STRUCTURAL INTEGRITY ASSESSMENT OF THE BENIN SAGAMU OVERPASS BRIDGE BY THE RELIABILITY THEORY

ABSTRACT

The increase in traffic intensity and overloading of vehicles could cause a bridge to experience more traffic loading than those it was designed for and cause its structural members to be overstressed than intended by designers. One way to verify these abnormalities is by structural integrity assessment. The Benin Sagamu Overpass Bridge located at Oluku, Benin City, Edo State, has been in service for over two decades and with no major rehabilitation and maintenance works done on it, this research developed methods to verify its structural integrity. The structural integrity of the longitudinal and transverse girders, was determined by structural assessment techniques based on CS 451. The structural integrity was quantified in terms of Reliability Index and probability of failure. The dimensions of the bridge were measured and also, the specific weights of bridge materials were adopted from CS 451 to estimate the bridge dead load. Traffic count was performed to estimate the bridge live load modified with traffic composition factors, hence, making the estimated live load bridge site-specific. The assessment vehicle axle loads were adopted for structural analysis using the influence line theory. Moments from the analysis resulting from dead and live loads represented the bridge strength model. The resistance model of the bridge was derived from concrete strength by Non-Destructive testing and from the section properties. The reliability theory was applied to determine the reliability and probability of failure of the transverse and longitudinal girders of the bridge. The bridge structural assessment showed that the bridge had shown no major signs of deterioration except for the expansion joints which needs immediate attention. Statistical analysis on the traffic data produced and assessment live load of 29.2T. The reliability index of the transverse girder and longitudinal girders were 3.9 and 5.2 respectively and compares favourably to target reliabilities of EN 1990. The reliability theory was found to be efficient in determining the structural integrity of the bridge by the use of manual traffic counts