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Benchmark 40: Access Steel Document SX024a-EN-EU
Project file: Benchmark_(EC_EN_1993)_40.esa
SCIA Engineer Version R18.1
Introduction
This benchmark concerns the example SX024a-EN-EU Design of a cold-formed steel lipped channel wall stud in compression of Access Steel, http://www.access-steel.com/, 2006.
This example deals with the design of a pinned wall stud subjected to compression. The stud is composed of a cold-formed lipped channel section where boards are attached to both flanges and they prevent buckling in the weak direction and torsional buckling.
Reference Results
The reference gives following results:
|
Effective section properties
|
| Aeff |
118 mm² |
| Weff,z,com |
1274 mm^3 |
| Weff,z,ten |
2585 mm^3 |
|
Combined compression and bending
|
| eN,z |
3,04 mm |
| Nc,Rd |
41,3 kN |
| Mcz,Rd,com |
0,45 kNm |
| ΔMz,Ed |
0,077 kNm |
| UC |
0,785 |
SCIA Engineer Results
Comments
- The reference does not detail the calculation of the effective section properties. The compression force causes a shift in neutral axis towards the edge folds. This implies that the compression load, acting at the centroid of the gross section, causes a weak axis moment which gives compression in the web and tension in the edge folds. The effective shape for this negative weak axis moment leads to only a reduction of the web and causes the centroid to shift just to the left of the middle of the flanges. As a result, the section modulus at the compression (web) side Weff,z,com is slightly bigger than the section modulus at the tension (edge fold) side Weff,z,ten.
The reference however has the inverse i.e. a big modulus at the tension side compared to a small modulus at the compression side. This seems to correspond to a positive weak axis moment which causes tension in the web and compression in the edge folds. For this effective shape there is practically no reduction so the centroid nearly stays at its original location. This causes a big section modulus at the tension (web) side Weff,z,ten and a small section modulus at the compression (edge fold) side Weff,z,com.
=>The reference seems to be applying an incorrect sign/direction of the weak axis bending moment, causing incorrect effective section moduli values.
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