A standard base plate connection is commonly adopted for column bases of low-rise steel structures. In most practical design, the column bases are likely covered by shallow concrete slab to hide the bolted base plate and level the slab. There is no guideline, that reflects the influences of the slab on the seismic performance of the column base. Cyclic loading tests are conducted, and the effects of thickness and shape of slab are investigated with reference to the standard base plate connection. The tests show that the covering concrete slab contributes to both the initial stiffness and ultimate strength. The plastic theory is applied to express the punching shear failure and the compressive failure in the slab, and the ultimate strength is estimated. Reasonable correlation with the corresponding test results is notable.
