Experimental evaluation of red lead surface slip coefficient in 90-year-old riveted bridge

Aging riveted steel bridges face challenges like corrosion and loosening, necessitating effective rehabilitation. This study investigates the load transfer mechanisms and structural behavior of bolted–riveted combination joints, focusing on a 90-year-old steel bridge in Osaka, Japan, with original red lead primer on faying surfaces. Comprehensive analyses, including surface/chemical examinations, slip tests (average coefficient 0.274 for aged red lead with total 48 sample size), material characterization, and tensile tests on various joint configurations, were conducted. A key finding was the red lead primer’s remarkable 90-year integrity, effectively preventing underlying steel corrosion despite surface non-uniformity. Historic steel showed properties comparable to modern SS400 grade, with some lamination defects. Tensile tests showed that replacing rivets with high-strength bolts (HSBs) substantially improved joint stiffness and slip resistance, despite the low slip coefficient (0.274). Strategic partial HSB replacement, especially at joint ends, enhanced load transfer via friction, increased net section yield strength by approximately 10%, and reduced stress concentrations around bolt holes. Results validate partial HSB replacement as an effective retrofitting technique for aging riveted bridges with red lead-coated faying surfaces. The study offers critical insights into red lead’s long-term protective performance and provides valuable, data-driven guidance for the structural assessment, preservation, and life-extension of these vital historical infrastructure assets. • Small-scale slip tests reliably predict full-scale behavior of aged red lead joints. • 90-year red lead primer remains intact with slip coefficient of 0.274 ± 0.0525. • Strategic HSB replacement increases net section yield strength by 10%. • Surface heterogeneity causes slip variation (0.22–0.28) within normal deviation. • Red lead joints maintain structural integrity despite nine decades of service.