Strengthening of Bridge G-270 with Externally Bonded Carbon Fiber Reinforced Polymer (cfrp) Prepared for the Missouri Department of Transportation in Cooperation with the U.s. Department of Transportation Federal Highway Administration

The opinions, findings and conclusions expressed in this report are those of the principal investigator and the Missouri Department of Transportation. They are not necessarily those of the U. EXECUTIVE SUMMARY This report presents the results of a pilot study to apply externally bonded Carbon Fiber Reinforced Polymer (CFRP) sheets to strengthen a simple span reinforced concrete solid slab bridge built in 1922. Strengthening with CFRP sheets was accomplished in three days without traffic interruption, and preparation consisted of only light sandblasting. Bridge G-270 is the only load-posted structure on a heavy truck route that serves a lead mining operation and the objective was to strengthen the bridge to allow removal of the load posting. The University of Missouri-Rolla conducted the pilot study for the Missouri Department of Transportation (MoDOT) under MoDOT Contract No. RI98-012. The laboratory testing included the static flexural test of two full-scale beams, designed as a unit strip from the existing bridge deck, and the fatigue bond test of coupon-type specimens. Two reinforced concrete beams, a control beam and a beam strengthened with externally bonded CFRP were tested under four point bending. Coupon-type specimens consisting of unreinforced concrete beams with a reversed T-shaped cross-section and with a CFRP sheet applied to the bottom were tested. The purpose was to investigate the behavior of bond between CFRP sheets and concrete under fatigue loading. The field load testing of the bridge, before and after strengthening, was performed by the University of Missouri-Columbia to verify the performance of the bridge after the application of externally bonded CFRP. Long-term field measurements also were conducted to monitor the durability and the strain condition of the strengthened system. Pennsylvania State University conducted the monitoring of durability b y studying the electrochemical effects of the CFRP material on the degradation of the reinforcing steel. Fiber-optic strain sensors were applied to the FRP reinforcement and the concrete to allow for long-term monitoring of the integrity of the FRP reinforcement. This pilot study was a success. Laboratory and field tests confirmed that CFRP sheets, externally applied to a bridge superstructure, effectively strengthened the slab. Monitoring of the bridge will continue.