新旧混凝土结合面剪切强度参数分析和计算研究

Parameter Analysis and Calculation Investigation of Shear Strength of Bonding Interface between New and Old Concrete

新旧混凝土结合面的抗剪强度是装配式混凝土结构和混凝土结构加固等领域重点关注的问题.基于搜集、整理的新旧混凝土结合面(以下简称结合面)的剪切试验数据库(含439个试件),对GB 50010―2010、ACI 318―19、Eurocode 2、PCI7th四个规范所给结合面抗剪建议计算式进行对比分析.结果表明:在各参数的影响下,ACI结果的保证率表现最好,而Eurocode 2计算强度的拟合效果最好;在结合面宽度达到300~400 mm时,GB 50010―2010的表现最好,但安全富余均较低,相对误差最大达到9倍.对数据库进行参数分析,发现结合面剪切强度τ_(exp)存在尺寸效应,与结合面的沿剪切方向尺寸关联较大;且τ_(exp)与夹紧力ρfy有较好的相关性.基于分析结果,根据叠加计算理论,对计算式提出建议和修正:分析引入尺寸效应系数β;同时修正了摩擦系数μ;应用了数据库拟合的销栓力分段函数,极大值为6.6 MPa.经对比验算证明,修正计算式在有无插筋及各种粗糙度情况下的误差最小,拟合效果最好,可为工程应用提供参考.

The shear strength of the bonding interface between new and old concrete is a critical concern in precast concrete structures and the strengthening of concrete structures.Shear calculation formulas of the bonding interface between new and old concrete given by four codes(GB 50010―2010,ACI 318―19,Eurocode 2,and PCI7th)are compared and analyzed based on the test date of shear tests(containing 439 specimens)of bonding interface between new and old concrete(to be referred to as the interface).The results show that under the influence of each parameter,the assurance rate of ACI calculation results is the best,and the calculation results of Eurocode 2 fit shear tests best.When the size range of the interface is 300~400 mm,the performance of GB 50010―2010 is best,but both of them are not safe,and the maximum relative error is about 9.According to the parameters analysis results of the database,the shear strengthτ_(exp) is affected by the size effect and is closely related to the size of the interface along the shear direction.Andτ_(exp) has a good correlation with the clamping stressρfy.Based on the analysis results,the shear strength calculation formula is modified according to the superposition calculation theory.The modification includes that the coefficientβis introduced by analyzing the size effect;the friction coefficientμis modified;the piecewise function of dowel resistance fitted by the database is applied,and its maximum value is 6.6 MPa.It is proved by comparative calculation that the error of the modified formula is the smallest,and the fitting effect is the best when the interface is with or without rebar and has various roughness.Moreover,it can be used as a reference for applications in civil engineering.