International Concrete Abstracts Portal

This paper presents the performance reliability of reinforced concrete beams strengthened with fiber reinforced polymer (FRP) sheets, including structural fragility. Emphasis is placed on the development of effective strains that can represent FRP-debonding failure. The reliability predicted by a conventional standard log-normal cumulative probability density function and by the proposed response surface metamodel (RSM) combined with Monte-Carlo simulation (MCS) is employed to assess the contribution of physical attributes to debonding failure. The models are constructed based on a large set of experimental database consisting of 230 test beams collected from published literature. Another aspect of the study encompasses the effect of various RSM parameters on the variation of effective strains, such as FRP thickness (t_f), steel reinforcement ratio (ρ), concrete strength (f^’_c), beam height (h), beam width (w), span length (L), and shear span (a). The mutual interaction between these parameters indicates that those related to beam geometry (i.e., L, w, h, and a parameters) and the t_f parameter are significant factors influencing the effective strain of FRP-strengthened beams.

Editors: Yail J. Kim, Baolin Wan, Isamu Yoshitake

Since the major milestones of sustainability, such as the Hannover Principle in 1991 and the Kyoto Protocol in 1997, the concept of sustainability has been broadly adopted by various disciplines. New construction consumes considerable amounts of energy and materials, and CO2 emission in 2020 is expected to increase by 100%, compared with that of today. Technical communities are responsible for improving the sustainability of the built-environment by using more durable and highly efficient materials to reduce the need for replacement, maintenance, or repair. When subjected to aggressive environments, the performance of constructed concrete bridges and their elements is of interest from socioeconomic perspectives. Advances in a variety of aspects are required to achieve such a goal, including the durability of concrete members, performance monitoring technologies, evaluation methodologies, damage assessment, and structural rehabilitation. This Special Publication (SP) includes 10 papers selected from the three special sessions held at the ACI Fall convention in Washington, DC, October 2014. Each submitted manuscript has been rigorously reviewed and evaluated by at least two experts. The editors wish to thank all contributing authors and anonymous reviewers for their endeavors.

Note: The individual papers are also available. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP-304

The Alaskan Way Viaduct replacement project is a joint program between the Washington State Department of Transportation (WSDOT), the Federal Highway Administration (FHWA), the City of Seattle, King County and the Port of Seattle. The project consists of several sub-tasks including the total replacement of the State Route 99 double-deck viaduct. The Alaskan Way Viaduct is a vital factor for economic sustainability while serving as a major transportation artery for the greater Seattle metropolitan area. Span 2C of this project is 210-ft (64.01 m) long and consists of an 8-inch (203 mm) thick cast-in-place concrete slab supported on seventeen WF100G precast pretensioned concrete girders. Construction is split into two phases: Phase I includes eight girders spaced at 6 ft-5 inches (1.96 m) on center and Phase II includes nine girders spaced at 6 ft (1.83 m) on center. This span has an eleven-degree skew and includes four cast-in-place concrete diaphragms at quarter points in addition to the end diaphragms. The WF100G girders are each 205-ft (62.48 m) long and 100-inch (2540 mm) deep. Each girder is reinforced with eighty (80) 0.6-in. (15.24 mm) diameter, 270 ksi (1860 MPa), low-relaxation seven-wire strands. WSDOT in collaboration with Concrete Technology Corporation (CTC) and the George Washington University (GW) have instrumented four girders of the second phase with about forty (40) vibrating wire gauges. This paper presents the details of the on-going plan developed by the WSDOT/CTC/GW team to monitor the progress of prestress losses over a period of three years. The paper will also present the challenges that the team faced during the instrumentation stage.

Composite concrete bridges are widely used because they combine the advantages of precast concrete with those of cast-in-place concrete. However, because of the difference in shrinkage properties between the girder and the deck and because of the sequence of construction, the deck is subject to differential shrinkage tensile stresses. These tensile stresses may lead to excessive cracking. This paper demonstrates how the likelihood of deck cracking due to differential shrinkage can be reduced and how consequently the resistance of composite concrete bridges against time dependent effects can be enhanced by choosing a deck mix with low shrinkage and high creep. An experimental study on the long term properties of seven deck mixes is presented to identify a deck mix with the aforementioned properties. A comparison of three composite concrete bridge systems used for short-to-medium-span bridges is performed to identify the bridge system that is most resistant against time dependent effects. The mix with saturated lightweight fine aggregates appears to best alleviate tensile stresses due to differential shrinkage and the bridge system with precast inverted T-beams and tapered webs appears to be the most resistant.

This paper presents a detailed investigation into the load-deformation response of reinforced concrete beams strengthened with mechanically fastened fiber-reinforced polymers (MF-FRP). A bearing-slip model was developed for MF-FRP connections fastened with concrete expansion anchors. The model was used to predict the interfacial change in strain between the concrete and the FRP. When combined with load deformation constitutive equations, the bearing-slip model better predicted the load-deformation behavior in MF-FRP strengthened concrete beams. Comparisons to experimental data showed that the developed method reasonably predicts (typically within 8%) actual beam response at ultimate load. Moment-curvature diagrams were also developed and used to predict midspan deflection, typically within 30% of experimental results.