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.

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.

In response to Federal Highway Administration requirements, several states are in the process of ensuring all bridges within their inventories are load rated. A challenging aspect of this effort is load rating reinforced concrete bridges that have no structural plans when there are thousands of such structures within a state inventory. To inform these efforts, the literature was reviewed to identify existing methodologies and a survey was distributed to engineers at state departments of transportation throughout the United States to understand how practicing engineers approach this problem. The survey responses show there are numerous bridges in the U.S. without plans; over 25000 bridges without plans are located in the 18 states that provided responses. Concrete structures comprise 70% of such bridges. To load rate concrete bridges without plans, most responding states report primarily using engineering judgement, which may include reference to performance under existing traffic, era-specific design traffic loads, assumed material properties and reinforcement quantities, or data collected using load tests or non-destructive evaluation. Several methodologies are described and advantages/limitations of each are discussed.

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.

In 2006 in Quebec, a skewed cantilever solid concrete slab bridge without shear reinforcement collapsed due to a shear failure, which highlighted the need to improve the assessment of this type of structure. A large experimental program was carried out to test three decommissioned solid slab bridges to failure. In parallel, an extensive nonlinear finite element analysis study was performed with the aim of better understanding the failure mechanisms, the degree of load redistribution, and to gain insight into the ultimate shear capacity of these structures. A beam shear failure mode was expected for the first two bridge tests, but a flexural failure mode was observed. This paper focusses mainly on the last field test of a simply supported solid slab bridge having a 40 degree skew. The load position and the loading protocol were established with the objective of causing a shear failure at the obtuse corner of the slab where high shear forces develop. The main test motivation was to illustrate that simply supported solid slab bridges would normally not be prone to shear failure due to an intrinsic redundancy. The paper presents experimental techniques that could help bridge owners in assessing the performance of their bridges. The test results also provide valuable information for calibrating nonlinear element models that can be used for assessing the carrying capacity of existing concrete bridges. Although the actual bridge conditions were worse than anticipated, a global shear failure mode occurred near the obtuse corner at a maximum load of 1400 kN, which significantly exceeded the factored shear force due to the maximum traffic load. The failure was followed by a gradual load redistribution toward undamaged portions of the slab. This field test confirmed the assumption of non-fragility for this type of bridge, where support conditions enable development of an intrinsic redundancy. Despite these observations, nonlinear analyses carried out in parallel to the testing program indicated that this beneficial effect diminishes with an increase of slab thickness.