Shear Lugs A model to analyse Fastenings with shear lugs

Ein Modell zur Berechnung von Einbauteilen mit Schubdbeln

To be awarded with the academic grade of a Doktor-Ingenieur by the Faculty of Civil Engineering of the Dresden University of Technology (Technische Universitt Dresden) approved Doctoral Thesis submitted by Dipl.-Ing. Harald Michler
Born on 24.02.1964 in Tbingen

Assessment: Univ.-Prof. Dr.-Ing. Manfred Curbach o.Univ.-Prof. Dipl.-Ing. Dr. techn. Dr. phil. Konrad Bergmeister Univ.-Prof. Dr.-Ing. Jrgen Schnell Submission: 24.5.2006 Day of the oral examination: 15.12.2006 Dresden, 2006

Abstract
An experimental and theoretical analysis of the behaviour of complex shear loaded fastenings was carried out at Dresden University of Technology. The main focus was on applications which introduce a great amount of shear load value parallel to the surface into a concrete base using a stell shear lug. The behaviour of these special fixings is presented as the result of the finished research program. Structures, as shown in the opposite V figure, are able to transmit high values of shear loads to the anchor ground. An additional loading baseplate of normal force und bending moment is suitable, shear lug cross but will only be supposed to cover the necessary section headed anchor bolt tolerance and off centre condition of the fixture as tie bar parts. The advantage of fastening with shear lugs concrete ground is based on the splitting of the load transfer into different components. The shear lug/lugs caries/carry the shear load, and the tie bar itself only balances the system by tension load due to moment loading and normal loading. Thusall loads are transferred by highly specialized components. If the base plate is embedded, there will be a shear load transferred in front of the base plate, too.
N M fixture

The load carrying behaviour of the fastenings in the experiments is analyzed. Here, the load-displacement relationship is of special importance . This thesis aims at elaborating a dimensioning concept for the design of shear lugs. The tests show a decisive influence of the movements displacements as well as rotations of the fastenings to the load carrying capacity. In order to to be able to examine this behaviour, the experiment is redesigned by finite elements. In a first step it is therefore possible to examine fastenings without movements based on the anchor bolt stiffness. In a second step, the influence of the deformation can be explored. Here, the parameters can be varied more exactly and in a more complex way than this is possible in terms of quantity with the comparetively extensive test setup. The calculation method being introduced here does not only supply the maximum shear load transfer capacity of the hole fastening system, a system with free geometries, but also shows the partial shear load transfer capacity of the individual parts of the unit. This method is a means of predicting the load-related behaviour of the fastenings to be expected, including the forecast of partial failure states. As a result, a suggestion for the design of the fittings is shown. This design can be applied to all fittings by splitting the different load components to especially provided anchor elements. The design resistance and behaviour of the fastenings is estimated, depending on different geometries and stiffness conditions of the lug. Different strength classes of the concrete as well as different load combinations are taken into consideration. First examples from building sites are also available.

Theses
Fastenings with shear lugs are powerful, but they are rarely used at present. Mainly fastenings with a comparatively small shear load capacity are standardised , especially anchors or head anchor bolts. Until now, fastenings with shear lugs have been designed only on aconstructive and rough basis. Undeformed block dowels or lugs are used and deformation of them is not considered. Twisting, displacement or deforming, of the fastenings against the anchor ground are not taken into consideration as well. Fastenings with shear lugs have a high shear load transmission capacity, because the load is divided into specialized components. The transmission of the surface-parallel shear load is totally separated from the balancing system. In fastening systems with shear lugs the components are subjected to loads appropriate to the material used. The concrete stress field loaded by the shear load demand is equally stressed and can be shown to be in hydrostatic stress state, due to specific circumstances. The centre of the shear load transmission in front of the shear lug depends on the displacement status of the whole fastening. In the case of a complex fastening with shear lugs, several load transfer mechanisms may occur in combination. These can be computed, however, separately. The main and basic load transfer mechanism is always the load transfer in front of the shear lug The load transfer in front of the base plate is a further transfer mechanism in most cases, if the base plate is embedded into the concrete. However, there may be more than one shear lug used in a single fastening. A complete decoupling of the load transfer mechanisms for shear force transfer is possible. The combination of the load transfer mechanisms and their qualities determine, however, the kind of failure of the fastening. The shown calculation method enables the evaluation as to what extent the individual load transfer mechanisms will work additively or alternatively. Fastenings with shear lugs will make the design of an economical and safe surface-parallel load transfer possible . The shown calculation method enables to use the entire load carrying capacity of fastenings with shear lugs safely and can therefore increase the attractiveness of these components for their application.