Strut-and-Tie Model Design Examples for Bridges: Final Report

A series of five detailed design examples feature the application of state-of-the-art strut-and-tie modeling (STM) design recommendations. This guidebook is intended to serve as a designer’s primary reference material in the application of STM to bridge components. The examples are as follows: (Example 1) Five-Column Bent Cap of a Skewed Bridge – This design example serves as an introduction to the application of STM. Challenges are introduced by the bridge’s skew and complicated loading pattern. A clear procedure for defining nodal geometries is presented. (Example 2) Cantilever Bent Cap – A strut-and-tie model is developed to represent the flow of forces around a frame corner subjected to closing loads. This is accomplished, in part, through the design and detailing of a curved-bar node at the outside of the frame corner. (Example 3a) Inverted-T Straddle Bent Cap (Moment Frame) – An inverted-T straddle bent cap is modeled as a component within a moment frame. Bottom-chord (ledge) loading of the inverted-T necessitates the use of local STMs to model the flow of forces through the bent cap’s cross section. (Example 3b) Inverted-T Straddle Bent Cap (Simply Supported) – The inverted-T bent cap of Example 3a is designed as a simply supported member. Results for both the moment frame case and the simply supported case are compared to illustrate the influence of boundary condition assumptions. (Example 4) Drilled-Shaft Footing – Three-dimensional STMs are developed to properly model the flow of forces through a deep drilled-shaft footing. Two unique load cases are considered to familiarize the designer with the development of such models.