Comparison of Prestressing Methods with CFRP and SMA Materials in Flexurally Strengthened RC Members

Abstract

Over the years, prestressing concrete has become a well-known technique to improve the ultimate and serviceability state of RC members. Besides steel reinforcement, relatively new materials such as carbon fiber reinforced polymers (CFRP) or especially shape memory alloys (SMA) can be used to active strengthening. The main scope of this paper is to compare various prestressing methods using carbon composites and memory steel alloys. A description of SMA, shape memory effect, its utilization for prestressing, and CFRP materials are presented in the paper. Moreover, current state-of-the-art developments in the field of both materials, considering prestressing systems and available anchorage, material behavior, creep and stress relaxation, durability issues, thermal compatibility with concrete, and fire behavior, are described. A general revision of previous studies based on flexural strengthening using both materials is conducted and the selected results of these studies are briefly presented. The behavior of RC beams after strengthening with mentioned techniques is compared and discussed. Selected on-site applications are described to confirm the feasibility and practicality of the strengthening systems. Finally, the main advantages and disadvantages of CFRP and SMA materials for prestressing concrete structures are summarized and further recommendations for the future research are listed.

Testing and Evaluation of Flexural Tensile Strength of Prestressed CFRP Cables

“…Therefore, we needed theoretical calculations to predict the error envelope range and thus the ultimate performance. According to the theoretical calculation model (Equation (7)) established in Section 2.2 , the influencing factors of the residual tensile strength were the radius of the CFRP tendon r , the elastic modulus E , the tensile strength f , the bending radius R of the bogie, and the numerical range of parameters of common reinforcement CFRP tendons [ 11 , 12 , 44 , 45 ], with r at 3–7 mm, f at 2100–2500 MPa, and E at 120–160 GPa.…”

“…In the 1980s, Japan, the United States, and other countries began to study its engineering applications [ 9 , 10 ] and the U.S. Specification ACI 440.4R-04 [ 11 ] recommends the use of CFRP cables as a prestressing material. However, in potential practical engineering applications, such as the flexural reinforcement of simply supported beams with external prestressed CFRP cables [ 12 , 13 , 14 ] and CFRP cables spanning cable saddles of suspension bridge [ 15 , 16 , 17 ], CFRP cables need to be bent at a certain angle [ 18 , 19 , 20 ]. Traditional materials tend to use steel strands and cables as members, which have less performance compromise from bending due to the superior ductility and plastic deformation of steel.…”

Numerical Simulation of the Bearing Capacity of Variotropic Short Concrete Beams Reinforced with Polymer Composite Reinforcing Bars

“…However, it should be noted that, as has already been proven by us and other authors earlier, it is certainly impossible to achieve a significant solution to the problem and eliminate all risk factors by improving the reinforcing elements alone [ 18 , 19 , 20 , 21 , 22 , 23 ]. Of course, such tasks should be approached in a comprehensive manner, and building elements made of heavy concrete with various reinforcing elements should be evaluated as a system operating in conditions of a certain synergy [ 24 , 25 , 26 , 27 , 28 , 29 ]. Such synergy, as we have already established earlier, can be complex reinforcement, namely, fiber plus reinforcing bars, improved concrete characteristics due to their nanomodification or the same fiber reinforcement with fibers [ 30 , 31 , 32 , 33 , 34 ].…”

“…Mineral impregnated carbon fiber composites are a new type of reinforcement for construction. Compared to steel reinforcement, carbon fiber reinforcement has a much higher tensile strength and a significantly lower weight [ 22 , 24 , 31 , 33 , 35 , 38 , 39 , 41 , 42 , 43 , 44 , 47 , 49 , 51 , 55 , 59 ]. At present, the technology of reinforcing concrete bending elements with carbon fiber sheets is popular [ 44 , 59 ].…”

Numerical Model for Flexural Analysis of Precast Segmental Concrete Beam with Internal Unbonded CFRP Tendons

“…Compared with monolithic beams [20,[24][25][26][27], the PSCB-IUCFRP system showed more complicated flexural behaviors, including the discontinuous behaviors of open joints and the unbonded phenomenon of the internal unbonded CFRP tendons. Le et al [28] and Tran et al [29] conducted the only numerical model for the PSCB-IUCFRP.…”