Title:
Load-Spread Spectrum in Strut-and-Tie Modeling of Structural Concrete
Author(s):
Mohamed E. El-Zoughiby
Publication:
Structural Journal
Volume:
118
Issue:
4
Appears on pages(s):
3-15
Keywords:
concentrated loads or reactions; deep beams and walls; discontinuity regions; equilateral-triangle; load path method; load-spread spectrum; regular-hexagon; strut-and-tie modeling; strut-tie angle
DOI:
10.14359/51732639
Date:
7/1/2021
Abstract:
The development of a strut-and-tie model (STM) using the load path method requires considering only concentrated loads or reactions. Distributed loads can be lumped into a series of (at least two) concentrated loads applied at nodes. The load-spreading (or strut-tie) angle is a key parameter in laying out an STM. Reducing the strut-tie angle to below a limiting value greatly increases the strut-tie forces, and when, by geometry, the angle is zero, no compression stresses would be permitted in a strut that is superimposed on a tension tie; strain incompatibilities with difficulty fit large struts within the space available. Two simple limiting rules—equilateral-triangle and regular-hexagon—are developed and used to define the three phases proposed for the load-spread spectrum in the strut-and-tie modeling method. The one-panel model, with(out) including web reinforcement in addition to the crack-control reinforcement required by codes, is assumed to represent the first two phases, while the two-panel model with one vertical tie represents the last phase. Sample examples are presented to justify and demonstrate the ease of implementation of the developed two rules.
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