Georg Hochreiner

Dowel deformations in multi-dowel LVL-connections under moment loading

Abstract The aim of the experimental study presented herein is the assessment and quantification of the behavior of individual dowels in multi-dowel connections loaded by a bending moment. For this purpose, double-shear, steel-to-timber connections with nine steel dowels arranged in different patterns and with different dowel diameters were tested in four-point bending. In order to achieve a ductile behavior with up to 7° relative rotation, the connections were partly reinforced with self-tapping screws. The reinforcement did not influence the global load–deformation behavior, neither for dowel diameters of 12 mm nor for 20 mm, as long as cracking was not decisive. The deformation of the individual dowels was studied by means of a non-contact deformation measurement system. Thus, the crushing deformation, that is, the deformation at the steel plate, and the bending deformation of the dowels could be quantified. In the case of 12 mm dowels, the bending deformation was larger than the crushing deformation, while it was smaller in the case of 20 mm dowels. Moreover, dowels loaded parallel to the grain showed larger bending deformations than dowels loaded perpendicular to the grain. This indicates that the loading of the individual dowels in the connection differs depending on their location.

19th Century Iron Dome Structures in the Vienna Hofburg. An Insight into the Simplified Structural Assessment of that Period and Its Evaluation Using Modern Engineering Software

The use of iron load-bearing systems in all types of building structures (e.g. infrastructure, commercial buildings, sacred buildings, prestigious buildings) gained enormous importance during the urban development and expansion of Vienna’s city center in the second half of the 19th century. A recent case study on the iron dome structures in what is known as the Michaelertrakt of the Vienna Hofburg provided the results of a detailed geometrical survey using high-tech instruments as well as archive documents containing a simplified structural analysis and dimensioning of the cross sections of the cupola as annex to the proposal for construction in terms of weight and costs. The geometrical survey data served as a basis for subsequent structural modeling within a commercial structural engineering software. Taken together, the data allow both an examination of the simplified structural assessment methods used at the end of the 19th century and an assessment of the present status of the historic dome structures with further information for their maintenance. The design for only vertical loading was in line with the theory of J. W. Schwedler. The extensions from A. Foppl were referenced for the design of the bracing system subjected to wind loads. The restrictions of the hand calculation formerly used made it necessary to make several simplifications, such as setting of additional hinges with consequences for the bending moments and superposition of different load cases. Finally, the consequences for neglecting the compatibility of displacements within this type of shell structure could now be evaluated and validated.