Papers by Norbert Gebbeken
International Journal of Impact Engineering, 2019
Masonry walls represent one of the most common applied constructions in civil engineering and arc... more Masonry walls represent one of the most common applied constructions in civil engineering and architecture. The inhomogeneous nature of masonry imposes a challenge in the development of robust modeling techniques especially under high dynamic loads. In this contribution some modeling strategies are discussed which are suitable for the simulation of unreinforced masonry walls under explosion loads. The damage formation of the wall under loads resulting from far-field as well as contact explosions is investigated. Firstly the issue of an appropriate material model for bricks under high strain rates is discussed. Through a proper adaptation of a material model initially developed for concrete under blast loads all the necessary parameters for the bricks are derived. Subsequently the focus lies in capturing the local damage formation and the resulting debris due to a contact detonation. Small parts of the wall in the proximity of the explosion separate from the main body of the wall and travel at high velocities. They can establish an additional danger for persons and infrastructure which theoretically lie in a secure distance from the target of the explosion. The numerical results which will be presented in this paper are validated with appropriate experiments.
Der Gebäude- und Bausektor als große CO2-Emittenten werden sich drastisch verändern müssen. Im In... more Der Gebäude- und Bausektor als große CO2-Emittenten werden sich drastisch verändern müssen. Im Interview mit Bauen+ erklärt Professor Norbert Gebbeken, Präsident der Bayerischen Ingenieurekammer Bau, welche Veränderungen zielführend sein werden, was das Label "Sustainable Bavaria" dabei für Ziele verfolgt, welche Innovationspotenziale es zu nutzen gilt und welche Rolle die Kammern als Körperschaften des öffentlichen Rechts spielen. Diese Metadaten wurden zur Verfügung gestellt von der Literaturdatenbank RSWB®plus
Beton- Und Stahlbetonbau, Jul 1, 2006
If reinforced concrete structural elements are subjected to a blast load a widely unknown shearli... more If reinforced concrete structural elements are subjected to a blast load a widely unknown shearlike failure type may be observed. Thereby, failure of a tension or compression strut occurs, that cannot be explained by a truss and tie analogy. Instead of this, shear cracks directly at the edge of the support will form. In case of failure the structural element will shear off before a bending mechanism can be formed. For this failure type no consistent dimensioning concept exists by now.
Wiley-VCH Verlag GmbH & Co. KGaA eBooks, Jun 3, 2013
Bautechnik, Dec 18, 2020
Background: Numerous associations between brain-reactive antibodies and neurological or psychiatr... more Background: Numerous associations between brain-reactive antibodies and neurological or psychiatric symptoms have been proposed. Serum autoantibody against the muscarinic cholinergic receptor (mAChR) was increased in some patients with chronic fatigue syndrome (CFS) or psychiatric disease. We examined whether serum autoantibody against mAChR affected the central cholinergic system by measuring brain mAChR binding and acetylcholinesterase activity using positron emission tomography (PET) in CFS patients with positive [CFS(+)] and negative [CFS(2)] autoantibodies. Methodology: Five CFS(+) and six CFS(2) patients, as well as 11 normal control subjects underwent a series of PET measurements with N-[ 11 C]methyl-3-piperidyl benzilate [ 11 C](+)3-MPB for the mAChR binding and N-[ 11 C]methyl-4-piperidyl acetate [ 11 C]MP4A for acetylcholinesterase activity. Cognitive function of all subjects was assessed by neuropsychological tests. Although the brain [ 11 C](+)3-MPB binding in CFS(2) patients did not differ from normal controls, CFS(+) patients showed significantly lower [ 11 C](+)3-MPB binding than CFS(2) patients and normal controls. In contrast, the [ 11 C]MP4A index showed no significant differences among these three groups. Neuropsychological measures were similar among groups. Conclusion: The present results demonstrate that serum autoantibody against the mAChR can affect the brain mAChR without altering acetylcholinesterase activity and cognitive functions in CFS patients.
Bautechnik, Apr 1, 2008
An der Universität der Bundeswehr München wird derzeit an einem Projekt gearbeitet, das sich mit ... more An der Universität der Bundeswehr München wird derzeit an einem Projekt gearbeitet, das sich mit der schnellen Abschätzung der Tragfähigkeit bestehender Brückentragwerke befasst. Die Erkundung und Klassifizierung einer Brücke darf dabei maximal drei Tage dauern. Unter der Voraussetzung, dass Bauunterlagen nicht mehr zur Verfügung stehen, wird dazu ein Hilfsmittel entwickelt. Das Lösungskonzept basiert auf den drei Teil schritten Brückenerkundung, Tragfähigkeitsberechnung und Brückenverhaltensmessung. Bei der Brückenerkundung müssen die für die Berechnung relevanten Parameter der Brücke – im wesentlichen Geometrieparameter und Materialparameter – erfasst werden. Die Brückenerkundung wird über ein Expertensystem gesteuert. Die Tragfähigkeitsberechnung wird ebenfalls computerunterstützt durchgeführt. Brückenverhaltensmessungen dienen zur Qualitätsbeurteilung der Erkundungsdaten und des Berechnungsmodells der Tragkonstruktion. Das in diesem Beitrag vorgestellte System ist offen für Erweiterungen. Derzeit wird an der Entwicklung eines Einstufungsverfahrens beschädigter Brücken gearbeitet.
Journal of Structural Engineering-asce, Oct 1, 2020
AbstractProtective barriers are frequently used to protect buildings and their inhabitants from b... more AbstractProtective barriers are frequently used to protect buildings and their inhabitants from blast and vehicle impact. This paper presents numerical investigations of the impulse reduction perfo...
Elsevier eBooks, 2013
Abstract: This chapter focuses on the influence of the tensile behaviour of concrete on protectiv... more Abstract: This chapter focuses on the influence of the tensile behaviour of concrete on protective structures in practice. Based on the fundamentals given in previous chapters, the actions of impact, penetration and perforation are discussed, followed by the contact detonation. A specific section is devoted to blast design. If a building or a structural element has faced exceptional loads, its residual carrying capacity is of interest. The chapter ends with a description of a number of projects that have been set up.
Engineering Computations, May 1, 1998
As far as steel‐rod structures are concerned the yield‐hinge theory is a very efficient approach ... more As far as steel‐rod structures are concerned the yield‐hinge theory is a very efficient approach of the ultimate‐load theory. Unfortunately, most of the published strategies suffer from considerable deficiencies which depend on two main reasons: first, the yield condition is not approximated very well, and, second, a flow rule is not incorporated at all. This may significantly affect the calculated load‐carrying behaviour and as a consequence the elasto‐plastic failure prediction. In the present paper a consistent formulation of a refined numerical method based on the yield‐hinge theory is consistently developed from the theory of plasticity. The derivation is carried out in the framework of a geometrically nonlinear Timoshenko beam theory discretized for the displacement based finite element method. The plastic deformations can be interpreted as three‐dimensional eccentric yield‐hinges (generalized yield‐hinges). The presented numerical xamples show the efficiency of the proposed method.
International Journal of Impact Engineering, Sep 1, 2019
Abstract This paper presents experimental and numerical investigations on the performance of vari... more Abstract This paper presents experimental and numerical investigations on the performance of various blast wall configurations in attenuating the shock wave. The blast walls are composed of a gabion wall with a canopy made of metal sheets, which is mounted at the top of the gabion wall with different angles of inclination. Three experiments were conducted for each configuration. Numerical models are developed and validated against the experimental data. Due to the small width of blast walls in the experiments, besides the vertical air flow over the top of the wall, the horizontal air flow around the sides of the wall plays a great role in the overpressure distribution behind the wall. The interaction between these air flows causes an overpressure increase at the building facade. In order to prove the design concept of the canopy, the wall width in the forthcoming experiments should be so large that no horizontal air flow occurs. Using the validated numerical models, three observations arisen from the studies of blast walls having infinite width. Firstly, the canopies can further reduce the overpressure and impulse behind the blast wall. Secondly, configuration M3 (canopy arranged 45° facing the charge) shows the best performance in shock wave attenuation among all three configurations. It offers an overpressure (impulse) reduction ranging from 51.7% to 88.0% (from 30.5% to 59.2%) at the gauges employed in the experiments, compared to the free field scenario. Thirdly, the optimal angle of inclination of the canopy, by which the blast wall achieves the best shock wave attenuation performance, lies between 105° and 120° (between 115° and 125°) for the overpressure (impulse) reduction.
International Journal of Mechanical Sciences, Sep 1, 2020
Abstract This paper studies how the properties of cylindrical explosive charges influence their g... more Abstract This paper studies how the properties of cylindrical explosive charges influence their generated blast loads (peak overpressure and maximum impulse) for surface burst scenarios, focusing on the aspect ratio (or length-to-diameter ratio) of the cylinder and the point of detonation of the charge. Specifically, the following three points of detonation are considered: the cylindrical charge is detonated at its bottom, middle or top centre, respectively. Numerical models are developed for both hemispherical and cylindrical charges, and are validated against experimental data available in the open literature. Important conclusions regarding the blast-resistant design are drawn from the parametric studies conducted using the validated models. Neglecting the effect of the cylindrical charge shape can result in underestimating the peak overpressure (maximum impulse) in the near field by a factor as high 6.6 (2.9). Therefore, the shape of the charge should be represented appropriately in the numerical simulations used for the blast-resistant design of protective structures subjected to near-field detonations. The generated shock front is known to smoothen out as the scaled distance increases, “healing” into a hemispherical one in the far field. However, cylindrical charges generate about 1.2 times higher blast loads in the far field than hemispherical ones do. The significance of the cylindrical charge shape effect on the peak overpressure (maximum impulse) resulting from the three considered points of detonation can be sorted in descending order as follows: bottom-centre-detonated > middle-centre-detonated > top-centre-detonated (top-centre-detonated > middle-centre-detonated = bottom-centre-detonated). The influence range is characterized by a scaled distance, above which the maximum value of the ratio of the peak overpressure (maximum impulse) of cylindrical charges and that of hemispherical charges converges to a constant value (1.2). The influence range for the overpressure is more or less the same (4.0 m/kg1/3) for the three different points of detonation, whereas the cylinder detonated at the bottom centre has a larger influence range for the impulse (8.0 m/kg1/3) than the cylinders detonated at the middle (4.2 m/kg1/3) and top centre (2.5 m/kg1/3).
Engineering mechanics, 1995
Journal of Applied Mathematics and Mechanics, Oct 16, 2008
Proceedings of the Ninth International Conference on Computational Structures Technology, May 20, 2009
Shock Waves, Sep 1, 2020
This paper develops a new empirical formula for the prediction of the triple point path in irregu... more This paper develops a new empirical formula for the prediction of the triple point path in irregular shock reflection cases. Numerical simulations using a two-dimensional axisymmetric multi-material arbitrary Lagrangian-Eulerian formulation are employed to obtain the data of fluid density. Using the data of fluid density and nodal coordinates, the gradients of fluid density are determined and then used to generate numerical schlieren images. Based on these images, the triple point paths are derived and compared with the models of the Unified Facilities Criteria (UFC) and Natural Resources Defense Council (NRDC) as well as two models from the open literature. It is found that the numerically derived triple point paths are in good agreement with those predicted by a recently published model in the open literature for the typical ground range of shock wave propagation of up to 6 m. Considering the whole distance range, it is found that the agreement of different models of the triple point path with the numerical ones depends on the considered blast scenario, i.e., the scaled charge height. For small-scaled charge heights, the model of the UFC and the recently published model in the open literature are in better agreement with the numerical results than the other two models, whereas the NRDC model has the best agreement with the numerical results for large-scaled charge heights. Based on the numerical results, a new empirical formula is proposed for the prediction of the triple point path, which is valid for a wide range of the scaled charge heights from 0.5 to 3.5 m/kg 1/3 and scaled ground distances up to 15 m/kg 1/3 .
Engineering Structures, Jun 1, 2020
Protective barriers are regarded as a useful means to enhance the safety level of buildings and r... more Protective barriers are regarded as a useful means to enhance the safety level of buildings and residents in cases of air blast and impact scenarios. However, only limited research exists concerning the properties and effectiveness in mitigating the blast loads of air-permeable metallic barriers, which requires far fewer materials than ordinary solid walls. This paper explores the blast mitigation effect of an innovative barrier type using woven wire mesh. Numerical models were developed and validated against the experimental values of both peak overpressures and maximum impulses, which were published by the authors in a previous study. The influence of the Mach stem formation, which is attributed to the small elevation of the explosive charge above the ground surface, on the blast loads is also examined. It is found that the Mach stem formation significantly affects the peak overpressure at gauge ps1 (1 m ahead of the barriers), whereas its effects on the peak overpressures at the remaining gauges and on the maximum impulses at all gauges are negligibly small. This indicates that the validated numerical models can be used to assess the blast mitigation effect behind the barriers. Based on the numerical results at the employed gauges, the barriers using woven wire mesh can achieve an overpressure (impulse) reduction as high as 31.6% (41.6%) with respect to the free field scenario, in which no obstacles exist in the path of the shock wave propagation. Furthermore, the validated numerical models are used to shed light on the barrier behaviour against air blast by analysing the overpressure-time histories and by visualizing the shock wave propagation. This assists in pointing out the underlying reasons for the noticeable phenomena observed in the experiments. Moreover, two parametric studies are conducted in order to discuss the impact of the gabion wall thickness and the opening span between the gabion walls on the blast mitigation effect of barriers.
Transactions of Tianjin University, 2006
The identification of the critical infrastructure has shown that the build civil engineering infr... more The identification of the critical infrastructure has shown that the build civil engineering infrastructure is almost involved everywhere, even with the IT-infrastructure. Therefore, the passive safety of structures is demanded. Security associations have analyzed that most assaults came along with explosion and impact scenarios, which amount in 80% of assaults. Consequently, these are the extraordinary loads the structures have to be planned and designed for. To carry out such an engineering job, the engineer has to be educated in multiple disciplines as physics, material science, continuum mechanics, numerical mechanics, testing, structural engineering and related specific fields as wave propagation etc. We will concentrate on the subjects of numerical simulation and testing.
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Papers by Norbert Gebbeken