Experiment And Analysis Of Hysteretic Behavior Of Self- Centering Steel Frames With Coupled Beams

The self-centering steel moment resisting frame?SC-MRF?can overcome the shortcomings of large residual deformation after earthquake of the steel moment resisting frame,has a large stiffness before gap opening and good ductility and energy dissipation ability after gap opening,and can avoid field welding of beam-column joints.The SC-MRF has been extensively researched and applied.However,the traditional SC-MRF has the problem that the floor may be easily cracked caused by the beam elongation effect,and the construction complexity increased due to field tension of strands.In this paper,a self-centering steel frame with coupled beams?SC-CBF?is proposed to overcome the former shortcomings,which is improved in the basis of SC-MRF.The hysteretic behavior of SC-CBF is studied in series.The main research contents and conclusions of this paper are as follows:?1?The working mechanism of SC-CBF and its mechanical properties under lateral force are analyzed.The beam elongation effect can be avoided because coupled beams is pined to columns.The friction energy dissipation device consuming energy using the internal displacement of coupled beams.The friction energy dissipation device,the posttensioned system and beam can be integrated prefabricated in the factory.The connection of coupled beams and columns can be done using a conventional assembly process.According to the virtual work principle,superposition principle and force balance equation,the lateral stiffness and critical load formula of SC-CBF are derived.The theoretical model of hysteresis curve of SC-CBF is established and the calculation formula of each parameter in the model is given.?2?The stiffness and strength characteristics of the pined connection in the beam-column joint of SC-CBF are studied.The uniaxial tensile test of pined connection was carried out,and the law of load displacement curve was studied.The initial stiffness formula of pined connection was derived,and the accuracy of the formula was checked by fine finite element analysis.The similarities and differences between the design methods of GB50017,ANSI/AISC 360 and Eurocode-3 on the pined connection are summed up.On the basis of this,the value of the stiffness reduction factor is given:for the pined connection designed according to GB50017,the factor can be used to reduce the initial stiffness to obtain the secant stiffness of the pined connection in common use.Stiffness check should be performed when the pined connection is used in a structure that is sensitive to stiffness.?3?The quasi-static test of SC-CBF under different design parameters is carried out.A single-layer single-span SC-CBF was designed and fabricated.Six test conditions with different initial pre-tension and energy friction were considered.The test results show that the reasonable design of the initial pre-tension and the energy friction can make the SC-CBF have both strong energy dissipation and self-resetting ability.The agreement of the theoretical hysteresis curve in Chapter 2 and the hysteresis curve in experimental result of SC-CBF is good.The model can accurately reflect the macroscopic mechanical properties such as the starting force and lateral stiffness of SC-CBF.?4?The finite element simulation and parametric analysis of single-layer single-span SC-CBF were carried out.The stress distribution of the members in SC-CBF was analyzed by three-dimensional fine model.The parameterized analysis of SC-CBF was carried out by two-dimensional simplified model.The results of finite element analysis show that the members can maintain the elasticity when the interlayer displacement angle of SC-CBF reaches 3%,and the ear plate in pined connection,beam end section and the end plate are the areas with large stress.The influence of 6 design parameters(the beam-column height ratio h/H,beam length to column height ratio L/H,cross-sectional area of prestressed tendon A_pt,pined connection stiffness k_p,initial pre-tension F_pt0 and energy dissipation friction force F_d)to hysteresis performance indexes?such as k₁,starting force F₁ and second stiffness k₂?is large.The stiffness formula and the starting force formula derived in Chapter 2 are highly accurate and can be used to replace the finite element calculation when the error allows.?5?Sensitivity analysis and response surface fitting were performed on the SC-CBF hysteresis performance index.The sensitivity of the SC-CBF's main hysteresis performance index was analyzed by the PDS module of ANSYS program.The approximate function relationship between each hysteresis performance index and related design parameters was fitted by regression analysis.Probability analysis results show that k₁ is mainly affected by L,h and k_p,F₁ is mainly affected by h,F_d and F_pt0,and k₂ is mainly affected by L,A_pt and h.The approximate function can replace the finite element method to solve the values of k₁,F₁,and k₂ when the number of design parameters within the range of random input variables.