题目：冻融混凝土结构的微结构损伤演变及对其力学和断裂行为的影响

Microstructural damage evolution and its effect on mechanical and fracture behavior of freeze-thawed concrete

报告人：Professor Lizhi Sun

时间：2018.9.19周三下午四点到五点半

地点：西六楼五楼报告厅

邀请人：陈志军 教授

主讲人简介：

Bio: Dr. Lizhi Sun is Professor in Department of Civil & Environmental Engineering at University of California, Irvine (UCI). His primary area of research is the micromechanics of heterogeneous composite materials, with applications in civil, mechanical, and aerospace engineering. He has published more than 190 papers including 95 peer-reviewed journal papers in the field of mechanics and materials. He wins academic and research awards such as Fellow of AAAS (2017), Fellow of ASCE’s Engineering Mechanics Institute (2014), UCI Civil and Environmental Engineering Professor of the Year (2013), AFRL Faculty Fellow (2011), UCI School of Engineering Fariborz Maseeh Best Faculty Research Award (2008), and Honda Research Initiation Award (2006). Dr. Sun is an editor for International Journal of Damage Mechanics and an associate editor for ASCE’s Journal of Engineering Mechanics and Journal of Nanomechanics and Micromechanics. He has organized more than 50 symposia for various societies and served as a reviewer for more than 70 journals and 10 funding agencies (e.g. NSF, NIH, and DoD). Dr. Sun has been the technical committee chair for ASCE-EMI Committee on Inelasticity Modeling and Multiscale Behavior (2009-2011), ASCE-EMI Committee on Nanocomposites (2012-2013), and ASCE-EMI Committee on Nanomechanics and Micromechanics (2014-2017).

内容摘要：

Abstract: Concrete structures in cold regions are exposing to cyclic freezing and thawing environment, leading to degraded mechanical and fracture properties of concrete due to microstructural damage. We combine the X-ray nano-CT technology and micro-scale cohesive zone model to investigate microstructural damage evolution and its effect on elastic and fracture behavior of freeze-thawed concrete materials. A two-level micro-to-macro scale finite element model is developed based on CT microstructural images with microcracks due to freeze-thaw cycles. The macroscopic load-deflection curves and fracture energies are simulated and compared favorably with experimental results. Simulation results demonstrate that microcracks caused by freeze-thaw actions are the primary reason for degradation of concrete mechanical properties. Fracture behaviors of frost-damaged concrete with different mortar and interfacial transition zone strength and fracture constants are also simulated and discussed. The combined X-ray nano-CT technology and cohesive zone model proposed is effective in characterizing fracture behavior of concrete and capturing freeze-thaw cycle-induced microstructural damage evolution and its effect on fracture process of concrete.