Structural Characterisation of the Failed Manafwa Historic Bridge in Uganda

Abstract

A visual inspection was carried out on thetwo-spanManafwa River Bridge along Mbale - Tororo Road to assess the extent of damage caused by traffic to the bridge superstructure. The superstructure slab developed a hole between two longitudinal steel beams located adjacent to the carriageway centreline on the Mbale bound lane on the Tororo span. At the time of inspection, the maximum length of opening parallel to traffic flow direction was 2530mm and was 1350mm in the normal direction. There is noticeable cracking of the deck surfacing at acorresponding location on the Mbale span. This report has a detailed analysis of the superstructure and the proposed research undertaken entailed the structural characterisation survey of the Manafwa Bridge which has recently shown signs of failure and for structural integrity comparisons evaluated using a finite element analysis method, ANSYS. In summary, the existing slab needs top reinforcement to resist hogging moments over longitudinal beams and at cantilever footwalk edges. The existing bottom reinforcement is adequate for sagging moments and punching shear requirements. The shear capacity of the longitudinal steel beams is satisfactory and can sustain loads greater than the combination of HA and HB37.5.