Applied Seismic Steel-Design Examples

Example 1: Ordinary Strength Check vs. Seismic Capacity Design

A beam-to-column connection in a seismic frame has an elastic-analysis beam-end moment below the ordinary AISC 360 design strength of the connection. A designer concludes that no further seismic check is required.

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Example 2: Special Moment Frame Connection Selection

A designer proposes a custom beam-to-column moment connection for a Special Moment Frame because its elastic finite-element stresses are low.

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Example 3: Protected-Zone Conflict

A mechanical contractor wants to weld a support bracket to a beam flange inside a designated plastic-hinge/protected-zone region of a seismic moment frame.

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Example 4: SCBF Brace and Gusset Philosophy

A special concentrically braced frame has a brace that passes an ordinary compression-strength calculation. The gusset is then sized only for that same compression force.

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Example 5: EBF Link as the Ductile Fuse

An eccentrically braced frame is designed with a short beam link. During value engineering, a stiff plate is proposed across the link region to simplify an equipment attachment.

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Example 6: Strong-Column / Weak-Beam Misuse

A preliminary check compares the nominal plastic moments of one column and one beam and finds the column moment larger. The designer labels the joint 'strong-column/weak-beam compliant.'

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Example 7: Demand-Critical Weld Documentation

A drawing calls for a CJP groove weld at a seismic connection but does not identify any seismic-specific weld or inspection requirements.

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Example 8: Code-Edition Traceability

A class design begins with NSCP 2015 load requirements. A student later inserts a table value copied from AISC 341-22 and a connection detail from AISC 358-22 without noting the change in code basis.

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Key Takeaways
  • Seismic examples must begin by identifying the intended ductile mechanism and the governing code editions.
  • Ordinary AISC 360 strength checks do not replace AISC 341 system/detailing requirements.
  • AISC 358 prequalification is connection-specific and bounded by explicit limitations; it cannot be extrapolated casually.
  • Protected zones and deformation compatibility are as important as nominal connection strength.
  • Capacity-design forces must be traced through every non-yielding component required to develop the intended ductile fuse.