An Original Probabilistic Framework for Evaluating Residual Fatigue Life of Reinforced Concrete Highway Bridges in Nigeria

Highway bridge fatigue deterioration under Nigerian traffic loading is driven by overloading prevalence, pavement roughness-induced dynamic amplification, and high truck traffic proportions that differ substantially from the bridge loading conditions assumed in international fatigue design codes. This study develops an original probabilistic framework for evaluating residual fatigue life of reinforced concrete highway bridges in Nigeria. The framework integrates three novel components: a Nigerian truck traffic load model developed from a 36-month weigh-in-motion data campaign on 18 bridges representing six traffic regions and road categories; a pavement-bridge interaction dynamic amplification model calibrated for Nigerian bridge roughness profiles; and a probabilistic fatigue reliability model using Monte Carlo simulation to propagate uncertainties in loading, material properties, and inspection measurement errors. Damage tolerance analysis using fracture mechanics principles is extended to reinforced concrete components using the Paris-Erdogan crack growth relationship calibrated to Nigerian structural concrete properties. The framework is applied to 30 bridge case studies of varying age, traffic exposure, and condition, validated against available inspection records. Results indicate that Nigerian truck overloading contributes up to 65 percent of cumulative fatigue damage beyond design assumptions. Residual fatigue life estimates differ from deterministic calculations by 20 to 45 percent when uncertainty is fully propagated. The probabilistic framework constitutes an original contribution to bridge lifecycle management methodology for high-overload-risk environments.

Keywords: bridge fatigue life, probabilistic framework, weigh-in-motion, reinforced concrete bridges, Nigeria