Evaluation of existing strut-And-tie methods and recommended improvements

The objective of the study summarized in this paper was to develop simple, accurate, and conservative guidelines for the design of deep beams and discontinuity regions. To accomplish this goal, the authors compiled a database of 868 deep-beam shear tests from the literature and fabricated and tested 37 additional deep-beam specimens. The cross-sectional dimensions of the specimens that were tested included 36 × 48 in. (910 × 1220 mm); 21 × 75 in. (530 × 1910 mm); 21 × 42 in. (530 × 1070 mm); and 21 × 23 in. (530 × 580 mm). A comprehensive analysis of the database resulted in the following conclusions: 1) deep-beam shear design provisions of ACI 318-11 and AASHTO LRFD (2010) are overly conservative; and 2) the accuracy of existing design provisions can be improved without compromising their conservative nature. Accordingly, the authors propose recommendations to these methods to form an improved strut-And-tie modeling procedure. The transparently derived procedure is based on fundamental principles, current provisions, and experimental data. The authors recommend adoption of the proposed modifications into the ACI 318 and AASHTO LRFD provisions. An example problem illustrating the use of the proposed method is provided in the Appendix.