Second-order analysis and design of cables and cable-frames

Cable structures are lightweighted, simple to fabricate and reusable. They provide effective solutions for large-span structures. Analysis of cables is complex because of their highly geometrically nonlinear behavior. Based on the Lagrangian formulation and a fourth-order polynomial displacement function, the tangent stiffness matrix for a five-node curved cable element is derived and statically condensed to a simple form readily for incorporation into a frame analysis computer program. The program uses the pointwise-equilibrium-polynomial (PEP) element with initial imperfection and the "Nonlinear Integrated Design and Analysis (NIDA)" method for design and nonlinear analysis of cabled structures. Numerical examples demonstrate the robustness and practicality of the proposed method.