"Strut-and-tie models are an excellent analysis tool for many design problems in concrete structures, and especially for discontinuity regions (D-regions)," says Karl-Heinz Reineck, editor of SP-208 and Chair of Subcommittee 445-A. "Where not properly analyzed and detailed, these regions can show damage or even result in brittle failure of the structure, as demonstrated by many cases."
SP-208 presents examples ranging from classical D-regions to unusual design situations, including:
- Deep beams (with and without openings)
- Dapped-end T-beam supported by an inverted T-beam
- Corbels (double and at column)
- Beam with indirect support and loading
- Prestressed beams
- Cable-stayed bridge pier table
- High wall with two openings
- Pile caps
Most of the examples have been taken from practice. In addition to explaining the approach of determining a model, they point out where problems can occur in dimensioning or in detailing and anchoring of the reinforcement and how the design could be improved.
The implementation of strut-and-tie-models in ACI 318-02 is a significant step toward more consistent design of structural concrete. SP-208 expands on the rules and guidelines given in the commentary to Appendix A by showing engineers how to apply these models in a variety of situations.
Developing and disseminating information on the best use of concrete has been the mission of ACI International for nearly a century. Founded in 1904, the international technical and educational society, headquartered in Farmington Hills, Mich., has 30,000 members and 94 chapters in 30 countries. ACI offers 14 certification programs for concrete practitioners, conducts more than 200 educational seminars annually, and produces more than 400 technical documents for improving the design, construction, maintenance, and repair of concrete structures.