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
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| Ac | - The total area of the cross-section
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| u | - The outer circumference of the cross-section
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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
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| TRd,c | - The torsional cracking moment
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| VEd | |
| VRd,c | - The design value for the shear resistance
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The resistance TRd,c is given by the expression (6.26):
Where is: | fctd | - The design tensile strength of concrete
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| Ak | - The area enclosed by the centre-lines of the connecting walls
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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
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| TRd,max | - The design torsional resistance moment
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| VEd | |
| VRd,max | - The maximum design shear resistance
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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
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| Ak | - The area enclosed by the centre-lines of the connecting walls
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| ν | - The strength reduction factor for concrete cracked in shear
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| fcd | - The design value of concrete compressive strength
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| Θ | - The angle between the concrete compression strut and the beam axis perpendicular to the shear force
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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
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| TEd | - The design torsional moment
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| Ak | - The area enclosed by the centre-lines of the connecting walls
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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
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| s | - The spacing of the stirrups
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| fyd | - The design yield strength of the shear reinforcement
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| Θ | - The angle between the concrete compression strut and the beam axis perpendicular to the shear force
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The verification is done using following expression:
