Precast, prestressed concrete panels (PCPs) have been widely used in Texas as stay-in-place formwork in bridge deck construction. Although PCPs are widely popular and extensively used, Texas is experiencing problems with collinear cracks (cracks along the strands) in panels. One reason for the formation of collinear cracks is thought to be the required level of initial prestress. Currently, PCPs are designed assuming a 45-ksi, lump-sum prestress loss. If the prestress losses are demonstrated to be lower than this value, this could justify the use of a lower initial prestress, probably resulting in fewer collinear cracks. For this purpose, 20 precast, prestressed panels were cast at two different plants. Half of those 20 panels were fabricated with the current TxDOT-required prestress of 16.1 kips per strand, and the other half were fabricated with a lower prestress of 14.4 kips per strand based on initially observed prestress losses of 25 ksi or less. Thirteen of those panels were instrumented with strain gages and monitored over their life time. Observed losses stabilized after five months, and are found to be about 24.4 ksi. Even with the reduced initial prestress, the remaining prestress in all panels exceeds the value now assumed by TxDOT for design. / text

Sandwichkonstruktionen mit Deckschichten aus dünnen Metallblechen und Stahlbeton stellen seit Jahrzehnten bewährte und wirtschaftliche Verbundkonstruktionen für Gebäudehüllen dar. Der Einsatz von dünnen Deckschichten aus textilbewehrtem Beton verbindet deren Vorteile und ermöglicht auch bei steigenden Anforderungen an den Wärmeschutz geringe Konstruktionsdicken. Der Beitrag berichtet über die Entwicklung von Ingenieurmodellen zur wirklichkeitsnahen Beschreibung des Tragverhaltens von Sandwichquerschnitten aus textilbewehrtem Beton, Hartschaumdämmkern und geeigneten Verbundmitteln. / Sandwich constructions made of thin metal sheets and structural concrete have been reliable and economic composite structures in the past decades. The application of thin-walled facings made of Textile Reinforced Concrete (TRC) combines the advantages of this construction and allows for slender construction thicknesses despite the progressing demands on thermal insulation. This contribution reports on the development of models, which enable the realistic mechanical description of the load-bearing behavior of the sandwich panels made of two TRC-facings and a core of polymeric rigid foam together with suitable connecting devices.