차량하중 재하위치를 고려한 현수교의 신뢰성 해석

Abstract

현재 세계적으로 장경간 케이블 교량에 대한 기술이 발전함과 동시에 장대 교량의 필요성이 점점 증가하고 있는 추세이지만, 우리나라의 케이블 교량의 구조 신뢰성 해석은 거의 미미한 수준이다. 본 연구는 실제 통용되고 있는 현수교의 주케이블, 보 강형, 행어의 신뢰성 지수를 계산하고 평가하는데 그 목적을 두고 있다. 현수교 신뢰성 해석을 위해 새천년대교(4경간 현수교)를 모델링하였고 구조해석을 수행하였다. 활하중 특히 차량 하중의 재하 위치 변화에 따라 각 부재의 신뢰성 지수가 얼마만큼의 추이를 보이는지 알아보고자 6가지의 차량 하중의 재하 위치를 가정하였다. 구체적으로, 현수교의 신뢰성 지수를 계산함에 있어서 AFOSM(advanced first order second moment)법 특히 Rackwitz-Fiessler 방법으로 신뢰성 지수를 구하였고, 최종적으로 상용 프로그램인 MATLAB을 이용하였다. 또한, 주케이블의 안전율과 신뢰성지수 간의 관계식을 규명하여 기존의 확정론적 설계개념인 안전율(factor of safety)과 신뢰성지수를 통해 구한 확률적 안전율을 비교 검토하였다. 차량 하중의 각 하중 케이스에 대하여 각 요소의 구조해석을 통해 신뢰성 지수를 산정한 결과 단면력이 많이 차이가 나는 경우가 있음에도 불구하고 신뢰성 지수는 예상외로 크게 차이가 나지는 않았다. 각 요소의 신뢰성 지수는 다소 큰 결과값이 도출되었으며, 이는 새천년대교가 어느 정도 과다 설계가 되었다고 판단된다.

| While the technology of multi-span cable bridge has been developed and the necessary of multi-spans bridge has been increased in the world, the structural reliability analysis in my country are rarely developed. This study has a purpose for computing and evaluating common main cables, steel beams, hangers of a suspension bridge. For the reliability analysis of a suspension bridge, New millenium bridge is modeled and the structural analysis of it is performed. As live loads, specially the change of traffic loading location, six kinds of traffic loading location is assumed to know the value of reliability index. Concretely, when the reliability index of a suspension bridge is computed, it is calculated by using AFOSM(advanced first order second moment) and specially, Rackwitz-Fiessler method. Finally, Commercial programme, Matlab is used. In addition, by investigating the relationship between factor of safety and reliability, factor of safety which is the deterministic design model and stochastic factor of safety by reliability index are compared. For the several loading cases of traffic, the reliability index is estimated by analyzing each elements in structures. As a result, there are a lot of differences for the cross-section, however, unexpectedly the differences of reliability index are not large. The reliability index of each elements has a large value and it means New millenium bridge was designed exaggeratingly.; While the technology of multi-span cable bridge has been developed and the necessary of multi-spans bridge has been increased in the world, the structural reliability analysis in my country are rarely developed. This study has a purpose for computing and evaluating common main cables, steel beams, hangers of a suspension bridge. For the reliability analysis of a suspension bridge, New millenium bridge is modeled and the structural analysis of it is performed. As live loads, specially the change of traffic loading location, six kinds of traffic loading location is assumed to know the value of reliability index. Concretely, when the reliability index of a suspension bridge is computed, it is calculated by using AFOSM(advanced first order second moment) and specially, Rackwitz-Fiessler method. Finally, Commercial programme, Matlab is used. In addition, by investigating the relationship between factor of safety and reliability, factor of safety which is the deterministic design model and stochastic factor of safety by reliability index are compared. For the several loading cases of traffic, the reliability index is estimated by analyzing each elements in structures. As a result, there are a lot of differences for the cross-section, however, unexpectedly the differences of reliability index are not large. The reliability index of each elements has a large value and it means New millenium bridge was designed exaggeratingly.