基于势流理论的跨海桥箱梁斜向波浪荷载作用研究

Effect of Oblique Wave Forces on Box-Girder Superstructure of Sea-Crossing Bridge Based on Potential Flow Theory

为分析斜向波浪对跨海桥箱梁的影响,提出斜向波浪作用下跨海桥箱梁所受波浪荷载的理论计算方法。该方法基于势流理论建立斜向波浪-桥梁作用的数学模型,利用特征展开匹配法及伯努利原理计算箱梁所受的斜向波浪荷载。以平潭海峡公铁大桥为背景,对比分析淹没状态下箱梁的无量纲波浪荷载理论计算值与水槽试验值,验证所提出理论计算方法的准确性,分析波浪入射角和结构几何特征参数对斜向波浪荷载的影响规律。结果表明:所提出的跨海桥箱梁斜向波浪荷载计算方法准确、高效;波浪入射角对箱梁所受波浪荷载有显著影响,由长周期波浪引起的垂直波浪荷载对入射角的变化更为敏感;在斜向波浪作用下,结构的几何特征对箱梁所受水平方向波浪荷载的影响更为显著。在跨海桥箱梁设计时,建议考虑结构尺寸与斜向波浪入射角对波浪荷载的影响,通过结构优化与合理的桥位布置来降低波浪荷载对桥梁上部结构的影响。

In this paper,the effect of oblique wave forces on the box-girder superstructure of the sea-crossing bridge is analyzed and a theoretical calculation method is proposed.The oblique wave forces impacting the superstructure is calculated by a mathematical model developed based on the potential flow theory,using the eigenfunction matching method and Bernoulli′s principle.The Pingtan Straits Rail-cum-Road Bridge is used as an example to verify the effectiveness of the theoretical calculation method presented.The theoretical values of the dimensionless wave forces on the submerged box girder were compared with the flume test values,and the influence law of incident angle and structural geometric parameters on the oblique wave forces was analyzed.The results demonstrate that the presented method to calculate the oblique wave forces impacting the box-girder superstructure of the sea-crossing bridge is practical and effective.The incident angle,to an obvious extent,dictates the strength of the wave forces on the superstructure,and the vertical wave loads induced by long-period waves are more sensitive to the variation of incident angle.Under the action of oblique waves,the strength of horizontal wave forces on the superstructure is highly related to the geometry of the structure.It is suggested that the structural dimension and incident angles of waves be considered in the design of the superstructure of the sea-crossing bridge.Efforts should be made to select appropriate geometry of the main girder and proper location of the bridge so as to minimize the impact of wave forces on the bridge superstructure.