隔震橡胶支座力学性能的损伤评估

Damage Assessment of Mechanical Performance of Seismic Isolation Rubber Bearings

在遭遇罕遇和极罕遇地震时,采用螺栓连接的隔震橡胶支座可能会因为局部橡胶损伤而导致整体屈曲或失稳。这种支座的力学性能深受其构成材料-钢和橡胶的物理属性的影响。橡胶的特点包括低模量、高延展性、超弹性以及弱压缩性。通过解析解和试验非线性响应结果表明:当水平力较小时,支座纯压下的最大和平均剪应变较大,随水平力增加,其纯剪下的最大和平均剪应变以及弯曲平均剪应变增加显著,因此,在评估支座最大和平均剪应变时,必须同时考虑压缩、剪切和弯曲效应的综合影响。此外,美国规范中最大剪应变限值可作参考,英国规范的名义压应变偏大。支座中橡胶的体积膨胀可能引起内部破裂,因此,在大应变和高轴压下,准确确定隔震支座的剪切模量和剪应变对于描述其力学行为和局部拉、压应力,以及预测内部损伤和破坏程度具有重要意义。

During rare and very rare earthquakes,bolted seismic isolation rubber bearings may buckle or destabilize as a result of localized 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.