Laser-welded corrugated core steel sandwich bridge decks
Doctoral thesis, 2020
Steel bridge decks are often used for applications when a lightweight structure is sought for. Conventional orthotropic steel decks suffers from drawbacks in several aspects, including high production costs and durability problems. Corrugated Core Steel Sandwich Panels (CCSSPs) have shown a good potential to become the next generation lightweight bridge decks with enhanced structural properties compared to its predecessor. The work presented in this thesis aims at verifying CCSSPs for bridge applications and to gain an increased understanding of their structural behaviour. Even though considerable research effort related to all-steel sandwich panels has been made, focus in previous work has been on web-core sandwich panels. Very little work has been devoted to corrugated core panels, particularly with reference to bridge deck applications.
In this work, a production process is presented for the novel CCSSP. Four demonstrator panels, of C-Mn and Duplex stainless steel are produced. The production-dependent geometric properties of the panel are measured, and it is concluded that the production process give good quality of the panel. Within the measured variation of the geometric properties, the impact of this variation on the fatigue-relevant stresses is studied using numerical analyses. As an example, the results show strong impact of the weld-width and possible misalignment of the welds.
Fatigue is a highly important factor for steel bridge decks and it has a strong relation to durability and strength requirements that are put on the deck. Here, the fatigue-strength of laserwelds in CCSSPs is assessed using experiments and numerical analyses. The results show alignment to other previously performed fatigue tests, and that with respect to the effective notch stress approach, the current recommendations given in design codes can be used, with a presented restriction. In addition to the small-scale cell specimens, a panel-specimen is also tested under fatigue loading. The results from this test demonstrate high fatigue-performance of the CCSSP.
To ensure that structural requirements concerning stiffness and strength are satisfied, reliable analysis methods are needed. To find an optimal bridge deck topology, and to run many loadcases, these analyses also needs to be time-efficient. In this thesis, two approaches with these targets are evaluated using numerical analyses. The results show that it is possible to accurately predict stresses using a deformation driven sub-modelling approach. Incorporation of the deformability of the weld region is shown to have a high impact on the state of stress in the welds, and a modelling technique is presented in this aspect. In addition, equivalent stiffness properties of CCSSPs are investigated and derived herein. A general conclusion from this work is that the results validate the feasibility of using CCSSPs for bridge deck applications.