Zur Gründung von Bauwerken auf weichen, gering tragfähigen Böden werden unter anderem Betonpfähle, einzeln oder in Pfahlgruppen, eingesetzt. Deren Bewertung bzgl. Tragverhalten bzw. Integrität ist bei bestimmten Baugrundverhältnissen und Pfahlgeometrien schwierig. Hierfür werden statische und dynamische Pfahlprüfungen durchgeführt. Aus Messwerten vom Pfahlkopf bzw. vom oberen Pfahlbereich werden üblicherweise die notwendigen Aussagen abgeleitet. Eine genauere Bewertung ist möglich, wenn präzise Messwerte über die gesamte Pfahllänge vorliegen. Deshalb wurden hochauflösende betoneinbettbare Messwertaufnehmer auf Basis von Faser-Fabry-Perot-Sensoren entwickelt, die in Modell- und in realen Rammpfählen getestet wurden. Der Beitrag beschreibt den Sensor, die Installation und exemplarisch einige Testergebnisse zur Erfassung der Wellenausbreitung im Modellpfahl. Feldtests wurden zurzeit der Erstellung des Manuskripts erfolgreich begonnen.
Reinforced concrete piles are often used for structures on non-sufficiently bearing soil areas. Assessment of bearing capacity and bearing behaviour of large concrete piles remains a difficult task under specific soil conditions and pile geometries. Usually static and dynamic pile tests are carried out for quality assurance. From dynamic measurements taken only from the pile head, the bearing behaviour and structural integrity can be derived using the one-dimensional theory of wave propagation. More precise information about the pile features can be achieved by highly resolving fibre-optic sensors based on Fabry-Perot technology, distributed over several locations along the pile length. Small scale piles and real driven piles have been tested. This paper describes the sensor, the sensor installation, and experimental results of tests in laboratory as well as test results for recording the wave propagation in the small scale piles.
In structural engineering timber is appreciated due to its low weight, its high aesthetic quality and because it is a renewable resource. The market share of timber structures and wood based hybrid structures will clearly increase over the next few years due to greater environmental awareness and a higher demand for sustainability. However, building with timber is marked by characteristics which lead to significant disadvantages in comparison wifh technical materials. For example, in outdoor areas Chemical and structural approaches offen lead to unsatisfactory and expensive Solutions with respect to durability. An idea is to make natural lumber a high-performance material which can be designed to meet the engineers’ demands conceming strength, stiffness, durability, shape, safety etc. These changes can affect the material itself, new technologies or a new approach to monitoring. Especially hybrids made of common timber products and technical textiles or enhanced timber products are high-capacitive and reach high bearing strengths with low material input and good durability. These hybrids are particularly qualified to use the advantages of wood and minimize the disadvantages. They can be used in different ways for load bearing structures, i.e. bridges. New construction types need monitoring to observe the stress and strains for which they were designed, and the structures’ behaviour as well as to guarantee required safety levels. The aim of successful usage of fibre optic measurement technology in timber elements was the development of a technology for measuring the lengthening in timber elements and wood based hybrid elements by using fibre optic sensors. The scientific and technical challenge was to develop an applicationtechnology for optical glass fibres in timber and densified veneer wood.
In laboratory tests as well as with the erection of a footbridge and during in-situ tests it could be shown that the structurally integrated fibre optic sensor technology used is suitable for short and long term measurement. The developed embedment technology tums out to be practical and fit for good transfer of strain-values from timber to the modified sensor fibres.
Static and dynamic pile tests are carried out to determine the load bearing capacity and the quality of reinforced concrete piles. As part of a round robin test to evaluate dynamic load tests, structure integrated fibre optic strain sensors were used to receive more detailed information about the strains along the pile length compared to conventional measurements at the pile head. This paper shows the instrumentation of the pile with extrinsic Fabry-Perot interferometers sensors and fibre Bragg gratings sensors together with the results of the conducted static load test as well as the dynamic load Tests and pile integrity tests.