Introduction
Fillet welds in built-up welded structural profiles, such as tees, play a critical role in transferring shear forces and ensuring structural integrity. In this blog post, we’ll focus specifically on shear flow design for the weld between the flange and the web (or stem) of a steel tee, following AISC 360. We’ll cover how shear is transferred, how to calculate weld demands, and how to verify weld capacities.
Understanding Shear Flow in Tee Welds
When a built-up tee section is subjected to shear, the flange and web must transfer forces through their connecting welds. These forces arise due to shear stresses in the member, requiring a properly designed fillet weld to resist the induced shear flow along the connection.
Shear flow in the weld depends on:
The applied shear force
The geometry of the tee section
The weld length and size
Proper weld design ensures that the connection can safely transfer shear without exceeding allowable stress limits.
Demand Calculations
The shear flow demand in a built-up tee section can be expressed as:
Where:
V = Shear force
Q = First moment of area about the neutral axis
I = Moment of inertia of the section
This equation helps determine the force per unit length that must be resisted by the weld.
Weld Capacity
The strength of the fillet weld is governed by its throat thickness and electrode strength. The nominal shear strength of a throat weld is given by:
Where:
Φ_w = Weld Resistance Factor
F_nw = Nominal Stress of Weld (based on electrode used)
A_we = Effective Weld Area
Example Problem
(Solutions Provided Using CalcBook) Problem Statement:
Demand Calculation:
Geometric Properties:
Weld Stress:
Capacity of 3/16" Welds
Controlling DCR
Conclusion
Welded tee connections are essential for structural stability, and their welds must be properly designed to transfer shear forces safely. By following AISC 360 guidelines, engineers can ensure robust and efficient designs. With tools like CalcBook, these calculations become faster, more streamlined, and transparent.
Stay tuned for more insights and examples in structural engineering design with CalcBook!
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