Additional reinforcement for torsion (Concrete beam: EC2)

Tekla Structural Designer
2021
Tekla Structural Designer

Additional reinforcement for torsion (Concrete beam: EC2)

The design value of the shear resistance of a concrete section with no shear reinforcement, VRd,c is given by;1

VRd,c = νmin * bw * d

For design in accordance with UK NA, EC2 Recommendations, Irish NA, Malaysian NA and Singapore NA;

CRd,c = 0.18/γC

γC = 1.5

νmin = 0.035 * k1.5 * fck 0.5

where

k = MIN(1 + √(200/d), 2.0) d in mm

For design in accordance with UK NA, EC2 Recommendations, Irish NA, Malaysian NA and Singapore NA;

αct = 1.0

γC = 1.5

If (ΤEd,maxRd,c) + (VEd,max/VRd,c) ≤ 1.0

THEN no additional longitudinal reinforcement for torsion is required.

IF (ΤEd,maxRd,c) + (VEd,max/VRd,c) > 1.0

THEN additional longitudinal reinforcement for torsion, A slT,reqd is required in some or all regions.

The additional longitudinal reinforcement is given by;

AslT,reqd = (ΤEd * uk* cotθ)/(2 * Ak * fyd)

where

uk = 2*((h-tef)+(bw-tef))

This reinforcement is in addition to that required for bending and tension arising from vertical shear and it is distributed in each of the four faces of the beam in proportion to the length of the face of the cross-section.

The area of the additional link reinforcement that is required to resist torsion is given by;

Aswt/s = (ΤEd)/(2 * Ak * 0.9 * fywd* cotθ) per leg

1 The design value of the shear resistance is calculated ignoring the longitudinal reinforcement as it is not known if this reinforcement is adequately anchored beyond the point under consideration. This is a conservative approach.
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