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通过自行研制开发的大型拼装式多功能电力加热炉,按照ISO834标准曲线升温,对26根无粘结预应力混凝土扁梁试件进行高温下试验研究。试验中观测了试件表面出现的渗水、油脂流淌与混凝土爆裂及外观颜色变化等宏观现象,研究了高温下试件变形、无粘结预应力筋的应力等力学性能的变化规律,分析了不同初始荷载、混凝土净保护层厚度及综合配筋指标等主要因素对其高温下力学性能的影响。试验结果表明:高温下试件发生动态连续变形,升温初期跨中挠度增加较小,温度较高时跨中挠度增长较大;预应力变化比较复杂;在同等升温条件下,试件承受的初始恒载越大,挠度变形也越大;增加混凝土保护层厚度,能延缓其内部钢筋的升温,提高试件的抗火性能;综合配筋指标q0较小的试件抵抗高温变形的能力较差。
Through the self-developed large-scale assembled multi-function electric heating furnace, according to the curve of ISO834 standard curve, 26 unbonded prestressed concrete flat beam specimens were tested under high temperature. In the experiment, macroscopic phenomena such as water seepage, grease flow and concrete burst and appearance color change were observed on the specimen surface. The variation of the mechanical properties such as the deformation of the specimen under high temperature and the stress of unbonded prestressed tendons were studied. Initial load, the thickness of the net protective layer and the comprehensive reinforcement index and other main factors on the mechanical properties at high temperature. The experimental results show that the dynamic deformation of the specimen occurs at high temperature, and the increase of the mid-span deflection is small at the early stage of the heating. The deflection of the mid-span increases with the increase of the temperature. The variation of the prestress is more complicated. Under the same heating condition, The greater the constant load is, the larger the deflection is. The thickness of concrete cover can delay the temperature rise of the internal reinforcement and improve the fire resistance of the specimen. The smaller the strength of composite specimens, the lower the resistance is, .