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Dezi et. al (2010)
🤾
Projectile motion
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.
📝 This calculator has been written in accordance with BS-EN-1993-1-8:2005 Eurocode 3: Design of steel structures - Part 1-8: Design of joints, which is part of the "EC3" or "Eurocode 3" code series.
Calculation
📝Technical assumptions
Inputs
Base plate
Ned
:5,000kNULS design compression load
fy
:275MPaYield strength of the steel base plate
Concrete Support Properties
fck
:25MPaCompressive strength of the concrete support
αcc
:0.85Concrete coefficient for long-term effects (refer to your National Annex)
γc
:1.50Partial factor of safety for concrete (refer to your National Annex)
Steel Column Properties
Section
:IPE - 100
h
:100mm
b
:55mm
tw
:4.1mm
tf
:5.7mm
r
:7mm
Perimeter
:400mm
Area
:1032mm2
Outputs
fjd
:14.24MPaBearing capacity of concrete support
Areq
:351,185mm2Required minimum base plate area
c
:250.1mmAdditional bearing width
wp
:555.1mmRequired minimum base plate width
lp
:600.1mmRequired minimum base plate length
tp
:98.6mmRequired minimum thickness of base plate
Is the calculator valid, that is, do the T-stubs overlap?
Check
:Overlap between T-stubs, calculator not valid. Decrease Ned or increase column size.
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,
in the figure below known as the "additional bearing width", forms an effective bearing area given by
and
. The required check is that the applied compressive stress on this effective area does not exceed the design bearing strength of the joint,
.
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.
The steps for this "equivalent T-stub in compression" design method are based on a research paper from the University of Ahmadu Bello, and are as follows:
1) Compute the bearing strength, of the concrete support
2) Find the required area of the base plate,
3) Find the additional bearing width,
4) Find the required base plate plan dimensions
5) Calculate the required base plate thickness,
Acknowledgements
This calculation was built in collaboration with Kamaludeen Samaila. Learn more.
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