Shear Carrying Capacity of Segmental Concrete Beams with Draped External Tendons (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.
KSCE Journal of Civil Engineering, 2019
A series of tests were carried out on nine specimens to improve the understanding of the shear behavior of precast concrete segmental beams (PCSBs) with hybrid tendons and dry joints. The influences of the tendon layout (hybrid tendons and external tendons), shear span ratio, and joint type (monolithic joints, and dry joints) on shear behavior of PCSBs were experimentally studied. The test results indicated that hybrid tendons slightly improved the shear strength and stiffness of PCSBs with dry joints compared to external tendons. The shear strengths of PCSBs with hybrid tendons and dry joints reduced with an increasing shear span ratio. Compared to monolithic beams with hybrid tendons, the dry joints slightly decreased the shear strength and enhanced the nonlinear behavior of PCSBs with hybrid tendons. The shear strengths of PCSBs and monolithic beams can be conservatively predicted by the AASHTO, Chinese code, and British Standard. The strut-and-tie model of prestressing force can accurately estimate the shear strengths of all the beams.
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.
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.
Nordic Concrete Research, 2021
Predicting the stress increase of an unbonded tendon in a post-tensioned continuous concrete beam at ultimate capacity is more difficult than when bonded tendons are used. The failure mechanisms of the continuous beam are also different to that of the simple-span beam. The loading type, ductility of the support area and moment redistribution influence the behaviour of the continuous structures. In this research, the simplified nonlinear analysis was used for predicting the unbonded tendon stress increase at ultimate capacity in continuous two-span beams. The model is based on the moment-curvature relationships of the reinforced concrete cross-sections under different compressive forces and deformations of the continuous beam under loading. The results have been compared with the experimental results of recent studies found in the literature. In addition, 92 unbonded post-tensioned two-span beams with different reinforcements have been examined by using the model and compared to the ...
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.
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.
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.
Ductility of Externally Prestressed Continuous Concrete Beams
Ductility is a desirable structural property that allows stress redistribution and provides warning of impending failure. Factors affect the ductility of beams prestressed with external FRP tendons are different than those affect the ductility of ordinary bonded prestressed concrete beams due to lack of bond and linear stress-strain relationship of FRP tendons. This paper investigated the effect of several variables on the ductility of continuous concrete beams, externally strengthened using Parafil ropes. The test variables included external prestressing force value, depth of external prestressing tendons, loading pattern, tendon profile and location of deviators. Test results show that the ductility of the externally prestressed concrete beams significantly reduced due to prestressing. Also, the eccentricity of the prestressing force and the tendon profile had the main influence on ductility of the externally prestressed beams, while the variation in prestressing force value, loading pattern and location of deviators had a less effect.
Re-Anchorage of a Ruptured Tendon in Bonded Post-Tensioned Concrete Beams: Model Validation
Key Engineering Materials, 2013
Many post-tensioned concrete bridges have been reported to have ruptured tendons due to corrosion [1] and the assessment of their residual structural capacity has to account for the possibility of re-anchorage of failed tendons. This paper presents an experimental programme to validate a numerical model developed by the authors for the re-anchorage of a ruptured tendon in post-tensioned concrete [2]. The experimental programme considered 33 post-tensioned concrete prisms, in which the rupture of tendon was simulated by releasing the tendon at one end. The full field displacement at concrete surface after release was measured using 3D Electronic Speckle Pattern Interferometry (ESPI). A wide range of parameters: tendon diameter, duct material, grout strength, concrete strength and shear reinforcement were investigated to validate the proposed model, which is found to be suitable for use in assessing post-tensioned concrete bridges with damaged tendons.