Column Connection Checks

This section is specific to column checks for moment connections or shear connections with axial force.

Force Distribution

This section applies to flange forces on moment connections only. Please see Required Flange Forces to see how RISAConnection calculates the flange forces when moment and axial loads are present.

Shear connections are assumed to carry all axial load through the connecting elements.

Moment Arm

The depth of the moment arm between flange forces (d_c) is described below. RISAConnection assumes these to be applied at the centroid of the beam flange (for End Plate and Direct Weld Moment Connections) or that of the flange plates (for Flange Plate Moment Connections).

Concentrated Force Location

For many of these checks where these forces are transferred into the column defines which equation you use in the specification. RISAConnection defines these locations for each moment connection type as:

• Flange plate moment connections: This is taken as the Top Column Dist (from the Loading input section) minus half of the thickness of the flange plate. This is the location where the centroid of the top flange plate transmits its force into the column.
• End plate moment connectionsand Direct Weld moment connections: This is taken as the Top Column Dist (from the Loading input section) plus half of the thickness of the beam flange. This is the location where the centroid of the top flange transmits its force into the column.

Note that we always assume the top flange is in compression for these moment connections, or we assume that the moment can be reversed.

k and N Assumptions

The AISC 360-10 specification specifies k as the distance from outer face of the column flange to the web toe of the fillet. Table 1-1 from the 14th Edition Steel Manual list both a k_det and a k_des value. RISAConnection assumes k = k_des for this value.

N is defined as the bearing length of the applied force. Therefore this value differs based on the weld type specified to connect the beam flange to the column or end plate. RISAConnection uses the following assumptions when calculating this value:

Column Flange Bending (Shear Connections)

This column flange bending capacity check is calculated per section J10.1 of the AISC 360-10 specification. Expand this section of the design report and RISAConnection will provide you with the exact equation, code reference, listed variables, as well as the code check value and pass or failure notification.

Top of Column Distance

Per section J10.1 of the AISC 360-10 specification, the available strength shall be reduced if the force application is at a distance less than 10*t_f from the end of the member. This can be addressed in RISAConnection by adjusting the user input Top Column Distance in the Loading section of Connection Properties. Please see the Concentrated Force Location section for more information on how this location is calculated.

For instance, if Concentrated Force Location < 10*t_f, RISAConnection will reduce R_n by 0.5.

Note:

• This is only checked in Shear Connections if the connection includes a tensile axial load.

Column Flange Bending (Moment Connections)

This moment capacity check applies to the Beam Flange Plate Moment Connection. This check is calculated per section J10.1 of the AISC 360-10 specification. Expand this section of the design report and RISAConnection will provide you with the exact equation, code reference, listed variables, as well as the code check value and pass or failure notification. See the Moment Arm section for more information on how this value is calculated.

Top of Column Distance

Per section J10.1 of the AISC 360-10 specification, the available strength shall be reduced if the force application is at a distance less than 10*t_f from the end of the member. This can be addressed in RISAConnection by adjusting the user input Top Column Distance in the Loading section of Connection Properties. Please see the Concentrated Force Location section for more information on how this location is calculated.

For instance, if Concentrated Force Location < 10*t_f, RISAConnection will reduce R_n by 0.5.

Column Flexural Yielding

This check applies to the End Plate Moment Connection. This check is calculated per Section 3.12.15 and Table 3.4 of the AISC Steel Design Guide 4 (Second Edition). Expand this section of the design report and RISAConnection will provide you with the exact equation, code reference, listed variables, as well as the code check value and pass or failure notification.

This check contains some complicated geometry to approximate the yield line pattern. Below are graphical explanations of some of the more complicated terms:

Some End Plate connections do not have column yield line formulas specifically listed in the design guides.

Note:

• The column yield lines for the 8 bolt (unstiffened) connection is not given in the design guides. But, can be found in section 4.4.5.5 and Figure 4-15 of Emmett Sumner's PhD thesis, Unified Design of Extended End-Plate Moment Connections Subject to Cyclic Loading.
• The column yield lines for the MRE1/3 connection is not given in the design guides. But, can be found in section 4.4.5.6 and Figure 4-16 of Emmett Sumner's PhD thesis, Unified Design of Extended End-Plate Moment Connections Subject to Cyclic Loading.
• The 2 bolt flush end plate connections will have the same yield lines as the Yp values in table 3-2 of AISC Design Guide 16. The only difference is that b_p (plate width) is replaced with b_cf (column flange width), t_p (plate thickness) with t_cf(column flange thickness). In addition "s" is used instead of P_f for the distance to the top yield line unless a transverse column stiffener is present in which case the distance between this stiffener and the top row of bolts is used in place of P_f.
• The 4 bolt flush end plate connections will have the same yield lines as the Yp values in table 3-3 of AISC Design Guide 16. The same differences mentioned in the bullet point above for the 2 bolt flush connection also apply to the 4 bolt flush connections.

Column Web Punching Shear (Shear Connections)

The column web punching shear capacity check is calculated per the AISC 15th edition Steel Design Manual section on Plate Elements Subjected to Out-of-Plane Loads on page 9-14. Expand this section of the design report and RISAConnection will provide you with the exact equation, code reference, listed variables, as well as the code check value and pass or failure notification. This check is included for beam to column shear connections with any (compression or tension) axial load.

Unfortunately older versions of the AISC Steel Design Manual do not give direction on out of plane checks on a Wide Flange column web, but you may opt to check these per the AISC 15th edition requirements by selecting the Include AISC 15th Out of Plane Web Checks check-box on the Solution tab of the (Global) Model Settings.

Note:

• Per the direction on AISC 15th edition Steel Design Manual page 9-15, RISAConnection assumes that the column flanges are not restrained and therefore always takes the effective width, c_eff = to the T dimension of the column. This is always the case, regardless of if the connection is bolted or welded because the code does not give specific direction for bolted connections.
• If the column is a HSS Pipe or Tube section, this check is done per AISC Steel Design Manual equation (10-7) for shear tabs, or equation (9-29) for clip angles when the AISC 15th edition design code is selected. Please see the HSS Checks topic for more information.

Column Web Axial Yielding (Shear Connections to Column Web)

The column web axial yield capacity check is calculated per the AISC 15th edition Steel Design Manual equation (9-31) on page 9-16. Expand this section of the design report and RISAConnection will provide you with the exact equation, code reference, listed variables, as well as the code check value and pass or failure notification. This check is included for beam to column shear connections with any (compression or tension) axial load.

Unfortunately older versions of the AISC Steel Design Manual do not give direction on out of plane checks on a Wide Flange column web, but you may opt to check these per the AISC 15th edition requirements by selecting the Include AISC 15th Out of Plane Web Checks check-box on the Solution tab of the (Global) Model Settings.

Column Web Flexural Yielding (Shear Connections to Column Web)

The column web flexural yield capacity check is calculated per the AISC 15th edition Steel Design Manual equation (9-35) on page 9-17. Expand this section of the design report and RISAConnection will provide you with the exact equation, code reference, listed variables, as well as the code check value and pass or failure notification. This check is included for any shear connection with moment at the column due to eccentricity in the shear connection.

Unfortunately older versions of the AISC Steel Design Manual do not give direction on out of plane checks on a Wide Flange column web, but you may opt to check these per the AISC 15th edition requirements by selecting the Include AISC 15th Out of Plane Web Checks check-box on the Solution tab of the (Global) Model Settings.

Note:

• This check includes a column stress interaction parameter, Qf. There are some cases where RISAConnection cannot determine this value, so it relies on the user adjusting this in the Loading input properties:
• 

Column Web Yielding (Shear Connections to Column Flange)

This column web yielding capacity check is calculated per section J10.2 of the AISC 360-10 specification for Wide Flange Columns with beams connected to the column flange. Expand this section of the design report and RISAConnection will provide you with the exact equation, code reference, listed variables, as well as the code check value and pass or failure notification.

Top of Column Distance

Per section J10.2 of the AISC 360-10 specification, there are two equations that apply to this check: J10-2 and J10-3. RISAConnection calculates the Concentrated Force Location to see which of these equations applies. Please see the Concentrated Force Location section for more information on how this location is calculated.

Therefore, if the Concentrated Force Location > d_beam, RISAConnection will use equation J10-2. If the Concentrated Force Location ≤ d_beam, RISAConnection will use equation J10-3.

Note:

• This is only checked in Shear Connections if the connection includes an axial load.
• Column Web failure due to punching shear and / or web plastification (yield lines for moment applied to shear tab) are NOT currently considered.

Column Web Yielding (Moment Connections to Column Flange)

This check applies to Beam Flange Moment Connections and End Plate Moment Connections for Wide Flange Columns with beams connected to the column flange but is calculated slightly differently for each type of check.

Flange Plate Moment Connection

For Flange Plate Moment Connections, this check is calculated per section J10.2 of the AISC 360-10 specification. Expand this section of the design report and RISAConnection will provide you with the exact equation, code reference, listed variables, as well as the code check value and pass or failure notification. See the Moment Arm section for more information on how this value is calculated.

End Plate Moment Connection

For End Plate Moment Connections, section J10.2 of the AISC 360-10 specification is not as clear. Therefore, RISAConnection instead references the AISC Design Guide 4, 2nd Edition which references the AISC 2nd Edition LRFD code.

This code has a much clearer reference to End Plate Moment connections and assumes a larger projection, as shown in the image below.

Expand this section of the design report and RISAConnection will provide you with the exact equation, code reference, listed variables, as well as the code check value and pass or failure notification. See the Moment Arm section for more information on how this value is calculated.

Note:

• For flush end plate connections, the spread of the axial force is not addressed in any of the design guides. Therefore, a value between the two formulas is used (5.5k + N +1.0*t_p). This is rational because it assumes a spread of load on one side is the same as the end plate connection, but on the other side it is assumed to be the same as the direct weld connection.
• In the case of flush end plates with double fillet welds, the plates are extended the distance of the weld leg + an extra 1/16th of an inch for any weld legs greater than 0.25".

Top of Column Distance

Per section J10.2 of theAISC 360-10 specification, there are two equations that apply to this check: J10-2 and J10-3. RISAConnection calculates the Concentrated Force Location to see which of these equations applies. Please see the Concentrated Force Location section for more information on how this location is calculated.

Therefore, if the Concentrated Force Location > d_beam, RISAConnection will use equation J10-2. If the Concentrated Force Location ≤ d_beam, RISAConnection will use equation J10-3.

Column Web Crippling (Shear Connections)

This column web crippling capacity check is calculated per section J10.3 of the AISC 360-10 specification. Expand this section of the design report and RISAConnection will provide you with the exact equation, code reference, listed variables, as well as the code check value and pass or failure notification.

There are three equations that come into play for this check. When the concentrated compressive force to be resisted is applied at a distance from the member end that is greater than or equal to d_col/2 use equation J10-4. If this distance is less than d_col/2, then use either J10-5a or J10-5b. Please see the Concentrated Force Location section for more information on how this location is calculated.

The differentiation between equations J10-5a and J10-5b depends on the ratio of bearing length to overall depth of the beam (N/d). See the Column Moment Checks topic for information on calculating N. If N/d <= 0.2, then equation J10-5a is used. If N/d > 0.2, then equation J10-5b is used.

The program will perform all of these dimensional checks and use the appropriate equation automatically.

Note:

• This is only checked in Shear Connections if the connection includes a compressive axial load.
• When the AISC 15th (360-16) code is selected, this check includes a Qf factor. For all wide flange and HSS columns in tension, this is taken as Qf = 1. For all other cases, see AISC 15th Table K3.2.

Column Web Crippling (Moment Connections)

Web crippling is local buckling that occurs when the web is slender (i.e. h/tw is large). The behavior is more restrained when the point load is applied away from the ends of the member. Because of this there are separate equations for when a concentrated transverse load is located near or away from the end of the member. This limit state is to be checked at each location where a concentrated force is applied transverse to the axis of a member.

The AISC 360-10 Specification section J10.3 gives the capacity equations to consider column web crippling.

There are three equations that come into play for this check. When the concentrated compressive force to be resisted is applied at a distance from the member end that is greater than or equal to d_col/2 use equation J10-4. If this distance is less than d_col/2, then use either J10-5a or J10-5b. This location where this compressive force occurs is defined earlier in this topic.

The differentiation between equations J10-5a and J10-5b depends on the ratio of bearing length to overall depth of the beam (N/d). See information earlier in this topic for information on calculating N. If N/d <= 0.2, then equation J10-5a is used. If N/d > 0.2, then equation J10-5b is used.

The program will perform all of these dimensional checks and use the appropriate equation automatically.

Note:

• When the AISC 15th (360-16) code is selected, this check includes a Qf factor. For all wide flange and HSS columns in tension, this is taken as Qf = 1. For all other cases, see AISC 15th Table K3.2.

Column Web Buckling (Moment Connections)

This check applies to both Beam Flange Moment Connections and End Plate Moment Connections. This check is calculated per section J10.5 of the AISC 360-10 specification. Expand this section of the design report and RISAConnection will provide you with the exact equation, code reference, listed variables, as well as the code check value and pass or failure notification. See the Moment Arm section for more information on how this value is calculated.

Note:

• Technically this check is only valid when there column web is restrained at both flanges (i.e. when there is a moment connection on both sides of the column). However, RISAConnection does not currently have a method to determine if this is the case. Therefore, the connection is always checked for column web buckling.
• When the AISC 15th (360-16) code is selected, this check includes a Qf factor. For all wide flange and HSS columns in tension, this is taken as Qf = 1. For all other cases, see AISC 15th Table K3.2.

Top of Column Distance

Per section J10.5 of the AISC 360-10 specification, the available strength shall be reduced by 50% if the force application is at a distance less than half the depth of the column. RISAConnection refers to this value as the Concentrated Force Location and is calculated per the user input Top Column Distance. Please see the Concentrated Force Location section for more information on how this location is calculated.

For instance, if Concentrated Force Location < 0.5*d_beam, RISAConnection will reduce R_n by 0.5.

Column Panel Zone Shear

Column web panel zone shear is a phenomenon that occurs when double-concentrated forces are applied to a member. A moment connection's beam flange forces creates these double concentrated forces.

These forces cause a shear to the web panel zone that we are checking here.

There are four equations from the AISC 360-10 specification that are used, equations J10-9, J10-10, J10-11 and J10-12. The program assumes that the effect of panel-zone deformation on frame stability is not considered in the analysis, thus equations J10-11 and J10-12 are never used. Whether to use J10-9 or J10-10 depends on the axial force in the column at the location of the connection. This force is input in the Loading section. If this force is <= 0.4*P_c then J10-9 is used. If P_r > 0.4*P_c, then J10-10 is used.

Note:

• When the AISC 15th (360-16) code is selected, this check includes an additional factor, ɑ. For LRFD design, this shall be taken as 1.0. For ASD design, this shall be taken as 1.6.

Story Shear

The actual demand panel zone shear that occurs can be reduced by the story shear coming into the panel zone.

This story shear is also an input in the Loading section. If there is story shear, then the program calculates an M_equivas the design demand. This is a reduced demand based on a reduced panel zone shear due to this story shear. Because the code checks are based on converting the capacities into equivalent moment capacities, the same must be done for the moment demand in this case.

RISAConnection will take all of the inputs, perform the applicable checks and use the appropriate equation.

Column Web Out of Plane Checks

The AISC 15th (360-16) edition Steel Construction Manual introduced explicit out of plane checks for column web connections loaded out of plane. These checks are listed below. Older versions of the Steel Construction Manuals did not include direction for these checks, but RISAConnection will allow you to include the checks along with older codes if you select the "Include AISC 15th Out of Plane Web Checks" check box on the Solution tab of Project Settings.

Column Web Punching Shear

The punching shear limit for a clip angle or end plate connection to a column web is checked per eqn (9-29) on page 9-14 of the 15th Edition Steel Construction Manual. For more detail see Column Web Punching Shear (Shear Connections).

Column Web Axial Yielding

Out of plane transverse loads on a column web are checked per eqn (9-31) on page 9-16 of the 15th Edition Steel Construction Manual. For more detail see Column Web Axial Yielding (Shear Connections to Column Web).

Column Web Flexural Yielding

Out of plane moment loads on a column web are checked per eqn (9-35) on page 9-17 of the 15th Edition Steel Construction Manual. For more detail see Column Web Flexural Yielding (Shear Connections to Column Web).

Out of Plane Check Limitations

• Out of plane checks are not included for supporting girder members because the yield line pattern would not be the same as what is published in the AISC 15th Ed Steel Construction Manual for Column webs.
• Out of plane checks are not included when stabilizer plates are present.
• When the axial load is tension, the yield line dimension c is assumed equal to zero when there is only one row of bolts.
  • When there are more than one rows of bolts, the dimension c is assumed equal to the outermost bolt centerline to centerline spacing (c = row spacing for 2 rows, c = 2*row spacing for 3 rows).
• When the axial load is in compression, the yield line dimension c is assumed equal to the width of the clip angle or end plate.
• RISAConnection assumes that the column flanges are not restrained and therefore c_eff = T per the direction on AISC 15th edition page 9-15. This assumption applies to both welded and bolted connections.
• Threshold limitation: If the axial load is less than 5% of the shear load, RISAConnection will take it equal to zero.

HSS Out of Plane Checks

Please see the section on HSS Checks for the details on similar out of plane checks for HSS connections.