Shear Lag in Tension Members Explained

When a structural member, especially an angle section, is used as a tension member and connected by only a part of its cross-section (like one leg in an angle), the stress distribution across the entire cross-section near the connection is not uniform. This phenomenon is called shear lag. The load tends to transfer directly through the connected portion, causing the unconnected or outstanding portion of the member to experience a delayed and lower stress buildup initially. This non-uniform stress distribution effectively reduces the capacity of the member.

Analyzing the ISA 100 × 65 × 8 Angle Section

The given section is an ISA 100 × 65 × 8, which denotes an Indian Standard Angle. This specification provides the following dimensions:

• One leg has a length of 100 mm.
• The other leg has a length of 65 mm.
• The thickness of the angle is 8 mm.

The problem states that the 100 mm leg is the connected leg using a welded connection. This means the 100 mm side is directly joined to the supporting structure, while the 65 mm side remains outstanding or unconnected.

Determining the Shear Lag Width for Welded Connection

In the context of an angle section acting as a tension member, when only one leg is connected (either by welding or bolting), the shear lag effect primarily impacts the outstanding (unconnected) leg. This outstanding leg lags in carrying its full share of the load because the stress transfer to it occurs through shear deformation from the connected leg, rather than direct axial loading.

Therefore, the term "shear lag width" in such a scenario refers to the width of the leg that is not directly connected to the main load-transferring element, as this is the width over which the shear lag phenomenon is most relevant for calculating the effective area of the section.

Given the angle ISA 100 × 65 × 8:

• The connected leg is 100 mm.
• The unconnected (outstanding) leg is 65 mm.

Thus, the width of the outstanding leg is the relevant dimension for the shear lag width.

Final Shear Lag Width Calculation

Based on the identification of the connected and unconnected legs, the shear lag width for the ISA 100 × 65 × 8 tension member, with the 100 mm leg connected by welding, is the width of the unconnected leg.

The shear lag width is 65 mm.