International Concrete Abstracts Portal

Concrete bridges play an important role in the efficiency and reliability of transportation civil infrastructure. Significant advancements have been made over the last decades to enhance the performance and durability of bridge elements at affordable costs. From an application perspective, novel analysis techniques and construction methods are particularly notable, which have led to the realization of more sustainable built-environments. As far as the evaluation and rehabilitation of constructed bridges are concerned, new nondestructive testing approaches provide accurate diagnosis and advanced composites, such as carbon fiber reinforced polymer (CFRP), have become an alternative to conventional materials. This Special Publication (SP) contains nine papers selected from two technical sessions held at The ACI Concrete Convention and Exposition – Spring 2018, in Salt Lake City, UT. The objective of the SP is to present technical contributions aimed to understand the state of the art of concrete bridges, identify and discuss challenges, and suggest effective solutions for both practitioners and government engineers. All manuscripts were reviewed in accordance with the ACI publication policy. The Editors wish to thank all contributing authors and reviewers for their rigorous efforts. The Editors also gratefully acknowledge Ms. Barbara Coleman at ACI for her knowledgeable guidance in the development of the SP.

Bridge deck condition rating systems commonly use measurements of obvious defects recorded through visual investigation. Accordingly, the condition of bridge decks is rated linguistically with inherent vagueness in the description of the deck condition. Although several advanced non-destructive testing (NDT) technologies have emerged for inspecting bridge decks, their results have yet to be incorporated in the condition rating process. The present study establishes a unique link between NDT technologies and inspector findings by developing a novel bridge deck condition rating index (BDCI). The proposed procedure captures the integrated results of infrared thermography (IRT) and ground-penetrating radar (GPR), along with visual inspection judgement deployed to evaluate a full-scale aging concrete bridge deck. The information sought to identify the parameters affecting the integration process was gathered from bridge engineers with extensive experience and intuition. The analysis process utilized the fuzzy set theory, thus overcoming the inherent scientific uncertainties and imprecision in the measurements of bridge deck subsurface defects by IRT and GPR testing along with surface defects identified through bridge inspector observations. Integrating the proposed BDCI procedure with existing bridge management systems can provide a detailed and reliable appraisal of bridge health, thus helping transportation agencies in optimizing budgets and prioritizing maintenance, repair, and rehabilitation efforts.

This research focused on concrete beams with voids simulating beams with fully corroded steel that were repaired with CFRP laminates. The experimental program included testing five, approximately one-third-scaled simply supported rectangular concrete beams. In three beams, the oiled steel rebars for flexure and shear were safely pulled out of the formwork after the concrete had cured for six hours, leaving voids. This technique was used to represent an extreme case of corrosion, albeit non-realistic, that is even worse than being exposed to the most corrosive environment. The aim was to investigate the extent of improvement by CFRP to flexural and shear capacity of beams that contain fully corroded steel bars, simulated by voids. The first specimen was with voids representing completely deteriorated steel. The second was a plain concrete beam without voids. The third beam was a typical code-designed reinforced concrete (RC) beam, that represented the “original undeteriorated” beam. The two remaining deteriorated beams were repaired by externally bonding one and two layers of CFRP. Load carrying capacity, deflection, and ductility were measured and compared. The novel results of this investigation were that test results showed that one layer of CFRP increased the load capacity to slightly higher than the RC beam, and two layers of CFRP increased it by a factor of two. Finally, a computer model was created to estimate the performance of the tested beams and to carry out a parametric study to investigate the effects of CFRP longitudinal reinforcement ratio and CFRP transverse confinement ratio on the flexural performance of CFRP-repaired concrete beams. The predicted contribution of CFRP to flexure and shear capacities was in good agreement with test results.

Due to increased traffic loads and changes in the code provisions many highway bridges in Germany exhibit deficits in shear capacity according to current codes. The majority of these bridges’ structures comprises continuous concrete beams whose calculatory shear capacity is often exceeded by now. However, the actual shear capacity of prestressed concrete continuous beams is usually underestimated since the design procedures have been derived on the basis of single-span beam tests and neglect significant shear transfer mechanisms. In order to extend the service life of existing bridges, the reserves in the design procedures can be partially taken advantage of by the application of refined design approaches. For this reason, five shear tests on prestressed concrete continuous beams have been performed at the Institute of Structural Concrete of RWTH Aachen University in Germany. Within these tests, the influence of cross-section type (rectangular and I-shaped cross-section), load distribution (concentrated and distributed loads) and the shear reinforcement ratio are investigated. In this paper, the test results of three beams under concentrated loads will be presented.

Employment of corrosion-resistant reinforcement represents a widely-recognized effective strategy to ensure the long-term durability of reinforced concrete (RC) and prestressed concrete (PC) structures. Fiber-reinforced polymer (FRP) composites have proved to be a reliable non-metallic solution, able to ensure both the required mechanical performance and corrosion resistance. FRP-RC infrastructural applications are currently spreading; conversely, FRP-PC bridges are still considered state of the art prototypes. Many are the conceptual and practical challenges accompanying this innovative technology: brittleness of FRP reinforcement, the likelihood of tension-controlled failure, limitations on the initial pull force, limitations on the sustained load that the member can carry, and service requirements that may control the design. Reports published by ACI committee 440 do not yet address FRP-RC/PC provisions in a consistent way. Discrepancies exist on how ACI 440.1R and ACI 440.4R approach FRP-RC/PC design, having the latter not being updated since the first generation of FRP regulations. This paper deals with the philosophy behind the design of the precast Carbon FRP-PC/Basalt FRP-RC double-tee girders and the auxiliary Basalt FRP-RC/Glass FRP-RC members that constitute the structure of a recently built pedestrian bridge. This study is an attempt to address the challenges still preventing the wide acceptance of CFRP in prestress applications and to unify the design approach for FRP-RC/PC structures. This successful case-study validates the proposed rationale and supports a slight relaxation of the design limits in terms of the initial pull force.