子结构混合试验关键技术研究

This project aims to develop a substructure online hybrid test platform that can be extensively used to evaluate the seismic performance of complex structrues. The substructure online hybrid test platform is the kernel of the project, which adopts a novel parallel time integration scheme to config the analytical and experimental environment, together with existing software and hardware. There are two challenges to develop a consummate online hybrid test system, i.e., (1) to coordinate the boundary condition between substructures, and (2) to experimentally control complex boundaries, particularly those with coupled degrees of freedom. To this end, the studies are categorized into three groups, specifically, theoretical basis on parallel time integration algorithm, key techniques to realize a practical platform including boundary coordinator and physical executor, and a demonstration experiment applied to a complex structure. The parallel time integration method is to be developed based on the Group Implicit algorithm, with its numerical characteristics thoroughly explored using an energy-based method. An interface element will be employed to coordinate substructures with different mechanical features, such as porous soil and solid structures. To reasonably answer the question about how to partition substructures, a criteria is developed and quantified by use of a frame structure and a wall structure, respectively. Moreover, an unbalanced energy index is employed to monitor the error accumulated during the online hybrid test process. In order to physically control nonlinear complex boundeires, a force-displacement mixed control method adopting multiple control loops, and a flexible test scheme approximating the boundary conditions are proposed in this study, which are particulaly useful to deal with complex boundaries with highly coupled loading devices. Eventually, the developed online hybrid test system is employed to investigate the seismic failure mechanism of a high-rise steel reinforced concrete structure system considering soil-structure interaction, which also serves as the complete demonstration of the developed substructure online hybrid test platform.

本项目将以子结构混合试验方法为对象，在理论基础、平台建设和应用研究三个方面开展工作。本项目的核心是子结构混合试验平台建设，以新型的积分算法为理论依据，建立并行的分析和试验环境，在已有软硬件基础上，进一步解决边界协调技术和控制方法难题，建设完善的子结构混合试验平台。本项目的理论基础是高效的子结构并行积分方法，将基于GI隐式方法提出适合混合试验的积分算法，并采用基于能量的方法对其数值特征做出科学合理的解释；发展界面协调单元技术解决混合试验中不同特征子结构的协调问题，回答如何合理的划分子结构这个科学问题，提出划分子结构的准则，并应用不平衡能量指标实时监测试验误差的累积过程；针对复杂非线性边界的控制难点，提出采用多层控制循环的多自由度力-位移混合控制方法和柔性边界处理方式；最终通过高层混合结构体系对子结构混合试验平台进行全面的验证。

混合试验技术是近十年来发展的重要结构工程抗震试验方法，这种方法一方面可以采用大型试验体进行试验，采用精细的有限元进行分析，结合了两种手段的优点，有利于提高地震模拟的精度；另一方面可以整合多个实验室的资源进行加载，从而大大提高了试验能力，特别适合于大型复杂结构体系的地震响应模拟。但是现有算法适用的结构动力系统较为简单，边界自由度个数有限，对于复杂工程结构体系适应性较差，难以满足复杂工程结构地震响应模拟的需要。同时试验系统的协调器必须确保子结构在边界上的协调和平衡，才能实现整体结构真实的动力响应。如何利用这些有限信息系统的寻求边界位移，保证平衡条件，同时兼顾复杂工程结构力学特征的多样性，这是子结构混合试验的核心科学问题。同时如何解决非线性多自由度系统的力-位移混合控制模式，是实现复杂边界条件控制的基础问题，也是制约混合试验方法应用的技术瓶颈。.过本项目研究，推动了子结构混合试验技术的发展，在新型无条件稳定数值积分方法、子结构边界协调技术方面取得了重要成果，并利用所开发的平台进行了大型结构混合动力试验。无条件稳定积分方法包含了刚度识别过程，可用于刚度强化结构的动力响应模拟，这种非线性是其他研究所未涉及的。子结构协调技术包括柔性加载制度、重叠领域协调方法、多自由度力位移混合加载方法。柔性加载制度保证了在主要自由度满足协调和平衡条件下，放松次要自由度的协调条件，从而使混合试验技术在现有技术条件下更容易实现；重叠领域协调方法，通过数值和试验的重叠构件实现边界条件，避免了对转动自由度的直接控制；多自由度力位移混合加载方法，实现了大刚度自由度的精确控制，在此技术上，申请了控制方法和多自由度加载平台两个专利，可将该技术通过新型加载平台进行应用。同时也促进了结构构件在真实受力条件下的实验研究，从而具有重要的科学意义和实用价值。