Some vital points a site civil engineer should abide by

Least density of the slab should be 125 mm.
Absorption of water should not be over 15%

Lapping is unaccepted for the bars which contain diameter over 36 mm.

Longitudinal reinforcement should be not under 0.8% and in excess of 6% of gross C/S.
At least 4 numbers of bars should be used for square column and 6 numbers of bars for circular column.
Minimum density of the slab should be 125 mm.
Lap slices are not recommended for the bar greater than 36 mm.
Water absorption of bricks should not surpass 15%.
PH value of the water should not be under 6.
Dimension tolerance for cubes should be +2 mm.

Densities of different types of construction materials :-

Steel = 7850 kg/Cum
Cement = 1440 kg/Cum
Brick = 1682 kg/Cum or 1920 kg/cum
Sand = 1100 to 1600 kg/cum

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Published By
Rajib Dey
www.constructioncost.co

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Design specifications for footings following IS 456: 2000

As per standard IS 456: 2000, the following guidelines are given for the design of isolated footings :-

The objective of Footings is to retain the applied loads, moments and forces and the driven reactions and make sure that any prospective settlement is as almost undeviating as possible, and the safe bearing capacity of the soil is not surpassed.

In sloped or stepped footings the operative cross-section in compression is restricted with the area over the neutral plane as well as the angle of slope or depth and location of steps is arranged in such a way that the necessities for design are fulfilled at each section. Sloped and stepped footings which are designed as a unit should be built up to guarantee action as a unit.

Thickness at the Edge of Footing

1. In reinforced and plain concrete footings, the thickness at the edge should be over 150 mm for footings on soils, nor below 300 mm over the tops of piles for footings on piles.

2. For plain concrete pedestals, the angle among the plane moving toward the bottom edge of the pedestal and the equivalent junction edge of the column with pedestal and the horizontal plane should be managed by the expression:
2) where
= computed optimal bearing pressure at the base of the pedestal in N/mm2
fck = characteristic strength of concrete at 28 days in N/mm2.

Moments and Forces

1. Toward the footings on piles, calculation for moments and shears are dependent on the proposition that the reaction from any pile is set at the centre of the pile.

2. In order to calculate stresses in footings which support a round or octagonal concrete column or pedestal, the face of the column or pedestal is assumed as the side of a square imprinted within the perimeter of the round or octagonal column or pedestal.

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Published By

Rajib Dey

www.constructioncost.co

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Concrete Footings – Some useful guidelines

Usually, it should be examined when the footings are arranged for concreting i.e. reinforcement is completely engrossed but it is recommended to examine it in two phase i.e.

01. Initially verify formwork prior to arrange reinforcement. This is very useful because finding out & rectifying formwork defect is very difficult once the reinforcement is organized in position.

02. Checking reinforcement – Therefore, it is suggested to initially verify the formwork prior to place or tie reinforcement.

01. Centering and shuttering / Formwork:

While starting the shuttering & centering / formwork for footing , abide by the following points.

• Verify the center lines / margin from boundary etc. from reference column/bench mark pillar, boundary distance from roads and obviously orientation regarding North.

• Make sure that the foundation is laid at a designed depth according to drawing.

• Size of formwork box should be according to drawing and it should be formed with correct materials.

• The formwork should have been dry and be refined cautiously prior to use mould release agent. The similar type of release agent should have been applied through on identical formwork materials.

• The surface of formwork should have been uniform and delicately coated with mould release agent.

• The mould release agent should not be contacted with reinforcement or the solidified concrete.

• The height of shuttering must be similar with the height of pedestal and joint should have been closed to avoid any leakage of cement pulp.

• Footing box should have been supported correctly in order that the placing of footing box should be unchanged throughout concreting.

• Centre of the footing is stamped with the nail on planks or footing box.

• Foundations shuttering should be strong in dry or even rainy situations or even when ground water exist.

• Prior to tying reinforcement, get the shuttering sanctioned by Engineer-in-charge or supervisor.

• Ensure that there is no earth collection on C.C. prior to tying reinforcement.

• If foundation depth increases, make sure that the excavated earth does not slide or drop unless it is refilled. Accomplish perfect shoring and shuttering. Make sure that suitable ladder etc to enter the pit and for coming out. Besides, examine the safety of labor’s working.

To read the complete article, go through the following link gharpedia.com

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Published By

Rajib Dey

www.constructioncost.co

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