Document Type
Dissertation
Degree
Doctor of Philosophy (PhD)
Major/Program
Civil Engineering
First Advisor's Name
David Garber
First Advisor's Committee Title
Committee chair
Second Advisor's Name
Atorod Azizinamini
Second Advisor's Committee Title
Committee member
Third Advisor's Name
Irtishad Ahmad
Third Advisor's Committee Title
Committee member
Fourth Advisor's Name
Arindam Gan Chowdhury
Fourth Advisor's Committee Title
Committee member
Fifth Advisor's Name
Ton-Lo Wang
Fifth Advisor's Committee Title
Committee member
Keywords
deep beams, strut-and-tie method, node behavior, failure mode, strut strength
Date of Defense
6-11-2018
Abstract
The strut-and-tie method (STM) is a simple and conservative method for designing concrete structures, especially deep beams. This method expresses complicated stress patterns as a simple truss or kinematic model made up of compression elements (struts), tension elements (ties), and the joints between elements (nodes). STM is based on lowerbound plasticity theorem, so using it properly will lead to a conservative design. Although the concepts of STM have been around in concrete design since the late 19th century, STM was first introduced in AASHTO LRFD in 1994 and ACI 318-02 in 2002. ACI 318 defines two different types of struts (prismatic and bottle-shaped) based on whether compression stress can spread transversely along the length of the strut. Recent work has brought into question whether these two types of struts do exist and whether current design provisions conservatively estimate failure loads for all members. The performance of struts and nodes were investigated experimentally by testing six fullscale concrete deep beams. The specimens had two different shapes (rectangular and trusslike), two different shear span-to-depth ratio (1 and 1.6), and three different types of development (externally unbonded bars, internally bonded hooked bars, and internally bonded bars with welded external plates). All the specimens were supported vertically and vii tested under a three-point load setup. Based on the results, the truss-like specimen failed at higher loads than rectangular specimens with the same shear span-to-depth ratio. According to these results and recent debate in the literature, bottle-shaped struts are not weaker than prismatic struts because of their shape. They are weaker due to shear failure where struts cross a diagonal tension field. Therefore, the structures should be separately checked for shear strength when they are designed with STM. In this dissertation, the development of the design equation for shear strength of discontinuity regions was introduced, and the procedure is under consideration for adoption in ACI 318-19. This research was expanded numerically by studying the effect of development type and length, strut type, and strut angle on the behavior of concrete deep beams. The crack patterns and load-displacement curves, which were obtained from experimental tests, were used to validate numerical models. The strength of concrete deep beams was assessed by modeling thirty-five specimens in a nonlinear finite element software. According to the results, development length and development types influenced the presence of tensile stress in the support nodes. Additionally, the effect of the tensile stresses from reinforcement development and diagonal tension were not additive in rectangular specimens.
Identifier
FIDC006887
ORCID
https://orcid.org/0000-0002-1283-7989
Recommended Citation
Rezaei, Nazanin, "Study on Strut and Node Behavior in Strut-and-Tie Modeling" (2018). FIU Electronic Theses and Dissertations. 3749.
https://digitalcommons.fiu.edu/etd/3749
Included in
Civil Engineering Commons, Construction Engineering and Management Commons, Structural Engineering Commons
Rights Statement
In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/
This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).