**Where you can use this:** [Atlas Tube HSS Connections Hub](https://connectionshub.atlastube.com/login/organisations?src=CALCSDOCS) only **Status:** Beta · **Region:** US · **Design codes:** AISC 360-22, AISC Design Guide 39 ## What this calculator does Designs a moment connection between a wide-flange beam and a concrete-filled HSS column using a bolted extended end plate, in the four-bolt extended unstiffened configuration. Two design paths exist, and the calculator picks between them automatically. | Path | When it applies | Behaviour | | ----------- | ------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------- | | Thick plate | End plate thickness at or above the thick-plate minimum | Plate is stiff enough that prying is not considered | | Thin plate | End plate thickness below the thick-plate minimum | Prying action, bolt rupture under combined tension and prying, and end plate flexural yielding all become live | Engineers often want a thinner end plate for cost or geometry reasons, but the standard thick-plate procedure does not cover it. Before this update, the thin-plate checks had to be done by hand or in a separate spreadsheet alongside the calculator, which created extra work and a risk of inconsistency between the two. ## Inputting key properties 1. **Select the WF beam section and grade.** 2. **Select the concrete-filled HSS column section, steel grade and concrete strength.** 3. **Enter the end plate thickness.** An **End Plate Classification** widget appears directly below this input showing whether the design is on the thick or thin plate path. A second flag in the End Plate Capacity section further down confirms thin end plate behaviour, so you can see which path you are on from either end of the sheet. 4. **Enter the threaded rod diameter, grade and layout.** 5. **Enter the weld sizes.** Watch the End Plate Classification widget as you vary plate thickness. Crossing the thick-plate minimum changes which limit states run, so a small thickness change can move the governing check. ## Applying loads Moment, shear and axial demand at the connection. On the thin plate path, shear is routed to the **compression-side rods only**, following the DG 39 SCO assumption, and a shear strength check for those rods appears under Threaded Rod Capacity. The tension-side rods are assumed not to carry shear. ## Reviewing the calculations ### Thin plate path | Check | Symbol | Reference | | --------------------------------------------------------------------------------------- | --------------- | ----------------------------------------------------------- | | End plate required flexural strength, adjusted for tensile axial load | `M_eq,thin` | AISC DG 39 | | Required end plate thickness for thin plate design | `t_p,reqd,thin` | AISC DG 39 | | Bolt pretension force | `T_b` | AISC 360-22 Table J3.1 | | Prying action force, with prying geometry `a'`, `w'`, `F'` | `Q_max` | AISC DG 39 Section 3.4 | | Bolt rupture with prying action, including minimum required rod diameter | | AISC DG 39 Table 5-10, phi = 0.75 LRFD, Omega = 2.00 ASD | | End plate flexural yielding, yield-line parameter `Y_p` for the four-bolt configuration | | AISC DG 39 Eq. 5-3, phi\_d = 0.90 LRFD, Omega\_d = 1.67 ASD | | Compression-side rods carrying shear | `n_rods_comp` | Drives required shear strength per threaded rod | ### Both paths Column face and concrete-fill limit states, weld capacity and beam-side checks run as normal. ## Assumptions and exclusions * Four-bolt extended unstiffened configuration only. * The thin plate path activates automatically. It is not a manual toggle. ## Related * [Concrete-filled HSS column](/docs/connections_hub/calculators/concrete_filled_hss_column) * [HSS to HSS moment connection](/docs/connections_hub/calculators/hss_to_hss_moment)