Shear Behaviour of Concrete Slabs and Beams Reinforced with High-Performance ASTM A1035 Steel

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  • High-performance steel bars manufactured to conform to ASTM A1035-11 have different metallurgy and microstructure than conventional reinforcing steel. These changes result in an effective yield strength significantly higher than conventional ASTM A615 steel while also being less susceptible to corrosion. Thus there is increasing interest in the use of ASTM A1035 steel to reduce life-cycle costs for new concrete structures. However, the lack of a well defined yield point for this material requires careful assessment of structural design models to ensure that they accurately account for influences from higher reinforcement strains. This research focuses on the behaviour of shear-critical concrete members containing ASTM A1035 steel reinforcement. Laboratory tests were completed for six slab strips and ten beams with overall heights ranging from 300 mm to 1000 mm and shear span to depth ratios of 3.0 – 3.6. In the current study the term “SLABS” refer to concrete members longitudinally reinforced with ASTM A1035 steel without stirrups and “BEAMS” refer to members with stirrups containing combinations of ASTM A1035 or Grade 420 steel. The influence on shear and deflection behaviour from the reinforcement configurations and the nonlinear stress-strain response of the ASTM A1035 steel were of primary interest. General analytical shear models were developed for members containing ASTM A1035 steel. Simplified design shear models were also developed where thelongitudinal ASTM A1035 reinforcement is proportioned on the basis of 690 MPa yield strength. All models were validated using the new experimental test results and data from the literature. The proposed shear models were also compared with existing analytical and numerical models. Improved capacity predictions were obtained from models that directly account for the influence of reinforcement strains and member depth. It was observed that the service load deflections of beams were underestimated by existing code deflection models such as the ACI ITG–6R-10 direct deflection model. Based on parametric studies, general deflection model and simplified deflection equations were developed for the beams containing ASTM A1035 steel reinforcement. The equations were validated against test results and were shown to be useful for deflection calculations in the design industry.

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    Attribution-NonCommercial 3.0 International