Modelluntersuchungen zur Windeinwirkung auf stählerne Doppelmantelbehälter

The model tests of wind action on the steel double‐shell tanks. The paper shows the results of the wind tunnel tests on the double shell cylindrical vertical tank models with fixed and floating roofs. During tests the pressure distribution onto both shells and onto the roofs was measured. The influence of the following parameters on the wind load value and distribution was analysed: – Distance between tank shells (3 distances) – Type of roof (floating or fixed) – Position of floating roof (4 positions). The measurement results have been presented as graphs of the pressure coefficients (C_p).     

Vorspannung mit Monolitzen ohne Verbund

Monostrand Prestressing with unbonded Tendons. Application, Experiences, Advantages, Economic Viability Prestressing of strands with unbonded tendons has proved to be effective in practice without reservation. The additional procedure is not inconsiderable, but should be regarded in its context, since it will be more than compensated for by the convincing advantages like crack‐freeness, low deflection of components, etc., in the long run. The article below discusses recent findings and experiences. Additionally, it deals with expanded fields of application, such as partial prestressing, flat slabs, hollow‐block slabs with long span, and, as a quantum leap, the prestressed flat slab made of steel fibre concrete.     

Oberflächenbearbeitung von Industriebetonböden bei Verwendung von SVB mit und ohne Fasern

Surface processing of industrial Concrete Floors made of SCC with and without Fibres. Self‐compacting concrete (SCC) is one the most important innovations in materials technology. However, from the point of producers and processors problems can be identified for certain application cases, e.g. for industrial concrete floors. In particular for surface processing and evenness requirements difficulties may occur. The following report summarises practical tests related to this topic and shows that SCC is indeed an alternative compared to conventional construction methods.     

Spannglieder mit Kunststoffhüllrohren zur Herstellung von Brücken ohne Betonstahlbewehrung

Tendons with Plastic Ducts for Bridges without Mild Steel Reinforcement Frequently the conventional sealing of concrete bridges does not show a satisfactory serviceability in practice. Imperfect sealing leads to chloride entry into the structure because of bending cracks in the upper side of bridges in the range of negative moments. If a road passes under a bridge, there is the risk of chloride entry caused by salt fog spread on the surface of the bridge. In addition to the restoration liability of the sealing the pavement requires regular repair work. This periodic repair work causes high costs and affects the traffic flow. The method presented in this paper is characterized by omitting corrosion‐sensitive reinforcement and by integrating the pavement in the structure. The aim is to create concrete bridges with improved durability which can be manufactured with comparable costs to conventional concrete bridges. The results of experimental tests on the structural behavior of such structures will be presented.     

Querkrafttragfähigkeit von Fahrbahnplatten ohne Querkraftbewehrung

Es wird über Versuche zur Querkrafttragfähigkeit von Brückenfahrbahnplatten aus Stahlbeton berichtet. Diese zeigen, dass die bekannten Rechenansätze für Bauteile ohne Querkraftbewehrung nach DIN 1045‐1 bzw. DIN‐FB 102 für Fahrbahnplatten auf der sicheren Seite liegen, die tatsächliche Tragfähigkeit aber weit unterschätzt wird. Weitere Ansätze zur Berechnung der Querkrafttragfähigkeit von Stahlbetonbauteilen ohne Querkraftbewehrung werden erörtert. Während die Modelle bei der Auswertung einer Datenbank von Balkenversuchen eine gute Übereinstimmung aufweisen, zeigt der Vergleich mit den Modellversuchen, dass die meisten Rechenverfahren die Tragfähigkeit der Platten unterschätzen. Zur Berechnung der Querkrafttragfähigkeit von Platten ohne Querkraftbewehrung unter Punktlasten wird ein Modell vorgeschlagen, welches die Querkrafttragfähigkeit mit der Zugbeanspruchung der Biegezugzone im kritischen Bereich verknüpft. Shear Resistance of Bridge Decks without Transverse Reinforcement The design of concrete bridge deck slabs is of major concern since the introduction of the Eurocodes as the calculated shear capacity of slabs without stirrups and staggered reinforcement according to the new design standards is often considerably smaller compared to the former regulations i.e. DIN 1045:88. This raises the question whether the existing structures are still save. A series of 12 tests on 4 different specimens representing a bridge deck was performed to examine the real load bearing behaviour of a slab with and without shear reinforcement under a wheel (point) load. The evaluation of the test results revealed, that the current design formula with an assumed elastic shear force distribution leads to rather conservative values of shear capacity for bridge deck slabs. Various approaches for shear design are discussed and the accuracy is checked by means of a shear database and the test results. A new model to calculate the shear capacity is proposed which shows a better agreement with test data than the known approaches.