KSCE Journal of Civil and Environmental Engineering Research (대한토목학회논문집)

Korean Society of Civil Engeneers (대한토목학회)
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Seismic Behavior of Bridges Considering Ground Motion Spatial Variation

공간적으로 변화하는 입력지진으로 인한 교량의 지진거동특성

  • Received : 2015.01.13
  • Accepted : 2015.06.11
  • Published : 2015.08.01
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Abstract

The ground motions of large dimensional structures such as long span bridges at different stations during an earthquake, are inevitably different, which is known as the ground motion spatial variation effect. There are many causes that may result in the spatial variability in seismic ground motion, e.g., the wave passage effect due to the different arrival times of waves at different locations; the loss of coherency due to seismic waves scattering in the heterogeneous medium of the ground; the site amplification effect owing to different local soil properties. In previous researches, the site amplification effects have not been considered or considered by a single-layered soil model only. In this study, however, the ground motion amplification and filtering effects are evaluated by multi-layered soil model. Spatially varying ground motion at the sites with different number of layers, depths, and soil characteristics are generated and the variation characteristics of ground motion time histories according to the correlation of coherency loss function and soil conditions are evaluated. For the bridge system composed of two unit bridges, seismic behavior characteristics are analyzed using the generated seismic waves as input ground motion. Especially, relative displacement due to coherency loss and site effect which can cause the unseating and pounding between girders are evaluated. As a result, considering the soil conditions of each site are always important and should not be neglected for an accurate structural response analysis.

장대교량과 같이 길이가 긴 다 지점 구조물에서는 각 지점에서의 지반운동은 차이가 난다. 이것은 지반운동의 공간적 변화로 알려져 있다. 지반운동의 공간적 변화는 각각 다른 위치에서의 지진파 도착시간의 차이에 의해 발생하는 파동전파 효과, 이질적인 지반매체에서의 지진파 산란에 의한 일관성손실, 부지의 지반특성에 따른 부지증폭 효과 등의 이유에 의해 발생한다. 기존연구에서는 부지증폭 효과를 고려하지 않거나, 지반을 단층으로 모델링하여 이를 고려하였으나, 본 연구에서는 다층의 지반에 의한 지반운동의 증폭 및 필터링이 구조물의 지진거동에 미치는 영향을 평가하였다. 서로 다른 지층의 수와 깊이 그리고 지반특성을 가지고 있는 부지에서 공간적으로 변화하는 지반운동을 생성하였고, 일관성손실 함수의 상관성 정도와 각 부지의 지반조건에 따른 지반운동의 시간이력의 변화특성을 평가하였다. 또한, 두 개의 단위 교량으로 이루어진 교량시스템을 대상으로 각각의 부지 조건에 맞게끔 생성된 지진파를 입력으로 하는 교량해석을 통해 각 단위교량 및 단위교량 간 지진거동 특성을 비교분석하였다. 특히, 일관성손실과 지반조건이 두 교량 간 충돌 및 낙교를 유발할 수 있는 상대변위에 미치는 영향을 평가하였다. 해석결과 각 부지의 지반조건의 고려는 아주 중요하며 실제 구조해석에서 무시되어서는 안 될 것으로 판단된다.

Keywords

References

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