A STUDY ON VERIFICATION OF SEISMIC SAFETY OF ROAD BRIDGES BY USING ACCELERATION-DISPLACEMENT RESPONSE SPECTRUM

本研究的目的是利用单自由度体系的加速度-位移反应谱（以下简称Sa-Sd谱），建立一种基于力-位移的公路桥梁抗震设计方法。本研究取得的主要结果总结如下1. S_a S_d谱受修正Park-Ang损伤指标D_r值、延性能力μ_u值和恢复力模型的影响。即D_r和μ_u的增大使加速度S_a和位移S_d的谱值增大。双线性模型的S_a和S_d值也比Q-hyst模型的大。S_a值在II型地震中随土层变硬而变大，在I型地震中随土层变软而变大，而S_d值在I型和II型地震中均随土层变软而增大2。利用弹性加速度反应谱S_（要求）屈服强度比R_r和位移延性系数μ_d_3，可以较准确地导出各地震类型和土组的S_a和S_d谱与自振周期T和延性能力μ_u的回归方程<ae>。利用推导出的S_a S_d谱，提出了钢筋混凝土单柱桥墩和门式刚架桥墩基于力-位移的抗震设计方法，并比较了该方法与日本规范延性设计方法在钢筋混凝土单柱桥墩设计结果上的定性差异。结果表明，该方法要求更高的抗侧承载力和更高的延性承载力，比延性设计方法更安全

Objective of this study is to develop a force-displacement-based seismic design method of road bridges by using the acceleration-displacement response spectrum (hereafter referred to as the S_a-S_d spectrum) of SDOF systems. The main results obtained in this study are summarized as follows1. The S_a S_d spectrum is affected by the required value D_r of modified Park-Ang's damage index, and the value of ductility capacity μ_u and restoring force model of a SDOF system. Namely the increasing value of D_r and μ_u makes the spectral values of acceleration S_a and displacement S_d larger. Also the value of S_a and S_d of Bi-linear model becomes larger than that of Q-hyst model. The S_a value also gets larger as the soil becomes harder in Type II earthquake and softer in Type I earthquake, while the value of S_d increases as the soil gets softer in both the Types I and II earthquakes2. Regression equation of the spectra of S_a and S_d for each earthquake Type and soil Group can be derived with relatively high accuracy as the function of natural period T and ductility capacity μ_u by using the spectra of elastic acceleration response S_<ae> required yield strength ratio R_r and displacement ductility factor μ_d3. The force-displacement-based seismic design method for a single-column RC pier and portal rigid frame RC pier is proposed by use of the derived S_a S_d spectrum, and the qualitative difference in the design results of single-column RC piers, between the proposed method and the ductility design method of the Japanese Specifications, is compared. As a result it becomes clear that the proposed method requires more lateral capacity and more ductility capacity, and the proposed method is the safer design than the ductility design method