EAPSI:Seismic performance of vintage Japanese braced-frame buildings before and after retrofit

在美国和日本的钢结构建筑中，通常采用中心支撑框架（CBF）来抵抗地震力。目前仍在使用的许多CBF都是在20世纪80年代末之前设计的，当时的设计重点是强度和刚度。当时的抗震规定意味着建筑物可以在保持强度的同时承受非弹性（永久）变形，但这并不一定能保证。因此，这些老式CBF预计将表现出不可接受的性能（例如，在大地震中，这一点得到了日本几次地震观测的支持。PI将与京都大学防灾研究所的Masayoshi Nakashima教授合作，他是抗震钢结构建筑设计的主要研究人员，调查日本老式CBF的抗震性能以及旨在提高性能的几种改造方案的有效性。PI在美国对老式CBF进行的一项正在进行的平行研究中开发的数值模拟技术将被利用和修改，以表征常见的日本建筑。这项研究将促进对日本老式CBFs的行为和改造的理解，这些CBFs可以应用于美国同行。美国和日本的CBFs具有相似的血统，特别是预容量设计CBFs由于强度，细节，几何形状和材料缺陷而引起了工程界的极大关注。PI和合作者最近对现有和改造的美国老式CBF进行的子装配测试表明，这些特性会严重限制非弹性变形能力或显著影响组件屈服和失效的顺序。利用美国和日本CBF之间的相似性，该实验数据将用于校准支撑和角撑板连接模型，数值模拟日本常见的老式CBF组件。日本的研究人员和工程师将帮助确定研究建筑物的特征，并确定潜在的改造方案，将使用代表各种危险水平的地震动套件进行非线性反应历史分析。东亚和太平洋夏季研究所计划下的这个奖项支持美国研究生的夏季研究，由NSF和日本科学促进会共同资助。

Concentrically braced frames (CBFs) are commonly used in steel buildings in the US and Japan to resist earthquake-induced forces. Many CBFs that remain in use today were designed prior to the late 1980s, when design focused on strength and stiffness. Seismic provisions at the time implied buildings could sustain inelastic (permanent) deformations while maintaining strength, but this was not necessarily ensured. Consequently, these vintage CBFs are expected to exhibit unacceptable performance (e.g., collapse) in large earthquakes, and this has been supported by observations from several earthquakes in Japan. The PI will collaborate with Professor Masayoshi Nakashima of the Disaster Prevention Research Institute at Kyoto University, a leading researcher in seismic steel building design, to investigate the seismic performance of vintage CBFs in Japan and the efficacy of several retrofit schemes intended to improve performance. Numerical simulation techniques developed in an ongoing parallel study conducted by the PI on vintage CBFs in the US will be utilized and modified to characterize common Japanese construction. The research will advance the understanding of the behavior and retrofit of vintage Japanese CBFs which can be applied to their US counterparts.CBFs in the US and Japan have similar lineage, and pre-capacity-design CBFs in particular have drawn considerable concern from the engineering community due to strength, detailing, geometric, and material deficiencies. Recent subassemblage testing of existing and retrofitted US vintage CBFs by the PI and collaborators has shown that these characteristics can severely limit inelastic deformation capacity or significantly affect the sequence of component yielding and failure. Leveraging the similarities between US and Japanese CBFs, this experimental data will be used to calibrate brace and gusset-plate connection models that numerically simulate vintage-CBF components common in Japan. Researchers and engineers in Japan will help establish characteristics of study buildings and determine potential retrofit alternatives, and nonlinear response history analysis will be employed using ground motion suites representative of various hazard levels. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Japan Society for the Promotion of Science.