Supervision of Emergency Repairs of Existing Niger Bridge at Onitsha/Asaba in Anambra/Delta States - Nigeria

The bridge built by Dumez Construction (France) in 1963/1965, is composed of 4 continuous steel truss girders: lateral girders consist of 2 spans, each of which is 90m long; central girders consist of 4 spans, each of which is 130m long.

The elevation scheme is symmetrical. On each half of the bridge, fixed supports are located between the first and the second span and between the fourth and the fifth span, while expansion joints are located between the first and the second girder and in the middle of the bridge. The superstructure of the deck is made of a reinforced concrete slab. The reinforced concrete slab is above the steel deck and there is no interaction between them.

The 13 piers in reinforced concrete consist of 2 columns with a variable rectangular section. Columns are connected by a pier cap and a lower diaphragm.

The scope of the services is the resident supervision of the rehabilitation works on the bridge and includes:

• to check the quality of materials being used for all works;
• to check that all quality control tests are conducted for the works;
• to ensure that all the specification are adhered to all the materials used for the works;
• to ensure that the works are done according to the approved design and drawings;
• to advice the Engineer’s Representative on the technical aspects of the work;
• submission of monthly progress Reports indicating the quality of workmanship, test results and progress of work;
• to advise the Ministry on the shortcomings noticed during the execution of the works and forward professional advice;
• to jointly measure all executed work and countersign the interim statement with the Engineer’s Representative and the Contractor.