P11.02: Experimental analysis and FE modeling of square hollow sections under combined axial and bending loads

The seismic performance of steel frames strongly depends on the non‐linear behaviour of beams and column because the plastic zones are concentrated in beams’ ends and at the base of the columns of the first storey. Therefore, in order to guarantee an appropriate behaviour of the whole frame, it is necessary to characterize the response of steel member up to failure. Dealing with the characterization of the non‐linear response of beams, many experimental works are currently available both for I and hollow sections. In addition, predictive models based on regression analyses able to provide both the ultimate resistance and rotation capacity of steel members, even though they always make reference only to the case of pure non‐uniform bending. As previously mentioned, the overall frame response is strongly influenced also by the non‐linear behaviour of columns, and an accurate prediction of their combined axial and bending vs rotation response is needed in order to control the seismic behaviour of the frame. In order to predict the ultimate resistance and rotational capacity of steel members subjected not only to bending but also to axial loads, two kinds of experimental testing and an analysis joint activity carried out. The monotonic behaviour of SHS subjected to bending only or combined bending and axial loads are investigated. Subsequently, numerical analysis are conducted to extend the experimental sample. At the end, the results of the experimental end FE work are used to calibrate a model able to express the ultimate resistance of SHS as a function of the main geometrical and mechanical parameters of the section.