为研究沉管隧道在不同地震动频率和输入方向下的地震响应特性,以港珠澳大桥海底沉管隧道为研究对象,首先,基于开源数值计算平台OpenSees,建立了沉管隧道-土层体系二维有限元模型,并根据隧道所处的场地条件,确定各土层的物理和力学参数及输入地震动;然后,根据港珠澳大桥海底沉管隧道场址地震安全评价结果,确定了小震、中震和大震的水平基岩峰值加速度;最后,探究了不同频率和不同方向地震动下海底沉管隧道的地震响应规律。结果表明:(1) 在3种不同方向地震动输入下,双向地震动输入对隧道结构的响应影响最大;(2) 相较于高频丰富的地震动,低频丰富的地震动对隧道结构的影响更大;(3) 隧道结构易损部位主要分布在中墙与顶底板的连接处、加腋处、顶底板及折拱段。
To investigate seismic response characteristics of immersed tunnels under different frequencies and input directions of earthquake ground motions, the underwater immersed tunnel of the Hong Kong-Zhuhai-Macao Bridge was taken as the research object. Firstly, based on the open-source numerical calculation platform OpenSees, a two-dimensional finite element model of the immersed tunnel-ground system was established. According to the site conditions of the tunnel, the physical and mechanical parameters of each soil layer and the input earthquake ground motions were determined. Secondly, based on the seismic safety evaluation results for the underwater immersed tunnel site of the Hong Kong-Zhuhai-Macao Bridge, the horizontal peak accelerations of the bedrock were determined for small, medium, and large earthquakes. Finally, the seismic response characteristic of underwater immersed tunnels under different frequencies and input directions of earthquake ground motion was explored. The computed results indicate that: (1) The bidirectional earthquake ground motions have the greatest impact on the response of tunnel structure for three types of different input directions of earthquake ground motion; (2) Earthquake ground motion with abundant low frequency component has a greater impact on the tunnel structure compared to earthquake ground motion with abundant high frequency component; (3) The vulnerable parts of the tunnel structure are mainly located at the connection between middle wall and top-bottom plates, haunches, top-bottom plates, and folded arch sections.
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