Stools in Reinforcement Detailing: Also known as mall chair. The purpose of the stools is to maintain the reinforcement in the right place and to separate the upper reinforcement and the lower reinforcement or to provide adequate space in the net.
Stool levels vary as needed.
Stools in Reinforcement Detailing
When installing main mesh reinforcement throughout the construction, it is important to keep the steel chairs evenly spaced and to maintain mesh reinforcement before and after concreting.
The stool has good strength to withstand loads without changing the gap between the two levels. 12mm or 16mm bars are used to make stools.
Depending on the construction, different types of stools are available, such as wire chairs, plastic chairs, or small concrete cubes or cylinders. Some even small dog bone sizes. It is also seen in RAF reinforcement in foundations and footings.
Depending on the development, distinctive sorts of stools are to be had, such as cord chairs, plastic chairs, or small concrete cubes or cylinders. Some even small dog bone sizes. It is also visible in RAF reinforcement in foundations and footings.
The thickness of the stool relies upon on the size of the footing and the slab. The spacing of stools for a mall is usually 1 square meter. The diameter of the stool is identical to the diameter of the principle reinforcement.
The stools are determined in the lower a part of the mainly curved rod within the slab to preserve the perfect hole among the top reinforcement and the decrease reinforcement.
Mal peak = slab thickness - (2 x cowl + diameter of higher and lower bars).
Stool is used to separate the upper reinforcement mesh and the decrease reinforcement mesh. Stool degrees can also change as needed. There should be enough strength to withstand the load with out converting the distance among the two layers. 12mm or 16mm bars are used to make stools.
RCC STRUCTURES DESIGN Multiple Choice Questions :-
1. An R.C.C. beam of 6 m span is 30 cm wide and has a lever arm of 55 cm. If it carries a U.D.L. of 12 t per m and allowable shear stress is 5 kg/cm2, the beam
A. Is safe in shear
B. Is safe with stirrups
C. Is safe with stirrups and inclined bars
D. Needs revision of section
ANS: D
2. According to I.S. : 456, slabs which span in two directions with corners held down, are assumed to be divided in each direction into middle strips and edge strips such that the width of the middle strip, is
A. Half of the width of the slab
B. Two -third of the width of the slab
C. Three-fourth of the width of the slab
D. Four-fifth of the width of the slab
ANS: C
3. The load stress of a section can be reduced by
A. Decreasing the lever arm
B. Increasing the total perimeter of bars
C. Replacing larger bars by greater number of small bars
D. Replacing smaller bars by greater number of greater bars
ANS: C
4. the column head support a flat slab, is generally kept The diameter of
A. 0.25 times the span length
B. 0.25 times the diameter of the column
C. 4.0 cm larger than the diameter of the column
D. 5.0 cm larger than the diameter of the column
ANS: A
5. fixed at its ends, the If is the uniformly distributed load on a circular slab of radius maximum positive radial moment at its centre, is
A. 3WR²/16 B. 2WR²/16 C. WR²/16
D. None of these ANS:
C 6. The maximum ratio of span to depth of a slab simply supported and spanning in one direction, is
A. 35
B. 25
C. 30
D. 20
ANS: C
7. If the width of the foundation for two equal columns is restricted, the shape of the footing generally adopted, is
A. Square
B. Rectangular
C. Trapezoidal
D. Triangular
ANS: B
8. The floor slab of a building is supported on reinforced cement floor beams. The ratio of the end and intermediate spans is kept
A. 0.7
B. 0.8
C. 0.9
D. 0.6
ANS: C
9. Pick up the correct statement from the following:
A. Lateral reinforcement in R.C.C. columns is provided to prevent the longitudinal reinforcement from buckling
B. Lateral reinforcement prevents the shearing of concrete on diagonal plane
C. Lateral reinforcement stops breaking away of concrete cover, due to buckling
D. All the above
ANS: D
10. In case the factor of safety against sliding is less than 1.5, a portion of slab is constructed downwards at the end of the heel slab, which is known as
A. A key
B. A cut-off wall
C. A rib
D. All the above
ANS: D RCC Structures Design Multiple Choice Questions
11. Lapped splices in tensile reinforcement are generally not used for bars of size larger than A. 18 mm diameter
B. 24 mm diameter
C. 30 mm diameter
D. 36 mm diameter
ANS: D
12. Minimum spacing between horizontal parallel reinforcement of the same size should not be less than
A. One diameter
B. 2.5 diameters
C. 3 diameters
D. 3.5 diameters
ANS: A
13. For a ribbed slab
A. Clear spacing between ribs shall not be greater than 4.5 cm
B. Width of the rib shall not be less than 7.5 cm
C. Overall depth of the slab shall not exceed four times the breadth of the rib
D. All the above
ANS: D
14. A very comfortable type of stairs is
A. Straight
B. Dog legged
C. Geometrical
D. Open newel
ANS: D
15. Columns may be made of plain concrete if their unsupported lengths do not exceed their least lateral dimension
A. Two times
B. Three times
C. Four times
D. Five times
ANS: C Q-NO:
16 The width of the flange of a L-beam, should be less than
A. One- sixth of the effective span
B. Breadth of the rib + four times thickness of the slab
C. Breadth of the rib + half clear distance between ribs
D. Least of the above
ANS: D
Q-NO: 17 A pre-stressed concrete member is preferred because
A. Its dimensions are not decided from the diagonal tensile stress
B. Large size of long beams carrying large shear force need not be adopted
C. Removal of cracks in the members due to shrinkage
D. All the above
ANS: D
Q-NO: 18 If the ratio of the span to the overall depth does not exceed 10, the stiffness of the beam will ordinarily be satisfactory in case of a
A. Simply supported beam
B. Continuous beam
C. Cantilever beam
D. None of these
ANS: C
Q-NO: 19 carrying a uniformly distributed load per metre length is suspended at two A pile of length points, the maximum, B.M. at the centre of the pile or at the points of suspension, is
A. WL/8
B. WL²/24
C. WL²/47
D. WL²/16
ANS: C
Q-NO: 20 If is the net upward pressure on a square footing of side for a square column of side , the maximum bending moment is given by
A. B.M = pb (c – a)/4
B. B.M = pb (b – a)²/4
C. B.M = pb (b – a)²/8
D. B.M = pb (b + a)/8
ANS: C
Q-NO: 21 To ensure uniform pressure distribution, the thickness of the foundation, is
A. Kept uniform throughout
B. Increased gradually towards the edge
C. Decreased gradually towards the edge
D. Kept zero at the edge
ANS: C
Q-NO: 22 longitudinal bars and lateral stirrups, is
A. Stress in concrete × area of concrete
B. Stress in steel × area of steel
C. Stress in concrete × area of concrete + Stress in steel × area of steel
D. None of these
ANS: C
