Flexural Strength of Prestressed Concrete Beams with Tendon wrapped by Plastic sheets (original) (raw)
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Composite Structures, 2019
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 loadcarrying 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
Flexural Design of Prestressed Concrete Beams Using FRP Tendons
Fiber Reinforced Polymer (FRP) tendons are being considered for design in structures exposed to aggressive environments or where non-metallic properties are desired. FRP tendons require considerable attention to detail during the design process. This paper presents a unified approach for the flexural design of beams with FRP tendons. Equations for flexural strength are presented, failure modes are defined, calibrations with test data are presented, and strength reduction factors are recommended. A test program validates the design approach and provides some serviceability data. Conclusions from the test program and design recommendations are provided.
Engineering Structures, 2018
This study investigates the use of carbon fibre reinforced polymer (CFRP) tendons on precast segmental beams (PSBs) to tackle the corrosion problems which are likely to occur at joint locations of PSBs prestressed with steel tendons. Up to date, the use of CFRP tendons was extensively documented for monolithic beams while their application on PSBs has not been reported yet. Three precast segmental T-section beams including two beams with unbonded CFRP and one with steel tendons were built and tested under four-point loads in this study. The test results showed that CFRP tendons can be well used to replace the steel tendons on PSBs. The beams with CFRP tendons demonstrated both high strength and high ductility as compared to the beam with steel tendons. However, the stresses in the unbonded CFRP tendons at ultimate loading conditions of the tested beams were low, ranging from only about 66% to 72% of the nominal breaking tensile strength. The type of joints i.e. dry and epoxied, greatly affects the initial stiffness of the beams but has no effect on the opening of joints at ultimate loading stage. Moreover, a comprehensive examination on four existing code equations to predict the stress in the unbonded tendons showed that the four examined codes predicted well
Civil and Environmental Research, 2019
Slab without beams cause bending cracks in the tensile region at a low loading level. One way to overcome these weaknesses is to provide a pre-concentric or eccentric initial bias style. In this study, we wanted to compare the performance of prestressed concrete slabs in terms of cross-sectional strength capacity and rigidity of concrete slab without prestressing through experiments. Objects that were tested without prestressing were made 1 piece, namely P1, and objects that were tested with prestressing were 3 piecesnamely P2 with 2 tendons, P3 with 3 tendons, and P4 with 4 tendons. The dimensions of each object tested are 100 × 40 × 8 cm and all of them are designed with concrete qualityf'c = 30 Mpa. The tendon usedis 8 mm plains teel that is pulled by tightening the nuts at both ends, with a parabolic profile shape and eccentricity value in the middle span of 1.5 cm. From the test results obtained a very significant increase in the crosssectional strength capacity of specimens P2, P3 and P4 against P1. The increase in peak load that can be borne by 192.18% is for P2, 286.54% is for P3, and 383.00% is for P4. It also happened to increase the peak bending moment which can be borne by 161.57% for P2, 241.05% for P3, and 322.68% for P4.
Crack Propagation of Concrete Beams Prestressed with Single Strand Tendons
Journal of Civil Engineering Research, 2014
Wheel abnormality intensifies impact characteristics of train loads on railway concrete ties. Concrete ties are commonly prestressed with single or multiple tendons. This paper presents experimental studies on crack propagation of prestressed concrete ties with single steel tendons subjected to impact loads. The presented study includes the effect of supplementary fiber reinforcement using polypropylene fibers on crack arrest, in terms of fiber type and content by volume. Concrete ties are modeled as flexural beams subject to four-point loading system. A mass dropped from predetermined height simulated the wheel impact loads. Experimental results include crack patterns, dimensions, and accompanied loads. The concrete beams reinforced with fibers experienced a delay in crack growth in both length and width. Further, the fiber reinforced beams had smaller initial crack length in comparison to beams with no fiber reinforcement.
Construction and Building Materials, 1998
. The use of fiber reinforced polymer FRP composites is significantly growing in construction and infrastructure applications where durability under harsh environmental conditions is of great concern. Aramid fiber composite rectangular tendons have potential as reinforcements for concrete structures. Recent studies on prestressed concrete beams have showed brittle flexural failure due to the elastic rupture of the FRPs; however, for the maintenance and hazard anticipation of structures, the brittle failure mode is undesirable. In order to improve the ductility, a series of flexural tests was carried out on beams with bonded Ž . andror unbonded rectangular rebars, or with additional non-tensioned regular reinforced rebars. Test results showed that ultimate deformation in the beam with unbonded rectangular rebars was 250% that of the beam with bonded rectangular rebars, while the loading capacity was 85%. The additional placement of reinforced rectangular rebars produced a 450% higher ultimate deformation. It was found that the ductility was significantly enhanced by the use of combination of bonded and unbonded rectangular rebars. ᮊ
Engineering Structures, 2013
This paper presents a brief review of equations proposed for calculating the increase in stress in external prestressing tendons at the ultimate stage. The validity of these equations to calculate the ultimate stress of external tendons in continuous beams was checked. Then, a simple method to calculate the stress in external tendons for continuous beams with or without symmetrical loading from the deformation of the strengthened member is presented and discussed. The steps of this method are simple and can be used at any stage of loading. Experimental results of 37 beams obtained from the published literature were used to check the accuracy of the proposed method. Several factors such as tendon type, internal and external prestressing forces, loading type, the presence of non-prestressed steel, tendon eccentricity/depth ratio, span/depth ratio, beam type, concrete strength, deviators number and deviator location were covered. The comparison between the actual and the calculated results showed good agreement.
Analysing the Route of PCI Girder-Type Prestressed Concrete Tendons
International Journal of Science and Research (IJSR)
This paper will analyse the middle span of the 31m-in-length bridge. The calculation stages undertaken here were to design the form and dimensions using PCI Girder-Type Prestressed Concrete, to determine the prestress force, eccentricity as well as the number of tendons and routes of each cable; and to calculate the resulting stress of the beam cross-section and the resulting loss of prestress forces. There were 4 tendons of prestressed cables for the PCI Girder design, each of which consisted of 19 high quality wires, i.e. uncoated 7 Wire Super Strands ASTM A-416 grade 270 with the cross-section equal to 12.7 mm in width and the ultimate tensile stress by1,860 Mpa, with a total of 76 strands. The tendon tensioning system implemented was the post-tensioning one where the prestress force was given when the concrete has already achieved the required age. The Bridge of Meureudu City experienced a total prestressed loss by 26.32%. The tendon route was parabolic with the greatest moments by 7,556.75 kNm derived from a combination of its own weight, additional dead loads, lane loads, the brake force and wind loads.
CRACKING BEHAVIOR AND CRACK WIDTH PREDICTIONS OF CONCRETE BEAMS PRESTRESSED WITH BONDED FRP TENDONS
A total of six specimens were tested under four-point loading to examine the cracking behavior of prestressed concrete beams with a combination of bonded CFRP tendons and steel/GFRP reinforcements. The investigated parameters included the partial prestressing ratio (PPR), amount of prestressed CFRP tendons, types of nonprestressed reinforcements, and jacking stress levels. The characteristics of cracking propagation, cracking spacing and crack widths of specimens were presented. Test results indicated that the prestressed concrete beam reinforced with nonprestressed GFRP rebars exhibited wider crack width and larger crack spacing than those reinforced with nonprestressed steel rebars. Based on the correlative principles recommended by ACI 224R-01, a formula modified from the Frosh equation was provided for calculating the maximum crack width of concrete beams with a combination of bonded FRP tendons and steel/FRP reinforcements.