Optimal Design of Reinforced Concrete Section Under Combined Dynamic Action

Abstract

Wind or earthquake dynamic actions produce combined efforts on structures (axial force, bending moment about one or two axes, …) whose maximum values within a member section can often be represented by an elliptical envelope. The present chapter describes a technique to optimize reinforced concrete sections subjected to this type of dynamic load by adjusting quantities of steel and/or concrete so that the interaction curve characterizing the resistance of the section becomes tangent to the envelope of the maximum combined forces. The method relies on a geometrical transformation from the original space of forces in which the envelope is an ellipse to a so-called “standard normal space” where it becomes the unit circle. In this latter space, the safety margin of the section has a very simple geometric expression and is measurable with well-known tools of reliability analysis. The section parameters (steel and concrete) can then be adjusted in a very efficient way.