Innovative Steel Braced Frame Systems for Tall Buildings in Seismic Active Regions

在加拿大，钢支撑框架广泛用于建筑结构的抗风和抗地震横向荷载。该系统易于设计、制作和安装。它代表了在风和小地震下实现横向强度和刚度的最经济有效的解决方案。然而，该系统在强震下表现不佳，如大的非弹性变形和显著的永久变形。对于高层建筑来说，它可能容易发生楼层集中漂移，从而导致整体不稳定和结构倒塌。为了达到适当的地震反应和公众安全，规范中已经实施了措施，包括更高的设计地震荷载和严格的高度限制。这些都增加了建筑成本，限制了系统的应用。此外，在重大地震事件发生后，建筑物业主可能面临长时间的停机时间和高昂的维修/重建成本，这可能会给加拿大经济带来重大损失。该研究将重点开发两种新型钢支撑系统，它们可以实现卓越的抗震性能，在极端地震后没有或有限的损坏，从而可以快速恢复功能，并将维修成本降至最低。第一个系统是一种创新的混合支撑系统，其中弹性支撑和非线性支撑与弹性梁相结合，产生正的屈服后刚度，确保稳定的地震响应和自定心能力。该系统可以与弹性节段脊柱系统相结合，以实现对结构高度更均匀的楼层漂移需求。第二种系统建立在可控摇摆支撑框架系统的基础上，该系统是在过去二十年中发展起来的，用于消除强震事件后的结构破坏和永久性结构变形。该项目最初的贡献是一种新的自定心层剪切保险丝，它减少了对结构的力需求，从而降低了其初始成本。这种新颖的剪切保险丝的灵感来自于第一个项目中描述的混合支撑框架系统。这两项研究的目的都是开发适合位于加拿大东部和西部地震活跃地区的高层建筑的支撑钢框架。该研究有望通过先进的非线性地震分析验证有效的结构配置和设计方法。还计划进行振动台试验和全尺寸循环试验来验证所提出系统的响应。还将进行研究，以改进使用支撑框架的设计规定与偏心和槽隐藏支撑连接的HSS成员。还将进行试验和数值模拟，以评估建筑结构重力框架中梁柱连接的塑性旋转能力。

Steel braced frames are widely used to resist wind and earthquake lateral loads for building structures in Canada. The system is easy to design, fabricate and erect. It represents the most cost-effective solution to achieve the lateral strength and stiffness under winds and small earthquakes. However, the system can exhibit poor performance under strong earthquakes such as large inelastic deformations and significant permanent deformations. For tall buildings, it can be prone to concentrations of storey drifts that can lead to global instability and structural collapse. Measures have been implemented in codes to achieve proper seismic response and safety to the public, including higher design seismic loads and stringent height limits. Those have increased construction costs and limited the application of the system. In addition, building owners are likely to face long downtime periods and high repair/reconstruction costs after a major seismic event, which may lead to significant losses for the Canadian economy. The research will focus on the development of two new steel bracing systems that can achieve superior seismic performance, with no or limited damage after an extreme earthquake, such that functionalities can be quickly restored, and repair costs are minimized. The first system is an innovative hybrid bracing system in which an elastic brace and a nonlinear brace are coupled with an elastic beam to generate a positive post-yielding stiffness that ensures stable seismic response and self-centering capabilities. The system can be coupled with an elastic segmental spine system to achieve more uniform storey drift demand over the structure height. The second system builds on the controlled rocking braced frame system that has been developed in the last two decades to eliminate structural damage and permanent structural deformations after a strong earthquake event. The original contribution from the proposed project is a new self-centering storey shear fuse that diminishes the force demand on the structure to reduce its initial cost. This novel shear fuse is inspired from the hybrid braced frame system described in the first project. Both studies will be conducted with the objective of developing braced steel frames suitable for tall buildings located in seismic active regions of eastern and western Canada. The research are expected to lead to effective structural configurations and design methodologies that will have been validated through advanced nonlinear seismic analysis. Shake table experiments and full-scale cyclic tests are also planned to validate the response of the proposed systems. Research will also be conducted to improve design provisions for braced frames using braces with intentional eccentricity and slotted hidden brace connections for HSS members. Testing and numerical simulations will also be performed to assess the plastic rotation capacity of beam-to-column connection in the gravity frame of building structures.