Analysis of the Deflection of Over-Truss Bridge Deck Using Finite Element Approach

Abstract

Deflection is basically the bend or curve that occurs within materials when loads are applied to them. A structure should be designed to be able to properly resist the applied loads and failure to do that makes the deflection visible and consequently lead to failure. During the course of this work the dead load, live load and environmental wind load acting on the bridge structure were calculated using the Analytical method and the calculated loads were used to analyze the bridge numerically using the STAAD pro software. The Plate stress animation from the STAAD software showed portions that were under intense loading on the concrete deck. From the animation, Steel beams 42, 45, 49, 53 and 57 were directly supporting these portions of the decks and were chosen for analysis. These beams were analyzed in terms of deflection, shear and bending. The values for shear, deflection, and bending for the five steel beams were compared under both approaches and their percentage difference was calculated. Comparing the results obtained from the analytical and numerical method gave a percentage difference of 4.39 %, 0.6 %, 0.93 %, 3.67 % and 1.19 % for shear, 6.29 %, 3.23 %, 1.07 %, 4.28 % and 1.14 % for bending, 12.5 %, 7.6 %, 4.08 %, 2.45 % and 2.6 % for deflection. 80 % of results obtained were less than 5 % in percentage difference and with this result, it is concluded that both methods are suitable for design. The Numerical method was nevertheless chosen to be a more economical and accurate method because it incorporates reliable safety factors that cater for uncertainties in its approach.