Relation Between High Strength reinforcing Bars and Maximum Allowable Strain in High Strength Concrete

This thesis explores the use of ASTM A1035 Grade 100 (690 MPa) steel reinforcing bars with or without high-strength concrete (HSC) in short reinforced concrete (RC) columns. The study is driven by the potential of using high-strength steel (HSS) in the construction industry for the purpose of optimizing material weight and providing solutions to reinforcing bar congestion in RC columns. The study also aims to gain a better understanding of the behavior of RC columns reinforced with HSS bars with or without HSC in comparison to those that are reinforced with conventional steel bars (ASTM A615 Grade 60 (420 MPa) steel). First, a literature review on the behavior of HSC and HSS was conducted, also shedding light on important parameters influencing the behavior of short RC columns under compression. Then, the selection of appropriate stress-strain models for unconfined and confined concrete and for conventional and high strength steel was determined. Following, algorithms were developed using the programming language Python to analyze the behavior of HSC sections reinforced with HSS bars. Using the selected stress-strain models, sectional analyses were conducted to study whether increasing the maximum yield stress of reinforcing steel bars to 100,000 psi can be justified for unconfined or confined RC columns under the provisions of the ACI 318-19 code. The interaction between axial load and bending moment capacity was examined for RC columns with HSS and HSC. Moment-curvature analysis was conducted for sections with HSS to examine the effect of high-strength steel on curvature ductility. Finally, finite element analysis (FEA) was conducted with the concrete damage plasticity (CDP) model based to predict the test results of RC columns with HSS bars conducted by Wang et al. (2023).