Der nachfolgende Aufsatz behandelt die Berechnung und Messung von hydratationsbedingten Zwangspannungen in massigen Betonbauteilen. Dabei wird auf das zeitveränderliche und viskoelastische Materialverhalten des Betons und dessen Berücksichtigung innerhalb eines numerischen Berechnungsverfahrens besonders eingegangen. Die vorgestellten Zusammenhänge werden anhand eines Dehnstabmodells mathematisch beschrieben und innerhalb eines FE‐Modells numerisch implementiert. Im Zuge des Betonierens einer Sohlplatte eines Schleusenbauwerks werden die Berechnungsergebnisse mit Messdaten für die Spannungsentwicklung verglichen und bewertet. Consideration of Viscoelasticity in Computation of Hydration induced Stresses in Massive Concrete Members The present document reports about the computation and measurement of hydration induced stresses in massive concrete structures. It focuses on the time dependent and viscoelastic material properties of concrete and their consideration within a numerical computation procedure. The presented relationships will be described mathematically by using a strain‐rod‐model and be implemented in a FEM‐Model. The computed results will be compared and evaluated by using measured stress data obtained during the casting of a lock's base slab.

Temperatur‐ und Spannungsberechnungen hydratisierender Betonbauteile sind mittlerweile Stand der Technik und vielfach bereits Bestandteil entsprechender Bauverträge. Die meisten der zur Verfügung stehenden Modelle sind jedoch für die Bauausführung aufgrund der Komplexität der Eingabeparameter und des Berechnungsaufwandes wenig praktikabel. Darüber hinaus ist die Bedienung ihrer resultierenden Softwarepakete oft kompliziert und wenig transparent. Der Beitrag stellt deshalb die Grundlagen eines praxisorientierten Softwarewerkzeuges sowie dessen Anwendung an anspruchsvollen Bauvorhaben vor.

For drying building structures [1], dielectric heating using RF energy (in this case 13.56 MHz) is an efficient and fast alternative to conventional heating methods based on heat transfer from the surface to the interior of the masonry. Another innovative application of volumetric RF heating is the chemical-free pest control in wood-based materials [2]. For such applications where the RF systems often are not completely shielded, the propagation or coupling of the electromagnetic wave into wires that are placed inside the field cannot be neglected which represents a certain risk. Depending on the different electromagnetic coupling mechanisms, several interference signals can be generated. In order to protect electrical equipment in the surrounding, these interferences have to be significantly reduced by electrical filters. For this purpose, initially a cost-effective (at least in comparison to standard RF measurement systems) and more robust measuring concept was developed. With the help of this system, the common mode (I_CM) interference could be identified as the dominant part and the differential mode (I_DM) interference as a minor disturbance. Based on the experimental evaluation, a cost-effective filter for the respective disturbance was constructed and successfully tested.

Carbon reinforced concrete (CRC) has been researched in Germany for around 20 years by now. To strengthen structures with this building material, a grid of carbon fibre in a fine-grained concrete layer is applied e.g. to the bending tension zone of an existing reinforced concrete structure (RC). This increases the load bearing capacity of the structure. The grids have changed significantly over the past few years. They have larger fiber cross-sections and different impregnations, which results in tensile forces that are approx. 3 times higher than those of textiles of the older generation. However, this increase in tensile strength can entail additional failure mechanisms: In some tests on RC specimens strengthened with a higher number of CRC layers the tensile forces in the strengthening layer could no longer be fully transferred into the steel reinforcement concrete member and damage occurred, either in the RC structure, in the bonding area between the RC structure and the strengthening layer or within the strengthening layer. To enable an optimized utilization of the carbon grids in the future, the various forms of failure are examined more closely in a research project. Different solutions are derived. The focus of the investigationsis on the anchoring of the ends of the strengthening layers. The aim is to find constructive solutions to make better use of the carbon grids and thereby further increase both the economic efficiency and the ecological balance of carbon reinforced concrete.