Simulation Platform for the Earthquake Response of Reinforced Concrete Structures

研究动机：钢筋混凝土结构（RCS）是一种强非均质复合材料，其性能取决于脆性混凝土和韧性钢筋之间的微妙相互作用。在极端的地震事件下，这两个组件之间的相互作用是至关重要的RCS的安全和生存的戏剧性失败最近在土耳其，台湾，日本和美国的地震。Objective. It表明：建议开发一个3-dim仿真平台的地震响应，SPER，模拟逐步失败的RCS受到地震事件。FEMS-FETI的并行有限元架构由Farhat博士的团队开发，用于解决大型流体-结构相互作用问题，为拟议的地震模拟环境提供了基本平台。SPER将采用一种新的非线性求解器，使用不完全消除，和一个创新的界面模型，以捕捉局部开裂和剪切破坏混凝土。为了验证概念，将检查RC柱，其中准静态失效以级联事件的形式发生，例如混凝土保护层的剥落、钢筋的渐进剥离、横向箍筋的屈服和断裂以及随后的轴向钢筋屈曲。作为系统分析的说明性示例，将选择两跨RC桥梁结构来突出桥梁上部和墩之间的三维相互作用，并展示SPER的可扩展性。长期目标设想高架交通系统的多层子结构模型，以坂神高速公路为例，该高速公路在1995年科比地震中出现了戏剧性的多段故障。 方法：拟议的SPER软件将基于多级/多重网格、区域分解和不完全非线性消除方法的组合。粗略地说，在这些算法中，（i）区域分解提供了并行性，（ii）多级提供了一个可扩展的计算环境，相对于问题的大小和并行计算机上的处理器的数量，而（iii）不完全消除消除了非线性求解器的敏感性，局部奇点。 相关性：RCS的逐步退化在地震工程中是一个非常重要的问题。目前的设计理念已经转向基于性能的方法，这需要对弹性范围之外的结构行为进行可靠的评估。SPER旨在模拟现有RCS的抗震性能，这些RCS是根据较旧的且通常不保守的地震规定建造的，并有助于开发快速且具有成本效益的修复程序。 外联：将通过一个网站传播特别项目报告，该网站将记录RCS基于模型的地震模拟软件的进展和成果。从长远来看，其目的是最终将SPER的三维能力纳入即将推出的NSF地震工程模拟网络（NEES），并在其中开发基于互联网的地震模拟能力，供学术界和地震工程界的同事使用。人力资源和教育：探索性研究将涉及来自土木工程，计算机科学和航空航天工程的三名研究生研究助理，分别由三个部门的四个Co-Pi指导和监督。他们将在跨学科的环境中工作，包括民用基础设施系统，并行计算技术和数值解决方案。仿真平台SPER将被用作教育工具，在一些本科生和研究生课程，正在提供的土木工程计划在科罗拉多大学，如钢筋混凝土结构的设计，地震工程和计算力学。SPER还将作为公众宣传的示范工具，特别是针对高中教师和K-12学生的地震灾害意识。这项工作将利用科罗拉多大学新的综合教学实验室（ITLL），该实验室因其通过发现进行学习的新颖方法而受到全国关注。

Motivation:Reinforced Concrete Structures, RCS, are strongly heterogeneous composites, the performance of which depends on the subtle interaction of the brittle concrete and the ductile reinforcement. Under extreme seismic events, the interplay between the two components is critical for the safety and survival of RCS as demonstrated by dramatic failures recent earthquake in Turkey, Taiwan, Japan, and the USA.Objectives:It is proposed to develop a 3-dim simulation platform for the earthquake response, SPER, to model progressive failure of RCS subjected to seismic events. The parallel finite element architecture of FEMS-FETI, which was developed by the team of Dr. Farhat for the solution of large fluid-structure interaction problems, provides the basic platform for the proposed earthquake simulation environment. SPER will feature a novel nonlinear solver using incomplete elimination, and an innovative interface model to capture localized cracking and shear failure in concrete. For proof of concepts, a RC column will be examined in which quasi-static failure takes place in the form of a cascade of events, such as spalling of the concrete cover, progressive debonding of the reinforcement, yielding and rupturing of the transverse stirrups, and subsequent buckling of the axial reinforcement. As an illustrative example on system analysis, a two-span RC bridge structure will be selected to highlight the 3-dim interaction between the bridge super-and the pier and to showcase the scalability of SPER. The long-term objective envisions multilevel substructure models of elevated transportation systems exemplified by the Hanshin Express Way, which exhibited dramatic multiple segment failure during the 1995 Kobe earthquake. Methodology:The proposed SPER software will be based on a combination of multilevel/multigrid, domain decomposition and incomplete nonlinear elimination methods. Roughly speaking, in these algorithms, (i) domain decomposition provides the parallelism, (ii) multilevel provides a scalable computing environment with respect to problem size and the number of processors on parallel computers, while (iii) incomplete elimination removes the sensitivity of the nonlinear solver to localized singularities. Relevance:Progressive degradation of RCS is a matter of great importance in earthquake engineering. The current design philosophy has moved to a performance-based approach which requires reliable assessment of the structural behavior beyond the elastic range. SPER is designed to simulate the seismic performance of existing RCS which have been built according to older and often non-conservative earthquake provisions, and to assist the development of rapid and cost-effective rehabilitation procedures. Outreach:SPER will be disseminated through a web site which will document the progress and outcome of the model-based earthquake simulation software of RCS. In the long haul, the intention is to eventually incorporate the 3-dim capabilities of SPER into the forthcoming NSF Network for Earthquake Engineering Simulation (NEES), and to develop therein an internet-based capability for earthquake simulations which may be used by colleagues in academia and the earthquake engineering community.Human Resources and Education:The exploratory research will involve three graduate research assistants from the Civil Engineering, Computer Science and Aerospace Engineering, respectively, which will be guided and supervised by the four Co-Pi's in three departments. They will work in an interdisciplinary environments that encompasses civil infrastructure systems, parallel computing technologies, and numerical solution schemes. The simulation platform SPER will be used as an education tool in a number of undergraduate and graduate courses that are being offered in the Civil Engineering Program at the University of Colorado, such as the Design of Reinforced Concrete Structures, Earthquake Engineering, and Computational Mechanics. SPER will also serve as a demonstration tool for public outreach, especially to high school teachers and K-12 students, on earthquake disaster awareness. This effort will take advantage of the new Integrated Teaching and Learning laboratory (ITLL) at the University of Colorado which has received national attention because of its novel approach to learning through discovery.