Journal of the Earthquake Engineering Society of Korea (한국지진공학회논문집)

Earthquake Engineering Society of Korea (한국지진공학회)
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A Failure Probability Estimation Method of Nonlinear Bridge Structures using the Non-Gaussian Closure Method

Non-Gaussian Closure 기법을 적용한 비선형 교량 구조계의 파괴확률 추정 기법

  • Published : 2010.02.28
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Abstract

A method is presented for evaluating the seismic failure probability of bridge structures which show a nonlinear hysteretic dynamic behavior. Bridge structures are modeled as a bilinear dynamic system with a single degree of freedom. We regarded that the failure of bridges will occur when the displacement response of a deck level firstly crosses the predefined limit state during a duration of strong motion. For the estimation of the first-crossing probability of a nonlinear structural system excited by earthquake motion, we computed the average frequency of crossings of the limit state. We presented the non-Gaussian closure method for the approximation of the joint probability density function of response and its derivative, which is required for the estimation of the average frequency of crossings. The failure probabilities are estimated according to the various artificial earthquake acceleration sets representing specific seismic characteristics. For the verification of the accuracy and efficiency of presented method, we compared the estimated failure probabilities with the results evaluated from previous methods and the exact values estimated with the crude Monte-Carlo simulation method.

비선형 이력거동을 가지는 교량 구조계에 지진하중이 작용하였을 때 파괴확률을 추정할 수 있는 기법을 제시하였다. 교량 구조계는 지진하중이 작용할 때 이중선형 이력거동을 보이는 단자유도 진동계로서 모델링하였다. 교량의 파괴는 상단의 변위 응답이 지진 지속시간 동안 정해진 한계 상태 값을 최초로 넘어설 때 발생하는 것으로 정의하였다. 지진하중에 대한 비선형 구조계의 최초통과확률을 추정하기 위하여, 단위시간 동안 한계상태를 넘어서는 빈도수를 계산하는 crossing theory를 적용하였다. 단위시간 동안의 한계상태 초과 빈도수 추정을 위하여 필요한, 비선형 구조계의 응답과 응답의 미분값 간의 결합확률밀도함수를 추정하기 위한 기법으로서, Non-Gaussian closure 기법을 제시하였다. 다양한 지반운동 특성을 가지는 다수의 인공지진 가속도 시간이력을 생성하여 교량의 동적 특성에 따른 파괴확률을 추정하였다. 제시된 기법을 사용한 결과 얻어진 파괴확률 값을 crude Monte-Carlo 시뮬레이션을 통하여 얻어진 정해 및 기존의 방법을 적용하여 얻어진 파괴확률 값과 비교함으로써 제시된 파괴확률 추정 기법의 정확성과 효율성을 검증하였다.

Keywords

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