A Sustainable built-environment requires a comprehensive process from material selection through to reliable management. Although traditional materials and methods still dominate the design and construction of our civil infrastructure, nonconventional reinforcing and strengthening methods for concrete bridges and structures can address the functional and economic challenges facing modern society. The use of advanced materials, such as fiber reinforced polymer (FRP) and ultra-high performance concrete (UHPC), alleviates the unfavorable aspects of every-day practices, offers many new opportunities, and promotes strategies that will be cost-effective, durable, and readily maintainable. Field demonstration is imperative to validate the innovative concepts and findings of laboratory research. Furthermore, documented case studies add value to the evaluation of emerging and maturing technologies, identify successful applications or aspects needing refinement, and ultimately inspire future endeavors. This Special Publication (SP) contains nine papers selected from three technical sessions held during the virtual ACI Fall Convention of October 2020. The first and second series of papers discuss retrofit and strengthening of super- and substructure members with a variety of techniques; and the remaining papers address new construction of bridges with internal FRP reinforcing and prestressing in beam, slabs, decks and retaining walls. All manuscripts were reviewed by at least two experts in accordance with the ACI publication policy. The Editors wish to thank all contributing authors and anonymous reviewers for their rigorous efforts. The Editors also gratefully acknowledge Ms. Barbara Coleman at ACI for her knowledgeable guidance.

The Sunshine Skyway Bridge is recognized as the State of Florida’s “flagship bridge.” The goal of the Florida Department of Transportation (FDOT) and specifically its entity that maintains the Skyway Bridge, the District 1 & 7 Structures Maintenance Office (DSMO), is to extend the life of this bridge to 100 years. Beam cracking on the trestle spans have been noted since the 1990s. In 2005 the DSMO initiated an in-depth study to determine the cause of cracking and to recommend a repair procedure. Upon completion, a committee of FDOT staff from various key offices in the State, along with consultant experts, determined criteria to address these cracks. The repairs included epoxy crack injection, penetrant sealer, and carbon fiber reinforced polymer (CFRP) wrap installation. FDOT addressed the repairs in three phases. The first repair project was in 2009, the second in 2013, and the third and final began in 2019.

The design principle of fiber-reinforced polymer (FRP) reinforcing composite bars for concrete structures has been well established through extensive research and field practices. Provisions governing certification testing and evaluation as well as quality control/assessment and FRP design provisions, are now in place to regulate materials specifications and design aspects and guide FRP manufacturers and end-users. The Canadian Standards Association (CSA) group addressing the state-of-the-art FRP material specifications and design requirement recently issued two updated provisions. The new edition of CSA S807 includes several additions and modifications in terms of quality and qualification requirements, material properties, testing procedures, and material mechanical and durability limitations. Additionally, the updated Section 16 of CSA S6 for the design of fiber-reinforced structures and highway bridges aimed at providing more rational design algorithms and allowing practitioners to take full advantage of the efficiency and economic appeal of FRP bars. This paper presents a summary of these recent modifications in Canadian codes and standards, introducing the underlying rationale. Additionally, the paper highlights the recent field applications of FRP bars in different types of concrete civil-engineering infrastructure.

This case study highlights the use of Fiber Reinforced Polymer (FRP) materials on the US 41 Highway Bridge over North Creek in Sarasota County near the Florida Gulf Coast. Design and construction involved the use of Glass-FRP (GFRP) reinforcement on the cast-in-place (CIP) concrete flat slab superstructure, Carbon-FRP (CFRP) prestressing strands on the concrete piles, and GFRP reinforced precast panels for the substructure combining a bridge bearing abutment and retaining wall system. The application of FRP prestressing and reinforcing is promoted by the Florida Department of Transportation (FDOT) under their Transportation Innovation Challenge initiative. Soldier-pile retaining walls are a commonly used system in southeastern US coastal states, but the incorporation of innovative materials such as CFRP-prestressing for piles and GFRP-reinforcing for concrete panels is not yet widespread. Comparison of lateral stability results of this wall system during construction and in the final condition is discussed. In addition, to describing the preferred FRP-PC/RC solution adopted for this project, a comparison is provided to a recently completed adjacent bridge that utilized a conventional carbon-steel PC soldier-pile and RC precast panel wall system. A further comparison is presented for the design and cost of the wall system based on the project design criteria (ACI 440.1R, ACI 440.4R, and 2009 AASHTO LRFD Bridge Design Guide Specifications for GFRPReinforced Concrete, 1st Edition) with the refinements and savings possible under the newer editions. Finally, the life-cycle cost, durability and environmental benefits from the use of the innovative CFRP and GFRP reinforcing systems in this type of traditional wall system, are identified for typical urban coastal areas with extremely aggressive conditions, congested access, and challenging environmental constraints.

Following an over-height truck impact, Carbon Fiber Reinforced Polymer (CFRP) fabric was used to retrofit the exterior girder in a four-span Reinforced Concrete Deck on Girder (RCDG) Bridge on route KY 562 that passes over Interstate 71 in Gallatin County, Kentucky. The impacted span (Span 3) traverses the two northbound lanes of Interstate 71. While the initial retrofit was completed in May 2015, a second impact in September 2018 damaged all four girders in Span 3. The previously retrofitted exterior girder (Girder 4) suffered the brunt of the impact, with all steel rebars in the bottom layer being severed. Damage to Girders 1, 2, and 3 was minor and none of the bars were damaged. A two-stage approach for the containment and repair of the damaged girders following an over-height truck impact was implemented when retrofitting the bridge. The repair and strengthening of all the girders using CFRP fabric was the economical option compared to the alternative option of replacing the RCDG bridge. The initial CFRP retrofit was found to have failed in local debonding around the impact location. The CFRP retrofit material that was not immediately near the impact location was found to be well bonded to the concrete. The removal of this material and subsequent surface preparation for the new retrofit was time consuming and challenging due to traffic constraints. In Girder 4 all but one of the main rebars were replaced by removing the damaged sections and installing straight rebars connected to the existing rebars with couplers. One of the rebars could not be replaced. A heavy CFRP unidirectional fabric, having a capacity of 534 kN (120,000 lbs.) per 305 mm (1 ft.) width of fabric, was selected for the flexural strengthening and deployed to replace the loss in load carrying capacity. A lighter unidirectional CFRP fabric was selected for anchoring and shear strengthening of all the girders, and to serve as containment of crushed concrete in the event of future over-height impacts. The retrofit with spliced steel rebars and CFRP fabric proved to be an economical alternative to bridge replacement.