Zanuy Carlos, Irache Pedro Javier, García-Sainz Alejandro
Department Continuum Mechanics and Structures, Universidad Politécnica de Madrid, ETS Ingenieros de Caminos, 28040 Madrid, Spain.
Materials (Basel). 2020 Dec 24;14(1):47. doi: 10.3390/ma14010047.
A significant increase of the use of high-performance fiber-reinforced concrete (HPFRC) to strengthen reinforced concrete structures (RC) has been noted for the past few years, thereby achieving composite RC-HPFRC elements. Such a technique tries to take advantage of the superior material properties of HPFRC in the ultimate and service load regimes. Many of the existing works on RC-HPFRC elements have focused on the strength increase at the ultimate load state and much less effort has been devoted to the serviceability response. The in-service performance of RC structures is governed by the behavior of the tension chord, which determines the crack pattern (crack widths are critical for durability) and deformations. The presence of HPFRC is supposed to improve serviceability due to its strain-hardening and tension-softening capacities. In this paper, the experimental analysis of composite RC-HPFRC tension members is dealt with. Specimens consisting of a RC tie strengthened with two 35 mm thick HPFRC layers have been subjected to loads in the service range so that the deformational and cracking response can be analyzed. The HPFRC has been a cement-based mortar with 3% volumetric amount of short straight steel fibers with a compressive and tensile strength of 144 MPa and 8.5 MPa, respectively. The experiments have shown that RC-HPFRC has higher stiffness, first cracking strength and reduced crack widths and deformations compared to companion unstrengthened RC. To understand the observed behavioral stages, the experimental results are compared with an analytical tension chord model, which is a simplified version of a previous general model by the authors consisting of 4 key points. In addition, the influence of time-dependent shrinkage has been included in the presented approach.
在过去几年中，高性能纤维增强混凝土（HPFRC）在加固钢筋混凝土结构（RC）方面的应用显著增加，从而形成了钢筋混凝土-高性能纤维增强混凝土组合构件。这种技术试图在极限荷载和使用荷载状态下利用高性能纤维增强混凝土优越的材料性能。许多关于钢筋混凝土-高性能纤维增强混凝土构件的现有研究都集中在极限荷载状态下的强度提高上，而对使用性能响应的关注则少得多。钢筋混凝土结构的服役性能由受拉弦杆的性能决定，受拉弦杆决定了裂缝模式（裂缝宽度对耐久性至关重要）和变形。高性能纤维增强混凝土的存在因其应变硬化和拉伸软化能力而被认为可以改善使用性能。本文对钢筋混凝土-高性能纤维增强混凝土组合受拉构件进行了试验分析。由两层35毫米厚的高性能纤维增强混凝土加固的钢筋混凝土系杆组成的试件在使用荷载范围内承受荷载，以便分析其变形和开裂响应。高性能纤维增强混凝土是一种水泥基砂浆，体积含量为3%的短直钢纤维，抗压强度和抗拉强度分别为144兆帕和8.5兆帕。试验表明，与未加固的对比钢筋混凝土相比，钢筋混凝土-高性能纤维增强混凝土具有更高的刚度、初裂强度，并且裂缝宽度和变形更小。为了理解观察到的行为阶段，将试验结果与一个分析受拉弦杆模型进行了比较，该模型是作者之前一个由4个关键点组成的通用模型的简化版本。此外，本文方法还考虑了时效收缩的影响。
