Connection Stiffness Implementation Procedure A

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CONNECTION STIFFNESS IMPLEMENTATION PROCEDUREFOR ETABS/SAP/STAAD USERS

Modeling of Global Frame Using SidePlate Connection Technology:Effective use and correct implementation of the inherent SidePlate connection stiffness on the global lateral

frame of a structure results in one or more of the following:

Significant reduction in the required lateral frame beam and column weight and/or size needed to satisfy

allowable building drift criteria

o Saves 20-30% in lateral steel tonnage when compared to all other moment connection systems

Reduction in the number of moment connections

Facilitates the use of pinned boundary conditions, in lieu of fixed, at the base of steel frame columns,

which results in simplified detailing and lower foundation costs

Removal of unwanted diagonal braces by converting the lateral braced frame system to a lateral moment

frame system eliminates the otherwise required coordination with other disciplines .

o A slight increase in lateral frame weight is expected, which is offset by a decrease in foundation cost and

no loss of useable building space (i.e. diagonal braces typically result in a 2-5% loss in usable area)

This is done by replacing beam and column stiffness with the SidePlate lateral connection stiffness, which is

simulated in the steel frames mathematical computer model as follows: use 100% rigid panel zone, increase

the beams moment of inertia, Ix, to approximately 3*Ix (seismic displacement controlled) or 1*Ix (wind dis-

placement controlled), for a typical distance of approximately 77% of the nominal beam depth (Db) beyond

the face of column flange, and increase the beams depth to 3 plus the nominal beam depth to account for

the added stiffness due to the depth of side plates.


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The SidePlate connection stiffness implementation steps are as follows for ETABS/SAP users:

ETABS UserMETHOD 1

THE ETABS BUILT-IN SIDEPLATE FEATURE automatically creates a non-prismatic beam where each fixed

beam end represents the appropriate SidePlate connection stiffness properties from the column face to-

wards the beam centerline as follows:

A section extends from column face to 77% of the nominal beam depth. The SIDEPLATE section, which

consists of the physical side plates {A}, cover plates {B} and beam, has an approximate moment of inertia

(3) times that of the beam alone for R=8 applications and (1) times the moment of inertia of the beam for

R=3 applications.

STEP 1: GEOMETRIC COMPATIBILITY & PRELIMINARY STRONG COLUMN WEAK BEAM RULES

When sizing the frame beam-to-column combinations for a SidePlate moment frame, the following

rules of thumb should be maintained:

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 DE-

SIGNS ONLY:

(Zx,col) > 1.7* (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, includ-

ing 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.


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STEP 2:

Select all moment frame beams.

STEP 3:

Click on Assign > Frame > Moment Frame Beam Connection Type > Side Plate Option > OK

(see Fig. 2)

STEP 4: MODEL SIDEPLATES PANEL ZONE

Select all moment frame beams and columns:

Assign > Frame > End Length Offsets >

Rigid-zone factor = 1 > OK.

(see Fig. 3)

Note: All full-scale testing programs demonstrated very

little contribution to the total overall drift from the panel

zone. Thus, it has been deemed by various prequalifica-

tion committees that the flexibility the panel zone does

have is negligible and can be considered as 100% rig-

id. Thus, it would be incorrect to utilize the ETABS Panel

Zones feature.

STEP 5: CONNECTION WEIGHT

To obtain the approximate connection plate weight for a specific project, simply email your ETABS model

to [email protected]. One of our engineers will review the model for validation and reply with the

connection plate weight.

ETABS end length offsets.

ETABS SidePlate built-in feature.


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ETABS UserMETHOD 2

USING NON-PRISMATIC BEAM SECTIONS

Another way of implementing SidePlate connection properties is to use non-prismatic beam sections. This

method can also be used for seismic or wind applications to help improve steel stress ratios if the current de-

sign is at or above the allowable code values due to present limitations with the built-in SidePlate feature.

STEP 1: SAME AS METHOD 1.

STEP 1A: BE SURE TO ASSIGN ALL MOMENT FRAME BEAMS AS STANDARD MOMENT CONNECTION

If the built in feature is still turned on, the non-prismatic beam section will have essentially double Side-

Plate stiffness, which will overestimate the strength of the connection.

STEP 1B: SELECT ALL MOMENT FRAME BEAMS.

Assign > Frame > Moment Frame Beam Connection Type > Standard Moment Connection > OK.

STEP 2A: CREATING THE SECTIONS FOR THE NON-PRISMATIC BEAM (I.E. XXSP)

1 TOTAL PER NON-PRISMATIC BEAM (SEE FIG. 4).

Click define > Frame Sections > Choose Add Property from the drop down menu. Input connection prop-

erties per the PDF entitled Engineers Design Guidelines.

Make sure the material is the steel material being used on the rest of the project.

For start/end section, there exist two side plates, the beam, cover plates and angles which is referred to as

the SP section. Change the Section name to represent the sections weight + SP. (e.g. For W24x55, this

section would be called 55SP.)

o Dimensions: Depth will be nominal beam depth plus 3. Width is the approximate average column

width used with this beam section.

Note: the area inputs are the same as that for the beam alone to preclude double counting of connection weight.

ETABS general section for non-prismatic beam sections


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STEP 2B: CREATING THE ACTUAL NON-PRISMATIC BEAMS (SEE FIG. 5)

To Create Non-Prismatic Section: Choose Add Non-prismatic from drop down menu.

Change Section Name to sectionNPSP (e.g. W27x94NPSP)

Change Start Section and End Section to XXSP, which in this case is 94SP section.

Typical Length = 77% of beam depth (i.e. can range between 75% to 100% of beam depth).

Note: SidePlate connection lengths are set to Absolute type.

Where the beam section in the middle is set to

Variable (this accounts for different bay widths

in which this section may be used).

All EI33 and EI22 Variations are Linear

SAP & STAAD UsersSTEP 1: GEOMETRIC COMPATIBILITY & PRELIMINARY STRONG COLUMN WEAK BEAM RULES:

When sizing the frame beam-to-column combinations for a SidePlate moment frame, the following

rules of thumb should be maintained:

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 differ-

ence 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:

(Zx,col) > 1.7* (Zx,bm) for 1-12 stories (rule of thumb)

Background: The above equation takes into account the latest Seismic Provisions equation for SCWB compli-

ance 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.

STEP 2: MODEL THE BEAM END PROPERTIES

To model SidePlate connection properties, the lateral beam needs to be broken up into three segments.

a) Insert a new node at distance equal to approximately 77% of the nominal beam depth plus the column

depth.

b) The beam element between the new nodes is assigned the proposed standard AISC frame beam size.

c) For the beam elements that are from the centerline of column to the new node (e.g. at end of side plates),

assign a beam just like the center portion, but modified with properties per the PDF entitled Engineers

Design Guidelines.


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STEP 3: MODEL THE PANEL ZONE

Select all moment frame beams and columns.

Assign a rigid end offset equal to half the column depth and half the modified beam end depth.

STEP 4: CONNECTION WEIGHT

To obtain the approximate connection plate weight for a specific project, simply email your model to

[email protected]. One of our engineers will review the model for validation and reply with the

connection plate weight.

Connection Stiffness Implementation Procedure A

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