Govt plans fresh test on Third Mainland Bridge

FOLLOWING fresh fears of shifting and vibrations on the Third Mainland Bridge, Lagos, the Federal Ministry of Works has announced plans to engage a consultant to urgently assess the entire bridge substructure to determine the nature of maintenance work required.

The consultant’s scope of works will include echo metric test to check the structural integrity of the piles in water and selected piles on land (total of 988 piles), including coring on selected piles, testing and chemical analysis and underwater inspection of 658 piles. Report of the inspection of foundation piles is expected to include appropriate recommendations.

A statement by the ministry refutes claim by Senator Gbenga Ashafa in a motion at the National Assembly that the bridge is not safe for motorists. He claimed that the repair works carried out on the bridge in the last quarter of last year was “a mere window dressing on the expansion joints.”

Besides, Senator Gbenga Ashafa representing Lagos East Senatorial district, which has some part of the 11.8 km bridge, fears an imminent collapse citing findings of an investigation conducted by Head of the Concrete Structural Engineering Laboratory, Yousei University, Seoul Korea, Prof. J.H.T. Kim.

Ashafa told reporters in Lagos Monday that Kim came on research in December 2012 and conducted an underwater examination of the structures holding the bridge and reported that damage to the structure was worst than what he had been briefed.

He said the professors’ report, presented on the floor of the Senate last Thursday, indicated progressive steel caisson deterioration in about 1, 318 foundation piles and extensive reinforcement bar deterioration in eight piles.

The Director of Highways Design (Bridges), Federal Ministry of Works, Aniete Effiong, however, said “the ministry has taken proactive steps in line with its mandate to ensure that the Third Mainland Bridge, a very important infrastructure investment of government, is protected and kept in an acceptable service state.”

According to him, a report was submitted in November 2012 and the major findings were that the visual underwater inspection, the non-destructive tests and coring campaign carried out on the Third Mainland Bridge in Lagos confirmed the adequacy of pile concrete quality. Some degradation was observed particularly in the first few meters of pile shaft, with a consequence of 35 years of bridge life.

“Although serious steel casing corrosion was noticeable, it was pointed out that the steel casing has no structural function regarding pile bearing capacity, as they simply serve as formworks to the piles; no cases of total loss of piles, clearance between the pile and pile cap or other major anomalies were reported on the tested piles; and based on the results of the investigations, there is no evidence of immediate threat of failure of the pilings.”



















Effiong noted that the addendum to the final report submitted by the Nigerian Submarine Divers Limited in December 2012 confirmed some deterioration and defects at the underwater sections of some of the foundation piles as follows: concrete degradation and appreciable loss of concrete infill materials; extensive deterioration of embedded steel reinforcement in piles; and progressive deterioration of steel caisson of foundation piles.

He said: “The findings of Messrs Nigerian Submarine Divers Limited (NSD) were strictly based on visual inspection and under water photos. For this reason, and following meetings between officials of the ministry, Messrs NSD, Julius Berger and Borini Prono, it was decided that Advanced Integrity Assessment including high technology chemical analysis of concrete samples from piles was inevitable in order to authenticate the findings of NSD as contained in their reports. Moreover, since Messrs NSD Ltd is not a civil engineering consultancy firm, their capacity and professional competence to carry out such works was doubtful.”

He said, “in recognition of the fact that the required integrity test has not been exhaustively conducted on the entire bridge, even as various investigations had been concluded, the Ministry felt obliged to request Messrs Borini Prono and Company (Nigeria) Limited, a member of the PGH Consortium that constructed the first section of the bridge to assess the condition of some foundation piles of the first section of the Third Mainland Bridge which was mostly impacted in the reports by studying the original designs, conducting site investigation in collaboration with Messrs Trevi Foundations Nigeria Limited, the foundation specialist that undertook the piling works in the first place. Messrs ICECON Nigeria Limited, specialist in Bridge Investigations, was also engaged by Messrs Borini Prono to independently confirm the results of their investigation.”

In their conclusion, he said, the firms recommended that elaborate maintenance programme based on systemic assessment of all the piles should be put in place.