A fracture mechanics-based method for prediction of cracking of circular and elliptical concrete rings under restrained shrinkage

Abstract

a b s t r a c tA new experimental method, utilizing elliptical ring specimens, is developed for assessing the likelihood of cracking and cracking age of concrete subject to restrained shrinkage. To investigate the mechanism of this new ring test, a fracture mechanics-based numerical approach is proposed to predict crack initiation in restrained concrete rings by using the R-curve method. It has been found that numerical results accord well with experimental results in terms of cracking ages for both circular and elliptical concrete rings, indicating that the proposed fracture mechanics-based numerical approach is reliable for analyzing cracking in concrete ring specimens subject to restrained shrinkage.

Effects of specimen size on assessment of shrinkage cracking of concrete via elliptical rings: Thin vs. thick

“…This self-restraint effect is enlarged in case of a closed shape such as the ring shape specimen in this study. The second part of the circumferential tensile stress caused by the central steel ring, can be calculated by applying a restraining pressure on the inner circumferential surface of a concrete ring [16]. Thus, the SIF caused by drying shrinkage (i.e.…”

“…In fact, due to geometrical effect, the radial deformation of the central restraining elliptical steel ring is not uniform along its circumference when concrete shrinks [15,16]. Therefore, it is believed that the uniform internal pressure assumption is not appropriate for elliptical ring specimens.…”

“…While in the conference paper, an elastic analysis was employed on thick concrete rings with the maximal tensile stress cracking criteria for concrete. A fracture mechanics-based analysis model and concrete cracking criterion are regarded to be more appropriate for analysing thick concrete rings [2,10,16]. (3) A deeper analyses on the restraining effect on thick concrete rings has been conducted in this paper, in which the restraining effects are separated into the following two parts: (a) circumferential self-restraint due to nonlinear moisture loss and therefore nonlinear drying restraint across a thick concrete ring wall; (b) external restraining effect along the radial direction from the central restraining steel ring.…”

“…The mechanism of the elliptical ring test has been largely unexplored since only Zhou et al [15] and Dong et al [16] have conducted research trying to figure out under which conditions the elliptical ring cracks earlier than circular ones. However, those studies only focused on thin rings.…”

“…Besides, in contrast with the fact that a crack may initiate anywhere in a circular ring specimen, for an elliptical ring specimen of a given geometry, it tends to be at a determinable position, reducing the resources needed for detecting crack initiation/propagation in the ring test. Therefore, elliptical ring specimens have been employed for assessing cracking tendency of cement-based materials as an improved ring test by some researchers [11][12][13][14][15][16]. However, most of those studies focused on investigating the effects of variations in material proportions/additives on the restrained shrinkage cracking of concrete or other cement-based materials.…”