Sandwichelemente mit Betondeckschichten besitzen gute bauphysikalische Eigenschaften, einen hohen Vorfertigungsgrad, geringe Montagezeiten und eine gute architektonische Gestaltbarkeit. Werden die Deckschichten mit einer Betonstahlbewehrung ausgeführt, ergibt sich ihre Dicke aufgrund der in EC 2 [1] geforderten Mindestbetondeckung zum Korrosionsschutz der Bewehrung zu etwa 80 mm [2]. Weiterhin wird bei der Bemessung von Stahlbetonsandwichelementen die Verbundtragwirkungen zwischen den einzelnen Schichten nicht angesetzt, sodass das volle Potenzial der Sandwichbauweise bei Stahlbetonsandwichelementen nicht ausgeschöpft wird. Das Forschungsvorhaben beschäftigte sich daher, aufbauend auf den Ergebnissen aus den Projekten HE 2637/16-1 und HE 2637/16-2 [3], s. S.356 ff ., mit der praxisnahen Umsetzung von weitspannenden Sandwichelementen mit dünnen Deckschichten unter Ausnutzung der Sandwichtragwirkung. Ein analytisches Berechnungsmodell, das im Zuge des Vorhabens entwickelt wurde, berücksichtigt die Verbundtragwirkung zwischen den einzelnen Schichten und kann das Trag- und Verformungsverhalten zutreffend abbilden. / Sandwich elements with concrete facings have excellent physical properties, a high level of prefabrication, short assembly times and various architectural design options. The facings are usually produced with steel reinforcement, which leads to a thickness of about 80 mm due to the minimum concrete cover required in EC 2 [1] for corrosion protection of the reinforcement [2]. Furthermore, the bond between the single layers are not taken into account in the design of sandwich elements, so that the full potential of sandwich constructions with reinforced concrete facings is not completely exhausted. Based on the projects HE 2637/16-1 and HE 2637/16-2 [3], see page 356 et seq., the focus of the transfer project was set on wide-span sandwich elements with thin facings made of carbon reinforced concrete and their practical production. An analytical model, which was developed during the project term, takes into account the bond between the single layers and can accurately represent the load-bearing and deformation behaviour of the novel sandwich elements.

Voltage instability is a major concern in operation of power systems and it is well known that voltage instability and collapse have led to blackout or abnormally low voltages in a significant part of the power system. Consequently, tracking the proximity of the power system to an insecure voltage condition has become an important element of any protection and control scheme. The expected time until instability is a critical aspect. There are a few energy management systems including voltage stability analysis function in the real-time environment of control centres, these are based on assumptions (such as off-line models of the system loads) that may lead the system to an insecure operation and/or poor utilization of the resources. Voltage instability is driven by the load dynamics, and investigations have shown that load restoration due to the on-load tap changer (OLTC) action is the main cause of the voltage instability. However, the aggregate loads seen from bulk power delivery transformers are still the most uncertain power system components, due to the uncertainty of the participation of individual loads and shortcomings of the present approaches in the load modeling. In order to develop and implement a true on-line voltage stability analysis method, the on-line accurate modeling of the higher voltage (supply system) and the lower voltage level (aggregate load) based on the local measurements is required. In this research, using the changes in the load bus measured voltage and current, novel methods are developed to estimate the supply system equivalent and to identify load parameters. Random changes in the load voltage and current are processed to estimate the supply system Thevenin impedance and the composite load components are identified in a peeling process using the load bus data changes during a large disturbance in the system. The results are then used to anticipate a possible long-term voltage instability caused by the on-load tap changer operation following the disturbance. Work on the standard test system is provided to validate the proposed methods. The findings in this research are expected to provide a better understanding of the load dynamics role in the voltage stability, and improve the reliability and economy of the system operation by making it possible to decrease uncertainty in security margins and determine accurately the transfer limits.