Required Design Inputs
- Member sizes and orientations — beam depth, flange width, and web thickness affect geometry and weld access
- Design loads at each connection — shear (kips), moment (kip-ft), and axial force (kips) at the factored load combination
- Governing structural standard — AISC 360 for conventional design, AISC 341 for seismic, AISC 358 for seismic prequalified
- Seismic design category (SDC) — determines whether special detailing requirements apply
- Material grades — A992 for wide-flange, A500/A513 for HSS, A36 vs. A572-50 for plates
- Bolt grade and installation method — A325-N, A325-SC, A490-SC; each produces different connection capacity
- Weld type and procedure — SMAW, FCAW, SAW; governed by AWS D1.1 and the project specification
Fabricator Standard Connection Preferences
In addition to engineering requirements, the connection design should incorporate the fabricator's standard preferences: preferred clip-angle sizes, shear plate thicknesses, edge distance conventions, and CNC hole tolerance. Connections designed without these preferences often require re-design when the fabricator reviews them for shop compatibility — particularly for CNC compatibility, where hole edge distances and patterns that work geometrically may not be achievable with the shop's equipment settings.
What Happens When Load Information Is Missing
When connection loads are not provided and connection design is delegated, the PE must either assume loads (which may be conservative and produce heavier connections than necessary) or RFI the EOR for loads (which adds time). The best practice is to negotiate a pre-detailing kickoff that includes the EOR and explicitly confirms the connection load table. A 2-hour kickoff meeting that produces a complete connection load table eliminates weeks of RFI cycle time.
Connection Load Formats — What Is and Is Not Useful
The format in which the EOR provides connection loads has a significant effect on the efficiency of the design process. A tabular connection load summary — showing shear, moment, and axial force at each connection type by member size range — allows the delegated PE to design connection families efficiently. Individual connection loads listed member-by-member on the framing plan are accurate but require more effort to work from. Verbal statements like 'design for full beam capacity' are not load data — they require the PE to calculate the member's capacity before beginning the connection design, adding time and cost.
- Preferred: tabular load summary organized by framing condition (interior beam, end beam, column splice, brace)
- Acceptable: reactions noted at each connection on the framing plan
- Not useful alone: 'design for full capacity' without load data or member capacity tables
- Required for seismic frames: connection type (SMF, IMF), system R-factor, and prequalification reference per AISC 358
- Required for column base plates: axial load, shear, and overturning moment from the column schedule
Seismic Connection Design Requirements
For structural steel in Seismic Design Categories C through F per ASCE 7, connection design is governed by AISC 341 (Seismic Provisions) in addition to AISC 360. AISC 341 requires that moment connections in Special Moment Frames (SMF) and Intermediate Moment Frames (IMF) be either pre-qualified per AISC 358 or validated by cyclic testing. Pre-qualified connection types include Bolted Unstiffened Extended End Plate (BUEEP), Bolted Stiffened Extended End Plate (BSEEP), Welded Unreinforced Flange — Welded Web (WUF-W), and others listed in AISC 358 Table 1-1. Continuity plate (stiffener) requirements, column panel zone doubler plates, and protected zone restrictions at plastic hinge regions are all required data inputs that only the EOR can provide.
Weld Procedure and Inspection Information
AWS D1.1 structural welding code governs all weld procedures, welder qualification, and weld inspection requirements for structural steel. Connection design must specify: the welding process (SMAW, FCAW-G, FCAW-S, SAW, GMAW), the filler metal classification and strength, the preheat and interpass temperature requirements for the base metal thickness and grade, and the required non-destructive testing (NDT) method — visual, ultrasonic (UT), or magnetic particle (MT). Seismic frame joints in SMF systems require additional requirements under AWS D1.8 (Seismic Supplement) including demand-critical weld designations, welding procedure specification (WPS) qualification, and enhanced inspection requirements. All of these must be documented in the connection design for inclusion on the shop drawing.