CFRP strengthening of reinforced concrete pontoon walls against ship bow collisions

Abstract

Reinforced concrete (RC) pontoons have been widely used as floating foundations to support various structures. However, pontoons are under the threat of accidental collisions from passing ships and service vessels. To ensure the integrity of pontoons and the supported structures in a collision accident, special strengthening techniques may be required to increase the impact resistance of the pontoons. Carbon fibre reinforced polymer (CFRP) composites have been extensively used in strengthening RC structures under blast and impact loads. However, the effectiveness of CFRP strengthening of RC pontoons against ship collisions has not been investigated. In this study, CFRP composites are used to strengthen RC pontoon walls against ship bow collisions. It is observed that while CFRP-strengthened pontoon walls still experience punching shear failures as the normal RC pontoon walls, the wall damage is nonetheless significantly reduced. With the strengthening of 4 mm CFRP sheet, the impact resistance of the pontoon wall is increased by 5-10% depending on the pontoon wall thickness. An analytical method for calculating the punching shear capacity of CFRP-strengthened RC pontoon walls is also proposed based on the critical shear crack theory. The method significantly reduces the computational efforts and can be used in the preliminary design phase.