Study on concrete infilled tubes as compression members in truss type light vehicular bridges

Abstract

Applicability of concrete filled steel tubes (CFST) for compression members in truss type steel light vehicular bridges is studied in this research as an economical solution for the lack of light vehicular bridges in Sri Lanka. There are many places in Sri Lanka where people have to travel long distance to cross rivers or access the nearby city for their day to day needs. CFST is a composite material which is getting more popular in the civil engineering industry. So, it is important to examine the properties of CFST as a composite material. The use of CFST in truss bridges has several advantages such as deflection reduction of the bridge, improved seismic performance, improved load carrying capacity, dynamic performance, and cost reduction. To achieve an economical structural performance, CFST section has to be designed properly. Optimum positions to use CFST have to be identified depending on the truss type. Replacing larger steel I sections with CFST will reduce the cost since the same amount of force can be carried out with less steel amount in CFST. Also, the tendency to local buckling is reduced when thinner sections are filled with concrete. Therefore, to achieve a higher span with a lesser cost (steel tonnage), usage of CFST sections for compression members have been accessed in this study. Also, the tendency to local buckling was examined with experimental and numerical simulations. Hence first, a desk study was carried out focusing Gin Ganga area to identify the problems in the area due to lack of bridges. Two experimental model bridges were tested in this study as one with only hollow aluminium tubes and other with cement grout filled in selected top chord members. Using a real scale numerical simulation of a CFST bridge model, practical applicability and cost figures were compared with a conventional steel truss bridge.