Passive Energy Dissipation Devices for Upgrading of Steel Structures

9416516 Betereo北岭地震对大量多层钢框架建筑造成重大破坏。人们对损坏提出了许多不同的解释，包括焊接问题、钢的材料特性、总体设计理念以及结构系统中缺乏冗余和多个抗侧向荷载路径。与这些观察相伴随的是，最近的几项实验研究突显了大型焊接钢节点在非弹性循环荷载下的潜在劣化性能。提高钢结构建筑抗震性能的途径之一是通过引入特殊的耗能装置来提高结构体系的耗能能力，从而减少主结构体系临界区的能量需求。本文对钢框架结构被动耗能的效益进行了理论分析和试验研究相结合的研究。研究了四种不同的被动消能体系。这些设备代表了主要类别的被动设备：摩擦型、金属型、纯粘性和粘弹性。对两种装置(摩擦装置和纯粘性装置)进行了实验研究，并利用试验结果建立了两种装置的数值模型。这些数值模型随后被用于分析研究。另外两种被动阻尼器(形状记忆合金和粘弹性)也包括在研究中，但在本项目中没有进行实验研究。在前人和当前研究成果的基础上，建立了这些阻尼器的数值模型。确定了一个实际的钢结构建筑，这是在北岭地震中遭受破坏的典型建筑，并作为分析研究的基础。选择了一组地震地面运动，分别代表服务水平、中等地震和严重地震震动。首先分析选定的建筑在其现有(未升级)状态下。设计了基于四种减震装置的升级方案，并通过对响应参数的仔细比较来研究它们的效益。通过考虑延性和对主结构系统的能量需求，以及通过使用适当的响应参数评估对非结构构件和内容的损伤来评估性能效益。最后对升级方案对建筑物地震经济损失易损性的影响进行了评估。被动耗能技术代表了一种对现有结构进行抗震升级的方法，它提供了比传统方法更好的性能和经济效益。本研究项目旨在进一步发展和完善使用这些技术进行升级的方法。这是一个北岭地震项目。***

9416516 Betereo The Northridge earthquake caused significant damage to a large number of multistory steel framed buildings. A number of different explanations for the damage have been proposed, including problems with welding, the material properties of the steel, and the general design philosophy and lack of redundancy and multiple lateral-resisting load paths in the structural systems. Coupled with these observations is the fact that several recent experimental investigations have highlighted the potential poor performance of large welded steel connections under inelastic cyclic loading. One approach for improving the seismic performance of the types of steel buildings is to increase the capability of the structural system to dissipate energy by introducing special devices for this purpose, and thus decreasing the energy demands on critical regions of the primary structural system. A combined analytical and experimental study focusing on the benefits of passive energy dissipation for steel frame structures is undertaken in this project. Four different passive energy dissipation systems are investigated. These devices are representative of the main classes of passive devices: friction, metallic, pure viscous, and viscoelastic. Two devices are studied experimentally (friction and pure viscous), and the results of the testing are used to develop numerical models of the two types of devices. These numerical models are then utilized in the analytical study. Two other types of passive dampers (shape memory alloy and viscoelastic) are also included in the study, but not investigated experimentally in the present project. Numerical models are developed for these dampers based on the results of other pervious and current research. An actual steel building, typical of those that suffered damage in the Northridge earthquake is identified and used as the basis of the analytical study. A set of earthquake ground motions are chosen, representing service-le vel, moderate and severe earthquake shaking. The selected building is first analyzed in its existing (non-upgraded) condition. Upgrade schemes based on each of the four types of damping devices are designed for the building and their benefits investigated by a careful comparison of response parameters. The performance benefits are assessed by considering ductility and energy demands on the primary structural system, and also by evaluating damage to nonstructural components and contents using appropriate response parameters. The impact of the upgrade schemes on the vulnerability of the building to economic loss due to earthquake shaking is finally assessed. Passive energy dissipation techniques represent a method for seismic upgrading of existing structures that offers performance and economic benefits over conventional approaches. This research project is designed to further develop and refine the methodologies for upgrading using these techniques. This is a Northridge earthquake project. ***