Shear Flow Weld Design
Fillet welds between elements in welded profiles such as wide flanges, tees, and other structural shapes, play a crucial role in transferring shear forces and maintaining structural integrity. In this blog post, we’ll focus specifically on shear flow design for throat welds in welded profiles per AISC 360, covering how shear is transferred, weld demands are calculated, and capacities are verified.
Understanding Shear Flow in Welds
In welded profiles, shear forces are transferred between elements (e.g., flanges and webs in wide flanges or components in tee sections) primarily through fillet welds along their intersection. These welds must be designed to handle shear flow efficiently without exceeding allowable stress limits.
Shear flow in these welds is influenced by the applied shear force, the geometry of the welds, and the distribution of shear across the weld length.
Demand Calculations
The shear flow demand can be expressed as:
Where:
V = Shear force
Q = First moment of area about the neutral axis
I = Moment of inertia of the section
For welds between elements of welded profiles, the shear demand per unit length is distributed along the length of the weld. This demand is then translated into required weld throat size.
Weld Capacity
The strength of the welds depends on the weld size (throat thickness) and the 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
Welds between elements in welded profiles are essential for maintaining shear continuity and structural stability. By following AISC 360 guidelines and leveraging tools like CalcBook, engineers can perform accurate and efficient weld designs.
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