Slab Cracking Control in Continuous Steel-Concrete Bridge Decks

This paper presents a study on the effectiveness of various casting techniques used to control slab tensile stresses during the construction of continuous steel-concrete composite bridge decks. The main features describing the early age behavior of concrete are outlined and available modeling options are considered. A practical procedure is presented for the evaluation of the slab stress state taking place at various construction stages based on the modular ratio approach suggested by Eurocode 4. The method, which can be implemented using commercial software, requires the evaluation of suitable modular ratios and creep coefficients to estimate the time-dependent effects of the concrete slab weight and the thermal, endogenous, and drying shrinkage components. This simplified procedure is then applied to a case study to evaluate, for various casting sequences, the contributions of the concrete weight and shrinkage components to the slab early cracking. Finally, the efficiency of various casting techniques in controlling the slab tensile stresses is presented and discussed.