International Concrete Abstracts Portal

This paper presents a unique approach to examine the performance of constructed concrete bridges in cold regions, based on a combined statistical analysis and geographic information system (GIS) method. A total of 3,013 bridges and 1,126 bridge decks selected from the State of North Dakota (one of the coldest regions in the United States) are analyzed. Detailed technical information of the examined bridges is obtained from the National Bridge Inventory (NBI) database constructed between 2006 and 2007. A statistical analysis is conducted to identify the critical sources of bridge deterioration in cold regions, in particular concrete bridges, using the ordinary least-square multiple regression method. The performance of concrete bridges under cold weather is in general satisfactory, while the deck slabs are the critical structural members and may require regular maintenance and repair. The contribution of the year-built and the presence of water are the most critical factors to the bridge deterioration. A case study is presented based on a 29-span bridge consisting of cast-in-place deck slabs supported by prestressed concrete and steel plate girders. Detailed inspection results are reported and adequate maintenance methods are discussed.

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.

The Texas Department of Transportation (TxDOT) maintains over 33,000 on-system bridges. A considerable number of these bridges are damaged each year by extreme events or structural deterioration and must be repaired rapidly. Externally bonded carbon fiber reinforced polymer (CFRP) composites provide TxDOT with a viable technique for repairing many damaged concrete bridges. CFRP has been used extensively as structural reinforcement for its exceptional engineering properties, simplicity, flexibility, and rapid placement. TxDOT began using CFRP in 1999 and has repaired more than 30 impact-damaged concrete bridges, resulting in considerable time and money savings. This paper summarizes TxDOT’s experience repairing concrete bridges damaged by impact, fire, corrosion, and alkali-silica reaction (ASR), focusing on damage assessment, determination of reparability, and procedures essential for effectiveness. TxDOT engineers have made a conscious effort to utilize CFRP materials to repair impact-damaged beams. CFRP has been used to supplement prestressed strands to restore flexural capacity, laterally ‘harden’ bottom flanges against damage from re-impacts, and enhance the ductility, shear strength, and integrity of concrete bridge beams. For repeatedly impact damaged beams, CFRP has been used as ‘sacrificial’ reinforcement to protect the primary reinforcement, the prestressed strands, and to increase survivability, thus preserving the structure. Recommendations regarding the effectiveness of such CFRP repairs are presented.

Fiber reinforced polymer (FRP) reinforcements have emerged as alternative to traditional materials for reinforcing new structures and the rehabilitation of existing structures. This paper will present the first field application on the use of FRP reinforcement to rehabilitate a historic arch bridge located in Cambridge, Ontario Canada. The bridge, Main Street Bridge, is a two span concrete bowstring arch bridge built in 1931. As part of the rehabilitation, the existing deck and sidewalks were removed and replaced. Glass FRP (GFRP) reinforcement was used in the deck and sidewalks. The new deck was 200 mm thick and was reinforced with16mm diameter GFRP bars spaced at 300 mm o/c (top longitudinal) and 19mm diameter GFRP bars spaced at 150 mm o/c (bottom longitudinal). The transverse reinforcements were 16mm diameter GFRP bars at 300 mm o/c (top and bottom). The floor beams supporting the deck were deficient in shear and as such Carbon FRP (CFRP) U-wraps were installed transversely over the beam regions that were deficient in shear. The design for the GFRP reinforcement in the deck and the CFRP reinforcement for shear strengthening of the floor beams was according to the Canadian Highway Bridge Design Code (CSA S6-06). The rehabilitation work including condition assessment, FRP designs, and installation of the FRP systems are discussed.