SMF Beam-Column Connection

References

2006 IBC Structural/Seismic Design Manual, Volume 3: Building Design Examples for Steel and Concrete

Details

The RBS connection is a pre-qualified connection type per AISC 358. This design example follows the procedure outlined in AISC 358 with reference to AISC 341 and AISC 360.

The basis for the prequalification of the RBS connection is widely attributed to initial RBS connection tests conducted at the University of Texas Ferguson Laboratory (Engelhardt etal., 1996). Extensive additional testing of RBS joint combinations performed as part of projects confirmed the viability of the connection using myriad beam and column sizes. Further information on the research supporting the validity of pre/qualification parameters may be found in FEMA-355D State of the Art Report on Connection Performance and AISC 358.

The following calculations comprise a design methodology that is inherently iterative and requires some experience to gain proficiency. After considering code drift limits and evaluating several combinations for strong column-weak beam and panel zone strength criteria, the combination of a W27x84 beam and W14x176 column was selected for use in the factored load combinations (Part 5), and this combination of beam and column sizes in the computer analysis results in overall frame drifts within the code limits (Part 4). The W14x176 column was chosen to elucidate details associated with doubler plates and possibly reduce the cost of the frame. When given the option, steel fabricators have elected W14x176 columns are to be full-height, one length. Full=height columns without splices were found to be the least-cost option. Column splices in SMFs must comply with AISC 341. The reduced beam section (RBS) connection developed in this example is shown in Figure 3-8 and 3-13

Results

Parameter RAM Connection Reference Difference
Plastic section modulus at the RBS (in.3) 169.3 168.95 < 1% (small difference may be due to error in reference, which uses c = 2.25 in rather than the cited value)
Maximum probable moment at the RBS (kip·in) 10,707 10,686 < 1%
Expected plastic moment of the beam (kip·in) 13,420 13,420 none
Mf (kip·in) 12,424 12,403 < 1%
Required shear strength (kips) 101 101 none
Minimum required thickness of column flange (in) 1.67 1.66 < 1%
Panel zone shear strength (kips) 469.3 469 < 1%

Input

The following data is input into the New Joint dialog:

Joint Data tab:
  • Joint = BCF
  • Beam / Section = W27x84
  • Beam / Material = ASTM A992 Gr 50
  • Column / Section = W14x176
  • Column / Material = ASTM A992 Gr 50
The following data can be added after the Seismic Parameters option is set in the Connection Design Configuration dialog:
  • Seismic load resisting system = SMF
  • Beam / Length, L = 28 ft
  • Beam / Seismic Design / RBS Connection = Yes
  • Beam / Seismic Design / Horizontal distance to start of RBS cut, a = 6 in.
  • Beam / Seismic Design / Length of RBS cut, b = 22 in.
  • Beam / Seismic Design / RBS cut maximum depth, c = 2.24 in.
  • Beam / Seismic Design / Shear due to gravity loads between plastic hinges, Vg = 26.33 kips
Loads tab:
  • DL / V2 = 16.4 kips
  • DL / M33 = 86.83 kip·ft
  • LL / V2 = 13.3 kips
  • LL / M33 = 77 kip·ft
  • EQ / V2 = 19 kips
  • EQ M 33 = 256.9 kip·ft

Select the Smart Connections/Smart DW connection type.

The following data is input into the Connection Pad:

General Information group:
  • Design criteria / Frame stability considered in analysis = checked (set the option)