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  • The International Concrete Abstracts Portal is an ACI led collaboration with leading technical organizations from within the international concrete industry and offers the most comprehensive collection of published concrete abstracts.

International Concrete Abstracts Portal

Showing 1-5 of 11 Abstracts search results

Document: 

SP304-10

Date: 

October 27, 2015

Author(s):

Hamid Y. Omran and Raafat El-Hacha

Publication:

Symposium Papers

Volume:

304

Abstract:

A nonlinear 3D Finite Element (FE) analysis was performed to predict the post-exposure load-deflection responses of Reinforced Concrete (RC) beams strengthened in flexure using prestressed Near-Surface Mounted (NSM) Carbon Fibre Reinforced Polymer (CFRP) strips. Five RC beams (5.15 m [16.90 ft] long) were modeled including one un-strengthened control beam and four beams strengthened using NSM-CFRP strips prestressed to 0, 20, 40, and 60% of the ultimate CFRP tensile strain. The beams were severely deteriorated due to applying accelerated environmental conditions consisting of 500 freeze-thaw cycles: three cycles per day between +34°C [93°F] to -34°C [-29°F] with fresh water spray for 10 minutes at a rate of 18 L/min [4.8 gallon/min] at temperature +20°C. The accelerated environmental conditions used in this study equivalent to 0.46 year of exposure inside a chamber, corresponds to a minimum lifetime of 12.8 years in Canada. Simultaneously, each beam was subjected to a sustained load equal to 62 kN [13.9 kip] representing 47% of analytical ultimate load of the non-prestressed NSM-CFRP strengthened RC beam. The degradation which occurred in the concrete properties, concrete-epoxy interface, and steel reinforcement was considered in the FE model. Also, debonding at the concrete-epoxy interface was simulated by assigning shear and normal fracture energies and the prestressing was applied to the CFRP strip using an equivalent temperature. The FE model was validated with the experimental test results. However, the experimental and numerical load-deflection curves were comparable up to yielding but after yielding, the predicted curves were not in good agreement with the experimental ones.


Document: 

SP304-04

Date: 

October 27, 2015

Author(s):

R. Koch and J. Karst

Publication:

Symposium Papers

Volume:

304

Abstract:

With constrained transportation budgets there is a great need to increase the service life of bridges. Typically the deck is the weak link in the durability of a bridge with the corrosion of the reinforcing being the primary deterioration mechanism. Using Glass Fiber Reinforced Polymer (GFRP) to replace the traditional steel reinforcing eliminates reinforcing-related corrosion and should significantly increase the service life of the deck. The I-635 Bridges over State Ave in Kansas City, KS were built in the late 60’s and had an extensive history of repairs and overlays. In 2013 KDOT decided to replace the decks with traditional epoxy coated steel in the northbound bridge and GFRP reinforcing in the southbound bridge. There was a small premium to use GFRP rebar over traditional steel reinforcing which is expected to be offset by an increase in the service life of the deck. A picture of the reinforcing for the new bridge deck is shown in Figure 1.


Document: 

SP304-02

Date: 

October 27, 2015

Author(s):

Fatmir Menkulasi, Doug Nelson, Carin L. Roberts Wollmann and Tommy Cousins

Publication:

Symposium Papers

Volume:

304

Abstract:

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.


Document: 

SP304-01

Date: 

October 27, 2015

Author(s):

Junwon Seo, Yail J. Kim, and Shadi Zandyavari

Publication:

Symposium Papers

Volume:

304

Abstract:

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 (tf), steel reinforcement ratio (ρ), concrete strength (fc), 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 tf parameter are significant factors influencing the effective strain of FRP-strengthened beams.


Document: 

SP304-06

Date: 

October 27, 2015

Author(s):

E.S. Hernandez, and J.J. Myers

Publication:

Symposium Papers

Volume:

304

Abstract:

Self-consolidating concrete (SCC), as defined by ACI 237R-07, is a very flowable, non-segregating concrete that can spread into placed, fill the formwork and encapsulate the reinforcement without any mechanical consolidation. SCC, compared to traditional concrete mixtures, has primary benefits that include a reduction in equipment and labor associated costs as well as higher construction effectiveness. Innovative materials such as high volume fly ash concrete (HVFAC), represent a substantial advantage to producing stronger, more durable cast-in-place (CIP) concrete members. A level of 50% fly ash to cement proportion, as well as both normal strength self-consolidating concrete (NS-SCC) and high strength self-consolidating concrete (HS-SCC), were employed in the implementation project for Missouri Bridge A7957. The objective of this research was to provide an implementation test bed and showcase for the use of these materials. The serviceability and structural performance, both short-term and long-term, of the concrete members within the bridge were monitored in an effort to investigate the in-situ performance of not only SCC but also HVFAC. The initial instrumentation program consisted of obtaining the temperature, strain, and deflection data for the different components within the bridge’s structure, from casting through service conditions. The results obtained from this two-year monitoring program will lead to propose certain specification requirements that can be used for future project implementations.


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