International Concrete Abstracts Portal

Sponsors: Sponsored by ACI Committees 342, Evaluation of Concrete and 343, Concrete Bridge Design (Joint ACI-ASCE) Editors: Benjamin Z. Dymond and Bruno Massicotte In recent years, both researchers and practicing engineers worldwide have been refining state-of-the-art and emerging technologies for the strength evaluation and design of concrete bridges using advanced computational analysis and load testing methods. Papers discussing the implementation of the following topics were considered for inclusion in this Special Publication: advanced nonlinear modeling and nonlinear finite element analysis (NLFEA), structural versus element rating, determination of structure specific reliability indices, load testing beyond the service level, load testing to failure, and use of continuous monitoring for detecting anomalies. To exchange international experiences among a global group of researchers, ACI Committees 342 and 343 organized two sessions entitled “Advanced Analysis and Testing Methods for Concrete Bridge Evaluation and Design” at the Spring 2019 ACI Convention in Québec City, Québec, Canada. This Special Publication contains the technical papers from experts who presented their work at these sessions. The first session was focused on field and laboratory testing and the second session was focused on analytical work and nonlinear finite element modeling. The technical papers in this Special Publication are organized in the order in which they were presented at the ACI Convention. Overall, in this Special Publication, authors from different backgrounds and geographical locations share their experiences and perspectives on the strength evaluation and design of concrete bridges using advanced computational analysis and load testing methods. Contributions were made from different regions of the world, including Canada, Italy, and the United States, and the technical papers were authored by experts at universities, government agencies, and private companies. The technical papers considered both advanced computational analysis and load testing methods for the strength evaluation and design of concrete bridges.

This paper presents the methods used by Jacques Cartier and Champlain Bridges Incorporated (JCCBI) to monitor the Champlain Bridge in its maintenance and structural monitoring program. The monitoring program, which was established in 2012 and increased in scope over time to obtain a clearer picture of the state and behavior of the Champlain Bridge, allows continual monitoring of the structural behavior of the bridge by monitoring critical members flexural response. Established key performance indicators detectable by the equipment are used to alert JCCBI to react quickly to ensure the structural integrity of the bridge. This paper describes the instrumentation and monitoring of the edge girders of 50 concrete spans and 45 pier caps of the Champlain Bridge, using optical sensors for recording strains on these elements. Over 330 optical sensors were installed on the bridge to record data continuously at 50 Hz. Such data contains invaluable information for monitoring the bridge response and can provide early warnings to indicate structural degradation. Through these means, amongst others, JCCBI preventively manage the risks associated with this vital infrastructure reaching the end of its service life.

Due to the increase in traffic and transported freight in the past decades, a significant number of in-service bridges have been subjected to loads above their original design capacities. Bridge structures typically incorporate deep concrete elements, such as cap beams or bent caps, with higher shear strengths than slender elements. However, many in-service bridges did not account for the deep beam effects in their original design due to the lack of suitable analysis methods at that time. Nonlinear finite element analysis (NLFEA) can provide a better assessment of the load capacity of deep bridge bent beams while accounting for the deep beam action. However, there is little guidance on how to conduct a numerical strength evaluation using the NLFEA. This study presents a nonlinear modeling methodology for the strength evaluation of deep bridge bents while considering advanced concrete behavior such as tension stiffening, compression softening, and dowel action. Five existing bridge bent beams are examined using the proposed methodology. The effectiveness and advantages of the proposed methodology are discussed by comparing the numerical results, including the load-displacement responses, load capacities, cracking patterns and failure modes, with the strut-and-tie and sectional analysis methods. Important modeling considerations are also discussed to assist practitioners in accurately evaluating deep bridge bents.

Several of the first prestressed concrete segmental bridges in North America were built in Quebec, Canada. The Rivière-aux-Mulets bridge was one of them. Built in the early 1960s, this bridge experienced several disorders due to inadequate design criteria enforced at that time. Despite a structural strengthening in the late 1980s, a bridge behavior follow-up has been required to ensure reliability. The structural health monitoring program implemented to track structural disorders, along with results from modal analysis and diagnostic load tests, is presented with a focus on the instrumentation and the data analysis. A three-dimensional finite element model was developed and calibrated using the frequencies and mode shapes detected under ambient traffic conditions. Data analyses showed that the expansion bearings were frozen, causing bending of the associated piers, which generated axial forces in the deck and decompression of concrete in the area surrounding active cracks. This process enables premature failure of prestressing tendons in the vicinity of these cracks, especially those located in the top flange, which is a corrosion-friendly environment. Development of cracks and associated prestress loss caused a reduction in the bridge load-carrying capacity. Analyses of health monitoring data led to acute assessment of the overall bridge structural performance.

An experimental investigation was conducted on a full-scale prestressed concrete girder laboratory bridge to determine whether linear elastic shear distribution principles are conservative for load rating at ultimate capacity. A secondary goal was to determine whether existing web-shear cracks would be visible in an unloaded state. Two tests were conducted to failure (one near the end with a partial-depth diaphragm and one near the end without) to determine if the most loaded interior girder shed shear force to adjacent girders as it transitioned from uncracked to cracked to failure. Failure during each test was characterized by web-shear crushing and bridge deck punching at the peak applied load. Differences in the behavior of the two ends (with and without partial depth end diaphragm) affected the diagonal crack pattern, shear distribution, and loads at cracking and failure. The effect on loading was less than 10%. Inelastic shear distribution results indicated the girder carrying the most load redistributed shear to the other girders as it lost stiffness due to cracking. Use of linear elastic load distribution factors was conservative considering shear distribution at ultimate capacity. The visibility of web-shear cracks in an unloaded state was found to be a function of stirrup spacing.