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Vienna, Austria

Kopf F.,FCP Fritsch | Schafer D.,ZT GmbH | Pistrol J.,Vienna University of Technology
Research and Applications in Structural Engineering, Mechanics and Computation - Proceedings of the 5th International Conference on Structural Engineering, Mechanics and Computation, SEMC 2013

In common buildings the Soil-Structure-Interaction (SSI) is governed by the elastic behavior of the building. The best conditions to see the soil effect predominate would be a dynamic rigid body movement of a massive building. For this reason measurements were carried out on an old anti-aircraft tower from World War II on typical Viennese soil conditions. The dynamic properties of the soil could be determined in two different ways. The first one is the common way using the dispersion of the Rayleigh waves on the soil surface and the back calculation to shear wave profiles. The second approach is the back calculation of the soil stiffness based on the soil-structure-interaction. With the simultaneous measurement of the dynamic movement of the building the kinematic behavior of the SSI could be determined. The tilting oscillations of the tower in both directions with different frequencies transmitted to the soil could be measured in the surroundings. The decay of these vibrations and their influence on the H/V-method results was studied. The results of the dynamic measurements were compared with different methods of numerical simulation. The benefits and the disadvantages of the methods can be compared. The calculation values of the numerical models could be calibrated with the real dynamic properties of the measured SSI-system. © 2013 Taylor & Francis Group. Source

Apostolidi E.,University of Natural Resources and Life Sciences, Vienna | Bergmeister K.,University of Natural Resources and Life Sciences, Vienna | Hilber R.,University of Natural Resources and Life Sciences, Vienna | Strauss A.,University of Natural Resources and Life Sciences, Vienna | And 5 more authors.
Life-Cycle of Structural Systems: Design, Assessment, Maintenance and Management - Proceedings of the 4th International Symposium on Life-Cycle Civil Engineering, IALCCE 2014

The current European road network and concrete bridges in particular have suffered in the past few decades serious and increasing damages, due to e.g. insufficient maintenance, incorrect calculation assumptions, change in use, constructional mistakes, environmental influences, etc. As engineering structures are designed in planning and execution according to current regulations and state of the art, the maintenance of such structures constitutes a serious problem for engineers. Although the addition of new reinforced concrete layers is a common practice to increase the shear capacity of a structural element, the objective of the paper is the development, optimization and assessment of an innovative steel reinforcement in form of sheet, replacing common reinforcing bars. A preliminary investigation considering the material and geometrical parameters of such a reinforcement type is presented, through a series of numerical simulations and experimental tests. © 2015 Taylor & Francis Group, London. Source

Amouzandeh A.,Vienna University of Technology | Zeiml M.,Vienna University of Technology | Zeiml M.,FCP Fritsch | Lackner R.,University of Innsbruck
Engineering Structures

The development of measures to avoid or minimise the destructive effects of fires in tunnels requires a quantitative assessment of the thermal intake of the structure during such incidents. In the underlying work, a typical tunnel-fire scenario is analysed with the help of Computational Fluid Dynamics (CFD) in order to predict temperature distributions inside the tunnel which in turn shall be used to assess the structural stability of the concrete lining. The CFD simulations are based on a fire code previously developed within the framework of OpenFOAM. The fire is simulated in an arched single-track, an arched double-track and a rectangular double-track cross-section of real dimensions taking into account two different ventilation velocities (0.5 and 3. m/s). Results are compared in terms of temperature distributions within the cross-section and longitudinal temperature distributions at ceiling level. Except for the temperature distribution within the cross-sections, little difference in results is seen for the two double-track tunnels with the low ventilation velocity (0.5. m/s), whereas higher temperature levels and a faster downstream movement of hot gases are observed in the single-track tunnel. For the high ventilation velocity (3. m/s), temperature levels drop dramatically and flow parameters within the three tunnel cross-sections differ insignificantly. In addition, a comparison of temperature profiles inside the concrete tunnel lining with results of a more detailed 1D calculation is presented. In order to obtain the most accurate temperature profiles, a procedure is suggested, where the 1D heat-conduction equation is solved by using the fluid temperatures from a previous CFD simulation, taking into account the temperature dependency of thermo-physical parameters of concrete and, if necessary, the risk of spalling. © 2014 Elsevier Ltd. Source

Pistrol J.,Vienna University of Technology | Adam D.,Vienna University of Technology | Villwock S.,HA MM AG | Volkel W.,HA MM AG | Kopf F.,FCP Fritsch
Geotechnical Engineering for Infrastructure and Development - Proceedings of the XVI European Conference on Soil Mechanics and Geotechnical Engineering, ECSMGE 2015

Dynamic roller compaction has become the common method for near-surface compaction, because dynamic rollers are much more efficient compared to static rollers. Two types of excitation are mainly used for dynamic roller compaction, the vibratory and the oscillatory roller. In the presented study the differences in functioning, mode of operation and loading the soil are outlined for the two types of excitation. First results of large-scale in-situ tests are presented in which the vertical earth pressure and tri-axial accelerations have been measured. Moreover a new indicator for the evaluation of the slip between the surface of an oscillatory drum and soil is presented. © The authors and ICE Publishing: All rights reserved, 2015. Source

Zhang Y.,Vienna University of Technology | Zeiml M.,FCP Fritsch | Pichler C.,University of Innsbruck | Lackner R.,University of Innsbruck | Mang H.A.,Vienna University of Technology
Poromechanics V - Proceedings of the 5th Biot Conference on Poromechanics

During spalling of fire-loaded concrete, the cross-sectional area of the concrete member is reduced, seriously affecting the integrity of the structure. Spalling is mainly attributed to two types of processes: thermo-hygral and thermo-mechanical. Thermo-hygral processes refer to the build-up of vapor pressure inside the concrete pores. Thermo-mechanical processes refer to the thermally-induced, restrained deformation of concrete. Both types of processes are closely connected to the physical and chemical behavior of concrete as a porous material. This contribution aims at realistic simulation of the stress state within fire-loaded concrete in order to attain insight into the development and occurrence of the critical state right before and during the event of spalling. This requires modeling of the two above-mentioned types of processes via a coupled thermo-hygro-chemo-mechanical model. Based on a coupled thermo-hygro-chemical model, the authors adopted a formulation of the effective-stress theory by combining the respective model with a multiscale homogenization approach (with the latter considering dehydration as the reverse of hydration), which gave access to the Biot's coefficent as a function of temperature. This led to a coupled thermo-hygro-chemo-mechanical code simulating the stress state in fire-loaded concrete as a consequence of both thermo-hygral and thermo-mechanical processes. In this coupled code, an embedded strong-discontinuity model is to be implemented, which is capable of capturing and tracking the propagation of a crack evolving in concrete as a quasi-brittle material. The aim is to attain the crack path as well as the width of the crack with the latter being closely connected to permeation of gas and water through the crack. With the resulting coupled model, it will be possible to take into account all major couplings, allowing to realistically simulate the spalling process. © 2013 American Society of Civil Engineers. Source

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