Tension stfiffening in RC beam
Tension stfiffening in RC beam
(OP)
When there is steel (bottom layer) in a concrete beam,the steel is in compression while the concrete in tension when the section shrink. So, how does it form tension stiffening in the beam when cracks start?
How does tension stiffening help to reduce cracking moment?
Thank you for your help!
How does tension stiffening help to reduce cracking moment?
Thank you for your help!






RE: Tension stfiffening in RC beam
Between the cracks, the concrete can still carry some tension stress, developed by the bond between the concrete and the reinforcing.
In strength design this is ignored and the concrete is assumed to carry no stress when it is in tension. For deflection and, for some codes, for crack control, the tension in the concrete between the cracks can be taken into account.
This is called tension stiffening.
The shrinkage will modify the stresses in the concrete but the tension face steel will still be in tension.
RE: Tension stfiffening in RC beam
RE: Tension stfiffening in RC beam
The cracking moment is reduced by any pre-existing tension stresses in the beam, such as those caused by concrete shrinkage.
RE: Tension stfiffening in RC beam
RE: Tension stfiffening in RC beam
No, if the concrete is free to shrink, there is no stress induced.
The reinforcement inside the concrete restrains the shrinkage and induces tension stresses in the concrete. If the reinforcement is near one of the faces of the concrete then this tension stress will be greatest on that face. Whether this is considered to be an increase in the applied load tension or a reduction in the cracking moment is another matter. Because it is an internal effect and easier to include in this way, the Australian code treats it as a reduction in the tensile strength of the concrete and thus a reduction in the cracking moment.