Schädigung einer schlaff bewehrten Betonbrücke durch Verkehrsbelastung

Evaluation of Damage Due to Traffic on a Reinforced Concrete Bridge An investigation of the damage caused by road traffic on a reinforced concrete bridge was performed. Focus was given to damage induced by extra‐heavy vehicles. A damage model based on fatigue of reinforcement bars was employed. The stress cycles in the reinforcement bars were determined using measurements of the crack widths under traffic loading which were analysed using the rainflow method and Miner's rule. A monitoring system was mounted and used for seven weeks continuously to collect input data for the damage model. Computer software was developed to process the monitoring data in the sense of the damage model. The results indicate that a singular passage of an extraheavy vehicle over the investigated bridge causes damage equivalent to the damage caused by one day of average weekly traffic. The described method was developed and used for the first time in the described project.     

Zuverlässigkeit von Mauerwerk aus großformatigen Steinen

Reliability of masonry consisting of large sized units. Within the scope of the harmonisation of the European design codes the partial safety concept has been recommended also for masonry structures. This requires the values of the partial safety factors to be discussed. Whereas for steel and concrete structures a large amount of studies have been conducted, this is not the case for masonry structures. This explains the large scatter of the partial safety factors suggested for the resistance side for the design unreinforced masonry in international codes. In this paper, the reliability of unreinforced masonry walls under compression made of large sized units will be analysed. A suggestion for optimized partial safety factors will be given.     

Reliability of masonry walls subjected to in‐plane loading: A slip failure along head joints / Zuverlässigkeit von Mauerwerkswänden bei Belastung in der Ebene: Versagen entlang der Stoßfugenflucht

Masonry structures are a sustainable, economical and traditionally widely used type of construction. However, current masonry design codes are rather conservative, so there is a growing need for revision i.e. calibration of safety factors to improve the allocation of material resources. In this paper, we investigate the probability of occurrence of slip failure along head joints (perpends) in masonry subjected to in‐plane loading. An appropriate limit state function is established and the masonry material properties and loads are defined as random variables in order to simulate likelihood of occurrence of a slip failure regime along the head joints. Furthermore, an example of masonry wall with probabilistic analysis outcomes using Monte Carlo simulation is presented and recommendations for further work are provided.     

Stochastische Abschätzung der Versagenswahrscheinlichkeit von Spannbetontragwerken infolge Spannungsrisskorrosion unter Berücksichtigung verschiedener Schädigungsverteilungen

Der bis 1965 hergestellte vergütete Spannstahl weist eine hohe Empfindlichkeit gegenüber Spannungsrisskorrosion auf. Ein Ausfall des Spannstahls in einzelnen Bauteilen während der Nutzung kann nicht ausgeschlossen werden, sowohl bei Brücken als auch bei Hochbauten. In diesem Beitrag wird mit Hilfe der Stochastik jedoch gezeigt, dass die Wahrscheinlichkeit eines Versagens ohne An kün digung durch die Rissbildung bei Spannbetonbauteilen mit meh reren Spanngliedern, wie dies bei Brücken in der Regel der Fall ist, im Allgemeinen sehr gering ist. Für eine bessere statistische Aussage ist eine gezielte Untersuchung zur Feststellung des Schadenablaufs von Spannstahl im Bauwerk sehr wünschenswert. Stochastic estimation for failure probability of prestressed concrete members due to stress corrosion considering different failure processes of tendons. The hardened and tempered prestressing steel, which was manufactured by 1965, exhibits a high sensibility to stress corrosion. The loss for the bearing capacity of the individual tendon during the service life can not be excluded, both for bridges and building structures. However, in this contribution, by using stochastic method, it is demonstrated that the failure probability for existing prestressed concrete structures without prior announcement by cracking is very small. For a better statistical estimation, the inspection of the failure processes of the tendons in structures is very helpful.