Development of Performance Based Fire Resistant Design the Prestressed Concrete Members

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The objective of this study is to collect fundamental experimental data for developing a performance-based fire resistant design of prestressed concrete members.Tensile tests on 7-wire strands of 12.7mm in nominal diameter at elevated temperature were carried out and stress-strain relationships were obtained. The specified temperatures were room temperature of 20 degrees Celsius, and every 100 degrees till 600 degrees Celsius. Observed tensile strength reduction ratios which are defined as a ratio of tensile strength at a certain temperature to that at the room temperature was compared with those for prestressing bars, experimentally obtained in the previous year The comparison revealed that the reduction ratio of the strands was 20% larger than that of the prestressing bars. The difference can be attributed to the composites which were generated during their productions: strands have marlin and prestressing bars have martensite.In the second year of the project creep strain of prestre … More ssing bars at elevated temperature was investigated. SBPR1080/1230 prestressing bars of 13mm in diameter were used for the knowing two tests. After they were heated to a specified temperature the bars were subjected to a constant tensile stress. In the other tests after they were loaded to a specified stress, which was kept constant during the tests the bars were heated to a specified temperature. The temperature was up to 300 degree Celsius. Creep strain-time relationships were idealized in terms of the temperature.Three prestressed concrete beams were constructed and tested under service load and high temperature. The beams were heated following the temperature time relation specified in ISO834. The heat duration which was assigned to each beam was 30, 60 minutes or to failure which was defined by the deflection and deflection velocity at the center of the beam. The failure occurred at 209 minutes. The beams were found to have fire resistant capacity according to the concrete cover thickness. The beams which were heated 30 and 60 minutes were loaded to failure a few months after fire resistant tests. The residual load carrying capacities and stiffness were investigated. Less