封一/四

为了解决FRP筋弹性模量低、剪切强度低和延性差的问题,设计和制备了多种规格的FRP-钢筋复合筋,并通过拉伸和剪切试验研究了含钢率和直径对其拉伸性能和剪切性能的影响。然后根据FRP-钢筋复合筋的性能特点及其增强混凝土构件的性能要求,提出了此类构件与相同钢筋混凝土构件的配筋总刚度相等的等效刚度设计法,并试验对比和分析了等承载力与等效刚度2种不同等效设计法设计的FRP-钢筋复合筋增强混凝土梁的受弯性能。结果表明:与FRP筋相比,FRP-钢筋复合筋的弹性模量、延性和剪切性能都明显提高。FRP-钢筋复合筋的弹性模量可达到FRP筋弹性模量的3倍以上,这为等效刚度设计法的实现提供了良好基础。等效刚度设计的FRP-钢筋复合筋增强混凝土梁具有和钢筋混凝土梁接近的屈服前受力性能(挠度和最大裂缝宽度)和良好的延性,并且可使其极限承载力提高30%。即等效刚度设计的此类构件不仅可满足安全性和适用性要求,而且具有更大的承载力储备和更好的耐久性。由于等效刚度设计法可参考现有的钢筋混凝土结构设计规范进行设计,其有望为此类构件和结构设计与工程应用提供简便适用的计算分析和设计方法。

FRP-steel Composite Bar and the Equal-stiffness Design Method for Its Reinforced Concrete Members

To address the issues of low elastic modulus, low shear strength, and weak ductility of fiber-reinforced plastic (FRP) bars, several types of FRP-steel composite bars were designed and manufactured. The effects of the steel ratio and diameter on the tensile and shear behaviors were investigated by tensile and shear tests. According to the properties of the FRP-steel composite bar and performance requirements of the members, an equal-stiffness design method-meaning that the total reinforcement stiffness of members is equal to that of steel bar reinforced concrete (RC) members-was developed. Moreover, the flexural behaviors of beams designed using equal-capacity and equal-stiffness methods were tested and compared. The results show that compared with the FRP bar, the elastic modulus, ductility, and shear performance of the FRP-steel composite bar are significantly improved. The elastic modulus of the FRP-steel composite bar can reach more than three times that of the FRP bar, which provides an excellent foundation for the equal-stiffness design method. Furthermore, compared with steel bar RC beams, the equal-stiffness-designed FRP-steel composite bar RC beam has a similar pre-yield mechanical behavior (deflection and maximum crack width), good ductility, and a 30% larger ultimate capacity. This indicates that the members designed with equal stiffness can not only satisfy the requirements of safety and serviceability, but also have better capacity reserve and durability. By using the equal-stiffness design method, the design code of steel bar RC structures can be followed, potentially providing a simple and applicable design method for the design and application of FRP-steel composite bar RC structures.