Retrofit of Rocking Structures

摇摆结构的改造

基本信息

批准号：
EP/H032657/1
负责人：
Matthew DeJong
金额：
$ 12.84万
依托单位：
University of Cambridge
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2010
资助国家：
英国
起止时间：
2010 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=EP%2FH032657%2F1
关键词：
Retrofit Rocking Structures

项目摘要

Numerous structures exhibit rocking behaviour when loaded dynamically, including unreinforced masonry structures, monuments, towers, bridge piers, sculptures, etc. The collapse of these structures due to dynamic loading has caused global destruction, as recently exhibited by earthquakes throughout the world. In the UK, collapse of masonry bridges during intense traffic loading is also a large concern. Thus, there is a national and international need to prevent the devastation caused by the collapse of these structures.Despite a significant amount of research in this area, engineers still misunderstand the fundamental difference between the dynamic response of rocking structures and typical elastic structures, and therefore assess rocking structures from a flawed perspective. The typical solution is to prevent rocking behaviour instead of controlling it. Prevention is usually achieved by tying structures down or reinforcing them. In the case of masonry structures, this is accomplished by drilling through structures and adding steel reinforcing, or by wrapping structures in Fibre-Reinforce Polymers (FRP). While these methods can be effective, they can over-stiffen structures and be destructive. Adding stiffness drastically changes fundamental dynamic behaviour, and can cause high stresses which lead to local damage. Such damage could be prevented with alternate retrofit solutions.The primary goal of this research is to develop new methods of controlling rocking motion using optimized damping solutions (e.g. shock absorbers). Instead of adding stiffness to the structure, damping is proposed because it allows some motion while dissipating unwanted energy. Thus, both devastating collapse of structures which have not been reinforced, and unnecessary local damage due to over-stiffening, could be prevented.In this context, this research will aim to characterize the fundamental behaviour of damped rocking motion through analytical modelling. A single rocking block analytical model will serve as tool to determine the type of damping which best controls rocking motion, and then to optimize the specific characteristics of damping mechanisms. Subsequently, more complex analytical models which describe the rocking behaviour of masonry arches will be created. Arches are typical components of masonry buildings and bridges, so understanding their dynamic behaviour is critical in developing appropriate retrofitting solutions. Analytical arch models will be used to test a variety of retrofit schemes which incorporate optimized damping mechanisms.While analytical models are critical for characterizing behaviour and designing retrofit solutions, experimental testing is essential to evaluate their accuracy. Results of analytical modelling will first be used to inform the design and construction of optimized spring-damper elements. These elements will enable the retrofit of blocks and arches which will be tested under horizontal ground motion using a small scale shake table. Experimental results will be used to evaluate analytical modelling results and to determine the effectiveness of retrofit solutions.Finally, analytical modelling is effective for simple structures, but it is typically not feasible for more complicated ones. Thus, the final aim of this work is to use commercial Discrete Element Modelling (DEM) software to predict experimental results. DEM is an appropriate tool for this purpose because it is tailored to model the interaction of multiple distinct blocks. If DEM is determined to be accurate, it could be an essential tool for designing and testing retrofit solutions for more complicated structures.In summary, new retrofit solutions are needed. This research aims to lay the foundation for the development of a new class of retrofit solutions which exploit clever damping systems. In the process, scientific progress will be made regarding the control of non-smooth dynamic systems in general.

许多结构在动态加载时都会表现出摇摆行为，包括无筋砌体结构、纪念碑、塔楼、桥墩、雕塑等。这些结构由于动态加载而倒塌已造成全球性破坏，正如最近世界各地的地震所表明的那样。在英国，砖石桥梁在交通负荷繁忙时倒塌也是一个大问题。因此，国内和国际上都需要防止这些结构倒塌造成的破坏。尽管在这一领域进行了大量的研究，但工程师们仍然误解了摇摆结构和典型弹性结构的动力响应之间的根本区别，并且因此，从有缺陷的角度评估摇摆结构。典型的解决方案是防止摇摆行为而不是控制它。预防通常是通过绑扎或加固结构来实现的。对于砌体结构，这是通过在结构中钻孔并添加钢筋，或通过用纤维增强聚合物 (FRP) 包裹结构来实现的。虽然这些方法可能有效，但它们可能会使结构过度僵化并具有破坏性。增加刚度会极大地改变基本的动态行为，并可能导致高应力，从而导致局部损坏。通过替代改造解决方案可以防止此类损坏。本研究的主要目标是开发使用优化阻尼解决方案（例如减震器）控制摇摆运动的新方法。提出阻尼而不是增加结构的刚度，因为它允许一些运动，同时消散不需要的能量。因此，可以防止未加固结构的破坏性倒塌，以及由于过度刚化而造成的不必要的局部损坏。在这种背景下，本研究旨在通过分析模型来表征阻尼摇摆运动的基本行为。单个摇摆块分析模型将作为工具来确定最好控制摇摆运动的阻尼类型，然后优化阻尼机构的具体特性。随后，将创建描述砖石拱的摇摆行为的更复杂的分析模型。拱门是砖石建筑和桥梁的典型组成部分，因此了解其动态行为对于开发适当的改造解决方案至关重要。分析拱模型将用于测试各种包含优化阻尼机制的改造方案。虽然分析模型对于表征行为和设计改造解决方案至关重要，但实验测试对于评估其准确性至关重要。分析建模的结果将首先用于指导优化弹簧阻尼器元件的设计和构造。这些元件将能够对砌块和拱门进行改造，并使用小型振动台在水平地面运动下进行测试。实验结果将用于评估分析建模结果并确定改造解决方案的有效性。最后，分析建模对于简单结构有效，但对于更复杂的结构通常不可行。因此，这项工作的最终目标是使用商业离散元建模（DEM）软件来预测实验结果。 DEM 是用于此目的的合适工具，因为它是为模拟多个不同块的交互而定制的。如果DEM被确定是准确的，它可能成为设计和测试更复杂结构的改造解决方案的重要工具。总之，需要新的改造解决方案。这项研究旨在为开发利用智能阻尼系统的新型改造解决方案奠定基础。在此过程中，一般而言，非光滑动态系统的控制将取得科学进展。