Elastoplastic and large deflection analysis of steel frames by one element per member. II: Three hinges along member

An isolated member capacity check for beam columns may not correctly reflect the true behavior of a structure undergoing large deflection and material yielding. This paper extends the previous work by the authors on geometrically nonlinear analysis of skeletal structures to combined geometrically and material nonlinear analysis of slender frames using a single element per member. In the proposed element, three plastic hinges are allowed to form in an element with two at the two ends and one at the location of maximum combined stress due to axial force and moment. For calibration against the load capacity of a single member in the load and resistance factor design and allowable stress design standards, the present results perform excellently while, in the case of ultimate and collapse analysis of steel frames, the present method gives accurate results allowing for interaction between all members with geometric and material nonlinearities. The formulation is capable of conducting an elastoplastic buckling analysis of a beam column modeled by one element per member, which is not available in literature.