Dalle de verre windows consist of thick slabs of coloured glass set in a matrix of reinforced concrete. The invention of this special art form is closely linked to the developments in modern ...architecture in the first half of the 20th century that are characterized by using new technologies such as steel-frame construction, reinforced concrete and the increasing use of glass. Many of these windows are showing damage, some of it severe. Until now, the causes of damage have hardly been investigated and there is still no practical and suitable approach to the analysis of the state of conservation of dalle de verre glazings. One of the main objectives of an interdisciplinary project (2019–2021) was therefore to evaluate the potential of non-destructive techniques for the characterisation of and identification of damage of dalle the verre windows in their structural, physical and climatic context. Various non-destructive methods (Ground-Penetrating Radar, Electric resistivity, Half-cell potential, Ultrasonics, Induction, Magnet and Thermography) have been tested on two prominent dalle de verre examples: the windows created by Fernand Léger for the church of Saint-Germain d’Auxerre in Courfaivre (Swiss Jura mountains) and the large tripartite by Alexandre Cingria once decorating the choir window church of the Franciscan monastery at Fribourg, Switzerland. The results of the analyses presented in this paper provide valuable information on the advantages and limitations as well as the costs of the methods used.
ABSTRACT
The paper deals with a microwave‐tomography‐based solution algorithm tailored for use with GPR data‐processing applications. The algorithm tackles an inverse scattering problem in the ...frequency domain through the use of a linear model of the electromagnetic scattering, based on the Born approximation. In particular, we evaluate the reconstruction capabilities of the linear inversion algorithm in terms of the retrievable spatial variations of the unknown contrast function, whilst considering the problem of choosing an optimal frequency measurement step, theoretically, using diffraction tomography arguments. A numerical analysis of the technique is performed by means of the singular‐value decomposition tool, which allows us to extend the theoretical results to more realistic cases involving lossy soils. Finally, we present a series of reconstructions, obtained using synthetic and experimental data, which show the performance of the method under realistic conditions.
The interest in agroforestry systems has increased considerably in recent years. The systems are more resilient to climate change and offer advantages related to soil health and biodiversity. ...Although the aboveground impacts of agroforestry systems are well known, the knowledge concerning root growth of trees remains limited.
This study tested the applicability of a non-destructive investigation method, the ground penetrating radar (GPR), to detect tree roots. We mapped two 80-year-old pear trees in cropland and investigated the impact of tilled and no-tilled management on the root system architecture especially in deeper soils (>0.6 m).
The root mapping method was successful, we determined the main roots of the tree up to a depth of 0.75 m. In addition, we found tillage significantly impacted root distribution. Tillage removed tree roots almost completely to a depth of 0.4 m. The bulk of the roots was present at a depth of 0.6 to 0.75 m (83% of the roots) in the tilled section, while it was found at 0.3 to 0.55 m (74%) in the no-tilled section. Detected roots indicated an overcompensation by additional roots in the tilled section that were not formed without tillage.
Overall, we found agroforestry trees were rooting deeper, below the managed cropland and therefore colonise different soil layers. Thus, the potential volume of water and nutrient intake was enlarged, which might enhance the resilience of the combined production systems. In addition, our approach presents a method for future non-destructive and continuous monitoring of tree roots and their development.
•Testing GPR system to detect deep root interaction in agroforestry systems.•Arable crops and agroforestry tree roots colonise different soil depths.•Tillage impacted tree roots by removal in topsoil and overcompensation in subsoils.•Non-destructive monitoring method of tree root system and their development.
Corrosion of re-bar within reinforced concrete is a major problem in countries where salt is applied to roads for de-icing. Concrete structures are periodically inspected in order to monitor possible ...damage caused by chloride induced corrosion of the reinforcement. However, bridge decks covered with asphalt pavements are not accessible for visual inspection and probing is limited. As a result, the planning of rehabilitation of bridge decks is usually based on a small number of probes. Consequently, the condition of bridge decks can only be assessed with low certainty. Therefore, a method enabling to study the conditions of concrete bridge decks covered by asphalt pavements is desirable. This paper describes a laboratory experiment aiming at the investigation of the effects of moisture and chloride content on the amplitudes of radar signals. It can be shown that both, moisture and chloride content have a measurable influence on signal amplitudes. This may enable the future use of ground penetrating radar for the planning of probing campaigns or for the extrapolation of results obtained at single probing points.
Non-English title Kister, Bernd; Hugenschmidt, Johannes
Die Bautechnik,
01/2017, Letnik:
94, Številka:
1
Journal Article
Nondestructive testing assists the assessment of old retaining walls made of natural stonework During the last twelve years a rating system has been developed at the Lucerne University of Applied ...Sciences and Arts for the assessment of old retaining walls made of natural stonework. Up to now this rating system has been applied successfully in several projects. The goal of this rating system is to assess the as-is state of old retaining walls as well as their constructiveness. Unfortunately, in many cases there is no information available about the design and construction details. Therefore a research project has been carried out to evaluate the possible contribution of nondestructive testing for the investigation of the constructiveness of such walls. In this project different methods have been used with acoustic and electromagnetic waves. Data were acquired with those different methods on a test wall with a length of approximately 5 m and a height of 1.8 m. In addition, data were acquired on an existing old retaining wall on a Swiss pass road. The test results show that the selection of a test method for those old retaining walls made of natural stonework is highly dependent on the type of masonry of the retaining wall.Original Abstract: An der Hochschule Luzern wurde in den vergangenen zwolf Jahren ein Rating-System zur Beurteilung alter Stuetzbauwerke aus Natursteinmauerwerk entwickelt und bereits bei verschiedenen Projekten angewendet. Das Ziel dieses Rating-Systems ist es, sowohl den Zustand der Stuetzbauwerke als auch deren konstruktive Eigenschaften zu ermitteln und zu bewerten. Da Unterlagen zum Aufbau dieser Bauwerke in der Regel fehlen, wurde in einem Forschungsprojekt geprueft, welchen Beitrag zerstorungsfreie Pruefverfahren bei der Erkundung der kon struktiven Eigenschaften von alten Stuetzbauwerken aus Natursteinmauerwerk leisten konnen. Zum Einsatz kamen sowohl Verfahren mit akustischen Wellen als auch solche mit elektromagnetischen Wellen. Nachfolgend wird ueber die Ergebnisse verschiedener Messverfahren an einem ca. 5 m langen und 1,8 m hohen, extra fuer das Projekt hergestellten Mauerwerksprobekorper sowie an einer bestehenden alten Stuetzmauer berichtet. Die Versuchsergebnisse zeigen, dass die Wahl der Messmethode auf die Art des Mauerwerks abgestimmt werden muss.
Abstract
An der Hochschule Luzern wurde in den vergangenen zwölf Jahren ein Rating‐System zur Beurteilung alter Stützbauwerke aus Natursteinmauerwerk entwickelt und bereits bei verschiedenen ...Projekten angewendet. Das Ziel dieses Rating‐Systems ist es, sowohl den Zustand der Stützbauwerke als auch deren konstruktive Eigenschaften zu ermitteln und zu bewerten. Da Unterlagen zum Aufbau dieser Bauwerke in der Regel fehlen, wurde in einem Forschungsprojekt geprüft, welchen Beitrag zerstörungsfreie Prüfverfahren bei der Erkundung der kon struktiven Eigenschaften von alten Stützbauwerken aus Natursteinmauerwerk leisten können. Zum Einsatz kamen sowohl Verfahren mit akustischen Wellen als auch solche mit elektromagnetischen Wellen. Nachfolgend wird über die Ergebnisse verschiedener Messverfahren an einem ca. 5 m langen und 1,8 m hohen, extra für das Projekt hergestellten Mauerwerksprobekörper sowie an einer bestehenden alten Stützmauer berichtet. Die Versuchsergebnisse zeigen, dass die Wahl der Messmethode auf die Art des Mauerwerks abgestimmt werden muss.
Abstract
Nondestructive testing assists the assessment of old retaining walls made of natural stonework
During the last twelve years a rating system has been developed at the Lucerne University of Applied Sciences and Arts for the assessment of old retaining walls made of natural stonework. Up to now this rating system has been applied successfully in several projects. The goal of this rating system is to assess the as‐is state of old retaining walls as well as their constructiveness. Unfortunately, in many cases there is no information available about the design and construction details. Therefore a research project has been carried out to evaluate the possible contribution of nondestructive testing for the investigation of the constructiveness of such walls. In this project different methods have been used with acoustic and electromagnetic waves. Data were acquired with those different methods on a test wall with a length of approximately 5 m and a height of 1.8 m. In addition, data were acquired on an existing old retaining wall on a Swiss pass road. The test results show that the selection of a test method for those old retaining walls made of natural stonework is highly dependent on the type of masonry of the retaining wall.
An der Hochschule Luzern wurde in den vergangenen zwölf Jahren ein Rating‐System zur Beurteilung alter Stützbauwerke aus Natursteinmauerwerk entwickelt und bereits bei verschiedenen Projekten ...angewendet. Das Ziel dieses Rating‐Systems ist es, sowohl den Zustand der Stützbauwerke als auch deren konstruktive Eigenschaften zu ermitteln und zu bewerten. Da Unterlagen zum Aufbau dieser Bauwerke in der Regel fehlen, wurde in einem Forschungsprojekt geprüft, welchen Beitrag zerstörungsfreie Prüfverfahren bei der Erkundung der kon struktiven Eigenschaften von alten Stützbauwerken aus Natursteinmauerwerk leisten können. Zum Einsatz kamen sowohl Verfahren mit akustischen Wellen als auch solche mit elektromagnetischen Wellen. Nachfolgend wird über die Ergebnisse verschiedener Messverfahren an einem ca. 5 m langen und 1,8 m hohen, extra für das Projekt hergestellten Mauerwerksprobekörper sowie an einer bestehenden alten Stützmauer berichtet. Die Versuchsergebnisse zeigen, dass die Wahl der Messmethode auf die Art des Mauerwerks abgestimmt werden muss.
Nondestructive testing assists the assessment of old retaining walls made of natural stonework
During the last twelve years a rating system has been developed at the Lucerne University of Applied Sciences and Arts for the assessment of old retaining walls made of natural stonework. Up to now this rating system has been applied successfully in several projects. The goal of this rating system is to assess the as‐is state of old retaining walls as well as their constructiveness. Unfortunately, in many cases there is no information available about the design and construction details. Therefore a research project has been carried out to evaluate the possible contribution of nondestructive testing for the investigation of the constructiveness of such walls. In this project different methods have been used with acoustic and electromagnetic waves. Data were acquired with those different methods on a test wall with a length of approximately 5 m and a height of 1.8 m. In addition, data were acquired on an existing old retaining wall on a Swiss pass road. The test results show that the selection of a test method for those old retaining walls made of natural stonework is highly dependent on the type of masonry of the retaining wall.
The spreading of deicing salt on roads during winter and the consequent migration of chloride ions within concrete exposes structures reinforcement to corrosion. Reinforcement corrosion is ...problematic because it reduces the structure's load carrying capacity and a long-term consequence can be structural failure. The use of Ground Penetrating Radar (GPR) technology is commonly applied to reinforced concrete structural mapping. This paper provides methodologies for the calculation of the electromagnetic parameters from GPR data accounting for chloride content and its distribution within concrete. The previous work showed that they are linked with water and chloride content. A GPR dataset was carried out with bi-static off-ground GPR antennas during an experiment recreating chloride contamination processes in concrete specimens. Two novel solutions are presented in this paper, their use on the dataset returned the electromagnetic parameters of the concrete specimens with knowledge of their thickness. Firstly, a ray-based approach is provided as a fast computational tool to determine average material properties. Thereafter, a novel full-waveform inversion based on a multilayered forward model is presented. It allows the identification of conductivity gradients present inside the concrete. Finally, the results are compared with additional destructive testing; they present a good correspondence.
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