Mode I fatigue crack arrest in tensile steel members using prestressed CFRP plates

Abstract

Numerous studies in the literature have shown that the strengthening of steel members using carbon fiber reinforced polymer (CFRP) composites can significantly extend the fatigue life of these structures. However, not enough attention has been focused on the potential of prestressed CFRP reinforcements for fatigue crack arrest in such members. In the current study, a simple analytical model is proposed to calculate the required prestressing level in the CFRP reinforcements in order to arrest the propagation of an existing fatigue crack in tensile steel members. Furthermore, a novel mechanical unbonded system is developed to anchor the high prestressing forces in CFRP reinforcements to the steel substrate using friction. A set of fatigue tests are performed on unstrengthened and strengthened precracked steel plates to verify the proposed model. The experimental results of the current study showed that the application of nonprestressed ultra-high modulus CFRP plates as externally bonded reinforcements can increase the fatigue life of precracked steel plates by a factor of 4.3. However, fatigue crack arrest is only possible when prestressed CFRPs of a certain prestressing level are used. Based on the analytical, numerical, and experimental results of the current study, it can be concluded that existing fatigue cracks in tensile steel members can be arrested using the proposed prestressed unbonded reinforcement system with the initial prestressing level calculated using the proposed model. In addition, some design recommendations are provided for fatigue crack arrest in practical cases.

Mixed mode I/II fatigue crack arrest in steel members using prestressed CFRP reinforcement

“…(3) has within 1% accuracy for 2a/w ≤ 0.8 [54]. It is worth mentioning that the explicit derivation of f(a,w) is available for a wide range of the member's geometry [55], while it may be determined through a finite element (FE) simulation for more complicated geometries, where no analytical solution exists [38].…”

“…A number of experimental studies have demonstrated the excellent performance of prestressed CFRP reinforcements for fatigue crack prevention [32,33] or fatigue crack arrest [34][35][36][37][38] in steel members subjected to the mode I loading condition. However, the practical application of prestressed bonded CFRPs for the strengthening of existing steel members has been quite limited so far [39].…”

“…Recently, the authors have demonstrated that an existing mode I fatigue crack in a tensile steel member can be safely arrested by providing sufficient prestressing force in the CFRP reinforcements; the required level of prestressing can be determined through the proposed analytical model [38]. However, to the best knowledge of the authors, to date no research has been conducted on the mixed mode I/II fatigue crack arrest in steel members by using prestressed reinforcements.…”

Blind prediction of FRP repairs for multiaxial fatigue cracks on Hydraulic Steel Structures

“…In general, research efforts on retrofitting steel elements has examined the following areas: (1) repair of naturally deteriorated steel girders, (2) repair of an artificially notched girder or steel plates to simulate fatigue cracks, (3) strengthening an intact section to increase the girder stiffness and flexure capacity, and (4) increasing the composite action between the steel girder and concrete deck in bridge application. Very few studies have been conducted on fatigue crack propagation in CFRP-repaired large specimens representing real structural members [16][17].…”

Performance Evaluation of a Carbon Nanotube Sensor for Fatigue Crack Monitoring of Metal Structures

“…In the United States (U.S.), an estimated 3% of the gross national product [4][5][6] is spent on replacing, repairing, inspecting, and/or monitoring fatigue damaged structures. Conventional fatigue repair techniques, including drilling crack-stop holes [7,8], adding bolted steel plates [9,10], and adhesively bonding fiber-reinforced polymer (FRP) sheets [11][12][13], often fail to reliably arrest a fatigue crack, and may result in crack re-initiation, which may trigger catastrophic failure.…”