考虑弯剪相关性的钢筋混凝土受弯构件承载力计算

钢筋混凝土受弯构件中,弯剪承载力存在相关性。中国规范GBJ10—89,GB50010,JTJ023—85和JTG D62—2004,以及美国规范ACI318基本沿用了相同的思路,未充分考虑弯剪相关性,受弯构件纵筋和箍筋用量分别按正截面承载力和斜截面承载力单独计算确定,仅通过剪跨比分析了在集中荷载作用下的独立梁的弯矩对抗剪承载力的影响。在分析GB50010和ACI318的强度准则中隐含应力层次的弯剪相关性和承载力公式中剪跨比影响的基础上,提出了考虑弯剪相关性的弯剪承载力修正公式。通过典型算例,分析了不同参数下修正公式与规范公式的设计配筋量,比较了抗弯和抗剪可靠指标的变化,并基于GB50068—2001的目标可靠指标要求,探讨了考虑弯剪相关性的必要性。

Calculation of bearing capacity of reinforced concrete bending members considering correlation between bending and shearing

There is correlation between flexural capacity and shearing capacity in RC(reinforced concrete) bending members. Chinese code GBJ10-89, GB50010, JTJ023-85 and JTG D62-2004, as well as American code ACI318 basically follow the same guidelines. They do not consider the bearing capacity correlation between bending and shearing sufficiently. The amount of longitudinal reinforcement and stirrup of a RC bending member is respectively calculated according to its normal section bearing capacity and oblique section bearing capacity. Only for independent beams under concentrated load, the influence of bending moment on shearing bearing capacity are considered through the shear-span ratio. Based on the analysis of the implicit correlation of bending and shearing from GB50010 and ACI318 strength criteria in stress level, and the effect of shear-span ratio in bearing capacity code formula, a modified formula considering the correlation of bending and shearing is put forward. By introducing several typical examples, the amount of reinforcement with different parameters is calculated with the modified formula and the code formula, respectively, and the reliability indexes of the two formulas are compared. Moreover, according to the target reliability index requirements of Chinese code GB50068-2001, the necessity of considering the correlation of bending and shearing in RC bending member is discussed.