평면 비정형 철골 모멘트골조의 비틀림 설계기준 평가

Abstract

It is generally believed that the eccentricity induced by difference with center of stiffness and mass causes torsional response during strong earthquake. According to ASCE 7-10, the torsional irregular structure is defined as the one that has large torsional responses caused by the eccentricity. The code requires that these structures should be designed abide by the torsional provisions. This study evaluates the influence of torsional provisions on the performance of the designed 3-, 9-story steel moment frame with different eccentricity, taking the collapse probability as performance metric. The collapse probability is computed with respect to the methology in FEMA P695. The results show that torsional irregular building needs more steel weights than regular building needs. This difference occurs in the process of checking the drift limit and the stability coefficient. As eccentricity become larger, the collapse probability of the structures become rather smaller. Especially, the one of torsional irregular structure is much smaller. To make the design reasonable, a new design approach is used. The displacement for checking drift limit is computed using the difference of the deflections of the centers of mass at the top and bottom of the story instead of the largest difference of the deflections of vertically aligned points. The collapse probability of these buildings increases when compared with that of code-designed buildings and satisfy with collapse capacity requirement. |강성과 질량중심의 차이에 의해 발생하는 편심은 지진이 왔을 때 비틀림 응답을 야기한다. ASCE 7-10 은 편심에 의해 큰 비틀림 응답이 발생하는 구조물을 비틀림 비정형 구조물로 정의하고 있다. 그리고 이러한 구조물에 대해서는 정형 구조물과는 다른 기준을 적용하여 설계하도록 규정하고 있다. 본 연구에서는 ASCE 7-10에서 제시한 비틀림 기준을 평가하기 위하여 편심의 크기가 다른 3층, 9층 철골 모멘트골조를 대상으로 설계를 수행하였으며, FEMA P695 에서 제안한 방법론에 따라 붕괴확률을 산정하였다. 설계를 수행한 결과 비틀림 비정형 구조물은 정형 구조물에 비하여 강재량이 많았으며, 이러한 차이는 변위제한과 안정성 계수 검토과정에서 크게 생겼다. 대상 구조물의 붕괴확률은 편심의 크기가 커질수록 오히려 작아졌으며, 특히 비틀림 비정형 구조물의 경우에는 요구 붕괴확률과의 차이가 컸다. 따라서 본 연구에서는 비틀림 비정형 구조물에 대한 합리적인 설계를 수행하기 위하여 변위제한 검토를 수행할 때의 변위를 수직 부재 횡변위의 최대값이 아닌, 질량중심간의 거리로 사용하여 설계를 수행하였다. 해당 구조물에 대하여 붕괴확률을 계산한 결과, 붕괴확률은 기존의 구조물에 비해 증가하였으며 요구 붕괴확률 또한 만족하였다.; It is generally believed that the eccentricity induced by difference with center of stiffness and mass causes torsional response during strong earthquake. According to ASCE 7-10, the torsional irregular structure is defined as the one that has large torsional responses caused by the eccentricity. The code requires that these structures should be designed abide by the torsional provisions. This study evaluates the influence of torsional provisions on the performance of the designed 3-, 9-story steel moment frame with different eccentricity, taking the collapse probability as performance metric. The collapse probability is computed with respect to the methology in FEMA P695. The results show that torsional irregular building needs more steel weights than regular building needs. This difference occurs in the process of checking the drift limit and the stability coefficient. As eccentricity become larger, the collapse probability of the structures become rather smaller. Especially, the one of torsional irregular structure is much smaller. To make the design reasonable, a new design approach is used. The displacement for checking drift limit is computed using the difference of the deflections of the centers of mass at the top and bottom of the story instead of the largest difference of the deflections of vertically aligned points. The collapse probability of these buildings increases when compared with that of code-designed buildings and satisfy with collapse capacity requirement.