Professional Assessment of Defects in Prestressed Concrete Bridges on Federal Roads in South West Nigeria

Prestressed concrete bridges are critical infrastructure components on the federal road network in South West Nigeria, and professional assessment of their defects provides essential intelligence for the Federal Ministry of Works' bridge maintenance programme. This study assessed the structural defects of 18 prestressed concrete bridges on federal roads in Ogun, Oyo, and Ekiti States through visual inspection and limited non-destructive testing. Inspection was conducted using the Federal Roads Maintenance Agency bridge inspection protocol, supplemented by BS 6349 bridge condition assessment guidance. Defects recorded included concrete spalling, reinforcement corrosion, prestress tendon duct cracking, bearing deterioration, expansion joint failure, and scour damage. A Bridge Condition Index was calculated for each bridge based on element severity and extent ratings. Results showed that 7 of 18 bridges received Bridge Condition Index scores below 60 (poor condition), requiring priority remediation. Concrete spalling exposing corroded reinforcement was the most prevalent structural defect, present on 14 bridges. Expansion joint failure was observed on 12 bridges, allowing water ingress to substructures. Prestress tendon duct cracking was confirmed on 4 bridges through ultrasonic pulse velocity testing. Bridge scour protection was absent or inadequate on 8 bridges spanning watercourses. The study concludes that the federal bridge stock in South West Nigeria requires significantly increased inspection frequency and proactive maintenance investment, and recommends a 5-year bridge rehabilitation programme under the Federal Roads Maintenance Agency.

Keywords: prestressed concrete bridges, bridge defects, Bridge Condition Index, South West Nigeria, bridge maintenance