Verified by the CalcTree engineering team on August 8, 2024
This calculator designs a steel base plate for a steel I-section column in axial compression. It computes the required thickness and plan dimensions of a base plate.
Column and baseplate are symmetric and only subjected to an axial compressive force applied concentrically. Baseplate is a pin support.
Column load is distributed to the concrete foundation as a uniform bearing pressure.
The three "T-stubs" (two T-stubs under the column flanges and one T-stub under the column web) which are used for determining the effective bearing area, do not overlap.
Design of the welds or bolts is not included in this calculator.
The user can select from the following European & UK steel sections: UB (universal beams), UC (universal columns), IPE (parallel faced flange beams) or HE (wide/very wide flanged beams). The geometric properties of the cross-section are provided as per the standard: BS EN 10365:2017 - Hot rolled steel channels, I and H sections - Dimensions and masses.
Inputs
Base plate
Ned
:2 MN
ULS design compression load
fy
:275 MPa
Yield strength of the steel base plate
Concrete Support Properties
fck
:25 MPa
Compressive strength of the concrete support
alpha_cc
:0.85
Concrete coefficient for long-term effects (refer to your National Annex)
gamma_c
:1.50
Partial factor of safety for concrete (refer to your National Annex)
Steel Column Properties
Section
:UC - 203x203x60
h
:210mm
b
:206mm
tw
:9.4mm
tf
:14.2mm
r
:13mm
Perimeter
:1202mm
Area
:7686mm2
Outputs
fjd
:14.24 MPa
Bearing capacity of concrete support
A_req
:140,474 mm2
Required minimum base plate area
c
:86 mm
Additional bearing width
wp
:378 mm
Required minimum base plate width
lp
:382 mm
Required minimum base plate length
tp
:34 mm
Required minimum thickness of base plate
Output parameters of a base plate with an I-section
Is the calculator valid, that is, do the T-stubs overlap?
Check
:OK, there is no overlap between T-stubs.
Explanation
Steel base plates are provided beneath steel columns in order to transmit the applied design forces safely to the foundations. Since steel columns are heavily loaded and their cross-sections are typically small, applying the loads directly on the foundation could result in a punching failure. Therefore a base plate must be provided beneath the column in order to spread the column load over a larger base area.
The actual distribution of pressure beneath a base plate is quite complex. EN 1993-1-8:2005 clause 6.2.5 and 6.2.8 presents a simplified approach. It assumes a uniform distribution of pressure beneath an effective area of the base plate known as the "equivalent T-stub in compression". The dimension,
c
in the figure below known as the "additional bearing width", forms an effective bearing area given by
Ieff
and
beff
. The required check is that the applied compressive stress on this effective area does not exceed the design bearing strength of the joint,
fjd
.
Area of equivalent T-stub in compression, adapted from Figure 6.4 EN 1993-1-8
As per Clause 6.2.8.2, the capacity of a symmetric column base plate subject to an axial compressive force applied concentrically may be determined by adding together the capacities of the three T-stubs shown below (two T-stubs under the column flanges and one T-stub under the column web). The three T-stubs should not be overlapping.
Effective bearing area of a base plate with I-section, adapted from Figure 6.19 EN 1993-1-8