Non-destructive evaluation techniques were used to assess the condition of a 40-year old concrete bridge operating in an aggressive marine environment. The bridge’s superstructure includes both reinforced and prestressed concrete one-way slabs, and experienced widening, repairs, and recently strengthening by means of externally bonded carbon fiber reinforced polymer (CFRP) laminates. Phase I of the investigation focused on evaluating deterioration of concrete and steel reinforcement by means of in-situ and laboratory testing. A 24 in. by 24 in. [610 by 610 mm] grid was marked on the bottom surface of the supporting slabs to map indicators of physical damage. Measurement of carbonation, pH, chloride content, corrosion potential, and visual inspection were implemented and rendered as layered maps to identify damaged areas. Phase II includes acoustic emission (AE) monitoring under service loads. AE amplitude, duration, energy and hits were analyzed to identify structural activity associated with damage phenomena, such as concrete cracking, slip between corroded reinforcement and surrounding concrete, and debonding of CFRP laminates. The database acquired from Phase I and Phase II was used for damage assessment. Combined results from the different techniques show promise in determining areas of concern with reduced uncertainty than when using a single measurement technique.

The paper deals with a rehabilitation case study on a pre-stressed concrete (PC) bridge (named “Torrente Casale”), located in the south of Italy (on the Salerno-Reggio Calabria highway). The bridge, built in the ’70s, was enlarged in 2001 in order to satisfy the new traffic demand. A seismic assessment of the bridge resulted necessary in order to verify its capacity to sustain both gravity and seismic loads. Both destructive and non-destructive tests have been performed in order to evaluate concrete and steel reinforcement mechanical properties. A theoretical analysis was performed, showing that the bridge piers existing cross section and internal reinforcement were not adequate to satisfy the seismic actions. Thus, two rehabilitation systems were investigated: a) an innovative technique based on the combined use of Fibre Reinforced Polymer laminates (FRP) and Steel Reinforced Polymer spikes (SRP), b) a traditional rehabilitation technique (i.e. RC jacketing). The design assumptions and calculations for the rehabilitation as well as the comparison between the effectiveness of the two investigated strategies are presented and discussed in the paper. The main construction phases of the strengthening technique, executed by following the first outlined strategy are also presented and illustrated.

Highway bridges are periodically exposed to fires that can cause severe and extensive damage to critical components. After such an occurrence, bridge owners are immediately faced with several critical questions, including: • Is the structure safe for use by the public? • Does the damaged bridge require load posting? • How has the service-life been affected? • What repair or rehabilitation alternatives are available? To properly answer owner concerns regarding the safety and serviceability of critical infrastructure, a complete evaluation consisting of visual inspection, Non-Destructive Testing (NDT), and laboratory testing is required. The objective of the evaluation is to identify the depth and extent of fire damage as well as any change in the physical or material properties in the steel and concrete. This paper entails a discussion of fire related damage mechanisms to highway structures, NDT methods and technologies available for evaluation of fire-damaged bridge elements and repair alternatives to return bridges to safe operation and restore the intended service life. Three case studies will be discussed to demonstrate application of the inspection and evaluation process presented.

This paper presents on-site inspection techniques to examine a damaged prestressed concrete girder bridge. The bridge is 18.3 m [60 ft.] and consists of double-tee beams (DT3000 x 700 ) with a 50 mm [2 in.] topping concrete. To simulate the effect of deterioration for the girder, the leg member is intentionally damaged by cutting 2 prestressing strands. A load test is conducted to evaluate the flexural behavior of the bridge before and after the damage. A site inspection is conducted after 10 months of the load test. The inspection techniques used for this study includes the visual inspection, pull-off test, ultrasonic test, rebound hammer test, core test, and surveying. The bridge exhibits significant cracks and spalling of the concrete in the deck and the legs. Corrosion of the reinforcing steels is observed. The pull-off test shows that the bond strength between the flange of the girder and the topping concrete is adequate. The ultrasonic test exhibits some internal defects of the leg member, including an increased transmission time of the ultrasound. The in-situ concrete strength measured is reasonably close to the specified 28 day concrete strength, based on the rebound hammer test and the core test, with an average error of 2.1%. Permanent downward deflections are not observed, whereas a maximum camber of approximately 35 mm [1.4 in.] is measured by surveying. The inspection techniques reported in this study are reliable and recommended to examine concrete bridge elements.

The historic bridge on Henley Street over the Tennessee River in Knoxville, Tennessee is a six-span, 1,389-foot (423 m) long open spandrel reinforced concrete arch bridge flanked by a 165-foot (50 m) long, three-span approach girder structure at each end. The arch span lengths range from 185 feet (56 m) to 317 feet (97 m) with an average rise-to-span ratio of 0.30. In an effort to accommodate six travel lanes, reduce the number of expansion joints in the deck, and use the existing arch structure in its present condition, a 1,720-foot (524 m) long continuous superstructure unit was designed with expansion joints located only at the abutments; however, analytical studies on the bridge showed that the combined effects of superstructure continuity and increased live load demands led to increased forces at various sections of respective structural components of the bridge. A combination of innovative design techniques were used to mitigate these adverse load effects. The bridge improvements were designed in accordance with the National Historic Preservation Act and the Department of Transportation Act of 1966.