At present, organic epoxy adhesives are usually used when strengthening concrete structures with carbon fiber sheets, but the softening points of organic adhesives are too low, most of which lie between 60℃ and 80℃. Because temperatures are high in summer, the surface temperatures of concrete bridge structures are often higher than the softening points of organic adhesives in some areas and the concrete structures strengthened with carbon fiber sheets using organic epoxy adhesives are difficult to meet heat resisting requirements.Therefore, the alkali-activated slag cementitious materials (AASCM) with the strength at 600℃ no lower than that at the normal atmospheric temperature were selected to paste carbon fiber sheets to strengthen 4 beams over the state of ultimate bearing capacity, and the mechanical properties of these 4 bonded prestressed truss concrete composite beams encased with circular steel tubes were studied by experiments. The test values of the flexural carrying capacity of these beams and the mid-span P-f curves presenting the two-fold line were obtained. On the basis of the test results, the calculation method of the flexural carrying capacity of the mentioned type of stiffened beams was presented in consideration of the influence of loading onto the original beams. The calculation formula of stiffness was set up, which is solved in good agreement with the test results.%目前粘贴碳纤维布加固混凝土结构多采用环氧类有机胶,但其软化点过低,多为60～80℃.夏季由于气温高,一些地区混凝土桥梁结构表面温度常超过环氧类有机胶的软化点,用环氧类有机胶粘贴碳纤维布加固的混凝土结构难以满足耐高温要求.为此,选用600℃时强度不低于常温强度的碱矿渣胶凝材料粘贴碳纤维布,对经历承载能力极限状态的4根黏结预应力内置圆钢管桁架混凝土组合梁进行加固并进行受力性能试验,获得加固梁的受弯承载力试验值和二折线的跨中荷载-挠度变形曲线.基于试验结果,提出考虑原梁加载历程影响的此类加固梁受弯承载力计算方法,建立与试验结果吻合良好的刚度计算公式.
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