Efficient design of high-strength hollow section K-joints

Lattice girders made of hollow sections are among the most common systems in steel building construction. The use of high-strength steels enables construction methods with lower material input and high load-bearing capacities. In order to exploit this potential for improvement in terms of competitiveness and resource efficiency, efficient design rules are required.
The design rules for connections with hollow sections have been semi-empirically validated by tests on normal-strength steels. These rules are based on the assumption that local stress peaks as a result of non-uniform stiffness distribution in the joint are reduced by plastic load redistribution and can thus be disregarded in the calculation. The question arises whether the local stress peaks have to be considered for high-strength steels, since their high yield strength and limited ductility allow only limited plasticity.
For K joints the reliability of the existing reduction factors should be determined by experimental and numerical investigations. In order to achieve this goal, large-scale joint tests are to be carried out and innovative damage-mechanical models are to be used which allow the numerical representation of material failure.
The research project is intended to derive design rules for hollow section joints with K shape, which refer to the individual failure modes, if necessary with an adaptation of the reduction factors for high-strength steels. Recommendations for practical application are to be developed which serve as a basis for a normative regulation in the building industry and enable an efficient design of welded hollow section joints with K shape made of high-strength steels. Thereby, economic as well as ecological advantages, e.g. cost and energy savings with low material input, will be developed for the SME-oriented steel construction industry and the quality-oriented steel industry.

University of Stuttgart
Institute of Structural Design
Prof. Dr.-Ing. Ulrike Kuhlmann, Wigand Knecht

RWTH Aachen University
Chair for Steel and Lightweight Metal Construction
Prof. Dr.-Ing. Markus Feldmann

FOSTA e.V. / AIF

01.10.2020