The demand for construction materials at tunnel construction sites is naturally very high. Thus, tunnel excavation material is increasingly used as a substitute for conventional mineral aggregates. Excavation material is not a standard product in terms of geometric, physical, and chemical properties of the rock as its quality is changes during tunnel driving depending on the geology and excavation method. By using this material as aggregate for concrete, the concrete obtains its characteristic properties. Certain concrete properties do not only influence the construction material itself but also fasten the elements that are assembled to the structural concrete. In this case, experimental validation of the usability of this special concrete for postinstalled anchorages and the effectiveness of different fastening systems are required. Therefore, investigations using various postinstalled anchor systems in different inner shell concrete types made of recycled aggregate (in this context, Bündner schist from the Brenner Base Tunnel) were performed in this study to obtain an assessment of the applicability of these systems in concrete with aggregate made of tunnel excavation material.
Iron based shape memory alloys (Fe-SMA) have recently been used as active flexural strengthening material for reinforced concrete (RC) beams. Fe-SMAs are characterized by a shape memory effect (SME) which allows the recovery of previously induced plastic deformations through heating. If these deformations are restrained a recovery stress is generated by the SME. This recovery stress can be used to prestress a SMA applied as a strengthening material. This paper investigates the performance and the load deformation behavior of RC beams strengthened with mechanical end anchored unbonded Fe-SMA strips activated by sequentially infrared heating. The performance of a single loop loaded and a double loop loaded SMA strengthened RC beam are compared to an un-strengthened beam and a reference beam strengthened with commercially available structural steel. In these tests the SMA strengthened beam had the highest cracking load and the highest ultimate load. It is shown that the serviceability behavior of a concrete beam can be improved by a second thermal activation. The sequential heating procedure causes different temperature and stress states during activation along the SMA strip that have not been researched previously. The possible effect of this different temperature and stress states on metal lattice phase transformation is modeled and discussed. Moreover the role of the martensitic transformation during the cooling process on leveling the inhomogeneity of phase state in the overheated section is pointed out.
Post‐installed fastening systems are essential in structural engineering nowadays. Triggered by the increasing popularity of high strength concrete (HSC) and ultra‐high performance concrete (UHPC), fastening in these basements is more and more frequently applied. This inevitably leads to the question of the applicability of conventional fastening systems and the corresponding design concepts with concrete showing a compressive strength of up to 200 N/mm2. According to EAD 330232‐00‐0601, mechanical fasteners have to be placed in predrilled holes in compacted reinforced or unreinforced concrete without fibers with strength classes in the range of C20/25 to C50/60 in compliance with EN 206. This means that concrete strength class C50/60 also provides the reference for higher concrete strength; the impact of fibers and accompanying increase of concrete ductility is also excluded. Within the framework of this contribution it is intended to analyze the following aspects: (a) proof of applicability of various fastening systems in unreinforced and fiber‐reinforced high strength concrete via experimental investigations and (b) making a statement regarding the currently valid European Assessment Document and provide experimental background for this issue.
Die ISO 17025 [1] legt für Prüf-und Kalibrierlaboratorien fest, dass bei der Durchführung von Prüfungen bzw. Kalibrierungen die zugehörige Messunsicherheit zu bestimmen ist. Methoden, um die Messunsicherheit zu bestimmen, können sowohl mittels exakter rechnerischer Ermittlung als auch durch eine geeignete Schätzung (vgl. Abschnitt 7.6.2 der ISO 17025 [1]) erfolgen. Hierzu sind alle Beiträge, welche für die Ermittlung der Messunsicherheit von Bedeutung sind, nach sinnvollem Ermessen heranzuziehen [1]. EAD 330232 [2]: "Mechanical Fasteners for Use in Concrete", Annex A definiert als Anforderung an im Rahmen dieser Bewertungsrichtlinie tätige Prüfstellen, dass die Bestimmungen der ISO 17025 einzuhalten sind. Somit sind die Anforderungen an die messtechnische Rückführung und die Bestimmung der Messunsicherheit einzuhalten.
Bei der Errichtung von langen Tunnel fallen große Mengen an Tunnelausbruchmaterial an, welche bei entsprechender Aufbereitung einer Wiederverwertung zugeführt und für eine – zumindest teilweise – Eigenversorgung des Bauvorhabens mit aufbereiteten Gesteinskörnungen verwendet werden können. Diese Vorgangsweise birgt nicht nur ein Einsparungspotenzial hinsichtlich Anschaffung, Lagerung und Transport von Baustoffen, die ansonsten zugeführt werden müssten, sondern trägt neben einer Verringerung der Umweltbelastungen auch zur Reduzierung des benötigten Deponievolumens und damit zu einer Kostenersparnis bei. Die Strategie eines umfangreichen Materialrecyclings wurde bereits beim Bau des Lötschberg und Gotthard Basistunnels erfolgreich umgesetzt. Aus diesem Grund gibt es auch im Zuge der Errichtung des Brenner Basistunnels Bestrebungen, eine größtmögliche Wiederverwertung von ausgebrochenem Gesteinsmaterial zu erreichen. Hier erfolgt derzeit u. a. der Vortrieb des Zufahrtstunnels Wolf in Steinach am Brenner, bei welchem Gesteine der Bündnerschieferserie ausgebrochen werden. Aufbauend auf im Vorfeld getätigte Untersuchungen werden hier seit Herbst 2014 die höherwertigen Kalkschiefer der Bündnerschieferserie mittels dreistufigem Brechersystem und einer leistungsstarken Nassaufbereitung im Bereich der Deponie Padastertal aufbereitet und v. a. als Gesteinskörnung für Spritz‐ und Konstruktionsbeton sowie als Drainagekies für die Errichtung des Bauloses verwertet. Processing and recycling of tunnel excavation material at the Brenner Base Tunnel During the construction of major tunnels large quantities of excavation material are generated, that – if suitably treated and processed – can be recycled as aggregate and be used in the construction of the tunnel itself. This approach generates numerous benefits regarding the costs for material procurement, storage and transport. In addition, reduction of environmental impact and demand for landfill volume can be achieved. The strategy of an extensive material recycling has already been successfully implemented in the construction of the Swiss Lötschberg and Gotthard base tunnel. For this reason there are significant efforts to achieve an equal high level of recycling of tunnel excavation material in the course of the construction of the Brenner Base Tunnel. There, tunnel driving of the access tunnel Wolf in Steinach am Brenner is currently ongoing and rocks of the Bündner Schists are being excavated. Building on the results of previous studies, calcareous schists of higher quality from Wolf have been recycled since autumn 2014 using a three‐stage rock crushing system followed by a high performing wet‐processing of the aggregates at the area of the Padastertal landfill site. The processed material is used primarily as aggregate for shotcrete and structural concrete as well as draining gravel.
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