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Computer Modeling/Stiffness

To appropriately represent the connection stiffness properties of SidePlate®, the computer model must reflect the following two items, also described in Figure E1:

  • 100% Rigid Panel Zone
  • Connection Properties Beyond Column Flange

Figure E1 – Connection Stiffness and Stress Modeling

SidePlate's engineers will do this for your model, but you can also model SidePlate connection stiffness yourself in most analysis software. Click a logo below for info. 

 

 Click here for more detailed RAM modeling instructions

 

 


Column-Beam Relationship

For a SidePlate connection to be constructed, there must be adequate room for the flanges of the beam to fit in between the side plates that are attached to the flanges of the column. To ensure that a compatible beam is chosen for a given column size, follow the guidelines in Figure E2 below.

  • Bolted Geometric Compatibility - bbf + 1” ≤ bcf
  • Welded Geometric Compatibility - bbf + 1.1* tbf + 1/2” ≤ bcf

Figure E2 - Partial SidePlate Connection Showing Geometric Compatibility

 

 


Base Fixity

In an ideal world, for steel moment frame economy, every base condition would be completely fixed. It is important to consider the base detailing at a building before deciding how to model it. See the below matrix of advantages and disadvantages for each:

 

Advantage

Disadvantage

Fixed

  • Lighter/shallower steel columns and beams
  • Minimal issues with weak/soft story (R=8)
  • Complications in base detailing
  • Increases in footing size
  • Grade beams may be needed

Pinned

  • Ease of detailing base plate and footings
  • Decrease in footing size
  • Issues with weak/soft story (R=8)
  • Higher drifts in the lower floors
  • Heavier/deeper steel columns and beams at lower floors

Cantilevers

Cantilevers can be used at SidePlate connections whether they are framing into the face of the side plate or the moment frame column flange. In order to ensure that the best solution is provided and the detailing is clear, please coordinate these connections with SidePlate Systems. Typical cantilever details fall into two main categories – those that are perpendicular, or run through the SidePlate connection, and those that are in-plane, or opposite of a one-sided SidePlate connection at the end of the frame.

In Plane / Parallel
In-plane or parallel cantilever connections occur at the end of a moment frame. These cantilever stubs often use complete joint penetration (CJP) welding of the beam flange to the column flange and rely on continuity plates between the column flanges. This configuration can often be used without interacting with the SidePlate connection. in many instances changes the SidePlate connection to a two-sided connection for an in-plane cantilever may be more economical and/or easier to erect. 

Out of Plane / Perpendicular
Out of plane or perpendicular cantilever connections may occur at any point along the moment frame. Where these connections occur at the SidePlate connection on the column, the gravity forces are included in the SidePlate connection design. If accurate cantilever and backspan beam sizes and geometry are not included in the analysis model, these should be coordinated with SidePlate Systems to ensure adequate connection designs.


Penthouses

A penthouse structure is meant to be an unoccupied space (likely for mechanical purposes) at the uppermost level of a structure. Per the IBC Section 1509.2, if a penthouse’s area is greater than 1/3 of the area of the story below, it is considered a story. If a structure has a penthouse level that does not meet these requirements (either it is occupied or it is greater than 1/3 the area), it should be considered a story. The uppermost story may use an alternate lateral system provided it meets the requirements of the code. It is important to note the exceptions to Table 12.2-1 in ASCE 7-10. If Special Moment Frames are selected as the lateral system for the penthouse level, the columns should be continuous to the base of the building.


Seismic Provisions

I. Prequalification

IAPMO Evaluation Report

II. Moment Frame Protected Zones

The AISC Seismic Provisions (ANSI/AISC 341) prohibit certain attachments in the protected zone for all Special and Intermediate Moment Frame applications. A protected zone (PZ) occurs where the beam or column is subject to inelastic strain and a plastic hinge forms or, more simply, the element bends and buckles under high seismic loads. For the SidePlate connection there are protected zones on the beam and on the side plate. The protected zone locations are illustrated in Figure E3 below.

Figure E3 - SidePlate Connection Protected Zones; a) field bolted and b) field welded

NOTE: that it is acceptable to weld to the face of the side plates outside of the protected zone provided that connections do not interfere with the fabrication and erection of the system.

III. Span to Depth

Each SidePlate connection type has a span to depth limit. The hinge-to-hinge span of the beam can be approximated by the following equation (final span to depth calculations are done by SidePlate connection design software and provided in the calculation package):

The ratio of the hinge-to-hinge span of the beam, Lh, to beam depth, d, shall be limited to:

SMF Field Bolted: 3.5 or greater.
IMF Field Bolted or Welded: 3 or greater.
SMF Field Welded: 4.5 or greater.

NOTE: For projects under California’s OSHPD jurisdiction, Lh to d, shall be limited to 5.0 or greater.

IV. Lateral Bracing of Beams

The engineer of record shall provide lateral bracing of the frame beam’s bottom flange in accordance with the latest AISC Seismic Provisions. The distance of unbraced length can be calculated from the ends of the side plates, as they provide lateral bracing of the beam, unless otherwise prohibited by the jurisdiction.
Beams should be laterally braced at a distance not to exceed:

The requirements for lateral bracing are based off of testing, as discussed in this section of the Commentary on the Seismic Provisions for Structural Steel Buildings (341). Supplemental top and bottom flange bracing at the expected hinge is not required for SidePlate because it is provided by the side plates.

Lateral bracing of the bottom beam flange may not be possible in some rare cases, such as large openings. In those instances, the engineer may consider torsional bracing such as built-up sections, or adding supplemental gravity columns between floors. Please contact SidePlate Systems to discuss these alternatives.

NOTE: For projects under California’s OSHPD jurisdiction, unbraced length must be measured from the centerline of each column.

V. LATERAL JOINT BRACING

Although AISC 341 requires lateral joint bracing at the top and bottom of beams in Special Moment Frames (SMF), these requirements do not apply to the SidePlate connection. Since there is a physical gap between the beam and the column, the load path does not use continuity plates at the joint, and localized buckling of the column is very unlikely. Additionally, the connection of the side plate to the column flanges provides additional stability at the joint. As a result, the SidePlate connection may be considered braced at the joint by simply providing a perpendicular beam shear tab connection within the joint region. At locations where no perpendicular framing occurs, the effects of a multi-story unbraced column should be considered, especially in weak axis bending and buckling outside of the SidePlate connection joint region.

VI. Collectors and Chords

In some configurations of moment frames, the load path for chords, collectors, or other axially loaded members will need to pass through perpendicular to the SidePlate connection. Coordination of these details will be similar to the coordination of cantilevers and will rely on the configuration of the engineer’s details.

In Plane / Parallel
Unless the detailing will conflict with the SidePlate connection, there is no need for coordination. 

Out of Plane / Perpendicular
Out of plane or perpendicular drag connections forces are included in the SidePlate connection design. In order for the SidePlate connections to be designed adequately for these conditions, drag/chord beam sizes and design level forces perpendicular to any SidePlate Connection will need to be provided with the preferred type of detailing (whether it be through a shear tab, top flange welded, or another mechanism).