Influence of Fracture Surface Roughness Characteristics on the Specific Fracture Energy of Concrete as a Function of Specimen and Aggregate Size

9713997 Perdikaris通过研究断口表面的粗糙度特征，如表面粗糙度指数、分维和波长含量，来评价微观尺度和混凝土抗压强度对单位裂缝面积断裂能的影响。本研究的主要目的是：a)在CMOD控制下对三种最大骨料尺寸和三种混凝土抗压强度的三种尺寸的混凝土梁试件进行三点弯曲试验，并确定断口表面的粗糙度特征，即每个断口的粗糙度指数、分维和傅立叶幅值谱；b)研究断口表面的粗糙度特征，评估它们与最大骨料尺寸和混凝土抗压强度的关系及其对“荷载-荷载-点-位移”响应和比断裂能的影响。C)开发基于细观力学的半经验分析，其中表观韧性将根据所观察到的裂纹路径和集料尺寸的给定粗糙度特征来计算。这项研究计划将通过大学-州-行业合作进行。研究结果将改进普通混凝土和高强混凝土性能的规范和评价方法，从而提高设计的效率。

9713997 Perdikaris The influence of the microscale and concrete compressive strength on the fracture energy per unit crack surface area will be evaluated by studying the roughness characteristics of a fracture surface, such as the surface roughness index, fractal dimension and wavelength content. The major objectives of this research are: a) to perform 3-point bending tests under CMOD control on concrete beam specimens of three sizes with three maximum aggregate sizes and three concrete compressive strengths and determine the roughness characteristics of the fracture surfaces, that is the roughness index, fractal dimension, and Fourier amplitude spectra for each fracture surface b) to study the roughness characteristics of the fracture surfaces and to evaluate their dependence on the maximum aggregate size and concrete compressive strength and their influence on the "load vs. load-point-displacement" response and the specific fracture energy. c) to develop a micromechanics-based semi-empirical analysis, wherein the apparent toughness will be calculated based on the given roughness characteristics of the observed crack paths and aggregate size. This research program will be undertaken through a university- state-industry collaboration. The results will improve the methods of specification and evaluation of the performance of normal and high strength concrete resulting in more efficient designs.