Destructive and Non-Destructive Testing of Bridge J857 Phelps County, Missouri : Strengthening and Testing to Failure of Bridge Piers

Many of the existing reinforced concrete (RC) bridge piers constructed in the first half of this century were designed as gravity piers with minimal flexural reinforcement and no consideration to seismically induced lateral forces. When considered in earlier designs, the seismic lateral forces were typically low. The potential risk of failure of columns on these piers under a moderate earthquake is becoming a growing concern for the transportation management agencies. In addition, flexural strength deficiency in RC columns may arise from the loss of reinforcement due to corrosion, premature termination of the main reinforcement, or inadequate splicing. One method for retrofitting columns with flexural strength deficiencies consists of the addition of a RC or steel jackets. However, these systems may not be very practical due to undesirable section enlargement or construction constraints. Fiber Reinforced Polymers (FRP) have suitable mechanical properties for structural applications such as corrosion resistance and high strength-to-weight ratio. Although a properly designed FRP jacket can improve column compression strength, shear strength, and ductility, it may not sufficiently improve flexural capacity. Near-surface mounted (NSM) FRP rods is another technique that could be used to improve the flexural capacity of RC columns. This strengthening technique consists of FRP rods embedded in grooves made on the surface of the concrete and bonded in place with epoxy. To investigate the applicability and effectiveness of this technique, a research program was carried out in which bridge columns originally designed to carry gravity loads were upgraded and then tested to failure. Flexural strengthening was achieved by mounting carbon FRP (CFRP) rods on two opposite sides of the columns. In addition, the strengthened columns were wrapped with carbon and glass composites to satisfy seismic detailing requirements. The columns were tested to failure by applying lateral load cycles. The behavior of strengthened columns and their failure modes are discussed and conclusions are drawn. Test results indicate that the proposed strengthening is feasible and effective for improving the flexural capacity of RC columns. The capacity of the strengthened sections could be predicted using classical methods of analysis. Full investigation of the upgraded structure should be made to ensure that the deficiency is not shifted to other structural components. The final report consists of three volumes. Volume I depicts the strengthening and testing to failure of the three bridge decks. Volume II focuses on the laboratory and field dynamic tests. Volume III presents the strengthening and testing to failure of the bridge piers