Seismic performance improvement of buildings with self-centering bracings

支撑是建筑物中用于抵抗横向荷载的对角线结构构件。传统的支撑主要承担轴向载荷。它们在轴向张力下表现良好。然而，在压缩下，支撑容易弯曲，失去其承载能力。研究人员提出了屈曲约束支撑、屈服支撑等方法来克服屈曲问题。然而，它们的缺点包括：a)重量重，b)制造困难，c)地震后可能造成永久性损坏。本文提出了一种新的支撑系统来克服这些缺点。这些系统重量轻，即使在大地震期间也不会造成永久性损坏。该系统将使用安装在气缸活塞内的超弹性形状记忆合金（SMA）棒，或者在受限的橡胶混凝土组件中使用SMA板。设计合理的自定心支撑框架结构，由于其自定心能力，即使在大地震事件发生后，也有望保持运行，从而提高安全性和生存能力。它还将大大节省灾后所需的维修/更换工作，并有可能进行修复而不是拆除。这项研究的意义是至关重要的，因为这项新技术将帮助加拿大提高地震期间建筑基础设施的安全水平。第一阶段将包括评估SMA棒/板的机械性能以及将SMA连接到钢部件的耦合器的性能。将对支撑构件和支撑框架进行一系列大规模的准静态循环和动力试验。生成的实验数据将用于确定影响地震反应和极限状态的重要参数，这将有助于制定基于性能的支撑框架设计指南。提出的设计准则将通过混合模拟试验进行验证。研究小组会与合作伙伴及设计守则委员会紧密合作，制订适当的架构，把建议的设计建议纳入设计守则。

Bracings are diagonal structural elements in a building for resisting lateral loads. Traditional bracings essentially carry axial loads. They perform well under axial tension. However, under compression, braces tend to buckle and lose their load carrying capacity. Researchers have proposed buckling restrained bracing, yielding bracing, etc to overcome this buckling problem. However, their disadvantages including: a) heavy weight, b) fabrication difficulty, and c) potential permanent damages after an earthquake. Here, novel bracing systems are proposed to overcome these shortcomings. These systems will be light-weight, and will remain operational with no permanent damages even during a large earthquake. The proposed system will utilize superelastic shape memory alloy (SMA) bars installed inside a cylinder piston, or SMA plates in confined rubberized concrete assembly. A properly designed self-centering braced frame structure is expected to remain operational even after a large seismic event due to its self-centering capability, increasing safety and survivability. It will also provide large savings in reduced repair/replacement work necessary in a post-disaster scenario, and potential for remediation in place rather than demolition. The significance of this research is paramount as this novel technology will help Canada improve the level of safety of building infrastructure during earthquakes. The first stage will involve evaluating the mechanical properties of SMA bars/plates and performance of couplers that connect SMA to steel parts. A series of large-scale quasi-static cyclic and dynamics tests will be performed on bracing elements and braced frames. The generated experimental data will be employed to determine the important parameters that affect the seismic response and limit states, which will help develop performance-based design guidelines for braced frames. The proposed design guidelines will be validated with hybrid simulation tests. The research team will work closely with the partners and design code committee to formulate the appropriate framework with which the proposed design recommendations can be incorporated in the design codes.