Non-linear integrated design and analysis of skeletal structures by 1 element per member

This paper proposes a new and practical approach of "Nonlinear Integrated D esign and Analysis (NIDA)" using 1 element per member and based on the curr ent first-plastic-hinge or first yield design practice. The most basic para meter, stress, allowing for various linear and non-linear effects such as t he P-Delta and the P-delta effects is used for strength and stability check s. Most previous work on advanced analysis cannot be used easily for produc tion of a safe design because many important characteristics of real struct ures such as determination of the direction of initial imperfections in a g eneral structure are not addressed properly. Although modeling a member by several elements for buckling analysis is sufficient, it involves complicat ed process in the simulation of member initial imperfection and also an inc onsistent model to the linear analysis. The suggested method, allowing for these realistic features, is practical, accurate, direct and simple so that classification of sway or non-sway frames, checking of varied member stiff ness under axial force, assumption of effective length and so on are no lon ger needed. The method permits the use of a single element per member in th e structural model, as in the case for linear analysis. No additional model ling work apart from. that needed for a linear analysis is required. The in sertion of an additional node to the buckled member by other researchers in a problem studied in the last example of this paper is eliminated since th e proposed element is capable of modeling curvature along an element. (C) 1 999 Elsevier Science Ltd. All rights reserved.