AS 4100. Example 5: Design a Universal Column Compression Member

This benchmark was prepared based on
Australian Steel Institute (ASI) Steel Structures – Sample Worked Problems to AS 4100
using
SDC for Femap and Simcenter Femap Version 2022.2

This benchmark guides you through the design of a universal column compression member in accordance with AS 4100. From preliminary calculations and FEA model setup (including software limitations) to SDC Verifier 2024 R1 analysis, you’ll learn how to confidently validate your design choices.

In the first part of the example some assumptions and preliminary calculations are made to choose a potential beam to fit the design requirements.

Based on the above the following Characteristic was defined:

Based on the input parameters presented above a beam model was created with the following material and property definitions:

Note: Because of the limitations of the FEA software the cross-section is defined without fillets, so slight differences in geometrical properties are to be expected.

Where possible these values have been modified manually (as for the moments of inertia and , torsion constant and warping constant in the table above), but some are calculated internally without the possibility to modify them (e.g. plastic section modulus).

Loads and constraints have been defined according to the problem definition:

The loads are multiplied by the according factors using the SDC Verifier Load Set creator:

The above parameter is checked within a Property Check, in this case one defined for I-Beam cross-sections.

As we can see the form factor value matches completely.

The effective lengths for each axis can be adjusted in the Beam Member Finder by modifying the according length factors:

SDC Verifier automatically picks the controlling axis for buckling when calculating the member slenderness values.

We can see that the value of the member slenderness is matching with the example calculations.

The compression member section constant a_b was already defined as a characteristic based on the according table and the member slenderness reduction factor a_c is calculated automatically through the procedure that doesn’t require input from tables:

Which results in an almost identical value as when using the linear interpolation based on Table 6.3.3(3) in the example.

When calculating the nominal member capacity in compression (N_c) SDC Verifier follows the logic of the standard, so the multiplication by the capacity factor ф happens later when comparing it to the design axial compression force.

That’s why the value obtained in the table has to be additionally reduced by ф for the purposes of the calculations in this example:

𝜙∗𝑁_𝑐=0.9∗2920921 𝑁=𝟐𝟔𝟐𝟗 𝒌𝑵

As we can see the obtained value is slightly lower than in the example, but that is due to the member slenderness reduction factor also being slightly lower, because of the manual way of obtaining that value from the table in the example.

Whether the chosen section is satisfactory is confirmed in SDC Verifier by obtaining a utilization factor (Uf) with a value below 1, which is additionally indicated by the green highlight in the table above.

AS 4100 Column Design Confidence with SDC Verifier

Despite slight deviations due to FEA software limitations, this benchmark highlights how SDC Verifier aligns with AS 4100 principles for compression member capacity calculations. Gain greater assurance in your column designs by understanding these nuances.

This post uses screenshots from the Steel Structures Sample Worked Problems to AS 4100 document