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1
Küsel, Frank, Elsabe Kearsley, Liam J. Butler, Sarah A. Skorpen, and M. Z. E. B. Elshafie. "Measured temperature effects during the construction of a prestressed precast concrete bridge beam." MATEC Web of Conferences 199 (2018): 11013. http://dx.doi.org/10.1051/matecconf/201819911013.
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Prestress losses in precast concrete beams include the short-term effects of elastic shortening and the long-term effects of concrete shrinkage, concrete creep and steel relaxation. Temperature effects are, however, excluded. The aim of this research was to monitor the behaviour of a prestressed precast concrete bridge beam, focussing on temperature effects and destressing. Successful monitoring assists in comparing the real performance of a structure to the expected design performance, and in managing the durability of the monitored structure. The effect of temperature variation on strains in prestressed beams was investigated by instrumenting a precast beam. Temperature and strains were monitored from the day of casting up to and including the cutting of the pretensioning strands. Daily temperature variations causing vertical non-linear temperature profiles resulted in internal strains of up to 28 % of the strains caused by destressing. It was therefore concluded that thermal effects before destressing resulting from elevated curing temperatures and daily temperature changes should be considered in the calculation of prestress losses. The monitoring techniques used were successful in determining the stresses and strains within the beam, which can be used to compare real prestress losses with the losses assumed in design.
2
Navrátil, Jaroslav, and Lukáš Zvolánek. "Shear at the Interface between Composite Parts of Prestressed Concrete Section." Applied Mechanics and Materials 752-753 (April 2015): 763–68. http://dx.doi.org/10.4028/www.scientific.net/amm.752-753.763.
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Composite concrete beams made of prefabricated prestressed or non-prestressed element and cast-in-place reinforced concrete slab became very popular in present-day civil engineering practice. Two concrete composite parts of beam are cast at different times. Different moduli of elasticity, consecutive load application, and differential creep and shrinkage cause unequal strains and stresses in two adjacent fibers of construction joint. The requirement is to ensure that both parts act fully compositely, because the bending and shear designs of composite members are based on this assumption. Therefore the level of shear stresses at the interface between two parts must be limited. The objective of the paper is to review the methods for the calculation of shear stresses in construction joint, and to evaluate the influence of different age of two concrete composite parts on the level of shear stresses. Calculation method alternative to Eurocode 2 method is proposed and tested. It is recommended to calculate the shear stress from difference of normal forces acting on sectional components in two neighboring sections of the element. It was observed that differential shrinkage of concrete components can significantly affect the stress distribution. Numerical studies were performed based on real-life examples of composite beams.
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Al-Ilani, Mohamad, and Yehya Temsah. "Comparative study of modeling methods used to simulate initial stresses in prestressed beams towards manual analysis." MATEC Web of Conferences 281 (2019): 01014. http://dx.doi.org/10.1051/matecconf/201928101014.
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Numerical modeling of the prestressing element that generates prestressed effect in beams has always been considered a big challenge. This research compares two methods of modeling; In the first method we used initial stresses predefined stress and in the second method we used the temperature strain. Concrete damage plasticity model (CDP) was used to model the non-linear behavior of concrete material and an elasto-plastic behavior was applied to ordinary and prestressed reinforcement. Truss elements were used to model ordinary and prestressed reinforcement embedded inside the concrete. As a result, Initial Temperature load method showed less error in bottom and top stresses and cambering of beam in comparison with the basic concept method, than predefined method.
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Kennedy, John B., Saddallah Chami, and Nabil F. Grace. "Dynamic and fatigue responses of prestressed concrete girders with openings." Canadian Journal of Civil Engineering 17, no. 3 (June 1, 1990): 460–70. http://dx.doi.org/10.1139/l90-050.
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The influences of opening size, eccentricity, and location on the natural frequencies, mode shapes, damping, and deformation response of prestressed beams and girders with openings under both dynamic and cyclic loadings are presented. A theoretical study was conducted by the finite element method to determine the above structural responses for prestressed rectangular, T- and I-beams. The results were verified and substantiated by tests on six post-tensioned concrete beams. Good agreement was shown between the theoretical and experimental results. Furthermore, it was shown that cyclic loading can have a significant influence on the amplitudes of vibration and the structural response of the top and bottom chords of the opening, and a very significant effect on the tensile strains on the side of the opening resulting from the initial prestressing. Design suggestions are made. Key words: design, dynamic, fatigue, frequencies, girders, openings, prestressed concrete, stresses, structures, tests.
5
Pažma, Peter, Viktor Borzovič, and Jaroslav Halvonik. "Secondary Effects of Prestressing at ULS on Hyperstatic Structures." Key Engineering Materials 691 (May 2016): 138–47. http://dx.doi.org/10.4028/www.scientific.net/kem.691.138.
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Secondary (parasitic) effects of prestressing develop in hyperstatic structures (continuous beams) due to restraining of imposed deformation by hyperstatic restraints. These effects may, in some case, significantly influence internal forces and stresses in prestressed structures. Internal forces due to the secondary effects should be included in design combinations for verification of both ultimate and serviceability limit state. Because secondary effects are influenced by structural system, there is a question how they will change after changing of the structural system e.g. due to development of plastic hinge (s) in a critical cross-section (s) or after development of kinematic mechanism?This article describes an experimental program at Slovak University of Technology in Bratislava, Department of concrete structures and bridges and its results. Program were focused on investigation of behavior of continuous post-tensioned beams with significant secondary effects of prestressing subjected to ultimate load. Together six, two span beams were tested, with maximum load changing structural system into kinematic mechanism. Secondary effects of prestressing were detected by measurement of reactions in all supports, further there were measured displacements in the quarters of both spans and strains in critical sections of the beams.
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Kovács, I. "Structural performance of steel fibre reinforced concrete — Part I. Overview of the experimental program." International Review of Applied Sciences and Engineering 5, no. 1 (June 1, 2014): 9–19. http://dx.doi.org/10.1556/irase.5.2014.1.2.
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Abstract The papers of the series deal with experimental characterisation of mechanical as well as structural properties of different steel fibre reinforced concretes that can be used for several structural applications. An extensive experimental programme (six years) has been developed to investigate the effect of steel fibre reinforcement on the mechanical performance and structural behaviour of concrete specimens. Specimens and test methods were selected to be able to detect realistic behaviour of the material, representing clear effect on the structural performance. Material compositions, test methods, type of test specimens will be detailed in the presented paper (Part I). Furthermore, compressive strength (Part II), stress-strain relationship (Part II), splitting strength (Part III) and toughness (Part IV) will also be discussed. In the light of the motivation to determine the structural performances of 1D concrete structural element affected by steel fibre reinforcement, bending and shear behaviour (Part V) as well as serviceability state (Part VI) of steel fibre reinforced concrete beams will be analysed. Since normal force — prestressing force — can affectively be used to improve the structural performances of RC element flexural tests were carried out on prestressed pretensioned steel fibre reinforced concrete beams (Part VII). Moreover, focusing on the in-plane state of stresses for 2D structures, behaviour of steel fibre reinforced concrete deep beams in shear and steel fibre reinforced concrete slabs (Part VIII) in bending will be explained. Finally, based on the wide range of the experimental and analytical studies on the presented field, a new material model for the 1D uniaxial behaviour (Part IX) and its possible extension to the 3D case (Part X) will be described hereafter. All papers will put emphasis on the short literature review of the last four decades.
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Jia, Jin Qing, Fang Yu, Da Li Yao, and Wei Qing Zhu. "Strain Analysis of Corrosed Prestressed Concrete Beams on Fatigue Test." Advanced Materials Research 255-260 (May 2011): 355–59. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.355.
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In order to study the relationship between strains and corrosion levels of prestressed concrete beams uder fatigue loading, accelerated corrosion method is used to make various corrosion rates of prestressed steel strands. The beams have the same designs and submitted to the same maximum and minimum load during the test. With the corrosion level as main parameter, strains at different position of the beams, such as non-prestressed steel strain, concrete strain in compressive region at mid-span and prestressed steel strain are studied. The test results show that beams with different corrosion rates have the same “three-stage“ law on the development of non-prestressed steel maximum and residual strain,as well as concrete strain and prestress strain. The significant increase of concrete strain is generated due to corrosion after concrete cracking.The increase of non-prestressed steel strain is nearly proportional to the growth of corrosion under the same fatigue load. A relationship was found to be a function. It can be obtained the corrosion rate of prestressed steel when the stress of non-prestressed steel strains are measured.
8
Alnuaimi, A. S. "Comparison between Experimental and 3D Finite Element Analysis of Reinforced and Partially Pre-Stressed Concrete Solid Beams Subjected to Combined Load of Bending, Torsion and Shear." Journal of Engineering Research [TJER] 5, no. 1 (December 1, 2008): 79. http://dx.doi.org/10.24200/tjer.vol5iss1pp79-96.
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This paper presents a non-linear analysis of three reinforced and two partially prestressed concrete solid beams based on a 20 node isoparametric element using an in-house 3D finite element program. Anon linear elastic isotropic model, proposed by Kotsovos, was used to model concrete behaviour, while steel was modelled as an embedded element exhibiting elastic-perfectly plastic response. Allowance was made for shear retention and for tension stiffening in concrete after cracking. Only in a fixed direction, smeared cracking modelling was adopted. The beams dimensions were 300x300 mm cross section, 3800 mm length and were subjected to combined bending, torsion and shear. Experimental results were compared with the non-linear predictions. The comparison was judged by load displacement relationship, steel strain, angle of twist, failure load, crack pattern and mode of failure. Good agreement was observed between the predicted ultimate load and the experimentally measured loads. It was concluded that the present program can confidently be used to predict the behaviour and failure load of reinforced and partially prestressed concrete solid beams subjected to a combined load of bending, torsion and shear.
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Selvachandran, P., S. Anandakumar, and K. L. Muthuramu. "Deflection of Steel Reinforced Concrete Beam Prestressed With CFRP Bar." Archives of Metallurgy and Materials 62, no. 3 (September 26, 2017): 1915–22. http://dx.doi.org/10.1515/amm-2017-0289.
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AbstractCarbon Fiber Reinforced polymer (CFRP) bars are weak in yielding property which results in sudden failure of structure at failure load. Inclusion of non-pretensioned steel reinforcement in the tension side of CFRP based prestressed concrete beam will balance the yielding requirements of member and it will show the definite crack failure pattern before failure. Experimental investigation has been carried out to study the deflection behavior of partially prestressed beam. Experimental works includes four beam specimens stressed by varying degree of prestressing. The Partial Prestressing Ratio (PPR) of specimen is considered for experimental works in the range of 0.6 to 0.8. A new deflection model is recommended in the present study considering the strain contribution of CFRP bar and steel reinforcement for the fully bonded member. New deflection model converges to experimental results with the error of less than 5% .
10
Huang, Dongzhou, and Mohsen Shahawy. "Analysis of Tensile Stresses in Transfer Zone of Prestressed Concrete U-Beams." Transportation Research Record: Journal of the Transportation Research Board 1928, no. 1 (January 2005): 134–41. http://dx.doi.org/10.1177/0361198105192800115.
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Prestressed U-beam bridges compare favorably in cost and appearance to traditional concrete I-beam bridges. Consequently, U-beam bridges are gaining in popularity and usage, especially when aesthetic issues are deemed important. U-beam bridges first appeared in Florida in 2000; however, during construction, cracks developed in the webs of the U-beams. This paper presents results of an analysis of representative cracking of U-beams and proposes a practical method for the transfer zone stirrup design. For the purpose of the analysis, the U-beam is divided into a series of finite shell-plate elements, and the prestressing tendons are simulated as a number of concentrated forces. Two different mechanical models of the U-beams are developed on the basis of the stages of construction. Analytical results show that high tensile stresses occur in the end zone of the U-beam because of the prestressing tendons and that these tensile stress must be properly considered in bridge design. The research results are applicable to the design of prestressed U-beams and similar types of prestressed girders.
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Hu, Di, Lai Fa Wang, and Ji Ping Guo. "Calculation of Short-Term and Long-Term Behavior of Prestressed Concrete Box Girders Considering Effect of Shear Lag." Key Engineering Materials 400-402 (October 2008): 943–48. http://dx.doi.org/10.4028/www.scientific.net/kem.400-402.943.
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A set of formulae to calculate short-term behavior of simply supported prestressed concrete box girders under dead load and prestress are established based on energy method, in which shear lag and effect of prestressed steel and non-prestressed steel are taken into account. As the time-dependent relationship between stress and strain of concrete, equilibrium of sectional forces and compatibility equation are introduced, a novel approach to analyze long-term behavior of prestressed concrete box girders is presented, and the theoretical formulae considering the synthetic effect of creep and shrinkage of concrete, relaxation of prestressed steel, shear lag and restriction of steels are deduced, which can be used directly to calculate time-dependent deflection of box girder, stresses and strains of concrete and steel at any location at any time. Comparison of theoretical values shows that that the long-term deflection increases by shear lag while distribution of transverse concrete stresses become even by concrete creep and shrinkage.
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Shen, Kongjian, Shui Wan, YL Mo, and Xiayuan Li. "A softened membrane model for prestressed concrete composite box girders with corrugated steel webs under pure torsion." Advances in Structural Engineering 22, no. 2 (August 3, 2018): 384–401. http://dx.doi.org/10.1177/1369433218788597.
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Torsion can be regarded as a principal factor in some cases, such as in curved girders and eccentrically loaded girders, when conducting the structural analysis of prestressed concrete composite box girders with corrugated steel webs. Recently, a rational model, called the softened membrane model for torsion, was proposed for the torsional analysis of reinforced concrete members; thereafter, this model was extended to prestressed concrete members under pure torsion and called softened membrane model for torsion prestressed concrete. This article presents a modified model, the softened membrane model for torsion prestressed concrete for prestressed concrete composite box girders with corrugated steel webs, to analyze full torsional behavior. To build the model, the softened membrane model for torsion in reinforced concrete members is first extended to perform the torsional analysis of prestressed concrete composite box girders with corrugated steel webs by incorporating the torsional contribution of corrugated steel webs. Afterward, the initial stresses and strains due to prestressing are considered to extend the softened membrane model for torsion to softened membrane model for torsion prestressed concrete for prestressed concrete composite box girders with corrugated steel webs by modifying the equilibrium equations, convergence criteria, and constitutive laws of materials. The modified model is validated by experimental data and is proven to be capable of predicting the overall torque–twist curve, especially the precracked branch and postcracked ascending branch. In addition, a comparison between the softened membrane model for torsion and softened membrane model for torsion prestressed concrete indicates that the torque values before and after concrete cracking will be overestimated and underestimated, respectively, without considering the effect of the initial stresses and strains. Finally, another comparison shows that the softened membrane model for torsion prestressed concrete is superior to the rotating-angle truss model for torsion in its ability to predict the precracked branch of the torque–twist curve.
13
Guo, Yong Chang, Jian He Xie, and Di Liu. "Interface Properties of Cracked RC Beams Strengthened with Prestressed Hybrid FRP - Part II: Crack Location." Advanced Materials Research 243-249 (May 2011): 5483–86. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.5483.
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This study is the second part of investigation into the interface mechanical performances of cracked reinforced concrete (RC) beams strengthened with prestressed hybrid fiber reinforced polymer (HFRP). Four cases of difference crack location are considered by establishing finite element analysis models to discuss the effort of crack location on the interface stresses in the strengthened beams. The analysis results indicate that the flexural crack obviously changes the distributing of the interface stresses, and an abrupt increase of the stresses arise at the crack location. Moreover, when the crack location is closer from the interface end, the change rate of the stresses is larger.
14
Rashid, Muhammad U., Liaqat A. Qureshi, and Muhammad F. Tahir. "Investigating Flexural Behaviour of Prestressed Concrete Girders Cast by Fibre-Reinforced Concrete." Advances in Civil Engineering 2019 (April 1, 2019): 1–11. http://dx.doi.org/10.1155/2019/1459314.
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The main objective of this research was to investigate the effect of adding polypropylene and steel fibres on flexural behaviour of prestressed concrete girders. Although the construction industry is frequently using prestressed concrete to increase the load-carrying capacity of structures, it can be further enhanced by using fibres. In this paper, experimental work was carried out to encourage the construction industry in utilizing fibres in prestressed concrete members to improve the mechanical properties of these members. As past investigations on fibre-reinforced prestressed beams were limited, the present work was done on small-scale fibre-reinforced I-shaped prestressed concrete girders. Six small-scale prestressed concrete girders were cast comprising a control girder, a hybrid girder, two girders with varying percentages of steel fibres, and two girders with varying percentages of polypropylene fibres. These girders were tested by centre point loading up to failure. It was concluded that, by the addition of small volume fraction of fibres, not only the ductility but also the tensile strength and flexural strength of FRC girders could be improved. It also altered the failure pattern positively by enhancing large strains in concrete and steel. Steel fibre-reinforced concrete showed higher energy absorption and deflection at ultimate loads in comparison to other specimens.
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Moravcik, Martin, and Lukas Krkoska. "Long-Term Effects Monitoring on Prestressed Concrete Bridge." Key Engineering Materials 691 (May 2016): 250–58. http://dx.doi.org/10.4028/www.scientific.net/kem.691.250.
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Balanced cantilever method is one most used method for the large span concrete bridge construction. Generally non-homogenous concrete structures with changing the structural system within its erection are sensitive to the deformation and stress prediction in time. Long-term monitoring system has become very important tool which enables to obtain basic information about actual structural behavior in time about stress and deformation level. It can also cover the other structural effects for example the temperature influence which can significantly affect to the later structural behavior. Generally bridge designers in practice do not have enough information about these influences within the structure erection over the time. Underestimating such above mentioned effects often causes that predicted values of stresses or deformation does not corresponded with the reality as was published for example in [1]. In boundary cases unexpected excessive deformations or crack opening due to the stresses distribution may lead to the serviceability problems, deterioration of aesthetics, and even early reconstruction of the bridge eventually. In this paper we would like to present some experiences with the long-term monitoring of bridge structure and performed structural analysis considering the real load history and structural scheme changing. Recorded strains development was compared with the numerical model results based on the expected behavior of prestressed concrete structure according to the European standard models, [3, 4].
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SOUZA JUNIOR, O. A., and D. R. C. OLIVEIRA. "Influence of the cable´s layout on the shearing resistance of prestressed concrete beams." Revista IBRACON de Estruturas e Materiais 9, no. 5 (October 2016): 765–95. http://dx.doi.org/10.1590/s1983-41952016000500008.
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Abstract Little information on experimental investigations regarding the influence of the prestressing forces in the shear resistance of prestressed beams is found in the technical literature. Thus, it was experimentally evaluated the shear resistance of six post-tensioned prestressed concrete beams with cross section of (150 x 450) mm2, total length of 2400 mm and concrete's compressive resistance of 30 MPa, with the variables of this work being the layout of the prestressing cable, straight or parabolic, and the stirrups geometric rate. Verticals displacement, steel and concrete's strains and a comparison of the experimental loads with the estimates of ACI 318, EUROCODE 2 and NBR 6118: 2014 codes are presented and discussed. The results showed that the cable's parabolic layout increased the beams' shear resistance in up to 16% when compared to beams with straight cables.
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McKay, K. S., and M. A. Erki. "Flexural behaviour of concrete beams pretensioned with aramid fibre reinforced plastic tendons." Canadian Journal of Civil Engineering 20, no. 4 (August 1, 1993): 688–95. http://dx.doi.org/10.1139/l93-085.
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The durability of reinforced concrete structures has become an increasing concern as our infrastructure ages. In particular is the deterioration of steel reinforcements when used in concrete structures exposed to severe corrosive environments. This paper investigates the feasibility of using noncorroding aramid fibre reinforced plastic (AFRP) tendons as a substitute for steel strand in pretensioned concrete applications. Three AFRP pretensioned beams, 150 × 300 × 2100 mm, were tested under static and cyclic loading. These results indicate that load capacities of the beams were not affected by the cyclic loading. Ultimate strengths were generally greater than predicted, primarily as a result of the ability of the AFRP rods to develop greater tensile stresses than expected. Key words: prestressed concrete, nonmetallic tendons, aramid fibres, advanced composite materials.
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Zhang, Jun, Lang Ni Deng, and Ling Liao. "Calculation Methods for Flexural Capacity of Normal Section of Concrete Beams Strengthened with Prestressed CFRP Plates." Advanced Materials Research 671-674 (March 2013): 632–35. http://dx.doi.org/10.4028/www.scientific.net/amr.671-674.632.
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Existing experimental studies showed that the reinforced concrete (RC) beams strengthened with prestressed carbon fiber-reinforced polymer (CFRP) plates had two possible flexural failure modes (including the compression failure and tension failure) according to the CFRP reinforcement ratio. Theoretical formulas based on the compatibility of strains and equilibrium of forces were presented to predict the nominal flexural strength of strengthened beams under the two failure modes, respectively. It can provide a reference for engineering application of strengthening design.
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Saraswathy, Velu, Han-Seung Lee, Subbiah Karthick, and Seung-Jun Kwon. "Stress Corrosion Behavior of Ungrouted Pretensioned Concrete Beams." Advances in Materials Science and Engineering 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/8585162.
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Prestressed concrete beams of size 150 × 150 × 1000 mm were designed, and two bonded cold-drawn 7 mm steel wires were stressed at 70% UTS under service conditions before concreting. The beams were cast with M40 grade concrete mix with various percentages of chlorides ranging from 0, 1, 2, and 3% by weight of cement and cured for 28 days. After 28 days, the stretching forces were released, the prestressing steel wire was allowed to regain its original length, the tensile stresses were transformed into a compressive stress in the concrete, and the stress corrosion behavior was assessed. Stress corrosion cracking (SCC) is due to the simultaneous action of stress, corrosive media, and material properties. The stress corrosion behavior of ungrouted pretensioned steel was assessed by using various electrochemical techniques such as electrochemical noise, open-circuit potential measurement, AC impedance, and potentiodynamic polarization measurements. The same experiments were conducted for rebars embedded in the concrete beam with various percentages of chlorides ranging from 0, 1, 2, and 3% by weight of chloride. After 30 days of exposure, the beams were tested for their flexural strength measurements to find out the load-bearing capacity.
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Zhou, Shi-Jun. "Effect of Construction Method on Shear Lag in Prestressed Concrete Box Girders." Mathematical Problems in Engineering 2012 (2012): 1–17. http://dx.doi.org/10.1155/2012/273295.
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Most of the previous researches conducted on shear lag of box girders were only concerned about simple types of structures, such as simply supported and cantilever beams. The structural systems concerned in these previous researches were considered as determined and unchangeable. In this paper, a finite element method considering shear lag and creep of concrete was presented to analyze the effect of dynamic construction process on shear lag in different types of concrete box-girder bridges. The shear lag effect of the three types of a two-span continuous concrete beam classified by construction methods was analyzed in detail according to construction process. Also, a three-span prestressed concrete box-girder bridge was analyzed according to the actual construction process. The shear lag coefficients and stresses on cross sections along the beam including shear lag were obtained. The different construction methods, the changes of structural system with the construction process, the changes of loading and boundary conditions with the construction process and time, the prestressing, and creep were all imitated in the calculations. From comparisons between the results for beams using different construction methods, useful conclusions were made.
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Atta, Ahmed. "Finite Element Analysis of External Prestressing Beams Made of Strain Hardening Material." Applied Mechanics and Materials 166-169 (May 2012): 259–68. http://dx.doi.org/10.4028/www.scientific.net/amm.166-169.259.
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The use of finite element analysis has been widely used as a means to analyze individual elements and the effects of concrete strength under loading. This paper is a study of prestressed concrete beams made of strain hardening material called UHP-SHCC (Ultra High Performance Strain Hardening Cementitious Composite) using finite element analysis to understand their response. A finite element model is studied and compared to experimental data. The basic parameters included second order effect of prestressed beam, and prestressing tendon depths have been considered in the analysis. The present study indicated the following conclusions: the number of deviators significantly influences the ultimate capacity and the strains values of UHP-SHCC beams, the change of external prestressing tendon depth has a significant effect on the cracking load, failure load, deflection values, and ultimate stress in the tendon in case of using UHP-SHCC beams but keep the final mode of failure without change.
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Huo, Xiaoming (Sharon), and Maher K. Tadros. "Structural Design of High-Performance Concrete Bridge Beams." Transportation Research Record: Journal of the Transportation Research Board 1696, no. 1 (January 2000): 171–78. http://dx.doi.org/10.3141/1696-59.
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Recently high-performance concrete (HPC) has been used in highway bridges and has gained popularity for its short-term and prospective long-term performances. Benefits of using HPC include fewer girder lines required, longer span capacity of girders, reduced creep and shrinkage deformation, less prestress losses, longer life cycle, and less maintenance of bridges. Research has been conducted on several issues of structural design of HPC bridge beams. The topics discussed include the effects of section properties of prestressed concrete girders, allowable tensile and compressive stresses, creep and shrinkage deformations of HPC, and prediction of prestress losses with HPC. The results from a parametric study have shown that a section that can have a large number of strands placed in its bottom flange is more suitable for HPC applications. The use of 15-mm-diameter prestressing strands allows the higher prestressing force applied on sections and can provide more efficiency in HPC bridges. The research results also indicate that the allowable compressive strength of HPC has a major effect on the structural design of bridges, whereas the allowable tensile stress has a minor effect on the design. Equations for predicting prestress losses based on the experimental and analytical results are recommended. The recommended equations consider the effects of lower creep and shrinkage deformations of HPC.
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Pereira, S. R., J. M. Calixto, and T. P. Bortone. "Numerical analysis of prestressed hollow core slabs under long term loading." Revista IBRACON de Estruturas e Materiais 6, no. 4 (August 2013): 613–22. http://dx.doi.org/10.1590/s1983-41952013000400007.
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This paper presents a numerical analysis of prestressed hollow core slabs under long term loading. The model considers the time dependence of material and rheological properties in order to predict the actual stage of displacements, strains and stresses. It also takes into account load changes. For the analysis, each slab is divided in a finite number of bar elements, in which the cross section is described in concrete elements, parallel to the flexural axis, and prestressed steel elements. For the results evaluation, the effective concrete area is considered. The numerical results are compared with experimental tests performed on two series of prestressed hollow core slabs. Each series had a different geometry, rate and distribution of prestressing strands. Mid-span displacements were evaluated up to 127 days after initial loading. Good correlation was achieved with both series at and below the service load level.
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Razaqpur, A. G., Mostafa Nofal, and M. S. Mirza. "Nonlinear analysis of prestressed concrete box girder bridges under flexure." Canadian Journal of Civil Engineering 16, no. 6 (December 1, 1989): 845–53. http://dx.doi.org/10.1139/l89-127.
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One-seventh scale direct models of single-cell and two-cell prestressed concrete box girder bridges, tested to destruction at McGill University, are analyzed by the nonlinear finite element technique. The nonlinear program NONLACS, utilized in the analysis, is described in detail together with the material models employed. The objective of the current study is to demonstrate the capabilities of the finite element program NONLACS in predicting the ultimate strength and complete response of prestressed concrete box girder bridges at all stages of loading up to the ultimate load. The load–deflection curves, concrete and steel stresses, and deflected shapes of the bridges at different load levels are compared with the corresponding experimental data. The results verify the applicability of the nonlinear finite element method as an economical and expedient alternative, in some cases, to expensive experimental work aimed at the investigation of the complete response of complex structures to applied loads. Key words: box girder bridges, concrete, concrete and steel strains, experimental data, finite element, load–deflection characteristics, nonlinear analysis, prestressing.
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KOLCHUNOV, V. I., К. YU KUZNETSOVA, and S. S. FEDOROV. "CRACK RESISTANCE OF PRESTRESSED REINFORCED CONCRETE FRAME STRUCTURE SYSTEMS UNDER SPECIAL IMPACT." Building and reconstruction 95, no. 3 (2021): 15–26. http://dx.doi.org/10.33979/2073-7416-2021-95-3-15-26.
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A variant of the crack resistance criterion and the strength criterion of plane-stressed structures made of high-strength fiber-reinforced concrete, fiber-reinforced concrete is proposed. The criteria are based on the theory of plasticity of concrete and reinforced concrete G.A. Genieva. In general, the condition for crack resistance of a plane-stressed fiber-reinforced concrete element is presented in the form of an ellipse with jumps on the coordinate axes of the main reduced stresses. The strength condition of a fiber-reinforced concrete element is described by a complex figure that takes into account cracking in the element under a plane stress state. The characteristic points on the coordinate axes are calculated from the physical and mechanical characteristics of concrete strength, obtained as a result of testing high-strength fiber-reinforced concrete for uniaxial compression and uniaxial tension with “dissolved” fiber in the concrete body and reinforcement reduced to concrete. The results of a comparative analysis of the criteria for crack resistance and strength of high-strength concrete and high-strength fiber-reinforced concrete are given, depending on the percentage of fiber in the concrete body and the type of fiber used. The proposed analytical dependences can be used to analyze the crack resistance and strength of plane-stressed reinforced concrete beams-walls reinforced with fiber, corner zones of shallow shells and other plane-stressed structures made of high-strength fiber-reinforced concrete and fiber-reinforced concrete.
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Zhao, Shun Bo, Song Wei Pei, Yang Wei Wang, and Xi Jian Liang. "Loading Behaviors of Superposed Aqueduct Affected by Segregating Layer Between PPCBs and Cast-In Situ RCF." Applied Mechanics and Materials 37-38 (November 2010): 614–18. http://dx.doi.org/10.4028/www.scientific.net/amm.37-38.614.
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Combined with the structural design of left-shore drainage aqueducts in China South-to-north Water Transfer Project, the structure of cast-in-situ reinforced concrete flume (RCF) with wide and shallow drainage section superposed on longitudinal precast prestressed concrete beams (PPCBs) was drafted. The 3D finite element models were built to study the normal service behaviors of the aqueduct with or without segregating asphalt layer between RCF and PPCBs. The results show that the segregating asphalt layer changes the structural compositions of aqueduct subjecting water loads and results in some effects on loading capacities of the PPCBs and the RCF, such as the larger displacement and tensile stress of PPCBs, the many longitudinal sections of subplate in whole tensile state with larger tensile stresses and the larger vertical tensile stresses at internal surface of sidewall. It provides valuable reference for designing the same kind of aqueduct.
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Jokūbaitis, Vidmantas, and Linas Juknevičius. "ANALYSIS OF METHODS FOR CALCULATING THE WIDTH OF NORMAL CRACKS IN REINFORCED CONCRETE STRUCTURES." Engineering Structures and Technologies 1, no. 1 (May 17, 2009): 23–39. http://dx.doi.org/10.3846/skt.2009.03.
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The width of normal cracks at the level of tensile reinforcement was calculated according to various methods using the data obtained from experimental tests on reinforced concrete beams (without reinforcement pre-stress), pre-cast reinforced concrete slabs and ribbed roof slabs. Th e numerical results were compared to actual crack widths measured during the experimental tests. Also, the crack widths of pre-stressed reinforced concrete beams were calculated according to various methods and compared with each other. Th e following conclusions were reached based on the analysis of numerical and experimental results: 1) Design stresses in tensile reinforcement calculated according to [STR] and [EC] design codes are very similar, although the calculation of such stresses is more logical and simple according to [EC]. Design stresses calculated according to [RU] are greater due to the estimation of the plastic deformations of concrete in the compressive zone. Th e method proposed by Rozenbliumas (Розенблюмас 1966) estimates tensile concrete above the crack peak, and thus allows a more accurate calculation of stresses in tensile reinforcement (Fig 3). Therefore, the latter stresses in pre-stressed RC beams may be decreased by 10–12 %, when height hct ≠ 0 (Fig 1, c) and ratio M/MRd varies between 0,65 and 0,75; 2) The widths of normal cracks in conventional RC beams (subjected to load that corresponds approx. 70 % of their carrying capacity) calculated according to [STR] and [EC] design codes are almost equal to the experimentally obtained crack widths. When beams and slabs are loaded by approximately 52 % of their carrying capacity, design crack widths wk [EC] are approximately 12 % less than wk [STR], although the design crack width wk [RU] is signifi cantly greater. Here, ratio β in the beams and slabs is equal to 2 and 3.3 respectively. Th erefore, the design code [RU] ensures higher probability that the crack width will not reach the limit value (for environmental class XO and XC1) equal in all design codes mentioned in this article; 3) In case of loaded prestressed reinforced concrete beams, the calculated increases of crack widths wk [EC], wk [RU] and w [5] are greater if compared to wk [STR] (Fig 6). Th e increased reinforcement ratio ρ has more signifi cant infl uence on the increases of crack widths calculated according to other design codes if compared to wk [STR]. Tensile concrete above the crack peak has signifi cant infl uence on the design crack width when pre-stressed RC beams are lightly reinforced (ρ ≤ 0,008); 4) During the evaluation of the state of fl exural RC members, expression (5) could be used for calculating the crack width or a position of the neutral axis when the heights of the crack and the tensile zone above the crack are known (calculated or measured experimentally). Design crack widths w (5) are very similar to the experimentally obtained results.
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Benyahi, Karim, Mohand Said Kachi, Youcef Bouafia, Salma Barboura, and Jia Li. "Reliability assessment of the behavior of reinforced and/or prestressed concrete beams sections in shear failure." Frattura ed Integrità Strutturale 15, no. 57 (June 22, 2021): 195–222. http://dx.doi.org/10.3221/igf-esis.57.16.
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The object of this article is to be able to simulate the behavior of reinforced and/or prestressed concrete beam’s section in the shear loading through a model allowing the evaluation of nonlinear strains caused by shear, while taking into account the real behavior of the materials. In this approach, we are often confronted with problems of modeling uncertainties linked to some insufficiencies of the mechanical model allowing to describe the physical phenomena in a realistic way. For that, it is necessary to use a reliability model making it possible to evaluate their probability of failure, by establishing failure curves according to the different transition zones of the limit state curve of the nonlinear behavior in the shear loading up to at section failure of reinforced and/or prestressed concrete beams. In this work, we also propose a coupling of the reliability method by response surface to carry out the reliability optimization on complex mechanical models, where the mechanical and reliability models developed have been implemented on the Fortran. This allows the estimation in an efficient way of the different reliability characteristics according to each transition zone from the limit state curve to the real behavior until failure in the shear loading.
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Flaga, Kazimierz, and Kazimierz Furtak. "Application of Composite Structures in Bridge Engineering. Problems of Construction Process and Strength Analysis." Civil And Environmental Engineering Reports 15, no. 4 (March 1, 2015): 57–85. http://dx.doi.org/10.1515/ceer-2014-0035.
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Abstract Steel-concrete composite structures have been used in bridge engineering from decades. This is due to rational utilisation of the strength properties of the two materials. At the same time, the reinforced concrete (or prestressed) deck slab is more favourable than the orthotropic steel plate used in steel bridges (higher mass, better vibration damping, longer life). The most commonly found in practice are composite girder bridges, particularly in highway bridges of small and medium spans, but the spans may reach over 200 m. In larger spans steel truss girders are applied. Bridge composite structures are also employed in cable-stayed bridge decks of the main girder spans of the order of 600, 800 m. The aim of the article is to present the cionstruction process and strength analysis problems concerning of this type of structures. Much attention is paid to the design and calculation of the shear connectors characteristic for the discussed objects. The authors focused mainly on the issues of single composite structures. The effect of assembly states on the stresses and strains in composite members are highlighted. A separate part of problems is devoted to the influence of rheological factors, i.e. concrete shrinkage and creep, as well as thermal factors on the stresses and strains and redistribution of internal forces.
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Qureshi, Hisham Jahangir, and Muhammad Umair Saleem. "Flexural and Shear Strain Characteristics of Carbon Fiber Reinforced Polymer Composite Adhered to a Concrete Surface." Materials 11, no. 12 (December 19, 2018): 2596. http://dx.doi.org/10.3390/ma11122596.
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The use of Fiber Reinforced Polymer (FRP) composites for strengthening concrete structures has gained a lot of popularity in the past couple of decades. The major issue in the retrofitting of concrete structures with FRP is the accurate evaluation of flexural and shear strains of polymer composites at the bonding interface of epoxy and concrete. To address it, a comprehensive experimental study was planned and carbon fiber reinforced polymer (CFRP) composite was applied on the concrete surface with the help of adhesives. CFRP was used as an external mounted flexural and shear reinforcement to strengthen the beams. Flexural load tests were performed on a group of eight reinforced concrete beams. These beams were strengthened in flexural and shear by different reinforcement ratios of CFRP. The strain gauges were applied on the surface of concrete and CFRP strips to assess the strain of both CFRP and concrete under flexural and shear stresses. The resulting test data is presented in the form of load–deformation and strain values. It was found that the values of strains transferred to the FRP through the concrete are highly dependent on the surface tensile properties of concrete and debonding strength of the adhesive. The test results clearly indicated that the strength increment in flexural members is highly dependent on strain values of the CFRP.
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Walls, Richard, Celeste Viljoen, and Hennie de Clercq. "Parametric investigation into the cross-sectional stress-strain behaviour, stiffness and thermal forces of steel, concrete and composite beams exposed to fire." Journal of Structural Fire Engineering 11, no. 1 (August 24, 2019): 100–117. http://dx.doi.org/10.1108/jsfe-10-2018-0031.
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Purpose This paper aims to provide a parametric investigation into the behaviour of steel, concrete and composite beams exposed to fire. This investigation gives insight into the structural behaviour of elements experiencing thermal and mechanical loading illustrating reasons for observed global structural behaviour, and identifying how selected design parameters influence results obtained. Non-linear heating/thermal bowing behaviour is specifically considered. Design/methodology/approach Cross-sectional stresses and strains, resultant thermal forces, bending stiffness, axial stiffness and deflections are plotted for beams subjected to different fire regimes or input values. The impact of changes in input parameters on beam section properties is illustrated. Unusual structural responses, localised effects and general trends are identified in relation to variations in thermal gradients, concrete tensile capacity, standard fire exposure time and the assumed concrete flange widths of composite beams. Findings Stress-strain plots highlighting cross-sectional structural behaviour, trends in beam properties and the influence of design parameters are provided. Some counter-intuitive behaviour is explained, such as increased member stiffness being offset by increased thermal effects, leading to this parameter having negligible impact on global behaviour but a significant effect on local stresses and strains. Increased concrete strengths may lead to increased thermal deformations, whilst the inclusion of concrete tensile capacity typically has a minimal influence. Research limitations/implications The research focusses on cross-sectional properties, although results generated illustrate how global behaviour is affected. Practical implications Design engineers are made aware of how selected input values influence predicted structural response. Also, localised stress and strain behaviour relative to imposed loads and thermal effects can be identified. Originality/value This paper provides novel insight into the (sometimes counter-intuitive) behaviour of beams exposed to fire, highlighting trends and the influence of important input parameters on predicted response.
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Kim, Sang-Ho, Sun-Jin Han, and Kang Kim. "Nonlinear Finite Element Analysis Formulation for Shear in Reinforced Concrete Beams." Applied Sciences 9, no. 17 (August 25, 2019): 3503. http://dx.doi.org/10.3390/app9173503.
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This study suggests a novel beam-column element formulation that utilizes an equilibrium-driven shear stress function. The beam shear is obtained from the bi-axial states of micro-planes, through matrix condensation and zero vertical traction assumptions. This properly remedies the shear stiffening of a one-dimensional beam-column element, keeping its degrees of freedom to a minimum. For verification of the proposed method, a total of seven shear test results of reinforced concrete (RC) beams were collected from the literature, in which the key variables were the reinforcement ratio, the presence of shear reinforcement, and section shape. The advantages are clearly shown in the shear stresses distributions being accurately described and the global load-displacement relations being successfully obtained and matching well with various test results. The proposed model shows satisfactory descriptions of the monotonic load-displacement response of the RC beams failing in multiple modes that vary from diagonal-tension to flexural-compression. In addition, more accurate and reliable information of sectional responses including sectional shear deformation and stresses is collected, leading to better prediction of a potential shear failure mode. Finally, the advantages of the proposed model are demonstrated by comparing the analysis results of an RCT-beam by using the different shear assumptions that include the constant and parabolic shear strains, constant shear flow, and the proposed shear stress function.
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Wang, Li, Wei Ming Yan, Hao Xiang He, and Wei Wang. "Integration, Application and Analysis of the SHM System for Continuous Rigid Frame Bridge." Applied Mechanics and Materials 578-579 (July 2014): 1161–69. http://dx.doi.org/10.4028/www.scientific.net/amm.578-579.1161.
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This paper is aiming to present the whole situation of a three spans prestressed continuous concrete rigid frame bridge’s SHM (structural health monitoring) system. Hardware structure and software exploitation of the system were respectively elaborated combining with the practical application situation, including details of sensors layout, data acquisition, storage and transform, the developing of monitoring and management system, etc. Emphasis is placed on data processing and analyzing which is collected from the bridge in the online continuously, such as modal identification of the measured acceleration responses, calculation of deflection curves in real time, observation of changing strains and stresses on the measuring points.
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Cerruti, Lou M., and Peter Marti. "Staggered shear design of concrete beams: large-scale tests." Canadian Journal of Civil Engineering 14, no. 2 (April 1, 1987): 257–68. http://dx.doi.org/10.1139/l87-038.
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Two large-scale reinforced concrete I-beams were tested to failure. The principal difference between the two specimens was the angle of inclination selected for the diagonal compression field in the web. A 45° inclination was used for specimen CM1 whereas a 31° inclination was used for specimen CM2. The validity of the truss model approach used in design was confirmed by the observed behaviour of the specimens.Diagonal crushing limits given in the Canadian code CAN3-A23.3-M84 were found to be conservative. It is recommended to use these limits for uniformly stressed web regions when applying the staggering concept of shear design. For nonuniformly stressed regions it is proposed to investigate potential failure mechanisms assuming an effective compressive strength of the web concrete of [Formula: see text].Canadian code rules for determining longitudinal bar cutoff locations may be unconservative. To prevent the formation of premature collapse crack mechanisms, it is recommended to extend the bars beyond the theoretical cutoff points by at least one-half of the stirrup spacing. Key words: beams, concrete, deflection, deformation, design, failure, girders, limit design method, reinforcement, shear strength, shear tests, strains, stresses, tests.
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Park, Cheol Woo, and Jong Sung Sim. "Shear Failure Analysis of Concrete Beams Reinforced with Newly Developed GFRP Stirrups." Key Engineering Materials 324-325 (November 2006): 995–98. http://dx.doi.org/10.4028/www.scientific.net/kem.324-325.995.
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Even though the application of fiber reinforced polymer (FRP) as a concrete reinforcement becomes more common with various advantages, one of the inherent shortcomings may include its brittleness and on-site fabrication and handling. Therefore, the shape of FRP products has been limited only to a straight bar or sheet type. This study suggests a new technique to use glass fiber reinforced polymer (GFRP) bars for the shear reinforcement in concrete beams, and investigates its applicability. The developed GFRP stirrup was used in the concrete instead of ordinary steel stirrups. The experimental program herein evaluates the effectiveness of the GFRP stirrups with respect to different shear reinforcing ratios under three different shear span-to-depth testing schemes. At the same shear reinforcing ratio, the ultimate loads of the beams were similar regardless the shear reinforcing materials. Once a major crack occurs in concrete, however, the failure modes seemed to be relatively brittle with GFRP stirrups. From the measured strains on the surface of concrete, the shear stresses sustained by the stirrups were calculated and the efficiency of the GFRP stirrups was shown to be 91% to 106% depending on the shear span-to-depth ratio.
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Derkowski, Wit, and Mateusz Surma. "Influence of concrete topping on behaviour of prestressed Hollow Core floor slabs on flexible supports." Budownictwo i Architektura 12, no. 1 (March 11, 2013): 107–14. http://dx.doi.org/10.35784/bud-arch.2180.
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Slim Floors (SF) are the structures made of the Hollow Core (HC) slabs supported on the slender beams, where the beam height is usually slightly greater than the height of precast slab element. With the increase of the supports' deflection, the deformation of the HC slab occurs, and in consequence, additional transverse normal and shear stresses appear in the precast element, which can cause a diagonal cracking and destruction of external webs of this element. It may also result in longitudinal cracks on bottom surface of the slab. Despite the frequent implementation of this type of structures, the existing standard EN 1168 gave only a brief record of the need to take the reduction in design shear capacity into account, but is not given any calculation procedure.
It is widely believed that reduction of unfavourable effects of shear stress in the HC slab’s web can be achieved by filling the cores with concrete or arrangement of the monolithic layer or concrete topping. The fib guidelines are practically the only one document which allows to determine the shear capacity of SF slabs, including the influence of concrete topping or core filling – brief description of this design model is presented in the paper. In order to determine the effect of concrete topping on the behaviour of prestressed HC slabs on the flexible supports, a number of calculation analyzes were performed, which take into account the effects of thickness of the concrete topping, the value of the friction coefficient between the concrete topping and the precast element, the sequence of concreting of vertical joints and topping layer and the amount of supplementary reinforcement in the topping. The results of the calculations, and the conclusions derived from them, are presented in the article.
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Zhai, Kejie, Hongyuan Fang, Bing Fu, Fuming Wang, and Benyue Hu. "Using Externally Bonded CFRP to Repair a PCCP with Broken Wires under Combined Loads." International Journal of Polymer Science 2019 (October 20, 2019): 1–11. http://dx.doi.org/10.1155/2019/8053808.
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Prestressed concrete cylinder pipe (PCCP) is widely used for long-distance water pipelines throughout the world. However, prestressing wire breakage is the most common form of PCCP damage. For some pipelines that cannot be shut down, a new technique for in-service PCCP repair by externally bonding the pipe with layers of carbon fiber reinforced polymer (CFRP) was proposed. A set of three-dimensional finite element models of the repaired PCCP have been proposed and implemented in the ABAQUS software, which took into account the soil pressure, the weight of the PCCP, the weight of the water, and the hydrostatic pressure. The stress–strain features of the PCCP repaired with CFRP of various thicknesses were analyzed. The stress–strain features of different wire breakage rates for the repaired PCCP were also analyzed. The results showed that the strains and stresses decreased at the springline if the PCCP was repaired with CFRP, which improved the operation of the PCCP. It has been found that the wire breakage rates had a significant effect on the strains and stresses of each PCCP component, but CFRP failed to reach its potential tensile strength when other materials were broken.
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Parfenov, S. G., and M. V. Morgunov. "EXPERIMENTAL INVESTIGATIONS OF THE LOSSES OF PRESTRESSING IN FINE REINFORCED CONCRETE ELEMENTS." Proceedings of the Southwest State University 22, no. 1 (February 28, 2018): 112–17. http://dx.doi.org/10.21869/2223-1560-2018-22-1-112-117.
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The article deals with late losses of prestressing of reinforcement due to shrinkage and creep in fine reinforced concrete structures. Creep deformations can several times exceed the elastic straincaused by load. The most common in practice caseof the development of concrete creep is slowly decreased creeping with timewith a rather high initial rate of the development in the first hours after loading. It is typical for stresses that do not exceed the long-term resistance of concrete. Experimental study of deformation of shrinkage and creep of fine-grained concrete allows us to compare the loss of prestressing due to concrete shrinkage and creep. Usually there is an aggregate effect of these factors, which significantly complicates the study of the processes occurring in concrete during long-term exposures. Basically, the results obtained during testing of concrete prisms are used to compare stress-related properties of concrete, but this is not enough to study the loss of prestressing due to concrete shrinkage and creep and testing should be carried out on elements reinforced with prestressed reinforcement to take into account changes in prestresses and redistribution of stresses on the height of the cross section (depth) of the element with a prolonged action of the prestressing force. The results of experimental studies of rectangular reinforced concrete beams at loadcase of different ages of t = 14, 28, 280 and 320 days are analyzed. The losses from rapid creep, shrinkage losses, total losses from shrinkage and creep are considered. The experimental data are presented in the form of graphs and tables. There was performed comparison of the experimental data with the calculated ones determined according to the current standards, and for shrinkage according to the method proposed by I.I. Ulitsky as well.
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Farhat, Rina. "Thickness of Concrete Cover for Corrosion Protection of Steel Reinforcement and Crack Control." Advanced Materials Research 95 (January 2010): 61–68. http://dx.doi.org/10.4028/www.scientific.net/amr.95.61.
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Thickness of concrete cover positively affects both the protection of the steel against corrosion and the safe transmission of bond forces. On the other hand it affects Crack control inversely, larger concrete cover causes larger crack width, and as a result it yields reduction in the protection of the steel against corrosion. The influence of the distance between the centroid of the longitudinal reinforcement to the neutral axis, and the stress in the tension steel, on the crack width and Crack control, will be examined. Computations will be done using personal computer program developed for nonlinear analysis of rectangular reinforced concrete sections in flexure. The analysis is performed using Stress-strain relationship for confined concrete: parabola – rectangle with decending branch to 0.3 fc at Ecu, followed by horizontal branch. Stress-strain diagram for reinforcing steel, with an inclined top branch with a strain limit of E su . Beams and slabs elements sections will be examined for the flexural moments from the external loads acting at serviceability limit state. This paper will introduce by computing the concrete fibers stresses and strains over the height of the section, for different element thickness, the influence of tension steel stresses and concrete cover thickness on crack control and corrosion protection of steel reinforcement.
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NACHT, P. K. K., and L. F. MARTHA. "Interactive graphics tool for the calculation and serviceability limit state stress check of bonded post-tensioned concrete beams according to brazilian codes via Autodesk Robot Structural Analysis Professional(r)." Revista IBRACON de Estruturas e Materiais 8, no. 3 (June 2015): 427–46. http://dx.doi.org/10.1590/s1983-41952015000300009.
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This work presents an interactive graphics computational tool for the verification of prestressed concrete beams with post-tensioned bonded tendons to the serviceability limit state (SLS) stress check according to the Brazilian code NBR 6118:2014. The tool is an add-in for Autodesk Robot Structural Analysis Professional(r), which serves as a structural modeling platform. With data supplied by the user through a graphics user interface, the program here developed calculates all relevant prestress losses that occur throughout the structure's life-cycle, along with the prestress' equivalent loads during this period. The traditional calculation methods, obtained in the NBR 6118, are presented along with the modifications which had to be implemented in order to allow for incremental loss calculations. Usage examples and results are presented, validating the adopted methodology. At the end of the software's calculation, the user receives two outputs: the prestress' equivalent loads in the Robot model and an Excel spreadsheet. The spreadsheet contains the resultant stresses in the beam and warns whether these are greater than the permissible stresses in the SLS stress check. The loads may then be used in other calculations, such as shear reinforcement.
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Mufti, A. A., B. Bakht, N. Banthia, B. Benmokrane, G. Desgagné, R. Eden, M. A. Erki, et al. "New Canadian Highway Bridge Design Code design provisions for fibre-reinforced structures." Canadian Journal of Civil Engineering 34, no. 3 (March 1, 2007): 267–83. http://dx.doi.org/10.1139/l06-137.
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This paper presents a synthesis of the design provisions of the second edition of the Canadian Highway Bridge Design Code (CHBDC) for fibre-reinforced structures. New design provisions for applications not covered by the first edition of the CHBDC and the rationale for those that remain unchanged from the first edition are given. Among the new design provisions are those for glass-fibre-reinforced polymer as both primary reinforcement and tendons in concrete; and for the rehabilitation of concrete and timber structures with externally bonded fibre-reinforced-polymer (FRP) systems or near-surface-mounted reinforcement. The provisions for fibre-reinforced concrete deck slabs in the first edition have been reorganized in the second edition to explicitly include deck slabs of both cast-in-place and precast construction and are now referred to as externally restrained deck slabs, whereas deck slabs containing internal FRP reinforcement are referred to as internally restrained deck slabs. Resistance factors in the second edition have been recast from those in the first edition and depend on the condition of use, with a further distinction made between factory- and field-produced FRP. In the second edition, the deformability requirements for FRP-reinforced and FRP-prestressed concrete beams and slabs of the first edition have been split into three subclauses covering the design for deformability, minimum flexural resistance, and crack-control reinforcement. The effect of sustained loads on the strength of FRPs is accounted for in the second edition by limits on stresses in FRP at the serviceability limit state.Key words: beams, bridges, concrete, decks, fibre-reinforced-polymer reinforcement, fibre-reinforced-polymer sheets, prestressing, repair, strengthening, wood.
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Ayub, Tehmina, Sadaqat Ullah Khan, and Nasir Shafiq. "Flexural Modelling and Finite Element Analysis of FRC Beams Reinforced with PVA and Basalt Fibres and Their Validation." Advances in Civil Engineering 2018 (2018): 1–18. http://dx.doi.org/10.1155/2018/8060852.
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A flexural capacity model for fibre-reinforced concrete (FRC) beams reinforced with PVA and basalt fibres is suggested for the rectangular beam sections. The proposed models are based on the concept of equivalent stress block parameters for both compressive and tensile stresses, similar to Eurocode and ACI code. The parameters are defined by allowing the conversion of the stress-strain models into equivalent rectangular stress blocks, similar to Eurocode 2. The flexural model is suggested to determine the loading capacity of 21 FRC beams containing up to 3% volume fraction of PVA and basalt fibres without reinforcing bars. In order to investigate the accuracy of the proposed flexure models, finite element analysis (FEA) of the same beams was carried out using the compressive and tensile stress-strain curves. Furthermore, 21 FRC beams subjected to three-point bending were tested. The results of the flexural models showed good agreement with the load-carrying capacity of the tested FRC beams, and the results of FEA of all beams showed a good correlation with the experimental results in terms of the maximum load, load versus midspan deflection patterns, and the maximum tensile strains.
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Bačinskas, Darius, Gintaris Kaklauskas, Viktor Gribniak, and Edgaras Geda. "MECHANICAL SIMULATION OF REINFORCED CONCRETE SLABS SUBJECTED TO FIRE." Technological and Economic Development of Economy 13, no. 4 (December 31, 2007): 295–302. http://dx.doi.org/10.3846/13928619.2007.9637815.
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There are many buildings and civil engineering works under construction which are at risk of fire. The fire resistance analysis of reinforced concrete structures constitutes an important part in their design. However, the analysis of the behaviour of load‐bearing members under high temperature conditions is very complicated. Various factors that influence the behaviour of the members need to be taken into account. Analytical and computation methods have been developed in the field of reinforced concrete building exposed to high temperature or accidental fire. Unfortunately, such models are computationally too demanding and their application are limited even for a simply supported reinforced concrete members (beams, plates etc). In this paper, an attempt has been made to extend application of the Flexural model to stress and strain analysis of flexural reinforced concrete members subjected to high temperature. Constitutive models and key material parameters describing thermo‐mechanical behaviour of concrete and reinforcement are discussed. A powerful calculation technique based on layered approach is briefly described. A numerical example of application of present method for calculating of stresses, strains and curvatures of reinforced concrete slab is presented.
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Lacki, Piotr, Przemysław Kasza, and Anna Derlatka. "Numerical Analysis of Prefabricated Steel-Concrete Composite Floor in Typical Lipsk Building." Civil and Environmental Engineering Reports 27, no. 4 (December 20, 2017): 43–53. http://dx.doi.org/10.1515/ceer-2017-0049.
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Abstract The aim of the work was to perform numerical analysis of a steel-concrete composite floor located in a LIPSK type building. A numerical model of the analytically designed floor was performed. The floor was in a six-storey, retail and service building. The thickness of a prefabricated slab was 100 mm. The two-row, crisscrossed reinforcement of the slab was made from φ16 mm rods with a spacing of 150 x 200 mm. The span of the beams made of steel IPE 160 profiles was 6.00 m and they were spaced every 1.20 m. The steelconcrete composite was obtained using 80×16 Nelson fasteners. The numerical analysis was carried out using the ADINA System based on the Finite Element Method. The stresses and strains in the steel and concrete elements, the distribution of the forces in the reinforcement bars and cracking in concrete were evaluated. The FEM model was made from 3D-solid finite elements (IPE profile and concrete slab) and truss elements (reinforcement bars). The adopted steel material model takes into consideration the plastic state, while the adopted concrete material model takes into account material cracks.
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De Corte, Wouter, Kizzy Van Meirvenne, Veerle Boel, and Luc Taerwe. "Design of Anchorage Zones of Pretensioned Concrete Girders: A Comparison of Nonlinear 3D FEM Results with Measurements on a Full Scale Beam." Applied Sciences 10, no. 22 (November 20, 2020): 8221. http://dx.doi.org/10.3390/app10228221.
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Pretensioned concrete beams are widely used for constructing large load-bearing structures and bridging long spans. Crack formation may occur in the end zones of these elements due to tensile splitting, spalling and bursting actions. Investigation of these zones is typically done by means of analytical methods, strut and tie modelling, 2D linear or nonlinear analysis, or full 3D nonlinear analysis. Especially challenging in this last approach is the modelling of the force transfer from the strands to the surrounding concrete as it strongly influences the magnitude of the tensile stresses. This paper presents a 3D nonlinear analysis of the anchorage zone of a pretensioned girder, and a comparison with experimental results (mechanical strain measurements, embedded strain gauges). Material modelling, steel-concrete interaction properties, as well as convergence problems are addressed systematically. The comparison indicates that a good agreement is found, both for concrete and rebar strains, and that a friction coefficient of 0.7 can be adopted, although the results for values from 0.5 to 0.9 do not differ that much. The results demonstrate that a 3D nonlinear analysis provides an excellent insight in the behavior of the end zones of pretensioned girders which opens perspectives for an optimization of the end zone design based on this type of analysis.
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Ali, Sarmad Abdulsahab, and John P. Forth. "An experimental and analytical investigation of reinforced concrete beam-column joints strengthened with a range of CFRP schemes applied only to the beam." Advances in Structural Engineering 24, no. 12 (May 10, 2021): 2748–66. http://dx.doi.org/10.1177/13694332211007371.
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This paper investigates the experimental and analytical behaviour of beam-column joints that are subjected to a combination of torque, flexural and direct shear forces, where different Carbon Fibre Polymer (CFRP) strengthening wraps have been applied only to the beam. These wrapping schemes have previously been determined by the research community as an effective method of enhancing the torsional capacities of simply supported reinforced concrete beams. In this investigation, four 3/4-scale exterior beam-column joints were subjected to combined monotonic loading; three different beam wrapping schemes were employed to strengthen the beam region of the joint. The paper suggests a series of rational formulae, based on the space truss mechanism, which can be used to evaluate the joint shear demand of the beams wrapped in these various ways. Further, an iterative model, based on the average stress-strain method, has been introduced to predict joint strength. The proposed analytical approaches show good agreement with the experimental results. The experimental outcomes along with the adopted analytical methods reflect the consistent influence of the wrapping ratio, the interaction between the combined forces, the concrete strut capacity and the fibre orientation on the joint forces, the failure mode and the distortion levels. A large rise in the strut force resulting from shear stresses generated from this combination of forces is demonstrated and leads to a sudden-brittle failure. Likewise, increases in the beams’ main steel rebar strains are identified at the column face, again influenced by the load interactions and the wrapping systems used.
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Marcinczak, Dorota, and Tomasz Trapko. "DIC (Digital Image Correlation) method in the research of RC beams strengthened with PBO-FRCM materials." E3S Web of Conferences 97 (2019): 03008. http://dx.doi.org/10.1051/e3sconf/20199703008.
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The article presents tests of a reinforced concrete beam strengthened in a shear with PBO-FRCM composite materials. Measurement of the deformation of the composite was carried out using two methods - with strain gauges and the optical DIC method (Digital Image Correlation). The DIC method consists in taking a series of photographs of the tested object before and during loading. The surface of the tested element must have randomly spaced spots that are applied to the object before measurement. During the study, the cameras monitor the shifting of spots against each other, which in comparison to the reference image before loading gives information about strains and stresses of the tested element. Measurements of deformation of composite materials using strain gauges are difficult to clearly analyse, because the strain gauge is in a specific, limited place, which does not correspond to the work of the entire composite. In addition, the strain gauge tends to break at the place of crack. The article discusses this problem by presenting the results of deformation of PBO-FRCM composite meshes measured in two mentioned ways, their comparison and discussion of results.
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Marcińczak, Dorota. "Metoda DIC." BUILDER 259, no. 2 (February 1, 2019): 66–68. http://dx.doi.org/10.5604/01.3001.0013.3444.
Full textAbstract:
DIC (DIGITAL IMAGE CORRELATION) METHOD IN THE RESEARCH OF RC BEAMS STRENGTHENED WITH PBOFRCM MATERIALS. The article presents tests of a reinforced concrete beam strengthened in a shear with PBO-FRCM composite materials. Measurement of the deformation of the composite was carried out using two methods - with strain gauges and the optical DIC method (Digital Image Correlation). The DIC method consists in taking a series of photographs of the tested object before and during loading. The surface of the tested element must have randomly spaced spots that are applied to the object before measurement. During the study, the cameras monitor the shifting of spots against each other, which in comparison to the reference image before loading gives information about strains and stresses of the tested element. Measurements of deformation of composite materials using strain gauges are difficult to clearly analyze, because the strain gauge is in a specific, limited place, which does not correspond to the work of the entire composite. In addition, the strain gauge tends to break at the place of crack. The article discusses this problem by presenting the results of deformation of PBO-FRCM composite meshes measured in two mentioned ways, their comparison and discussion of results.
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Chang, Zhaoqun, Guohua Xing, Jiahua Zhao, and Jiao Huang. "Feasibility and flexural behavior of RC beams prestressed with straight unbonded aluminum alloy tendons." Advances in Structural Engineering, December 18, 2020, 136943322098166. http://dx.doi.org/10.1177/1369433220981662.
Full textAbstract:
This paper investigates the feasibility and flexural behavior of reinforced concrete beams internally prestressed with straight unbonded aluminum alloy tendons by testing five partially prestressed beams and one reference beam. For each beam specimen, load-deflection curves, failure modes and cracking behavior, the relationship between load and strains in steel and prestressing aluminum alloy tendons were examined and analyzed. In particular, the effects of effective prestress, combined reinforcement index (CRI), and partial prestressing ratio (PPR) on flexure of concrete beams were discussed. The test results indicated that the spacing and width of concrete cracks of prestressed beams containing the same amount of bonded longitudinal steel reinforcement decreased with the increase of effective prestress, and the combined reinforcement index governs flexural behavior of the prestressed beams. The flexural crack width and displacement ductility exhibited a reduction with the increase of CRI. In addition, an analytical model was established to calculate the flexural strength and corresponding deflection at midspan of the concrete beams internally prestressed with unbonded aluminum alloy tendons by suggesting a new simplified curvature distribution, which is more accordant with the original curvature distribution. The proposed model provides a relatively good estimation of the flexural capacity and midspan deflection of the prestressed beams.
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El-Basiouny, Ahmed M., Hamed S. Askar, and Mohamad E. El-Zoughiby. "Experimental and numerical study on the performance of externally prestressed reinforced high strength concrete beams with openings." SN Applied Sciences 3, no. 1 (January 2021). http://dx.doi.org/10.1007/s42452-020-04023-z.
Full textAbstract:
AbstractThis study investigates experimentally and numerically the performance of externally prestressed reinforced high strength concrete (HSC) beams with central openings. Seven externally prestressed rectangular HSC beams (six with central openings and a reference solid beam) are loaded incrementally to failure. All the beams have the same dimensions, reinforcement ratio and openings of variable size. Experimentally, the results show that, the appearance of the first flexural crack and the flexural stiffness reduction are largely governed by opening height. In contrast, the opening length greatly affects the presence of the first shear crack and the obtained values of strains in stirrups. Additionally, the opening length and height when combined can affect the strains in top- and bottom-bars and the failure load of the teste beams. Numerically, a three-dimensional nonlinear finite element analysis using ANSYS has been carried-out to analyze seventy (70) externally prestressed HSC beams with central openings. Based on the numerical results, a general formula to predict the ultimate moment is generated and verified. It can be used to predict the load carrying capacity of aging concrete elements with openings retrofitted using external prestressing techniques.