Reinforced concrete is used worldwide in the construction industry. In past eras, extensive research has been conducted and has clearly shown the performance of stress–strain behaviour and ductility design for high-, standard-, and normal-strength concrete (NSC) in axial compression. Limited research has been conducted on the experimental and analytical investigation of low-strength concrete (LSC) confinement behaviour under axial compression and relative ductility. Meanwhile, analytical equations are not investigated experimentally for the confinement behaviour of LSC by transverse reinforcement. The current study experimentally investigates the concrete confinement behaviour under axial compression and relative ductility of NSC and LSC using volumetric transverse reinforcement (VTR), and comparison with several analytical models such as Mender, Kent, and Park, and Saatcioglu. In this study, a total of 44 reinforced-column specimens at a length of 18 in with a cross-section of 7 in × 7 in were used for uniaxial monotonic loading of NSC and LSC. Three columns of each set were confined with 2 in, 4 in, 6 in, and 8 in c/c lateral ties spacing. The experimental results show that the central concrete stresses are significantly affected by decreasing the spacing between the transverse steel. In the case of the LSC, the core stresses are double the central stress of NSC. However, increasing the VTR, the capacity and the ductility of NSC and LSC increases. Reducing the spacing between the ties from 8 in to 2 in center to center can affect the concrete column’s strength by 60% in LSC, but 25% in the NSC. The VTR and the spacing between the ties greatly affected the LSC compared to NSC. It was found that the relative ductility of the confined column samples was almost twice that of the unrestrained column samples. Regarding different models, the Menders model best represents the performance before the ultimate strength, whereas Kent and Park represents post-peak behaviour.
<p>To investigate the failure mode and effect on a steel girder negative bending behavior of an SFRC composite deck, eccentric tension tests and numerical simulations were conducted on C50 concrete composite deck and SFRC composite deck specimens. Furthermore, parametric analysis via girder segment finite element models was carried out for summarizing the influences of the composite deck on the steel box girder performance. The test and simulation analysis results showed that the residual contribution of SFRC slab to the axial tensile stiffness of composite deck was 36% as cracking up to 0,10 mm, while that of C50 concrete slab was only 15%. Moreover, the parametric analysis results showed that the residual contribution of SFRC slab to the bending stiffness of steel girder was twice that of C50 concrete slab. When SFRC crack width reached 0.10 mm, the bending stiffness of the main girder was reduced by 11% compared with the intact state.</p>
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