The flat plate slab system is widely used in construction fields due to its excellent constructability and savings in story height compared to the conventional beam-column moment-resisting system. Many researchers are, however, concerned about the punching shear failure that can happen in a two-way flat plate slab system, for which many shear-strength-enhancement techniques have been suggested. One of the effective alternatives is the application of steelfiber-reinforced concrete. However, most previous studies on the punching shear strength of steel-fiber-reinforced concrete flat slabs had presented empirical formulas based on experimental results. On the other hand, theoretical models proposed in previous studies are difficult to be applied to practical situations. Therefore, in this study, a punching shear strength model of the steel-fiber-reinforced concrete two-way flat slab is proposed. In this model, the total shear resistance of the steel-fiber-reinforced concrete flat slab is expressed by sum of the shear contribution of steel fibers in the cracked tension region and that of intact concrete in the compression zone. A total of 91 shear test data on steel-fiberreinforced concrete slab-column connection were compared to the analysis results, and the proposed model provided a good accuracy on estimating the punching shear strength of the steel-fiber-reinforced concrete flat slabs.

Structural performance of a reinforced concrete (RC) column is greatly influenced by its slenderness ratio. Especially, under the elevated temperature, secondary moment can be additionally induced by the loss of cross-section. In this study, therefore, the axial force-flexural moment (P-M) interaction model of a RC column exposed to fire was proposed, which considers the slenderness effect due to fire damage. The 500 °C isotherm method presented in Eurocode2 was adopted to consider the fire damage, and the nonlinearity of materials was also reflected. In addition, in order to consider initial imperfection, the maximum axial strength was limited by Rankine load. The proposed P-M interaction model was verified with test results collected from existing studies. The results showed that the proposed model evaluated the fire-resisting performance of the specimens very accurately.

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