无腹筋混凝土短梁受剪承载力尺寸效应研究  

Study on size effect in shear strength of reinforced concrete short beams without web reinforcement

作　　者：李烨[1] 李哲[1] 易伟建[1] 陈晖[1] 张望喜[1] Li Ye;Li Zhe;Yi Weijian;Chen Hui;Zhang Wangxi(Hunan University,Changsha 410082,China)

机构地区：[1]湖南大学,湖南长沙410082

出　　处：《土木工程学报》2022年第12期1-12,共12页China Civil Engineering Journal

基　　金：国家自然科学基金(51878260,52008161)。

摘　　要：《混凝土结构设计规范》(GB 50010-2010)中对于短梁受剪承载力的计算没有考虑梁高的影响,而现有研究表明无腹筋梁的抗剪承载力随梁有效高度的增加而降低。梁受剪尺寸效应的作用机制并没有统一的认识。为研究无腹筋梁的受剪尺寸效应及作用机制,设计了2组8根无腹筋梁,高度为200~1600mm,剪跨比为2.0。三点简支加载。获取了荷载-挠度曲线、纵筋应变、混凝土应变、裂缝宽度、裂缝张开-滑移位移。计算了临界斜裂缝上的应力。搜集并分析了已有的梁受剪尺寸效应试验数据。研究结果表明:无腹筋短梁抗剪承载力存在尺寸效应;骨料咬合机制对无腹筋短梁抗剪承载力贡献有限;受压区未开裂混凝土的强度具有明显的尺寸效应,进而引起了梁抗剪承载力的尺寸效应;我国规范中短梁和不配置抗剪钢筋的单向厚板的抗剪承载力计算公式基本合理,但对部分短梁和大尺寸梁的受剪承载力预测可能偏于不安全,建议在可靠度校准的基础上适当调整。In the Chinese code ’Code for Design of Concrete Structures(GB 50010—2010)’, the influence of beam height on shear capacity of short beam is not considered.Existing researches, however, disclose that the shear capacity of beam without web reinforcement decreases with the increase of effective beam height, but no consensus on the mechanism of size effect in the shear failure of the beam has been achieved.In order to study the size effect and mechanism of reinforced concrete beams without web reinforcement, eight beams in two groups with the beam height of 200~1600 mm and the shear span ratio of 2.0 were designed for three-points loading tests, so that the load-deflection curve, longitudinal reinforcement strain, concrete strain, crack width and crack opening-slip displacement were observed.The stress on the critical diagonal crack was calculated, and the shear transfer mechanism of the beam without web reinforcement was analyzed.Additionally, the beam tests focusing on the size effect of the shear strength were collected and analyzed.The results disclose that the shear capacity of reinforced concrete short beams without web reinforcement has an obvious size effect.The contribution of aggregate interlock mechanism to shear capacity of the short beams without web reinforcement is small.The strength of uncracked concrete in compression zone has an obvious size effect, which further contributes to the size effect of shear capacity.The formulae for calculating the shear capacity of short beams and unidirectional thick slabs without shear reinforcement in GB 50010—2010 are reasonable, but the prediction of shear capacity of some short beams and large-size beams tends to be unsafe.Hence, it is suggested that appropriate adjustment should be made on the basis of reliability calibration.

关 键 词：受剪承载力 梁 尺寸效应 压杆-拉杆模型 深梁 

分 类 号：TU375.1[建筑科学—结构工程]