Question

In eccentric loading of welds, the stress which vary from point to point as proportional to its distance from the centre of gravity, is known as:

• A. Primary Shear Stress
• B. Secondary Shear Stress
• C. Tertiary Shear Stress
• D. Distributed Load

Hint:

Remember that eccentric loads on welded joints cause both uniform direct shear stress and torsional shear stress that varies linearly with the distance from the centroid of the weld group.

Answer 1

The Correct Option is B

Step 1: Understand eccentric loading of welds.
Eccentric loading occurs when the applied load does not pass through the centroid of the weld group. This eccentric load creates both a direct shear stress and a torsional shear stress in the welds. Step 2: Define Primary Shear Stress.
Primary shear stress (\( \tau_p \)) is the shear stress induced in the welds due to the direct shear force component of the eccentric load. It is assumed to be uniformly distributed over the effective weld area and acts in the direction of the applied shear force. The magnitude is given by \( \tau_p = \frac{P}{A} \), where \( P \) is the shear force component and \( A \) is the total effective area of the weld group. Step 3: Define Secondary Shear Stress.
Secondary shear stress (\( \tau_s \)) is the shear stress induced in the welds due to the torsional moment created by the eccentric load about the centroid of the weld group. This stress is not uniformly distributed but varies linearly with the distance from the centroid of the weld group. The magnitude of the secondary shear stress at any point in the weld is proportional to the distance \( r \) from the centroid and is given by \( \tau_s = \frac{Mr}{J} \), where \( M \) is the torsional moment, \( r \) is the distance from the centroid to the point of consideration, and \( J \) is the polar moment of inertia of the weld group about its centroid. Step 4: Define Tertiary Shear Stress.
Tertiary shear stress is not a standard classification of stress in eccentrically loaded welds in basic structural analysis. The primary stresses considered are direct shear (primary) and torsional shear (secondary). Step 5: Define Distributed Load.
Distributed load refers to a load that is spread over an area or length, unlike a point load. While the applied force in eccentric loading might be considered over a small area of the weld, the resulting stresses within the weld are categorized based on their nature (direct shear vs. torsional shear). Step 6: Identify the stress proportional to the distance from the centre of gravity.
As explained in Step 3, the secondary shear stress (\( \tau_s = \frac{Mr}{J} \)) is directly proportional to the distance \( r \) from the centroid (centre of gravity) of the weld group. Step 7: Select the correct answer.
The stress which varies from point to point as proportional to its distance from the centre of gravity in eccentric loading of welds is known as secondary shear stress. This corresponds to option 2.