基于名义拉应力法的预应力混凝土结构的裂缝控制

CRACK CONTROL OF PRESTRESSED CONCRETE STRUCTURES BASED ON NOMINAL TENSILE STRESS METHOD

根据现行规范的裂缝宽度的计算公式,自编程序计算有黏结和无黏结部分预应力混凝土结构对应于特征裂缝宽度的名义拉应力值,并考虑了截面高度、保护层厚度、混凝土强度等级、非预应力筋配筋率、非预应力筋直径和预应力度等参数对一定裂缝宽度下名义拉应力值的影响,归纳各参数对名义拉应力值的影响系数。对于各参数对名义拉应力值的综合影响系数,可以将各影响系数相乘得到。最后以实际工程为例,比较了用本方法进行裂缝控制和用规范公式计算结果的差异。算例分析表明,基于名义拉应力法的预应力混凝土结构的裂缝控制方法是一种简便、可靠的裂缝控制方法。

Based on the formula of the crack width in the present code, the nominal tensile stress value corresponding to the limit of crack width was studied. The influences of cross section height, the cover thickness, concrete strength grade, non-prestressed reinforcement ratio, diameters of non-prestressed reinforcement and prestress degree on the normal tensile stress of the given crack width were also discussed. Then the influence coefficients of these parameters on the normal tensile stress values were concluded. The comprehensive influence coefficient on the normal tensile stress was obtained by multiplication of the single influence coefficient of the panoeters. In the end, an example was calculated by using the method of normal tensile stress and the formula of the code. The result shows that the method of normal tensile stress is a simple, convenient and creditable method on the crack control of the prestressed concrete structures.