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Planar tomography and numerical analysis for damage characterization of impact loaded RC plates
(2020)
The damage analysis of reinforced concrete (RC) is of high interest for reasons of effective maintenance and structural safe-ty of buildings. The damage structures of RC plates loaded by an impact were investigated, applying X-ray planar tomogra-phy and finite element method (FEM). Planar tomography allows getting three-dimensional information of the RC elements and the damage including crack, spalling and scabbing. The FEM model validated on the tomography data justifies the appli-cation for further predictions of the damage description. In this study, we investigated concrete plates of three different thick-ness subjected to impacts at different low- and medium-velocity, whereby the used impactor had a flat tip, which resulted in small penetrations on the front side and scabbing on the rear side. In order to quantify the damage, the damage volume and its distribution through the plate were computed and the correlations between degree of damage and impact velocity were found out.
Prediction of dynamic effects of reinforced concrete structures under impact loading is a technical challenge. This is a consequence of the great variability of the physical properties resulting from the wide adaptability of reinforced concrete and a consequence of the wide range of impact loading. Experiments and numerical investigations are normally used on a small scale to address the problem. In this paper, impact tests on reinforced conrete plates with the lateral dimensions of 1.5 m x 1.5 m and a thickness of 30 cm are presented. In bending reinforcement, besides the velocity two properties are varied, the diameter and the spatial distribution of the rebars. Experiments are performed at the Otto-Mohr-Laboratory of the Institute of Concrete Structures of the Technische Universit¨at Dresden. Due to the accelerated fall of the impactor the velocity ranges between 20 and 70 m/s. In addition to the measured quantities such as bearing forces, accelerations are also measured at 4 different positions on and under the plate, as well as the deflection at several positions. The measured data are used for the analysis of the damage form and the numerical examinations with the program Ansys Autodyn and the material model after Drucker-Prager.
Numerical investigations support the tests, with detailed analysis of individual effects. These numerical computations and the planar tomographic investigations were carried out at BAM in Berlin. With the help of planar tomographic evaluation, the damaged structure is
made visible and compared with the numerical results. Influences of the bending reinforcement are explained on the basis of damage evaluation in the local area and on selected measured values. In addition to the test evaluation, the tomographic and numerical methods are presented.
Reinforced concrete (RC) is used as structural material in most diverse civil engineering applications. For the variability of its physical properties it is still an engineering challenge to meet all necessary requirements for the prediction of dynamic effects under impact loading. In this paper, investigations are shown within the scope of quantifying and evaluating the damage caused by an impact. The experimental investigations are performed in the field of low- and medium-velocity impact. The chosen flat nose shape results in small penetrations on the top side and scabbing on the bottom side. The plate is scanned with an adapted planar tomographic examination after the impact, and the damage is analysed, afterwards. Cracks and spalling are made visible with a reconstruction. The numerical model validated on the tomographic results justifies the application for further predictions of the damage description.
Reinforced concrete (RC) is used as structural material in most diverse civil engineering applications. For the variability of its physical properties it is still an engineering challenge to meet all necessary requirements for the prediction of dynamic effects under impact loading. In this paper, investigations are shown within the scope of quantifying and evaluating the damage caused by an impact. The experimental investigations are performed in the field of low- and medium-velocity impact. The chosen flat nose shape results in small penetrations on the top side and scabbing on the bottom side. The plate is scanned with an adapted planar tomographic examination after the impact, and the damage is analysed, afterwards. Cracks and spalling are made visible with a reconstruction. The numerical model validated on the tomographic results justifies the application for further predictions of the damage description.
Prediction of dynamic effects of reinforced concrete structures under impact loading is a technical challenge. This is a consequence of the great variability of the physical properties resulting from the wide adaptability of reinforced concrete and a consequence of the wide range of impact loading. Experiments and numerical investigations are normally used on a small scale to address the problem. In this paper, impact tests on reinforced conrete plates with the lateral dimensions of 1.5 m x 1.5 m and a thickness of 30 cm are presented. In bending reinforcement, besides the velocity two properties are varied, the diameter and the spatial distribution of the rebars. Experiments are performed at the Otto-Mohr-Laboratory of the Institute of Concrete Structures of the Technische Universit¨at Dresden. Due to the accelerated fall of the impactor the velocity ranges between 20 and 70 m/s. In addition to the measured quantities such as bearing forces, accelerations are also measured at 4 different positions on and under the plate, as well as the deflection at several positions. The measured data are used for the analysis of the damage form and the numerical examinations with the program Ansys Autodyn and the material model after Drucker-Prager. Numerical investigations support the tests, with detailed analysis of individual effects. These numerical computations and the planar tomographic investigations were carried out at BAM in Berlin. With the help of planar tomographic evaluation, the damaged structure is made visible and compared with the numerical results. Influences of the bending reinforcement are explained on the basis of damage evaluation in the local area and on selected measured values. In addition to the test evaluation, the tomographic and numerical methods are presented.
Due to the many possible applications, the uncomplicated production and the high application range, reinforced concrete is a widely used building material. This large range of physical material properties still poses an engineering challenge in determining all necessary requirements for predicting dynamic effects under impact load.
Many aspects of impact have already been examined and some correlations have been studied intensively. Examples are the work of Lastunen and Booker, who studied the influence of projectile properties on the impact form. Li has also investigated the local effects of an impact. The field of detailed damage analysis has not been in focus so far.
This presentation shows some studies in medium-velocity impact with the focus on post-impact damage evaluation. The impactor is modified so that the test plates show low penetration on the top and scabbing on the bottom. With the unique tomography lab test stand at BAM the plate is scanned after the impact and the damage is analyzed. Cracks and scabbing are made visible with a reconstruction. The comparison of simulation and tomography allows to create prognosis models for damage characterization.
We examine the behavior of reinforced concrete components subjected to impact induced loading conditions which might be caused by vessels collisions such as aircraft fuel tanks The concrete plates were impact damaged at TU Dresden and shipped to BAM At BAM laminar tomography as the imaging method is used to determine and quantify the damage state An automatic crack detection method based on template matching is applied to find the cracks and we aim to develop a new method using machine learning Algorithms In addition numerical models are developed to understand the experiment and to predict the damage structures based on failure mechanisms.
The contribution discusses the processing and analysis of data generated on two different ways of investigations for impact damage in reinforced concrete structures. Damage investigations are essential to determine type and characteristics of damage and thus the residual capacity. Damage describing data is generated using two different types of investigation, a non-destructive tomographic as well as numerical examination. Subsequently, data of both sources was merged and analysed. Within the research project “Behaviour of structural components during impact load conditions caused by aircraft fuel tank collision” reinforces concrete plates were damaged by impact loading, see Hering (2020). Afterwards the damaged specimens were investigated tomographically as well as numerically using several methods and models. Aim of the presented research work was to specify an objective comparability of numerical data with experimentally determined damage patterns and based on this, to establish a quantitative damage evaluation.
Schutzbauwerke von systemkritischen Infrastruktureinrichtungen wie Betonwände und Betonbarrieren müssen Anprallereignissen oder schweren Unfällen in einem vertretbaren Maße widerstehen können. Anprallereignisse können verschiedenster Natur sein. Hierzu zählen Steinschlag, Fahrzeug- oder Flugzeuganprall oder auch Geschosseinschlag. Geschosseinschläge bzw. Bei den Anprall- oder Impaktereignissen wird zwischen hartem und weichem Anprall unterschieden, bei hartem Anprall verformt sich der Anprallkörper nicht oder nur geringfügig, bei weichem Anprall stark.
In diesem Artikel werden Forschungsergebnisse zum harten Anprall auf bewehrte Stahlbetonplatten vorgestellt, welche über die letzten Jahre im Rahmen eines Kooperationsprojekts zwischen dem Institut für Massivbau (IMB) der Technischen Universität Dresden (TUD) und der Bundesanstalt für Materialforschung und -prüfung (BAM) durchgeführt wurden. Auf dem Gelände des Otto-Mohr-Labors (OML) der TUD steht hierfür ein speziell konzipierter Fallturm zur Verfügung. Der Aufbau im Fallturm lässt aktuell druckluftbeschleunigte Impaktversuche mit mittleren Anprallgeschwindigkeiten zu. Die durch Anprall geschädigten Stahlbetonplatten wurden anschließend bei der BAM mit Strahlung tomographisch untersucht. Diese Untersuchungen ermöglichen einen Blick auf die Schädigung und Rissstruktur im Inneren der Stahlbetonplatten.
Ein Schwerpunkt der durchgeführten Untersuchung ist der Vergleich von Testergebnissen mit den häufig angewendeten halbempirischen Berechnungsmethoden zu den erforderlichen Wandstärken und den sich daraus ergebenden zulässigen Anprallgeschwindigkeiten. Bei diesem Vorgehen wird auch die mit analytischen Methoden abschätzbare Durchdringungsgeschwindigkeit bzw. Austrittgeschwindigkeit eines Projektils ermittelt und mit den realen Testergebnissen verglichen. Außerdem wird der Einfluss von sowohl externen als auch internen Strukturparametern auf Risse betrachtet und ein Fazit abgeleitet. Weiterhin werden laufende und zukünftige wissenschaftliche Untersuchungen zum Anprall auf Betonstrukturen am IMB und der BAM genannt.