Experimental Study on Shear Behavior of Precast Concrete Segmental Beams with Hybrid Tendons and Dry Joints (original) (raw)
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Modified Model for Shear Carrying Capacity of Segmental Concrete Beams with External Tendons
Doboku Gakkai Ronbunshuu E, 2010
The study presents an investigation of the shear behavior of segmental concrete beams with external tendons considering the effect of joint opening. Joint position and prestressing force that affect the joint opening have been examined based on the results of experimental procedure and FEM. The simplified truss model with the small number of degree of freedom has been modified for segmental concrete beams with external tendons. The formulations to predict the variable angle and the thickness of struts are suggested with considering the effect of joint opening. A satisfactory prediction for the shear carrying capacity and the failure mechanism of segmental concrete beams with external tendons has been obtained.
Shear Carrying Capacity of Segmental Concrete Beams with Draped External Tendons
Journal of Japan Society of Civil Engineers, Ser. E2 (Materials and Concrete Structures), 2011
This study presents an investigation of the shear behavior of segmental concrete beams with draped external tendons. Deviator force and transfer mechanism of prestressing force from an anchorage that affect the shear failure mechanism have been examined based on the results of experimental procedure and FEM with different location of deviator and inclined angle of draped tendons. The modified model proposed by authors has been extended for segmental concrete beams with draped external tendons with considering the effect of deviator force and transfer mechanism of prestressing force from the anchorage. The results from the extended modified model for draped external tendons had a good agreement with experimental results.
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
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
Shear Carrying Capacity of Segmental Prestressed Concrete Beams
Doboku Gakkai Ronbunshuu E, 2009
This paper describes the results of an experimental study and nonlinear finite element method in order to examine the shear failure mechanism of segmental prestressed concrete beams by varying the length of segment, prestressing force and loading position. It is observed that after the opening of the segmental joints, the stiffness of such beams considerably decreases and the tendon stress is caused to increase significantly. The simplified truss model and other existing prediction methods for shear carrying capacity have been applied in this study in order to examine their applicability and accuracy. The simplified truss model can provide reasonable accuracy under the limitation of applied prestressing force.
Flexural Strength of Prestressed Concrete Beams with Tendon wrapped by Plastic sheets
For post-tension prestressed concrete beams, both of tendons laid in metal duct and wrapped by plastic sheets are recognized as unbonded tendon by researchers, and the same equation is used to estimate the flexural strength. But the contacting conditions between tendon and its surrounding concrete are quite different for these two kinds of unbonded tendons. This study compares the flexural strength, crack distribution and crack width of beams with these two kinds of unbonded tendons and bonded tendon. The results reveal that the structural behavior of tendon wrapped by plastic sheets is between bonded tendon and tendon laid in metal duct. A modified equation is proposed to estimate flexural strength of tendon wrapped by plastic sheets. Reducing cost and shortening construction time are the main advantages for this kind of the prestressed beams with tendon wrapped by plastic sheets. After further investigation, it may be an alternative method for the post-tension prestressed concrete structure in the future.
Engineering Structures, 2018
Precast segmental columns have been more and more popularly used in constructions of prefabricated reinforced concrete (RC) structures in recent years. During its servicing life the precast segmental column might be subjected to lateral impact loads from hazards such as falling rock and vehicle collision etc., which however has not been well understood. It is therefore necessary to properly understand the response and vulnerability of segmental column under impact loading. A previous experimental study revealed that the trapezoidal prism shear key on concrete segment could effectively reduce lateral slippage between segments under lateral impact loading, but stress concentration near the shear key led to crushing damage to concrete segment. A new shear key design, i.e., domed shear key with smoothed curvature is proposed in this study. Precast segmental columns with domed shear key are fabricated and tested. This paper presents the test results of scaled segmental columns with this new shear key design. The performance of segmental column with the new dome shear key is compared with previously tested columns with trapezoidal shear key and plain segmental column without shear key. Furthermore, the segmental columns with the new domed shear keys were impacted at different locations along the column including the column mid-span, the segmental joint, and the bottom segment to examine the influences of different impact locations on their impact resistant capacities, and the response and failure modes.
Effect of Torsion on Externally Prestressed Segmental Concrete Bridge with Shear Key
2009
Externally Prestressed Segmental (EPS) concrete box sections are widely used in the construction of bridge structures today. EPS concept has become an attractive tool for rehabilitation and strengthening of existing bridges which have insufficient strength and/or excessive deflection and cracking. Problem statement: EPS bridges are affected by combined stresses (bending, shear, normal, and torsional) at the joint interface between the segments. However, very limited researchers studied this type of bridges under combined stresses. Approach: This paper presented an experimental investigation of the structural behaviour of EPS bridge with shear key under torsion. Four beams were tested, each containing three segments that were presetressed using two external tendons. A parametric study of two different external tendon layouts as well as different levels of torsional force applied by different load eccentricities was conducted. Results: The effect of torsion was evaluated in terms of vertical deflections, concrete and tendon strains, failure loads and failure mechanisms. It was concluded that torsion has a significant effect in the structural behaviour of external prestressed segmental box girder beams. Torsion not only alters failure load of the beam but also changes the type of failure mechanism. It was also investigated that harp tendon layout results in better structural behaviour in term of deflection and tendon strain as compared with the straight tendon. Recommendations: It recommended including the effect of joint (flat and shear key) type as well as the effect of tendon layout under torsion to obtain comprehensive behavior of EPS bridge.
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.
MATEC Web of Conferences, 2016
This research designed a partial prestressed concrete beam-column with reinforced concrete interior joint, using square columns of 400/400 mm, reinforcement 6 D16 + 4D13, section beam 250/400 mm, tensile reinforcement 5 D13, compression reinforcement 3 D13 + 2 strand tendon D12,7 mm , and joint without plastic hinge, then tested in laboratory with lateral cyclic loads on peak column, static axial load 1120 kN on the centre column, to get the tendon capacity to assume positive and negative bending moments due to lateral load, according to provisions of ACI 318-2008 part 21.5.2.5 (c). Test results showed that the moment tendon contribution on beam section, in the tensile area, the positive and negative moment both on the left side or the right side column are all qualified (<25 %). In compression area, the positive moments on left and right columns are not qualified at all (> 25 %). As for the negative moment, either left or right side column are all qualified (< 25 %). Ductility, compression, and tensile ductility on drift ratio 3.50% are all qualified (>4.0). Although the contribution of positive moment capacity tendon in compression areas does not qualify, in overall, the reliability and ductility of the structure qualify.