A study of externally reinforced fibre-reinforced concrete bridge decks on steel girders

A concrete slab acting compositely with steel girders is commonly an economical solution for short and medium span highway bridges. A severe maintenance penalty exists for such a system in areas where the use of de-icing chemicals is prevalent, largely due to the corrosion of embedded steel reinforcing bars and the attendant concrete degradation. Transverse steel straps, placed below the concrete slab, eliminate the deleterious effects of corrosion on the concrete and allow improved access for routine maintenance.;A static testing program, initiated in 1994, has been undertaken at DalTech on a full-scale externally restrained fibre reinforced concrete (FRC) bridge slab. This program includes three series of destructive tests.;The failure pattern observed at the ultimate load in each test can be characterized as a punching shear mechanism, with localized damage. The results of static tests obtained from a full-scale laboratory model of an externally reinforced FRC deck supported on longitudinal steel girders are presented.;The major contributions of the work are summarized as: (1) Design of a full-scale externally reinforced FRC bridge superstructure to be used for experimental testing to establish the relationship between the degree of external restraint and the system ultimate capacity. (2) Refinement of an analytical model that can be used to predict the load-deformation response and the ultimate punching load of a restrained FRC deck slab acted upon by a concentrated load. In particular, the external transverse restraint is represented in the analytical model and the failure criterion for concrete in a triaxial stress field was revised. (3) Comparison of the measured response of an intact externally restrained FRC slab with the predicted behaviour based on the refined analytical model was made for varying degrees of external restraint. (4) The degree of external restraint that is required to assure a punching failure mechanism in an externally restrained FRC acted upon by a concentrated load was optimized on the basis of system weight and safety. (5) The residual system capacity inherent in a deteriorated section of an externally restrained FRC bridge slab was also investigated. The measured capacities for two deteriorated sections are presented and compared with analytical predictions. (6) Deck repairs were undertaken to locally restore the deck capacity at punched locations. From this work, a recommended repair procedure is presented that was demonstrated to restore 75% of the system capacity of a "punched" concrete slab. (Abstract shortened by UMI.).