基于P-a曲线的桥梁船撞动力需求分析冲击谱方法研究

Assessing the demand of bridge structures subjected to vessel collisions plays a key role in the research of vessel-bridge collision, related to accurately evaluate vessel-collision risk and design anti-collision measures and strategies. Although the equivalent static method widely used in the current design codes is very simple to be employed in practical engineering, it fails to capture the dynamic interaction between vessel and bridge in nature. Since the dynamic effect is not taken into account, the demand of the impacted structure may be extremely underestimated and the catastrophic accidents may happen, leading to human casualties and property losses. On the other hand, the method using general-purpose contact-impact nonlinear finite-element codes can obtain the process of vessel-bridge collisions. However, this method was not widely used in practical engineering, due to the shortcomings of numerical instability and low efficiency. Therefore, combined with model tests of vessel-bridge collisions, a shock spectrum analysis method will be developed based on the relationships of impact force (P) and crush depth (a) in this project to efficiently evaluate the accurate dynamic-demand of bridges subjected to vessel (including barge and ship) collisions. This project mainly includes: (1) modeling (or regularizing) dynamic P-a curves; (2) developing elastic and inelastic shock spectra, and proposing a modal combination rule and an index to determine the required number of modes for vessel collision analysis; (3) carrying out model tests considering vessel-bridge dynamic interaction using drop-hamper test systems. The expected research findings will benefit designing anti-collision measures and strategies economically and reasonably, and also provide a reference for developing a specialized design code for use by our bridge engineers in evaluating structures for vessel collision in future.

确定船撞下结构的需求是桥梁船撞研究中的基本问题，关系到能否正确评估船撞风险，设计防撞策略及措施。现有的规范静力法虽简单实用，但却难以反映船-桥相互作用的动力本质，没有考虑动力效应的影响，使结构需求被远远低估，可能导致重大安全事故，造成巨大的生命财产损失。采用非线性接触有限元技术虽可模拟船-桥碰撞过程，但存在数值易不稳定、计算效率低等不足，难以广泛运用。为此，本项目将结合船首拟静力和船-桥碰撞模型试验，探讨基于驳船和散货船两类船舶的撞击力（P）与撞深（a）关系曲线，系统地研究船撞冲击谱法，使其能高效、合理地估计桥梁结构的动力需求。主要内容有：（1）建立模型化动力P-a曲线；（2）构建弹性与非弹性冲击谱，以及适用于船撞的振型组合方法与所需振型数判断方法；（3）开展基于落锤试验机的船-桥动力相互作用模型试验。研究成果能为研究防撞措施与策略提供依据，也为将来我国制定专门的桥梁船撞设计规范提供参考。

建立行之有效的船撞桥梁结构动力需求分析方法是当前船撞研究中重要而关键的问题之一。本项目以建立基于P-a曲线的桥梁船撞动力需求分析方法为总目标，提出了桥梁船撞冲击谱分析方法，使其既具有传统规范静力法简单方便的特点，又能够较为合理地反映船-桥相互作用的动力本质。本项目开展的主要工作和成果有：（1）采用多种CAD/CAE软件联合建立了多种不同DWT的船舶精细化有限元模型，并形成了快速建立精细化船舶模型的一般性流程，为桥梁船撞动力分析提供了基础；（2）采用接触-碰撞有限元分析技术，较为深入系统地研究了船舶P-a曲线的局部和整体特征，阐明了船舶P-a曲线特征的物理含义，指出了应变率及接触面积对P-a曲线的影响规律，给出了考虑这些因素影响的计算公式；（3）研究了适用于船撞冲击谱分析的模态叠加方法，指出了传统地震反应谱分析中SRSS和CQC方法不适用船撞冲击谱分析中的原因，证明了桥梁结构船撞响应仅与有限阶模态有关且峰值响应时刻具有一定预测性；对大量船-桥碰撞情形进行模态时程分析，获得了估计峰值响应时刻的四种基本类型，建立了峰值响应时刻的估计公式，提出了Weighted Algebraic Sum (WAS)模态组合方法，并验证方法的有效性；（4）结合湖南大学高性能落锤试验机系统，开展了多组受压墩柱抗冲击性能试验，指出了影响桥墩抗撞能力的主要因素，并研究了修正的数值模拟方法。在该项目资助下，项目负责人及团队已在《ASCE Journal of Engineering Mechanics》等SCI期刊发表论文5篇，《中国公路学报》EI论文1篇，国际会议论文2篇，获批国家发明专利1项，实用新型专利1项，撰写《桥梁工程》和《桥梁设计百问》等书籍桥梁船撞相关章节等。本项目研究成果将促进桥梁船撞领域的研究，并为我国将来制定专门的桥梁船撞设计规范提供参考。