Innovative Steel Braced Frame Systems for Enhanced Seismic Performance

钢支撑框架是最常用的结构体系之一，用于抵抗施加在建筑结构上的风和地震横向荷载。当在弹性范围内响应时，该系统非常有效，例如在风和小震情况下。然而，该系统已被证明在强震下表现出较差的性能，例如大的塑性变形和显著的永久变形。更高的抗震设计荷载、严格的高度限制和其他要求已在规范中实施，以实现对公众的最低安全。这些都增加了建设成本，限制了系统的应用范围，建筑物所有者可能面临长时间的停机时间以及重大地震事件后的重大维修/重建费用，这将导致加拿大经济的重大损失。 这项研究的目的是开发新型钢支撑框架体系，在极端地震后表现出优越的性能，没有或仅有有限的损害，以便能够迅速恢复运营，并将维修成本降至最低。将研究三种系统：用于低层应用的带底部剪切保险丝的摇摆框架；用于中等高层建筑的模块化脊椎系统；用于高层单层应用的多层支撑框架。这三种应用几乎涵盖了加拿大建造的所有钢结构建筑。摇摆框架将通过摇摆和自定心剪切保险丝串联作用来适应地震施加的位移，从而限制对每个机构的需求，并且结构不会受到结构破坏。模块化的脊柱概念消除了软层反应，允许在建筑物中使用钢支撑框架，超过加拿大规范目前规定的高度限制的2倍以上。该系统的设计使得非弹性地震变形只在地震后可以很容易更换的专用元件中产生。因此，即使在非常严重的地震中，结构也没有受到破坏。多层支撑框架现在必须用更重的柱来建造，以抵抗地震引起的弯曲需求，防止屈曲破坏。提出了另一种支撑配置，这种配置需要较小的柱，同时减少结构位移。 申请人最初提出了这三个系统，拟议的研究旨在完成正在进行的开发工作。对于所有这三个系统，研究包括制定有效的结构安排，使用先进的非线性地震分析检查它们在强地面运动下的反应，制定设计策略以优化它们的反应，并进行大规模物理测试以展示它们的性能。

Steel braced frames are among the most popular structural systems used to resist wind and earthquake lateral loads imposed to building structures. The system is very effective when responding in the elastic range as is the case under wind and small earthquakes. However, the system has been shown to exhibit poor performance under strong earthquakes such as large plastic deformations and significant permanent deformations. Higher seismic design loads, stringent height limits and other requirements have been implemented in codes to achieve minimum safety to the public. These have increased construction costs and limited the range of application of the system and building owners are likely to face long downtime periods as well as major repair/reconstruction costs after a major seismic event, which will result in major losses for the Canadian economy. This research aims at developing new steel braced frame systems exhibiting superior performance with no or limited damage after an extreme earthquakes such that operations can be resumed rapidly and repair costs are minimized. Three systems will be studied: rocking frames with base shear fuses for low-rise applications; modular spine systems for medium-rise buildings and multi-tiered braced frames for tall single-storey applications. These three applications cover nearly the entire range of steel building structures that are built in Canada. The rocking frame will be developed to accommodate seismic imposed displacements through rocking and self-centering shear fuse acting in series such that the demand on each mechanism is limited and the structure sustain no structural damage. The modular spine concept eliminates soft-storey response, allowing steel braced frames to be used in buildings more than 2 times the height limit currently specified in the Canadian code. The system is designed such that inelastic seismic deformations only develop in dedicated elements that can be easily replaced after an earthquake. Hence, the structure sustain no damage, even in very severe earthquakes. Multi-tiered braced frames must now be constructed with much heavier columns to resist the seismic induced flexural demand and prevent buckling failure. Alternative bracing configurations are proposed that require smaller columns while reducing the structure displacements. The applicant has originally proposed the three systems and the proposed research aims at completing ongoing development work. For all three systems, the research consists in developing effective structural arrangements, examining their response under strong ground motions using advanced nonlinear seismic analysis, developing design strategies to optimise their response and performing large scale physical testing to demonstrate their performance.