What is Strut-Tie Model(STM)?

[ACI 318M-14 Fig. R23.2.1]

Strut-Tie Model

The strut-tie model, a generalization of the truss analogy, is a discrete representation of actual stress fields resulting from applied load and support conditions. This model represents the load-carrying mechanism of a structural member by approximating the flow of internal forces through the use of struts to represent the flow of compressive stresses and ties to represent the flow of tensile stresses.

• Strut-tie models shall consist of struts and ties connected at nodes to form an idealized truss.
• Strut-tie model approach is one of the useful design methods for shear members and D-region.
• Strut-tie model approach provides the method that can make a quite complicated concrete structure to a simple truss model.
• Strut-tie model approach can design structural concrete using various models according to load conditions, geometry, shape and location of reinforcement.

 

Component of Strut-Tie Model

1. Strut

• Compression elements
• The idealized elements of compression stress field

2. Tie

• Tensile force transmission elements

3. Node

• Intersection points of 3 or more struts and ties
• The intersection point of the centerline of struts, ties, and concentrated loads

4. Nodal Zone

• Region that the forces of struts and ties are transmitted through the node

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Reference

1. American Concrete Institute (2014) Building Code Requirements for Structural Concrete (ACI 318M-14) and Commentary(ACI 318RM-14), Farmington Hills, Michigan, USA.

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• component
• nodal zone
• node
• STM
• strut
• tie

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