钢筋及BFRP筋混凝土深受弯构件受剪性能及尺寸效应对比分析:试验研究

Comparative analysis of shear behavior and size effect of RC and BFRP-RC deep flexural members:experimental study

文章旨在研究并对比钢筋及BFRP筋(玄武岩纤维增强筋)混凝土深受弯构件受剪性能及尺寸效应的异同,对4根钢筋混凝土深受弯构件及4根BFRP筋混凝土深受弯构件(梁高为300~1200mm)进行了剪切破坏试验。对比分析了荷载-位移曲线、斜裂缝宽度、混凝土应变、纵筋应变及腹筋应变随结构尺寸变化的发展趋势。揭示了钢筋及BFRP筋混凝土深受弯构件抗剪强度尺寸效应规律,并分析了设计规范和计算方法的适用性。研究表明:(1)BFRP筋混凝土深受弯构件的极限荷载约为钢筋混凝土深受弯构件的0.3~0.5倍,而挠度约为钢筋混凝土深受弯构件的1.4~1.7倍;(2)梁高从300mm增至1200mm时(试验梁的水平及竖向腹筋率均为0.51%),钢筋混凝土深受弯构件的名义极限抗剪强度下降34.0%,而BFRP筋混凝土深受弯构件下降45.7%;(3)对于大尺寸构件的抗剪承载力,设计规范的计算结果安全储备不足,未能合理考虑尺寸效应;(4)提出的尺寸效应理论公式可以定量描述结构尺寸对钢筋及BFRP筋混凝土深受弯构件名义极限抗剪强度的影响。

This work aims at studying and comparing the shear performance and size effect of RC deep flexural members and BFRP-RC(Basalt Fiber Reinforced Polymer-reinforced concrete)deep flexural members.Shear failure experiments were carried out on 4 RC deep flexural members and 4 BFRP-RC deep flexural members(beam heights ranging from 300mm to 1200mm).The development trends of the load-deflection curve,diagonal crack width,concrete strain,longitudinal reinforcement strain,and web reinforcement strain with the change in structure size are compared and analyzed.The size effect laws in the shear strength of RC deep flexural members and BFRP-RC deep flexural members are revealed,and the applicability of design codes and calculation methods is analyzed.The results show that:1)The ultimate load of BFRP-RC deep flexural members is about 0.3~0.5 times that of RC deep flexural members,and the deflection is about 1.4~1.7 times that of RC deep flexural members;2)When the beam height increases from 300 mm to 1200 mm(the horizontal and vertical web reinforcement ratio are 0.51%),the nominal ultimate shear strength of the RC deep flexural member decreases by 34.0%,while the BFRP-RC deepflexural member decreases by 45.7%;3)For the shear capacity of large-sized members,the safety reserves of the calculation results of design codes may not be sufficient and the size effect may not be reasonably considered;4)The theoretical formula proposed by Jin et al.can quantitatively describe the influence of structural size on the nominal ultimate shear strength of RC and BFRP-RC deep flexural members.