Abstract

The usage of hollow profiles offers constructive and manufacturing advantages in metal construction. Because of the current standardization (Eurocode 3) in this area in the European Union, it is reasonable to regulate the usage of such profiles made of high strength steels (e.g. S690) by building law (prEN 1993-1-12 “Erweiterung auf Stahlgüte bis S700”), like it is done for other cross-sectional shapes. The missing design rules and –standards are the main reason for the poor and accordingly depressed usage of high strength steels, which are almost exclusively produced by Western European and German manufacturers.

The specific problem with framework constructions made of hollow profiles especially consists of calculation and design of welded connections. The structural behavior of hollow profile joints is characterized by the deformation behavior and load distribution in the connection area. Stress redistributions result with increasing load, which make a clear analytical capture impossible.
 
For being able to use the existing tables of carrying capacities according to DIN EN 1993-1-8 for steels with elastic limits of more than 500 N/mm², it is planned to introduce a reduction factor for the carrying capacity of 0,8 in the concept of prEN 1993-1-12. Though, in this concept it is explicitly mentioned, that this factor is to be proved experimentally. An equivalent reduction factor for S690 of 0,9 has already been introduced in DIN EN 1993-1-8. This factor is to be checked, and if necessary, changed within the scope of this project.
 
First preliminary analogy observations of hollow profile joints made of S460/S690 and of S235/S355 show, that due to the complicated geometry depending carrying mechanism, a simple adjustment, that is exclusively based on the influence of the elastic limit cannot be generated. As a basic principle, first experiments on hollow profile joints showed, that higher degrees of utilization are created than such made of S235 and S355.
 
Within the planned experimental and theoretical examinations the reduction factors shall be checked and, if necessary reduced or even abolished completely. Possibly a catenation of the reduction factors with the joint’s geometrical parameters will be necessary. By abolishing or reducing the reduction factors, a cost-effective usage of hollow profiles made of high strength steels will be possible.
 
The results will be processed conforming to standards and shall be integrated directly in/to the according standards. This is guaranteed by the submitters’ memberships in the according international boards/bodies. To ensure a praxis-oriented proceeding, it is proposed to integrate representatives of reputable steel construction companies.