Articoli di riviste: "Concrete beams Testing"

1

Zainurrahman, Eko Darma e Sri Nuryati. "Carbon Fiber Reinforced Polymer Sebagai Perkuatan Lentur pada Balok Beton". BENTANG : Jurnal Teoritis dan Terapan Bidang Rekayasa Sipil 8, n. 1 (15 gennaio 2020): 20–28. http://dx.doi.org/10.33558/bentang.v8i1.1947.

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Concrete Beams can experience a sudden collapse when overload because of its brittle characteristic. The use of Carbon Fiber Reinforced Polymer (CFRP) on concrete beams externally as external confinement is predicted to improve concrete mechanics properties, increase the ductility and capacity of concrete, and the flexural strength of concrete beams. An experimental study on the reinforcement of concrete beams with Carbon Fiber Reinforced Polymer (CFRP) was carried out to estimate the effectiveness of CFRP on concrete structures as a concrete beam flexural reinforcement material. Two types of concrete beams are provided in this study to test the flexural strengthening effect of the externally bound CFRP composite. First type of concrete beam used for testing is a normal concrete beams, whereas the second tested beam, the CFRP was laminated by coating the beams with Fiber. The dimensions of both types are 15cm x15cm with a length of 55cm footing range. Testing result obtained the compressive strength was 23,29 MPa, flexural strength of normal and CRFP concretes were 33,41 Kg/cm2 and 48,07 Kg/cm2 respectively. It was concluded that the use of CRFP at the concrete beam increases flexural strength up to 44% with the ratio of 143 %.

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Muhtar, Amri Gunasti, Suhardi, Nursaid, Irawati, Ilanka Cahya Dewi, Moh Dasuki et al. "The Prediction of Stiffness of Bamboo-Reinforced Concrete Beams Using Experiment Data and Artificial Neural Networks (ANNs)". Crystals 10, n. 9 (27 agosto 2020): 757. http://dx.doi.org/10.3390/cryst10090757.

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Stiffness is the main parameter of the beam’s resistance to deformation. Based on advanced research, the stiffness of bamboo-reinforced concrete beams (BRC) tends to be lower than the stiffness of steel-reinforced concrete beams (SRC). However, the advantage of bamboo-reinforced concrete beams has enough good ductility according to the fundamental properties of bamboo, which have high tensile strength and high elastic properties. This study aims to predict and validate the stiffness of bamboo-reinforced concrete beams from the experimental results data using artificial neural networks (ANNs). The number of beam test specimens were 25 pieces with a size of 75 mm × 150 mm × 1100 mm. The testing method uses the four-point method with simple support. The results of the analysis showed the similarity between the stiffness of the beam’s experimental results with the artificial neural network (ANN) analysis results. The similarity rate of the two analyses is around 99% and the percentage of errors is not more than 1%, both for bamboo-reinforced concrete beams (BRC) and steel-reinforced concrete beams (SRC).

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Michalek, Peter, Jakub Kralovanec e Jan Bujnak. "Composite Steel and RPC Testing". Pollack Periodica 15, n. 3 (7 novembre 2020): 144–49. http://dx.doi.org/10.1556/606.2020.15.3.14.

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Reactive powder concretes are a set of ultrahigh-strength concrete reinforced with fibers. Their compressive strength is greater than 100 MPa. For assuring connection of steel beams and a concrete slab, steel stud connectors are used. The investigation of that kind of shear connection efficiency, in the case of this higher strength concrete deck using standard push-out test specimens has been executed. The experimental results are presented in the paper.

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Aparicio, Angel C., Gonzalo Ramos e Juan R. Casas. "Testing of externally prestressed concrete beams". Engineering Structures 24, n. 1 (gennaio 2002): 73–84. http://dx.doi.org/10.1016/s0141-0296(01)00062-1.

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Sunar Bükülmez, Pınar, e Oguz C. Celik. "Pre and post-fire mechanical properties of structural steel and concrete in steel-concrete composite cellular beams". MATEC Web of Conferences 282 (2019): 02054. http://dx.doi.org/10.1051/matecconf/201928202054.

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This paper presents an experimental investigation into possible variations of mechanical properties of structural steel and concrete in composite cellular beams exposed to ISO 834 fire and cooled down phases. Four full-scale fire tests were performed on protected and unprotected beams under assumed service loads. Tensile stress-strain behavior of steel coupons taken from the beams and compressive strengths of concrete cores taken from the reinforced concrete slabs are studied. Material coupon tests for steel are carried out as per TS EN ISO 6892-1. As for the concrete, compression tests were conducted. Coupon test results reveal that, after fire testing, a maximum reduction ratio of 65% in ultimate strain is obtained for the unprotected beam samples. This indicates that the reductions in the mechanical properties of steel in the protected beams are much less when compared to those of the unprotected beams. It is also found that the maximum increase in post-fire strength/pre-fire strength ratios for concrete is 11% for the unprotected beam, while a 20 % decrease is recorded for water based protected cellular beam. For the protected specimens, the RC slabs were exposed to higher temperatures, and the compressive strength of concrete after testing was lower than that of the unprotected beam slabs.

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Jiang, De Bao, e Xiao Jing Gu. "Test Research of Prestressed Concrete Beams with CFRP under Low Cyclic Loading". Advanced Materials Research 163-167 (dicembre 2010): 3848–52. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.3848.

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Through testing it is obtained that force and the damage that 1 root structure of prestressed concrete beams strengthened and 3 different layers CFRP reinforced stickup prestressed concrete beams under cyclic loading. This test results show that CFRP reinforcement effect of prestressed concrete beams is obvious, and at the same time the cracking of prestressed concrete beam has also has certain reinforcement effect; But the CFRP reinforcement effect is proportional to the number of layers.

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Newtson, Craig M., Gaur P. Johnson e Brian T. Enomoto. "Fundamental Frequency Testing of Reinforced Concrete Beams". Journal of Performance of Constructed Facilities 20, n. 2 (maggio 2006): 196–200. http://dx.doi.org/10.1061/(asce)0887-3828(2006)20:2(196).

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Motter, Christopher J., David C. Fields, John D. Hooper, Ron Klemencic e John W. Wallace. "Steel-Reinforced Concrete Coupling Beams. I: Testing". Journal of Structural Engineering 143, n. 3 (marzo 2017): 04016191. http://dx.doi.org/10.1061/(asce)st.1943-541x.0001670.

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Jesse, S. Margaret, e V. M. Shanthi. "Investigating the Load–Deflection of FRP Material in Concrete Beams Wrapped with CFRP in Universal Testing Machine (UTM)". Journal of Computational and Theoretical Nanoscience 15, n. 2 (1 febbraio 2018): 744–51. http://dx.doi.org/10.1166/jctn.2018.7155.

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Strengthening Reinforced Concrete (RC) beams using FRP laminate becomes one of the main strengthening techniques. Failure of these beams is usually controlled by the bond strength between the laminate and the concrete. This paper presents the results of experimental investigation on six reinforced concrete beams, with various types, which were tested under two-point loading. The aim of the work was to study the efficacy of Carbon Fiber Reinforced Polymer (CFRP) sheets in enhancing the beam strength and stiffness from shear failure or flexural failure. The strengthening and deflection of the beams were carried out with cyclic loading. Experimental data on ultimate load, deflection and failure modes of each of the beams were obtained. For the comparison of CFRP sheet with cement concrete and the retrofitted specimens absorbs more energy, the CFRP beams yield a good result.

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Buller, A. H., M. Oad e B. A. Memon. "Flexural Behavior of Reinforced RAC Beams Exposed to 1000°C Fire for 18 Hours". Engineering, Technology & Applied Science Research 9, n. 3 (8 giugno 2019): 4225–29. http://dx.doi.org/10.48084/etasr.2733.

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In order to meet the socio-economic demands around the globe, construction industry not only consumes concrete at a very fast pace but also yields huge amounts of construction and demolishing waste. The phenomenon gives rise to environmental issues due to production of concrete ingredients and due to dumping of the waste. Therefore, one of the solutions is the production of green concrete utilizing demolished waste. This research work studies the effect of prolonged fire (18 hours) on the flexural behavior of reinforced concrete–recycled aggregate beams. The beams were using 50% replacement of natural coarse aggregates with demolished concrete. The beam samples were cast as both normal and rich mix concrete and were cured for 28 days. After curing, the beams were exposed to fire at 1000°C in a purpose made oven, followed by testing in a universal load testing machine under central point load. The test results show that the proposed beams (cast with rich mix) exhibited about 22% reduction in flexural strength. The failure mode of the beams was observed as shear failure.

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Wang, Wei, Xin Zeng, Emery Niyonzima, Yue-Qing Gao, Qiu-Wei Yang e Shao-Qing Chen. "Size Effect of Shear Strength of Recycled Concrete Beam without Web Reinforcement: Testing and Explicit Finite Element Simulation". Sustainability 13, n. 8 (13 aprile 2021): 4294. http://dx.doi.org/10.3390/su13084294.

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Recycled concrete is a form of low-carbon concrete with great importance. The explicit finite element method is an economical and feasible method for analyzing static concrete structures, such as those made of recycled concrete. The shear strength of regular concrete beams has size effects. In this study, a group of physical tests on the size effect of the shear strength of recycled concrete beams without web reinforcement was carried out under the condition of a constant shear span ratio. The research results show that the shear strength of the test beam generally decreases with the increase in beam section height, and a regression formula of the shear strength was obtained, which can formulate this effect. The rationale and feasibility of the explicit finite element method solving the ultimate load of concrete structures (which can derive the shear strength) were briefly demonstrated, and an explicit finite element simulation of test beams was carried out. Results showed an obvious and phenomenologically regular size effect of the shear strength of recycled concrete beams without web reinforcement, which can be simulated by the explicit finite element method. This research aims to promote the study of low-carbon recycled concrete structures to a certain extent and encourage the application of economic explicit finite element methods for the static analysis of concrete structures.

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Yang, Yong Xin, Wei Zhang, Zeng Wei Guan e Wei Xie. "Numerical Analysis of RC Beams Strengthened with Pre-Stressed CFRP Sheets". Advanced Materials Research 255-260 (maggio 2011): 3101–5. http://dx.doi.org/10.4028/www.scientific.net/amr.255-260.3101.

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Through the finite element analysis software, fourteen strengthened beams are calculated in the condition of considering bonding-slip or not respectively. Comparing simulation results with test and theoretical calculation, We can draw the following conclusions: Testing reinforced concrete beams when there is no debonding, ANSYS simulation, theoretical calculations and experimental results agree well. Testing reinforced concrete beams when there is debonding. By considering the bond-slip calculation model calculation accuracy is higher. .Numerical results show that, prestressed CFRP with relative of prestressed girder of carbon fibre reinforced beam can significantly improve the cracking beam loading, and effectively improve the yield loads, but the ultimate load.

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Alnahhal, Wael, e Omar Aljidda. "Effect of Fiber Volume Fraction on Behavior of Concrete Beams Made with Recycled Concrete Aggregates". MATEC Web of Conferences 253 (2019): 02004. http://dx.doi.org/10.1051/matecconf/201925302004.

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This study investigates the effect of using different volume fractions of basalt macro fibers (BMF) on the flexural behavior of concrete beams made with 100% recycled concrete aggregates (RCA) experimentally. A total of 4 reinforced concrete (RC) beam specimens were flexural tested until failure. The parameter investigated included the BMF volume fraction (0%, 0.5%, 1%, and 1.5%). The testing results of the specimens were compared to control beam specimen made with no added fibers. The experimental results showed that adding BMF improves the flexural capacity of the tested beams.

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Das, P. C., J. S. Owen, B. J. Eccles, M. A. Woodings e B. S. Choo. "Role of Dynamic Testing in Assessment of Bridges". Transportation Research Record: Journal of the Transportation Research Board 1594, n. 1 (gennaio 1997): 115–24. http://dx.doi.org/10.3141/1594-12.

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Six reinforced concrete beams were loaded incrementally up to failure. After each increment the load was removed and measurements of the modal properties of the beams were made by impulse testing. The variation of the natural frequencies, frequency ratios, mode shapes, and the level of damage were investigated. It was found that on completion of the tests the natural frequencies of the beams had been reduced by an average of 25 percent in each mode. However, changes in mode shape were very small, and appreciable differences were only observed when the damage was highly localized. Modeling of the beam by using finite elements predicted trends that compared well with experimental observations. It is concluded that if dynamic testing were used in monitoring reinforced concrete structures, then the changes in frequency due to initial concrete cracking or yield of the reinforcement could be detected. More useful information associated with the spread and type of cracking through a structure may be detectable, although the level of the frequency changes is of the same order as those due to changes in ambient conditions.

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Protchenko, Kostiantyn. "Residual Fire Resistance Testing of Basalt- and Hybrid-FRP Reinforced Concrete Beams". Materials 15, n. 4 (17 febbraio 2022): 1509. http://dx.doi.org/10.3390/ma15041509.

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The fire resistance of fiber-reinforced polymer reinforced concrete (FRP-RC) elements depends on the temperature performance of the original concrete member, the fire scenario, and FRP reinforcement behavior. In this study, fire resistance tests are described, along with the characteristics obtained during and after applying elevated temperatures, simulating the effects of fire. The tested beams were reinforced with basalt (BFRP) bars and with a hybrid composite of carbon fibers and basalt fibers (HFRP) bars. Fire tests were performed on full-scale beams, in which the midsections of the beams were heated from below (tension zone) and from the sides for two hours, after which the beams were cooled and subjected to flexural testing. BFRP-RC beams failed before the heating time was completed; the best failure was associated with a BFRP reinforced beam that failed approximately 108 min after heating. Contrary to the BFRP-RC samples, HFRP-RC beams were capable of resisting exposure to elevated temperatures for two hours, but showed a 70% reduction in strength capacity when compared to non-heated reference beams. According to the author, the higher resistance of HFRP-RC beams was the result of the thermal expansion coefficient of carbon fibers employed in HFRP, which “prestresses” the beams and enables smaller deflections. The preliminary findings of this study can increase the feasibility of using FRP materials for engineering purposes.

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Elbasha, Nuri Mohamed. "Reinforced HSC Beams". Key Engineering Materials 629-630 (ottobre 2014): 544–50. http://dx.doi.org/10.4028/www.scientific.net/kem.629-630.544.

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The primary long and short term advantages of high strength concrete are, low creep and shrinkage, higher stiffness, higher elastic modulus, higher tensile strength, higher durability (resistance to chemical attacks) and higher shear resistance. In addition, high strength concrete reduces the size of the member, which in turn reduces the form size, concrete volume, construction time, labor costs and dead load. Reducing the dead load reduces the number and size of the beams, columns and foundations. Thus there is a positive impact on reduction of maintenance and repair costs and an increase in rentable space. Other, yet to be discovered advantages may also exist. High strength concrete has definite advantages over normal strength concrete. The ductility of over reinforced HSC beams is enhanced through the application of helical reinforcement located in the compression region. The pitch of helix is an important parameter controlling the level of strength and ductility enhancement. This paper presents an experimental investigation of the effect of helices on the behavior of over reinforced high strength concrete beams through testing ten helically confined full scale beams. The helix pitches were 25, 50, 75, 100 and 160 mm. Beams’ cross section was 200×300 mm, and with a length of 4 m and a clear span of 3.6 m subjected to four point loading. The main results indicate that helix effectiveness is negligible when the helical pitch is 160 mm (helix diameter). The experimental program in this study proved that the HSC, HSS and helical confinement construct a reinforced concrete beam. This beam has the ability to resist weathering action and chemical attack while maintaining its desired engineering properties. In near future Reinforced High Strength Concrete Beam with Helical Confinement will be considered as a durable and sustainable Reinforced Concrete Beam.

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MORDOVSKY, Sergey S., Nikolay A. ILYIN, Denis A. PANFILOV, Valeriya N. TALANOVA e Yana A. BUZOVSKAYA. "METHOD OF MODELING A REINFORCED CONCRETE BEAM WITH DOUBLE REINFORCEMENT FOR STRENGTH, DEFORMATION AND FIRE RESISTANCE". Urban construction and architecture 9, n. 1 (15 marzo 2019): 4–9. http://dx.doi.org/10.17673/vestnik.2019.01.1.

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The article presents a new technical solution, which relates to the field of construction, in particular, to the testing of bending reinforced concrete elements - building beams for strength, deformation and fire resistance on a scale model. The new method of solution implies an increase in the information content, visual clarity and depth of experimental studies of reinforced concrete beams as a result of using the cost-effective way of designing geometric and forceful similarity to the scale model of reinforced concrete beams for strength, deformation and fire resistance. The proposed method allows us to estimate the limiting states of a reinforced concrete beam by strength, deformation and fire resistance; develop an analytical model for calculating the actual fire resistance; save on labor costs in the manufacture of large scale model of full scale design for its testing.

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Sagaydak, A. I., V. V. Bardakov, S. V. Elizarov e V. I. Ivanov. "STANDARDS FOR THE TECHNICAL STATE TESTING OF REINFORCED CONCRETE STRUCTURES BY MEANS OF ACOUSTIC EMISSION METHOD". Kontrol'. Diagnostika, n. 264 (giugno 2020): 32–39. http://dx.doi.org/10.14489/td.2020.06.pp.032-039.

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The review of 3 standards in the field of concrete and reinforced concrete acoustic emission testing, developed and issued by International Organization for Standardization in 2019 is provided in the article. The first standard describes the process of acoustic emission signals measuring in concrete and reinforced concrete. The second standard describes test method for damage qualification of reinforced concrete beams. This standard allows dividing the damage degree of reinforced concrete beams into 3 groups: minor, intermediate, heavy. The third standard describes method for active cracks classification in concrete. This standard allows dividing growing cracks into 2 types: tensile cracks and other crack types (shear). Experimental studies on the correctness assessment of these standards by reinforced concrete beams three-point bending testing with incremental cyclic load were carried out. In total 5 RC beams of heavy concrete with different concrete strength and reinforcing type were tested. Based on the testing results the correctness of the criteria and methods presented in the standards was confirmed.

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Sagaydak, A. I., V. V. Bardakov, S. V. Elizarov e V. I. Ivanov. "STANDARDS FOR THE TECHNICAL STATE TESTING OF REINFORCED CONCRETE STRUCTURES BY MEANS OF ACOUSTIC EMISSION METHOD". Kontrol'. Diagnostika, n. 264 (giugno 2020): 32–39. http://dx.doi.org/10.14489/td.2020.06.pp.032-039.

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Abstract (sommario):

The review of 3 standards in the field of concrete and reinforced concrete acoustic emission testing, developed and issued by International Organization for Standardization in 2019 is provided in the article. The first standard describes the process of acoustic emission signals measuring in concrete and reinforced concrete. The second standard describes test method for damage qualification of reinforced concrete beams. This standard allows dividing the damage degree of reinforced concrete beams into 3 groups: minor, intermediate, heavy. The third standard describes method for active cracks classification in concrete. This standard allows dividing growing cracks into 2 types: tensile cracks and other crack types (shear). Experimental studies on the correctness assessment of these standards by reinforced concrete beams three-point bending testing with incremental cyclic load were carried out. In total 5 RC beams of heavy concrete with different concrete strength and reinforcing type were tested. Based on the testing results the correctness of the criteria and methods presented in the standards was confirmed.

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Madjlessi, Noosha, Demitrios M. Cotsovos e Mojtaba Moatamedi. "Drop‐weight testing of slender reinforced concrete beams". Structural Concrete 22, n. 4 (5 maggio 2021): 2070–88. http://dx.doi.org/10.1002/suco.202000395.

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Lindberg, Ralf, Nina Lindberg, Anssi Laaksonen e Ilkka Vilonen. "Testing of Full Scale Pre-Stressed Concrete Beams". IABSE Symposium Report 100, n. 3 (1 giugno 2013): 170–76. http://dx.doi.org/10.2749/222137813807018881.

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Gong, Bingnian, e Bahram M. Shahrooz. "Concrete-Steel Composite Coupling Beams. I: Component Testing". Journal of Structural Engineering 127, n. 6 (giugno 2001): 625–31. http://dx.doi.org/10.1061/(asce)0733-9445(2001)127:6(625).

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Abdulazeez Abdulridha, Aseel, Sura Amoori Abbas, Lubna Salim Danha e Zainab Hassan Shaker. "Flexural Behavior of the Layered Beams Containing Reactive Powder Concrete and Self-Compacting Concrete". Journal of Engineering and Technological Sciences 54, n. 3 (20 maggio 2022): 220302. http://dx.doi.org/10.5614/j.eng.technol.sci.2022.54.3.2.

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Reactive powder concrete (RPC) possesses superior structural and mechanical characteristics. Despite these excellent properties, the main drawback of RPC is that it is a very costly material. This study included an experimental program for studying the flexural behavior of hybrid beams containing RPC together with self-compacting concrete (SCC) in the same section. Five specimens with dimensions of 100 x 150 x 1000 mm were investigated. The first crack load, ultimate load, maximum deflection, load-deflection response, and crack pattern were investigated. The experimental program included testing five reinforced concrete beams with four-point loading. The specimens were cast as follows: full depth of self-compacting concrete; full depth of reactive powder concrete; half of the section depth of RPC (tension zone); quarter of the section depth of RPC (tension zone); and half of the section depth of RPC (compression zone). The experimental results of the hybrid beams showed that using RPC in the tension zone of the beam significantly improved the performance of the hybrid beams when compared with the SCC beam. The improvement rate increased with the RPC layer thickness in the tension zone. Using RPC in the compression zone together with SCC did not produce a significant improvement in the performance of the hybrid beams.

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Braimah, Abass, Mark F. Green e T. Ivan Campbell. "Fatigue behaviour of concrete beams post-tensioned with unbonded carbon fibre reinforced polymer tendons". Canadian Journal of Civil Engineering 33, n. 9 (1 settembre 2006): 1140–55. http://dx.doi.org/10.1139/l06-063.

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Much research has been conducted in the past decade to evaluate the suitability of fibre reinforced polymer (FRP) reinforcement in concrete structures. Most of the research has concentrated on the short-term performance of FRP prestressed and reinforced concrete beams. Only a limited amount of research has considered the fatigue behaviour of FRP prestressed beams. This paper presents an experimental research program designed to examine the fatigue behaviour of unbonded carbon fibre reinforced polymer (CFRP) post-tensioned concrete beams. The fatigue test program consisted of five large-scale (4.0 m span) concrete T-beams. Three of the beams were post-tensioned with CFRP tendons, and the remaining two beams were post-tensioned with steel prestressing strands. The fatigue load limits were chosen to produce an additional stress range of about 100 MPa in the lower prestressing reinforcement. During fatigue testing, some of the prestressing strands fractured at the anchor location. In the steel post-tensioned beams, fracture of wires in the seven-wire prestressing strands did not result in total failure of the steel post-tensioned beams, as the unbroken wires continued to carry prestress force. In the CFRP post-tensioned beams, however, fracture led to splintering of the tendon between the anchors and total loss of prestress force. In general, the CFRP post-tensioned beams performed satisfactorily in fatigue, in comparison with the steel post-tensioned beams, as long as premature failure of the tendons near the anchor location was prevented.Key words: fibre reinforced polymer (FRP), anchorage, tendon, fatigue, post-tension, concrete, beam, dynamic, testing.

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Omeman, Z., M. Nehdi e H. El-Chabib. "Experimental study on shear behavior of carbon-fiber-reinforced polymer reinforced concrete short beams without web reinforcement". Canadian Journal of Civil Engineering 35, n. 1 (gennaio 2008): 1–10. http://dx.doi.org/10.1139/l07-080.

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Recent literature emphasized the scarcity of information on the shear behavior of fiber-reinforced polymer (FRP) reinforced concrete short beams and the need to develop sufficient experimental data in this area. The present study responds to this need by conducting shear force testing on eight concrete short beams reinforced with carbon-fiber-reinforced polymer (CFRP) and four control concrete beams reinforced with steel. To ensure a shear failure, all tested beams were reinforced with only bottom longitudinal reinforcement and no web reinforcement was provided. The crack pattern, reinforcement strain, mode of failure, and shear strength and deflection of tested beams were studied. The influence of the shear span to effective depth ratio, a/d, beam effective depth, d, longitudinal reinforcement ratio, ρ, and concrete compressive strength, f ′c on the shear behavior of CFRP-reinforced concrete short beams was examined. It was observed that the experimental parameters investigated had a significant effect on the shear strength and deflection of tested beams. It was also found that the strut-and-tie method more accurately predicts the shear strength of steel-reinforced concrete short beams than it does for similar CFRP-reinforced beams and, thus, needs to be modified to be applicable for reinforced concrete beams with FRP reinforcement.

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Liu, Tongxu, e Jean-Philippe Charron. "Shear strengthening of concrete T-beams with lateral layers of UHPC". MATEC Web of Conferences 364 (2022): 04016. http://dx.doi.org/10.1051/matecconf/202236404016.

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Concrete T-beams are commonly used in building slab systems and bridge decks. They may require strengthening in shear when they are deteriorated or when loading requirements increased. This research project studied the shear behaviour of concrete T-beams using cast-in-place Ultra High-Performance Concrete (UHPC) layers as a lateral strengthening method avoiding beam depth modification. Three UHPC strengthened beams together with one reference reinforced concrete beam were tested in monotonic three-point bending. Parameters investigated include the thickness of UHPC layers and the presence of steel anchors at the UHPC-concrete interface. A digital image correlation (DIC) technique was used to investigate the strain distribution of T-beams during the testing. Strain distribution, failure modes and strengthening effects provided by the UHPC lateral strengthening were analyzed. Results show that UHPC strengthening can substantially improve the stiffness and shear capacity of concrete T-beams, 25 and 50 mm lateral layers increased by 102% and 113% the T-beam shear capacity, respectively. Typical bending-shear behaviour were observed on each strengthened beam with UHPC layers. A final shear failure was observed in the T-beam with 25 mm UHPC layers and 50 mm UHPC layers without anchors, while a combination of shear and bending failure was noted in the T-beam with 50 mm UHPC layers and steel anchors. The steel anchors at the UHPC-concrete interface can further increase the ultimate shear capacity and beam stiffness, but at a limited extent. Therefore, experimental results confirmed that cast-in-place UHPC lateral layers are an effective way to strengthen existing concrete T-beams with inadequate shear capacity

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Yang, Qiuwei, Xi Peng e Yun Sun. "Shear Capacity Evaluation of the Recycled Concrete Beam". Materials 15, n. 10 (21 maggio 2022): 3693. http://dx.doi.org/10.3390/ma15103693.

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Compared with traditional concrete beams, recycled concrete beams are more prone to cracking and shear failure. Generally, shear failure is a brittle failure and its failure consequences are often very serious. Thus, the shear capacity is an important parameter in the design and testing for beam structures. In this work, the computation method and size effect on shear capacity of recycled concrete beams without stirrups are studied. Four recycled aggregate concrete beams with different sizes are tested by the bending experiment to obtain their ultimate shear capacities. By keeping the shear span ratio unchanged, the variation laws of mechanical parameters such as cracking load, ultimate shear capacity and shear strength for these beam specimens are studied. From the experiment results, it is concluded that the shear capacities of beams with lengths of 740 mm, 1010 mm, 1280 mm and 1550 mm are 86.3 kN, 106 kN, 124.7 kN and 177.7 kN, respectively. The corresponding shear strengths are 6.84 MPa, 5.59 MPa, 4.9 MPa, and 5.56 MPa, respectively. Nine computation formulas of shear capacity in the literature, such as ACI 318M-14, EN 1992-1-1, GB50010-2010 and so on, are used to calculate the shear capacities of these recycled concrete beams for comparison. The comparative study shows that it is feasible to consider the size effect in the computation of shear capacity for the recycled concrete beam.

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Tamil Selvi, M., e T. S. Thandavamoorthy. "Load-Deflection Characteristics Of Steel, Polypropylene And Hybrid Fiber Reinforced Concrete Beams". Archives of Civil Engineering 61, n. 1 (1 marzo 2015): 59–72. http://dx.doi.org/10.1515/ace-2015-0004.

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AbstractConcrete is the most widely used construction material because of its specialty of being cast into any desired shape. The main requirements of earthquake resistant structures are good ductility and energy absorption capacity. Fiber reinforced concrete possesses high flexural and tensile strength, improved ductility, and high energy absorption over the conventional concrete in sustaining dynamic loads. The aim of this paper is to compare the properties of concrete beams in which three types of fibers are added individually. Steel fibers, polypropylene fibers and hybrid fibers were added to concrete in the weight ratio of four percentages in the preparation of four beam specimens. The fourth specimen did not contain fibers and acted as a control specimen. The dimensions of the beam specimens were 150 mm × 150 mm × 700 mm. The reinforced concrete beams of M30 grade concrete were prepared for casting and testing. Various parameters such as load carrying capacity, stiffness degradation, ductility characteristics and energy absorption capacity of FRC beams were compared with that of RC beams. The companion specimens were cast and tested to study strength properties and then the results were compared. All the beams were tested under three point bending under Universal Testing Machine (UTM). The results were evaluated with respect to modulus of elasticity, first crack load, ultimate load, and ultimate deflection. The test result shows that use of hybrid fiber improves the flexural performance of the reinforced concrete beams. The flexural behavior and stiffness of the tested beams were calculated, and compared with respect to their load carrying capacities. Comparison was also made with theoretical calculations in order to determine the load-deflection curves of the tested beams. Results of the experimental programme were compared with theoretical predictions. Based on the results of the experimental programme, it can be concluded that the addition of steel, polypropylene and hybrid fibers by 4% by weight of cement (but 2.14 % by volume of cement) had the best effect on the stiffness and energy absorption capacity of the beams.

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Chen, Li Hua, Fei Xiao e Qi Liang Jin. "Research on Key Issues in Design of Outer-Plated Steel-Concrete Continuous Composite Beams". Applied Mechanics and Materials 166-169 (maggio 2012): 414–19. http://dx.doi.org/10.4028/www.scientific.net/amm.166-169.414.

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Based on the theoretical analysis and testing results, some key issues in design of outer-plated steel-concrete continuous composite beams are discussed. The influence of the form of steel beam upper flange on the behavior of composite beam is analyzed. The requirements about longitudinal reinforcement strength in the concrete flange of the negative moment region are given. It is suggested that the moment-shear interaction should be neglected when calculating the flexural capacity of outer-plated steel-concrete composite beams under negative bending moment. The behavior of longitudinal shear resistance at the interface between the concrete flange and web of composite beam is studied, and the related calculating formula is put forward based on the structural features of the composite beam.

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30

Lei, Guang Yu, Chang Hong Wu e Shi Ming Li. "Testing Research for Deformation and Rigidity of Lightweight Aggregate Reinforced Concrete Beams under Fatigue Loading". Applied Mechanics and Materials 204-208 (ottobre 2012): 3123–27. http://dx.doi.org/10.4028/www.scientific.net/amm.204-208.3123.

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Through the experiment of eight lightweight aggregate reinforced concrete beams under static loading and fatigue loading with constant amplitudes, the deformation rule under fatigue loading was analysed, the rigidity calculation means and formulations of lightweight aggregate reinforced concrete beam under fatigue loading were also discussed.

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31

Raju, Sumathy, Jagadheeswari Rathinam, Brindha Dharmar, Sasi Rekha, Siva Avudaiappan, Mugahed Amran, Kseniia Iurevna Usanova, Roman Fediuk, Pablo Guindos e Ramkumar Velayutham Ramamoorthy. "Cyclically Loaded Copper Slag Admixed Reinforced Concrete Beams with Cement Partially Replaced with Fly Ash". Materials 15, n. 9 (25 aprile 2022): 3101. http://dx.doi.org/10.3390/ma15093101.

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Generally, the concrete with higher strength appears to produce brittle failure more easily. However, the use of mineral admixture can help in enhancing the ductility, energy dissipation, and seismic energy in the designed concrete. This paper presents energy absorption capacity, stiffness degradation, and ductility of the copper slag (CS) admixed reinforced concrete with fly ash (FA) beams subjected to forward cyclic load. The forward cyclic load was applied with the help of servo-hydraulic universal testing machines with 250 kN capacity. Twenty-four beams with a size of 100 mm × 150 mm × 1700 mm made with CS replaced for natural sand from 0% to 100% at an increment of 20%, and FA was replaced for cement from 0% to 30% with an increment of 10% were cast. Beams are designed for the grade of M30 concrete. Based on the preliminary investigation results, compressive strength of the concrete greatly increased when adding these two materials in the concrete. Normally, Grade of concrete can change the behaviour of the beam from a brittle manner to be more ductile manner. So, in this work, flexural behaviour of RC beams are studied with varying compressive strength of concrete. Experimental results showed that the RC beam made with 20% FA and 80% CS (FA20CS80) possesses higher ultimate load-carrying capacity than the control concrete beam. It withstands up to 18 cycles of loading with an ultimate deflection of 60 mm. The CS and FA admixed reinforced concrete composite beams have excellent ultimate load carrying capacity, stiffness, energy absorption capacity, and ductility indices compared to the control concrete beam.

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32

Raju, Sumathy, Jagadheeswari Rathinam, Brindha Dharmar, Sasi Rekha, Siva Avudaiappan, Mugahed Amran, Kseniia Iurevna Usanova, Roman Fediuk, Pablo Guindos e Ramkumar Velayutham Ramamoorthy. "Cyclically Loaded Copper Slag Admixed Reinforced Concrete Beams with Cement Partially Replaced with Fly Ash". Materials 15, n. 9 (25 aprile 2022): 3101. http://dx.doi.org/10.3390/ma15093101.

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Abstract (sommario):

Generally, the concrete with higher strength appears to produce brittle failure more easily. However, the use of mineral admixture can help in enhancing the ductility, energy dissipation, and seismic energy in the designed concrete. This paper presents energy absorption capacity, stiffness degradation, and ductility of the copper slag (CS) admixed reinforced concrete with fly ash (FA) beams subjected to forward cyclic load. The forward cyclic load was applied with the help of servo-hydraulic universal testing machines with 250 kN capacity. Twenty-four beams with a size of 100 mm × 150 mm × 1700 mm made with CS replaced for natural sand from 0% to 100% at an increment of 20%, and FA was replaced for cement from 0% to 30% with an increment of 10% were cast. Beams are designed for the grade of M30 concrete. Based on the preliminary investigation results, compressive strength of the concrete greatly increased when adding these two materials in the concrete. Normally, Grade of concrete can change the behaviour of the beam from a brittle manner to be more ductile manner. So, in this work, flexural behaviour of RC beams are studied with varying compressive strength of concrete. Experimental results showed that the RC beam made with 20% FA and 80% CS (FA20CS80) possesses higher ultimate load-carrying capacity than the control concrete beam. It withstands up to 18 cycles of loading with an ultimate deflection of 60 mm. The CS and FA admixed reinforced concrete composite beams have excellent ultimate load carrying capacity, stiffness, energy absorption capacity, and ductility indices compared to the control concrete beam.

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33

Tampubolon, Sudarno P. "Analisa Perilaku Pushover pada Pengujian Balok Beton Bertulang". Bentang : Jurnal Teoritis dan Terapan Bidang Rekayasa Sipil 10, n. 1 (7 gennaio 2022): 77–88. http://dx.doi.org/10.33558/bentang.v10i1.3078.

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Abstract (sommario):

Beams are part of the building structure that is important to consider when designing the structure. Some failures that occur in beams due to beam reinforcement are not installed such as planning/ design procedures, this problem can cause structural failure. Knowing the behavior of the beam structure due to the given load can help predict the strength of the structural beam and the comfort of the planned structure. To determine and predict the strength and comfort of the reinforced concrete beam structure due to the received load, experimental and simulation tests are carried out. VecTor2 simulation is used to predict shear, crack, and displacement forces in reinforced concrete beams when displacement loads are applied. The bond stress-slip effect (0.139) has a good effect on the strength and hysterical response of reinforced concrete beams. From the results of pushover testing and simulations, it is obtained that the ratio for load capacity ranges from 1.00-1.095. In addition, the installation of 135˚ hooks on stirrups shows that the crack behavior that occurs forms an angle of 45˚, this indicates that the bond between concrete and reinforcement is going well, this can be seen from the analogous behavior principle of reinforced concrete beams.

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34

Yi, Wei Jian, e Yan Mei Lv. "Experimental Study on Shear Failure of High-Strength Concrete Beams with High-Strength Stirrups". Key Engineering Materials 400-402 (ottobre 2008): 857–63. http://dx.doi.org/10.4028/www.scientific.net/kem.400-402.857.

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Abstract (sommario):

19 RC beams with shear span-to-depth equal to 3 were tested under a stiff testing facility, and complete load-deflection curves including the post-peak branch were obtained. Based on the test results the effects of concrete strength, stirrups strength, inclined stirrup angle, the amount of longitudinal reinforcement on failure mode, shear ductility index and shear capacity were analyzed. The test results were compared with the shear design approaches of Chinese Code and American Code. The results indicate that the shear failure of beam with appropriate web reinforcement has finite ductility. High-strength concrete beams with high-strength stirrups can increase not only the shear capacity, but also the shear ductility. The shear capacity of beams with high-strength concrete and stirrup can be designed with Chinese Code, but shear capacity of high-strength concrete beams without stirrups, or with the smaller amount of longitudinal reinforcement, and normal strength concrete beams with high-strength stirrups may be over-estimated by the Code.

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35

Smarzewski, Piotr, Justyna Poręba e Agata Rentflejsz. "Experimental testing of high performance fibre reinforced concrete deep beams". Budownictwo i Architektura 10, n. 1 (11 giugno 2012): 015–26. http://dx.doi.org/10.35784/bud-arch.2227.

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Abstract (sommario):

The article presents the results of testing reinforced deep beams made of high performance concrete and fibre-concrete in the scheme of centrally placed load. The test was conducted for three deep beam elements of the of the main reinforcement bars in the form of lower, upper, horizontal and vertical stirrups in support areas of alternative reinforcement grids or steel and polypropylene fibers between the points of support elements. Analysis of results was based on the maps of major strains, the relations of force in the function of time and the relations of vertical displacements of the length of the members in the horizontal section.

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36

Zhou, Yunlong, Zhinian Yang, Zhiguo You, Xingguo Wang, Kaijiang Chen, Boyu Guo e Kai Wu. "Experimental Study on Fire Resistance of Concrete Beams Made with Iron Tailings Sand". Buildings 12, n. 11 (28 ottobre 2022): 1816. http://dx.doi.org/10.3390/buildings12111816.

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Abstract (sommario):

In order to measure the effect of iron tailings sand replacing natural sand on the fire resistance of concrete beams, five full-scale iron tailings sand concrete (ITSC) beams and two natural sand concrete (NSC) beams were conducted to fire testing under dead load and rising temperature conditions. The section temperature field, mid-span displacement, failure form, and fire resistance limit of ITSC beams under fire were analyzed. The main influence factors included different ISTC strengths (C30 and C40) and constraints. The analysis results were compared with those of NSC beams. The results show that the complete replacement of natural sand with iron tailings sand had little influence on the temperature field of concrete and reinforcement in simply supported beams and continuous beams under fire. The fire endurance of the ITSC simply supported beams was similar to that of NSC simply supported beams. When exposed to fire, the higher the strength of the ITSC, the better the fire resistance of the beam. The fire endurance of continuous beams was higher than that of simply supported beams. On the basis of the analysis of the fire resistance performance, it was found that iron tailings sand can replace natural sand to formulate concrete beams.

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37

M S, Latha, Revanasiddappa M e Naveen Kumar B M. "Influence of stirrup spacing on shear resistance and deformation of reinforced concrete beams". International Journal of Engineering & Technology 7, n. 1 (3 febbraio 2018): 126. http://dx.doi.org/10.14419/ijet.v7i1.9013.

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Abstract (sommario):

An experimental investigation was carried out to study shear carrying capacity and ultimate flexural moment of reinforced cement concrete beam. Two series of simply supported beams were prepared by varying diameter and spacing of shear and flexural reinforcement. Beams of cross section 230 mm X 300 mm and length of 2000 mm. During testing, maximum load, first crack load, deflection of beams were recorded. Test results indicated that decreasing shear spacing and decreasing its diameter resulted in decrease in deflection of beam and increase in bending moment and shear force of beam.

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38

Novak, Josef, e Alena Kohoutkova. "Optimization of Pretensioned Steel Fiber Reinforced Concrete Beam". Advanced Materials Research 1106 (giugno 2015): 94–97. http://dx.doi.org/10.4028/www.scientific.net/amr.1106.94.

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Pretensioned concrete beams are used as a main load bearing member for composite bridges with a span to 30 m. The advantage of longitudinal prefabrication technology of beams for small span bridges is quick installation, savings of straight supporting scaffolding of centers and formwork. The amount of labour with formwork, reinforcement and concrete including work with scaffolding of centers on site is reduced at a minimum. During searching applications of steel fiber reinforced concrete (SFRC) suitable for this kind of structure a pretensioned concrete beam suitable for a bridge bay with a span from 12 to 15 m has been chosen for an investigation. Three types of beam were manufactured for experimental tests. The beams were supposed to be a part of a bridge bay with a composite slab. These pretensioned beams were made of SFRC. In case of the experimental tests, a cast-in place concrete cover from plain concrete was casted on the top of the beams. The cast-in place concrete cover simulated a top composite slab. The bearing capacity of the beams with the cast-in place concrete cover was tested until their destruction. The tested beams showed higher bearing capacity than it was determined by a theoretical calculation. The beams also demonstrated high safety against collapse during structure overloading. The process of the experimental testing was also simulated on a numerical nonlinear model and then the results were compared. The result comparison of the both types of tests did not show any significant irregularities.

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Mohammed, Ihtesham Hussain, Ahmed Majid Salim Al Aamri, Shakila Javed e Yahya Ubaid Al Shamsi. "A Comparative Investigation on Normal and High Strength Concrete Beams under Torsion". Materials Science Forum 1048 (4 gennaio 2022): 359–65. http://dx.doi.org/10.4028/www.scientific.net/msf.1048.359.

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In this study, an experimental investigation was done to study the behaviour of Normal Strength Concrete (NSC) and High Strength Concrete (HSC) Plain beams under torsion with the concrete mix of M40 and M100. No mineral admixtures are used to obtain the required strength of concrete. Eight NSC beams and eight HSC beams whose width was varying with 75 mm, 100 mm, and 150 mm; depth varying as 75 mm, 100 mm, 150 mm and 200 mm; and span of the beams varying 600 mm, 800 mm and 1200 mm were casted and cured to stud the effect of torsion. The principle aim of this study was to understand the torsional behaviour of the NSC and HSC beams for rotation, cracking, size effect and torsional strength. A standard torsional loading method was used for conducting the testing of beams. The results obtained were compared with different theories and code equations. It was observed that the torsional strength of the beam increases with the increase in strength of concrete. HSC beams have higher torsional strength than the NSC beams which has the same amount of reinforcement.

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40

Abdulhameed, Ali Adel, e AbdulMuttalib Issa Said. "Behaviour of Segmental Concrete Beams Reinforced by Pultruded CFRP Plates: An Experimental Study". Journal of Engineering 25, n. 8 (31 luglio 2019): 62–79. http://dx.doi.org/10.31026/j.eng.2019.08.05.

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The research aims to develop an innovative technique for segmental beam fabrication using plain concrete blocks and externally bonded Carbon Fiber Reinforced Polymers Laminates (CFRP) as a main flexural reinforcement. Six beams designed and tested under two-point loadings. Several parameters included in the fabrication of segmental beam were studied such as; bonding length of carbon fiber reinforced polymers, the surface-to-surface condition of concrete segments, interface condition of the bonding surface and thickness of epoxy resin layers. Test results of the segmental beams specimens compared with that gained from testing reinforced concrete beam have similar dimensions for validations. The results display the effectiveness of the developed fabrication method of segmental beams. The modified design procedure for externally bonded carbon fiber reinforced polymers ACI 440.2R-17 was developed for designing segmental beams. The experimental test values also compared with design values, and it was 93.3% and 105.8% of the design values, which indicates the effectiveness of the developed procedure.

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Abdulhameed, Ali A., e AbdulMuttalib Issa Said. "Behaviour of Segmental Concrete Beams Reinforced by Pultruded CFRP Plates: an Experimental Study". Journal of Engineering 25, n. 8 (5 agosto 2019): 62–79. http://dx.doi.org/10.31026/j.eng.2019.08.11.

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Abstract (sommario):

Research aims to develop a novel technique for segmental beam fabrication using plain concrete blocks and externally bonded Carbon Fiber Reinforced Polymers Laminates (CFRP) as a main flexural reinforcement. Six beams designed an experimentally tested under two-point loadings. Several parameters included in the fabrication of segmental beam studied such as; bonding length of carbon fiber reinforced polymers, the surface-to-surface condition of concrete segments, interface condition of the bonding surface, and thickness of epoxy resin layers. Test results of the segmental beams specimens compared with that gained from testing reinforced concrete beam have similar dimensions for validations. The results show the effectiveness of the developed fabrication method of segmental beams. The modified design procedure for externally bonded carbon fiber reinforced polymers ACI 440.2R-17 developed for designing segmental beams. The experimental test values also compared with design values and it was 93.3% and 105.8% of the design values which indicates the effectiveness of the developed procedure.

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42

Liu, Xinhua, Jianren Zhang, Zihan Cheng e Meng Ye. "Experimental and Numerical Studies on the Negative Flexural Behavior of Steel-UHPC Composite Beams". Advances in Civil Engineering 2021 (31 gennaio 2021): 1–15. http://dx.doi.org/10.1155/2021/8828175.

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Abstract (sommario):

The cracking of concrete in the negative moment region for a composite beam subjected to a negative bending moment reduces the beam’s strength and stiffness. To improve the cracking performance of composite beams, this paper presents an experimental investigation on applying ultrahigh-performance concrete (UHPC) instead of conventional concrete. Three steel-UHPC composite beams with different forms of joints were designed and tested through a unique rotation angle loading method using a spring displacement control testing setup. The crack distribution, rotation versus crack width, load versus spring displacement, and strains in the UHPC slab and steel girders were measured and studied. Nonlinear finite element analysis using ABAQUS based on the damaged plasticity model of concrete was carried out for comparison with the test results. The experimental and numerical results showed that the use of a UHPC slab can enhance the cracking performance of composite beams. Considering the convenience of construction, a reasonable joint form was suggested, and the appropriate UHPC longitudinal laying length in the negative moment region was proposed to be 0.1 L. Furthermore, a simplified formula for calculating the UHPC crack width was developed based on bond-slip theory.

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43

Saleh, Fadillawaty. "Determination of Damage Location in Reinforced Concrete Beams Using Mode Shape Curvature Square (MSCS) Method". Applied Mechanics and Materials 845 (luglio 2016): 140–47. http://dx.doi.org/10.4028/www.scientific.net/amm.845.140.

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This paper presents a numerical algorithm technique to detect cracks propagated in concrete beams based on the frequency response curve of the beam determined from vibration testing. Impact tests on simply supported reinforced concrete beams were conducted to measure vibration on the beam. The ICATS software was carried out to capture the Frequency Response Functions (FRFs) data at each load step. Utilizing the FRFs data, a numerical algorithm based on finite different methods was performed to compute the different FRFs between undamage and damage beams based on the mode shape curvature square (MSCS) method. The numerical damage location was defined by subtracting the MSCS undamage to damage of beams. Therefore, the accurate damage location was identified by comparing the numerical and observed experimental results.

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44

Buller, A. H., M. Oad e B. A. Memon. "Flexural Strength of Reinforced Concrete RAC Beams Exposed to 6-hour Fire – Part 2: Rich Mix". Engineering, Technology & Applied Science Research 9, n. 1 (16 febbraio 2019): 3814–17. http://dx.doi.org/10.48084/etasr.2494.

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In this research work, experimental investigation on flexural strength of reinforced concrete beams exposed to fire for 6-hours at the temperature of 1000˚C is presented. The beams are made with 50% replacement of natural coarse aggregates with recyclable concrete aggregates. A total of 12 reinforced concrete beams using 1:1.5:3 mix (rich mix) and 0.54 water-cement ratio were cast. The beams were prepared in two groups. Group 1 beams were prepared with 50% recyclable aggregates, whereas group 2 beams were cast with all-natural aggregates (control specimens). All beams were exposed to fire at the above-mentioned temperature followed by testing in universal load testing machine under central point load. Comparison of the results reveals that proposed beams show comparable resistance even after exposed to 6-hours fire at 1000°C.

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45

Kachouh, Nancy, Tamer El-Maaddawy, Hilal El-Hassan e Bilal El-Ariss. "Shear Behavior of Steel-Fiber-Reinforced Recycled Aggregate Concrete Deep Beams". Buildings 11, n. 9 (21 settembre 2021): 423. http://dx.doi.org/10.3390/buildings11090423.

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Abstract (sommario):

Results of an experimental investigation aimed at studying the effect of steel fibers on the shear behavior of concrete deep beams made with a 100% recycled concrete aggregate (RCA) are presented in this paper. The study comprised testing of seven concrete deep beam specimens with a shear span-to-depth ratio (a/h) of 1.6. Two beams were made of natural aggregates (NAs) without steel fibers, two beams were made of a 100% RCA without steel fibers, and three beams were made of RCA-based concrete with steel fibers at volume fractions (vf) of 1, 2, and 3%. Two of the beams without steel fibers included a minimum shear reinforcement. Test results showed that the beam with a 100% RCA without steel fibers exhibited a lower post-cracking stiffness, reduced shear cracking load, and lower shear capacity than those of the NA-based control beam. The detrimental effect of the RCA on the shear response was less pronounced in the presence of the minimum shear reinforcement. The addition of steel fibers significantly improved the shear response of the RCA-based beams. The post-cracking stiffness of the RCA-based concrete beams with steel fibers coincided with that of a similar beam without fibers containing the minimum shear reinforcement. The use of steel fibers in RCA beams at vf of 1 and 2% restored 80 and 90% of the shear capacity, respectively, of a similar beam with the minimum shear reinforcement. The response of the RCA specimen with vf of 3% outperformed that of the NA-based control beam with the minimum shear reinforcement, indicating that steel fibers can be used in RCA deep beams as a substitution to the minimum shear reinforcement. The shear capacities obtained from the tests were compared with predictions of published analytical models.

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46

Michałowska-Maziejuk, Dorota, Barbara Goszczyńska e Wiesław Trąmpczyński. "Effectiveness of strengthening pre-loaded RC beams with CFRP strips in conventional and accelerated strengthening procedures". MATEC Web of Conferences 284 (2019): 06005. http://dx.doi.org/10.1051/matecconf/201928406005.

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Abstract (sommario):

This paper analyses the results obtained from the testing of reinforced concrete beams additionally strengthened with composite materials pressed into the concrete cover using the near-surface-mounted reinforcement (NSMR) method. The testing program comprised two series of beams with cross-sectional dimensions of 0.12 x 0.30 x 3.30 m. The series differed in the amount of longitudinal steel reinforcement, 0.51% and 1.00%. Three beams were cast in each series. One beam was assigned as the control beam, while two other beams were strengthened with carbon fibre strips. A two-component thixotropic epoxy resin was used as a bonding agent. One of the two beams was cured for 7 days (to the product information document). The bonding process in the other beam was accelerated to last 1.5 hours by heating the strip up to 70°C. As the strengthening of "new" elements is not an accepted practice in engineering, the beams were pre-loaded. The load was maintained during the strengthening procedure and curing period (for 7 days and 1.5 hours) and then the beams were monotonically loaded to failure. The comparison of load capacity results for the CFRP strengthened and control beams revealed the effectiveness of the strengthening method. The paper also presents the strengthening technique in the NSMR application with the prototype heating device.

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47

Rochman, Taufiq, e Suhariyanto. "STATE OF THE ART OF TANK STRUCTURAL EVALUATION REVIEW: A CASE STUDY OF AN ELEVATED CONCRETE WATER TANK CONCERNING CRACK INITIATION". Journal of Southwest Jiaotong University 56, n. 5 (30 ottobre 2021): 90–106. http://dx.doi.org/10.35741/issn.0258-2724.56.5.9.

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Abstract (sommario):

This study aims at the structural evaluation of the elevated concrete water tank condition, including crack initiation, through nondestructive testing. The growing demands for environmental quality have resulted in a rise in the design and construction of tanks and reservoirs in the construction industry. Cracks for water line leakage were found during watertight testing in concrete tanks. Long-term liquid leaking may permanently damage the tank and can contaminate the groundwater. Given the critical existence of leaked cracks in tank serviceability and durability, the contribution examines the triggers and effects of their occurrence. An inspection of the existing water tank system is conducted to ascertain its condition. The investigation included structural design checks, concrete compressive strength tests, visual assessments, hammer inspections, and Ultrasonic Pulse Velocity (UPV) testing with Portable Ultrasonic Non-Destructive Digital Indicating Tester (PUNDIT). This observation is made at many elevations on various sampling points on the tank structure's elements, including columns, beams, tank floor slabs, and tank wall shells. The results indicate the presence of flexural type cracks in the main beam's middle span and diagonal beams. Additionally, cracks attributed to long-term drying shrinkage were discovered on the diagonal of the floor slab and cracks of the same pattern on the main beam's middle span. The deflection estimated by structural remodeling was larger than the deflection estimated by design. The computed crack width in the main and diagonal beam exceeds the acceptable crack width.

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48

Seshadri Sekhar, N., P. N. Raghunath, D. Govindarajalu e K. Suguna. "Cyclic Behaviour of High Performance Concrete Beams Strengthened with GFRP Sheets". Applied Mechanics and Materials 813-814 (novembre 2015): 1114–20. http://dx.doi.org/10.4028/www.scientific.net/amm.813-814.1114.

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This paper indicates the difference between the strengthened reinforced high performance concrete beams and the normal reinforced high performance concrete beams. This paper shows the cyclic behaviour of the two types of beams. Experimental investigations were carried out on reinforced High Performance Concrete (HPC) beams of size 150 mm × 250 mm × 3000 mm under both static loading and cyclic loading separately under four point bending. It was observed that the trend in behaviour of the load-deflection curve of the beams was showing the same trend of normal reinforced concrete beams under static loading. In static loading the strain energy absorbed by the beams were observed to be the same as calculated with the area under the load-deflection curve. Other beam was tested under cyclic load separately. The load applied was 35% of static ultimate load which was uniform throughout the fatigue testing of the beams. It was observed that the deflections were increased with the number of cycles. Some of the beams were strengthened by different types and thickness of the GFRP sheets. It was also observed that the strengthened beams withstood more number of cycles than normal HPC beams. The paper presents in detail the experimental investigations conducted on beams and pertinent conclusions drawn therefrom.

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49

Indrayani, Indrayani, Lina Flaviana Tilik, Djaka Suhirkam, Suhadi Suhadi, Muhammad Prawira Wardana e Iros Milawati. "Pengaruh Penambahan Serat Kawat Bendrat Terhadap Kuat Lentur Beton Geopolimer". Bentang : Jurnal Teoritis dan Terapan Bidang Rekayasa Sipil 10, n. 1 (7 gennaio 2022): 69–76. http://dx.doi.org/10.33558/bentang.v10i1.2941.

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Abstract (sommario):

Currently, innovation continues to be developed to replace cement with other materials so that the use of cement as a building material can be reduced. Utilization of coal waste (fly ash) is an alternative to subtitude cement. From previous studies, fly ash mixed with alkaline materials in the form of NaOH and Na2SiO3 in a ratio of 1:5 can produce geopolymer concrete. This geopolymer concrete research was continued by adding bendrat wire fibers into the geopolymer concrete mixture. The method used in testing the aggregate, testing the compressive strength of normal concrete K225, testing the flexural strength of normal concrete and geopolymer concrete refers to SNI. Another additional material that is mixed is bendrat wire fiber. The research was carried out in the form of making flexible beams of 10 cm x 10 cm x 50 cm with fiber variations of 0%, 0.5%, and 1,0% at the age of 14 and 28 days. The results of the flexural strength test of the BN beam at the age of 28 days can withstand loads than BG. The average flexural strength obtained with variations of BN, BN+SB 0.5% and BN+SB 1.0% respectively were 2.796 MPa, 3.113 MPa, and 3.879 MPa. The results of testing the average flexural strength of geopolymer concrete beams at 28 days, obtained variations of BG, BG+SB 0.5%, and BG+SB 1.0% respectively were 0 MPa, 0.055 MPa and 0.104 MPa. In addition, geopolymer concrete cannot be used as a beam and the addition of bendrat wire fiber to geopolymer concrete cannot withstand the tensile load on the concrete.

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50

Bardakov, V. V., A. I. Sagaydak e S. V. Elizarov. "ACOUSTIC EMISSION BEHAVIOUR OF OVER-REINFORCED CONCRETE BEAMS". Kontrol'. Diagnostika, n. 255 (2019): 4–12. http://dx.doi.org/10.14489/td.2019.09.pp.004-012.

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Abstract (sommario):

The paper presents the results of the conducted experimental studies on three-point bend testing of over-reinforced concrete beams with incremental cyclic load, up to destruction, using the acoustic emission method. In total 3 RC beams differ from each other in reinforcement type, concrete composition and ultimate load were tested. Special attention is paid to the investigation of the relationship between destructive processes occurring during the testing of reinforced concrete beams and the evolution of acoustic emission data registered during the test. The analysis described in the article makes it possible, on the basis of acoustic emission data, recorded during the tests, to distinguish the stages corresponding to the different technical state of over-reinforced concrete structures.

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