Analysis of Multi-Tendon Friction-Based Composite Anchorage Device for CFRP Cables and Its Anchorage Mechanism

Abstract

Carbon fiber-reinforced polymer (CFRP) cables are anticipated to be employed in larger, longer, and more durable structures in the engineering field. However, its anchorage devices and mechanism should be appropriately developed and improved. At present, mainly relying on the adhesive force, most anchorage devices may lose their efficiency because of adhesive aging and failure or the slip of an individual tendon. A friction-based composite anchorage device with an integrated bearing of inner cone filler (i.e., load transfer media (LTM)) bonding and a single extruding anchor is proposed, and the anchorage mechanism is examined for Φ7 CFRP cables of strength 2400 MPa. Firstly, sufficient conditions for anti-slip failure of CFRP tendons in the anchorage zone are derived by assuming uniform LTM bonding. The obtained results reveal that the smaller inner pore size of the barrel leads to higher efficiency. Additionally, the maximum efficiency depends on the friction coefficient of the contact surface, the inner cone angle of the barrel, and the diameter and quantity of the CFRP tendons. The necessary conditions for the safety of the CFRP tendon anchorage zone are carefully obtained based on the Tsai–Wu failure criterion. It is concluded that the compressive stress of CFRP tendons in the anchorage zone should gradually increase from the load-bearing end to the no-loading end. Additionally, the relations among the anchorage efficiency coefficient and the CFRP tendon diameter d, the anchorage length l, the dip angle of LTM external conical surface α, and the friction angle β are derived based on the equivalent failure principle. The CFRP cables of four specifications (i.e., with Φ12, Φ19, Φ37, and Φ121 tendons) are designed under theoretical guidance, and eight static tests are carried out for more verification studies. The test results indicate that the anchorage efficiency coefficient of designed anchorage devices can be over 90%, and even up to 96.8%. Further, the failure modes are divergent destruction, which verifies the reliability of friction-based anchorage devices and provides a solid theoretical foundation for the design and engineering applications of CFRP cables.

Experimental Investigation of Fatigue Capacity of Bending-Anchored CFRP Cables

“…To overcome these problems, a straight tube filled with potting compound (a mixture of modified high-temperature cured epoxy resin, cast stone powder, and steel grit) was used in the bonding section to reduce the tensile stress transferred to the friction section. This was useful to avoid the compression-shear fracture of the CFRP rod in accordance with the damage fracture criteria used in unidirectional FRP materials [16].…”

“…This effect may aggregate premature fiber failure, resulting in compression-shear fracture of CFRP rods within the anchoring system. Consequently, the bending extent of a CFRP rod (closely associated with the level of additional shear) has been studied [6,[16][17][18], and the maximum allowable bending extent has been determined based on the tensile test results of a CFRP rod anchored in the bending mode, with strength loss limited to 5% to ensure anchoring performance [18].…”

“…In contrast to UBC testing of CFRP cables, experimental research on the fatigue resistance of CFRP cables requires a significant amount of time and money. Consequently, most CFRP cable fatigue tests are based on practical engineering and follow the testing standards established for steel cables [7,[12][13][14]16]. Due to the excellent fatigue resistance of CFRP rods, almost all tested CFRP cables reported in the literature do not exhibit any symptoms of fatigue fracture resulting in the fatigue resistance capacity of these cables, which has mainly been evaluated on the basis of UBC post-fatigue loading.…”

Numerical Investigation on the Structural Behavior of a Short-Span Cable-Stayed Bridge with Steel and CFRP Hybrid Cables

“…Due to the orthotropic characteristics of CFRP materials, the stress concentration caused by traditional cone anchors clamping the anchorage region can lead to premature failure of CFRP tendons. Therefore, some scholars have improved the filling and structure of CFRP tendon anchorage systems to enhance the bearing capacity of CFRP cable anchorage [24][25][26][27][28].…”

A Novel Smart CFRP Cable Based on Optical Electrical Co-Sensing for Full-Process Prestress Monitoring of Structures

“…Carbon-fiber-reinforced polymer (CFRP) is a kind of composite material with many superior performances, such as high tensile strength, light weight, anti-corrosion, good fatigue, and creep performance [3]. Thus, CFRP cable has great potential to replace steel cable in prestressed concrete structures [4][5][6][7]. However, the CFRP cables are composed of anisotropic tendons.…”