Base Plates
All base plates are sized to consider the bearing capacity of the member that supports the base plate. This member could be a foundation, a concrete column or a wall. Base plates are not designed where they are supported by a transfer beam. The support area at the foundation level is taken according to the criteria provided by the user. Where supported on a column or a wall the orientation of the support relative to the base plate and the support dimensions themselves form the extents of the supporting area.
Base plates oriented at an angle different than the support angle will have an effective support area defined as illustrated below.
The initial plate size (a, b) is calculated based on the supported steel column dimensions and the user specified minimum dimensions from column side to edge of plate. The maximum base plate size that can fit on the support is then calculated as a rectangle of equivalent proportions to initial plate size (c, d). This area (c, d) is defined as the supporting area for bearing capacity determination.
AISC 360 (ASD and LRFD)
Base plate for AISC 360 is based on the procedures outlined in the AISC 360 Manual of Steel Construction. The Φc and Ωc values for the bearing strength are different between AISC 360-05 and newer versions of AISC 360, so there will likely be differences in designs between the two specifications.
For base plates on small support areas, the allowable bearing strength is based on the "area of the supporting surface that is geometrically similar to and concentric with the loaded area" as required by Code.
For rectangular and round sections, the interior stresses are not checked.
ASD 9th and LRFD 3rd
Except as outlined below, base plate design for ASD and LRFD is based on the procedures outlined in the respective AISC Manual of Steel Construction. For the ASD 9th Edition, the revised method printed in the January 1991 printing is used. For LRFD, the methodology outlined in the 2nd Edition is used.
For ASD, the allowable concrete bearing strength is based on ACI 318 89 ultimate strength.
For base plates on small support areas, the allowable bearing strength is based on the "area of the supporting surface that is geometrically similar to and concentric with the loaded area" as required by Code.
For rectangular and round sections, the interior stresses are not checked.
Eurocode
Base plate design for the Eurocode is based on BS EN 1993-1-8:2005 section 6.2.5.
The critical moment location for the base plate is taken to be at the centerline of the flange. That is, the moment arm is taken as the c distance plus one-half of the flange thickness.
For columns consisting of round and rectangular hollow sections, the bearing area is determined by calculating the value for c and then calculating the associated area, analogous to the method described for I-shaped columns.
γMO and Υc are specified in the command of RAM Manager.
CAN/CSA-S16-01/ S16-09 / S16-14
Base plate design for CAN/CSA-S16-01 is based on the methodology given in Part Four of the CISC Handbook of Steel Construction, Eighth Edition. Base plate design for CAN/CSA-S16-09 is based on the methodology given in Part Four of the CISC Handbook of Steel Construction, Tenth Edition. Base plate design for CAN/CSA-S16-14 is based on the methodology given in Part Four of the CISC Handbook of Steel Construction, Eleventh Edition. For lightly loaded base plates, the methodology based on the Fling reference as described therein is utilized.
The factored bearing resistance of concrete is based on Clause 10.8.1 of CAN/CSA-A23.3-94.
For Rectangular and Round Hollows Sections the critical moment location for the base plate is taken to be at the centerline of the column flange. The moment in the plate that occurs within the hollow section is not checked.
The plate design Fy is based on the Grade and plate thickness.