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Recommended improvements to current shear-friction provisions of model code
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| The shear-friction theory, first proposed by Birkeland and Birkeland (1966), was adopted by CEB-FIP Model Code 1990 to predict the longitudinal shear strength between parts of concrete members cast at different times. This is a relevant subject for different situations, such as the connection between precast members with cast-in-place parts and strengthening of existing RC members with a new concrete layer. Other situations, such as corbels; metallic supports subjected mainly to shear forces; regions near supports; and the connection between columns and foundations can also be designed using the shear-friction theory. It is known that surface roughness plays a significant role on the bond strength of concrete-to-concrete interfaces. Recent studies, using a laserbased device specifically developed to quantify the texture of concrete surfaces, proved that roughness can be measured and, moreover, correlated with the cohesion and friction coefficients present in the Model Code's design expression. Therefore, the current qualitative assessment of the surface roughness, merely based on a visual inspection, can be replaced by an accurate and quantitative approach. The curing conditions of the substrate concrete (old concrete) and of the added concrete layer (new concrete) are not considered either. This can have a significant influence because additional stresses can appear at the interface between both concrete layers due to differential shrinkage. Differential stiffness due to the difference between Young modulus is not addressed either. In this paper, improvements to Model Code 90's design expression for longitudinal shear strength between concretes cast at different times are recommended. Furthermore, a comparison between the design expressions proposed by the CEB-FIP Model Code 1990, the Eurocode 2 and the ACI 318 is presented. | 1.44 MB | Adobe PDF |
Advisor(s)
Abstract(s)
The shear-friction theory, first proposed by Birkeland and Birkeland (1966), was adopted by CEB-FIP Model Code 1990 to predict the longitudinal shear strength between parts of concrete members cast at different times. This is a relevant subject for different situations, such as the connection between precast members with cast-in-place parts and strengthening of existing RC members with a new concrete layer. Other situations, such as corbels; metallic supports subjected mainly to shear forces; regions near supports; and the connection between columns and foundations can also be designed using the shear-friction theory. It is known that surface roughness plays a significant role on the bond strength of concrete-to-concrete interfaces. Recent studies, using a laserbased device specifically developed to quantify the texture of concrete surfaces, proved that roughness can be measured and, moreover, correlated with the cohesion and friction coefficients present in the Model Code's design expression. Therefore, the current qualitative assessment of the surface roughness, merely based on a visual inspection, can be replaced by an accurate and quantitative approach. The curing conditions of the substrate concrete (old concrete) and of the added concrete layer (new concrete) are not considered either. This can have a significant influence because additional stresses can appear at the interface between both concrete layers due to differential shrinkage. Differential stiffness due to the difference between Young modulus is not addressed either. In this paper, improvements to Model Code 90's design expression for longitudinal shear strength between concretes cast at different times are recommended. Furthermore, a comparison between the design expressions proposed by the CEB-FIP Model Code 1990, the Eurocode 2 and the ACI 318 is presented.
Description
Conference name - 3rd International fib Congress and Exhibition, Incorporating the PCI Annual Convention and Bridge Conference 2010; Conference date - 29 May 2010 - 2 June 2010; Conference code - 126173
Fonte: https://www.researchgate.net/profile/Eduardo-Julio-3/publication/268817271_2010_RECOMMENDED_IMPROVEMENTS_TO_CURRENT_SHEAR-FRICTION_PROVISIONS_OF_MODEL_CODE/links/5478a0d60cf2a961e4877bb9/2010-RECOMMENDED-IMPROVEMENTS-TO-CURRENT-SHEAR-FRICTION-PROVISIONS-OF-MODEL-CODE.pdf
Fonte: https://www.researchgate.net/profile/Eduardo-Julio-3/publication/268817271_2010_RECOMMENDED_IMPROVEMENTS_TO_CURRENT_SHEAR-FRICTION_PROVISIONS_OF_MODEL_CODE/links/5478a0d60cf2a961e4877bb9/2010-RECOMMENDED-IMPROVEMENTS-TO-CURRENT-SHEAR-FRICTION-PROVISIONS-OF-MODEL-CODE.pdf
Keywords
Repair Rehabilitation Standards Specifications Design codes
Pedagogical Context
Citation
Santos, P. M., & Júlio, E. N. B. S. (2010, May). Recommended improvements to current shear-friction provisions of model code. In Proceedings of the 3rd fib International Congress, Washington, DC, USA (p. 21).
Publisher
Precast Prestressed Concrete Institute
CC License
Without CC licence