In research on concrete constructions, fiber optic sensor technology is becoming increasingly important. It enables high‐frequency and quasi‐continuous measurement of temperature and strain distribution. Furthermore, this technology offers the opportunity to determine the crack width within the cross section of specimens and not, as with conventional instrumentation, only from the outside. While experience for application of fiber sensors in steel‐reinforced concrete research already exists for several years, only few findings are available for textile‐reinforced concrete (TRC). This article gives a short overview of the principle of fiber optic sensor technology, presents possible concepts for utilization in TRC testing, and explains the necessary post‐processing steps for the preparation of the measurement results by means of an example from current research. Finally, the results are validated with conventional measuring methods and the applicability and further challenges are discussed.
Sandwich‐structured composites represent an efficient method to establish building envelopes which concurrently satisfy several demands. Besides low self‐weight with high load‐bearing capacity, sandwich panels provide sufficient physical properties, such as heat and sound insulation. In general, sandwich panels for applications in building industry are made of flat or thin profiled metal sheets or thick concrete facings. However, standard elements are limited to short spans. In contrast, spatially shaped concrete structures with folded plate or curved geometry provide high stiffness and load‐carrying capacity even for thin elements. The application of folded plate and curved concrete structures to sandwich panels combines the advantages of both construction methods. To realize thin facings in various shapes, high performance cementitious composites are advantageous. Ultra‐high performance fiber reinforced concrete (UHPFRC) provides high compressive and tensile strengths with ductile material behavior. The application of non‐corrosive reinforcement, for example, carbon fiber reinforced polymer (CFRP), allows for filigree concrete elements with a thin concrete cover to only fulfill bond requirements. For sandwich panels with folded plate or curved facings, new production methods are necessary to account for cross‐sections in various shapes. This paper introduces the basic ideas of non‐planar concrete sandwich elements for long‐span roof structures and the developed production methods.
Realistic characterization of fatigue loading resistance is a paramount for an economical and reliable structural design of reinforced concrete (RC) and prestressed concrete (PC) structures. The need for innovative experimental methods for the characterization of fatigue behavior is driven by the current aims to construct wind turbine towers that must resist up to N = 10 7 loading cycles corresponding to 25 years of service life. Considering the number of possible configurations with regard to structural geometries, cross-sectional layout of reinforcement and loading scenarios, experimental data are required that capture the key mechanisms driving the fatigue damage between the reinforcement and concrete matrix. Experimental investigations of bond behavior under fatigue loading have been reported in the literature in the 90′s of last century. Since then, no systematic investigation of bond fatigue behavior has been published. As a consequence, no assessment rules are available for the bond fatigue, only separate assessment rules for concrete and steel. The present paper will report on the ongoing research of bond fatigue behavior using the beam-end test setup. The test campaign includes the push-in loading with the goal to provide data characterizing the compressive behavior of reinforced cross sections in wind turbine towers.
Zusammenfassung Im Stegöffnungsbereich von Stahlbeton- oder Verbundträgern wird ein erheblicher Teil der globalen Querkraft vom perforierten Trägersteg in die Stahlbetongurte ober- oder unterhalb der Öffnung umgelagert. Der Betongurt muss daher zur Abtragung der lokalen Querkraft ausreichend dimensioniert und seine Querkrafttragfähigkeit mit geeigneten Berechnungsmethoden nachgewiesen werden. In verschiedenen bestehenden Nachweiskonzepten für die Querkrafttragfähigkeit in Stegöffnungsbereichen wird die Tragwirkung des Betongurtes nicht oder nur unzureichend berücksichtigt. Der vorliegende Beitrag zielt darauf ab, die Rolle der Stahlbetongurte beim Querkraftabtrag in Stegöffnungsbereichen zu klären, die resultierenden Besonderheiten für die Bemessung herauszuarbeiten und praxisorientierte Regeln für die Berechnung und den Querkraftnachweis vorzuschlagen.
New design provisions for anchorage and lap design, based on Model Code 2010 and the related background document, have been proposed for the next generation of Eurocode 2 (prEC2). In this article, the new provisions are examined and compared with the provisions in current Eurocode 2 (EC2). In the first of the three parts of this study, design examples are developed to show the practicability and effectiveness of the new design provisions. In the second part, parametric studies are carried out to check the generality of the new provisions and to clarify the roles of the main input parameters controlling the design of anchorages and laps. In the third part, a comparison is made between the predictions based on the new provisions and the results of a large database reported in the literature. To improve the fitting of the test results, adjustments are proposed for the coefficients appearing in the provisions of prEC2. The proposed adjustments—that may be introduced into National Annexes—ensure a sufficient level of safety of the new provisions for the design of anchorages and laps.
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