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In this study, a parallel-tendon and dispersed-tendon cable anchor system (CAS) for high-strength carbon-fiber-reinforced polymer (CFRP) cables were investigated based on a previously developed load transfer component (LTC). The static behaviors of three cables comprising 37 CFRP tendons with a 7-mm tendon diameter were experimentally evaluated and the failure mechanism of the cables was numerically revealed. The parallel-tendon cable exhibited an integral pull-out failure caused by a shear failure of the LTC, while the dispersed-tendon cables showed a mixed shear and compressive failure caused by an excessive axial tensile strain difference and wedge action of the LTC. From loading end to free end, the shear stress of the LTC first increased rapidly, and then increased slowly with fluctuations, and finally peaked the free end. The experimental and numerical results agreed well in the axial cable strains and shear stresses of the LTC. By optimizing parallel tendons into dispersed tendons in the anchor zone, the anchor efficiency of the cable was improved from 60% to 91%. Correspondingly, the cable force was improved from 2,684 to 4,070 kN. The increase in the anchor length and decrease in the conical angle can decrease the stress concentration of the dispersed-tendon CAS. [ABSTRACT FROM AUTHOR]

More sustainable precast concrete structural elements are emerging from the research community utilizing high-strength, selfconsolidating fiber-reinforced concrete (HPSCC) reinforced with noncorroding prestressed carbon-fiber-reinforced polymer (CFRP). An example of this is a new type of precast CFRP pretensioned HPSCC panel intended as load-bearing beams or columns for use in building envelopes. Such elements have recently been applied to architectural façade elements in Europe. A key issue in the implementation of these elements as load-carrying members in buildings is demonstrating satisfactory performance in fire. It is well known that the bond between FRP reinforcing bars and concrete deteriorates at elevated temperatures. It is also known that high-strength concrete is susceptible to explosive spalling when subjected to fire. Reductions in FRP reinforcement tensile and bond strength during fire, effects on the load-bearing capacity of prestressed concrete structures, and the explosive spalling response of HPSCC during fire all remain largely unknown. This paper provides insights into the fire behavior of CFRP prestressed HPSCC slabs through an experimental study on thin slabs exposed to a standard fire while subjected to sustained service loads. It is shown that the fire resistance of these elements is governed by fire-induced spalling or, if spalling is prevented by the use of high dosages of polypropylene microfibers in the concrete, by thermal splitting-crack-induced bond failure of the CFRP tendons in their prestress transfer zone. Neither reductions in tensile strength of the tendons nor reductions in bond strength due to resin softening at high temperature appeared to play critical roles for the tests described in this paper. Key areas for future research are highlighted. [ABSTRACT FROM AUTHOR]

A new model is presented for calculating the axial strain of carbon fiber-reinforced polymer (CFRP)-confined concrete columns. An energy-balance approach is introduced to establish a relationship of the energy absorption between a confined concrete column and CFRP. The proposed model was verified using a large database collected from 167 CFRP-confined plain concrete specimens. This database contains 98 circular specimens with diameters ranging between 100 and 152 mm, and 69 square specimens having a side length ranging between 100 and 152 mm. The database covers unconfined concrete strengths from 20 to 50 MPa. The proposed model shows very good correlation with the experimental results. In addition, the proposed model also provides a comparative prediction of the strain of CFRP-confined concrete columns in two extreme cases, i.e., (1) insufficient confinement, and (2) heavy confinement, which are not usually well predicted by other models. [ABSTRACT FROM AUTHOR]