High Temperature Effects on Concrete Materials: A Multiscale Approach

摘要本研究的重点是与火灾安全相关的高温效应。该项目包括：（a）对从普通混凝土到高性能（低渗透性）混凝土的不同水灰比的混凝土试样进行高温试验;（B）在宏观和微观观测尺度上对相互作用的机械和环境退化过程进行计算机模拟。多尺度方法将采用硬化水泥浆水平上的多相材料的微观力学和局部-全局有限元策略来模拟和放大混凝土的非均匀细观结构，其中骨料颗粒通过零厚度的粘性界面单元与相邻的水泥浆相互作用。应用将包括混凝土试样的耐火性研究，这些材料承受高温火灾和同时的机械载荷，从变温下的热蠕变效应，到孔隙压力与湿度驱动的热收缩，以及考虑热降解和机械降解耦合的复合材料损伤的微观力学过程，将讨论一些基本问题。数值模拟器将提供一种工具来设计和优化混凝土的成分，并评估国家的混凝土基础设施对火灾危险的脆弱性。数值模拟平台将被用作一个新的本科材料课程的教育工具，该课程将在科罗拉多大学土木工程专业提供。基于PC的混凝土模拟器也将作为一个演示工具，为公众宣传，特别是高中教师和K-12学生，利用新的综合教学和学习实验室在科罗拉多大学的材料意识，已收到全国的关注，因为它的新方法，通过发现学习。混凝土数值模拟器将通过一个网站传播，该网站将记录一般混凝土和颗粒复合材料的基于模型的材料模拟软件的进展和结果。

AbstractThe proposed research focuses on high temperature effects related to fire safety. The project includes (a) high temperature experiments on concrete specimens with different w/c ratio ranging from normal to high performance (low permeability) concretes, and (b) computational simulations of interacting mechanical and environmental degradation processes at the macro- and meso-scales of observation. The multi-scale methodology will employ micro-mechanics of multi-phase materials at the level of the hardened cement paste and local-global finite element strategies to model and upscale the heterogeneous meso-structure of concrete where aggregate particles are interacting with a contiguous cement paste through cohesive interface elements of zero-thickness.Applications will include studies of the fire resistance of concrete specimens, which are subjected to high temperature fire scenarios and simultaneous mechanical loading.A number of fundamental questions will be addressed, starting from transitional thermal creep effects under variable temperatures, to pore pressure- vs humidity-driven thermal shrinkage, as well as micro-mechanical processes of composite damage considering coupling between thermal and mechanical degradation. The numerical simulator will provide a tool to design and optimize the constituents of concrete and to assess vulnerability of the nation's concrete infrastructure against fire hazards.The numerical simulation platform will be used as an educational tool in a new undergraduate materials course that will be offered in the Civil Engineering Program at the University of Colorado. The PC-based concrete simulator will also serve as a demonstration tool for public outreach, especially to high school teachers and K-12 students, on material awareness taking advantage of the new Integrated Teaching and Learning Laboratory at the University of Colorado which has received national attention because of its novel approach to learning through discovery. The numerical concrete simulator will be disseminated through a web site which will document the progress and outcome of model-based material simulation software for concrete and particulate composites in general.