Shipping Container Impact with Bridge Girders
Master thesis
Permanent lenke
https://hdl.handle.net/11250/2786256Utgivelsesdato
2021Metadata
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Sammendrag
Aluminium bridge decks have been proposed as alternatives to traditional steel bridgedecks. These girders can meet all design criteria for bridges and have the advantagesof low density and high corrosion resistance. Regardless of girder material, one criticalissue in bridge design is to ensure the safety of bridge girders under accidental shipcollisions. Such collision accidents can occur in earthquake or tsunami inundation, due toship maneuvering errors or mechanical failures. The bridge girder strength against shipcollision load should be carefully checked to avoid large local damage in the impactedregion and further degradation of global bridge safety. Some studies have been conductedfor ship deckhouse and forecastle impacts with bridge girders. However, bridge decksare also under the impact of stacked shipping containers from cargo ships. Consideringthe lower elastic modulus and ductility of aluminium material compared with steel,aluminium bridge girders may be more vulnerable to collision loads.The thesis work is divided in two parts. The first aims to numerically investigate thelocal structural response of bridge girders under shipping container impacts for steel andaluminium girders. FE- Models of a bridge section and a 20 ft standard shipping containerare developed in LS-DYNA. The strain rate effect of the aluminium girder is investigated. Theimpact force, structural damage, and energy dissipation during the collision are comparedfor both materials. The effects of impact angle and vertical location are also discussed.The second part of the work aims to numerically investigate the global response of thebridge by using the obtained force-displacement relationship from the shipping containerimpact. A global model has been built in Orcaflex. Eigenmodes, moments about the strongand weak axis as well as bridge motions have been discussed. The conclusions from thelocal analysis (published as an article) were that strain rate had a minor effect on theinvestigated aluminium alloy. In addition, a significant reduction of contact force wasobserved for the aluminium girder due to local fracture leading to larger dissipation ofstrain energy. For some head-on collision scenarios, the girder material seemingly playsa lesser role as long as the stiffness is sufficient to redistribute the impact force over alarger area. The majority of energy dissipation was observed in the shipping containers.For the global analysis, there was significant development of strong axis bending momentand the dynamic displacement was less than expected. The period of the motions post-impact was close to one of the eigen-periods. It should be stated that the modal analysisdid not correlate satisfactorily with the NPRA’s existing reports, which would questionthe validity of results in this part.