Influence of locked-in girder stress on the design of suspension bridges

A fundamental assumption used in designing suspension bridges is: under the total dead load on the bridge the cable is parabolic and the stiffening girder is unstressed at mean temperature. Since the total dead load includes self-weight (DL) and superimposed dead load (SDL), the assumption implies that the SDL should be applied before stiffening girder has become integrated with the main cable, otherwise the stiffening girder will be stressed. The stress in stiffening girder due to SDL is thereafter referred to as locked-in girder stress. How to calculate the locked-in girder stress? Should it be considered in design? To answer these questions is the objective of this paper. First, an iteration algorithm is developed to determine the locked-in girder stress, and then results of two case studies are presented. The first case is Tsing Lung Bridge which has been recently designed, and the second one is The Second Tacoma Narrows Bridge which is currently under rehabilitation construction. The conclusion drawn from this study is: for either new design or rehabilitation evaluation, the locked-in girder stress is too significant to be ignored.

• Abstract

• Introduction

• Numerical Solution

• Case Studies

• Results and Discussions

• Conclusions

• References