	Applies To
	Product(s):	RAM Connection
	Version(s):	Any
	Area:	Design

Flexural Yielding Calculations

QUESTION: In RAM Connection, how are Mpl and Mstrip calculated?

ANSWER: The design procedure for base plate design in RAM Connection is based on AISC Design Guide 1. The Design Guide includes some design examples that will clarify how these parameters are calculated.

Flexural Yielding (Bearing Interface): The equations used to calculate the plate bending moment in the "Flexural Yielding (Bearing Interface)" check are discussed in Section 3.3.2 of the Design Guide.
Flexural Yielding (Tension Interface): The strip moment in the "Flexural Yielding (Tension Interface)" check is calculated assuming the tensile loads in the anchors generate one-way bending in the base plate about assumed bending lines. The location of the bending lines depends on whether the anchors are placed inside or outside the column flanges. See Figure 3.1.1(b) and Figure 4.5.2 in the Design Guide. The program assumes a 45 degree load distribution from the anchor to the bending line to determine the width of the bending strip.

Steel Design Code (ASD vs. LRFD)

QUESTION: In RAM Connection, are there any design checks that are not preformed when the AISC ASD steel design code is selected versus the AISC LRFD steel design code?

ANSWER: Yes.

Since the ACI Appendix D checks are based on ultimate limit state design, RAM Connection will only complete the ACI Appendix D checks if LRFD is selected for the design method.
The Anchor pullout design for US design codes is limited to LRFD methods. When performing ASD design of a base plate report simply indicates:

NOTES
Anchors only designed for LRFD code

The design code is selected in the Customize Connection Design dialog:

Analysis Axis

QUESTION: In RAM Connection, how are biaxial base plates analyzed?

ANSWER: A linear model is used for the contact stresses calculation between a steel base plate and a concrete foundation. This is different from the "both axis" approach which evaluates the plate for major or minor axis moments individually (with axial).

For more information, read the full paper on this topic: HERE.

Pressure Distribution

QUESTION: In RAM Connection, what is the difference between uniform and triangular pressure distribution?

ANSWER: The uniform distribution considers that the maximum bearing stress below the base plate is uniformly distributed. Then, the bearing length is determined considering the maximum bearing stress along with the tension at the anchors. The triangular distribution is similar, but the maximum bearing stress below the base plate is assumed to be triangularly distributed and the centroid of the bearing stress is closer to the edge of the base plate. This will increase the eccentricity that will be considered.

NOTE: For base plates designed according to the AISC 360, the uniform pressure distribution will be calculated according to the AISC Design Guide 1. The triangular pressure distribution will be calculated according to the AISC Design Guide 1, Appendix B (alternative method).

Consider Strain Compatibility

QUESTION: In RAM Connection, how does the strain compatibility affect the design of the base plate and anchors?

ANSWER: The strain compatibility will affect the calculations for the demand on the flexural yielding of the base plate.

Strain Compatibility NOT Considered: When strain compatibility is not considered, the analysis assumes that the maximum concrete compressive stress equals the code allowable concrete bearing capacity and then calculates the anchor forces to achieve equilibrium.

Strain Compatibility Considered: When strain compatibility is considered, the analysis assumes that the base plate is fully rigid, and the compression and tension strains are calculated assuming a linear relationship.

HINT: Enabling the strain compatibility may help RAM Connection find a base plate solution if a solution was not found using the regular method.

Concrete Bearing

QUESTION: In RAM Connection, how is the concrete bearing limit determined and which parameters will affect this design check?

ANSWER: The nominal bearing strength is determined according to the AISC 360 Section J8 (Equations J8-1 and J8-2):

The ratio of A2/A1 will be calculated using the dimensions of the base plate along with the dimensions of the footing or pedestal. The pedestal, footing, and grout parameters are entered into the Connection Pad after the initial base plate is assigned. (These parameters can be found in the Base Plate > Support folder in the Connection Pad.)

To modify the design to be more conservative, without modifying the support dimensions, the calculated A2/A1 area ratio for the bearing stress calculation can be overridden in the Connection Pad after the initial base plate is assigned. (The Override A2/A1 Ratio parameter can be found in the Base Plate > Base Plate folder in the Connection Pad.)

Connection Type (Stiffeners)

QUESTION: In RAM Connection, how do stiffeners effect the design of the base plate?

ANSWER: The demand on the flexural yielding at the tension interface (Mpt) of the base plate is calculated considering the tension at the anchors over an effective width (Beff). For large base plates, or base plates with significant tension on the anchors, stiffeners can help to reduce the controlling effective width:

Transferring Shear from the Column Base Plate to the Concrete Support

QUESTION: In RAM Connection, how is shear transferred from the column base plate to the concrete support?

ANSWER: In RAM Connection, shear can be transferred from the base plate to the support using one of the following methods:

Shear in the Anchor Rods (default method)
Friction between the Base Plate and the Grout/Concrete Surface
Use of a Shear Lug

The option to include the friction between the base plate and support can be selected in the Connection Pad. The friction shear capacity will then be calculated, and the anchor bolts will not transfer the shear from the base plate to the support.

The option to include a shear lug can be selected in the Connection Pad, along with the Shear Lug parameters. The capacity of the shear lug will then be calculated and the anchor bolts will not transfer the shear from the base plate to the support.

Grouting

QUESTION: In RAM Connection, can you include the grouting between the base plate and the concrete support?

ANSWER: Yes. You can choose to include grouting in the Connection Pad after the initial connection is assigned. This parameter will affect the shear capacity of the anchor bolts:

Cracked Concrete

QUESTION: In RAM Connection, is cracked concrete considered in the design of the anchor bolts?

ANSWER: Cracked concrete can be selected in the Connection Pad after the initial connection is assigned. The cracked concrete parameter will affect the modification factors as follows:

Breakout Cracking Factor (ψc,N): Effects the calculation for the breakout capacity of the anchor/group of anchors in tension. Effects the pryout capacity of the anchor/group of anchors in shear. Effects the capacity determined in the interaction of tensile and shear forces calculation.
Pullout Cracking Factor (ψc,P): Effects the calculation for the pullout capacity of the anchor/group of anchors in tension. Effects the capacity determined in the interaction of tensile and shear forces calculation.
Breakout Cracking Factor (ψc,V): Effects the calculation for the breakout capacity of the anchor/group of anchors in shear. Effects the capacity determined in the interaction of tensile and shear forces calculation.

Effective Length of Anchors

QUESTION: In RAM Connection, how is the effective length of the anchors calculated?

ANSWER: The total embedment length of the anchors is equal to the effective embedment depth plus the bolt/anchor head size. The effective embedment length is entered into the Connection Pad. The bolt/anchor head size is 0.65 x diameter of the bolt. The effective embedment length of the anchor bolts will affect the tensile breakout calculations, as seen in the figure below:

Anchors Welded to Base Plate

QUESTION: In RAM Connection, can you specify if the anchors are welded to the base plate?

ANSWER: Anchors welded to the base plate will be considered in the design if this option is selected in the connection pad. If this option is selected, the anchor/group of anchors that are farthest from the concrete edge will be considered as critical during the design in accordance with the ACI 318-19, Figure R17.7.2.1b.

RAM Connection Base Plate FAQ