Behavior of CSC-Type Shear Connectors under Pry-Out Shear Test: Analytical Study

The use of cold-formed steel (CFS) shapes in steel-concrete composite sections has increased over the past 20 years in the construction industry worldwide. This system has constructive advantages such as high load-bearing capacity, high stiffness and ductility, ease of transportation and assembly, and full usage of the capacity of the materials. Additionally, CFS sections are considered a sustainable alternative in construction.The capacity of the system depends on the effectiveness of shear connectors during the transfer of stress between materials. Currently, the push-out experimental test follows a standardized procedure to evaluate the capacity of shear connectors in composite sections, but CFS shapes have demonstrated premature failures by local buckling, thus questioning the applicability of the experimental test for such configurations.In this research, the capacity of the proposed confined shear connectors (CSC) is evaluated in composite systems, through the alternative pry-out test methodology. From numerical models, the effects of the steel shape thickness, the thickness of concrete slabs, the compressive strength of concrete and the separation between connectors in composite systems are studied. The analysis concluded that, under this test methodology, the separation between connectors does not represent statistically significant changes in the final capacity of the composite system.

Experimental study on flexural performance of steel-reinforced concrete slim floor beams

In long-span floors, the use of composite slim floor beams can effectively improve the flexural stiffness and flexural capacity of the floor system. In order to strengthen the stiffness of the composite slim floor beams and achieve better fire resistance, an innovative steel-reinforced concrete slim floor beams is presented in this article. To investigate the flexural performance of the steel-reinforced concrete slim floor beams, static loading experiments were carried out on six specimens. The parameters of the test were the height of slim floor beams and the type and size of steel shape in the steel-reinforced concrete slim floor beams. On the basis of the experiment, the bending failure modes, flexural stiffness, and flexural capacity of the steel-reinforced concrete slim floor beams were studied comprehensively. The test results indicated that the steel-reinforced concrete slim floor beams exhibited great flexural capacity, large stiffness, and high ductility. The calculation formulas of flexural stiffness and flexural capacity were also proposed in this article. The analysis of flexural performance of the steel-reinforced concrete slim floor beams can provide a significant foundation for further research.

Effect of Intermediate Stiffeners on the Behaviors of Partially Concrete Encased Steel Beams

Partially concrete encased steel (PE) beams are composite steel beams and concrete elements that present several advantages, such as higher fire resistant, higher flexural capacity, and higher lateral torsional buckling resistant compared to bare steel beams. This paper reports an experimental study of eight PE beams under cyclic loading. The effectiveness of intermediate stiffeners, such as midspan stiffener and plastic hinge zone stiffener, in enhancing composite action and ductility of the PE beams was studied. The ductility performance of PE beams using strengthened beam-to-column connection and weakened beam-to-column connection was also investigated. The test results show that the plastic hinge zone stiffener performed well and has the potential to replace shear connectors. Strengthened and weakened beam-to-column connections can be implemented in PE beams to enhance the ductility of the PE beams; with the details of both strengthened and weakened beam-to-column connections determined by bare steel shape instead of the whole section. In addition, the suggestions to prevent premature failure of weakened beam-to-column connection were provide.

Seismic retrofit of precast soft-storey building using diagonal steel-shape memory alloy bracing device: Numerical investigation

A diagonal steel-shape memory alloy bracing device is proposed for seismic retrofitting of vulnerable building frame structure. Superelastic shape memory alloy bar is put in series with steel bars in the bracing. The device makes use of the loading plateau of superelastic shape memory alloy to limit the tensile force of diagonal bracing. A precast soft-storey building frame in Australia was selected for a case study. A numerical model of the frame was developed and validated with the results from full-scale pull-down field tests. Nonlinear time history analysis was then conducted to evaluate the seismic performance of the frame with different retrofitting strategies. The result shows that the diagonal steel-shape memory alloy bracing can reduce the displacement demand on the soft-storey frame. Meanwhile, the level of tensile force of steel-shape memory alloy bracing can be controlled by the force plateau of the shape memory alloy bar, which is recommended to be 20% of the yielding force of the steel bar. The lower tensile force demand could alleviate the force demand at the associated support connections.

Enhancing seismic performance of unbonded prestressed concrete bridge column using superelastic shape memory alloy

In this article, an application of superelastic shape memory alloy strands for improving the seismic performance of unbonded prestressed reinforced concrete bridge column is proposed. In the reinforced concrete column with unbonded prestressing steel-shape memory alloy strands, superelastic shape memory alloy strands are put in series with unbonded steel strands, and the loading plateau of shape memory alloy is exploited to limit the increase in the axial load of column under an earthquake. Quasi-static analysis and seismic analysis were conducted to compare the seismic performance of conventional reinforced concrete column, reinforced concrete column with unbonded prestressing steel strands, and the proposed reinforced concrete column with unbonded prestressing steel-shape memory alloy strands. Result shows that reinforced concrete column with unbonded prestressing steel-shape memory alloy strands has larger ultimate displacement capacity than reinforced concrete column with unbonded prestressing steel strands in the quasi-static analysis. In the seismic analysis, reinforced concrete column with unbonded prestressing steel-shape memory alloy strands suffers from smaller earthquake residual displacement than reinforced concrete column and reinforced concrete column with unbonded prestressing steel strands. Furthermore, parametric analysis was carried out to investigate the effects of unbonded steel strand ratio, prestressing force ratio, bonded longitudinal reinforcement ratio, and maximum tensile force ratio (area of shape memory alloy strands) on the ultimate displacement and quasi-static residual displacement of reinforced concrete column with unbonded prestressing steel-shape memory alloy strands. Results show that increasing the prestressing force ratio and the maximum tensile force ratio within certain ranges can improve the self-centering capability of column. Increasing the area of bonded longitudinal reinforcement and unbonded steel strand ratio results in larger residual displacement.

Numerical and Experimental Analysis of a Shear Connection Made Using a Top-Hat Profile

The paper proposed a numerical model of a shear connection between a reinforced concrete slab and a steel shape. The connection was made using a top-hat profile. A method for conducting experimental research on shear connections in the composite structures was presented. Geometric dimensions and material parameters of the analysed model of connection, on which the experimental research was conducted, were noted. The results of the conducted experimental research were compared to the results of the numerical analysis performed using ANSYS software. displecement curves were analysed for both cases and any correlation between experimental and numerical results was noted.