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Through the punching shear test of six hollow slab-column connection specimens, the mechanic parameters of the hollow slab-column connection were collected, including the cracking load, the ultimate load, the displacement of the slab bottom and the strain data of steel and concrete under the influence of the unbalanced bending moment. Afterward the effect of the hollow ratio and the bending direction on the ultimate punching shear capacity of hollow slab-column connection was studied. The test results show that the capacity of hollow slab-column connection decreases with the increase of hollow ratio, but only within a narrow range. When the unbalanced moment is low, both the horizontal unbalanced moment and the along pipe unbalanced moment create almost the same impact on the punching connection. The punching capacity of the hollow slab-column connection under two-way unbalanced moment is lower than that under one-way unbalanced moment, but the final displacement is larger and the deformation ability is better. Finally the relationship between the unbalanced moment and the ultimate bearing capacity of hollow slab-column connection was proposed.

To investigate the punching shear capacity of cast-in-situ reinforced concrete hollow slab-column connections under the unbalanced bending moments, a series of specimens were tested and analyzed in this paper. Hollow ratio, direction of moment, tube layout pattern and other factors are considered in the experiment. Performance of the specimens was evaluated in terms of cracking load, ultimate bearing capacity, fracture distribution and load-displacement curve. Moreover, the punching shear capacity formula of the hollow slab-column connections was provided. The experimental results show that the failure patterns of the specimens are punching failure; stiffness improved with the increase of thickness. Under one-direction unbalanced moment, the punching shear capacity decreases with the increase of hollow ratio; Under bi-direction unbalanced bending moment, the punching shear capacity increases with the increase in hollow ratio; the punching shear capacity is higher when bending moment along the tube compared to bending moment cross the tube, but it is not obvious; the specimens under bidirection unbalanced moment have lower punching shear capacity and better deformation ability compared with specimens under one-direction unbalanced moment. Using the proposed punching shear capacity formula, the calculated values are in good agreement with measurements.