A second-order flexibility-based beam-column element with member imperfection

In this paper, a new flexibility-based beam-column element with member initial imperfection is proposed for direct analysis or second-order inelastic analysis of steel structures. In past decades, the stiffness-based elements gain great successes in handling large deflection problems while the flexibility-based elements play a dominant role in plastic analysis. Apart from the merits of the above two types of elements, the proposed flexibility-based type element considers member initial imperfection and distributed plasticity along the member length and therefore one element is generally sufficient to model a member for practical design. On the contrary, several stiffness-based elements are required to model a member in order to capture the plastic behavior of member under complex loads. The conventional flexibility-based type elements cannot meet the codified requirements of direct analysis as they do not take member initial imperfection into account and this limitation is removed in the new element proposed in this paper. Several examples are given in this paper to illustrate the accuracy and validity of the proposed element.