Designing an end-plate moment connection

An end-plate moment connection is a plate shop-welded to the beam end and field-bolted to the column flange, or to a second end plate in a beam splice. The bolts at the tension flange and the end plate in bending carry the moment. The bolts at the compression flange carry the shear. ILX designs the 15 flush and extended configurations of AISC Design Guide 39, End-Plate Moment Connections (2023), Chapter 5, to AISC 360-22. It also checks the column, and designs the continuity plates and doublers the column needs. For seismic moment frames it designs the AISC 358-22 Chapter 6 extended end plates (4E, 4ES and 8ES) for SMF and IMF, and OMF connections by AISC 341-22 E1.6b (see Seismic moment frames).

When to use an end-plate moment connection #

Use it for a beam framing into a column flange, or a beam-to-beam splice, where the joint must carry moment: gravity and wind frames, R = 3 systems designed to AISC 360 only, and seismic moment frames (SMF and IMF with the 4E, 4ES or 8ES, and OMF).

• Flush end plates stay within the beam depth. They suit lighter moments, splices and joints where a projecting plate is in the way.
• Extended end plates project beyond the tension flange, with bolts outside the flange. They carry larger moments, and the stiffened versions add a triangular stiffener on the extension.

For SMF and IMF, AISC 358-22 prequalifies only the three extended end plates 4E, 4ES and 8ES; the other twelve configurations are flagged as not covered for those systems. For a simple shear end plate, use Designing a shear end-plate connection. For welded flanges or flange plates, use Designing an FR moment connection.

Creating an end-plate moment connection #

1. In the wizard's Connection type step, in the Moment group, select End-plate moment.
2. Choose the configuration. Each configuration starts from the plate, bolt and weld geometry of its DG39 Chapter 5 example. The members and loads are not copied.
3. Enter the Connection mark (ME-1, ME-2 and so on by default), the Beam and the Column, then the loads, and select Create.

Change the configuration, procedure and every dimension in the editor afterwards. The toolbar has Design method (LRFD or ASD) and Units (US or Metric), as for the other types. Auto-design is not available for this type yet; the checks propose the end-plate thickness, bolt diameter, continuity plates and doubler they need as suggested fixes.

End-plate configuration and procedure #

The 15 configurations #

The End-plate configuration sets the bolt pattern at the tension flange, the yield-line table and the stiffeners. The bolt rows are counted at one flange.

Four-wide rows have bolts at ±g/2 and ±(g/2 + go). Inside rows sit at pfi, then pb apart, below the inside face of the tension flange. Outside rows sit at pfo (then pb) beyond its outside face.

Configuration fields #

Thick or thin plate: your choice #

DG39 §4.1.1 accepts both procedures. Pick the one you want to design to:

• Thick plate (no prying) (§5.1.1). The plate is stiff enough that the bolts see no prying. The bolts are checked for φ Pt Σ ni hi ≥ Mr,eq (Eq. 5-3). The plate is checked for γr φb Fyp tp² Yp ≥ 1.10 Mr,eq (Eq. 5-4). This gives a thicker plate and smaller bolts.
• Thin plate (prying) (§5.1.2). The plate yields first and the bolts carry prying forces. The plate is checked for γr φb Fyp tp² Yp ≥ Mr,eq (Eq. 5-5). The bolts are checked for φ Σ αi Pqi ni hi ≥ Mr,eq (Eq. 5-6), with the tee-stub prying force at every bolt location. This gives a thinner plate and larger bolts.

γr is 0.80 for flush plates and 1.0 for extended plates (Eq. 5-1). The procedure is shown in the drawing key data and the report title, for example 4E, thick plate.

Bolts at the other flange. DG39 tabulates the bolt pattern at the tension flange only. Same pattern mirrors it at the other flange, as needed for moment reversal. Two compression bolts puts two bolts at pfi from the compression flange, which is enough for shear when the moment never reverses. If any combination puts that flange in tension, a failing check says so.

End-plate loads #

The load modes are those of the FR moment connection (see Moment, shear and axial loads):

• M > 0 puts the top flange in tension. P is positive in tension. Moments are in kip-ft (kN-m), forces in kips (kN).
• The design moment is Mr,eq = Mr + (Tr/2)(d − tbf) (DG39 Eq. 3-30). Axial compression is neglected, which is conservative (§3.5). The flange force is Tr,calc = Mr/(d − tbf) + Tr/2 (Eq. 3-39).
• If the axial term exceeds half the moment, a recommendation warns that the yield-line pattern may change (§3.7.2(11)).
• A moment that changes sign between combinations is a load reversal. The bolts must then be pretensioned (RCSC 4.2(2)).
• Column axial load (compression +) enters the panel-zone strength (J10.6). Column story shear Vrc reduces the panel-zone shear (Eq. 3-34).
• Beam axial force in the panel-zone shear. DG39 Eq. 3-34 (default) uses the equation as written, so beam tension reduces the panel shear. Adds to the flange force adds P/2 to the flange force, as in Example 5.2-1, a knee joint where the axial force acts with the flange force. DG39 does not settle which applies to your frame, so choose it.
• Analysis includes inelastic panel-zone deformation uses J10.6(b) in place of J10.6(a).

End-plate beam and column #

With a cap plate and a flush end plate, the column flange uses the cap-plate yield lines of Appendix A. Appendix A has no cap-plate yield lines for extended plates, so that combination gives a failing check and the flange is checked as a top-of-column flange.

End plate and stiffeners #

The effective plate width bp,eff = min(bp, bf + max(tp, 1 in.)) is used in every yield line and tee stub (Eq. 4-3, §3.7.2(5)). A wider plate is allowed and a recommendation shows the width used.

End-plate bolts #

Snug-tight or pretensioned. DG39 §4.1.3 allows snug-tight Group 120 (A325) bolts for gravity, wind and R = 3 loads that are not fatigue loads and do not reverse significantly. With snug-tight bolts a recommendation says so. Group 150 and Group 200 bolts in tension, and any joint with a reversing moment, must be pretensioned (RCSC 4.2), or a failing check says so.

The pretension Tb matters only in the thin-plate procedure, where Pq = max(Pt − Qmax, Tb) (Eq. 3-27):

• Pretensioned: Tb from AISC 360-22 Table J3.1.
• Snug-tight: Tb from DG39 Table 3-3. It is a fraction of the full pretension for Group 120 and a tabulated value for Group 150. Table 3-3 has no values above 1 in. or for Group 200, so Tb = 0 is used there and a recommendation says so.

Cyclic loading (fatigue). In the Bolts section, Cyclic loading turns on the AISC 360-22 Appendix 3 checks: the tension bolts (Case 8.5, with the thin-plate prying force; 20 % of the load for pretensioned bolts with only steel in the grip) and the beam flange to end-plate weld (CJP, Case 5.4, or fillets, Cases 5.7 and 8.2), for the tension-flange force Tr,calc times the cyclic range of the moment.

End-plate welds #

Three weld rules are left to the engineer by DG39, so ILX asks for them:

• Flange weld demand. DG39 Eq. 3-38 designs the flange weld for the required flange force, but not less than 60 % (LRFD) or 40 % (ASD) of the flange yield strength Fy bf tf. §3.7.5 says the weld is normally designed for the flange yield strength. Flange yield strength does that. The same choice applies to the web weld near the tension bolts (Eq. 3-41).
• Effective flange fillet length. The DG39 examples use different lengths. 2bf − 2k1 is used for rolled beams (Examples 5.2-1 and 5.2-2). 2bf − tw is used in Example 5.3-1. 2bf − tw − 2w deducts the web welds for built-up beams (Examples 5.2-3 to 5.2-6). Automatic uses k1 for rolled beams and the web welds for built-up beams.
• CJP flange welds develop the flange. DG39 §4.2.3 calls for no weld access holes, welding from the outside face of the flange, and a full-depth PJP weld over the web between the flange-to-web fillets. A recommendation repeats this.

Column, continuity plates and doublers #

With Design when required, ILX designs continuity plates when any column limit state at a flange falls short. They are designed for Tr,calc − min φRn of the column limit states at that flange (DG39 Eq. 3-48), using the same J10.8 designer as the FR connection. A doubler is added when the panel zone fails. The designed sizes are offered as suggested fixes. With None, a failing column check stays failed.

Checks the end-plate connection runs #

Every check is run for every load combination and the governing one is reported. See Checks and compliance for reading the results.

End plate.

• Flexural yielding by yield lines: Mpl = Fyp tp² Yp (Eq. 3-15), with Yp from the configuration's table (Tables 5-2 to 5-7, 5-10 to 5-18) and bp,eff (Eq. 4-3). The calculation lists every bolt row's h, s = √(bp g)/2 and the pf, ps values used. Thick plates are checked against 1.10 Mr,eq (Eq. 5-4), thin plates against Mr,eq (Eq. 5-5), both with γr. The required thickness tp,reqd is shown and suggested.
• Extended part, unstiffened extended plates (4E, MRE 1/2, MRE 1/3, 8E/4W, 12-bolt four-wide): shear yielding and shear rupture under the share of the flange force carried by the outside bolts (§5.1.3 A.3; AISC 360-22 J4.2).
• Effective width bp ≤ bf + max(tp, 1 in.) (Eq. 4-3, recommendation). For 4ES, MRE 1/3 stiffened and 8ES, de < s, so that the tabulated yield-line pattern applies (§5.3.1).

Bolts.

• Thick plate: tension rupture without prying, φMnp = φ Pt Σ ni hi ≥ Mr,eq, with Pt = Fnt Ab and φ = 0.75 (Ω = 2.00) (Eq. 5-3). The required diameter db,reqd is shown and suggested.
• Thin plate: tension rupture with prying, φMq = φ Σ αi Pqi ni hi ≥ Mr,eq (Eqs. 5-6, 3-28). Each bolt location is a vertical tee stub (next to a flange) or a horizontal one (next to the web or a stiffener), as in DG39 Fig. 5-1. Each has its own w, b and a (Eq. 3-24), F' (Eq. 3-26), Qmax (Eq. 3-23) and Pq = max(Pt − Qmax, Tb) (Eq. 3-27), all listed. Second interior rows take Pq = Tb. Four-wide rows use the α factors of the tables. If a tee stub has no flexural strength left for prying (a negative radicand in Eq. 3-23), a failing check names the bolt location.
• Shear by the compression-side bolts: bolt shear, bearing on the end plate and on the column flange (AISC 360-22 J3.7, J3.11; DG39 §3.7.2(4)). Tearout does not control (Example 5.2-1).
• Pretension required (RCSC 4.2) and the snug-tight notes above.
• Detailing: g ≤ bf or g + 2go ≤ bf (Eqs. 4-1, 4-2), spacing ≥ 2⅔d (J3.4), side and end edge distances (J3.5, J3.6), and the tightening clearance from the flange (§3.7.2(3), recommendation).

Welds and beam.

• Flange-to-plate fillets for the flange weld demand above (Eq. 3-38; AISC 360-22 J2.4, θ = 90°), and the minimum size (Table J2.4). CJP welds are a note.
• Beam web tension yielding near the tension bolts (Eq. 3-40; J4.1(a)). The web is checked from the flange to 6 in. past the innermost tension row, carrying the share of the flange force of the bolts next to the web.
• Web-to-plate welds near the tension bolts (Eq. 3-41).
• Web-to-plate welds for shear, and web shear rupture along them (J2.4, J4.2(b)), over the lesser of d − 2tf − the tension zone, and d/2 − tf (§3.7.2(10)).
• Minimum web fillet (Table J2.4).

Web stiffeners (flush plates with web stiffeners, Examples 5.2-3 and 5.2-4).

• The web and the stiffeners share the flange force over the tension zone.
• The stiffener-to-web fillets and the base metal shear rupture along them (J2.4, J4.2(b)).
• Length ≥ hws / tan 30° (Eq. 4-4, recommendation).

End-plate stiffener (4ES, MRE 1/3 stiffened, 8ES, 12-bolt stiffened).

• Thickness ts ≥ tbw Fyb / Fys (Eq. 3-36).
• Slenderness hst / ts ≤ 0.56 √(E/Fys) (Eq. 3-37). It is required only for high-seismic-ductility design, so here it is a recommendation.
• Length Lst ≥ hst, a slope of 45° at most (§4.2.5), and Lst ≥ hst / tan 30° (Eq. 4-4, recommendation).
• Fillets: to the beam flange for the stiffener's shear yield strength, and to the end plate for its tensile yield strength, per inch. CJP welds are a note.

Column (beam to the column flange).

• Column flange flexural yielding at the tension bolts, by the yield lines of DG39 Appendix A: Mcf = Fyc tcf² Yc (Eq. 3-43), Rn = Mcf/(d − tbf) (Eq. 3-42). The demand is 1.10 Tr,calc, because the column flange must act as a thick plate (Eq. 3-19). The unstiffened, top-of-column and cap-plate cases each have their own table.
• With continuity plates, the stiffened yield lines of Appendix A, with bcf,eff = 2bs + tcw + max(tcf, 1 in.) (Example 5.3-2). When the stiffened flange is adequate, the unstiffened check becomes continuity plates required.
• Web local yielding at both flanges: Rn = (6 Ct kc + lb) Fyc tcw (Eq. 3-46), with lb = tbf + 2w + 2tp (Eq. 3-47), limited by the plate projection as in Example 5.2-1. Ct = 0.5 when the column top is within dc of the flange force, otherwise 1.0. With a cap plate at the tension flange, the cap plate delivers the force (Example 5.2-1).
• Web crippling at the compression flange (J10.3).
• Web compression buckling (J10.5), two-sided connections only.
• Continuity plates (Eq. 3-48; AISC 360-22 J10.8): width, thickness, length, strength, welds and clips, as for the FR connection (see Column stiffening (J10)).
• Cap plate (Example 5.2-1): the weld to the column flange and the welds to the column web for the flange weld demand, column web shear rupture at the weld (J4.2(b)), and a cap plate at least as thick as the beam flange.
• Panel-zone shear (DG39 Eq. 3-34; J10.6) by J10.6(a) or (b), and with the doubler (J10.9) with its welds to the column flanges.

NOT FEASIBLE is reported when the geometry cannot be built: a bolt hole in the beam flange or web, outer bolts off the plate, tension rows in the compression half of the beam, a web stiffener that does not fit between the rows, a flush plate edge inside the flange weld, or the first bolt row above the column top.

Tested parameter range. The DG39 equations were validated within the tested ranges of Table 5-1 (flush) and Table 5-9 (extended), ± 10 % (§4.1.2). A recommendation lists every parameter outside: pf, pb, g, go, d, bp, tf and, for extended plates, the extension pext. Outside the range the yield-line pattern may differ, so the design rests on your judgment.

Seismic moment frames (AISC 358-22 Chapter 6, AISC 341-22) #

Set Seismic system to SMF, IMF or OMF and a Seismic (AISC 341-22 / 358-22) section opens below the configuration. A Seismic card above the drawings shows the design basis: Ry and Cpr, Mpr, Sh, Lh, Vh, Mf, Ffu, Vu and the protected zone.

Which design applies #

AISC 341-22 E1.6b(c) is the prescriptive detail for beam flanges welded to the column, so it is not an option for an end plate.

The code load combinations always run the DG39 Chapter 5 design as well, so the connection is also checked for the loads you entered. The AISC 358-22 checks run once, by LRFD even when the design method is ASD (358-22 1.3), and their keys start with sm_.

Seismic fields #

The stiffener weld choice of the End-plate stiffener section applies: 358-22 needs a CJP groove weld to the end plate when the stiffener is thicker than 3/8 in. Select CJP to the end plate, fillets to the flange. The continuity plate and doubler fields of the Column section apply as well.

Checks (AISC 358-22 Chapter 6 and AISC 341-22 Chapter E) #

Capacity design (6.7.1 Steps 1 to 4; 2.4): Mpr = Cpr Ry Fy Zb (Eq. 2.4-1). Sh is the lesser of d/2 and 3bf for the 4E (Eq. 6.7-1), or Lst + tp for the 4ES and 8ES (Eq. 6.7-2). Then Vh = 2 Mpr / Lh + Vgravity (Eq. 2.4-3), Mf = Mpr + Vh Sh (Eq. 2.4-4), Vu = Vh + wu Sh (2.5) and Ffu = Mf / (d − tbf) (Eq. 6.7-6).

Prequalification limits (6.2, 6.3):

• every Table 6.1 parameter within its range for the configuration: tbf, bbf, d, tp, bp, g, pfi, pfo and, for the 8ES, pb. 358-22 says "all connection elements shall be within the ranges shown", so there is no tolerance;
• a rolled W or built-up I beam (built-up: web-to-flange fillets ≥ 0.75 tw and ≥ 1/4 in. near the connection, 6.3.1(1));
• a rolled W column no deeper than W36;
• the clear span-to-depth ratio;
• the slab exception;
• width-to-thickness of the beam and column as highly ductile (SMF) or moderately ductile (IMF) members (AISC 341-22 Table D1.1b).

Bolts and detailing (6.5, 6.6): pretensioned A325, A490, F1852 or F2280 bolts (Chapter 4); g ≤ bbf; the minimum pitch; pb ≥ 2⅔ db (8ES); bp ≥ bbf, with the effective width bbf + 1 in. at most; stiffener length Lst ≥ hst / tan 30° (Eq. 6.6-1), with 1 in. landings.

End plate and bolts (6.7.1):

• Bolt rupture without prying: Mf ≤ φn 2 Pt Σ hi, with db,req (Eqs. 6.7-3, 6.7-4) shown and suggested.
• Plate yielding: φd Fyp tp² Yp ≥ 1.11 Mf, with tp,req (Eq. 6.7-5) shown and suggested. Yp comes from Table 6.2 (4E), Table 6.3 (4ES) or Table 6.4 (8ES), Case 1 (de ≤ s) or Case 2 (de > s), with pfi ≤ s.
• 4E only: shear yielding and rupture of the extension, Ffu/2 ≤ φd 0.6 Fyp bp tp and ≤ φn 0.6 Fup An (Eqs. 6.7-7, 6.7-8).
• 4ES and 8ES: stiffener thickness ts ≥ tbw Fyb / Fys (Eq. 6.7-9) and hst / ts ≤ 0.56 √(E/Fys) (Eq. 6.7-10). The stiffener-to-flange weld develops the stiffener in shear. The stiffener-to-plate weld is a CJP, or fillets that develop it in tension when ts ≤ 3/8 in.
• Beam shear at Vu (Spec. G2.1).
• Bolt shear Vu ≤ φn nb Fnv Ab, with the 4 or 8 bolts of one flange (Eq. 6.7-11).
• Bearing and tearout on the end plate and the column flange, Vu ≤ φn Σ rni (Eq. 6.7-12). Every bolt of the compression flange is checked, at either flange because the seismic moment reverses. Tearout goes toward the next hole or the plate edge.

The resistance factors are φd = 1.00 for ductile and φn = 0.90 for nonductile limit states (358-22 2.4.1).

Welds (6.6.6):

• The flange weld must be the CJP groove weld without backing, with the 5/16 in. fillet on the inside face. It is demand critical. There are no weld access holes.
• The web fillets near the tension bolts develop the web in tension (Fy tw per inch) from the flange to 6 in. past the farthest row.
• The web fillets of the compression-side zone carry Vu, as DG39 Example 6.3-3 does.

Column (6.7.2), at both flanges:

• Flange yielding: tcf ≥ √(1.11 Mf / (φd Fyc Yc)) (Eq. 6.7-13), with Yc from Table 6.5 (four-bolt) or Table 6.6 (eight-bolt). When the top bolt row is less than s below the column top, the top-of-column yield lines of DG39 Appendix A are used, because the 358 tables assume more than s.
• Web local yielding (Eqs. 6.7-16, 6.7-17), with Ct = 0.5 when the column top is less than dc above the beam.
• Web crippling (Eqs. 6.7-18 to 6.7-21).

If any of these fails, continuity plates are designed for Fsu = Ffu − min(φRn) (Eq. 6.7-22) with the J10.8 designer. They are then checked to AISC 341-22 E3.6f.2: thickness ≥ 0.5 tbf (0.75 tbf two-sided), b/t ≤ 0.56 √(E/(Ry Fy)), width to the beam flange tips, flange welds CJP or fillets ≥ 0.75 t, web welds, and the 358-22 3.6 clips. The 6.4(3) exception for plates ≤ 3/8 in. is also checked. The column flange is then rechecked with the stiffened Yc, with psi and pso measured from the plate faces.

Panel zone and moment ratio: for an SMF, the panel zone by AISC 341-22 E3.6e (Ru = Σ Mf / (d − tbf) − Vc, φv = 1.00, doubler designed, Eq. E3-6) and the column-beam moment ratio by Eq. E3-1. For an IMF, the J10.6 panel-zone check of the code combinations applies (E2.6e).

Bracing and protected zone: supplemental bracing between the end of the protected zone and d/2 beyond it, unless the slab exception applies (6.3.1(7)). Beam bracing spacing per AISC 341-22 D1.2. The protected zone (6.3.1(8)) runs from the column face to the lesser of d and 3bf beyond the end plate (4E), or to the end of the stiffener plus the lesser of d/2 and 3bf (4ES, 8ES). It is hatched on the drawing.

Seismic verification #

ILX reproduces the three worked examples of DG39 Chapter 6, which follow the 358-22 procedure: 6.3-1 (4E), 6.3-2 (4ES) and 6.3-3 (8ES). The comparison covers the capacity design, the bolt and plate design, the stiffener, bolt shear and bearing, the welds, the column side, the panel zone and the moment ratio. Where DG39 departs from the standard as written, ILX follows the standard and the test says why:

• the panel-zone demand (DG39 also subtracts half the beam axial force);
• the tearout of the 8ES end plate (DG39 judges by inspection that it does not control);
• the pitch rule above;
• rounding in Example 6.3-1, where unrounded Mf is 0.3 % over the bolt strength.

The record is in research/67.

End-plate drawings, report and sheet #

The editor draws the connection in elevation and the end plate face-on. The key data strip shows the plate, the configuration and procedure, the flange force, Yp, the continuity plates and the doubler. Open Required strength and flange forces to see Mr,eq and Tr,calc worked out. The calculation report lists the inputs (configuration and procedure, beam, support, seismic basis, loads, end plate, bolts, welds, stiffeners, continuity plates and doubler) and every check; see Reports and Drawings.

End-plate limitations and verification #

Scope

• Seismic: AISC 358-22 Chapter 6 covers the 4E, 4ES and 8ES only. Built-up, boxed and cruciform columns are not designed. The top-of-column (roof) joint uses the DG39 Appendix A yield lines; 358-22 itself prequalifies intermediate-story joints (its Commentary 2.6 calls a top-of-column detail "believed to be capable of providing reliable performance").
• Built-up columns are not modeled: the column is a rolled W, M, S or HP shape. Built-up beams are supported.
• Sloped beams and knee-joint geometry are not modeled. The beam is horizontal and frames square to the column flange.
• Panel-zone tension field action is not used. The panel zone is checked by J10.6 and strengthened with doublers only.
• Column-flange prying is not modeled. The column flange must act as a thick plate (φRn ≥ 1.10 Tr,calc, Eq. 3-19). If it does not, add continuity plates or use a heavier column.

Engineer's choices

DG39 leaves these to you. The defaults are listed above:

• the procedure (thick or thin);
• the bolt pattern at the other flange;
• the flange weld demand rule (60 % / 40 % or the flange yield strength);
• the effective flange fillet length;
• the sign of the beam axial force in the panel zone (Eq. 3-34 or Example 5.2-1);
• snug-tight or pretensioned bolts, and Table 3-3;
• the column top and cap plate;
• the continuity plates and doubler (design when required, provided or none).

Verification

ILX reproduces all 30 non-seismic end-plate examples of DG39, in LRFD and ASD, and the three seismic examples of Chapter 6 (see Seismic moment frames):

• the 15 thick-plate examples of Chapter 5 (5.2-1 to 5.2-6 flush, 5.3-1 to 5.3-9 extended), one per configuration;
• the 15 thin-plate examples of Appendix B (B.2-1 to B.2-6, B.3-1 to B.3-9).

The comparisons cover Yp, the plate and bolt strengths, the prying forces, the welds and the stiffeners, and the column side in the two examples with a column (5.2-1 and 5.3-2). The method and the example-by-example record are in research/64. See How ILX was verified.