Stiffness-based Approach for Preliminary Design of Framed Tube Structures Article in Press

A parametric formulation for preliminary design of tubed-system tall buildings, in which some optimality criteria and practical constraints are considered, is presented. Here, a minimum compliance optimization formulation, developed by other researchers, is applied to a framed-tube structure. The tube behavior is modeled as a cantilevered box beam. Independent variable in this problem is thickness of the box, and a formulation for its optimal value is proposed. The challenge in this research was treatment of the lower bound constraint on thickness in an analytical manner. To deal with this constraint, a critical height parameter (CH) is introduced, and the design domain is divided into two zones of constant thickness (CT) and constant curvature (CC). This definition allows for computation of optimal thickness distribution along the structure through an analytic dimensionless equation. Different static loading patterns are considered; including the concentrated, uniform, triangular and quadratic forms. A numerical example is presented to demonstrate the ease of the proposed method in application, and the analysis results are presented by charts to validate the efficiency of it.