![]() The ACI 318-19 suggests that if the compressive strength of the column concrete exceeds 1.4 times the compressive strength of the slab concrete, the column concrete should either be extended beyond the column face by a distance greater than 600 mm as shown in Fig. The current design codes (ACI 318-19 CSA A23.3-14 ( 2019)) include a provision that requires that the column can ensure proper load transfer performance when the upper/lower columns and slabs have different compressive strengths, as shown in Fig. When HSC is used for columns and NSC is used for slabs, the placement of NSC between the upper and lower HSC columns affects the load transfer mechanism of the columns. By contrast, since increasing the compressive strength of slab concrete does not significantly contribute to enhancing flexural performance, normal strength concrete (NSC) is typically used for slabs (Gamble and Klinar 1991). High strength concrete (HSC), which has a compressive strength greater than 50 MPa, has been increasingly used in a number of applications, and reducing the cross-section of the column has been shown to lead to a more efficient use of floor space (Lee and Mendis 2004). In addition, axial loading tests of isolated columns were conducted and the proposed equation was verified. Therefore, based on the analysis model established in previous research, this study has proposed an equation for calculating the effective compressive strengths of the corner, exterior and isolated columns without any confinement effects of the slab. However, there is still a lack of theoretical studies investigating the effective compressive strengths of the corner and exterior columns. For both corner and exterior columns, the confinement effect of the slab is significantly smaller than that for the interior column, and there is a more marked decrease in load transfer performance. The effective compressive strength of a column increases as it is confined by the slab, and the design codes mandate three different effective compressive strengths for interior columns (confinement on four sides), exterior columns (confinement on three sides), and corner columns (confinement on two sides). The current design codes discuss the effective compressive strengths of columns, which reflect a decrease in load transfer performance that can occur when columns and slabs have different concrete compressive strengths. ![]()
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