CAST (Computer Aided Strut-and-Tie) Design Tool

Abstract

The Strut-and-Tie Method (STM) is an emerging procedure for the design of D- (Discontinuity) Regions. D-Regions are those parts of a structure in which there is a complex variation in strain, such as corbels, deep beams, joints, and walls with openings. The STM design process involves idealizing that an internal truss carries the load through the discontinuity region to its boundaries, providing sufficient reinforcement to serve as the tension ties, and then checking that the compressive struts and nodal zones (joints) are sufficiently large enough to support the applied forces. While the STM is conceptually simple, calculating and modifying the dimensions of the truss and its members can be prohibitively time consuming. This paper describes a graphical design tool that enables the user to draw the D-Region to be designed, draw an internal supporting truss, select member dimensions, and select tension tie reinforcement. The program continuously recalculates the truss and nodal zone forces (and stresses), and thereby creates an efficient interactive STM design tool.