RCC Flashcards
Bottom bars under the columns are extended into the interior of the footing slab to a distance greater than
[A]. 42 diameters from the centre of the column
[B]. 42 diameters from the inner edge of the column
[C]. 42 diameters from the outer edge of the column @
[D]. 24 diameter from the centre of the column
If we erect the steel for a column and footing, let’s take 6 bars for the column. So we need to bend (90 °) these bars near the bottom and insert them into the footing. BUT BARS INSIDE THE FOOTING SHOULD BE MORE THAN 42 Times the diameter of the bar.
Let’s consider our bar is 16mm, so we need to insert 42 *16= 672 mm into the footing, obviously, its counted from the bend or you can say the outer edge of the column.
And we have to do it with all 6 bars which we consider here.
Dimensions of a beam need be changed if the shear stress is more than
[A]. 10 kg/cm2
[B]. 15 kg/cm2
[C]. 20 kg/cm2 @
[D]. 25 kg/cm2
Max shear stress of concrete= 0.63 under root fck.
So, for M15 concert it should be;
0.63 x under root 15 = 2.5 N/mm^2.
As per IS 456-1978 section is redesigned if shear stress is greater than 20 kg/cm2 or 2N/mm2.
So, the Given answer is correct.
For a circular slab carrying a uniformly distributed load, the ratio of the maximum negative to maximum positive radial moment, is
[A]. 1 [B]. 2 @ [C]. 3 [D]. 4 [E]. 5
For a circular slab carrying a uniformly distributed load, Max negative radial moment 2wr^2/16, the negative bending moment will occur at support. Max positive radial moment wr^2/16, the max positive bending moment will occur at centre. So the answer will be 2.
The minimum cube strength of concrete used for a prestressed member, is
[A]. 50 kg/cm2 [B]. 150 kg/cm2 [C]. 250 kg/cm2 [D]. 350 kg/cm2 @ [E]. 400 kg/cm2
M35 for Post-tensioned concrete.
M40 for Pre-tensioned concrete.
The number of treads in a flight is equal to
[A]. risers in the flight
[B]. risers plus one
[C]. risers minus one @
[D]. none of these.
Rise = 1 + Trade.
For initial estimate for a beam design, the width is assumed
[A]. 1/15th of span [B]. 1/20th of span [C]. 1/25th of span [D]. 1/30th of span @ [E]. 1/40th of span.
Depth is l/20.
And width is l/30.
If T and R are tread and rise respectively of a stair, then
[A]. 2R + T = 60 @ [B]. R + 2T = 60 [C]. 2R + T = 30 [D]. R + 2T= 30 [E]. 3R + 27 = 30
Rise -150mm & trade -300mm.
R=15cm & T=30cm.
Then 2R+T=60.
2*15+30=60.
The effective width of a column strip of a flat slab, is
[A]. one-fourth the width of the panel [B]. half the width of the panel @ [C]. radius of the column [D]. diameter of the column [E]. none of these.
In IS456 - 2000 Clause 31.1.1 - a
Column strip - Column strip means a design strip having a width of 0.2S ‘2, but not greater than 0.25’ on each side of the column centreline, where I. is the span in the direction moments are being determined, measured centre to centre of supports and ‘2 is the span transverse
Cantilever retaining walls can safely be used for a height not more than
[A]. 3 m [B]. 4 m [C]. 5 m [D]. 6 m @ [E]. 8 m
Cantilever retaining wall economical for heights 6 - 7.5 m small to moderate height. So according to question 8 m correct.
If W is the load on a circular slab of radius R, the maximum circumferential moment at the centre of the slab, is
[A]. [B]. [C]. 3W.R^2 /16 @ [D]. zero [E]. none of these.
[C]. 3W.R^2 /16 @
radial moment also
=3W.R^2 /16
In a combined footing if shear stress exceeds 5 kg/cm2, the nominal stirrups provided are:
[A]. 6 legged [B]. 8 legged [C]. 10 legged [D]. 12 legged @ [E]. none of these.
Footing essentially acting as a wide beam. Normally, in combined footing, we do not provide shear reinforcement. If nominal shear strength exceeds permissible shear strength, then its depth is increased so that nominal shear strength is less than permissible shear strength. However, Shear reinf Is provided when nominal exceeds permissible shear strength. It depends on dia, stress & spacing of stirrups. It is not fair to say 8 or 12 legged.
For stairs spanning horizontally, the minimum waist provided is
[A]. 4 cm [B]. 6 cm [C]. 8 cm [D]. 10 cm [E]. 12 cm. @
Yes it should be 8 cm.
Ref: R.S. Khurmi/ conventional and objective type civil engineering book.
If the maximum shear stress at the end of a simply supported R.C.C. beam of 6 m effective span is 10 kg/cm2, the share stirrups are provided for a distance x from either end where x is
[A]. 50 cm
[B]. 100 cm
[C]. 150 cm @
[D]. 200 cm
L/4 indiabix
The radius of a bar bend to form a hook, should not be less than
[A]. twice the diameter @ [B]. thrice the diameter [C]. four times the diameter [D]. five times the diameter [E]. none of these.
The radius of a bar bend to form a hook, should not be less than
[A]. twice the diameter @ [B]. thrice the diameter [C]. four times the diameter [D]. five times the diameter [E]. none of these.
The toe projection of foundation slabs is taken
[A]. as one third of the base @
[B]. as one sixth of overall height of the wall
[C]. equal to heel slab
[D]. below ground surface.
Toe projection of foundation slab=25% to 30% of the height of stem or 1/3.
And heel projection =70% to75% or.7H.
On piles, the drop must be at least
[A]. 80 cm [B]. 100 cm [C]. 120 cm @ [D]. 140 cm [E]. 150 cm
The piles are pushed to the ground to carry the surface loads or heavy structures above it.
Now the drop means the transfer of piles to the exact location when we can release the piles at 120 cm.
In testing a pile by load test, pile platform is loaded with one and half times the design load and a maximum settlement is noted. The load is gradually removed and the consequent rebound is measured. For a safe pile, the net settlement (i.e. total settlement minus rebound) per tonne of test load should not exceed
[A]. 10 mm [B]. 15 mm [C]. 20 mm [D]. 25 mm @ [E]. 30 mm
For sand max allowable deflection is 25mm.
If the shear stress in a R.C.C. beam is
[A]. equal or less than 5 kg/cm2, no shear reinforcement is provided
[B]. greater than 4 kg/cm2, but less than 20 kg/cm2, shear reinforcement is provided
[C]. greater than 20 kg/cm2, the size of the section is changed
[D]. all the above. @
If the shear stress in a R.C.C. beam is
[A]. equal or less than 5 kg/cm2, no shear reinforcement is provided
[B]. greater than 4 kg/cm2, but less than 20 kg/cm2, shear reinforcement is provided
[C]. greater than 20 kg/cm2, the size of the section is changed
[D]. all the above. @
