Abstract
Precast segmental prestressed concrete beams (PSBs) have been widely used in many elevated highway bridge projects around the world. Steel tendons at joint locations, however, are vulnerable to corrosion damages, which cause deteriorations and in extreme cases lead to the collapse of the whole structures. This study experimentally investigates the use of carbon fibre-reinforced polymer (CFRP) tendons as an alternative solution for the PSBs to tackle the corrosion issue. Four large-scale segmental T-shaped concrete beams with internal bonded or unbonded tendons and dry or epoxied joints were built and tested under four-point loading. The test results indicated that CFRP tendons showed satisfactory performances therefore could replace steel tendons for the use in PSBs. All the tested beams exhibited excellent load-carrying capacity and ductility. Tendon bonding condition greatly affected the flexural performance of the segmental beams. Joint type had only a slight effect on the load-carrying capacity and ductility of the beams, but significantly affected the beams’ initial stiffness. Unbonded tendons experienced an evident reduction in the tendon strength at the ultimate stage as a consequence of the loading type, harping effect and joint opening. Both AASTHO-1999 and ACI 440.4R-04 predicted well the tendon stress, thus the load-carrying capacity of the beams with bonded tendons, however, the accuracy significantly reduced for the cases with unbonded tendons. Similarly, the codes did not well estimate the deformation capacity of the prestressed beams with unbonded tendons. An empirical formula is proposed to predict the deflections of beams with unbonded tendons, which yields very close predictions to the experimental results.
Highlights
Precast segmental prestressed concrete beams (PSBs) have been widely used in many bridges around the world, especially in the United States, France, Spain and China over the past four decades
Beams C1 and C2 with bonded tendons failed by rupture of carbon fibre-reinforced polymer (CFRP) tendons without any concrete spalling on the top while Beams C3 and C4 failed by concrete spalling on the compressive side and CFRP tendons rupturing at the bottom
It is observed that the beams with bonded tendons showed much higher strengths but lower ductility compared to the beams with unbonded tendons
Summary
Precast segmental prestressed concrete beams (PSBs) have been widely used in many bridges around the world, especially in the United States, France, Spain and China over the past four decades. Time-saving and economic benefits are among the advantages that made the PSBs very well suited to the construction of the medium to moderate long-span bridges [1]. Steel tendons are used as the only prestressing material to join individual segments to form completed bridge spans. Corrosion problems of the steel tendons at segment joints, are a great concern of the application of PSBs, in the places with highly aggressive environmental conditions. Inappropriate design choices and poor quality construction of the corrosion protection systems are the main factors that have been contributing to the corrosion-induced damages, which greatly increase and lifetime maintenance costs of such bridges. The whole structure might even completely collapse as reported in previous studies [2,3,4]
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