Journal articles: 'Shear strength of unbonded tendons'

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Dilger, Walter H., and Marwan Shatila. "Shear strength of prestressed concrete edge slab–column connections with and without shear stud reinforcement." Canadian Journal of Civil Engineering 16, no. 6 (December 1, 1989): 807–19. http://dx.doi.org/10.1139/l89-124.

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Results are reported of tests to failure on six full-scale unbonded post-tensioned prestressed concrete slab–edge column specimens. The objective is to study experimentally the strength and behaviour of this type of connections. The variables are quantity and distribution of stud shear reinforcement and length of overhang. The relevant design equations suggested by Dilger and Ghali as well as several models by others for predicting the strength of prestressed concrete slab–edge column connections are compared with test results. It is concluded that the ACI and CSA provisions for predicting the strength of such connections are conservative, and that the presence of stud shear reinforcement is a good means of increasing the strength and ductility of this type of connections. Key words: shear strength, flat slabs, prestressed concrete, unbonded tendons, shear reinforcement, design, ductility.

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Sayed-Ahmed, Ezzeldin Y., Shelley L. Lissel, Gamil Tadros, and Nigel G. Shrive. "Carbon fibre reinforced polymer (CFRP) post-tensioned masonry diaphragm walls: prestressing, behaviour, and design recommendations." Canadian Journal of Civil Engineering 26, no. 3 (June 1, 1999): 324–44. http://dx.doi.org/10.1139/l98-073.

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The use of post-tensioned masonry can lead to economic and elegant structures. A major problem associated with post-tensioning is the corrosion of the steel tendons, especially for unbonded tendons. If carbon fibre reinforced polymer (CFRP) tendons could be used to replace the traditional steel tendons, the corrosion problem would be overcome. However, a number of issues need to be resolved before CFRP tendons can be used comfortably in post-tensioning applications. The first part of this paper deals with a diaphragm wall post-tensioned using CFRP tendons. The post-tensioning procedures are described and the prestress losses occurring in the past 12 months are presented. Results from thermal, flexure, and racking shear tests performed on the wall are reported. The second part of the paper deals with the development of design procedures and equations based on both the test results and the database currently available. The equations presented are specifically for CFRP unbonded post-tensioned masonry diaphragm walls but with appropriate modification could be applied to the design of any CFRP post-tensioned masonry wall. A design example is included.Key words: anchorage system, carbon fibre reinforced polymers, diaphragm walls, flexural strength, masonry walls, prestress losses, prestressed masonry, post-tensioning, shear strength, thermal loads.

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Lissel, Shelley L., Nigel G. Shrive, and Adrian W. Page. "Shear in plain, bed joint reinforced, and post-tensioned masonry." Canadian Journal of Civil Engineering 27, no. 5 (October 1, 2000): 1021–30. http://dx.doi.org/10.1139/l00-057.

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Masonry is cost competitive on a life cycle basis with other forms of construction, and should therefore be considered as a structural material more frequently by both architects and engineers. Post-tensioned geometric sections of masonry are structurally efficient wall systems. Post-tensioning with carbon fibre reinforced polymer (CFRP) is an attractive solution to potential corrosion problems with unbonded tendons. Tests on CFRP post-tensioned diaphragm walls have revealed that shear strength in prestressed masonry is an area deserving more study and improvement. The tests also showed that the bonding pattern of the masonry at the web-flange junction can have a substantial effect on the resulting strength of that connection. A test series to evaluate the effects of prestress force and bed reinforcement on shear strength has been carried out and a summary of the results is presented here. Tests to determine the effect of bonding pattern on the strength of the web-flange connection have also been conducted.Key words: post-tensioning, masonry, shear, FRP tendons, corrosion-free.

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Lissel, S. L., N. G. Shrive, and J. Gilliland. "Design of carbon fibre reinforced polymer post-tensioned masonry diaphragm retaining walls." Canadian Journal of Civil Engineering 32, no. 3 (June 1, 2005): 579–94. http://dx.doi.org/10.1139/l05-008.

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Two masonry diaphragm retaining walls were constructed on the University of Calgary campus and post-tensioned with carbon fibre reinforced polymer (CFRP) tendons. As these are the first masonry diaphragm walls post-tensioned with CFRP tendons outside of a laboratory, one objective in the design was to provide a wide margin of safety, especially concerning the effective, or sustained, prestressing force and losses. The tendons are unbonded, so guidance chairs were placed during construction to meet the requirements of the clauses expected in the next edition of the Canadian masonry design code. Research has shown that the strength of masonry to resist shear in the webs is enhanced by the normal stress induced by post-tensioning, so this was used in the design. The webs of the walls interlock with the flanges, imposing restrictions on the spacing of the webs. A centre-to-centre spacing of 500 mm was selected, with one tendon per cavity. The design of the walls and capping beams is detailed, and the construction sequence and monitoring program are described briefly. Key words: post-tensioning, masonry, retaining walls, design, FRP tendons, corrosion free

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Wang, H. L., S. W. Liu, and Z. Zhang. "Seismic Performance and Effects of Different Joint Shapes for Unbonded Precast Segmental Bridge Columns." Journal of Mechanics 32, no. 4 (April 14, 2016): 427–33. http://dx.doi.org/10.1017/jmech.2016.22.

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AbstractTo study the seismic performance and the effects of different joint shapes for unbonded precast segmental bridge columns under low-reversed cyclic loading, two 3-D finite element (FE) models respectively using plane-contact joints and shear resistant joints were established. In the FE models, the mechanical behaviors of concrete and tendons were respectively described by the damage-plastic model and the bilinear model, and the contact criteria was based on Coulomb's Friction. The results of nonlinear time history analysis showed that the deformation of the columns was mainly composed of alternately open-closed joints, and the failure of the column was mainly caused by concrete crush on the bottom segment. Compared with two model's hysteresis loop, backbone curve, ductility and residual deformation, it was found that the column with shear resistant joints had longer stable period of strength, better ductility, and smaller residual displacement than the column with plane-contact joints, so it had better seismic performance.

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Zheng, Wen Zhong, Chong Xi Bai, and Hui Dong Cheng. "Experimental Study on Behaviors of Unbonded Prestressed Concrete Beams Reinforced with CFRP Tendons." Key Engineering Materials 400-402 (October 2008): 567–73. http://dx.doi.org/10.4028/www.scientific.net/kem.400-402.567.

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In order to research behaviors of unbonded prestressed concrete beams reinforced with CFRP tendons, static load experiments on 4 partially prestressed simple beams with unbonded CFRP tendons and 9 two spans partially prestressed concrete continuous beams with unbonded CFRP tendons were performed. Based on the experiment results of simple beams, the law of ultimate stress increment in unbonded CFRP tendons in simple beams was obtained. Based on the experiment results of continuous beams, the law of stress increment in unbonded CFRP tendons in continuous beams was obtained at serviceability state and at strength limit state of bending capacity. The calculation formula of length of equivalent plastic hinge for this kind of continuous beam was presented. The calculation formulas of moment modification coefficient with composite reinforcement index for intermediate support as variable and relative plastic rotation for intermediate support as variable were given respectively.

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Du, Xiu Li, Zuo Hu Wang, and Jing Bo Liu. "Flexural Capacity of Concrete Beams Prestressed with Carbon Fiber Reinforced Polymer (CFRP) Tendons." Advanced Materials Research 168-170 (December 2010): 1353–62. http://dx.doi.org/10.4028/www.scientific.net/amr.168-170.1353.

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Fiber reinforced polymer (FRP), particularly those incorporating carbon fiber (CFRP), has high strength, high stiffness-to-weight ratio and high resistance to corrosion, which shows potential for use as prestressing tendons in corrosive environment. However, concrete beams prestressed with FRP tendons have showed brittle flexural failure due to the elastic rupture of FRP tendons. In order to improve the ductility, a combination of bonded and/or unbonded prestressing tendons was used. Nine prestressed concrete beams were tested up to failure to study the effect of bonded and unbonded FRP tendons on their flexural capacity. Three factors were taken into consideration; the bonding condition of CFRP tendons, the location of CFRP tendons and the prestressing ratio. Also an analytical investigation was carried out to extend some flexural capacity calculation equations to this beam type. The results of the experimental showed that under the same condition, the carrying capacity of concrete beam prestressed with bonded FRP tendons was 20% higher than that of internal unbonded prestressed beam, and was 40% higher than that of external unbonded prestressed beam without deviators. By combination of bonded and unbonded FRP tendons, the ductility of prestressed concrete beams can be improved.

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Lee, Deuck Hang, and Kang Su Kim. "Flexural strength of prestressed concrete members with unbonded tendons." Structural Engineering and Mechanics 38, no. 5 (June 10, 2011): 675–96. http://dx.doi.org/10.12989/sem.2011.38.5.675.

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HAMAHARA, Masayuki, Shoudai KOIKE, and Tsuyoshi FUKUI. "ULTIMATE STRENGTH OF PRECAST CONCRETE MEMBERS ASSEMBLED BY UNBONDED TENDONS." Journal of Structural and Construction Engineering (Transactions of AIJ) 86, no. 789 (November 1, 2021): 1549–57. http://dx.doi.org/10.3130/aijs.86.1549.

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Wei, Ya, Francis T. K. Au, Jing Li, and Neil C. M. Tsang. "Experimental and numerical investigation of post-tensioned concrete flat slabs in fire." Journal of Structural Fire Engineering 7, no. 1 (March 14, 2016): 2–18. http://dx.doi.org/10.1108/jsfe-03-2016-001.

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Purpose This paper aims to understand the structural fire performance of two-way post-tensioned flat slabs, particularly their deformations and load-carrying mechanisms in fire, and to explore the behaviour of post-tensioned high-strength self-compacting concrete flat slabs with unbonded tendons in fire. Design/methodology/approach Four tests of post-tensioned high-strength self-compacting concrete flat slabs were conducted under fire conditions. Numerical modelling using the commercial package ABAQUS was conducted to help interpret the test results. Findings Two of the specimens with lower moisture contents demonstrated excellent fire resistance performance, while the others with slightly higher moisture contents experienced severe concrete spalling. Originality/value The test results were discussed in respect of thermal profiles, deflections, crack patterns and concrete spalling. The performance of post-tensioned high-strength self-compacting concrete flat slabs with unbonded tendons under fire conditions was better understood.

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Luchi, L. A. R., and J. C. C. Leite Jr. "Design of punching shear for prestressed slabs with unbonded tendons on internal columns." Revista IBRACON de Estruturas e Materiais 10, no. 4 (August 2017): 788–825. http://dx.doi.org/10.1590/s1983-41952017000400002.

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ABSTRACT This paper is related to the punching shear in prestressed slabs with unbonded tendons for interior columns calculated by the codes ABNT NBR 6118:2007, ABNT NBR 6118:2014, EN 1992-1-1:2004 e ACI 318-11. To calculate the punching shear resistance the formulations of the NBR 6118:07, effective until April/2014, did not consider the compression of the concrete in the plane of the slab, due to prestressing. Just the inclined components of some tendons were considered for total load applied relief, but this fact did not generate a significant difference, compared to reinforced concrete, because the inclination angle is very close to zero. The American and European provisions consider a portion related to the compression of the concrete in the planeof the slab. Differences in the results obtained by the four design codes will be exposed, showing that the EC2:04 and the NBR6118:14 achieved the best results.

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Gardner, N. J. "Punching shear provisions for reinforced and presfressed concrete flat slabs." Canadian Journal of Civil Engineering 23, no. 2 (April 1, 1996): 502–10. http://dx.doi.org/10.1139/l96-054.

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The validity of the CSA A23.3-94 code provisions for punching shear were compared with the punching shear results of 142 reinforced concrete flat slabs, 16 prestressed concrete flat slabs with unbonded tendons, and 17 flat slabs with unbonded prestressed and supplementary bonded reinforcement. The code prediction equations are not capable of direct verification against experimental results without using a correction factor. Using a justifiable correction factor, the CSA A23.3-94 provisions are appropriately conservative for reinforced concrete slabs but the scatter is large. However, it was concluded that the CSA A23.3-94 provisions are not conservative for prestressed concrete flat slabs. An equation is proposed to calculate the punching shear capacity of reinforced concrete and prestressed concrete slabs, which has a smaller coefficient of variation than the punching shear provisions of CSA A23.3-94, for symmetrically loaded interior columns. The critical section of the proposed method is the perimeter of the column, which is easier to justify than an arbitrary critical perimeter half the effective depth of slab from the column. Key words: reinforced concrete, prestressed concrete, flab slabs, punching shear.

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Liu, Jia Sheng. "Design Analysis of Unbonded Prestressed Concrete Two-Way Slab." Applied Mechanics and Materials 204-208 (October 2012): 853–56. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.853.

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Through some engineering example, the finite element software SAP2000N is used to make a finite element analysis on the prestressed concrete slab, which is made of concrete with grade of C40, low relaxation PC strand wile with tensile strength standard value of 1860N/mm2and nonprestressed reinforcements with grade of HRB335. By doing this, the author systematically introduced the material selection, prestressing technique and linear, load values and internal force calculation, distribution of prestressed tendons and nonprestressed reinforcement, the design process of crack and deformation of cast-in-site prestressed concrete two-way slab.

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Liu, Qing Wen, and Fu Qiang Wu. "Characteristic Analysis of Prestressed Concrete Frame Joints with Spread-Ended Beams." Applied Mechanics and Materials 578-579 (July 2014): 648–52. http://dx.doi.org/10.4028/www.scientific.net/amm.578-579.648.

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Three joints of prestressed concrete frame are studied under low frequency reversed loading. The failure and cracks feature, damage characteristics and mechanical properties under seismic loads are comparatively analysed between joints with spread-ended beams and conventional joints. Studies show that the layout of prestressing tendons and joints with spread-ended beams have little influence on the bearing capacity and ductility. Prestressing tendons through the joint core region can improve the shear strength of joints, but tendons through the joint outer region can not. We need to only consider the influence on the area of prestressing tendons through joint core region when calculating the shear strength of joints.

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Jin, Li Bing, De Cai Chen, and Ji Peng Qi. "Experimental Study on Shear Capacity of Prestressed SFRC Beams." Applied Mechanics and Materials 256-259 (December 2012): 926–29. http://dx.doi.org/10.4028/www.scientific.net/amm.256-259.926.

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In order to study the shear capacity enhancement effect of prestressed technology to steel fiber reinforced concrete, the practical formulas were proposed for evaluating the shear-strength of unbonded prestressed steel-fiber reinforced concrete beams (UPSFRCB) through the test and study of shear capacity of UPSFRCB with simply supported ends. Various factors affecting the shear strength of UPSFRCB, such as steel fiber, prestress and shear-span to depth ratio were analyzed. The result is of importance to the popularization and application of prestressed steel-fiber reinforced concrete.

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Estévez-Cimadevila, J., F. Suárez-Riestra, D. Otero-Chans, and E. Martín-Gutiérrez. "Experimental Analysis of Pretensioned CLT-Glulam T-Section Beams." Advances in Materials Science and Engineering 2018 (2018): 1–12. http://dx.doi.org/10.1155/2018/1528792.

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The bending behavior of T-section beams composed of a glulam web and an upper cross-laminated timber flange was studied. The influence of two fundamental factors on the bending strength and stiffness was considered: the wood species used for the webs and pretensioning with unbonded tendons. Sixteen specimens with a 9 m span were tested until failure: eight of them were nontensioned (4 Picea abies webs and 4 Quercus robur webs) and the other eight were pretensioned using threaded bars with 20 mm diameter anchored in plates fixed at the ends of the specimens (4 Picea abies webs and 4 Quercus robur webs). Pretensioning with unbonded tendons showed a clear improvement in the load capacity of the specimens with Picea abies webs, while the difference was not significant for the specimens with Quercus robur webs. Considering deflection, pretensioning gave the advantage of an initial precamber but also generated slight variations in the stiffness as a result of increasing the portion of the section that was in compression. The variation in the stiffness depended on the relation between the compressive and tensile moduli of elasticity parallel to the grain, and its influence on the deflection was analyzed using a finite element method.

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Shi, Yun, Guanglin Yuan, and Hao Zhu. "Effect of Axial Compression Ratio on Seismic and Self-Centering Performance of Unbonded Prestressed Concrete Columns." Advances in Civil Engineering 2022 (January 18, 2022): 1–13. http://dx.doi.org/10.1155/2022/7346620.

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To explore the influence of the applied axial compression ratio and preloaded axial compression ratio on the seismic performance of unbonded prestressed concrete columns, pseudo-static tests were carried out on four prestressed columns and one ordinary column in this study. The seismic performance indexes of test columns were studied and analyzed, including failure modes, hysteresis curves, skeleton curves, stiffness, ductility, and energy dissipation. The test results show that compared with concrete columns with ordinary reinforcement, the hysteresis curve of reinforced concrete columns with prestressed tendons has a pinch phenomenon to a certain extent, and the energy dissipation performance becomes worse. For the prestressed columns, the greater the applied axial compression ratio, the worse the fullness of hysteresis curves and the energy dissipation performance, the greater the residual displacement, the faster the strength attenuation, and the worse the self-centering performance. For the posttensioned unbonded prestressed concrete columns, the greater the preloaded axial compression ratio, the worse the energy dissipation performance of the test column, the slower the strength attenuation, and the better the self-centering performance.

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Kwon, Byung Un, and Thomas H. K. Kang. "Seismic Behavior of RC Beam-Column Exterior Joints with Unbonded Tendons and High Strength Concrete." Journal of the Earthquake Engineering Society of Korea 19, no. 6 (November 1, 2015): 283–92. http://dx.doi.org/10.5000/eesk.2015.19.6.283.

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Alotaibi, Emran, Nadia Nassif, Mohamad Alhalabi, Humam Al Sebai, and Samer Barakat. "Numerical investigation on redundancy of bridges with AASHTO I-girders." Bridge Structures 17, no. 1-2 (June 11, 2021): 41–50. http://dx.doi.org/10.3233/brs-210187.

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Bridge safety is one of the most critical concerns among civil engineering fields due to its high importance. The redundancy of bridges was heavily investigated in the literature; however, they were focused on twin girder redundancy cases. Additionally, literatures were scarce in studies that focused on the improvement that should be made to achieve redundancy systems in different AASHTO I-girder types. Thus, this study focused on assessing the additional required number of tendons for different AASHTO I-girder types and spacing between them to achieve the redundancy of I-girder bridges. The additional unbonded tendons are suggested to be added externally or internally. The parameters varied in this study are compressive strength of ultrahigh-performance concrete (UHPC), spacing between girders (i.e. number of girders) and type of girders. Leap Bridge Concrete software was used to simulate the required structural modes. After performing extensive numerical analyses following AASHTO LRFD guidelines, the results have shown that in case of the removal of external I-girder, the tendons in the nearest girder need to be nearly increased by 1.85 to 2.3 times compared to the original design, depending on spacing, compressive strength, and the number of girders. On the other hand, in the case of interior girder removal, the number of tendons in the nearest two girders need to be increased by 1.24 to 1.32 times the original design. The effect of compressive strength variation of the used UHPC was negligible compared to spacing and type of girder. It is worth mentioning that all simulations in this study were verified using CSI Bridge software.

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Nishiyama, Taizo, Hosin (David) Lee, and M. Asghar Bhatti. "Investigation of Bonding Condition in Concrete Overlay by Laboratory Testing, Finite Element Modeling, and Field Evaluation." Transportation Research Record: Journal of the Transportation Research Board 1933, no. 1 (January 2005): 15–23. http://dx.doi.org/10.1177/0361198105193300103.

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To evaluate the effect of bonded versus unbonded condition in concrete overlay structure, a field evaluation, laboratory experiment, and 3-D finite element analysis (FEA) model were carried out. First, a field evaluation of bonded and unbonded pavement test sections in Iowa was performed. Cores were extracted from existing pavements and tested for their bond strengths with shear testing equipment. The bond strength between an overlay and the existing pavement gradually increased over time, regardless of the initial bond strength. In some cases, an insufficient bond shear strength at the interface between the concrete overlay and the existing pavement seemed to have contributed to increased distress on the overlay surface. Second, a laboratory experiment was conducted to investigate an effect of bonding in pavement structure. Concrete cylinder specimens that were one-half regular concrete and one-half polymer concrete were fabricated, and their indirect tensile strength was measured at the bonding interface. The experiment results indicated that polymer concrete samples exhibited higher indirect tensile strength than regular concrete samples at the interface. Finally, a 3-D FEA model using eight-node solid elements and a spring element was developed to quantify the bonding level. This model can simulate various bond levels from fully bonded to unbonded by a change of the stiffness of the spring element. The most appropriate spring stiffness was identified for different bonding conditions of overlaid pavements. A parametric study was conducted with spring stiffness changed to develop a matrix that can be used to quantify different levels of bonding. This matrix can help pavement engineers select the most appropriate spring stiffness for a given bonding condition and overlay thickness.

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Abbas, Hayder Qays, and Alaa Hussein Al‐Zuhairi. "Usage of EB-CFRP for Improved Flexural Capacity of Unbonded Post-Tensioned Concrete Members Exposed to Partially Damaged Strands." Civil Engineering Journal 8, no. 6 (June 1, 2022): 1288–303. http://dx.doi.org/10.28991/cej-2022-08-06-014.

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The study presents the performance of flexural strengthening of concrete members exposed to partially unbonded prestressing with a particular emphasis on the amount (0, 14.2, and 28.5%) of cut strands-symmetrical and asymmetrical damage. In addition to examining the influence of cut strands on the remaining capacity of post-tensioned unbonded members and the effectiveness of carbon fiber reinforced polymer laminates restoration, The investigated results on rectangular members subjected to a four-point static bending load based on the composition of the laminate affected the stress of the CFRP, the failure mode, and flexural strength and deflection are covered in this study. The experimental results revealed that the usage of CFRP laminates has a considerable impact on strand strain. In addition to that, the flexural stiffness of strengthened members becomes increasingly significant within the serviceability phases as the damaged strand ratios increase. The EB-CFRP laminates increased the flexural capacity by approximately 13%, which corresponds to strand damage of 14.28% and about 9.5% for 28.57% of strand damage, which represents one of the unique findings in this field. Additionally, semi-empirical equations for forecasting the actual strain of unbonded tendons were presented. The suggested equations are simple to solve and produce precise results. Doi: 10.28991/CEJ-2022-08-06-014 Full Text: PDF

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Yan, Wutong, Liangjiang Chen, Bing Han, Huibing Xie, and Yue Sun. "Flexural Analysis Model of Externally Prestressed Steel-Concrete Composite Beam with Nonlinear Interfacial Connection." Applied Sciences 12, no. 9 (May 7, 2022): 4699. http://dx.doi.org/10.3390/app12094699.

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Interfacial slip effects and the unbonded phenomenon of external tendons are the key mechanical features of the externally prestressed steel-concrete composite beams (EPCBs). In this paper, an 8-node fiber beam element is built for the nonlinear analysis of the composite beam with interfacial slip effects. A multi-node slipping cable element is proposed for the simulation of external tendons. The derived formulations are programmed in OpenSees as newly developed element classes to be conveniently used for the flexural analysis of EPCBs. The effectiveness of the proposed model is fully verified against the experimental tests of simply supported and continuous beams and then applied to the parametric study. The results show that the increasing deviator spacing will significantly decrease the tendon effective depth at ultimate states and further decrease the flexural capacity. The larger effective depth is beneficial to the tendon stress increments and further improves the flexural capacity. The enhancement of interfacial shear connection degree will increase the structural capacity but the effects on the tendon stress increments and second-order effects were not monotonic.

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Wang, Guo Lin, and Shao Ping Meng. "Experimental Study on Shear Behavior of Prestressed Concrete Deep Beams with Draped Tendons." Advanced Materials Research 163-167 (December 2010): 1339–42. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.1339.

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Two simply supported deep beams were tested, one with draped prestresssing tendons and the other without for reference. Shear behavior and the prestressing effect were focused on. The test results showed that deep beams with the longitudinal reinforcement ratio of a normal amount were inclined to fail in flexural-shear, and the prestressing could greatly increase both the cracking load and the shear strength. Beside, the Modified Strut-and-Tie Model (MSTM) and the sectional design method from China Code (GB02) have also been adopted for predictions. The comparisons indicates that the MSTM can not only well predict the shear strengths of deep beams, but also well account for the prestressing effect, while the sectional design method seems so conservative due to its not properly considering the shear mechanism of deep beams. It can be concluded that the MSTM is capable of predicting the shear strength of PC deep beams with draped tendons and thus can be employed in practical designs.

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Chang, Hong, and Wei Zhou. "Flexural Behaviour of Unbonded Posttensioned Concrete Beam Strengthened with Aluminium Alloy Plates." Mathematical Problems in Engineering 2020 (April 6, 2020): 1–13. http://dx.doi.org/10.1155/2020/6535609.

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Owing to their high corrosion resistance, aluminium alloy (AA) plates bonded with magnesium phosphate cement (MPC) are considered as a viable candidate for reinforcing inshore infrastructures that are subject to severe environmental conditions and vapor atmospheres. Therefore, the aim of this study is the evaluation of the flexural behaviour of simple beams that are strengthened using this technique. Six unbonded posttensioned concrete (UPC) beams with different reinforcement ratios are damaged by static loads and then repaired and strengthened using AA plates. The failures under two-point loading are then investigated. Thereafter, a simplified method is proposed for the evaluation of the flexural strength of a UPC beam strengthened by an AA plate with MPC. The flexural strengths of the six specimens increase by an average of 14%, and the displacement ductility factor decreases by an average of 34.14%. Moreover, the increase and decrease ratios are proportional and inversely proportional to the comprehensive reinforcement index, respectively. The influences of the three main factors on the flexural strength of the AA plate are determined: the increase in the stress of the unbonded tendons, stress at the midspan and slippage at the ends of the AA plate, and increase ratio of the flexural strength. It shows that the AA plates bonded with MPC can be used successfully in concrete strengthening.

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Pang, Miao, Zhangxiang Li, and Tiejiong Lou. "Numerical Study of Using FRP and Steel Rebars in Simply Supported Prestressed Concrete Beams with External FRP Tendons." Polymers 12, no. 12 (November 24, 2020): 2773. http://dx.doi.org/10.3390/polym12122773.

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This study aimed at examining the feasibility of using fiber-reinforced polymer (FRP) rebars instead of steel ones in prestressed concrete beams (PCBs) with external FRP tendons. By applying an experimentally validated program, numerical tests were performed on simply supported PCBs, with investigated variables including rebars’ type and area. Three types of rebars were considered, i.e., carbon, glass FRPs (CFRP, GFRP), and reinforcing steel. The ratio of tensile rebars ranged from 0.22% to 2.16%. The results indicated that the beams with CFRP rebars exhibited better crack mode and higher ultimate load than the beams with GFRP or steel rebars. GFRP rebars led to considerably higher ultimate deflection and tendon stress increment than steel rebars. In addition, several models for calculating the ultimate stress in unbonded tendons were assessed. An analytical model was also proposed to predict the tendon stress at ultimate and flexural strength in externally PCBs with steel and FRP rebars. The model predictions agreed well with the numerical results.

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Hu, Zebin, Zhenming Xu, Shufeng Zhang, Haibo Jiang, Yuanhang Chen, and Jie Xiao. "Experimental Study on Shear Behavior of Precast High-Strength Concrete Segmental Beams with External Tendons and Dry Joints." Buildings 12, no. 2 (January 27, 2022): 134. http://dx.doi.org/10.3390/buildings12020134.

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Precast high-strength concrete segmental beams with external tendons and dry joints (ED-PHCSBs) have become a potential alternative for achieving accelerated bridge construction due to their lighter self-weight and easier installation. In order to investigate the shear behavior of ED-PHCSBs, eight precast concrete segmental specimens were fabricated and tested to failure. For comparison purposes, one externally prestressed high-strength concrete monolithic beam was also investigated. The primary parameters, including concrete strength, shear span-depth ratio, stirrup ratio, joint number, and joint location, were adopted. Test results indicated that increasing the concrete strength or stirrup ratio can effectively improve the shear capacity of the ED-PHCSBs. The shear span-depth ratio was inversely proportional to shear strength for all specimens. The results also revealed that the joint number had a marginal effect on the defections and stresses of the external tendons of ED-PHCSBs. AASHTO 2017 and Chinese code 2018 can conservatively estimate the shear strength of ED-PHCSBs. Considering the actual failure modes of the precast beams, a calculation method based on a modified strut-and-tie model was proposed. The average and standard deviation of the ratios of the test results to the predicted value of the proposed method were 0.98 and 0.08, respectively. It indicated that the proposed formula was more accurate.

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Zhang, Burong, and Brahim Benmokrane. "Design and evaluation of a new bond-type anchorage system for fiber reinforced polymer tendons." Canadian Journal of Civil Engineering 31, no. 1 (January 1, 2004): 14–26. http://dx.doi.org/10.1139/l03-062.

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Corrosion resistance, high strength, and advantageous strength-to-weight ratio enable fiber reinforced polymers (FRPs) to have substantial potential to replace steel tendons in prestressed applications. One of the main technical obstacles to wide use of FRPs in the construction industry is the methodology to anchor FRP tendons to achieve their full strength. High tensile to compression and shear strength ratios make it necessary to develop a new anchorage design concept for FRP tendons. This paper gives a literature review of bond-type anchorage systems and the mechanics of stress transfer by bond from FRP tendons to grout and reports an experimental study on a newly developed bond-type anchorage system with carbon fiber reinforced polymer (CFRP) Leadline 8-mm-diameter rods. The test program consisted of nine monotonic tensile tests, two pullout tests, and two proving tests on the anchorage system with Leadline single- or 9-rod tendons. The test results showed that the developed anchorage system with 250-mm bond length ensures full development of the tensile strength of Leadline mono-rod tendons. The bond strength of Leadline 9-rod tendons is 14 MPa for a bond length of 95 mm, 62% of that of mono-rod ones with a bond length of 80 mm. The anchorage system with a 400-mm bond length gives at least 90% of the tensile strength of Leadline 9-rod tendons and also demonstrates an acceptable sustained loading behaviour in accordance with existing codes.Key words: anchorage, bond stress, creep, grout, polymers, rod, slip, tendon.

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Zhang, Xihong, Hong Hao, and Chao Li. "Multi-hazard resistance capacity of precast segmental columns under impact and cyclic loading." International Journal of Protective Structures 9, no. 1 (March 2018): 24–43. http://dx.doi.org/10.1177/2041419617736321.

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Using precast segmental concrete columns in structures improves the construction efficiency and site safety, leads to better construction quality, and reduces the construction cost, site disruption and environmental impact. The performance of segmental columns to resist earthquake and impact loads is not well studied yet. As a structure might be subjected to such loads during its service life, understanding its resistance capacities is essential for structural safety. This article reports the findings of our recent studies on the response of precast segmental columns with unbonded prestress tendons. Pendulum impact test and uniaxial cyclic test were conducted on quarter-scale segmental columns. The seismic performance and impact-resistant capacity were evaluated experimentally and compared with a reference conventional monolithic column. Test results showed that under cyclic loading, segmental columns exhibited better deformation ability and smaller residual drift; under impact loading, segmental columns also showed better self-centring capacity and less residual displacement. By introducing concrete shear key, the shear resistance at segmental joint could be improved; however, shear key would also result in more concrete segment damage owing to stress concentration.

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Vo-Le, Dien, Duong T. Tran, Thong M. Pham, Chinh Ho-Huu, and Long Nguyen-Minh. "Re-evaluation of shear contribution of CFRP and GFRP sheets in concrete beams post-tensioned with unbonded tendons." Engineering Structures 259 (May 2022): 114173. http://dx.doi.org/10.1016/j.engstruct.2022.114173.

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Zhou, Zhi Liu, Feng Wang, Kang Zhao, Tao Liu, and Ya Nan Zhang. "Calculation Method of Ultimate Punching Bearing Capacity of Unbonded Prestressed Concrete Slab." Applied Mechanics and Materials 744-746 (March 2015): 378–82. http://dx.doi.org/10.4028/www.scientific.net/amm.744-746.378.

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The calculation method of punching shear bearing capacity of unbounded prestressed concrete slab is presented for the reason that traditional methods mainly depend on experiences. The concrete material is assumed as ideal rigid-plastic material. The Quasi-Coulomb Criterion is taken as the strength criterion of concrete, according to plastic limit theory, and the calculation equation of punching shear limit bearing capacity of unbounded prestressed concrete slab is derived through the establishment of virtual work equation. Comparison of the calculation results based on the presented equation with test results proves that the calculation method in this paper can not only reflect and decide various influencing factors of punching shear ultimate bearing capacity of unbonded prestressed slab, and but also the calculated results are more reasonable, accurate.

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Rafeeqi, S. F. A., S. U. Khan, N. S. Zafar, and T. Ayub. "Implication of Unbondedness in Reinforced Concrete Beams." Advanced Materials Research 587 (November 2012): 36–41. http://dx.doi.org/10.4028/www.scientific.net/amr.587.36.

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In this paper, behaviour of nine (09) RC beams (including two control beams) after unbonding and exposing flexural reinforcement has been studied which were intentionally designed and detailed to observe flexural and shear failure. Beams have been divided into three groups based on failure mode and unbounded and exposed reinforcement. Beams have been tested under two-point loading up to failure. Experimental results are compared in terms of beam behaviour with respect to flexural capacity and failure mode which revealed that the exposed reinforcement does not altered flexural capacity significantly and unbondedness positively influences shear strength; however, serviceability performance of beams with unbonded and exposed reinforcement is less.

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Abdelatif, Amged O., John S. Owen, and Mohammed F. M. Hussein. "Re-Anchorage of a Ruptured Tendon in Bonded Post-Tensioned Concrete Beams: Model Validation." Key Engineering Materials 569-570 (July 2013): 302–9. http://dx.doi.org/10.4028/www.scientific.net/kem.569-570.302.

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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.

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Mortazavi, Ali. "Anchorage and shear strength properties for composite tendons used in earthwork support systems." Construction and Building Materials 21, no. 1 (January 2007): 109–17. http://dx.doi.org/10.1016/j.conbuildmat.2005.06.034.

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Jia, Li, Zhi Fang, Zhengmeng Huang, Kypros Pilakoutas, Qiwu Wang, and Xingyu Tan. "Flexural Behavior of UHPC Beams Prestressed with External CFRP Tendons." Applied Sciences 11, no. 19 (October 2, 2021): 9189. http://dx.doi.org/10.3390/app11199189.

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This paper presents an experimental investigation on the flexural behavior of ultra-high-performance concrete (UHPC) beams prestressed with external carbon fiber-reinforced polymer (CFRP) tendons. A total of eight T-shaped beam specimens were fabricated and tested, and the effects of the effective prestressing stress, partial prestressing ratio, deviated angle, and loading condition on the flexural behavior were analyzed. The experimental results indicate that the fully prestressed beams experienced a brittle failure, and the shear capacity of these beams was mainly controlled by the effective prestressing stress in CFRP tendons and the ultimate tensile strength of UHPC, whereas the partially prestressed beams failed in a ductile manner. The presence of internal steel reinforcement could significantly improve the flexural capacity and deformation ability. Thus, internal reinforcements should not be omitted from UHPC beams with CFRP tendons. A higher effective prestressing stress resulted in enhanced cracking load and flexural capacity. The deviated angle enhanced the utilization efficiency of high strength CFRP tendons. The loading condition exerted a slight influence on the flexural behavior of the specimens. Moreover, a method considering the effect of steel fibers was proposed and verified to predict the flexural capacity of UHPC beams prestressed with external CFRP tendons.

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Jung, Woo Tai, Moon Seoung Keum, Jae Yoon Kang, and Jong Sup Park. "An Experimental Study on Anchor Performance of Bare CFRP Tendons with Bond Type Anchor." Advanced Materials Research 1082 (December 2014): 408–11. http://dx.doi.org/10.4028/www.scientific.net/amr.1082.408.

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Despite of their outstanding axial strength, CFRP tendons necessitate special anchorage due to their low lateral shear strength. In order to cope with such CFRP tendon, the conventional bond type anchor needs to be improved. The results of bond tests executed on 10-mm diameter CFRP tendons coated with sand and oxide revealed that, even if the average bond strength increases by 3 times compared to the non-coated bare tendon, the coated CFRP tendon still requires excessively long anchored length for bonding. Therefore, this study applies a method enabling to shorten the bonded length and improving further the bond performance compared to sand or oxide coating. The improvement of the bond characteristics is achieved by splitting the ends of the CFRP tendon so as to widen the bonded area by 3.5 times. The test results showed that the anchor performance of the CFRP tendon reaches 95% of its tensile strength making it applicable for the bond type anchor.

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SAWABE, Sumihiro, Naoshi UEDA, Hikaru NAKAMURA, and Minoru KUNIEDA. "SHEAR FAILURE BEHAVIOR ANALYSIS OF RC BEAM WITH UNBONDED REGION AND DECREASED BOND STRENGTH IN STIRRUPS." Doboku Gakkai Ronbunshuu E 62, no. 2 (2006): 444–61. http://dx.doi.org/10.2208/jsceje.62.444.

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Satwika, Vanteddu, and Mohit Jaiswal. "Comparison of RCC and Post-Tensioned Flat Slabs Using ETABS." IOP Conference Series: Earth and Environmental Science 982, no. 1 (March 1, 2022): 012084. http://dx.doi.org/10.1088/1755-1315/982/1/012084.

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Abstract Flat slabs are widely used nowadays. The system’s insufficient punching shear capacity is a major and serious flaw. There are numerous approaches to increasing the punching shear strength of concrete slabs to solve the problem of punching failure. Increasing the thickness of the slab adjacent to the column, as well as the thickness of the column, contradicts the architectural intent. In developing countries such as India, the benefits of prestressing, particularly post-tensioning, have yet to be recognized. In this study, the technique of post-tensioning is used to strengthen a flat slab. RCC flat slabs are compared to post-tensioned flab slabs with different tendon profiles. Tendons are available in two forms: distributed and banded. The models were built as per ACI 318-14. These slab models were created using ETABS software, and the following parameters were compared: thickness, supporting reactions, punching shear, and deflection. When compared to traditional flat slabs. The results indicate that post-tensioned flat slabs have a higher punching shear capacity even at shallower depths, resulting in more cost-effective sections. The provision of tendons also results in lower deflection.

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Dolatabad, Yousef Askari, and Ali-Akbar Maghsoudi. "Ultimate stress increase in unbonded tendons in post-tensioned indeterminate I-beams cast with high strength normal and self compacting concrete." Engineering Science and Technology, an International Journal 21, no. 3 (June 2018): 495–506. http://dx.doi.org/10.1016/j.jestch.2018.04.006.

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Wang, Guo Lin, and Wen Sheng Ding. "Experimental Study on Shear Behavior of Prestressed Concrete Beams." Applied Mechanics and Materials 226-228 (November 2012): 1045–48. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.1045.

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Two simply supported beams with a shear span to depth ratio of 2.2 were tested, one with straight prestresssing tendons and the other without for reference. The shear behavior and the prestressing effect are focused on. The test results showed that the prestressed concrete (PC) beam has a significant arch effect, and the prestressing could greatly increase both the cracking load and the shear strength. Besides, the Modified Strut-and-Tie Model (MSTM) and the sectional design method from China Code (GB10) and ACI318-08 have also been adopted for predictions. The comparisons indicates that the MSTM can not only well predict the shear strengths of PC beams with a small shear span to depth ratio, but also well account for the prestressing effect, while the sectional design method seems so conservative due to its not properly considering the shear mechanism of such beams. It can be concluded that the MSTM is capable of predicting the shear strength of PC beams with significant arch effect and thus can be employed in practical designs.

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Marshe, Sylvanus, and Mark F. Green. "Punching behaviour of composite bridge decks transversely prestressed with carbon fibre reinforced polymer tendons." Canadian Journal of Civil Engineering 26, no. 5 (October 1, 1999): 618–30. http://dx.doi.org/10.1139/l99-027.

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Composite bridge decks under concentrated wheel loading develop compressive membrane action that tends to increase significantly the strength of the deck slab. Transverse prestressing of the deck slab can improve the compressive membrane action and allow a reduction in the slab thickness. With a reduced thickness, however, durability is a concern with steel prestressing tendons. By using fibre reinforced polymer prestressing tendons, the durability of the bridge deck slab can be improved. This paper describes an experimental investigation to study the punching behaviour of composite bridge decks transversely prestressed with carbon fibre reinforced polymer (CFRP) tendons. Six panels of a 1/4.04-scale model of a simply supported composite bridge deck are tested under a static concentrated wheel loading. The results are compared to those from a previous similar study using steel prestressing tendons. It is shown that it is feasible to use CFRP tendons to transversely prestress composite bridge decks, and that the CFRP prestressed bridge deck shows better overall structural performance than the steel prestressed deck. The lack of plasticity of the CFRP tendons is not a concern in this application.Key words: composite bridge deck, concrete, compressive membrane action, punching shear, prestressing, advanced composite material (ACM), fibre reinforced polymer (FRP).

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Zhang, Yannian, Ning Li, Qingjie Wang, Zhijun Li, and Xiaoyan Qin. "Shear Behavior of T-Shaped Concrete Beams Reinforced with FRP." Buildings 12, no. 12 (November 24, 2022): 2062. http://dx.doi.org/10.3390/buildings12122062.

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The calculation formula for bearing capacity was verified and further corrected through the current study of the influences of different parameters on the shear behavior of concrete T-beams reinforced with surface-embedded FRP. Tests were conducted on 14 beams reinforced with FRP tendons, including assessments of different concrete strength grades, longitudinal reinforcement ratios, surface characteristics, types, diameters, reinforcement modes, FRP spacings, and specimen shear span ratios. The results show that surface-embedded FRP reinforcement technology can be utilized to improve the overall stiffness and shear strength of beams, delay the development of oblique cracking, reduce the width of diagonal cracking, and improve the bite cooperation between concrete aggregates, thus improving the manifestation of reinforcement. The shear failure mechanism of reinforced concrete beams, strengthened with surface-embedded FRP, seemed to be similar to that of ordinary reinforced concrete beams. The mechanism of action was identical to that of stirrups, and the utilization factor of FRPs was determined.

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Zhu, Zhangfeng, and Zhengxing Guo. "Experiments on Hybrid Precast Concrete Shear Walls Emulating Monolithic Construction with Different Amounts of Posttensioned Strands and Different Debond Lengths of Grouted Reinforcements." Advances in Materials Science and Engineering 2016 (2016): 1–13. http://dx.doi.org/10.1155/2016/6802503.

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This paper proposed a hybrid precast concrete shear wall emulating monolithic construction (HPWEM) that utilized grouted vertical connecting reinforcements and unbonded posttensioned high-strength strands across the horizontal joint for the lateral resistance. The grouted reinforcements with predetermined debond length were used to provide strength by tension and energy dissipation by yielding. The posttensioned strands were mainly employed to offer the restoring force to reduce the residual displacement by elastic extension. The overlapping welded closed stirrups improved the confinement property of the restrained concrete, avoiding the brittle failure. Six HPWEM specimens, considering variables including the amounts of strands and the debond lengths of grouted reinforcements, as well as one referenced cast-in-place monolithic wall specimen, were tested under the low-cycle reversed lateral load. The HPWEM specimens were capable of providing strength, stiffness, ductility, and energy dissipation equivalent to that of the monolithic wall specimen under certain variable condition.

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Hassan, Ammar, Makoto Kawakami, Kyoji Niitani, and Tamio Yoshioka. "An experimental investigation of steel-free deck slabs." Canadian Journal of Civil Engineering 29, no. 6 (December 1, 2002): 831–41. http://dx.doi.org/10.1139/l02-092.

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The steel-free deck slab developed in Canada used straps as a confinement system and relied on the stiffness of this confinement system rather than its strength. In this paper, a new approach, using the strength of a confinement system comprising unbonded prestressed bars, was investigated. In addition, the effect of the concrete strength and the steel ratio of the confinement system was examined. Seven large-scale one-way steel-free deck slabs were built using normal- and high-strength concrete, prestressed to different levels, and statically tested up to failure. The overall behaviour of the slabs was similar to that of slabs confined by straps. Cracking strength was not considerably enhanced. The slabs failed in punching shear mode with high loads. The new approach was not able to overcome the problem of the longitudinal crack, which developed in the tested slabs and reportedly appeared in all the steel-free slabs built or tested previously in Canada. Prestressing had a definite effect, however, on delaying the occurrence of this longitudinal crack, thereby enhancing serviceability. The paper recommends that the serviceability limit state of the steel-free slabs would be better assessed by the occurrence of the longitudinal crack, even though the ultimate capacity of the slabs is high.Key words: arch action, cracking, external prestressing, high-strength concrete, punching shear, steel-free deck slab.

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Atutis, Edgaras, Marius Budvytis, and Mantas Atutis. "EXPERIMENTAL STUDY ON THE FLEXURAL AND SHEAR ANALYSIS OF CONCRETE BEAMS REIN FORCED WITH GLASS FIBER -REINFORCED (GFRP) BARS / STIKLO PLUOŠTO ARMATŪRA ARMUOTŲ SIJŲ, IŠANKSTINIO ĮTEMPIMO ĮTAKOS LAIKOMAJAI GALIAI IR STANDUMUI EKSPERIMENTINIS TYRIMAS." Mokslas - Lietuvos ateitis 5, no. 5 (December 19, 2013): 467–73. http://dx.doi.org/10.3846/mla.2013.73.

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The paper analyzes experimental studies examining the flexuraland shear analysis of the beams reinforced with GFRP bars. Atesting program consisted of two beams reinforced with longitudinalprestressed GFRP tendons, two beams reinforced withlongitudinal GFRP bars and two beams reinforced with longitudinalsteel reinforcement and shear reinforcement of GFRP bars.The experimental flexural and shear strength of concrete beamswere compared with theoretical strength calculated according toa number of design recommendations, and the significance ofprestressing for deflection and cracking was analyzed. Santrauka Straipsnyje nagrinėjami sijų, armuotų stiklo pluošto armatūra, eksperimentiniai tyrimai, kuriuose buvo nagrinėjama šių sijų laikomoji galia statmenajame ir įstrižajame pjūviuose. Buvo bandomos dvi sijos, armuotos išilgine iš anksto įtempta stiklo pluošto armatūra, dvi sijos armuotos neįtemptąja stiklo pluošto armatūra, dvi sijos armuotos plienine išilgine armatūra ir skersine stiklo pluošto armatūra. Gautos statmenojo ir įstrižojo pjūvio laikomosios galios palyginamos su įvairiomis projektavimo normomis ir rekomendacijomis, analizuojama išankstinio įtempimo reikšmė sijų lenkiamajam standumui.

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Han, Sun-Jin, Jae-Hoon Jeong, Hyo-Eun Joo, Seung-Ho Choi, Seokdong Choi, and Kang Su Kim. "Flexural and Shear Performance of Prestressed Composite Slabs with Inverted Multi-Ribs." Applied Sciences 9, no. 22 (November 17, 2019): 4946. http://dx.doi.org/10.3390/app9224946.

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Half precast concrete slabs with inverted multi-ribs (Joint Advanced Slab, JAS), which enhance composite performance between slabs by introducing shear keys at connections between the slabs and improve structural performance by placing prestressing tendons and truss-type shear reinforcements, have recently been developed and applied in many construction fields. In this study, flexural and shear tests were performed to verify the structural performance of JAS members. Towards this end, two flexural specimens and four shear specimens were fabricated, and the presence of cast-in-place concrete and the location of the critical section were set as the main test variables. In addition, the flexural and shear performance of the JAS was quantitatively evaluated using a non-linear flexural analysis model and current structural design codes. Evaluation results confirmed that the flexural behavior of the JAS was almost similar to the behavior simulated through the non-linear flexural analysis model, and the shear performance of the JAS can also be estimated appropriately by using the shear strength equations presented in the current design codes. For the JAS with cast-in-place concrete, however, the shear strength estimation results differed significantly depending on the way that the shear contributions of the precast concrete unit and cast-in-place concrete were calculated. Based on the analysis results, this study proposed a design method that can reasonably estimate the shear strength of the composite JAS.

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Wang, Xiao-Hui, and Xi-La Liu. "Analysis of RC beam with unbonded or exposed tensile steel reinforcements and defective stirrup anchorages for shear strength." Computers & concrete 10, no. 1 (July 25, 2012): 59–78. http://dx.doi.org/10.12989/cac.2012.10.1.059.

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Choi, Chang Sik, Baek Il Bae, Hyun Ki Choi, and Il Sung Park. "Shear Strength Upgrade of Perforated RC Shearwalls Using Prestress and Steel Plate." Advanced Materials Research 194-196 (February 2011): 1896–99. http://dx.doi.org/10.4028/www.scientific.net/amr.194-196.1896.

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Remodeling is also an environmentally-friendly approach that reduces the amount of waste in construction site. Specifically, there are many attempts to make house more wide according to the merging of two old houses in apartment buildings. For making two houses into single housing area, openings shoud be needed or walls should be removed. However, removing shearwalls are very dangerous attempt because of reducing of lateral load capacity of buildings. Therefore many engineers prefer to leave shearwalls. However, there are insufficient studies about partial damage, that is, openings. In these cases the damaged shear walls need to be retrofitted by additional materials or members. In this research, four specimens were tested to investigate the capacity of the damaged wall and the retrofitted wall. The artificially damaged wall was prestressed by tendons to improve the shear capacity of the wall, and the other walls were retrofitted by adding steel plate at the surface for the same purpose. Consequently, these retrofitted walls had improved capacity and stiffness in both shear and flexure. Especially, the wall with steel plate showed ductile behavior after ultimate load and the prestressed wall had greater stiffness than the unstrengthened prototype wall.

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Mei, Kui Hua, Zhi Tao Lv, and Ji Wen Zhang. "The Static Test Study on Anchors of CFRP Cables." Advanced Materials Research 671-674 (March 2013): 1635–40. http://dx.doi.org/10.4028/www.scientific.net/amr.671-674.1635.

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The axial performance of CFRP is excellent, while the lateral compression strength and shear strength are low, thus they can’t be anchored by traditional anchors. A new type of adhesive anchor was designed and five experimental cables were fabricated and the static tests were carried out. In the tests, the tensile capacity, bond strength and pullout behavior of CFRP cables anchors filled with resin were discussed. The efficiency coefficients and the load-slip behaviors of the bond-type anchors and the uniformities of the stresses in the tendons were studied. Several conclusions are drawn which have become powerful evidences for using the bond-type anchors in the first cable stayed bridge with CFRP cables in China.

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Hassanin, A. I., and H. F. Shabaan. "Effects of Uniform Load on Externally Post-tensioning Composite Beams under Multiple Degrees of Shear Connection." IOP Conference Series: Earth and Environmental Science 1026, no. 1 (May 1, 2022): 012024. http://dx.doi.org/10.1088/1755-1315/1026/1/012024.

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Abstract Composite beams (steel and concrete) are used widely as the main structural elements in flexure in bridges and buildings. Such structures' design life would be decreased if the loads increased or if environmental deterioration could occur. Such modifications can reduce the strength of these members and therefore need to be considered for replacement or retrofitting.The current study presents an evaluation of the effect of shear connection with its different degrees from partial to full for the composite beams strengthened with post-tensioning tendons. It is known by design that the use of partial shear connection in composite beams requires that the sliding capacitance of the shear connectors shouldn’t be less than the maximum slip so that the composite section can reach the ultimate design load. The degree of shear connection over which the composite section is designed, as well as the span length of the beam, are the most important factors governing the maximum slip limit. This study was performed using numerical modelling by the finite element analysis method to simulate the bending behaviour of composite steel beams under uniform loading cases which were strengthened with three shapes of tendons profiles. The results of two finite element models have been compared with experimental results obtained from previous literature related to the same topic. This comparison was made to ensure the efficiency, effectiveness, and accuracy of the model used, using ANSYS Workbench Software.

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Elbelbisi, Ahmed H., Alaa A. El-Sisi, Hilal A. Hassan, Hani A. Salim, and Hesham F. Shabaan. "Parametric Study on Steel–Concrete Composite Beams Strengthened with Post-Tensioned CFRP Tendons." Sustainability 14, no. 23 (November 28, 2022): 15792. http://dx.doi.org/10.3390/su142315792.

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A sustainable environment can be achieved by strengthening the existing building to avoid new construction and by replacing the construction materials with long-lasting sustainable materials such as a fiber-reinforced polymer (FRP). Using post-tensioned (PT) FRP systems has proven to be an effective technique in strengthening the structure and decreasing cracks and deformability. In this study, a 3-D finite element model was built to investigate the flexural behavior of composite beams strengthened with external PT FRP tendons. Limited research studied the use of FRP tendons to enhance the structural behavior of composite beams. This paper represents a comprehensive study of the effect of several parameters that control the design of the FRP tendons. Parameters such as PT level, tendon material, tendon length, degree of shear connection (DOSC), and tendon profile shape were considered under loading. The 3-D model’s correctness is validated using published experimental data. It was observed that of all FRP materials, carbon FRP is the best type for upgrading the beam strength, and it was recommended to use a 30 to 40% PT level. In addition, applying external PT over the full length of the beam increases the ultimate load capacity significantly. However, due to the difficulty of construction, it was recommended to use 90% of the beam span length since the difference in beam capacity does not exceed 5%. Finally, adding PT tendons with a trapezoidal and parabola profile to composite beams significantly increases the yield load and the beam capacity.

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Journal articles on the topic 'Shear strength of unbonded tendons'

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