STRENGTHENING OF PONTOONS OF RIBBON TYPE FLOATING BRIDGES

Abstract

The objective of this research work is to study the different techniques for strengthening the internal structure of pontoons of the ''ribbon-type'' floating bridges with an emphasis on increasing the ''load – carrying'' capacity of existing floating bridges. The research presented here is directed into two main approaches, the first approach is concerned with the strengthening of existing bridge pontoons through addition of structural elements, to increase their moment-carrying capacity. The newly designed pontoon bridges are analyzed in detail to determine their dynamic behavior under the effect of moving vehicles, with careful consideration of the additional weights imposed by the strengthening system applied to the pontoons. The second approach is mainly directed towards developing partial fixation between pontoons through modification of the pontoon connections, without any changes to the internal pontoon configuration. An extension is made to the analytical model already developed in previous research, for the determination of the dynamic response of floating bridges interactively with the moving vehicles. A new nonlinear element is proposed for the simulation of the newly proposed pontoon connections. A mathematical model is proposed to idealize the reaction of the underlying fluid, incorporating the proposed nonlinear element. A software package is developed using Microsoft Excel in connection with Visual Basic for the implementation of the mathematical model. An extensive parametric study is conducted for the determination of the effect of the main factors affecting the behavior of the strengthened pontoon bridges, including pontoon weight, fixation type, degree of partial fixation, and vehicle loads. The analysis results were used to develop conclusions and recommendations related to the practical strengthening of existing pontoon bridges. The effect of various strengthening strategies on the overall bridge load-carrying capacity are discussed in detail. Key words: Floating bridges - single pontoon analysis – torsional moment - eccentric loads – fluid-structure interaction – dynamic analysis