Design of Concrete Structures Using High-Strength Steel Reinforcement (2011) / Chapter Skim
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From page 5... ...
The AASHTO LRFD Bridge Design Specifications (2007) , however, limit the yield strength of reinforcing steel to 75 ksi for most applications.
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1.2 Objectives of NCHRP Project 12-77 The objective of the study presented in this report is to evaluate existing AASHTO LRFD Bridge Design Specifications relevant to the use of high-strength reinforcing steel and other grades of reinforcing steel having no discernable yield plateau. The focus of the experimental phase of this study is the use of ASTM A1035 (2009)
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Representative Stress-Strain Curves for A1035 and A615 Reinforcing Steel.
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Mast et al. studied the behavior of concrete beams subject to flexural and axial loads at service level and nominal strength and determined the section behavior using a cracked section analysis that satisfied equilibrium and compatibility.
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. 1.3.4 Shear Reinforcement The shear behavior of reinforced-concrete beams is not well understood and calculation of the shear strength is based on semi-empirical relationships.
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. Strength and deformability of concrete are known to be inversely proportional; therefore, more confinement is required in order for high-strength concrete columns to reach levels of deformation expected of well-detailed normal-strength concrete columns.
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(2009) assessed the present empirical development length equations prescribed by ACI 318 (2008)
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approach of directly assessing cracking behavior of concrete beams was dropped by ACI 318 in 1999 and by AASHTO in 2005 in favor of a simplified version of the alternative approach proposed by Frosch (1999 and 2001) that prescribed spacing limits for longitudinal reinforcing steel thereby indirectly controlling crack width.
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From page 13... ...
In the commentary to §5.7.3.4, AASHTO describes the use of the γd term to calibrate Equation 5 for any desired crack width limitation. It is well established that crack control is improved by using a larger number of well-distributed, smaller diameter bars to make up the required area of flexural reinforcing steel.
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From page 14... ...
A summary of corrosion performance of reinforcing steel is presented in Appendix A and provides quantitative data available in the literature. 1.4 Survey of Use of High-Strength Steel Reinforcement in Bridge Structures A written survey intended to assess the current practice and the use of high-strength reinforcing steel was disseminated in June 2007.
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From page 15... ...
1.4.2 Reported Use of A1035 Reinforcing Steel in Highway Bridge Infrastructure MMFX Inc., the only supplier of A1035 reinforcing steel, reports 25 U.S. and 4 Canadian jurisdictions that have used A1035 reinforcing steel in at least one bridge project as of December 2009.
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