Erhöhung der Tragfähigkeit von GV‐Verbindungen durch den Einsatz von Klebstoff

Use of adhesives to increase the load‐bearing capacity of slip‐resistant connections. Slip‐resistant connections are preferred for steel constructions if subjected to fatigue loads and/or load reversals, no slip in the connection is permitted and joining on construction site is necessary. These connections are prepared with a high manufacturing effort due to the intensive preparation of the faying surfaces, or the contact area between the steel plies and it must receive special consideration in design and coating application. The typical corrosion protection for steel structures is still the hot‐dip galvanizing. The follow‐up work of the faying surfaces for a use in slip‐resistant connections is related to a high effort and guarantees no high slip factors. Furthermore the slip factor may deviate more or less high with the properties of the zinc layer. Against this background, investigations have been carried out in a recently concluded research project which show an increase in the load bearing capacity of slip‐resistant connections by the combined use of adhesive. In the case of the process combination, which is also referred and named as a preloaded hybrid connection, the applied preload of the high‐strength bolts is responsible for the considerable increase in load bearing capacity compared to the elementary joining processes – adhesive bonding or just slip‐resistant connections. If the two methods are carefully combined, the individual load bearing capacities can approximately add up.     

Einfluss der Wanddicke auf das Ermüdungsverhalten von geschweißten X‐Knoten aus Rundhohlprofilen

Influence of wall thickness on the fatigue behaviour of welded X‐joints of circular hollow sections. The current version of EN 1993‐1‐9 stipulates different notch classes for the design of fatigue loaded constructions based on the nominal stress concept. Annex B of EN 1993‐1‐9 also outlines the design referring to the structure stress concept, but includes no specifications for the evaluation of the structural stresses (e. g. extrapolation path) nor detailed classification for specific fatigue loaded hollow sections. More extensive specifications for the application of the structure stress concept with detailed calculation formulas graphs and extrapolation points are given in CIDECT‐Design Guide No. 8, for example. For the design of such welded steel constructions for fatigue, there are different methods, that can be applied. In order to handle the size effect, different recommendations can be found in literature to reduce the predicted fatigue life of plates and tubes with increased thickness. For example in the current DIN EN 1993‐1‐9 wall thickness correction factor for plates exceeding t > t₀ = 25mm is given, i. e.: S_R = S_R,D (t_o/t)^0,25. For welded hollow sections, DIN EN 1993‐1‐9 limits the range of validity to wall thicknesses t ≤ 8mm and 12,5mm respectively and the diameters of circular hollow sections to d ≤ 300mm and to edge length of rectangular hollow section b ≤ 200mm. In the scope of the FOSTA research project P 801, the Labor für Stahl‐ und Leichtmetallbau of the University of Applied Sciences Munich, conducted investigations on different notch cases of welded hollow sections with the outcome of assessing the influence parameters of welded hollow sections.     

Verfahrensprüfung zur Bestimmung von Anziehparametern für vorgespannte geschraubte Verbindungen

Procedure qualification for the determination of tightening parameters for preloaded bolted connections. DIN EN 1090‐2 and DIN EN 1993‐1‐8/NA define tightening procedures for preloaded bolted assemblies tightened at the nut side by simple use thereof. However, in a multitude of applications, preloaded bolted connections are used, which for example are tightened on the head side, designed as tapped hole connections and/or are to be used several times. In these cases, a procedure test is necessary to determine the tightening parameters. The present paper describes the principal procedure for carrying out such a procedure test, in particular the target level of preloading, the length of thread engagement for components with internal threads, the single and multiple use of components, and the boundary criteria for determining the tightening parameters. Furthermore, the procedure is explained using practical examples.