increases gradually,and the frictional force of asbestos-free organic matter friction materials show a downward tendency;(4)The bolt pretension of Al-Mg alloy friction material is relatively stable;(5)The theoretical formula of friction force is in good agreement with the experimental results,which can be used for the design and analysis of dampers;(6)The rigid-plastic model can be applied to restoring force model of dampers made of Cu-Zn alloy and Al-Mg alloy friction materials.(3)Abaqus finite element software is used to simulate the steel frame with rotational friction dampers.Truss element and beam element are used to simulate the braces with different cross-section forms.The validity of the model is verified by comparison with the theoretical analysis results.On this basis,21 variable parameter finite element models are established and the bearing capacity and initial stiffness and yield displacement of the steel frame with rotational friction damper is studied.The results show that:(1)the error between the theoretical value and the horizontal stiffness of the steel frame without damper in Abaqus finite element model is 5.65%;(2)the simulation results of friction energy dissipation braces by beam element and truss element are basically the same,with a difference of about 24%-28% from the theoretical value;(3)the rotational friction damper simulated by AXIAL connection property can achieve the design bolt pretension force and rotational friction force;(4)The initial stiffness of energy dissipation structure with friction damper is only related to the area of support section,and the larger the area of support section,the larger the initial stiffness;(5)Friction energy dissipation braces with different rotational friction force can improve the bearing capacity of the structure,and the magnitude of the increase is linear with the size of friction force,independent of the area of support section;(6)Yield displacement and yield load of friction energy dissipation braces are determined by the area of support section and rotational friction.force to decide together. |
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