High Temperature Effects on Concrete Materials: A Multiscale Approach

摘要拟开展的研究重点是与消防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)混凝土的不同水灰比混凝土试件进行高温实验，以及(B)在宏观和细观尺度上对相互作用的力学和环境退化过程进行计算模拟。多尺度方法将在硬化水泥浆体水平上使用多相材料的微观力学和局部-全局有限元策略来模拟和提升混凝土的非均匀细观结构，其中骨料颗粒通过零厚度的粘结界面元素与连续的水泥浆体相互作用。应用将包括研究混凝土试件的耐火性，这些混凝土试件承受高温火灾场景和同时的机械载荷。从变温下的过渡热徐变效应到孔压和湿度引起的热收缩，以及考虑热降解和机械退化耦合的复合材料损伤的细观力学过程。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科罗拉多大学土木工程专业开设的一门新的本科材料课程的教育工具。基于PC的混凝土模拟器还将作为公共宣传的示范工具，特别是对高中教师和K-12学生，利用科罗拉多大学新的综合教学和学习实验室的材料意识，该实验室因其在发现中学习的新颖方法而受到全国关注。混凝土数值模拟器将通过一个网站传播，该网站将记录基于模型的混凝土和颗粒复合材料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.