When Building Codes Require Calculations
Most building codes do not explicitly require connection design calculations for standard gravity connections where the EOR has designed and shown the connections on the structural drawings. Calculations are required when: connection design is delegated to the fabricator and the connection must be verified against code; the connection type is seismic-rated and requires compliance documentation; the connection is a custom or non-prequalified type that requires justification; or the AHJ (authority having jurisdiction) specifically requests calculations as a condition of permit.
When the Contract Requires Calculations
Even when codes don't require them, many project specifications require delegated connection design calculations to be submitted with shop drawings. Division 05 of the project spec will typically state something like 'connection design calculations, signed and sealed by the fabricator's engineer, shall be submitted for all delegated connections with the shop drawing submittal.' If this language is in the spec, calculations are contractually required regardless of code.
Format and Submission Requirements
Connection calculations submitted for EOR review should: identify each connection by drawing reference, piece mark, and gridline; show the governing load combination; reference the applicable standard (AISC 360 Chapter J for simple connections, AISC 358 for seismic prequalified); show the capacity calculation; and conclude with a compliance statement. They must be signed and sealed by the PE accepting design responsibility. The EOR reviews for load compliance and specification conformance — not for correctness of the PE's engineering, which is the PE's responsibility.
Seismic Projects and AISC 341 Requirements
Projects in Seismic Design Categories C through F, as defined by ASCE 7 and the IBC, impose connection calculation requirements beyond those of non-seismic design. AISC 341 (Seismic Provisions for Structural Steel Buildings) and AISC 358 (Prequalified Connections for Special and Intermediate Steel Moment Frames) together establish that seismic moment frame connections must use pre-qualified connection types with documented compliance calculations, or must be tested and qualified by alternative means. The calculations must demonstrate that the connection meets the rotation capacity, strength, and detailing requirements of the prequalified connection type. Non-seismic calculation methods — verifying bolt shear and weld capacity alone — are insufficient for AISC 341 scope; the calculations must address expected yield stress, probable maximum moment, and panel zone demands.
Special Inspection and Calculation Documentation
On projects requiring special inspection under IBC Chapter 17, the special inspector verifies structural work against approved documents — including the connection design calculations. The special inspector for structural steel (typically a CWI or AWS Certified Inspector per IBC Table 1705.2) needs access to the approved calculations to verify that the weld sizes, bolt grades, and plate thicknesses they are inspecting match what was calculated and approved. Calculations that exist but were never submitted to the EOR for approval, or that were submitted but never formally approved, leave the special inspector without a verified reference document — a finding that can result in work being stopped.
When EOR-Designed Connections Eliminate the Need
When the EOR fully designs every connection and shows the design — plate sizes, bolt patterns, weld sizes, and stiffener requirements — on their structural drawings, separate delegated connection calculations are not required. The EOR's stamped structural drawings are the engineering document of record for those connections. The detailer's role is to produce shop drawings that faithfully implement what the EOR designed; the calculation basis is the EOR's responsibility. This model eliminates the delegated calculation submittal requirement but requires significantly more engineering work from the EOR and more detailed structural drawings as input to the detailer.
Keeping Calculations Current Through Revisions
Connection calculations are not a once-issued document. When design revisions change member sizes, connection loads, or connection geometry — through addenda, EOR design changes, or scope additions — the calculations must be updated and resubmitted. An approved calculation set that references a W24x62 beam at a connection that has since been revised to a W24x76 is no longer valid; the higher beam capacity changes the connection demand and potentially the connection design. Fabricators should confirm with their connection engineer whether each revision that affects a connection requires a calculation update, and include calculation re-issuance as a line item in revision-related change order estimates.