Abstract
This report summarizes the assessment carried out as a result of the public uproar on the degree of safety of the Ajaokuta/Itobe Bridge in Kogi state. The public outcry was as a result of a severe damaged expansion joints of the bridge. Visual inspection and concrete strength test were carried out to ascertain the safety condition of Itobe Bridge. Seven out of the total number of eight expansion joint covers were damaged and out of place while all the elastomeric bearings were in good working condition. The scouring of the river bed was not visually pronounced except little at the abutment side of the Abuja-Ayingba approach which is attributed to change of water course. Farming activities within the vicinity of the bridge embankment has no effects on the bridge foundation. The compressive strength test result of some bridge elements selected shows that the values are within the satisfactory range. The assessment recommended the lengthening and desilting of the drainage pipes to prevent further corrosion of the concrete and steel members. The use of sand blasting and repainting of the steel beams was also recommended to protect them from further corrosion. Maintenance of cracks on the reinforced concrete abutment and piers should be carried out. The use of sheet piles filled with compacted sand or gabions around the exposed piles caps to protect the foundation was recommended. Shoreline protection measures should be used in protecting the bridge eroded embankment. Seven out of eight expansion joint devices were damaged therefore exposing the elements of the structure that are otherwise protected by the joint devices. The openings about 47cm-53cm becomes a conduit by which moisture, abrasives, chemicals, and other debris are deposited on the superstructure and substructure below the opening, thereby causing extensive damage. The expansion joints devices should be fixed with proper elastomeric strip seal to protect the bridge from further deterioration.
Highlights
The United States National Bridge Inspection Standards (NBIS, 2012) in their (Bridge Inspectors Reference Manual) defines a bridge as a structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the centre of the roadway of more than 6.09 metres between undercopings of abutments or spring lines of arches, or extreme ends openings for multiple boxes; it may include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening
To prolong the life span of a bridge, there is the need to routinely inspect drainage systems, expansion joints, bearing assemblies, beams, seats, caps, embankments, piers and other critical members of the bridge (Iowa DOT, 2011) The Itobe Bridge is situated across River Niger in Kogi State Nigeria; the bridge has a great importance to the Nigerian economic, social and financial benefits as it links the northern and the eastern part of the country
Integrity Test Non-Destructive Test (NDT)structural integrity tests were conducted on some selected bridge components using Gilson Schmidt Concrete Test Hammer to determine the compressive strength of the concrete
Summary
The United States National Bridge Inspection Standards (NBIS, 2012) in their (Bridge Inspectors Reference Manual) defines a bridge as a structure including supports erected over a depression or an obstruction, such as water, highway, or railway, and having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the centre of the roadway of more than 6.09 metres between undercopings of abutments or spring lines of arches, or extreme ends openings for multiple boxes; it may include multiple pipes, where the clear distance between openings is less than half of the smaller contiguous opening. Failure of the bridge will be disastrous to the users as it will halt the commercial movement thereby affecting the country’s economy The aim of this assignment is to prepare an assessment report on Itobe Bridge in order to assess its current condition, overall safety, and performance of the bridge structure, identification of any major defect or incident and any steps that might be required to secure its future durability and to design predictive maintenance for the bridge. Itobe/Ajaokutabridge is a reinforced concrete (Haunched Box Girder) bridge built across River Niger by Julius Berger group of company in 1985.The study area is between latitude and longitudes7°25'53.56"N,6°42'9.33"E just 2 kilometers away from Ohunene community It has total length of 2,890metres, consisting of 8 expansion joints spanning at about 361meters apart and 66,740 square meters of surface area carrying dual carriageway of 18m total width per lane (including median and walkway) on A2 Highway of Nigeria. Drone-aided visual inspection and structural integrity assessment (compressive test) were carried out on the bridge with the view to gather any relevant information for further study and compilation
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