Laser-welded corrugated core steel sandwich panels for bridge application

Licentiate thesis, 2017

The design of steel bridge decks has remained unchanged since the introduction of orthotropic decks. Orthotropic decks are expensive to produce, mainly due to high labor-costs. Furthermore, several joints (within the deck and between the deck and the surrounding structure) are highly fatigue sensitive, and the deck has a low stiffness in the transverse direction (i.e. perpendicular to the longitudinal stiffeners). This has in many cases led to premature deterioration and high maintenance costs. This thesis has a focus on laser-welded corrugated core steel sandwich bridge decks that have an increased stiffness-to-weight ratio and a more industrialized production with less complex detailing compared to conventional orthotropic steel decks. These enhancements lead to a more attractive solution with respect to economic and environmental sustainability. Structural analysis of a three-dimensional corrugated core sandwich panel using numerical methods is computationally heavy. In particular, the structural behavior of such panel in the transverse direction is rather complex. For that reason, this thesis is aimed at developing methods for simplified analysis incorporating homogenized beam and plate theories. Focus is put on predicting the stiffness and load effects in the direction transverse to the corrugation. A second aim of this thesis is to investigate the impact of variation of the production-dependent geometric parameters of the core-to-face joints of corrugated core steel sandwich panels on fatigue-relevant stresses in the vicinity of the laser stake welds. In order to utilize a simplified approach for static analysis of a corrugated core steel sandwich panel, a new analytical formulation for the transverse shear stiffness in the weak direction of the panel is presented in this thesis. To ensure that this stiffness property yields accurate predictions, the rotational rigidity of the weld region is simulated by a rotational spring. The magnitude of this spring is determined by a closed-form solution based on numerical and regression analyses. Both the transverse shear stiffness and the rotational spring is verified by numerical analyses and experiments. Furthermore, the impact of the variation of the production-dependent parameters is studied in this thesis by an extensive parametric study incorporating two-dimensional continuum numerical models. Numerical results are presented and discussed in detail. As an example, the parametric study shows that a misalignment between the weld-line and core direction can lead to a large increase of the fatigue-relevant stresses.