Title:
Revisiting Unreinforced Strut Efficiency Factor
Author(s):
Ray Kai Leung Su and Daniel Ting Wee Looi
Publication:
Structural Journal
Volume:
113
Issue:
2
Appears on pages(s):
301-312
Keywords:
deep beam; high-strength concrete; node confinement; shear enhancement factor; shear stress limit; strut efficiency factor; strut-and-tie modeling
DOI:
10.14359/51688062
Date:
3/1/2016
Abstract:
A comprehensive experimental study investigating the strut compression strength of deep beams without stirrups by array of varying strut angles and concrete strengths is presented. The specimens were designed to strut failure, eliminating unwarranted coupled failure modes. The discrepancies of dependent parameters in strut efficiency factors were reconciled with provisions in design standards, along with various researchers’ proposals. It was affirmed that a single constant value is best to represent the strut efficiency, echoing the design recommendation in ACI 318-11. Nonetheless, a less-conservative recommendation was put forward based on the experiment and a suite of supplementary filtered database results. A compatible lower-bound shear limit to prevent strut failure was set forth to unify the strut strength and sectional shear stress limit through a generic linear shear enhancement factor. This model was found to be robust and conservative for a wide range of concrete strengths and strut angles.
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