A beam will not fail if there is a good anchorage bond between steel and concrete. In such case, the beam will not be affected even bond get damaged along the entire span. If a valuable resistance is provided against the slipping of the beam along the entire span than it leads to smaller cracks with little wider. There are four main factors that affect the width of crack very much. These are;
- Shape of bar
- Stresses in reinforcement
- Concrete cover
- Steel/ reinforcement distribution
Shape Of Bar
Flexural beams with smooth rounded bars will show a comparatively small number of cracks during the service. Similarly, if the beam is comprised of well slip resistance than it will show a large number of very fine cracks i.e., a hairline cracks that are invisible to the casual eye. Now in common practice bars are always provided after surface deformations. ASTM has specified the spacing and minimum height criteria’s in A 615, A 706, and A 996 codes.
Stress in Reinforcement
Stress in the reinforcement is the second main factor that was studied by Gergely and Lutz. They have proved that the width of the crack is directly related to
Concrete Cover
Spacing and width of cracks depends on the distance
Reinforcement distribution
As concrete is weak in tension, therefore cracks width depends on the steel distribution at the tension face of the beam. Cracking can be controlled by providing a larger number of smaller diameter bars instead of larger diameter and a small number of bars in the required area of steel. Spacing between reinforcing bar should be equal.