A practical design method for semi-rigid composite frames under vertical loads

Although the benefits of semi-rigid connections and composite actions of slabs are extensively documented in the design of steel frames, they are not widely used in practice. The primary cause is the lack of appropriate practical design methods. In this paper, a practical method suitable for the design of semi-rigid composite frames under vertical loads is proposed. The proposed method provides the design of the connections, beams and columns for semi-rigid composite frames at the ultimate and serviceability limit states. The rotational stiffness of beam-to-column connections for calculating the deflection of the frame beams and the effective length factor of columns are also determined. In addition, the accuracy of the proposed design method is verified by a pair of tests carried out on full-scale semi-rigid composite frames. Moreover, a design example is proposed to demonstrate the application of the proposed design method. It is shown that the proposed design method not only takes into account the actual behavior of the beam-to-column connections and its influence on the behavior of the overall structures, but is also simple and convenient for a designer to use in engineering practice.