中文摘要：

已有的混凝土受热力学性能研究重点集中于500℃以上的高温区段,小于500℃的亚高温区段的混凝土强度则直接按常温处理,这不符合实际温度作用的受力情况。长期处于亚高温作用下的混凝土结构也需要了解其材料受力性能的变化规律。通过亚高温区段混凝土的受压强度试验,考察了不同亚高温及温度持续时间对其的影响。结果表明,不同温度持续时间的混凝土受压强度随温度升高的变化趋势相似,在100～250℃波动较大,且在100℃附近形成一个强度的低谷,250℃后则呈急剧下降趋势。而当试件温度分布均匀后,温度持续时间对混凝土受压强度的影响很小。通过试验还给出了亚高温下混凝土受压强度的计算公式。

英文摘要：

Existing researches on behaviors of heated concrete are mainly focused on the high temperature range above 500℃.The compressive strength of concrete under sub-high temperature（500℃） is only simply taken as that at room temperature,and this does not accord with its actual mechanical properties.It is more important to investigate the mechanical properties of concrete in the structures subjected to long-term sub-high temperature.The influences of sub-high temperature and its lasting time on the concrete compressive strength were investigated based on experiments.It is shown that the concrete compressive strength with different temperature lasting time has a similar changing trend.There exists a strength fluctuation from 100℃ to 250℃ with a concave around 100℃ and sharp decrease after 250℃.Temperature lasting time has little effect on the compressive strength after the temperature distribution becomes uniform.A calculation formula of strength of concrete subjected to sub-high temperature was presented.