Residual strength of CFRP strengthened prestressed concrete bridge girders after hydrocarbon fire exposure

Significant investigations have been conducted on the effect of extreme load events, such as earthquake, wind and flood on bridges, as compared to fire hazards, even though fire can cause significant economic and public impacts. To bridge this knowledge gap, a full-scale single span prestressed concrete bridge was tested under a combined hydrocarbon fire and simulated AASHTO live load. The superstructure comprised of three standard I-girders, precast deck panels, cast-in-place deck, and elastomeric bearing pads. One girder was wrapped with carbon fiber reinforced polymer (CFRP), another with CFRP and sprayed fireproofing and a third was without CFRP or fireproofing. The test was conducted for 60 min and the fire temperature reached as high as 1131 degrees C. It was found that the fireproofing was helpful in lowering the temperature at the CFRP-concrete interface, thereby preserving the integrity of the CFRP bonding, the concrete substrate, and prestressing steel. Without fireproofing, the CFRP quickly debonded, thereby causing significant concrete spalling and loss of some prestressing strands. Following the fire test, the deck was saw cut and each girder was tested in the laboratory under a three-point bending set-up to determine their residual strengths. The CFRP girder without fireproofing lost 59% of its design flexural capacity, while the one with fireproofing did not experience any reduction.