长期荷载作用下SFRC梁承载能力极限状态可靠性分析

为分析长期荷载作用下SFRC梁承载能力极限状态可靠性的时变规律,基于持荷10年的SFRC梁抗弯试验结果,建立了SFRC梁承载能力极限状态时变可靠性分析模型.对于Ⅰ系列梁(持荷水平不变、钢纤维掺量改变)和Ⅱ系列梁(持荷水平改变、钢纤维掺量不变),将等效抗力法和一次二阶矩法相结合,求得其时变可靠指标,并预测了100年长期荷载作用下可靠性的时变规律.结果表明:对于Ⅰ系列梁,钢纤维体积分数为0.5%是最佳掺量;对于Ⅱ系列梁,外荷载越小,可靠指标越大,抗弯承载力越大,外加荷载越接近,可靠指标越接近;在服役期内SFRC梁可靠指标先上升后下降,当钢筋开始锈蚀,可靠指标曲线出现拐点,导致梁正截面抗弯承载力下降明显.

Reliability Analysis of SFRC Beams Under Ultimate Limit States of Long-Term Load

Time-dependent reliability model for the ultimate load-carrying capacity of steel fiber reinforced concrete (SFRC) beams subjected to long-term load is established based on the results obtained from the beams under sustained load ten years.Two series of tested beams are considered: Series I with constantly applied load but varying steel fiber content, and Series II with the same steel fiber content but subjected to different applied loads. The time-dependent reliability indexes are determined and the reliability pattern for 100 years of long-term load is forecasted using the equivalent resistance method and the first-order-second-moment method. The results show that the optimum content of steel fibers is 0.5% in Series I beams; however, for Series II beams with the same steel fiber content, the smaller the applied load is, the larger the reliability index and the flexural capacity are. Also, the reliability indexes are almost the same for similar applied loads. Under service conditions, the reliability indexes increase at first and then decrease with time. An inflection point is observed in the reliability index curves when the steel reinforcement starts to corrosion, leading to an obvious decrease in the flexural capacity.