Column splices (different depths): When the depth of the upper column section is smaller than that of the lower column, what should be provided at the splice to ensure proper load transfer and alignment?

Introduction / Context:
Steel column splices must provide continuity for axial load, moments (if any), and alignment. When mating sections have different depths, detailing must address geometry and bearing to avoid local overstress and eccentricities.

Given Data / Assumptions:

• Upper column is shallower than lower column.
• Splice is designed primarily for axial load transfer with alignment control.
• Fabrication tolerances require packings where necessary.

Concept / Approach:

Filler plates compensate for the difference in depth so that splice plates and flanges align correctly. Bearing plates (or bearing stiffeners) ensure uniform load transfer across the joint. Using both is standard practice when section depths differ, preventing stress concentrations and secondary bending at the splice.

Step-by-Step Solution:

Verification / Alternative check:

Steel design handbooks illustrate splice details with filler and bearing elements where section sizes change. Shop drawings typically call out plate thicknesses to equalise depths and ensure contact surfaces.

Why Other Options Are Wrong:

• Filler plates only: alignment improved, but bearing may be inadequate.
• Bearing plates only: load may transfer, but geometric mismatch remains for splice plates.
• Shim washers: not appropriate as the primary solution for depth differences.

Common Pitfalls:

• Forgetting to extend filler plates to the full contact area.
• Not machining bearing surfaces where required for high loads.

Final Answer:

Both filler plates and bearing plates.