RILEM TC QFS ‘quasibrittle fracture scaling and size effect’-final report

Abstract

The report attempts a broad review of the problem of size effect or scaling of failure, which has recently come to the forefront of attention because of its importance for concrete and geotechnical engineering, geomechanics, arctic ice engineering, as well as in designing large loadbearing parts made of advanced ceramics and composites, e.g. for aircraft or ships. First the main results of Weibtlll statistical theory of random strength are briefly summarized and its applicability and limitations described. In this theory as well as plasticity, elasticity with a strength limit, and linear elastic fracture mechanics (LEFM), the size effect is a simple power law because no characteristic size or length is present. Attention is then focused on the deterministic size effect in quasibrittle materials which, because of the existence of a non-negligible material length characterizing the size of the fracture process zone, represents the bridging between the simple power-law size effects of plasticity and of LEFM. The energetic theory of quasibrittle size effect in the bridging region is explained and then a host of recent refinements, extensions and ramifications are discussed. Comments on other types of size effect, including that which might be associated with the fractal geometry of fracture, are also made. The historical development of the size effect theories is outlined and the recent trends of research are emphasized.

Confinement of FRP concrete columns: Review of design guidelines and comparison with experimental results

“…The difference between the unconfined compressive strength of a cylinder and the unconfined compressive strength obtained from the scaled columns could be due to the size effect phenomenon (62). It is widely accepted that the strength of concrete structures generally decreases as structure size increases (63)(64)(65)(66)(67).…”

Flexural fatigue of high-strength plain and fiber-reinforced concrete: influence of mesostructure and study of size effect

“…In other words, the heterogeneity of concrete implies a higher probability that larger specimens will contain defects that can accelerate material failure. This statistical theory of the size effect was initially proposed by Mariotte in the early 18th century, although it was Weibull in 1939 [76] who made a decisive contribution, proposing the so-called Weibull distribution to describe the phenomenon. Decades later, attempts to explain the size effect in concrete from the viewpoint of fracture mechanics began.…”

“…After the publication of Bažant's size effect law, new theories of the size effect emerged, also deterministic. However, in the mid-1990s Carpinteri put forward a theory based on fractals [76]. This researcher suggests that the process of crack formation and growth is conditioned by the fractal properties of the crack surface.…”