Design and execution of joints with lock-bolts for steel structures. A large number of mechanical joints for steel structures is generated with conventional bolts. Still, this proven joining technology has some significant disadvantages. These include the big scattering of inserting the preload using the torque-tightening method, the risk of self-loosening by cyclic loads causing a cross movement of the components as well as the low fatigue resistance for axial loads. The lock-bolt technology was already invented in the 1930s and mainly used for the aviation and space industry in support of its evident advantages. Due to demands from different industrial markets, like aviation, truck, trailer, rail, bus, agriculture, mining, military and steel construction industry, the lock-bolt technology was further developed and applied. Its application, particularly in the mechanical engineering sector, was mainly possible due to individual investigations performed by the users of the technology. These investigations were costly but necessary due to the lack of consistent design rules, which hindered a broader implementation and the calculation of lock-bolt connections in the construction and building industry. Within the scope of several research projects funded by the AiF (German Federation of Industrial Research Associations) the Fraunhofer-Application Center for Large Structures in Production Engineering successively developed calculation rules, which will be introduced to the reader within the scope of this paper with the aim to utilise the advantages of this joining technique. Furthermore, the applicability in the building industry with general technical approvals will be exemplified and current applications demonstrated

Die Blindniettechnik gilt als ein sehr schnelles und prozesssicheres Fügeverfahren. Blindniete werden überall dort eingesetzt, wo klassische Fügeverfahren, wie bspw. das Schweißen oder Schrauben, technologisch oder konstruktiv bedingt nicht eingesetzt werden können oder unwirtschaftlich sind. Zu den klassischen Anwendungsgebieten im Stahlleichtbau gehören die Befestigungen von Dach‐ und Wandverkleidungen. Darüber hinaus werden weitere Anwendungsfelder wie z. B. Hochregallager und Wohncontainer von der Blindniettechnik erobert. Leider bestehen seitens der Ausführung und Bemessung von Verbindungen mit Blindnieten im Stahlleichtbau für zuvor genannte Konstruktionen einige Hürden, sodass bislang immer auf einen bauaufsichtlichen Verwendbarkeitsnachweis zurückgegriffen werden muss. Dieser kann meist nur durch zeit‐ und kostenintensive Einzelfalluntersuchungen erlangt werden. Darüber hinaus ist die bestehende normative Regelung durch DIN EN 1993‐1‐3 sowie DIN EN 1090‐4 nach Meinung der Verfasser unzureichend, was einem breiteren Einsatz der Blindniettechnik momentan noch entgegensteht. In diesem Beitrag werden die Ergebnisse aus systematischen Untersuchungen zur Abscher‐ und Lochleibungstragfähigkeit von Blindnieten und den damit hergestellten Verbindungen vorgestellt. Ziel der Untersuchungen war die Überprüfung und Erweiterung der im EC 3 bestehenden Bemessungs‐ und Ausführungsregeln für Blindnietverbindungen, um zukünftig einen rein rechnerischen Nachweis der DIN EN 1993‐1‐3 für querkraftbeanspruchte Blindnietverbindungen zu erlauben und somit den erforderlichen Aufwand für eine versuchsgestützte Bemessung zu reduzieren.

Many mechanical joints in steel structures use conventional bolts. Nevertheless, this proven joining technology has some significant disadvantages. These basically include the high levels of scatter during application of the assembly preload using the torque‐controlled tightening process, the risk of loosening during cyclic loads due to transverse displacement of the components and the low fatigue resistance under axial loading. Lockbolt technology was invented as long ago as the 1930s and mainly used for the aviation and space industry because of its evident advantages. This joining technology has been constantly further developed in response to the most diverse demands from sectors such as aviation, commercial vehicles, rail vehicles, agricultural machinery, defence technology and steel structures. The application of lockbolt technology, which is primarily used in mechanical engineering, was in most cases based on individual studies, since no consistent rules and guidelines were available for the design and execution of lockbolt connections in steel structures. Within the scope of several public research projects funded by the AiF (German Federation of Industrial Research Associations) and conducted by the iGF (Industrial Collective Research) organization as well as through approval investigations, the Fraunhofer Institute for Large Structures in Production Engineering (IGP) has successively developed the necessary design rules according to the EN 1993 standard (Eurocode 3) for use in structural connections. These design rules will be presented within the context of this article in order to make the benefits of this joining technology available to other users. In addition, insights into the use of technical approvals will be presented together with some current applications.

Construction is not possible without joining single parts to components and at the end to the final structure. There exist multifarious kinds of connections whose suitability mainly depends on the characteristic of raw material the structural parts are made of. This article especially deals with joints in metallic light weight structures. Beside the typical connections in metal structures like welding, bolting and riveting in metallic light weight structures further kinds of connections can be found like standing seam, clinch, punch rivet or cartridge fired pin connections. Describing all these single methods would go beyond the scope of this article. That is why only the predominant part of all connections with so called pencil-shaped fastening elements like screwed connections, blind riveted connections and connections with cartridge fired pins will be dealt with. Furthermore the scope of application will be shown, advantages and disadvantages will be compared, the determination of characteristic values or resistance will be shortly explained and advices for calculation and execution will be given

Many mechanical joints in steel structures use conventional bolts. Nevertheless, this proven jointing technology has some significant disadvantages. These basically include the high levels of scatter during application of the assembly preload using the torque-controlled tightening process, the risk of loosening during cyclic loads due to transverse displacement of the components and the low fatigue resistance under axial loading. Lockbolt technology was invented as long ago as the 1930s and mainly used for the aviation and space industry because of its evident advantages. This jointing technology has been constantly further developed in response to the most diverse demands from sectors such as aviation, commercial vehicles, rail vehicles, agricultural machinery, defence technology and steel structures. The application of lockbolt technology, which is primarily used in mechanical engineering, was in most cases based on individual studies, since no consistent rules and guidelines were available for the design and execution of lockbolt connections in steel structures. Within the scope of several public research projects funded by the AiF (German Federation of Industrial Research Associations) and conducted by the iGF (Industrial Collective Research) organization as well as through approval investigations, the Fraunhofer Institute for Large Structures in Production Engineering (IGP) has successively developed the necessary design rules according to the EN 1993 standard (Eurocode 3) for use in structural connections. This paper presents connections with lockbolts in steel structures. Following an introduction to lockbolt technology and the assembly preload of lockbolts, the securing effect and corrosion protection of lockbolts are presented.