Influence of concrete shrinkage on crack widths in reinforced concrete members under direct loading

Under long-term loading, crack widths in reinforced concrete members increase due to the time-dependent material behaviour of concrete. While many crack width approaches neglect shrinkage in crack width calculations, investigations in the literature indicate that shrinkage strains should be taken into account for crack width calculation. In order to classify the individual effects of shrinkage, bond creep and concrete creep on the crack pattern, they were analysed separately under -direct loading. For this purpose, a parameter analysis was performed in the stabilized cracking stage with a rheological model validated by experimental tests to determine the proportion of concrete shrinkage on crack width increase. A comparison with the crack width approach of Model Code 2010 shows that the approach of Model Code 2010 is potentially well suited to describe time-dependent effects realistically, but overestimates them. For this reason, the approach was modified without fundamentally changing the established crack width formula. With that modification, very good results were achieved in a further comparison.