Collaborative Research: An Integrated Model for Performance-Based Assessment and Design of Secondary Systems Mounted on Building Structures

这项研究将开发、制定和验证一种创新和实用的方法来评估二次系统的地震需求和能力。次系统(即非结构构件)是指那些容纳或附着到建筑物或工业设施的楼板、屋顶和墙的系统和构件，这些系统和构件不属于主承重结构系统的一部分。二次系统在地震期间和地震后的存活对于减少人员伤亡、继续运行和减少直接破坏成本非常重要，直接破坏成本最高可达建筑物总成本的85%。在对这类系统的地震需求评估和对损失的估计方面，目前的知识和实践存在至少四方面的缺陷。首先，在几种情况下，现行规范规定对地震需求的估计不足，这将导致破坏和重大经济损失。第二，这类部件的简化设计方法没有明确说明这一过程中最重要的不确定因素。第三，目前的损失估计方法是基于单个组成部分的损失总和，没有明确考虑附带损害(即一个组成部分的损害对其他组成部分的损害的影响)的概念，这将导致对损失的不准确估计。第四，在评估使用动态运动的二次系统的损害和相关损失方面所做的努力非常有限，这种运动比通常使用的准静态加载方案更具代表性。这项研究的目的是制定和验证一种方法，用于对安装在弹性和非弹性初级结构上的次级系统的需求和能力进行应用评估。这一方法将考虑到这一过程中存在的不确定性，并最终有助于估计地震期间次级系统的破坏造成的经济/伤亡/停机时间损失。智力价值：研究结果对于(A)提供对安装在弹性和非弹性建筑物上的次级系统的地震响应的控制机制和参数的了解是至关重要的，(B)将结构和非结构系统的理论基础形成一个综合的计算机模型以量化对此类系统的地震需求，(C)开发一个综合的概率模型，用于对次级系统的峰值加速度(强度)和变形需求提供稳健和可靠的评估，以及(D)开发一种实用和有效的方法，以便使用动态加载协议获得次级元件的能力。对二次系统地震需求的准确和可靠预测将包括这一过程中最重要的不确定性来源。这对于准确估计地震期间二次系统受损造成的经济损失和伤害至关重要。更广泛的影响：这项研究的结果将对研究人员、设计工程师和建筑规范编写者有价值，他们必须为二次系统的抗震设计和评估做出决策和/或建立标准。从该项目中吸取的经验教训将被纳入设计实验的建议中，以了解和量化次级系统的地震能力，并减少这一预测的不确定性。概率方法论将促进结构工程、结构动力学、地震工程、统计和可靠性理论概念在建筑物二次系统保护中的同时并存。这项研究将提供研究生和本科生研究助理(一名在马里兰大学，一名在加州大学欧文分校)和一名本科生研究助理的教育。学生将通过学习结构、动力学、地震、概率和新的地震工程概念来学习研究过程和受益。一名大学预科学生也将在项目期间协助研究活动。该活动将促进未被充分代表的预科和本科工科本科生参与与研究相关的任务。其中一名PI是代表不足的群体的成员，因此他将成为代表不足的学生的专业榜样。

This research will develop, formulate, and validate an innovative and practical approach for assessing seismic demands and capacities of secondary systems. Secondary systems (i.e., nonstructural components) are those systems and elements housed or attached to floors, roofs, and walls of a building or industrial facility that are not part of the main load bearing structural system. The survival of secondary systems during and after an earthquake is important for the reduction of casualties, continuing functionality, and the reduction of direct damage costs, which can reach up to 85 percent of the total cost of the building. Shortcomings in the current state of knowledge and practice in the seismic demand assessment of such systems and the estimation of damage-induced losses are at least fourfold. First, in several cases, current code provisions provide inadequate estimates of seismic demands that will lead to damage and significant economic losses. Second, simplified design methodologies for such components do not explicitly account for the most important sources of uncertainties in the process. Third, current loss estimation methodologies are based on the summation of losses from individual components by which the concept of collateral damage (i.e., the effect of damage in one component on other components' damages) is not explicitly considered, which will result in an inaccurate estimate of losses. Fourth, very limited efforts have been placed to assess damages and associated losses for secondary systems using dynamic motions, which are more representative than commonly used quasi-static loading protocols. The goal of the study is to formulate and validate a methodology for applied assessment of demand and capacity of secondary systems mounted on elastic and inelastic primary structures. This methodology will account for uncertainties present in the process and ultimately help in the estimation of economic/casualty/down-time losses due to damages in secondary systems during earthquakes.Intellectual Merit: The results of the research are essential for (a) providing an understanding of the mechanisms and parameters that control the seismic response of secondary systems mounted on elastic and inelastic buildings, (b) formulating theoretical foundations of structural and nonstructural systems into a comprehensive computer model to quantify the seismic demands for such systems, (c) developing an integrated probabilistic model useful to provide a robust and reliable assessment of the peak acceleration (strength) and deformation demands of secondary systems, and (d) developing an applied and effective methodology for obtaining capacities of secondary elements using a dynamic loading protocol. The accurate and reliable prediction of seismic demands for secondary systems will incorporate the most important sources of uncertainty in the process. This is of paramount importance for accurate estimation of economic losses and injuries caused by damage to secondary systems during earthquake events. Broader Impacts: Results from this study will be of value to researchers, design engineers, and building code writers who have to make decisions and/or establish criteria for the seismic design and evaluation of secondary systems. The lessons learned from this project will be incorporated into recommendations for the design of experiments to understand and quantify the seismic capacity of secondary systems, as well as to reduce the uncertainty in this prediction. The probabilistic methodology will promote the concurrent incorporation of structural engineering, structural dynamics, earthquake engineering, and statistical and reliability theory concepts in the protection of secondary systems in buildings. This study will provide for the education of both graduate and undergraduate research assistants (one at the University of Maryland and one at the University of California, Irvine) and an undergraduate research assistant. The students will learn the research process and benefit by learning about structures, dynamics, earthquakes, probability, and novel earthquake engineering concepts. A pre-college student will also assist with the research activities for the duration of the project. The activity will promote the participation underrepresented pre-college and undergraduate engineering undergraduate students in research related tasks. One of the PIs is a member of an underrepresented group, so he will serve as a professional role model for underrepresented students.