跨海箱型梁桥台风极端波浪致灾机理与试验验证

The extreme wave-generated by the typhoon is one of the most dangerous disasters that threaten the safety of the superstructure of coastal and cross-sea bridges. However, the research on this subject is still deficient. This project will investigate the wave action on coastal and cross-sea bridges, especially those new box-girder bridge. The disaster mechanism of the extreme wave action on bridges will be studied by employing the focused wave, which is an efficient approach to simulate the extreme typhoon-generated wave. This project will develop the calculation model of the wave forces acting on the superstructure generated by the extreme wave. Firstly, the second order focused wave will be developed to improve the shortcoming of the linear focused wave in wave spectrum simulation. The input parameters of the focused wave will be determined after the second order focused generation method implement in numerical wave flume and validated in the wave flume. Secondly, the focused wave action on the submerged box-girder bridge will be investigated by the theoretical method basing on the potential flow theory and the numerical model set up basing on the open source codes OpenFOAM. After validated by test data, the effect of the structural configuration, wave overtopping and guardrail on the wave loads will be investigated by the theoretical and numerical model. Finally, the numerical model of focused wave acting on the elevated and semi-submerged box-girder bridge will be set up. The effect of the air trapping and wave overtopping on the wave action will be studied both numerically and experimentally. The calculation method of wave forces acting on cross-sea box-girder bridges will be established based on the above research results. This project will systematically reveal the mechanical mechanism of the extreme typhoon-generated wave action on the cross-sea box-girder bridges, and develop the analysis methodology and design theory of the wave effect of the cross-sea bridge. Therefore, the investigation of this project has important theoretical significance and practical value for the safety of the cross-sea bridge.

台风极端波浪是威胁近海和跨海桥梁上部结构安全的重要灾种之一，而国内外在该方向的研究较为匮乏。本项目针对新建跨海箱型桥梁上部箱梁，利用聚焦波这一台风极端波浪高效模拟方法，开展极端波浪作用下桥梁的致灾机理及波浪力计算方法的研究。首先，针对线性聚焦波波谱模拟不够精确的缺陷，发展二阶聚焦波数值造波及实验室实现方法，确定不同波浪特性聚焦波的造波参数；其次，研究淹没状态箱梁在聚焦波作用下基于势流理论的波浪力计算理论方法以及数值模型，揭示结构构型、越浪和防撞墙对波浪作用的影响机制并进行试验验证；最后，建立悬空和半淹没状态箱梁在聚焦波作用下的多相流数值模型，研究俘获空气和越浪对波浪作用的影响机理。综合上述研究成果，建立跨海箱型梁桥在极端波浪作用下的波浪力计算方法。本研究将系统揭示跨海箱型梁桥台风极端波浪作用的力学机理，发展跨海桥梁的波浪作用分析和设计理论，对保障跨海桥梁安全具有重要的理论意义和实用价值。

台风极端波浪是威胁近海桥梁结构安全的重要灾种之一，目前针对近海桥梁上部结构尤其是箱型主梁受到的台风波浪作用的研究仍较为匮乏。该青年基金项目正是针对近海桥梁箱型主梁受到的台风波浪作用开展研究，首先提出了连续聚焦波这一创新性造波方法，采用多初相位混合的相速度法建立了连续聚焦波造波理论，分别基于线性和高阶造波理论推导了造波机位移控制算法，应用预估-修正方法进一步优化了台风波浪造波模拟方法，该造波方法可以在100s时间内获得6个以上的重复性高达99%以上的大幅值波浪，能够大幅提高结构波浪作用研究的试验及数值模拟效率；针对台风波浪形成发展过程中存在的非线性波-波耦合作用问题，本项目采用多初相位解耦方法，推导了基于波浪水槽实测结果的高阶谐波分离算法，发展了基于谐波系数法的高阶谐波分量估算方法，为波浪-结构耦合作用中的高频波浪力分析计算建立了理论基础。其次，通过对箱型梁桥复杂几何构型进行适当简化，建立了淹没和半淹没状态下近海桥梁上部结构波浪作用水动力模型，通过求解满足自由表面、固体物面和海底边界条件的Laplace或Helmholtz控制方程，利用特征展开匹配算法获得了波浪-结构作用全域速度势函数，基于线性伯努利方程求解得到波浪作用压强场，并沿物面积分得到了结构受到的波浪作用力，通过与已有物理模型试验结果进行对比，验证了解析计算模型的准确性和有效性；基于该水动力模型研究发现，淹没状态桥梁结构受到的波浪力与入射波波幅、桥梁主梁宽高比、吃水深度等因素密切相关，为近海桥梁抗波浪优化设计提供了思路；基于该水动力学模型，研究了在桥梁前侧布置潜式防波堤或海沟对桥梁波浪力的抑制效果。最后，采用项目提出的连续聚焦波模拟台风波浪，开展了波浪水槽箱梁桥模型试验，获得了箱型梁桥波浪力时空分布特征，发现了当考虑台风波浪频谱特征时，箱梁桥波浪力比规则波要大40-50%，提供了跨海桥梁台风波浪作用新的基本认识，基于项目研究成果发展了近海桥梁波浪荷载计算模型。