Investigation of the seismic out‐of‐plane behaviour of unreinforced masonry walls

The structural stability of unreinforced masonry (URM) walls has to be guaranteed not only under static (permanent and live) loads but also under earthquake loads. Loads transverse to the plane (out‐of‐plane) often have a decisive influence on the load‐bearing capacity. In practical applications, simplified methods from codes, guidelines and literature are often used to analyse and evaluate the out‐of‐plane capacity of load‐bearing and non‐load‐bearing URM walls. The results of these simplified methods can be significantly conservative and inaccurate since essential influencing effects are neglected. For many existing buildings, the simplified methods underestimate the capacity, which leads to cost‐intensive retrofitting and strengthening measures or complete replacement by other wall systems. In order to realistically estimate the out‐of‐plane capacity, parameters such as wall geometry, boundary conditions, vertical loads and especially dynamic effects (e.g. inertia forces) have to be taken into account. In this paper, non‐linear time history simulations are presented to investigate the influence of these effects. The numerically determined maximum acceptable earthquake acceleration is compared with results from simplified analysis models. The comparison shows that the out‐of‐plane capacity is significantly higher than the values predicted by simplified models. Finally, several initial experimental seismic tests conducted on the shaking table of the TU Kaiserslautern are presented, together with the planned extensive experimental test program on the out‐of‐plane capacity of masonry walls.     

Grundlagen zur Festlegung der Sicherheitselemente des Betriebsfestigkeitsnachweises

Principles of determination of safety features for fatigue assessment. According to Eurocode 3 the fatigue behaviour of steel structures can be assessed either by means of the damage equivalent stress range or directly using the damage accumulation method (Miner's rule). Partial safety factors for load and resistance are to be considered. On resistance side, the partial safety factors vary between 1.0 and 1.6 depending on the structure type, i. e. road bridge, railway bridge or crane runway girder. The fatigue assessment methods are based on different forms of Miner's rule, and accordingly different reference S/N curves with or without consideration of fatigue strength. Theoretically, fatigue failure occurs when the damage sum reaches an amount of D = 1.0. In this paper the “actual damage sum at failure” will be determined by means of evaluation of fatigue tests conducted on welded joints. The “actual damage sums” deviate in most cases significantly from 1.0 and are generally lognormal distributed. Knowing the distribution characteristics allows the determination of the partial safety factors for resistance, which are required within the semi‐probabilistic safety concept to take into account both material and model uncertainties, depending on the utilized form of Miner's rule.     

Zur Wiedergeburt einer historischen Gitterbrücke

On the rebirth of a historic lattice truss bridge. In this contribution, in view of a complicated history of the 160 years old wrought‐iron lattice truss bridge in Tczew (Poland) across the Vistula, and with reference to the two emerged ideas of the reconstruction, the load test of the original bridge carrying structures has been described. The historical Bridge across the Vistula is loaded with a new bridge road deck. This was performed recently by the experimental institution for bridge constructions of the Politechnika Gdańska (Gdańsk University of Technology). The completed proof has confirmed the assumed strength of the new bridge deck, but also a surprisingly high toughness, greatly desired at present, of the original superstructure itself. The investigated monumental ingenieur construction of the past is a bridge structure that, in its meaning, can surely be compared with the famous Britannia Bridge.     

Verfahrensprüfung zur Bestimmung von Anziehparametern für vorgespannte geschraubte Verbindungen

Procedure qualification for the determination of tightening parameters for preloaded bolted connections. DIN EN 1090‐2 and DIN EN 1993‐1‐8/NA define tightening procedures for preloaded bolted assemblies tightened at the nut side by simple use thereof. However, in a multitude of applications, preloaded bolted connections are used, which for example are tightened on the head side, designed as tapped hole connections and/or are to be used several times. In these cases, a procedure test is necessary to determine the tightening parameters. The present paper describes the principal procedure for carrying out such a procedure test, in particular the target level of preloading, the length of thread engagement for components with internal threads, the single and multiple use of components, and the boundary criteria for determining the tightening parameters. Furthermore, the procedure is explained using practical examples.     

Die Fachstelle Brückenmessung der DB Netz AG

The department of bridge measurement of DB Netz AG. Over 25 000 railway bridges lie within the route network of the DB Net AG. The safe use of these bridges is ensured through regular checks by trained personal and is augmented by calculations regarding structural safety, fatigue and residual lifetime. In 1923, only 3 years after the foundation of the Deutsche Reichsbahn, a specialized department was founded at the Berlin headquarters to effectively address the complex technical issues relating to railway bridges. In‐situ direct measurements provide information of the complete system's behavior under real life conditions enabling objective assessments.