Modeling of RC/SRC Systems with Flexibility-Based Models

9520282 Spacone本项目的主要目标是为组合框架的非线性静力和动力分析开发一套现实的模型。对复合材料结构性能的全面理解仍有待实现。组合构件的受力行为涉及钢与混凝土在循环荷载作用下的局部粘结转移等复杂现象。理解和模拟这一行为的能力对于评估现有的民用基础设施系统以及设计新的结构非常重要。基于结构分析的柔度法，提出了一种新的框架单元列式：该列式能有效地模拟钢筋混凝土框架在地震作用下的非线性反应。与传统的刚性配方相比，新配方有几个优点。新公式将用于建立组合梁和型钢混凝土柱的新杆件模型。这些模型将考虑钢与混凝土在大变形情况下的局部粘结效应。它还将同时考虑非线性材料和几何效应。为了更好地了解组合柱的性能，并对新的分析模型进行校准，将对型钢混凝土柱进行一系列小型试验。建议的模型将通过一系列相关性测试，使用先进的识别-优化技术进行验证。最后，进行了小比例组合框架在拟静力循环荷载和输入地震动作用下的参数试验。本项目中研究的基于灵活性的模型将导致对现有民用基础设施系统的健康状况和安全状况进行可靠的评估。新模型可以作为一种研究和实用工具，以更好地了解组合框架的复杂行为，最终可以导致改进设计程序的发展。这是一个在民用基础设施系统倡议NSF 94-145的第一年计划下支持的项目。***

9520282 Spacone The main objective of this project is to develop a set of realistic models for the nonlinear static and dynamic analysis of composite frames. A full comprehension of the behavior of composite structures is still to be achieved. The behavior of composite members involves complex phenomena such as the partial bond transfer between steel and concrete subjected to cyclic loadings. The ability to understand and model this behavior is important for the evaluation of existing civil infrastructure systems as well as for the design of new structures. A novel frame element formulation based on the flexibility method of structural analysis will be made: The new formulation is effective in modeling the nonlinear response of reinforced concrete frames subjected to seismic inputs. The new formulation offers several advantages over classical stiffness formulations. The new formulation will be applied to formulate new member models for composite beams and SRC columns. These models will include the effects of partial bond between steel and concrete under large element deformations. It will also consider both nonlinear material and geometric effects. A small series of experimental tests on SRC columns will be performed to better understand the behavior of composite columns and to calibrate the new analytical models. The proposed models will be validated through a set of correlation tests, using advanced identification- optimization techniques. Finally, a set of parametric tests on small scale composite frames under both quasi-static cyclic loadings and input ground motions will be conducted. The flexibility-based models investigated here in this project will lead to a reliable assessment of the state-of-health and safety of existing civil infrastructure systems. The new models can be used as a research and practical tool for attaining a better understanding of the complicated behavior of composite frames, wh ich can eventually lead to the development of improved design procedures. This is a project supported under the year 1 program on the Civil Infrastructure Systems initiative NSF 94-145. ***