Tragfähigkeit von Lochleibungsverbindungen vorgespannter Glasscheiben zur Ausbildung von Anschlüssen im Konstruktiven Glasbau

Strength of bearing connections in toughened glass plates for the structural use. In steel structures due to their “infinite'” ductility the bearing connections are standard components of joints. Their design rules are based on simple engineering models. However if analogous bearing connections are subject of glazing structures the requirements on the materials' ductility cannot be met. Therefore interlayers out of mortar etc. in the hole surrounding the bolt have to be introduced such that a ductile load deformation behaviour can be reached reducing stress peaks and avoiding steel‐glass‐contact. On this basis design rules are to be established to predict the load carrying capacity of bolts in glass bearings. The following investigations describe the experimental and theoretical works to derive an engineering model for this purpose.     

Probabilistische Bemessung von geklebten Anschlüssen im Holzbau

Kleben von tragenden Bauteilen ist im Holzbau auf wenige Anwendungsgebiete beschränkt. Es wird hauptsächlich zur Herstellung von Brettschichtholz oder zur Ertüchtigung bestehender Strukturen eingesetzt. Um Kleben als Alternative zu stiftförmigen mechanischen Verbindungsmitteln einzusetzen, muss die Bemessung geklebter Anschlüsse ermöglicht werden. Holzspezifische Faktoren wie Anisotropie, Streuung der mechanischen Eigenschaften und sprödes Versagen erschweren eine genaue Vorhersage. Aufgrund der auftretenden Spannungsspitzen ist ein deterministischer Spannungsnachweis nicht geeignet. Eine Alternative zur Bestimmung der Tragfähigkeit geklebter Anschlüsse bietet die in diesem Beitrag vorgestellte probabilis tische Methode, die es erlaubt, die Spannungsverteilungen in geklebten Verbindungen mit ihren Spannungsspitzen und die Streuungen der Festigkeitswerte des Werkstoffes zu erfassen. Im Rahmen der vorgestellten Arbeit wurden geklebte Doppel‐Laschenanschlüsse sowohl experimentell als auch numerisch betrachtet, wobei der Einfluss der überlappungslänge, der Klebschichtdicke und des Klebstoff‐E‐Moduls betrachtet wurde. Im Anschluss wurde ein probabilistisches Bemessungsverfahren angewendet und eine gute übereinstimmung zwischen experimentellen und theoretischen Traglasten erreicht. Das Verfahren kann unmittelbar für die Bemessung geklebter Anschlüsse angewandt werden. Probabilistic design of adhesively bonded timber joints. The use of adhesive bonding in structural timber engineering is limited to the production of laminated wood and the toughening of existing structures. To use adhesives as an alternative to mechanical fasteners, an accurate and reliable design method has to be developed. Characteristic material properties of wood such as anisotropy, large scattering of mechanical values and brittle failure complicate the capacity prediction of bonded joints. A deterministic approach is not able to deal with the stress peaks inside the joints. With the probabilistic concept, an alter native solution is presented, which allows for a strength prediction under consideration of the complex stress distributions and the stress peaks in the joint, as well as the scatterings of the mechanical properties of the material. Adhesively bonded double lap joints were investigated both experimentally and numerically under consideration of various parameters such as overlap length, adhesive layer thickness and type of adhesive. The probabilistic design method was applied and good agreement between experimental and theoretical failure loads was obtained. The proposed method has immediate actionable application for the dimensioning of adhesively bonded timber joints.     

Untersuchungen zu Herstellungs‐ und Instandhaltungs kosten von unterschiedlichen Konzepten zur Sicherstellung der Dauerhaftigkeit von Parkbauten

Research of production and maintenance costs for alternative concepts to ensure the durability of parking buildings There is currently an intense discussion about how to ensure the durability of parking buildings. Without having carried out a comprehensive cost analysis for the alternatives for durability concepts costs are nevertheless used as an argument for or against a certain execution. In this publication the costs of various execution concepts are compared on the basis of a virtual two‐storey underground garage with standard dimensions for the two major components of ”suspended ceiling“ and ”baseplate“. For instance the cost analysis includes the production costs for the minimum reinforcement in dependence of the examined surface protection or of the waterproofing system respectively. Furthermore the costs for maintenance, inspection and repair among other aspects are compared in dependence of the surface protecting system for a service life of 50 years. This cost approach takes into account consists of market fluctuations as well as scheduled maintenance cycles by considering medium, minimum and maximum costs. For the suspended ceiling the following coating or waterproofing systems respectively are examined: surface protection system ”OS 11“; ”mastic asphalt (single/double layer) with asphalt sheeting ”; ”mastic asphalt (single/double layer) with surface protection systems OS 10“ and ”PMMA“ protecting surface system. For the base plate two load cases are investigated: ”water exchange zone“ (WW) and ”water pressure“ (WD) in combination with the following surface protection systems: ”OS 11“, ”mastic asphalt (single/double layer) with asphalt sheeting“ and ”OS 8 with accompanying crack treatment“. For the ongoing maintenance costs, engineering values are chosen in accordance to the current state of knowledge. It is expected that current research projects are going to provide scientific results in the near future allowing an update of this cost analysis.     

FE‐Untersuchungen zur Interaktion von Biegedrillknicken und plastischem Querschnittsversagen bei Durchlaufträgern

Finite element analysis of the interaction between lateral torsional buckling and cross‐section yielding of continuous beams. Continuous beams can be regarded as economically designed, if lateral torsional buckling and yielding occur simultaneously. In order to predict the exact failure mechanism and to adopt necessary measures, the various interactions can be examined by means of the finite element method. Another advantage of FE analysis is that asymmetrical crosssections, beams with web stiffeners or openings as well as arbitrary supports can be examined. Goal of this paper is to point out which aspects have to be considered when developing a suitable computational model, beginning with the FE discretization and the choice of the time step up to the introduction of imperfections. Further, guidelines for the interpretation of FE results, e.g. of load displacement curves, are provided.     

Die Auswirkung von duktilen Anschlüssen auf die Explosionsresistenz lasttragender Stützen

Effect of ductile connections on blast resistant load bearing columns. Load bearing columns exist in most constructions and are applied for instance as floor columns or as bridge piers. The study performed here addresses the question how the load‐bearing column behaves under blast load and which constructive measures result in an enhanced resistance against the blast pressure wave. Simple single‐cell steel cross section set‐up is changed stepwise by implementation of multi steel cells or by filling the hollow steel section with concrete. In doing so, the column is not generated as an isolated member, but installed in a flexible neighboring system, which allows taking the connection ductility into account. The response behavior of representative steel and composite column types is investigated, the section is searched for local overstresses and the failure mechanisms of the structural member are defined. The evolution of the cross section set‐up and the corresponding changes in the simulation results enable the formulation of decisive parameters which contribute to the enhancement of member blast resistance. The study pursues the specific local resistance design approach and aims at developing constructive protection technology in order to avoid the detected local damages. The column base appears to be the vulnerable section at the column rigidly or less flexible connected to the ground. The strategic use of ductile bearing condition is applied to reduce stress concentration by allowing deformation and energy dissipation, in order to safely transmit the high lateral forces into the fundaments. Structural solutions which represent an invisible protection measure are evaluated in regards to their effectiveness. The numerical analysis of this study is performed by using the MD Nastran software.     

Untersuchungen über das Trag‐ und Dehnungsverhalten des Betongurtes bei Verbundanschlüssen

Investigations about the load bearing‐ and strain behavior of the concrete slab in the range of composite connections. Due to the rising cost pressures in the construction industry, it is particularly important to choose efficient design methods to achieve economic structures. The use of the plastic hinge theory may lead to good results within the steel and composite construction industry because cross section‐ and system reserves can almost fully used. This means for the normal composite beam a redistribution of the bending moment from the support section to the field section. This redistribution causes an increase of the rotation at the composite connection. The presented tests show the influence of the reinforcement (type of reinforcement and reinforcement ratio) to the rotation capacity of the connection. The increased rotation requirements of composite connections in the area of plastic hinges should already be take in to account at planning state.