Dynamic Response Calibration of Hybrid Floating Bridge System Using Rayleigh Damping

Abstract

Floating bridges are efficient and rapid solutions in crossing water gaps when the conditions are not suitable or economic for the construction of other conventional bridge systems. Using floating bridges is promoted to be a good solution in various applications such as rapid disaster relief, military gap crossing operations, and connecting lifelines of cross-shore territories. However, design and analysis of floating bridges are challenging engineering tasks where various factors have to be considered such as water structure interaction, wind, and different traffic loading cases. Moreover, inherit structural damping is another concern to simulate the structural energy dissipation and capture to a considerable limit the bridge dynamic behavior. In this study, the Rayleigh damping method is used to calibrate the dynamic structural behavior of a ribbon floating bridge system. The floating bridge is composed of the assembly of three different floating bridge structures: The Heavy Communication Bridge (HCB), the assault floating bridge (PMM71), and both are connected using a pontoon unit named New Connection Pontoon (NCP). The NCP is fully manufactured of steel sheets and sections and developed to integrate a traffic line through connecting the HCB and PMM71. The whole bridge assembly is subjected to tracked tank load of Military Loading Class of 70 tons (MLC70). Due to the request for rapid and reduced assembly time, a Hybrid NCP (HNCP) is redesigned of FRP composite laminated sheets and a steel skeleton to minimize weight. A 3D numerical model is developed of the full floating bridge system solution PMM71, HNCP, and HCB using ANSYS FE Package. The dynamic structural response is captured at two tracked passing vehicle speeds, 8 km/h and 16 km/h. A modal analysis is performed to quantify the cumulative bridge mass participation, mass, and stiffness Rayleigh factors based on the cyclic frequency values. The baseline steel NCP dynamic structural draft values are calibrated using the Rayleigh method and validated with experimental results. Furthermore, the structural response of the full-bridge system involving the HNCP is investigated. The obtained results showed the difference in draft values between the steel NCP and the experimental values are minimized to reach 3.88% and 4.8% for 8 km/h and 16 km/h vehicle speeds, respectively. A comparison between draft values obtained for the baseline steel NCP and HNCP is performed. The results showed an improvement of the draft values by 3.8% and 3.69% for 8 km/h and 16 km/h vehicle speeds, respectively. The numerical model is concluded as a promising model for studying the structural behavior of a fully composite laminated floating bridge system.