Low-Damage Seismic Solutions for Structural Systems with Wood

在典型的抗震设计方法中，只要能保证生命安全，大地震时的破坏是可以接受的。但在最近的地震中，巨大的经济损失引发了人们对结构在震后恢复成本和时间方面的性能的质疑。另一种被称为“低破坏解决方案”的方法，通过允许系统内牺牲元素的破坏来避免对主要结构成员的破坏，引起了设计师、规划人员和社区的极大兴趣。此外，还规定在大地震发生后更换损坏的部件，并在短时间内以合理的费用使结构恢复到充分发挥功能的水平。应用低损伤原理的最著名的机制之一是结合无粘结后张拉和低碳钢屈服元件。后张筋本质上是弹性金属链，贯穿结构构件，将它们连接在一起，从而确保地震后组件的完整性和完全自定心。位于连接处的低碳钢通过显著的非弹性变形吸收能量，从而保护主要结构成员免受损坏。

In typical seismic design approach, damages during a major earthquake are considered acceptable as long as life safety is achieved. But significant financial losses in recent earthquakes have raised questions about performance of structures in terms of post-earthquake recovery cost and time. One alternative approach termed “Low-damage Solution”, which avoids damage to the main structural members by allowing damages in sacrificial elements within the system, has attracted significant interest from designers, planners and the community. Provisions are also made to replace the damaged elements after a major earthquake and bring the structure back to a fully functional level within a short period of time at a reasonable cost. One of the most well-known mechanisms that applies the low-damage philosophy involves the combination of unbonded post-tensioning and mild steel-yielding elements. The post-tensioning tendons are essentially elastic metal strands that run through the structural members holding them together, thereby ensuring integrity and full self-centering of the assembly following an earthquake. The mild steel elements located at connections absorb energy through significant inelastic deformations, in turn protecting the main structural members from damage. Over the last decade, the concept has been successfully implemented with structural members made of engineered wood products through extensive research and a number of applications, mostly in New Zealand. The technology has recently been imported to North America, (known as post-tensioned' wood structures) where it is financially competitive only for high-rise (up to 14 stories) wood buildings. But very limited information is currently available on structural systems for wood buildings beyond six stories in general. The two regions of both Canada and the United States most likely to have tall wood buildings also have significant seismic risks. This underlines the need for comprehensive research on structural systems, i.e. assemblies of members, for tall wood buildings. This research program will explore building structural systems that are most likely to be suitable for the 8 to 14 storied height range. The proposed systems are: frames with cross-bracings, frames in combination with individual or multiple walls, and Hybrid structures, i.e. combination of wood with concrete and/or steel. Attempts will be made to develop practical guidelines and details for all the systems to promote widespread applications. The benefits to my field and Canada will be two-fold: first, the new understandings and expectations for better seismic performance of structures will eventually help improved standards of design practice ensuring better life safety; and secondly, the new knowledge will advance the country's standing in terms of wood construction, leading to potential growth in the forestry sector and ensuing economic benefits.