Stability
NSC 15
Technical Digest 2019
Conclusions
1 Eurocode 3 provides essentially 3 different methods to consider local and
global second order effects when verifying members;
2 In practice, local second order effects are usually considered when
checking member stability according to section 6.3 of EN 1993-1-1;
3 Local imperfections may need to be considered for global analysis; this
may be mandatory according to clause 5.3.2 (6) of EN 1993-1-1; the
criteria is more significant for frames with fixed bases where lower αcr can
be obtained with slender members;
4 The effective length method considers the effects of global second order
effects by increasing the local second order effects; buckling lengths
greater than 2l may be required;
5 The numerical consideration of global P-Δ effects and the approximated
consideration of those effects with the amplification factor give very
similar results; For member stability verifications according to section 6.3
of EN 1993-1-1, system lengths should be used;
6 The effective length method gives a reasonable answer in comparison
to the other two other methods where second order internal forces are
calculated. Differences between methods can be up to approximately
0.15 in the utilization factor (conservative or non-conservative);
differences are less significant for higher values of αcr.
7 The importance of considering more than 1 finite element per member
was demonstrated for struts and frames. At least 3 finite elements are
recommended;
8 Horizontal loads have a small influence in the values of αcr.
References
1 BS EN 1993-1-1+A1; Eurocode 3 - Design of steel structures - Part 1-1:
General rules and rules for buildings; BSI, 2014;
2 An approximate method for calculating the elastic critical load of multistorey
frames; M. R. Horn; The Structural Engineer, 53, 1975.
3 Eurocode 3 and the in-plane stability of portal frames; Lim, J.B.P., King,
C.M., Rathbone, A.J., Davies, J.M. and Edmondson, V.; The Structural
Engineer, Vol. 83, No. 21, November 2005.
4 NA to BS EN 1993-1-1+A1 ; UK National Annex to Eurocode 3 - Eurocode
3 - Design of steel structures - Part 1-1: General rules and rules for
buildings; BSI, 2014;
5 Stability and second order effects on steel structures: Part 1:
fundamental behaviour; R. Pimentel, New Steel Construction; Vol 27 No 3
March 2019.
6 Stability and Design of Structures (in Portuguese); A. Reis, D. Camotim;
Orion editions, 2012;
7 BS 5950-1; Structural use of steelwork in building: Part 1: Code of
practice for design - Rolled and welded sections; BSI, 2000;
8 Manual on Stability of Steel Structures; ECCS – European Conventional
for Constructional Steelwork, 1976;
9 Effective lengths of columns in multi-storey buildings; R. H. Wood; The
Structural Engineer, 52, 1974.
10 SN008a; NCCI: buckling lengths of columns: rigorous approach; M. Oppe,
C. Muller, D. Iles; London: Access Steel; 2005.
11 The effective length of columns in multi-storey frames; A. Webber, J. J.
Orr, P. Shepherd, K. Crothers; Engineering Structures 102 (2015) 132–143.
12 Structural steel design according to Eurocode 3 and AISC Specifications;
C. Bernuzzi, B. Cordova; Wiley Blackwell, 2016.
13 Autodesk Robot Structural Analysis 2019.
Visit www.SteelConstruction.info
All you need to know about Steel Construction
Everything construction professionals need to know to
optimise the design and construction of steel-framed
buildings and bridges can be easily accessed in one place
at www.SteelConstruction.info
This online encyclopedia is an invaluable fi rst stop for
steel construction information. Produced and maintained
by industry experts, detailed guidance is provided on
a wide range of key topics including sustainability and
cost as well as design and construction.
This is supported by some 250 freely downloadable PDF
documents and over 470 case studies of real projects.
The site also provides access to key resources including:
• The Green Books
• The Blue Book
• Eurocode design guides
• Advisory Desk Notes
• Steel section tables
• Steel design tools
Explore the full content of www.SteelConstruction.info
using the index of main articles in the quick links menu, or
alternatively use the powerful search facility.
/www.SteelConstruction.info
/www.SteelConstruction.info
/www.SteelConstruction.info