Torsion Design Based on Thin-Walled Tube Analogy

RazorSharpAustin avatar
RazorSharpAustin
·
·
Download

Start Quiz

Study Flashcards

10 Questions

What is the main structural analogy used for designing torsion?

Thin-walled tube

In the thin-walled tube analogy, where is the torsional resistance primarily assumed to be provided from in a cracked reinforced concrete beam?

Outer skin of the cross-section around the stirrups

When a beam subjected to torsion has cracked, where is the torsional resistance primarily provided in the thin-walled tube analogy?

On the surface around closed stirrups

What is the approximate threshold for torques that do not cause a structurally significant reduction in either flexural or shear strength?

One-quarter of the cracking torque

In the thin-walled tube analogy, how is cracking torsion under pure torsion derived?

(0.75 Acp / Pcp)

When does cracking occur according to the thin-walled tube analogy?

When the principal tensile stress reaches 0.75 cf * lambda 33.0

In a non-prestressed beam loaded with torsion only, what is equal to the principal tensile stress?

(T/2Aot)

What part of a reinforced concrete beam is neglected in the thin-walled tube analogy for torsion?

"Core" concrete cross-section

How is a reinforced concrete beam idealized geometrically in the thin-walled tube analogy?

"Hollow section"

Which part of the reinforced concrete beam provides most of the torsional resistance after cracking according to thin-walled tube analogy?

Outer skin of cross section near stirrups

Study Notes

Design for Torsion

  • The design for torsion is based on the thin-walled tube, space truss analogy.
  • In this analogy, the core concrete cross section in a solid beam is neglected.
  • A reinforced concrete beam's torsional resistance is provided primarily by closed stirrups and longitudinal bars near the surface after cracking.
  • The thin-walled tube analogy assumes the resistance is provided by the outer skin of the cross section, roughly centered on the closed stirrups.

Idealization of Sections

  • Both hollow and solid sections are idealized as thin-walled tubes before and after cracking.

Torque Limits

  • Torques that do not exceed approximately one-quarter of the cracking torque (Tcr) can be ignored.
  • Such torques do not cause a structurally significant reduction in flexural or shear strength.

Cracking Torsion (Tcr)

  • Cracking torsion under pure torsion (Tcr) is derived by replacing the actual section with an equivalent thin-walled tube.
  • The tube has a wall thickness (t) of (0.75 Acp / Pcp) prior to cracking.
  • The area enclosed by the wall centerline (Ao) is equal to (2/3) Acp.

Cracking Criteria

  • Cracking is assumed to occur when the principal tensile stress reaches −c f λ 33.0.
  • In a non-prestressed beam loaded with torsion alone, the principal tensile stress is equal to the torsional shear stress (τ = T/(2Aot)).

Learn about the design approach for torsion in beams, which is based on the thin-walled tube space truss analogy. Explore how reinforced concrete beams resist torsion, with a focus on the role of stirrups and longitudinal bars. Understand the concept of torsional resistance in the context of the outer skin of the cross section in the design.

Make Your Own Quizzes and Flashcards

Convert your notes into interactive study material.

Get started for free

More Quizzes Like This

Use Quizgecko on...
Browser
Browser