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 Design and Analysis (NIDA)" using 1 element per member and based on the current first-plastic-hinge or first yield design practice. The most basic parameter, stress, allowing for various linear and non-linear effects such as the P-Δ and the P-δ effects is used for strength and stability checks. Most previous work on advanced analysis cannot be used easily for production of a safe design because many important characteristics of real structures such as determination of the direction of initial imperfections in a general structure are not addressed properly. Although modeling a member by several elements for buckling analysis is sufficient, it involves complicated process in the simulation of member initial imperfection and also an inconsistent 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 stiffness under axial force, assumption of effective length and so on are no longer needed. The method permits the use of a single element per member in the structural model, as in the case for linear analysis. No additional modelling work apart from that needed for a linear analysis is required. The insertion 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 the proposed element is capable of modeling curvature along an element.