Parametric Assessment of Structural Behavior of Integral Abutment Bridge Approach Slabs When Subjected to Live Load and Thermal Effects

Integral abutment bridges (IABs) have gained increasing popularity in the United States owing to their relatively low cost, simpler construction, greater service life, and better seismic performance. However, elimination of the joints in IABs raises concerns about distress to the structural system induced by live loads and thermal effects. IAB approach slab cracking has been a frequent example of such distress in Illinois. This paper presents validated numerical simulations of IAB approach slabs in Illinois based on typical design and construction practices, as well as on 2.5 years of thermal effect conditions obtained from field monitoring of two instrumented IAB approach slabs. Various approach slab parameters, boundary conditions, and loadings are examined in the simulations. From this parametric study, it is suggested that such approach slabs would generally not be prone to cracking from truck live loads, although certain skews and widths can increase the chances of cracking. However, when an approach slab is subjected to the combined effects of low temperature and solar radiation, the principal stress can reach the concrete modulus of rupture - and its distribution confirms some crack patterns observed in the field, especially for highly skewed approach slabs. Increasing the slab thickness and/or releasing restraint at the approach slab-abutment interface may aid in mitigating structural distress from live load and/or thermal effects for IAB approach slabs in Illinois.