Identification of the Influence of Concrete Cover Thickness and ∅/ρ Parameter on Crack Spacing.

Abstract

Cracks due to the service load in the reinforced concrete structures are controlled at the design stage, by limiting the calculated crack width. Widely used crack width calculation models (Eurocode 2 and Model code 2010), estimates the crack width by multiplying the crack spacing with the mean strain difference of concrete and reinforcement. Concrete cover thickness and the ratio of diameter to reinforcement area to effective tensile area of concrete (∅/ρp,ef) are the two main crack spacing governing parameters in the aforementioned models. The existing models are mostly applicable when concrete cover thickness is within the specified limit. For example, Model Code 2010 model limits the concrete cover thickness to 75 mm. In order to identify the influence of aforementioned two governing parameters on crack spacing, the results of recent experiments have been considered. According to some recent studies, it is found that the concrete cover thickness has a significant influence and the ∅/ρp,ef parameter has a negligible effect on crack spacing. To investigate the reasons why the ∅/ρp,ef parameter has a negligible effect on crack spacing, the involvement of bond properties is needed to study. Some authors have specified that the large diameter bars consist of higher bond force per unit surface area than the small diameter bars, due to the high rib area. Due to this reason, the similar bond behavior could be identified, from low number of large bar diameters and high number of small diameter bars. A literature review has been carried out to study the bond behavior on specimens subjected to pure tension. With the facts and available data, it is further verified that the ∅/ρp,ef parameter has a negligible influence and concrete cover thickness has a significant effect on crack spacing.

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