Seismic Fragility Analysis Of Isolated Frameworks Based On High-dimensional Model Representation Method

Isolation technique is widely recognized as an effective and mature damping control technique and has been widely used around the world. Nowadays, the superstructure of the isolated structures is generally designed by elastic methods. However, it may moves into nonlinear state under strong earthquake action and big deformation will be caused in the isolation bearing, thus leading to the general failure of isolation building, as a result, the study of its fragility and reliability is particularly important. When conducting seismic fragility analysis, the most commonly used method is statistical analysis which is based on the earthquake damage data obtained during the earthquake or Monte Carlo simulation of metamodel. However, these methods need large number of numerical simulation and therefore are time-consuming. This article mainly concerns the fragility analysis of isolated R.C. frame structures based on the combination of HDMR(high-dimensional model representation) approximation functions and Monte Carlo simulations. It saves great time on the prerequisite of guaranteeing the precision of the result.The main contents of this research are as follows:(1) First of all, a six-floor isolated R.C. frame structure is designed according to the current Chinese code. Then a number of three-dimensional finite element models of both the base isolated and inter-story isolated structure are built into SAP2000 software. Modal analysis is then conducted based on the finite element models and the results show that the isolation prolong the vibration period of the superstructure, base-isolated and inter-story isolated isolation frame structure has good capacity of isolating horizontal earthquake actions.(2) The structural damage index and physical parameters of base isolated and inter-story isolated frame structure are determined. Ten ground motion records corresponding to the class II sites of the Chinese seismic design code are selected from the Pacific Earthquake Engineering Research Center.(3) The fragility analysis of the base-isolated R.C. frame structures is conducted using the HDMR method and the results are compared with that of the response surface method. The results show that the seismic fragility curves obtained by these two methods respectively are highly identical and it is reliable to use HDMR method to calculate the earthquake vulnerability curve of base isolated and inter-story isolated R.C frame structure.(4) The fragility analysis of the inter-story isolated structures is also conducted using the HDMR method and the results are compared with that of the base-isolated structures. The results show that two different isolation structures may appear different failure types under special circumstances.