Steel connection design and detailing is where structural plan review comments accumulate fastest. The structural engineer sizes the members, but the connections that hold them together must transfer the design forces through bolts, welds, and plates that each have their own capacity checks under AISC 360 (Specification for Structural Steel Buildings). A beam that passes every flexure and shear check can still fail a plan review if the connection details don't show adequate bolt quantities, weld sizes, or plate thicknesses.
This covers the AISC 360 steel design and connection errors that generate the most plan review comments, based on the 2022 edition (AISC 360-22). Most of these apply equally to the 2016 edition.
Bolt and weld specifications
Missing bolt specifications
AISC 360 Section J3 requires that the structural drawings specify the bolt type, bolt diameter, and connection type (bearing/snug-tight, pretensioned, or slip-critical) for every bolted connection. The bolt type determines the nominal strength: ASTM A325 (Group A) bolts have a nominal tensile strength of 120 ksi, while ASTM A490 (Group B) bolts have 150 ksi. The connection type determines whether the bolt is designed for shear through the bolt body, bearing on the connected material, or slip resistance at the faying surface.
Plan reviewers check the structural general notes and connection details for a bolt specification. The most common violation is a set of structural drawings that shows bolted connections in the details but never specifies the bolt type or connection category anywhere on the drawings or in the general notes. Without a bolt specification, the reviewer cannot verify that the number of bolts shown is adequate for the design forces. The second most common issue is connections that require pretensioned or slip-critical bolts (per AISC 360 Table J3.1: connections subject to vibration, fatigue, or connections using oversized or slotted holes) but are not identified as such on the drawings.
Weld size and specification
AISC 360 Section J2 sets requirements for weld size, length, and type. Fillet weld sizes must not be less than the minimums in Table J2.4 (based on the thickness of the thinner part joined) and must not exceed the thickness of the thinner part minus 1/16 inch for parts 1/4 inch or thicker. The effective throat of a partial joint penetration (PJP) groove weld depends on the groove angle and welding process. Complete joint penetration (CJP) groove welds develop the full strength of the connected part.
Reviewers check weld sizes on the connection details against the minimum and maximum requirements, and verify that the weld strength is adequate for the connection demand. Common violations include fillet welds smaller than the Table J2.4 minimum (a 3/16-inch fillet on a connection where the thicker part is over 3/4 inch, requiring a 5/16-inch minimum), weld sizes shown on details that don't match the weld sizes in the weld schedule, and PJP groove welds specified without indicating the effective throat dimension.
Connection design forces
Simple shear connections
Simple shear connections (single plate, double angle, shear end plate) must be designed for the required shear force at the connection. AISC 360 Section J4 covers the limit states for connected elements: shear yielding on the gross area, shear rupture on the net area, and block shear rupture. Reviewers check that the connection detail shows enough information to verify these limit states: plate thickness, plate dimensions, bolt pattern (gauge, spacing, and edge distances), and hole type.
The most common violation is a connection schedule or typical detail that assigns a single connection type to all beams without checking whether the connection capacity matches the beam end reaction for each specific beam. A W12x19 and a W24x84 might both be shown with the same 3-bolt single plate connection, but the W24x84 has a much larger end reaction that may exceed the connection capacity. Reviewers cross-reference the connection schedule against the beam reactions from the structural analysis output.
Moment connections
Moment connections (fully restrained or partially restrained) must transfer the design moment, shear, and axial force at the connection. For seismic applications (SDC C and above), moment connections must also satisfy the requirements of AISC 341 (Seismic Provisions) for the specific seismic force-resisting system. AISC 358 (Prequalified Connections for Special and Intermediate Steel Moment Frames) provides prequalified connection designs that satisfy the seismic requirements without project- specific testing.
Reviewers check that moment connection details reference a specific prequalified connection type from AISC 358 (such as reduced beam section, bolted flange plate, or extended end plate) or provide a project-specific connection design with calculations. The most common violation is a moment frame on the structural plans with no connection details at all, only a symbol indicating a moment connection at the beam-column joint. The reviewer requires either a prequalified connection reference or detailed calculations before approving the design.
Column base plates and anchor rods
Base plate design
AISC 360 Section J10 covers column base plates, including bearing on concrete, base plate bending, and anchor rod design. The base plate must be sized so that the bearing stress on the concrete does not exceed the concrete bearing strength per ACI 318, and the plate thickness must be adequate to resist bending from the column flange loads or the concrete bearing pressure. For moment frames, the base plate connection must transfer the column base moment through a combination of anchor rod tension and bearing compression.
Reviewers check the foundation details for base plate dimensions, thickness, anchor rod size, pattern, and embedment depth. Common violations include base plates that are shown on the structural plans but not dimensioned or detailed, anchor rod patterns that don't match between the structural and foundation drawings, anchor rod embedment depths that aren't specified, and base plate connections for moment frame columns that show only four anchor rods in a pattern that cannot resist the column base moment. The coordination between the structural and foundation drawings is critical: the structural engineer designs the base plate assembly, but the foundation engineer needs the anchor rod loads and layout to design the footing.
HSS and pipe connections
HSS connection design
Hollow structural section (HSS) connections have unique design requirements under AISC 360 Chapter K. The connection capacity depends on the chord wall slenderness, the ratio of branch to chord width (beta ratio), and the load angle. Limit states include chord wall plastification, shear yielding (punching shear) of the chord, sidewall local yielding and crippling, and uneven load distribution in the branch. These limit states are significantly different from wide flange connection design, and many structural engineers who are experienced with W-shape connections underestimate the complexity of HSS connections.
Reviewers check that HSS connections are detailed with adequate information to verify the Chapter K limit states. The most common violation is an HSS truss or braced frame connection shown with a gusset plate welded to the HSS chord wall without checking the chord wall capacity for the concentrated force. A gusset plate connection that works for a W-shape column may cause a local failure in an HSS chord wall because HSS walls are typically much thinner than W-shape flanges. Connection details for HSS members should show the chord wall thickness, the connection plate dimensions, and reference the applicable Chapter K limit states.
Member design issues that show up in connection review
| Check | AISC 360 section | Common error |
|---|---|---|
| Compression member slenderness | Chapter E (E1, E3) | KL/r exceeds 200 for a compression member; bracing points not clearly shown on drawings |
| Flexural member bracing | Chapter F (F1, F2) | Unbraced length Lb exceeds Lr but member capacity not reduced for lateral-torsional buckling |
| Shear in beam webs | Chapter G (G2.1) | Web shear capacity not checked for coped beams where the net section is reduced |
| Combined forces | Chapter H (H1.1) | Beam-column interaction ratio not provided for columns with both axial and bending |
| Serviceability / deflection | Chapter L (L3) | No deflection limits stated; L/360 live load and L/240 total load are typical but must be documented |
These member design issues often surface during connection review because the connection forces depend on the member capacity assumptions. If a beam's unbraced length is longer than assumed in the original design (because intermediate bracing shown on the framing plan is not actually detailed), the reduced member capacity changes the connection demand. Reviewers check for consistency between the framing plan, the member schedule, and the connection details.
Catching steel design issues before submittal
Steel connection review requires cross-referencing the structural framing plans (member sizes, bracing points, connection types), the connection details (bolt patterns, weld sizes, plate dimensions), the structural general notes (bolt specification, steel grade, weld procedure), and the foundation drawings (base plate details, anchor rod patterns). Checking AISC 360 connection requirements alongside ASCE 7 load requirements and ACI 318 foundation requirements in a single pass catches the cross-reference errors that are hardest to find when each component is reviewed separately.