Introduction to Cyclic Loading Analysis of Steel Beam-Column Joints with Welded Steel Angles

In structural engineering, beam-column joints play a critical role in transferring forces and ensuring stability within steel frame structures. When subjected to cyclic loading, such as those experienced during earthquakes or wind loads, these joints must withstand repeated stress reversals without significant degradation in strength or stiffness.

One common detailing method for these joints involves the use of welded steel angles, which are used as connectors between the beam and the column. These angles can be configured in various ways (e.g., top-and-seat angles, double angles at the beam web), and their design and behavior under cyclic loads are crucial for the joint’s overall seismic performance.

 Cyclic Loading and Its Importance

Cyclic loading refers to the application of repeated or reversing loads over time. In seismic design, structures must absorb and dissipate energy through inelastic deformation without collapsing. Therefore, understanding how a welded angle connection performs under such conditions is vital for:

• Ensuring ductility (ability to deform without breaking)
• Maintaining stiffness and strength
• Preventing brittle failure
• Improving energy dissipation capacity

 Steel Beam-Column Joint with Welded Angle – Key Components

1. Beam: Transfers loads to the column.
2. Column: Vertical load-carrying element.
3. Welded Steel Angle: Serves as a connection element between the beam and column.
4. Welds: Transfer forces from the beam and angle into the column.

Angles may be used as:

• Top-and-seat angles: Placed at the top and bottom flanges of the beam.
• Web angles: Connecting the beam web to the column.

🧪 Cyclic Loading Analysis – What It Involves

Cyclic analysis of such joints typically includes:

1. Experimental Testing

• Quasi-static tests with controlled displacements
• Observations of:
  • Yielding of the angle legs
  • Weld fracture
  • Local buckling
  • Slip or prying effects

2. Finite Element Analysis (FEA)

• Nonlinear simulations including material plasticity and contact/slip behavior
• Evaluation of:
  • Hysteresis curves (force-displacement loops)
  • Degradation of stiffness and strength
  • Plastic hinge formation