Direct Shear And Punching Test

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4. To perform direct shear and punching shear test on steel specimen. (29-10-08) Apparatus 10 Ton Buckton UTM, Shear Jigs, Vernier Caliper, Steel Specimens (plain steel bar for direct shear test and steel plate for punching shear test.)

Related Theory Shear Force (V): A force which is applied parallel to the sections is known ad Shear force.

Shear Strain (𝝋𝛗 ): The distortion produced by Shear Stress on an element or Rectangular Block is shown in the diagram. The Shear Strain or "Slide" is 𝜑 and can be defined as the change in the right angle. It is measured in Radians and is dimensionless.

Shear Stress The intensity of internal resistance when the applied force is parallel to the section being sheared is called shear stress OR, If the applied load consists of two equal and opposite parallel Forces which do not share the same line of action, then there will be a tendency for one part of the body to slide over or shear from the other part. If the section L M is 𝐹

parallel to the forces and has an area A then the average Shear Stress. (𝑃 = 𝐴)

1

Direct shear and Punching shear test on steel specimen

07 Civil 73

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Types of Shear Stress 1.   2.

Direct Shear Stress Single Shear Stress Double Shear Stress Punching Shear Stress

Direct Shear Stress

Punching Shear Stress

Procedure 1. 2. 3. 4. 5. 6.

Measure the diameter of steel bar and find its cross sectional area. Fix the lower jig and upper jig in the machine. Fix the zero error of the machine. Place the steel sample over the lower jig. Apply the shear load until the bar gets sheared. Apply the load gradually and note the reading when the bar gets sheared. Calculate the shear strength by using the relationship. (𝜏 =

𝑃 𝜋𝑑2 4

)

Precautions    

Don’t perform stress test on the edges of the specimen. Must align, upper and lower jigs. Apply the load gradually. Zero error of the machine should be removed.

2

Direct shear and Punching shear test on steel specimen

07 Civil 73

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Calculations and Observations Direct Shear Stress Sample Test Type Used Direct Shear Stress

Shear Load Tons

Observed Diameter d1 (mm)

N

1.06 10398.6

6.75

d2 (mm)

d3 (mm)

6.95

6.867

Average Shearing Diameter Area mm mm2

6.856

Shear Stress (t=V/A) Mpa

37

PSI

281 40763

*1 MPa = 145.04 PSI, 𝒕 =

𝑽 𝑨

Punching Shear Stress Test Type

Sample Used

Punnching Shear Stress

Shear Load Tons

N

1.32 12949

Diameters of Jigs do mm di mm 12.2

15.55

Average Thickness Shearing Diameter of Plate (t) Area mm 13.8875

mm

mm2

1.55

67.67

Shear Stress (t=V/A) Mpa

191.4 27754

Comments The phenomenon of punching shear stress enables us to design bridge becks and other its kinds of structures. Passing vehicles acts as a punch on the bridge deck. So it should be kept in mind while designing a bridge. Moreover a direct shear stress value of a material gives us a clue to predict the strength of a material against shearing.

3

Direct shear and Punching shear test on steel specimen

07 Civil 73

PSI