Statistical analysis of existing models for flexural strengthening of concrete bridge beams using FRP sheets

This paper performs a statistical analysis of previously proposed models for resisting the debonding of FRP sheets used in strengthening reinforced and prestressed concrete beams. End debonding and intermediate crack-induced debonding modes of failure are studied for beams in flexure. Two different databases are assembled from published experimental debonding tests on concrete beams of different span lengths. The first database contains the results of four point bending tests performed to study the behavior of the FRP-concrete bond at the end of the FRP sheet. The second database which includes four point bending tests, three point bending tests and one point loading tests, has been created to examine intermediate crack-induced debonding. These two databases are significantly larger than those used in developing any of the existing debonding strength models and provide a solid basis for assessing the performance of such models. A regression analysis reviews the relationship between the experimentally measured loads that caused debonding to the model predicted values as well as the bias and the variability in the prediction models. This regression analysis allows for drawing conclusions on the most appropriate and accurate models, from a statistical point of view, that may be used in a follow up reliability-based calibration of partial safety factors. The applicability of such information for the development of design specifications for strengthening of deteriorated concrete bridges is highlighted. This will be implemented in a forthcoming companion paper.