Development of Performance Based Fire Resistant Design the Prestressed Concrete Members

本研究的目的是为开发基于性能的预应力混凝土构件耐火设计收集基础实验数据。对标称直径12.7mm的7丝股进行了高温拉伸试验，得到了应力-应变关系。指定的温度为室温20摄氏度，每100摄氏度直到600摄氏度。将观察到的抗拉强度折减比（定义为一定温度下的抗拉强度与室温下的抗拉强度之比）与上一年试验得到的预应力筋的折减比进行比较，结果表明，钢绞线的折减比预应力筋的折减比大20%。这种差异可归因于在生产过程中产生的复合材料：钢绞线具有马氏体，预应力筋具有马氏体。在项目实施的第二年，对预应力钢筋在高温下的蠕变应变进行了研究。已知两项试验采用直径为13mm的SBPR1080/1230预应力杆。在它们被加热到特定的温度后，棒材受到恒定的拉伸应力。在其他测试中，当它们被加载到指定的应力后，在测试期间保持恒定，杆被加热到指定的温度。温度高达300摄氏度。蠕变应变-时间关系在温度条件下是理想化的。对3根预应力混凝土梁进行了高温和使用荷载试验。按照ISO834规定的温度-时间关系对梁进行加热。分配给每个梁的热持续时间为30,60分钟或由梁中心的挠度和挠度速度定义的失效。故障发生在209分钟。根据混凝土覆盖层厚度确定了梁的耐火能力。加热30分钟和60分钟的梁在耐火测试几个月后加载失效。研究了结构的剩余承载能力和刚度。少

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