Tech Tips

The following Technical Tips for architects and structural engineers represent some
of the most frequently asked topics regarding SidePlate connection technology:

Use of Deeper Frame Columns

In order to achieve the most economical steel moment frame system possible in terms of lowest possible steel tonnage and steel fabrication costs, it is best to select a frame column that is proportioned like a rectangular section (e.g. deeper column like W21x or W27x) versus a square (e.g. W12x or W14x). Doing so results in a column that has the same structural stiffness when compared to a W14x column, but for half of the steel weight resulting in 1-3 lbs/square foot in overall steel tonnage savings or about $1 - $3/SF in construction cost savings.

Since the majority of moment frame columns occur around the perimeter of a building, the great majority of columns in the interior space will be gravity load resisting and can be sized appropriately (e.g. Square tube columns, W12x or W14x). However, depending on the overall building configuration and number of frame columns available in each direction, occasions do arise where interior moment frame columns are required. Such columns can be a combination of both deep and shallow without sacrificing economy.

When deeper columns are oriented perpendicular to the slab edge such as at corners, it typically is prudent to locate such column several inches off the main grid line as shown below.

>> View Diagram

Edge of Slab Location

Welded (FRAME): When deciding the appropriate distance from the center line of perimeter steel framing to the edge of slab, it is important to keep in mind the thickness of the side plates (i.e. ranges from ½" - 2 ½") as well as the horizontal extension of the bottom cover plate beyond the face of the side plate (i.e. ranges from 1 - 2 ½") that occur at the perimeter beam-to-column joints so that exterior curtain wall systems are not interrupted by the presence of the side plate connection itself.

Bolted: When deciding the appropriate distance from the center line of perimeter steel framing to the edge of slab, it is important to keep in mind the thickness of the side plates (i.e. ranges from ½" - 1 ½") as well as the horizontal extension of the top angle beyond the face of the side plate (i.e. ranges from 3 ½" - 4") that occur at the perimeter beam-to-column joints so that exterior curtain wall systems are not interrupted by the presence of the side plate connection itself.

For anticipated project specific side plate connections, call SidePlate Systems for more information.

>> View Diagram

Extension of Side Plates

The side plates typically extend horizontally beyond the face of column flange approximately 80% of the frame beam depth (e.g. typical ranges from 18"-30").

Welded (FRAME): The side plates no longer extend vertically below the bottom of frame beam as they once did. Hence, the only physical item that extends below the bottom of the beam is the thickness of the bottom cover plate which is typically no thicker than 1".

Bolted: The side plates do extend vertically below the bottom of frame beam by 3½" - 4".

Slab Depressions at Moment Frame Columns

For slab depressions adjacent to a SidePlate connection, it's important to keep in mind that the side plates typically have a vertical extension of about ¾" (Bolted) or 2½" - 3½" (Welded) above the top of steel for an average horizontal distance of approximately 80% of the depth of the moment frame beam from the face of column flange. Shorter vertical extensions may be possible with the use of a slightly thicker side plate. Refer to graphic below. Please contact SidePlate Systems for details.

>> View Image

Steps in Floors at Moment Frame Columns

For steps in floors adjacent to a SidePlate connection, it's important to keep in mind that the side plates may be tapered as shown in the detail below as required per the architectural design. As such, these areas need to be coordinated between the structural engineer and the architect. Refer to sample detail below. Please contact SidePlate Systems for details.

>> View Diagram

Column - Beam Relationship

Create the lateral model as customary for any project using steel moment frames. When selecting preliminary lateral beam and columns sizes, it is important to keep in mind the following two rules:

WELDED GEOMETRIC COMPATIBILITY: bbf + 1.1tbf + 1/2" ≤ bcf

Background: The SidePlate connection typically consists of cover plates at the beam ends to bridge the difference between the beam flange width and the wider column flange width. The cover plates are fillet welded to the beam flange edges of which the top cover plate is detailed to be approximately the same width as the column flange width.

BOLTED GEOMETRIC COMPATIBILITY: bbf + 1 1/2" ≤ bcf

Background: The SidePlate connection typically consists of a cover plate and angles at the beam ends. The cover plate is fillet welded to the beam flange edges.

STRONG COLUMN WEAK BEAM COMPLIANCE FOR R=8 SMF DESIGNS ONLY:
Σ (Zx,col) > 1.7*Σ (Zx,bm) for 1-12 stories (rule of thumb)

Background: The above equation takes into account the latest Seismic Provisions equation for SCWB compliance of SMF connections, including an approximate allowance for reduction in column capacity due to axial loads as well as the pushing out of the plastic hinge into the beam.

>> View Diagram

Computer Modeling Tips

To appropriately represent the connection stiffness properties of SidePlate®, the computer model must reflect the following two items:

100% PANEL ZONE

  • RAM FRAME (v14.04+) — Automatically incorporated when SidePlate is assigned as the Frame Beam Connection Type (see below)
  • RAM FRAME (v14.03 and older) — assign all frame beam and columns with a rigid end zone of a 0% reduction (refer to "Connection Stiffness Implementation Procedure for RAM v12 & v13")
  • ETABS & SAP 2000 — Assign all frame beams and columns with a Rigid End Offset of "r=1"
  • RISA — Assign Rigid End Offsets = 1.0

CONNECTION PROPERTIES BEYOND COLUMN FLANGE

The SidePlate connection typically extends horizontally beyond the face of column flange approximately 80% of the nominal frame beam depth (e.g. typical ranges from 18"-30"). The connection properties are different for high seismic (inelastic) applications versus wind (elastic) and low seismic applications.

For R=8 designs, seismic displacement will typically govern the size of the lateral beams and columns. For R=3 designs, wind displacement will typically govern.

For seismic displacement controlled lateral members, modify the properties of the beam ends for a distance DIM A (use typical 77% of beam depth):

Ix = 3*Ix of frame beam
Depth = nominal frame beam depth + ≈3" (e.g. SidePlate depth)
Sx = (2*(3*Ix))/(Depth of SidePlate)
Zx = 1.15*Sx value (above)

  • RAM FRAME v14.04+ — Under Criteria, select SidePlate — Seismic Displacement (this automatically incorporates the appropriate properties). Then assign the moment connection type as SidePlate using the Assign — Beams - Connection command — refer to the PDF "Specifying and Designing SidePlate® Moment Frames in the RAM Structural System"
  • ETABS — use built-in feature by assigning all frame beams to use "SidePlate" beam type
    Note: The modified Sx portion is not included in the ETABS built-in feature. If overstresses of 1.25 or less are encountered in the beams, the beams may not be overstressed when checked at the end of the side plates. In order to confirm this, non-prismatic beams will need to be utilized — refer to PDF "Connection Stiffness Implementation Procedure for ETABS/SAP"
  • RISA/SAP 2000 — Insert a node along the frame beam located at approximately (½*frame column depth + 77% frame nominal beam depth). Assign a new member between centerline of frame column and new node that has the properties above.

>> View Diagram

For wind displacement controlled lateral members, modify the properties of the beam ends for a distance DIM A (use typical 77% of beam depth):

Ix = 1*Ix of frame beam
Depth = nominal frame beam depth + ≈3" (e.g. SidePlate depth)
Sx = (2*(1*Ix))/(Depth of SidePlate)
Zx = 1.15*Sx value (above)

  • RAM FRAME v14.04+ — Under Criteria, select SidePlate — Wind Displacement (this automatically incorporates the appropriate properties). Then assign the moment connection type as SidePlate using the Assign — Beams - Connection command — refer to the PDF "Specifying and Designing SidePlate® Moment Frames in the RAM Structural System"
  • ETABS — create a non-prismatic beam to create properties above — refer to PDF "Connection Stiffness Implementation Procedure for ETABS/SAP"
  • RISA/SAP 2000 — Insert a node along the frame beam located at approximately (½*frame column depth + 77% frame nominal beam depth). Assign a new member between centerline of frame column and new node that has the properties above.

>> View Diagram

Moment Frame Protected Zone
(for IMF & SMF Applications Only)

AISC Seismic Provisions prohibit certain attachments in the protected zone for all Special and Intermediate Moment Frame applications. If required, the protected zone will be identified in the SidePlate details. SidePlate's protected zone is identified as shown in the following diagram:

>> View Diagram

Lateral Bracing of Beams
(for IMF & SMF Applications Only)

EOR shall provide lateral bracing of the frame beam's bottom flange in accordance with the latest AISC Seismic Provisions, where the length of the beam is defined as the distance between the ends of the side plates. Supplemental top and bottom flange bracing at the expected hinge is not required since lateral bracing of the beam at or near the plastic hinge is provided by the side plates as proven by full-scale tests.

Lateral Bracing at Beam-to-Column Connections
(for SMF Applications Only)

The SidePlate connection is composed of two parallel side plates that are welded to the outside edges of the column flanges for the full depth of each beam plus a certain length above. In addition, horizontal shear plates are welded to the inside edges of the column web at the top and bottom of each side plate. This configuration creates a 100% rigid panel zone and prevents the column flanges from buckling at the levels of top and bottom beam flanges and beyond. The connection also provides the adequate 2% lateral bracing at these levels.

All of the full-scale tests were completed without bracing of the column flange at top or bottom beam flange and all configurations had SCWB << 2.0. Test results showed no flexural yielding or lateral-torsional buckling in the column. Hence, the SidePlate® moment connection system is considered to be a Braced Connection in accordance with AISC Seismic Provisions Section 9.7.

Attaching to Face of Side Plate

It is acceptable to weld to the face of the side plates in the area indicated using the project approved minimum preheat.

>> View Diagram

Curved Moment Frames

Due to the inherent torsional robustness of the SidePlate connection, curved moment frames are easily achievable without compromising performance by utilizing one of the following typical methods:

  1. A skewed moment frame beam is shop cut into three pieces, their ends mitered to create the required beam skew angle and then complete joint penetration (CJP) shop welded back together. Typical skew angles range between 2-15 degrees without requiring any special analysis. Field installation is the same as straight beams using fillet welds. In order to resist the out-of-plane force in the beam due to the skew, appropriate lateral bracing of the bottom beam flange must be provided within 12" of the mitered joint — refer to detail below.

    For angles greater than 15 degrees and up to 30 degrees, contact SidePlate Systems for additional solutions.  >> View Diagram
  2. A skewed moment frame beam with bent side plates is the same concept as the skewed moment frame beam in option 1) where the beam can be a series of 3 straight segments, but instead the curvature begins just passed the column flanges within the gap regions by bending the side plates. Alternately, the beam can be straight from side plates to side plates - refer to detail below. Please Contact SidePlate Systems for details.  >> View Diagram
Cantilevers (Drags similar)

Cantilevers can be used at SidePlate connections whether they are framing into the face of the moment frame column flange (e.g. parallel to the moment frame beam) or framing into the face of the side plate (e.g. perpendicular to the moment frame beam).

For conditions where the cantilever beam is parallel to the moment frame beam and

  • Cantilever is about 4' or less from the face of column flange, the typical detail is to simply complete joint penetration (CJP) weld the cantilever beam to the moment frame column flange. Short cantilevers like this could be shop welded to minimize field welding.
  • Cantilever is greater than 4', there are two options that can be done:
    • Option 1) Field CJP weld the cantilever beam to the column flange, or
    • Option 2) use a two-sided SidePlate® moment connection and field fillet weld the cantilever beam to the side plates.

Note: option 2 is commonly done for long cantilevers and/or heavily loaded cantilevers.

For conditions where the cantilever beam is perpendicular to the moment frame beam, there are three possible scenarios that can occur:

  1. Cantilever beam is shallower than the moment frame beam
  2. Cantilever beam is deeper than the moment frame beam
  3. Cantilever beam is the same depth series as the moment frame beam.

For shallower cantilever beams, it is strongly recommended whenever possible to utilize a cantilever beam that is one beam depth series shallower than the moment frame beam depth to minimize the additional flexural loads imparted onto the side plates, thus minimizing any increase to the thickness of the side plates — refer to sample detail below.

>> View Diagram

For cantilever beams deeper than the moment frame beam, no additional special considerations are required — refer to sample detail below for a typical detail used for these conditions.

>> View Diagram

For same depth or identical sized cantilever beams, this condition is discouraged because of the bottom of the cantilever beam will frame directly into the bottom edge of the side plate, thus not allowing an appropriate CJP welding of the cantilever beam's bottom flange to the face of the side plate. If this condition is essential and can't be eliminated, please contact SidePlate Systems for additional solutions that are available upon request.

Sloping Roofs and Exterior Floors

Sloping roofs and sloping exterior framed floors are typically sloped for drainage and/or architectural design purposes up to a maximum of 1.5" per foot. Slopes greater than 1.5" per foot are possible. Please contact SidePlate Systems for details.

SidePlate® moment frames can be easily sloped in a variety of ways as depicted below:

>> View Diagram

Perpendicular Braces to SidePlate Moment Connections

Diagonal bracing lateral load resisting elements (i.e. wide flange, HSS, BRB or dampers) framing perpendicular to SidePlate® connections can be easily accommodated by utilizing a detail such as:

>> View Diagram

Termination of Moment Frame Column and Roofs

The termination of moment frame columns above the top of steel need to be coordinated to ensure that the top of the moment frame column assembly is within the finished floor or roof elevation. For standard popped out conditions, this distance is typically about 4" above the top of steel — refer to popped out option detail below.

>> View Diagram

For conditions where this distance is required to be less than 4", there is a recessed option which can achieve a 2"-3" distance — refer to recessed option detail below.

>> View Diagram

Termination of Moment Frame Biaxial Column and Roofs

For biaxial moment frame column applications only, this distance is a minimum of 8" above the top of steel. Every effort should be made in design to terminate such biaxial moment frame columns at a level below the roof to preclude the additional detailing that may be required at roof conditions.

Facade Attachments

When façade attachments occur at perimeter moment frame columns, it should be noted that the top of the horizontal shear plates (resting on top of the side plates) are typically 3"-4" above the top of steel and should coordinated with the façade manufacturer.

For high seismic projects only, façade attachments on moment frame beams need to be coordinated between the architect and the structural engineer of record to preclude any welding to the beam flanges located within the beam protected zone.

For conditions where this distance is required to be less than 4", there is a recessed option which can achieve a 2"-3" distance.

Location of Frame Beam Splice (as occurs)

The location of frame beam splice, DIM F, can be approximated as follows:

  • ½ times the frame column depth + horizontal extension of side plates (77% of beam depth) + 1.25 times the frame beam depth

Call SidePlate Systems for project specific information.

>> View Diagram

Fireproofing

When required by the governing code for certain types of construction, steel SidePlate® connections shall have a fire-resistance rating like that of a "structural frame."

  • The minimum thickness of sprayed on fire-resistive material (SFRM) for steel SidePlate® connections plates, not encased in concrete, shall be determined just like that of a pipe/tube column section with a constant steel wall thickness, which are uniformly heated and protected (the fire exposure of a pipe/tube column is directly analogous to a plate with a 1-sided fire exposure and protection).
  • The SFRM shall have been tested in accordance with ASTM E119 and listed for fire resistive pipe/tube column applications for no less than the required rated time.
  • The contractor shall provide the means for fireproofing across the physical column/beam separation between the bottom beam flange cover plate and the face of the column flange.