P 1163 – Economical design of fatigue-stressed, welded circular hollow section nodes taking into account the required weld quality
Fatigue loaded, welded joints of circular hollow sections have a great economic potential in structural, mechanical and plant engineering. Connections of welded hollow sections as uniplanar K-joints or multiplanar K- and KK-joints respectively are particularly common, which are therefore subject of this research project. More recently, thick-walled hollow section joints have incresingly been realized, but still without any officially accepted standardization rules of building and bridge authorities. Especially for the fatigue design, which often has to be conducted on the basis of the structural stress approach, none exist so far.
The aim of this research project was therefore the development of a DASt–Guideline complying with the European standards, based among others on the results of the earlier project P815. For this purpose a fatigue assessment procedure, taking into account the scale effect and covering also thick-walled hollow sections, has been developed on the basis of previous and new tests, carried out in this research project, by means of statistical analyses and systematic numerical investigations, including the definition of the application range. Two additional important aspects of the planned investigations were the extension of the scope of application to large-sized hollow sections d0 > 500 mm and the development of practiceoriented recommendations for the fabrication and quality assurance of an optimal weld seam geometry. By experimental investigations on large-sized hollow section joints (chord-dimensions 660 mm×60 mm) the existing application range could be expanded to formats needed especially in bridge construction and in the offshore industry. By means of 27 component-type tests on welded K-joints of circular hollow sections with specified weld root opening size and weld shape the effects of weld irregularities and weld shape could be quantified. In the near future contracting companies can be provided with an assurance for an economic design of welds with the help of the proposal for a DASt–guideline. Weld irregularities, which do not exceed a certain value and otherwise had to be repaired in a time-consuming manner can remain inside the hollow section joint.
These studies were accompanied by systematic ultrasonic tests with the phased array technique in which also the inspection method for these complex weld geometries has been developed and validated. For small and medium-sized enterprises of the steel construction industry i.e. for bridge, crane and building constructions as well as for offshore-projects or wind turbines an opportunity is provided for an economical manufacture. Furthermore this standard complying solution allows engineers of consultancies to avoid expensive special-purpose solutions like joints with stiffeners.
Prof. Dr.-Ing. U. Kuhlmann, S. Bove, M. Sc, Prof. Dr.-Ing. A. Dürr, Dr. rer. nat. R. Steinhausen, Dr. rer. nat. Ch. Pientschke, Dr. rer. nat. M. Kiel