An investigation of cracks caused by concrete shrinkage and temperature difference in common reinforced concrete bridge structures.

Cracking phenomena commonly occur in reinforced concrete structures of bridge and culvert components. While some bridge design standards, such as the AASHTO LRFD standard from America, allow for the presence of cracks, they do not provide direct quantitative limits on permissible crack widths. This research analyzes the crack formation mechanism of reinforced concrete structures under the influence of shrinkage and temperature loading, using the "tension-chord" model from the fib MODEL CODE. The research findings demonstrate that despite the steel reinforcement adequately arranged to resist shrinkage and temperature, as per American bridge design standards, cracks frequently occur with widths that may exceed the allowable limits specified in the fib MODEL CODE. The main reason is the inadequate control of concrete construction temperature, especially for large-sized concrete structures. Other findings are: with the same steel ratio, using small diameter reinforcement can significantly reduce the crack width compared to larger ones; Increasing the steel ratio can reduce the crack width but increases the susceptibility to cracking; Crack does not occur immediately after maintenance completion but after a period ranging from several days to several months; Crack width due to concrete shrinkage and temperature changes is typically 0.3mm but may reaches to 0.7mm due to high hydration heat of large sizes structures.