Untersuchungen zur Tragfähigkeit von geschädigten Spanngliedern mit nachträglichem Verbund

Investigations on the Ultimate Strength of Damaged Post‐Tensioned Tendons In order to assess the influence of bond action between strands, injection grout and surrounding concrete on the ultimate strength of damaged post‐tensioning tendons more accurately, a series of tensile tests on tendons which were built using post‐tensioning strands and wires from demolished bridges were carried out. Wire and strand breakage was included in the tendons at specified patterns. Furthermore, the influence of the quality of the injection grout on the load carrying‐capacity of the tendon was studied. The results of the test series show that tendons with damaged or broken wires or strands are able to carry a high percentage of the ultimate load of an undamaged tendon.     

Verbund im Glasbau – Neues und Bewährtes

Laminated glass – novel and well‐tried. With increasing safety specifications, glass laminates become more important in the use of glass for structural elements. The requirements of laminated glass includes safety against fall arrest, post breakage behaviour and bomb blast resistance. In addition to the structural aspects, laminates of two or more glass panes are nowadays increasingly used for sound insulation, protection against direct or diffuse sunlight etc. Various design possibilities (coloured or printed interlayer, embedding of fabric, papers meshes etc.) are available for a wide range of architectural applications. Parallel to the rising requirements and possibilities of laminated glass, scientific studies concentrated on the mechanical properties of laminates with Polyvinylbutyral (PVB) interlayer and development of new interlayers by the industry. This article compares laminates with different interlayers and shows the results of scientific research.     

Verifizierung zerstörungsfreier Prüfverfahren zur Detektion von Spannstahlschäden an Spannbetonbauteilen mit nachträglichem Verbund

Verification of Non‐Destructive Testing Techniques for Detection of Prestressing Steel Damage at Post‐Tensioned Concrete Members For an assessment of the risk potential of existing structures where in the case of prestressing steel damage the load‐bearing capacity could be significantly affected non‐destructive testing techniques which enable reliable evaluation of the condition of the prestressing steels are of utmost importance. During the demolition of the Hohenzollerndamm bridge in Berlin where damage of prestressing wires due to hydrogen‐induced stress corrosion cracking were found in former investigations parts of the girders of the bridge superstructure could be taken out. After non‐destructive investigation by means of two testing techniques based on magnetic leakage flux measurement and one technique based on electromagnetic resonance measurement the single wires were inspected in order to verify the non‐destructive testing results with respect to their reliability. From the results it can be concluded that areas with fractures of several wires could be detected by the two techniques based on magnetic leakage flux measurement.     

Trag‐ und Verformungsverhalten von Verbundfugen mit elastischem Verbund

Load bearing and deformation behavior of bonding joints with elastic composites. The performance of modern composite structures made of steel and concrete is decisively influenced by the bearing and deformation behavior as well as the deformation capacity of the composite joint. Further development with regard to safety and efficiency requires a deeper understanding of the load transfer mechanisms in order to respect the deformations and deformability of the load bearing elements more accurately. The composite connectors and their ductility decisively affect the load bearing and deformation behavior of the composite structures. In addition to the displacement parallel to the composite joint, which is taken into account in the existing investigations on the theory of the elastic composite action, the uplift between the composite partners should also be included in the investigations. The new calculation model of composite beams is primary designed for the elastic deformability of headed studs. The design model with its relevant parameters is explained. The calculated results are compared to test results and the numerical simulations.