In isolation structures, laminated rubber bearings are widely used. It has the characteristics of low horizontal stiffness and high vertical stiffness, which can prolong the period of the main structure, avoid the excellent period of the earthquake and block the transmission of seismic energy to the upper structure. Coupled with energy dissipation dampers, seismic energy can be effectively dissipated. On the basis of expounding the research progress of laminated rubber bearings, this paper looks forward to the research direction in this field 1 research progress of laminated rubber 1- 1 Haringx theory. The theoretical study of mechanical properties of laminated rubber bearings is generally based on Haringx theory. This theory is based on incompressible elastic body, which is an elastic theory with small deformation and is not suitable for large deformation and buckling. Study on properties of 1-2 laminated rubber Based on Haringx theory, A-N-Gent studied the compression, bending and shear characteristics of infinite strip and circular incompressible elastic layers, and obtained simple linear solutions under the assumptions of small deformation and incompressibility. P-B-Lindly further studied the compression characteristics of linear elastic materials of rigid plates fixed at both ends. C-G-Koh obtained the compressive stiffness of square compressible materials by variable transformation method, which proved that the paraboloid deformation hypothesis accords with the actual situation. M-S- Chalhobe considered the influence of volume compression ratio on compression stiffness, and on this basis, studied the compression performance of rectangular rubber and the influence of steel-rubber bonding in bending state. H-C-Tsai[ 1] deduced the compression stiffness of infinite strip circle and square, and verified it by finite element method. Then, the simplified effective compression stiffness formulas of infinite strip, round and square rubber bonded between rigid plates, the inclined stiffness of rubber, the horizontal displacement of circular rubber bonded between rigid plates under pure bending and the circular, square and infinite strip rubber bonded between rigid plates are derived. 1-3 research on laminated rubber bearing 1-3- 1 rigid stiffened rubber bearing (1) natural rubber bearing. Laminated rubber bearings need to provide enough vertical bearing capacity and bear large horizontal deformation. Therefore, the research on the strength and stiffness of laminated rubber bearings has become the main research content. C-G-Koh[2] studied the square rubber isolation bearing, put forward a viscoelastic model considering P-δ effect, and obtained the steady-state response of the model under sinusoidal horizontal force and constant pressure. M-S- Chalhobe [3] theory analyzes the compression stiffness of circular isolation bearing considering the influence of volume compression ratio. On this basis, M-Iizuka put forward the macro model of finite deformation and large deformation of nonlinear spring under constant pressure and the empirical design formula of isolation bearing [4]. M-C- constantinou [5] studied the compressive stiffness of hollow rubber layer. G-H-Koo[6] proposed a mechanical model, which used the instantaneous observed shear modulus parameter equation to estimate the bearing under the conditions of small deformation and ultimate shear deformation. H-C-Tsai[7] studied the steady-state response of viscoelastic cylindrical model isolation bearing under sinusoidal horizontal force and constant pressure by using separation variable method. As a pressure-bearing component, laminated rubber bearings have also been widely studied. C-W-Roeder[8] studied the stability of rubber bearings under different vertical loads both theoretically and experimentally. C-G-Koh[9] made an experimental study on the stability of bearings. J-F-Stanton[ 10] Based on Haringx theory, the stability of rubber bearings under different vertical loads is studied theoretically and experimentally. S-Nagarajaiah [11] Based on Koh-Kelly theory, a nonlinear calculation model considering large deformation, large rotation angle, shear force and rotational stiffness is proposed. I [12] tested a series of rubber bearings, studied the influence of horizontal displacement on critical load, and evaluated the existing design methods. In addition to theoretical and experimental research, J-C-Simo[ 13] uses finite element method to analyze the horizontal displacement characteristics and stability under different vertical loads. W-Seky[ 14] analyzed the large deformation of laminated rubber bearings by finite element method. (2) Lead rubber bearing. Filling lead core in laminated rubber bearings can improve the damping of laminated rubber bearings, dissipate seismic energy and provide initial stiffness against tiny vibration. R-G-Tyler[ 15] conducted a large deformation experiment on the lead rubber bearing. A-Mori[ 16] made an experimental study on the compression characteristics of NRB and LRB under axial compression, and made a comparative study with codes, Gent, Chalhoub, Kelly and other theories implemented at that time, which proved that the mechanical properties of LRB and NRB were similar, and the lead core had little influence. R-S- Zhanjide [17] studied the characteristics of near-field earthquakes and the optimization of azimuth parameters. By adjusting the yield strength of the bearing, the maximum displacement of the isolated structure can be affected, while the acceleration response of the structure remains unchanged. Based on AASHTO specification, an improved bearing equivalent linearization model is proposed. Compared with the nonlinear model, the effect is good. C-Topkaya[ 19] carried out oblique compression tests on square rubber bearings and studied the size effect. K-L-Ryan[20] obtained through experimental research that when the axial load increases, the vertical stiffness decreases. When large horizontal deformation occurs, the vertical stiffness softens; The yield strength of LRB is related to axial force. On this basis, Ryan proposed a nonlinear model considering the influence of axial compression. M-Takayama[2 1] analyzed the stress-strain law of LRB under different average pressures by finite element method. M-imbo[22] analyzed the influence of S 1 on the stress distribution and stress concentration under axial compression by finite element method. (3) High damping rubber bearing. The high damping rubber bearing is made by adding additives to natural rubber, which makes the bearing have damping characteristics in addition to the horizontal and vertical mechanical characteristics of NRB. J-S-Hwang[23] uses the fractional derivative Kelvin model to establish the calculation model of HDR. The improved Gauss-Newton system identification method is used for comparative study. Subsequently, the application of fractional derivative Maxwell model in HDR [24] and fractional derivative Kelvin model considering the influence of temperature [25] are studied. Y-Ohtori[26] studied the size effect of HDR. D-N-Grant[27] studied the horizontal bi-directional force on a circular HDR, and established a macro model that is not coupled with horizontal displacement. M-Abe[28] made a theoretical and experimental comparative study on square HDR and LRB, and suggested that the coupling effect under three-dimensional force should be considered in the design. 1-3-2 rubber bearing with flexible stiffening plate The traditional laminated rubber bearing adopts steel plate as reinforcing material, and its benefits are obvious because of its excellent mechanical properties. However, this also causes the high cost and self-weight of bearings. In view of this, scholars began to study the mechanical properties of flexible stiffened plate bearings. J-M-Kelly [29] carried out theoretical and experimental research. The research shows that the cost and weight can be reduced by using fiberboard instead of steel plate as the reinforcing plate of laminated rubber bearing. B-Y-Moon and B-S-Kang[30] introduced the design and manufacture of rubber bearing of fiber reinforced plate in detail, and studied the influence of central hole and lead core on rubber bearing of fiber reinforced plate. H-C-Tsai et al. conducted a series of studies on laminated rubber bearings with flexible stiffeners. The research shows that the boundary conditions of flexible stiffening plate will affect the stiffness of bearing; Only by compressing the bearing can the stiffness of the fiber rubber bearing be improved; When the fiberboard is not fully stretched, the pressure and bending moment are nonlinear coupling; The vertical buckling load of fiber reinforced plate bearing is influenced by horizontal force, and it is also smaller than that of linear material reinforced plate bearing. 2. Summarize and prospect the research on the mechanism of laminated rubber bearings, focusing on the strength, stiffness, stability and damping characteristics of bearings: from theoretical analysis to experimental analysis, empirical formula and the application of finite element method; From Haringx theory of ideal elasticity to considering volume compression, material characteristics, loading mode, size effect and temperature effect; From one-dimensional, two-dimensional to three-dimensional analysis; From simply considering uniaxial compression, tension and bending, to biaxial compression, tension and shear, and then to triaxial compression, shear, tension and shear and their combined effects, systematic research has been carried out and fruitful results have been achieved. Due to the complex characteristics of laminated rubber bearing material and structural mechanism, the research of laminated rubber bearing still needs to be further deepened. (1) The mechanical properties of laminated rubber bearings under complex stress state and the influence of correlation of various characteristic states on the mechanical properties of bearings are studied. (2) With the further popularization of isolation technology and the increase of building height, it is necessary to study the mechanical properties of laminated rubber bearings with large diameter and super-large diameter. (3) Combined with the research of laminated rubber bearings with flexible stiffeners, small laminated rubber bearings with light weight, small volume and low cost are developed and popularized, which is convenient for use in small buildings. (4) The ultimate bearing capacity of laminated bearings depends on the mechanical characteristics of internal stiffeners, but there is little research on internal stiffeners, which needs further study. (5) On the basis of in-depth study of various properties of laminated rubber bearings, it is necessary to solve the optimization design problem of laminated rubber bearings. (6) Finite element analysis of laminated rubber bearings. Using finite element analysis can improve the research efficiency, reduce the cost and solve some analysis that cannot be completed by experiments.
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