Seismic ratcheting of eccentric gravity loaded moment-resisting frame buildings
Seismic ratcheting of eccentric gravity loaded moment-resisting frame buildings
复制标题
偏心重力荷载抗弯框架建筑的地震棘轮
DOI：
10.1002/eqe.3790
复制
发表时间：
2023
影响因子：
4.5
通讯作者：
Koichi Kusunoki
中科院分区：
文献类型：
--
作者：
Trevor Z Yeow;Koichi Kusunoki
在地震中，结构可能主要在单一方向上发生非弹性变形，从而造成更大的破坏。这种行为被称为地震棘轮，可能是由偏心重力载荷引起的。加拿大和新西兰引入了规范条款，以放大静力分析方法获得的位移，以考虑地震棘轮效应。然而，这些条款是基于对钢筋混凝土（RC）墙或单自由度（SDOF）结构的分析，并且没有明确提供减轻地震棘轮行为的方法。在本研究中，对钢筋混凝土和钢筋混凝土抗弯矩框架建筑进行了参数分析，以评估规范条款的充分性，确定影响地震棘轮行为的参数，并提出减轻这种行为的方法。研究发现，新西兰规范低估了钢筋混凝土建筑的位移增量，尽管它能够覆盖钢结构建筑的位移增量，而加拿大规范则是保守的。此外，位移增加对建筑物的屈服后行为和地震动特性很敏感。然而，在设计期间对这些特性的假设可能不能反映实际的建筑和地震条件，这表明很难获得对位移增加的可靠估计。相反，采用缓解措施来减少地震棘轮效应，例如设计更高的地震要求，增加二次结构系统以增加建筑物的后弹性刚度，或在调整了偏心重力载荷效应后提供更平衡的横向强度，这些都是更好的措施来对抗由偏心重力载荷引起的地震棘轮效应。
Structures may predominantly inelastically deform in a single direction during earthquakes and incur greater damage. This behavior is known as seismic ratcheting and can be caused by eccentric gravity loads. Code clauses were introduced in Canada and New Zealand to amplify displacements obtained from static analysis methods to consider seismic ratcheting effects. However, such clauses are based on analyses of reinforced concrete (RC) wall or single‐degree‐of‐freedom (SDOF) structures, and methods to mitigate seismic ratcheting behavior were not explicitly provided. In this study, parametric analyses of steel and RC moment resisting frame buildings were performed to evaluate the adequacy of code clauses, identify parameters which influence seismic ratcheting behavior, and propose methods to mitigate such behavior. It was found that the New Zealand code underestimated the displacement increase for RC buildings, though it was able to envelope the displacement increase for steel buildings while the Canadian code was conservative. Additionally, the displacement increase was found to be sensitive to the building's post‐yield behavior and ground motion properties. However, assumptions of these properties during design may not be reflective of the actual building and seismic conditions, indicating that a reliable estimate of the increase in displacement is difficult to obtain. Instead, employing mitigation measures to reduce seismic ratcheting effects, such as designing to higher seismic demands, adding a secondary structural system to increase the building's post‐elastic stiffness, or providing more balanced lateral strengths after adjusting for eccentric gravity load effects are better measures to counter seismic ratcheting effects caused by eccentric gravity loads.