STABLITY PROBLEMS IN THIN WALLED BOX GIRDER BRIDGE

Abstract

The Box-Girder structural system has shown to be the most efficient structural solution for bridge decks., However the box section experience Stability related issues if being constructed using thin walled elements. Steel or FRP based Element are being used now a days, being high strength material thickness required to fulfil the strength consideration and constraints is very less resulting in thin walled element structures where the designs are mainly governed by stability requirements. As we increase the thickness of plate, stability will also increase but it results into a uneconomical design, so efforts are being made to reduce the thickness and increasing stability by introducing stiffeners. This study identifies the effects of different parameters which affects Buckling behavior of different elements of Box-Girder Bridge i.e. Flange and Web buckling. Over the past decades FRP laminated composites are gaining popularity as a structural element, being light weight it is easy to handle and transport leading to short installation times and speedy construction which is a major criterion during disasters. Also the quality of work is improved in terms of corrosion resistance, endurance limit, damage tolerance, aesthetic appearance, low maintenance, life retardancy etc. Reducing dead weight increases live load capacity of bridges without significant damage to existing superstructure, thus lengthening its service life. Further the flexibility they offer to tailor different properties of structural elements by altering fiber orientation, number of layer to achieve desirable strength and stiffness in the required direction has enhanced its usage. Because of their thin walls, they are frequently prone to buckling in a variety of modes. Many theories have been demonstrated to be accurate in forecasting deflection and to be overly accurate in predicting buckling loads. When designing thin walled box composite girders, the accuracy of the prediction of their stability limit state is of paramount significance due to the focus placed on obtaining an optimal ratio of weight to strength in current buildings. FRP box girders comprised of FRP stiffened panels are subjected to membrane compression (top flange), in plane shear (web), and membrane tension over their service life, respectively (bottom flange).Hence the use of laminated composite materials is aptly suited as they provide flexibility to designer to specify different material properties for different elements of beam cross-section.