Spacing of stirrups as per IS 456. As per the provisions of IS 456, the maximum distance between stirrups shall not exceed 300 mm or 12 inches. and is provided with at least 100 mm or 4 inches in beam and in column.
The stirrups have several name such as ring, link, lateral ties and vertical stirrups. Some people in local language say it “ring”, as technical point of view it is either called as lateral ties if it is used for column and vertical stirrup when used for reinforced beam.
Spacing between stirrups in column will varies at the ends and at central part . Generally the lateral ties are closely spaced at the ends when compared to the middle part it is done so as to overcome the buckling of column. The spacing also depends on the design of the column such as shape of the column and diameter of steel reinforcement used.
One of the important function to provide lateral reinforcement or lateral ties in columns is to hold the primary reinforcement in place before and during concreting. The longitudinal bars which are used for column could be as long as 12 meters or 40 feet and would sway in any random direction if they are not tied together. So we can say that lateral reinforcement or ties is used to tie individual bars and thus the name ties.
Spacing between stirrups in beam will varies at the ends and at central part. Generally the vertical stirrups are closely spaced at the ends when compared to the middle part it is done so as to overcome the shear cracks in the beam which could result in failure.
The term stirrups is used to define the transverse reinforcement provided in beam where the primary mode of load transfer is through bending and shear. Here the requirement of transverse reinforcement is to prevent shear cracks in the beam which could result in failure. Thus they provide additional shear strength to the concrete and are designed accordingly.
As the shear strength requirement is more at the supports than the center, the spacing of stirrups decreases towards the end of the beam.
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Minimum and maximum spacing between stirrups in beam and column
As per IS 456 code provision, the spacing of stirrups in reinforced beam and column should be least lateral dimensions of beam and column or 16× diameter of smallest longitudinal bar or 300mm.
Suppose dimensions of beam is 250 × 300mm, their least lateral dimension is 250mm or 10″, so you should take spacing between stirrups at 250mm or 10″ apart. So you should use T8@10″C/C for stirrup.
The standard spacing of stirrups in a rectangular beam is 6 to 8 inches toward the center of the beam and 4 to 6 inches toward the supports end of the beam. Spacing of vertical stirrups in RCC beam is kept maximum at mid span of RCC beam and minimum near support ends.
The minimum spacing of vertical stirrups in a rectangular beam should not be less than 4 inches or 100 mm. In general 4 to 5 inches of stirrups spacing provided at middle and 6 to 7 inches at supports ends of an RCC beam.
Formula for spacing of stirrups in a rectangular beam is: spacing between stirrups = Least lateral dimension of beam or 16× diameter of smallest longitudinal bar or 300mm.
Spacing between stirrups in beam:- as per general rules and guideline, maximum spacing between stirrups in beam should not be exceed to 300mm or 12″ and minimum should be not less than 100mm or 4″. On general standard spacing of 6″ to 7″ (150 – 180mm) between stirrups provided at middle and 4″ to 5″ (100 – 125mm) at end support of beam.
Spacing between stirrups in column:- as per general rules and guideline, maximum spacing between stirrups in column should not be exceed to 300mm or 12″ and minimum should be not less than 100mm or 4″. On general standard spacing of 6″ to 7″ (150 – 180mm) between stirrups provided at middle and 4″ to 5″ (100 – 125mm) at end support of column.
Spacing of stirrups near the support end is minimum due the maximum shear forces of the supports. Generally minimum spacing of 6″ to 7″ (150 – 180mm) provided to the support end between stirrups for the rectangular beam and column.
Spacing of stirrups in rectangular beam is maximum at the mid – span and minimum at the support end. This is because the shear forces gradually decreases towards the mid – span and become zero at the centre and higher at the end supports. Thus, maximum spacing of 300 mm provided between stirrups at the mid span of beam and column and minimum of 100 – 150 mm at the end supports.
As per code provision the stirrups spacing should be least among the : 1) Least lateral dimension of the column, 2) 16 times the diameter of longitudinal main bar and 3) Not more than 300 mm c/c.
◆ Spacing of stirrups as per IS 456
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Conclusion:-
As per IS 456 code provision, maximum spacing between stirrups should not be more than 300mm or 12″ and it is minimum of 100mm or 4″ provided in beam & column