Measurement of Characteristic Length of Nonlocal Continuum

The characteristic length of a heterogeneous brittle material such as concrete represents a material property that governs the minimum possible width of a zone of strain‐softening damage in nonlocal continuum formulations or the minimum possible spacing of cracks in discrete fracture models. This length is determined experimentally. The basic idea is to compare the response of two types of specimens, one in which the tensile softening damage remains distributed and one in which it localizes. The latter type of specimen is an edge‐notched tensile fracture specimen, and the former type of specimen is of the same shape but without notches. Localization of softening damage is prevented by gluing to the specimen surface a layer of parallel thin‐steel rods and using a cross section of a minimum possible thickness that can be cast with a given aggregate. The characteristic length l is the ratio of the fracture energy (i.e., the energy dissipated per unit area, dimension N/m.) to the energy dissipated per unit vo...