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Title: Assessment of Crack Spacing and Crack Width Formulations in RC Elements Externally Strengthened with FRP Materials

Author(s): C. Barris, F. Ceroni, A. Perez Caldentey

Publication: Symposium Paper

Volume: 360


Appears on pages(s): 691-708

Keywords: Reinforced Concrete (RC), Beams, Ties, Fiber Reinforced Polymer (FRP), EBR, NSM, Crack width, Crack spacing.

DOI: 10.14359/51740657

Date: 3/1/2024


Serviceability checks in Reinforced Concrete (RC) elements involves the verification of crack width mainly aimed to limit the exposure of the steel reinforcement to corrosion and chemical attack and, thus, improve durability. Classical approaches for assessing the crack width in RC elements provide the calculation of two terms: 1) the average crack spacing, and 2) the average difference between the strain in the steel reinforcement and in the concrete in tension referred to the average crack spacing. A similar approach can be assumed valid also for RC elements strengthened with externally bonded Fiber Reinforced Polymer (FRP) materials, taking into account the additional tension stiffening effect provided by the external reinforcement.

This paper presents the comparisons of some existing code formulations for predicting crack spacing and crack width in RC elements with the experimental results of a database collected by the Authors and concerning tests on RC beams and ties externally bonded with different types and configurations of FRP materials. The paper is mainly aimed to check the reliability of the existing equations provided by codes in order to address the future assessment of reliable design provisions for cracking verifications in RC elements strengthened with FRP materials. The comparisons have evidenced, indeed, some useful issues for the design provisions: 1) larger scatter in the predictions of crack width than in crack spacing and, in particular, for ties, 2) limited effect of shrinkage on crack width, 3) necessity of taking into account the external reinforcement in crack spacing formulations, 4) good reliability of mechanical models for calculating cracks width.