Damage Assessment of Mechanical Performance of Seismic Isolation Rubber Bearings
During rare and very rare earthquakes,bolted seismic isolation rubber bearings may buckle or destabilize as a result of lo-calized rubber damage.The mechanical properties of such bearings are strongly influenced by the physical properties of their constituent materials-steel and rubber.The characteristics of rubber include low modulus,high ductility,super elasticity,and weak compressibility.The results of analytical solution and experimental nonlinear response show that when the horizontal force is small,the maximum and average shear strain under pure compression of the bearing is large,and with the increase of the horizontal force,the maximum and average shear strain under pure shear and the average shear strain in bending increase significantly,therefore,when evaluating the maximum and average shear strain of the bearing,the combined effects of compression,shear and bending effects have to be taken into account at the same time.In addition,the maximum shear strain limits in the U.S.code can be used as a reference,and the nominal compressive strains in the U.K.code are on the large side.Volume expansion of the rubber in the bearing may cause internal rupture;therefore,accurate determination of the shear modulus and shear strain of seismic isolation bearings under large strains and high axial pressures is important for describing their mechanical behavior and local tensile and compressive stresses,as well as for predicting internal damage and destruction.
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