Passive Energy Dissipation Devices for Upgrading of Steel Structures

北岭地震对大量多层钢结构建筑造成了重大破坏。对于这种损伤，人们提出了许多不同的解释，包括焊接问题、钢材的材料特性、总体设计理念以及结构系统中缺乏冗余和多个横向抗载荷路径。与这些观察结果相结合的事实是，最近的一些实验研究强调了大型焊接钢连接在非弹性循环载荷下的潜在不良性能。提高钢结构建筑抗震性能的一种方法是通过引入特殊装置来提高结构系统的耗能能力，从而降低主要结构系统关键区域的能耗需求。本项目对钢框架结构被动耗能的效益进行了分析与试验相结合的研究。研究了四种不同的被动耗能系统。这些装置代表了无源装置的主要类别：摩擦、金属、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。然后将这些数值模型用于分析研究。另外两种类型的被动阻尼器（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。一个实际的钢结构建筑，典型的那些遭受破坏的北岭地震被识别和使用作为分析研究的基础。选取了一组地震地震动，分别代表服务级、中、强地震震动。选定的建筑首先在其现有（未升级）条件下进行分析。针对该建筑设计了基于四种阻尼装置的升级方案，并通过对响应参数的仔细比较研究了它们的效益。通过考虑主要结构系统的延性和能量需求，以及使用适当的响应参数评估非结构部件和内容物的损伤来评估性能效益。最后评估了升级方案对建筑物在地震下的经济损失脆弱性的影响。被动能量耗散技术代表了现有结构抗震升级的一种方法，与传统方法相比，它提供了性能和经济效益。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. ***