Modeling of restoring force characteristics of rubber bearings under multi-axial loading

基础隔震技术是近年来发展起来的一种减轻地震荷载的技术，自1995年科比大地震后得到了广泛的应用。高阻尼橡胶（HDR）是一种新型材料，它除了具有柔性外，还具有阻尼特性，在日本主要应用于基础隔震支座。本研究建立了高应变率的唯象模型，并通过基础隔震支座在多轴加载条件下的试验对该模型进行了验证。高阻尼橡胶材料尚未成型，其主要应用--高阻尼橡胶支座（HDR）在安装到实际土木结构之前需要进行试验研究。本文研究了高阻尼橡胶材料的本构关系，并对本构关系进行了实验验证。首先，在材料试验的基础上，提出了弹塑性体和超弹性体相结合的高阻尼橡胶本构关系。在这里，特别注意系统地组织橡胶材料的各种材料测试，因为橡胶材料的机械测试的当前标准不足以用于在极端地震事件的情况下预期极其严重的大变形条件的土木结构。然后，（1）通过图像处理空间地测量HDR表面的应变场;（2）通过将所提出的本构关系应用于所测量的应变场，我们可以得到恢复力或HDR。(3)将计算得到的恢复力与实验结果进行比较，验证了所提出的本构关系。利用该模型，可以对HDR的性能进行高精度的数值评估，从而大大减少了抗震设计中的不确定性。

Base-isolation is the recently developed technology to reduce seismic load to civil structures and currently widely used after the experience of 1995 Kobe Earthquake. High Damping Rubber (HDR), which has the damping property in addition to the flexibility, is a new material and has mainly been applied in base-isolated bearings in Japan. In this research, the phenomenological model of HDR is constructed, and this model is verified through the experiment of the base-isolated bearing under multi-axial loading conditions. High damping rubber material has not modeled yet and, thus, its main application, high damping rubber bearings (HDR), need experimental test prior to its installation to actual civil structures. In this research, the constitutive law of high damping rubber material is studied and this constitutive law is verified experimentally. At first, based on the results of the material tests, we proposed the constitutive law of high damping rubber which combines clasto-plastic body and hyper-elastic body. Here, special attention is paid systematically organize various material testing of rubber materials because current standards for mechanical testing of rubber materials are not sufficient for use to civil structures where extremely severe large deformation condition is expected in case of extreme seismic events. Then, (1) strain-field to surface of HDR was measured spatially through the image processing and (2) by applying the proposed constitutive law to the measured strain filed, we could get restoring force or the HDR. (3) Comparing the calculated restoring force with the experiment, we could verify the proposed constitutive law. Using this model, performance evaluation of HDR can be made numerically with high accuracy, which reduces the uncertainty involved in seismic design considerably.