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Effective Use of the Strut-and-Tie Method per ACI 318-19, Part 2 of 2
Tuesday, October 19, 2021 1:00 PM - 3:00 PM
The strut-and-tie method (STM) is an approach to evaluate or design any structural concrete member, or discontinuity region in a member, by modeling the member or region as an idealized truss. The concepts behind the development of the STM will be presented, as well as “What’s New” in the ACI 318-19 code. The session will include the fundamentals of STM as well as practical examples; accordingly, the session is geared toward practitioners and educators who use or would like to learn more about the strut-and-tie provisions in the ACI 318 code.
(1) Develop the skills to apply the strut-and-tie method in real world engineering applications;
(2) Identify the advantages of utilizing the strut-and-tie method;
(3) Evaluate and interpret the behavior of a structure designed by the strut-and-tie method;
(4) Identify the different types of discontinuity regions.
This session has been approved by AIA and ICC for 2 PDHs (0.2 CEUs). Please note: You must attend the live session for the entire duration to receive credit. On-demand sessions do not qualify for PDH/CEU credit.
Stepped Beam with Multiple Load Combinations
Presented By: Adam Lubell
Affiliation: Read Jones Christoffersen Ltd.
Description: A simply supported stepped beam having multiple disturbed regions is designed. The beam, consisting of a 3’-5” (1041 mm) cantilever span and a 16’-10” (5131 mm) back-span, is required to support an intensive green roof on the tenth floor of a 14-story office building. The cantilever and part of the back-span support the roof. The remainder of the back-span is 16” (406 mm) deeper and supports the office floor. The beam is subjected to tributary area loads from the green roof and the offices. A spandrel beam is indirectly supported on the cantilever section of the stepped beam. Since the disturbed regions at the column supports, indirect support, and at the step render the majority of the beam as disturbed, the entire beam is designed using strut-and-tie models in accordance with ACI 318-19. This design example considers multiple load combinations resulting in different strut-and-tie truss analysis models.
Design of Knee Joints with Curved-Bar Nodes Using ACI 318-19
Presented By: Christopher Williams
Affiliation: Purdue University
Description: Provisions for the design of curved-bar nodes were introduced in ACI 318-19. Experimental research investigating the curved-bar node design provisions will be described. Additionally, the design of a curved-bar node in a knee joint will be presented.
Practical Design Example: Strut-and-Tie Modeling of a Spread Footing
Presented By: Jeffrey Rautenberg
Affiliation: Wiss, Janney, Elstner Associates
Description: A practical design example will be presented to demonstrate how strut-and-tie modeling can be used for a spread footing. The footing will also be designed using sectional analysis procedures, and the results will be compared.
Deep Members with Openings
Presented By: Daniel Kuchma
Affiliation: Tufts University
Description: In many design problems, particularly those with internal openings, there are many shapes of the strut-and-tie models that can be identified and designed to carry the imposed loadings. Experimental tests and analyses suggest that nearly all shapes can be used to design a structure that will have sufficient capacity. However, the service level performance and ductility of these structures are strongly influenced by the selected shape of model. The importance of the selected shape of the strut and tie model is examined.
Strut-and-Tie Model Design for Deep Pile Caps with Tension Piles
Presented By: Widianto Widianto
Description: Two approaches (sectional design and Strut-and-Tie Model (STM) design) are presented for designing deep pile-caps under a combination of axial load, shear, and moment that produces tension in some piles. The sectional design method is similar to that used for traditional design of thin slabs or slender footings using the ACI 318 Building Code. Several potential problems with the sectional design approach based on ACI 318 Code for deep pile-caps are discussed. The differences in designing and detailing of final reinforcement based on the sectional design and the STM design are discussed.