钢筋混凝土剪力墙剪切刚度计算的斜向腹筋桁架-拱模型

Inclined web tie truss-arch model for calculating effective shear stiffness of reinforced concrete shear walls

钢筋混凝土剪力墙构件腹板为双向配筋,其剪切刚度的传统计算方法忽略竖向钢筋的作用,低估了剪力墙构件的剪切刚度和受剪承载力。为考虑双向配筋对剪力墙剪切刚度的影响,提出等效斜向腹筋桁架-拱模型,与传统桁架-拱模型不同,模型中桁架作用的腹杆由斜向等效受拉钢筋及斜裂缝间的混凝土斜压杆构成,斜向等效钢筋的方向与裂缝处两个方向钢筋的合力方向一致。采用最小能量原理推导了斜向压杆倾角的理论算式,在已有试验数据的基础上,对压杆角度理论算式进行简化,提出了便于工程应用的简化算式。斜向开裂后剪力墙的有效剪切刚度为斜向腹筋桁架模型剪切刚度与拱模型剪切刚度的叠加,采用该模型分别对现有的剪力墙试件进行计算,并将计算值与实测值进行了比较,结果表明,提出的斜向腹筋桁架-拱模型可以较为准确地计算钢筋混凝土剪力墙构件斜向开裂后的有效剪切刚度。

The web of reinforced concrete （RC） shear wall is always reinforced bi-directionally, and the effect of vertical reinforcement is usually neglected in traditional methods for calculating its shear stiffness, which may underestimate the shear stiffness and the bearing capacity of RC shear walls. Considering the effect of bi-directional reinforcements, the equivalent inclined web tie truss-arch model was proposed to predict the effective shear stiffness of RC shear walls. Comparing to the traditional truss-arch model, the web truss action in the proposed model consists of equivalent inclined reinforcements and inclined compressive strut formed by the concrete between the inclined cracks. The orientation of equivalent inclined reinforcements coincides with the direction of resultant force of the orthogonal reinforcements in the crack plane. A closed-form formula for calculating the inclined crack angle was developed based on the minimum energy principle, and a simplified method applicable to practical engineering was also proposed on the basis of analysis of existing experimental data. The total shear stiffness of a fully diagonally cracked shear wall was calculated by summing the shear stiffness attributed by truss and arch models respectively. By applying the proposed model to predict the effective shear stiffness of the collected shear wall specimens and comparing the calculated and measured results, it is indicated that the effective shear stiffness of RC shear walls can be reasonably predicted by the proposed inclined web truss-arch model.