A review of literature and code formulations for cracking in R/C members

Abstract

Cracking in R/C members is a complex phenomenon characterized by high scattering, mainly affected by concrete in tensile zone. The aim of this paper is to evaluate the effectiveness of formulas for crack width prediction developed in last decades. First, an historical review of available literature models is presented and discussed. Second, the progress and missteps, which have characterized the development of international code provisions, are shown. Finally, a comprehensive comparison between predicted crack widths and experimental data is performed. Some formulas more than others provide mean values of crack width in good agreement with experimental data; nevertheless, predictions are always very scattered, as ratios between theoretical and experimental values have a coefficient of variation not lower than 30%. Results show that the prediction capacity does not necessarily increase as the cracking model is refined.

Quantification of crack prediction models in reinforced concrete under flexural loading

“…This high variation is indicative of the random nature of crack mechanisms and the resulting difficulties in modeling their behavior. The means and CoV's, as given in Table , for model uncertainty of EN 1992 and MC 2010 are comparable to those obtained by Lapi et al using maximum crack widths. Although there is some overlap in the large dataset used by Lapi et al (namely, Clark 1956 and Hognestad 1962) and that compiled for this study (Table ), the sources are largely independent, validating the short‐term flexure model uncertainty values obtained in this study.…”

“…In the design of structures such as LRS, the stabilized cracking phase is assumed to have been reached. The predicted maximum crack width corresponds to a 5% probability of exceedance by design code formulations, which may not probabilistically match the measured maximum crack width, thus contributing to model uncertainty.…”

“…Various researchers have reported on and compared numerous crack formulations which included design code formulations and improvements. For example, Borosnyόi and Balázs commented on over 40 proposed flexural crack widths models, while Lapi et al compared 30 flexural crack models, illustrating the extent of the debate. This is also indicative of a significant level of model uncertainty in crack models.…”

Predicting Crack Spacing of Reinforced Concrete Tension Members Using Strain Compliance Approach With Debonding

“…Oh and Kang (1987) suggested a semi-empirical equation, where crack spacing has been related to reinforcement axial strain and bar diameter. Lapi, Orlando, and Spinelli (2018) have carried out an exhaustive review on code formulations for cracking in concrete which revealed that various linear functions with c, s (reinforcing bar spacing) and φ/ρ ef as key independent variables were exceedingly dominant in most international codes. The comprehensive review of cracking equations builds on the previous work conducted by Borosnyói and Balázs (2005).…”

Special Issue: Interdisciplinary approaches for cement-based materials and structural concrete

“…Thus, cracking control relies on the proper calculation of steel stresses upon cracking, as well as on appropriate evaluation of crack widths. The code formulations to perform such calculations have evolved over time (Knoppik et al 2019;Lapi et al 2018), and there is an ongoing effort to develop improved design rules (Caldentey et al 2018). Two important open questions can be identified, which need to be addressed by new calculation methods.…”