What is the formula for punching shear?
What is the formula for punching shear?
For an interior punching shear perimeter this will always be L1/2 or L2/2. For edge and corner cases this value is calculated as the moment of area of the shear perimeter/area of the sides.
How do you calculate punching shear in footing?
Punching shear is produced directly by the forces and moments acting on the column. For the simple case of a concentric footing with a downward load, the punching shear can easily be calculated as the volume of the bearing pressures on the critical area around the column.
What is punching shear failure?
Punching shear is a type of failure of reinforced concrete slabs subjected to high localized forces. In flat slab structures, this occurs at column support points. The failure is due to shear. This type of failure is critical because no visible signs are shown prior to failure.
What is punching shear in pile cap?
As we all know, Punching Shear is a concentrated load causing shear stress on the section around the load and this load should be resisted by the structural member from where the concentrated load or the reaction is rested. …
What causes punching shear?
Punching shear arises when a concentrated load is applied to a small area of a slab or, most commonly, the reaction of a column against a slab. The resulting stresses are verified along defined control perimeters around the loaded area.
How do you stop a punching shear failure?
To overcome the punching failure problem, there are many ways to increase the punching shear strength of concrete slabs, increasing slab thickness in the area adjacent to the column, increasing column thickness which is against the architectural desire, and finally providing slab with shear reinforcement.
How do you calculate footing load?
per square foot. Total load = (½ building width x Post spacing) x (5 lbs. dead load1 + snow load2) = 20′ x 8′ x (5 + 20 lbs. / square foot) = 160 square feet x 25 lbs. / square foot = 4000 lbs.
How do you calculate footing size?
How to Calculate Footing Size
- Determine the width and length of the cement slab in inches.
- Divide the width by 12 to convert it to feet.
- Divide the length by 12 to convert it to feet.
- Determine the depth or thickness that is required for the footing in inches.
- Multiply the width by the length and then by the depth.
What causes punching shear failure?
General Mechanism of Failure Punching shear is a phenomenon in flat slabs caused by concentrated support reactions inducing a cone shaped perforation starting from the top surface of the slab.
How do you calculate pile cap size?
Consider the design of a pile cap supporting two pile and a single column on the pile cap. consider 150mm offset from the pile and space between piles as 2.5 times pile diameter. Effective depth, d = 1000-50-20/2 = 940 mm > 750mm; (2.5×600/2) Ok.
Why pile cap is provided?
Pile caps create a stable foundation and offer a larger area for the distribution of the building load onto the piles. They act in a similar way to piled raft foundations, where a concrete slab rests on soil which may be susceptible to movement, above a group of piles. Rectangular (for all other number of piles).
What is the critical section for punching shear?
… critical section for the punching shear appears at a distance “d/2” to from the junction of the column with the footing in the two directions occurs in the rectangular section formed by the points 5, 6, 7 and 8, as shown in Fig. …
How to calculate the perimeter of punching shear?
Consider the design of footing for punching shear as per the BS 8110. According to the BS 8110 Part 1, shear perimeter shall be at 1.5d. Hence Ok. Length of share perimeter = 4x (1.5d+300+1.5d) = 4x (1.5×350 + 300 + 1.5×350) = 5400mm
When is punching shear used as a failure mechanism?
Punching shear is a failure mechanism when structural elements subjected to concentrated load. Failure occurs in perimeter defined away from the concentrated load. Slabs, pile caps, footings, raft foundations, etc. element is subjected to punching action and they need to be designed for it.
What is the critical shear perimeter in BS 5400?
And it covers almost all the different cases that could arise when we design slabs, pile caps, flat slabs, footings, raft foundations. Distance to the critical shear perimeter is considered as 1.5d in BS 5400 Part 4. BS 8110 is also considered the same shear perimeter.
How is depth of section adequate for shear?
Therefore, depth of section is adequate for shear. Extent of shear links Sn = (V d – Vn)/q + d Extent of shear links Sn = (1266.64 – 706.326)/ (514.77 + 1.024) = 2.112 m Therefore, stop main shear links (4Y10mm @ 150mm) i.e. at 2.2 m from face of column and provide nominal reinforcement of 3Y10 @ 300mm till the point of zero shear force.