Dynamic Analysis of a FRP Deployable Box Beam

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Landherr, Johanna
bridge , dynamics , FRP , deployable
Fibre reinforced polymers (FRPs) are currently being used in new bridge construction as a feasible alternative material for corroded bridge deck replacements, footbridges, and emergency vehicle bridges. For both military and civilian applications, there exists a need for bridges that are lightweight and inexpensive, that can be readily transported and easily erected. The 10 m glass FRP deployable box beam presented in this thesis was developed to aid cross-country mobility in areas where infrastructure has been damaged by conflict or natural disasters. The box beam represents one trackway of a dual trackway system. The quasi-static and dynamic behaviour of the box beam was investigated under laboratory and field conditions. Quasi-static tests were conducted to ensure the strength of the steel hinge, the hinge connection to the base plate of the box beam, and the overall box beam would support the vehicle loads in field testing. Data from these tests were used to validate the finite element model. Field testing was conducted to investigate the natural frequencies of the box beam, calculate the dynamic increment of the structure, and confirm the validity of the finite element model created in Matlab. Three vehicles were used to evaluate the response of the box beam to different types of suspension, loads, and number of wheels per trackway. A finite element model was developed to predict the displacement of the bridge under various vehicle loads. The analysis resulted in displacement contours within a reasonable amount of error when compared to those measured in field testing. Recommendations for future research and development of the structure are provided based on this research.
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