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Torsion (ULS)

The torsional resistance is calculated according to the chapter 6.3 of EN 1992-1-1. The analysis is based on the basis of a thin-walled closed section. The effective wall thickness is calculated in accordance with the chapter 6.3.2:

Where is:

tef

  • The effective wall thickness

Ac

  • The total area of the cross-section

u

  • The outer circumference of the cross-section

The torsional resistance without reinforcement

The verification in accordance with the chapter 6.3.2(5) is done for members without any torsional reinforcement:

Where is:

TEd

  • The design torsional moment

TRd,c

  • The torsional cracking moment

VEd

  • The design shear force

VRd,c

  • The design value for the shear resistance

The resistance TRd,c is given by the expression (6.26):

Where is:

fctd

  • The design tensile strength of concrete

Ak

  • The area enclosed by the centre-lines of the connecting walls

The resistance including torsional reinforcement

The capacity of the concrete struts is given by the formula (6.29):

Where is:

TEd

  • The design torsional moment

TRd,max

  • The design torsional resistance moment

VEd

  • The design shear force

VRd,max

  • The maximum design shear resistance

The design torsional resistance moment TRd,max is given by the expression (6.30):

Where is:

αcw

  • The coefficient taking account of the state of the stress in the compression chord, value is 1.0

Ak

  • The area enclosed by the centre-lines of the connecting walls

ν

  • The strength reduction factor for concrete cracked in shear

fcd

  • The design value of concrete compressive strength

Θ

  • The angle between the concrete compression strut and the beam axis perpendicular to the shear force

The design shear force in the transverse reinforcement VEdt is given by the expression

Where is:

VEdt

  • The design shear force in the transverse reinforcement caused by torsional moment

TEd

  • The design torsional moment

Ak

  • The area enclosed by the centre-lines of the connecting walls

The design resistance of the transverse reinforcement VRdt is given by the expression:

Where is:

Asw

  • The cross-sectional area of the transverse reinforcement considered for the torsional resistance

s

  • The spacing of the stirrups

fyd

  • The design yield strength of the shear reinforcement

Θ

  • The angle between the concrete compression strut and the beam axis perpendicular to the shear force

The verification is done using following expression:

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