强震下薄壁高墩公路桥抗震性能的模型更新混合试验研究

Bridges endowed with thin-walled tall piers account for more than 40% of the total number of bridges in southwestern China. However, the investigation on seismic performance of such bridges by seismic testing method are quite limited. The sub-structuring hybrid testing method is superior to shaking table tests as the requirements of testing equipment of the latter method are high for large-size bridges. The accuracy of numerical substructures as well as the simulation of the complex boundary conditions of experimental substructures is the key factor that limits the development of hybrid testing method. To this end, a hybrid testing method with online model updating is proposed considering incomplete boundaries and applied to investigate the seismic performance of tall-pier bridges. Firstly, a three-dimensional fiber element is formed considering shear effects and the simulation of high-order modes with low computational burden; a dual parameters identification method for multi-model is proposed based on this element to improve the versatility of model updating. Then, the parameter identification module based on incomplete boundaries of experimental substructures and the model updating module containing complete boundaries are established for simulating the complex boundaries; a software platform is set up to achieve the hybrid tests of tall-pier bridges to support the application of the proposed method. Finally, reveal the mechanism of the generation and development of plastic hinges of tall piers, and the contribution of high-order modes to the seismic responses of bridges; to give a threshold value of the main design parameters corresponding to different failure modes of tall piers. The outcomes of this project provide valuable supports for improving seismic design method and seismic resilience assessment of highway bridges endowed with tall piers.

薄壁高墩桥梁在我国西南地区占比超过40%，然而针对其抗强震性能的地震模拟试验研究十分有限。针对该类桥梁结构尺寸巨大、对振动台模拟设备要求高的问题，子结构混合试验方法具有显著优势。数值子结构分析精度低与试验子结构复杂边界条件模拟困难是限制混合试验方法发展的关键因素。本项目旨在针对薄壁高墩桥提出一种考虑非完整边界条件的模型更新混合试验方法，并深入研究该类桥梁的抗震性能。首先，建立考虑剪切效应与高阶振型高效模拟的3D纤维有限单元，基于该单元提出多模型参数识别方法，解决模型更新通用性问题。之后，建立不完整边界试验子结构参数识别模块和完整边界数值子结构更新模块，解决试验子结构复杂边界条件问题；最后搭建软件平台，开展薄壁高墩桥混合试验，揭示薄壁高墩塑性铰产生与发展机理，高阶振型的影响机制；针对高墩破坏状态给出主要设计参数的取值范围，为薄壁高墩公路桥梁抗震设计改进与韧性提升提供有力支持。

薄壁高墩桥梁在我国西南地区占比超过40%，然而针对其抗强震性能的地震模拟试验研究十分有限。本项目采用理论分析、数值模拟与试验研究相结合的方法，聚焦薄壁高墩公路桥梁模型更新混合试验方法研究。主要研究内容包括：1）提出了具有较好计算精度与计算效率的高墩分布式弯-剪模型，为以弯剪破坏为主要模式的空心高墩桥抗震性能分析提供有力支持，并推进了模型参数识别与更新在混合试验方法中的应用，拓宽其对结构的适用范围。2）提出了方程非解析的多本构模型多参数的联合识别方法，结合所提出的构件弯-剪模型与材料本构模型，大幅度提高了薄壁空心高墩桥数值子结构的计算精度，同时减小了模型误差，有效提高了材料本构参数用于模型更新的通用性。3）提出一种考虑非完整边界条件的、适用于多荷载耦合的混合试验方法，为风-震耦合作用下的高柔结构性能分析提供试验研究的保障；开发配套混合试验软件平台，降低所提出混合试验方法的应用门槛。4）揭示了高阶振型与空心截面应力分布对高墩损伤的影响机理，提出了适用于高墩桥的损伤测度参数与破坏模式估计方法，给出定量评价高墩桥抗震性能的分析方法。

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