Linear and non-linear FE-analysis of cracking behavior of wing walls in integral bridges

Sammanfattning: Wing walls on slab frame integral bridges has traditionally been designed for mainly earth pressure and its self-weight. It has also been designed separately from the rest of the bridge. Traditionally no 3D effects have been considered in the design of the wing walls. The Swedish Transport Administration (Trafikverket) have recently introduced regulations stating that 3D effects must be considered when designing wing walls, which means that the wing wall no longer can be designed separately from the rest of the bridge. This leads to an introduction of membrane forces in the wing wall which in turn leads to an increase of the required amount of reinforcement. This master’s thesis investigates the governing parameters that affect the magnitude of these membrane forces and where they arise in the wing wall. A parametric study is conducted where the goal is to present a relationship between the magnitude of the membrane forces and the height and length of the wing wall. This part is analyzed using linear FE modeling. Furthermore, the master’s thesis also investigates how the membrane forces affects the crack width in the Service Limit State (SLS) of the wing wall. Wing walls that are designed according to the traditionally procedure are analyzed together with applied membrane forces acting on the wing wall. The cracking behavior of the wing wall is checked for long-term loading with an established non-linear FE modeling considering bond-slip and crack propagation in reinforced concrete. The model is validated against an experiment of a deep beam and shows sufficient accuracy regarding crack spacing and conservative crack widths for lower loads. The results from the linear analysis states that membrane forces cause extra amount of longitudinal reinforcement in the corner of the wing walls. The parametric study indicates a tendency for a higher amount of reinforcement needed due to the membrane forces for smaller wing walls. The parametric study also indicates that for smaller wing walls the membrane forces are of greater importance since they constitute for a greater part of the total applied load. For larger wing walls the earth pressure and the self weight gets more dominant and hence the membrane forces constitute for a lesser part of the total applied load. The result of the non-linear analysis is in some way contradictory. It indicates that the membrane forces for short and low wing walls are of lesser problem in SLS, but for short and high wing walls the membrane forces are of higher importance. The opposite was found in the linear design.