Why crank bar provided in slab
WHY CRANK BARS ARE PROVIDED IN SLAB:
Different shape of bent up bars and cranks are provided in the slab and other structural
members. Bars are bent near the supports normally at an angle of 45°. The angle bent may also
be 30° in shallow beams where the (effective depth < 1.5 breadth).
The slab is supported at two ends. The maximum tensile stress that is positive moments
(sagging) acting in the middle of the slab and the maximum compressive stress that is negative
moments (hogging) acting at both ends of support. So bottom steel is required at the mid span
and top steel resists negative moments at the supports. A bent-up bar called as crank bar is
provided to make RCC slab safe from compressive stresses.
When bent up bars are provided, the strength and deformation capacity of slabs with bent up
bars compared to slabs without bent up bars is sufficiently increased.
So crank bars are generally provided
1. To resist negative bending moment (hogging).
2. To resist shear force which is greater at supports.
3. To reduce the risk of a brittle failure of slab-column connection.
4. To reduce the amount of steel used.
5. For the economization of materials.:
Different shape of bent up bars and cranks are provided in the slab and other structural
members. Bars are bent near the supports normally at an angle of 45°. The angle bent may also
be 30° in shallow beams where the (effective depth < 1.5 breadth).
The slab is supported at two ends. The maximum tensile stress that is positive moments
(sagging) acting in the middle of the slab and the maximum compressive stress that is negative
moments (hogging) acting at both ends of support. So bottom steel is required at the mid span
and top steel resists negative moments at the supports. A bent-up bar called as crank bar is
provided to make RCC slab safe from compressive stresses.
When bent up bars are provided, the strength and deformation capacity of slabs with bent up
bars compared to slabs without bent up bars is sufficiently increased.
So crank bars are generally provided
1. To resist negative bending moment (hogging).
2. To resist shear force which is greater at supports.
3. To reduce the risk of a brittle failure of slab-column connection.
4. To reduce the amount of steel used.
5. For the economization of materials.
Different shape of bent up bars and cranks are provided in the slab and other structural
members. Bars are bent near the supports normally at an angle of 45°. The angle bent may also
be 30° in shallow beams where the (effective depth < 1.5 breadth).
The slab is supported at two ends. The maximum tensile stress that is positive moments
(sagging) acting in the middle of the slab and the maximum compressive stress that is negative
moments (hogging) acting at both ends of support. So bottom steel is required at the mid span
and top steel resists negative moments at the supports. A bent-up bar called as crank bar is
provided to make RCC slab safe from compressive stresses.
When bent up bars are provided, the strength and deformation capacity of slabs with bent up
bars compared to slabs without bent up bars is sufficiently increased.
So crank bars are generally provided
1. To resist negative bending moment (hogging).
2. To resist shear force which is greater at supports.
3. To reduce the risk of a brittle failure of slab-column connection.
4. To reduce the amount of steel used.
5. For the economization of materials.:
Different shape of bent up bars and cranks are provided in the slab and other structural
members. Bars are bent near the supports normally at an angle of 45°. The angle bent may also
be 30° in shallow beams where the (effective depth < 1.5 breadth).
The slab is supported at two ends. The maximum tensile stress that is positive moments
(sagging) acting in the middle of the slab and the maximum compressive stress that is negative
moments (hogging) acting at both ends of support. So bottom steel is required at the mid span
and top steel resists negative moments at the supports. A bent-up bar called as crank bar is
provided to make RCC slab safe from compressive stresses.
When bent up bars are provided, the strength and deformation capacity of slabs with bent up
bars compared to slabs without bent up bars is sufficiently increased.
So crank bars are generally provided
1. To resist negative bending moment (hogging).
2. To resist shear force which is greater at supports.
3. To reduce the risk of a brittle failure of slab-column connection.
4. To reduce the amount of steel used.
5. For the economization of materials.
Comments
Post a Comment