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Effect of Concrete Strength on Shear Capacity of Reinforced High-Strength Concrete Continuous Beams without Web Reinforcements

Effect of Concrete Strength on Shear Capacity of Reinforced High-Strength Concrete Continuous... Hindawi Advances in Civil Engineering Volume 2023, Article ID 8784575, 10 pages https://doi.org/10.1155/2023/8784575 Research Article Effect of Concrete Strength on Shear Capacity of Reinforced High-Strength Concrete Continuous Beams without Web Reinforcements 1 2 Bamo Ahmed Hasan and Jalal Ahmed Saeed University of Sulaimani, College of Engineering, Architectural Engineering Department, Sulaymaniyah, Kurdistan Region, Iraq University of Sulaimani, College of Engineering, Civil Engineering Department, Sulaymaniyah, Kurdistan Region, Iraq Correspondence should be addressed to Bamo Ahmed Hasan; bamo.hasan@univsul.edu.iq Received 21 August 2022; Revised 13 March 2023; Accepted 30 March 2023; Published 4 May 2023 Academic Editor: Suvash Chandra Paul Copyright © 2023 Bamo Ahmed Hasan and Jalal Ahmed Saeed. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Inordertoevaluatetheshearstrengthandbehaviorofhigh-strengthconcretebeamswithoutwebreinforcing,eighthigh-strength continuous concrete beams with cross sections of 200mm by 300mm were cast and tested to failure. Te ultimate load-carrying capability and shear behavior are presented. Te applicability of the Sudheer et al. equations and ACI 318M-14 is examined. In addition, the efects of the compressive strength (f ) and shear span to efective depth ratio (a/d) on the shear strength and behavior of HSRC beams without stirrups are also studied. 63MPa, 78.8MPa, 85.9MPa, and 92MPa were the concrete’s compressive strengths, while 2.41 and 3.33were its shear spanto efectivedepth ratios. Tere were two equal spans of continuous beams,andateachspan,theywereevaluatedunderasingle-pointload.Itwasfoundthatwithincreasingcompressivestrength,the failure load was increased.But the defection did not afect it signifcantly. While increasing, (a/d) led to a decrease in failure load but increased defection. It was also found that both ACI 318 M-14 and Sudheer et al. equation were more conservative. exceeds fexural strength at every part of the beam. When 1. Introduction high-strength concrete is rapidly loaded in uniaxial com- Reinforced concrete has been the most extensively utilized pression cracks, it can generate a smooth failure surface that material in building since the eighteenth century because of is virtually planar. Unlike lower-strength concrete, which its desirable excellent qualities. Te main property of con- has a rough failure surface, high-strength concrete has crete is its compressive strength, which will be classifed as a smooth failure surface [4]. Dependent on the strength and normal strength concrete (NSC) and high strength concrete location of coarse aggregates, the crack may go through or (HSC) by some publications. High-strength concrete is pass by them, resulting in a quite diferent shear behavior. defned as concrete that has a compressive strength that is Once shear cracking is initiated, both the normal and the tangential displacements occurred at the interface of the signifcantly greater than that used in normal practice [1, 2]. Beams made of reinforced concrete could fail in a variety of cracks. As theaggregates arestrong, the crackwould passby diferent ways. Shear is one of the most common failures in them. Aggregate interlock caused by friction and collision reinforced concrete buildings because it happens un- will be activated in this situation, preventing the tangential expectedly and without warning to the user. Tis might be displacement. However, if the crack penetrates through the due to the difculty in anticipating some other kinds of aggregates, a relatively smooth crack surface would be collapse, or the catastrophic nature of some of the failures if formed, as shown in Figure 1 [5]. theyoccur[3].Becausesheardefeatissuddenandbrittle,the Te crack development mechanism is difcult to com- shear design must ensure that shear strength matches or pletely comprehend, even though it appears to be the 2 Advances in Civil Engineering (a) (b) Figure 1: Consequences of crack interact with an aggregate: (a) pass by and (b) penetrate through [5]. simplest; yet, shear failure of reinforced concrete beams is variables infuencing the degree of the size efect in shear. Tey looked at the variables that afect how strong fexural a very complex occurrence due to the participation of too manyvariables[6].Fivesheartransfermechanismshadbeen beamswithbig,lightreinforcementsareinshear.Teycame to the conclusion that, as the beams grew larger, members identifed: residual tensile stresses transmitted directly across cracks; shear stress in the uncracked compression without stirrups failed in shear at lower shear stresses. zone (the fexural compression zone); interfacial shear Moreover, high-strength concrete structures could collapse transfer caused by aggregate interlock or crack friction; atunexpectedlylowshearlevelsandweremorevulnerableto dowel action of the longitudinal reinforcing bars; and arch the size efect in shear. Tey recommended making a few action [7]. After cracks occur due to fexure the amount of minor changes to the current ACI shear design equation. shear force is taken compression zone. Since the concrete is Te infuence of concrete strength contribution on con- tinuous reinforced concrete beams with two spans was the uncracked, failure is due to a combination of shear and compressive stresses. Tis means that the shear force can be subject of MichaelMcCarty’s [13] M.Sc. thesis. He has made an efort to determine whether shear reinforcement at represented by the compressive strength of the concrete. Whenfracturesappearasaresultoffexure,thecompression maximumspacingcanregulateshearforcesandavertashear zone is accountable for the amount of shear force. Tis failure. Concrete had a compressive strength range of means that the concrete’s compressive strength may be used 4948psi (34MPa) to 6255psi (43MPa). Motamed [14] had to represent the shear force. Kani [8] concluded that small presented a Ph.D. dissertation about the behavior of (a/d) beams had higher shear strength. Te term (M/Vd) amonolithicbeamatexternalcolumnjointsandtheefectof contains a theoretical representation involving bending the central vertical bar (CVB) on joint shear behavior. Tey moment (M), shear force (V), and efective depth (d). (M/ employed two diferent types of concrete: high-strength Vd) still has physical signifcance at any cross-section of concrete, whose compressive strength ranged from 87.2MPa to 94.48MPa, and normal-strength concrete, abeam.Inaddition,Brianetal.[9]showedthatregardlessof thekindofthecoarseaggregatematerialemployed,theshear whose compressive strength ranged from 32.8MPa to 38.16MPa.Hecametotheconclusionthattheshearcapacity span-to-depth ratio was found to signifcantly infuence the shear strength of beams. Because continuous beams con- of NSC beams with the same geometry and reinforcement stitute the majority of the actual construction, un- and an a/d �3.02 span/depth ratio was lower or equal to the derstanding the efect of continuity on shear behavior is shear capacity ofHSC beams. In aresearch study byNwofor critical. Rodriguez et al. [10] had studied the efects of et al. [15], the most economical design for six continuous continuity on the shear strength of statically indeterminate reinforced concrete beams was compared to that of Euro- parts, the function of web reinforcement in shear strength, code 2 and BS 810-97. Tey came to the conclusion that the BS8110 shear forces at supports surpassed the Eurocode2 by and the minimal amount of web reinforcement required to prevent shear failures. Te test’s parameters included anaverageofaround1.19%forboththetopandlowerlimits ofshearforce.And,theEurocode2ismorecautiousinterms loading type, fexural reinforcement grade, spacing and percentage of web reinforcement, cut-of or extension of of partial factors of safety for loadings. For the combination longitudinal reinforcement, and a nominal compressive of live and dead loads examined in this study, the maximum strength of 3500psi (24.1MPa). A study on the behavior of design loads required by the BS 8110 were almost 1.3% simple and continuous fber-reinforced polymer beams was higherthanthoserequired bytheEurocode2.Tenecessary published by Grace et al. [11]. Te concrete’s compressive margin of safety was maintained while a more cost-efective strength was 48.26MPa. Tey came to the conclusion that designwaspossiblethankstoEurocode2.Twelvereinforced the use of GFRP stirrups signifcantly enhanced beam de- concrete beams, eight without stirrups, and four with shear fectionsanddeformedshear.Furthermore,theuseofGFRP reinforcement, had been tested by Aguilar et al. [16]. Te compressivestrengthofconcretevariedfrom48to105MPa. stirrups rather than steel stirrups resulted in a signifcant number of small, inclined cracks that covered roughly two- Teywantedtoknowifhigh-strengthconcretecouldusethe minimum and maximum shear reinforcement levels in- thirdsofthespan.Michael[12]releasedanarticledescribing a thorough experimental study to identify the critical dicated in the AASHTO LRFD 14 standards and the ACI Advances in Civil Engineering 3 Table 1: Mix proportions. Code 318-14. Tey came to the conclusion that both AASHTO LRFD and ACI 318’s conservatism had di- Types A B C D minished as the amount of shear reinforcement increased. Cement (kg/m ) 400 500 500 500 Ahmad et al.’s [17] investigation of moment redistribution Silika fume (kg/m ) — — 50 55 behavior under fexural and shear stresses in continuous 3 Sand (kg/m ) 900 904 900 840 concrete beams reinforced with glass fber-reinforced Gravel (kg/m ) 791 931 875 830 polymer (GFRP). Te analysis system (ANSYS) was used HRWRA (kg/m ) — 2.3 6.875 7.5 to generate a fnite element model. Te predictive shear Water (kg/m ) 170 190 160 125 capabilities of the analytical model, the produced fnite el- (w/cm) 0.425 0.38 0.291 0.23 f (MPa) 63.0 78.8 85.9 92.0 ement model, and the data from the literature were all compared. Tis study demonstrated the efectiveness of ANSYS software as a tool for simulating GFRP re- inforcement.Itwasfoundthattheresultsoftheexperiments and the fnite element analysis were in perfect accord. As was previously mentioned, a variety of factors afect how strong shear beams made of high-strength reinforced concreteare.Itischallengingtoanalyzeonecomponentand isolate it from other factors since the impacts of diferent factors interact with one another. Tere aremany studies on simply supported beams, but fewer studies than simply supported ones cover continuous beams. Terefore, the main objective of this study is to determine the efect of continuity on the shear strength of statically 0.1 1 10 indeterminate beams. Figure 2: Grading of fne aggregate with ASTM C33 limits [19]. 2. Objectives of the Study [19] limits, crushed stone with 12.5mm maximum size, the (1) To measure the shear strength of continuous beams grading conformed ASTM C33 [19] specifcations, shown in made of high-strength reinforced concrete without Figure3,andordinarydrinkingtapwaterwereused.Also,to web reinforcement achieve the workability and strength of concrete, a water (2) To study how the a/d ratio and compressive strength reducing admixture, Sika ViscoCrete 5930L super plasti- f afect the shear strength of high-strength rein- cizer, was needed to make the concrete mix workable, in forced concrete beams without stirrups when sub- addition to the Silica fume. Finally, deformed steel bars with jected to a concentrated loads nominal diameters of 20mm and 538MPa yield strength were used as fexural reinforcements and 8mm with 3. Methodology 520MPa yield strength were used for shear reinforcements, whose properties shown in Table 2. Tofulflltheabove-givenobjectives,aresearchprogramthat includes experimental and numerical phases is proposed. Te experimental phase consists of casting and testing 8 4.2. Beam Details. Te variables are concrete compressive concrete beams continuously over two spans. Also, the strength and shear span to efective depth ratio. All the comparison made between the ultimate shear strength ac- beams have the same cross-section (200mm width and quired from test data with values calculated from ACI and 300mm height) and longitudinal reinforcement ratio other researchers’ predictions. (3 ∅20mm). Beam details are explained in the Table 3. Te specimens were divided into four groups A, B, C, and D according to their concrete compressive strengths. In Fig- 4. Experimental Program ures 4 and 5 reinforcement details were explained. All the 4.1. Materials. To reach the required mix design of high- beams were designed so that failure will occur due to shear. strength concrete mixtures, instructions and directions of Also,theyweresochosenthattheydonotfailintheexterior ACI 211.4R [18] and ACI 363.2R [2] guides have been support regions. followed. To reach the required concrete strengths, four types of mixes were used. Tese mixes were obtained after conducting more than thirty trials. Te mixed proportions 4.3. Mechanical Properties of Concrete. Figure 6 show are summarized in Table 1. curves of stress-strain diagrams. To obtain Compressive Te selection of the raw components for concrete had Strength f three 150 ×300mm cylinders were taken been controlled by ASTM regulations. Ordinary Portland according to ASTM C 39/C 39M [20]. Tree cement, locally manufactured at the Tasluja factory in 100 ×100 ×500mm prisms were taken in accordance Sulaimani,NorthIraq,locallynaturalsandfromriver,whose with ASTM C78/C78M [21] utilizing simple beams with propertiesshowninFigure2,whichconformstoASTMC33 third-point stress in order to obtain the modulus of 4 Advances in Civil Engineering 120 100 0 500 1000 1500 2000 2500 3000 Microstrain Type A Type C 1 10 100 Type B Type D Figure 3: Grading of course aggregate with ASTM C33 limits [19]. Figure 6: Stress-strain curves. Table 2: Properties of the reinforcing steel bars. 4.4. Instruments. After the preparation of the molds using Steel bar Diameter (mm) f (MPa) f (MPa) Types of use y u plywood sheets, the next stage began with the construction 8 7.68 317 520 Stirrups of the cage, by assembling the main reinforcement bars with Main the stirrups as shown in Figure 7, and they were explained 20 19.72 538 680 reinforcement previously in the fgures and tables. Ten, the strain gauges were fxed to the predetermined location on the re- inforcements using glue. After that the strain gauges were covered with special tape, made for electrical joints, to Table 3: Details of specimens. protect their moisture, impact, or damage during casting. Dimensions Finally, the cage was placed inside the plywood mold after Longitudinal (mm) Groups Beam a/d f (MPa) c brushing inside with oil to make the removal of the forms reinforcement B H a easy after casting the beams. Casting was started along the length of the beams and 11 200 300 650 2.41 3∅20mm A 63.0 21 200 300 900 3.33 3∅20mm was flled in two layers each layer was compacted using an internalvibrator.Teuppersurfaceofthemoldswasleveled 11 200 300 650 2.41 3∅20mm B 78.8 with a steel trowel. Tis process was continued until the 21 200 300 900 3.33 3∅20mm casting of the group was completed. Side by side of this 11 200 300 650 2.41 3∅20mm C 85.9 process, nine cylinders (150∗300) mm and three prisms 21 200 300 900 3.33 3∅20mm (100∗100∗500) mm were cast to obtain compressive 11 200 300 650 2.41 3∅20mm D 92.0 strength, splitting tensile strength, modulus of rupture, and 21 200 300 900 3.33 3∅20mm modulus of elasticity. After 24hours, the sides of the molds andcontrolspecimenswereremoved.Tecuringprocessfor Ф 8 mm @ 80 mm C/C 3 Ф 20 mm 140 mm the beams and the control specimens started and all of them were covered with wet burlap and kept wet for more than 90days. Te beams were tested under a universal machine with a hydraulic jack of 2000kN (200ton), 700bar, and 3 Ф 20 mm 500 mm 650 mm maximum capacity as explained in Figures 8 and 9. Figure 4: Reinforcement detail for beam 1. To obtain reactions and loads, load cells of type S8920 were placed beneath the exterior reaction and loaded. As shown in Figure 10, these load cells were manufactured by 3 Ф 20 mm 140 mm Ф 8 mm @ 80 mm C/C SEWHACNM. Tree (linear variable displacement trans- ducer)LVDTwereused,thefrstonealongtheinclinedstrut location, the second on the compression fber of the load, 3 Ф 20 mm 500 mm 900 mm and the third one along the compression fber of the middle support. Also, precision electronic strain gauges were used Figure 5: Reinforcement detail for beam 2. along the diagonal strut between the middle support and loading points. For measuring the strain of stirrups and mainreinforcements,precisionelectronicstraingaugeswere rupture. Elasticity modulus were made in accordance used. Te positions of strain gauges were shown in with ASTM C 469/C 469M [22]. Finally, to determine Figures 11–14. splitting tensile strength, three additional 100 ×200mm A linear variable displacement transducer (LVDT) was cylinders were obtained in compliance with ASTM C used under the point load to measure the defection that 496/C 496M [23]. Table 4 presents the results for the occurred during the loading process. And, a data logger of control specimens. Stress (MPa) Advances in Civil Engineering 5 Table 4: Test results of the control specimens. 2 2 2 2 Types f (N/mm ) f (N/mm ) f (N/mm ) E (N/mm ) c r sp c strain gauge 1 strain gauge 1 A 63 5.1 4.0 33255 B 78.8 5.9 4.7 36371 500 mm a a 500 mm C 85.9 6.2 5.0 37670 Figure 11: Placement of concrete electronic strain gauges. D 92 6.5 5.2 38752 Figure 7: Reinforcement cages. Load Load Figure 12: Linear variable displacement transducer (LVDT). 500 mm aa 500 mm Figure 8: Test arrangement of typical beam specimen. Figure 13: Placement of steel strain gauges. Figure 9: Beam specimen under loading machine. Figure 14: Electronic steel strain gauges. leftsupporttodeterminethesupportreactionsinadditionto total load accurately to determine the shear force in each span. A wide fange steel beam was used to divide the hy- draulic jack force into two-point loads. A thick plate (200∗60 ∗20) mm was used to prevent the local bearing failure at the point of load application. Te test was started under force control with a specifc loadincreaseof10kNto15kNoncetheprecedingprocesses hadbeenfnished.Avisualinspectionwasconductedateach load increase, and any cracks were marked. Te crack propagation was examined at each load increment, and the location, load size, and newly formed cracks were noted and Figure 10: Load cells. documented.Teweightwasincreasedincrementallyduring this procedure until the beam fnally failed. the type Windmill 851 was used to collect all the data from 5. Test Results and Discussions the strain gauges, LVDTs, and loads cells. 5.1. Crack Propagation and Failure Load. Atbeginningofthe 4.5. Test Procedure. All the beams were tested in a loading loadingprocess,withloads,allthebeamsbehavedelastically. frame through one hydraulic jack of 2000kN capacity, with Te stresses were small and below proportional limits, three support reactions. Load cells had been put beneath the consequently, the beams were free of cracks and the 6 Advances in Civil Engineering Table 5: Failure load of the beams. defections were small. Te frst crack was vertical, due to fexural stress. After the formation of the frst crack, they Moment at Failure load Exterior reaction were followed by more similar fexural cracks. Further new Beams interior support (kN) (kN) fexural cracks formed in both the hogging and sagging (kN·m) fexural regions as the load was increased. With increasing A11 356.1 157.05 50.8575 the loads, the fexural cracks near the supports propagated A21 264.55 114.08 78.383 diagonally toward the loading point. Te cracks grew wider B11 433.099 192.08 60.6234 and propagated toward each other. Before the beams fail, B21 292.641 144.62 60.909 a diagonal crack is initiated at the midheight of the beam. C11 471.6 191.74 86.039 C21 325.74 160.59 68.34 Before the failure, as the load increased, the number of D11 542.2 231.21 86.5385 cracksdidnotincrease,butthedepthandwidthofthecracks D21 356.258 178.09 71.3062 had increased. Te failure loads of the beams are shown in Table 5. Te crack pattern of beams is shown in Figures15–18forcastinggroupsA,B,C,andD,respectively. 5.2. Efect of Compressive Strength on Load-Defection Be- havior and Ultimate Load. Te relation between defection andloadis showninFigures19 and20.Ingeneral,whenthe concrete compression strength increases, the ultimate load of failure of the beams increases too. Te experimental Figure 15: Crack pattern for beam of group A. resultsshowedthatfor beamseries1,beamswithshearspan to depth ratio (a/d) 2.41 when the compression of the concrete increased from 63MPa to 78.8MPa the ultimate load increased 121.6%. By changing the compressive strength from 63MPa to 85.9MPa the ultimate load in- creased132.4%.Whilethechangingofcompressivestrength from 63MPa to 92MPa lead to an increase in the ultimate load by 1.523%. For shear span to depth ratio (a/d) 3.33, beam series 2, when the compressive strength increased Figure 16: Crack pattern for beam of group B. 1.25% as well as the ultimate load increased 1.106%. Te increase in concrete strength of 136.4% was followed by the increase in the ultimate load of the beam by 123.1%. Also, raising the compressive strength by 146% was reasoned to increase the ultimate load by 134.7%. In contrast to the ultimate load, it was found that with increasing concrete compressive strength the defection response was not in the same attitude. In some groups, we observed that with increasing concrete strength displace- Figure 17: Crack pattern for beam of group C. ment decreases, but not in a constant proportion while in some other groups increasing compressive strength caused to increase in the defection of the beam. We noted that the load-defection curves could be divided into two distinct stages, precracking and postcracking. In the frst stage, the curvewasalmostlinear.Afterformationofthecrackscauses a reduction in the beam stifness and leads to a changing slope of the curve. Also, it was observed that when the compressivestrengthoftheconcretewasincreasedtheslope Figure 18: Crack pattern for beam of group D. of the frst stage of the curve, precrack, became steeper. 5.3. Efect of Shear Span to Efective Depth Ratio on Load- efective depth ratios (a/d) 2.41 and 3.33. Te results of the Defection Behavior and Ultimate Load. Te shear span to tested beams showed that for beams with compressive efective depth ratio is one of the most essential aspects strength of concrete 63MPa, changing a/d from 2.41 to 3.33 afecting the beam’s resistance and behavior. Te infuence the ultimate load decreased from 356.1kN to 264.55kN, of the force moment increases as the distance between the 74.3%, as shown in Figure 21. For beams, with concrete load and the support increases, and in the presence of the compressive strength of 78.8, MPa changing a/d led to force moment, the fractures in the section expand and the adecreaseintheultimateloadby67.57%,from433.1MPato efective depth of the section falls, reducing the section’s 292.64MPa, as shown in Figure 22. Beams of type C, with resistance to shear. In this study, we got two shear span to concrete compressive strength of 85.9MPa, changing in Advances in Civil Engineering 7 600 600 0 2468 Deflection (mm) A11 B11 C11 D11 A11 C11 B11 D11 Figure 19: Load-defection curve and ultimate load for beam 1. 0 2468 10 Deflection (mm) A21 B21 C21 D21 A21 C21 B21 D21 Figure 20: Load-defection curve and ultimate load for beam 2. 􏽱�� 􏽱�� shear span to efective depth ratio reduced the ultimate load V d ′ ′ V � 0.16 f + 17 ρ b dbut≤0.29 f b d, 􏼢 􏼠 􏼡􏼣 69.07%, from 471.6MPa to 325.74%, as shown in Figure 23. c c w w c w Te last group was beams of type D, with concrete com- (1) pressive strength of 92MPa. When the aspect ratio, a/d, changed the ultimate load changed too, from 542.2MPa to where V ; Nominal shear strength provided by concrete, N 356.26MPa, 65.71%, as shown in Figure 24. f ; Compressive strength of Concrete, N/mm , ρ ; Longi- c w It is commonly known that the defection grew along tudinal fexural reinforcement ratio, A /b d, V ; Shear force s w u withthespan.Temomentofforce increasesasthedistance at the section considered, N, M ; Moment at the section between the supports increases, increasing the defection as considered, N·mm, b ; Web width, mm, d; and Efective a consequence. We came to the conclusion that raising the depth, mm aspect ratio, a/d, produced an increase in the defection ACI stated that V d/M shall not be greater than 1.0. under the point load after examining the curves of the re- Table 6 presents the calculated shear strength versus lationship between load and defection of the tested beams. tested shear. Tese increases were varied rather than consistent. 6.2. Te Equation Proposed by Sudheer et al. for Shear Pre- 6. Comparing Test Results with diction [25]. In 2010, Sudheer et al. developed the linear Other Provisions regression equation in power series to calculate the shear resistanceofhigh-strengthconcretebeamswhileaccounting Inthisarticle,theresultsofthetestsarecomparedtotheACI for the concrete’s tensile strength, fexural reinforcement, code, with two diferent researcher approaches presented. and the (a/d) ratio: TeACI318M-19equationforcalculatingtheshearstrength provided by concrete for nonprestressed members Te 0.8 f ρ modifed Zsutty equation and the equation proposed by (2) V � 32 􏼠 􏼡 b d, c w Sdheer et al. were compared. (a/d) where V , Shear strength provided by concrete, N, f , c t 6.1. ACI 318M Equation for Shear Prediction. For member Tensile strength of concrete, N/mm , a/d, Shear span to subjected to shear and fexure ACI 318M-14 proposed the depth ratio. ρ Longitudinal fexural main reinforcement following equation [24]: ratio, and b , d Web width, efective depth, mm Force (kN) Force (kN) Force (kN) Force (kN) 8 Advances in Civil Engineering 0 2468 Deflection (mm) A11 A21 A11 A21 Figure 21: Load-defection curve and ultimate load for beams A11 and A21. 400 500 0 2468 10 Deflection (mm) B11 B21 B11 B21 Figure 22: Load-defection curve and ultimate load for beams B11 and B21. 0 2468 Deflection (mm) 200 C11 C21 C11 C21 Figure 23: Load-defection curve and ultimate load for beams C11 and C21. 0 2468 Deflection (mm) D11 D21 D11 D21 Figure 24: Load-defection curve and ultimate load for beams D11 and D21. Force (kN) Force (kN) Force (kN) Force (kN) Force (kN) Force (kN) Force (kN) Force (kN) Advances in Civil Engineering 9 Table 6: Test predicted shear result based on ACI code. V V c c ′ ′ Beam f f ρ V d/M b d V /V c w ACI Test ACI tested A11 0.0056 1 200 270 73718.7 356100 0.20701678 A21 0.0056 0.518312644 200 270 71242.42 264550 0.2692966 B11 0.0056 1 200 270 81837.53 433099 0.18895802 78.8 B21 0.0056 0.656154848 200 270 80069.89 292641 0.27361132 C11 0.0056 0.878231965 200 270 84592.28 471600 0.17937295 85.9 C21 0.0056 0.652480246 200 270 83431.74 325740 0.25612985 D11 0.0056 0.970288369 200 270 87860.03 542200 0.16204358 D21 0.0056 0.674630818 200 270 86340.11 356258 0.24235276 Table 7: Test and predicted shear result based on Sudheer et al. equation. Beam f ρ a/d V Sudheer V tested V /V c c t Sudheer Test A11 0.0056 2.4 41074.6 356100 0.11534564 A21 0.0056 3.33 31607.3 264550 0.11947554 B11 0.0056 4.26 29528.7 433099 0.06818009 4.7 B21 0.0056 5.19 25213.8 292641 0.08615954 C11 0.0056 6.12 23220.4 471600 0.04923741 C21 0.0056 7.05 20735.7 325740 0.06365724 D11 0.0056 7.98 19377.4 542200 0.03573839 5.2 D21 0.0056 8.91 17741.7 356258 0.04980008 Tepredictedresultsbasedonequation(2)arepresented a decrease the defection. Also, when the concrete inTable7,alongwithacomparisonofthepredictedandtest became stronger, the ductility reduced and the results. concrete became more brittle. Te V /V values measure the equation’s predicted tested (3) In beams with a/d �2.41, Increasing compressive conservation,andifthisnumberislessthan1.0,theequation strength by 125% caused the ultimate to increase is on the safe side because it overestimates the true value of by 121%. And, ultimate load 132% because of the beam. Te following broad conclusions can be drawn increasing compressive strength 136%. Also, this based on the information in these tables: increase continued and reached 152% when compressive strength increased by 146%. Also, (1) FortheACIequation,when a/dincreased,thevalues when a/d �3.33, the increase in ultimate load was became less conservative; this may be because of the 111%, 123%, and 135% when the compressive efect of the fexural moment strength increased 125%, 136, and 146%, (2) Te equation proposed by Sudheer et al. was more respectively. conservative, and the predicted values decreased as (4) When a/d increased, the defection of the beams the tensile strength of concrete increased increased, too. (5) For concrete strength of 63MPa, increasing a/ 7. Conclusions d from 2.41 to 3.33 caused to decrease in the ulti- mate strength of 74%, and defection increased by Te results of a study on the strength and behavior of 137%. reinforced high-strength continuous concrete beams were (6) For beams group B (78.8MPa) changing a/d led to summarizedinthispaper.Tefollowingconclusionsmaybe a decrease in ultimate load of 68% and increased taken from the scope of this study: defection by 143%. (1) As the compressive strength of concrete was in- (7) For beams group C (85.9MPa) the ultimate load creased, the concrete became more fragile and the decreased 69% and defection increased 152% be- correspondingstraindecreased.And,increasingthe cause of changing a/d from 2.41 to 3.33. compressive strength led to an increase in the ul- (8) For beams group D (92MPa) the ultimate load timate load of the beams. decreased 66% and defection increased 123%. (2) Te increase of concrete compressive strength (9) Te values for the ACI equation became less con- caused a slight decrease in the defection of the servative as a/d increased; the fexural moment beams because the increasing concrete strength might have had something to do with this. caused to increase in stifness and this led to 10 Advances in Civil Engineering [9] J. O. Brian, N. M. Raphael, N. Timothy, and A. G. Zachary, (10) Te values predicted by Sudheer et al.’s equation “Shear performance of concrete beams with a maximum size decreased as concrete’s tensile strength increased, ofrecycledconcreteaggregate,” Advances in Materials Science and they were more conservative. and Engineering,vol.2022,ArticleID6804155,17pages,2022. [10] J. J. Rodriguez, A. C. Bianchini, I. M. Viest, and E. K. Clyde, 8. Further Study Recommendations “Shear Strength of two-span continuous reinforced concrete beams,” Journal of the American Concrete Institute, vol. 30, Te following suggestions may be useful for further work: no. 10, pp. 1089–1130, 1959. [11] N. F. Grace, A. K. Soliman, G. Abdel-Sayed, and K. R. Saleh, (1) Experimental and analytical studies about the shear “Behavior and ductility of simple and continuous FRP behavior of continuous beams with diferent cross- reinforced beams,” Journal of Composites for Construction, sections, such as L-shaped and T-shaped sections. vol. 2, no. 4, pp. 186–194, 1998. (2) Inthisstudy,specimensweretestedunderone-point [12] P. Michael, “Collins and daniel Kuchma,” How Safe Are Our loads in each span. It is better to test a series of Large, Lightly Reinforced Concrete Beams, Slabs, and Foot- continuous beams under diferent loading arrange- ings?” ACI Structural Journal,vol.96,no.4,pp.482–491,1999. [13] C. Michael McCarty, “Behavior of two-span continuous ments than a one-point load in each span. reinforced concrete beams,” M. Sc. Tesis, Russ College of (3) Experimental and analytical study about the efect of EngineeringandTechnologyofOhioUniversity,Athens,OH, unsymmetricalspansonshearstrengthofreinforced USA, 2008. high-strength continuous beams. [14] J. Motamed, “Monolithic to external column joints in rein- forced concrete,” Ph. D. thesis, University of Westminster, UK, London, 2010. Data Availability [15] T.C.Nwofor,S.Sule,andD.B.Eme,“Acomparativestudyof BS8110 and Eurocode2 standards for design of a continuous Te data used to support the study are available from the reinforced Concrete Beam,” International Journal of Civil corresponding author upon request. Engineering and Technology, vol. 6, no. 5, pp. 76–84, 2015. [16] G. Aguilar, S. Villamizar, and J. A. Ramirez, “Evaluation of Conflicts of Interest shear reinforcement design limits in high-strength concrete beams,” ACI Structural Journal Concrete Beams, vol. 115, Te authors declare that they have no conficts of interest. no. 2, 2018. [17] H. Ahmad, A. Elnemrm, N. Ali, Q. Hussain, K. Chaiyasarn, and P. Joyklad, “Finite element analysis of glass fber- Acknowledgments reinforced polymer-(GFRP) reinforced continuous concrete beams,” Polymers, vol. 13, no. 24, p. 4468, 2021 Dec 20. TestudywassupportedbyUniversityofSulaimani,College [18] Aci 211 4R-11, “Guide for selecting proportions for high- of Engineering, Sulaymaniyah, Kurdistan Region, Iraq. strength concrete using portland cement and other cemen- titiousmaterials,”ReportedbyACICommittee211,American References Concrete Institute, Michigan, MG, USA, 2011. [19] AstmDesignationC33/C33M–13, Standard Specifcation for [1] Aci committee 363R-10, “Report on high strength concrete,” Concrete Aggregates, Annual Book of ASTM Standard, West Reported by ACI Committee 363, American Concrete In- Conshohocken, PA, USA, 2015. stitute, Michigan, MG USA, 2010. [20] AstmDesignationC39/C39M–03, Standard Test Method for [2] Aci committee 363.2R-11, “Guide to quality control and Compressive Strength of Cylindrical Specimens, Annual Book assurance of high strength concrete,” Reported by ACI of ASTM Standard, West Conshohocken, PA, USA, 2004. Committee 363, American Concrete Institute, Michigan, MG [21] AstmDesignationC78/C78M–15, Standard Test Method for USA, 2011. Flexural Strength of Concrete (Using Simple Beam with Tird- [3] D.Darwin,C.W.Dolan,andA.H.Nilson, Design of Concrete Point Loading), Annual Book of ASTM Standard, West Structures, McGraw-Hill Book Company, New York, NY, Conshohocken, PA, USA, 2015. USA, 2016. [22] Astm Designation C 469/C 469M – 14, Standard Test Method [4] J. G. M. van Mier, “Failure of concrete under uniaxial for Static Modulus of Elasticity and Poisson’s Ratio of Concrete compression: an over view,” Fracture Mechanics Of Concrete in Compression, Annual Book of ASTM Standard, West Structures, vol. 2, 1998. Conshohocken, PA, USA, 2015. [5] Q. Deng, Y. Wei-Jian, and T. Fu-Jian, “Efect of coarse ag- [23] Astm Designation C 496/C 496M – 11, Standard Test Method gregate size on shear behavior of beams without shear re- for Splitting Tensile Strength of Cylindrical Concrete Specimens, inforcement,” ACI Structural Journal, vol. 114, no. 5, Annual Book of ASTM Standard, West Conshohocken, PA, pp. 1131–1142, 2017. USA, 2015. [6] A. Ghafar, J. Afzal, and U. R. Habib, “Development of shear [24] Aci 318M-14, Building Code Requirements for Structural capacity Equations for rectangular reinforced concrete Concrete (ACI 318M-14) an ACI Standard and Commentary, beams,” Journal of Engineering and Applied Science, vol. 6, American Concrete Institute, Michigan, MG, USA, 2014. pp. 1–8, 2010. [25] L. Sudheer Reddy, N. V. Ramana Rao, and T. D. Gunneswara [7] ACI-ASCE committee 445 on shear and torsion, “Recent Rao, “Shear resistance of high strength concrete beams approaches to shear design of structural concrete,” Journal of without shear reinforcement,” International Journal of Civil Structural Engineering, vol. 124, no. 12, pp. 1375–1417, 1998. and Structural Engineering, vol. 1, no. 1, pp. 101–113, 2010. [8] G. N. J. Kani, “Basic Facts Concerning Shear Failure,” ACI Journal, vol. 63, pp. 675–692, 1966. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Advances in Civil Engineering Hindawi Publishing Corporation

Effect of Concrete Strength on Shear Capacity of Reinforced High-Strength Concrete Continuous Beams without Web Reinforcements

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Hindawi Advances in Civil Engineering Volume 2023, Article ID 8784575, 10 pages https://doi.org/10.1155/2023/8784575 Research Article Effect of Concrete Strength on Shear Capacity of Reinforced High-Strength Concrete Continuous Beams without Web Reinforcements 1 2 Bamo Ahmed Hasan and Jalal Ahmed Saeed University of Sulaimani, College of Engineering, Architectural Engineering Department, Sulaymaniyah, Kurdistan Region, Iraq University of Sulaimani, College of Engineering, Civil Engineering Department, Sulaymaniyah, Kurdistan Region, Iraq Correspondence should be addressed to Bamo Ahmed Hasan; bamo.hasan@univsul.edu.iq Received 21 August 2022; Revised 13 March 2023; Accepted 30 March 2023; Published 4 May 2023 Academic Editor: Suvash Chandra Paul Copyright © 2023 Bamo Ahmed Hasan and Jalal Ahmed Saeed. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Inordertoevaluatetheshearstrengthandbehaviorofhigh-strengthconcretebeamswithoutwebreinforcing,eighthigh-strength continuous concrete beams with cross sections of 200mm by 300mm were cast and tested to failure. Te ultimate load-carrying capability and shear behavior are presented. Te applicability of the Sudheer et al. equations and ACI 318M-14 is examined. In addition, the efects of the compressive strength (f ) and shear span to efective depth ratio (a/d) on the shear strength and behavior of HSRC beams without stirrups are also studied. 63MPa, 78.8MPa, 85.9MPa, and 92MPa were the concrete’s compressive strengths, while 2.41 and 3.33were its shear spanto efectivedepth ratios. Tere were two equal spans of continuous beams,andateachspan,theywereevaluatedunderasingle-pointload.Itwasfoundthatwithincreasingcompressivestrength,the failure load was increased.But the defection did not afect it signifcantly. While increasing, (a/d) led to a decrease in failure load but increased defection. It was also found that both ACI 318 M-14 and Sudheer et al. equation were more conservative. exceeds fexural strength at every part of the beam. When 1. Introduction high-strength concrete is rapidly loaded in uniaxial com- Reinforced concrete has been the most extensively utilized pression cracks, it can generate a smooth failure surface that material in building since the eighteenth century because of is virtually planar. Unlike lower-strength concrete, which its desirable excellent qualities. Te main property of con- has a rough failure surface, high-strength concrete has crete is its compressive strength, which will be classifed as a smooth failure surface [4]. Dependent on the strength and normal strength concrete (NSC) and high strength concrete location of coarse aggregates, the crack may go through or (HSC) by some publications. High-strength concrete is pass by them, resulting in a quite diferent shear behavior. defned as concrete that has a compressive strength that is Once shear cracking is initiated, both the normal and the tangential displacements occurred at the interface of the signifcantly greater than that used in normal practice [1, 2]. Beams made of reinforced concrete could fail in a variety of cracks. As theaggregates arestrong, the crackwould passby diferent ways. Shear is one of the most common failures in them. Aggregate interlock caused by friction and collision reinforced concrete buildings because it happens un- will be activated in this situation, preventing the tangential expectedly and without warning to the user. Tis might be displacement. However, if the crack penetrates through the due to the difculty in anticipating some other kinds of aggregates, a relatively smooth crack surface would be collapse, or the catastrophic nature of some of the failures if formed, as shown in Figure 1 [5]. theyoccur[3].Becausesheardefeatissuddenandbrittle,the Te crack development mechanism is difcult to com- shear design must ensure that shear strength matches or pletely comprehend, even though it appears to be the 2 Advances in Civil Engineering (a) (b) Figure 1: Consequences of crack interact with an aggregate: (a) pass by and (b) penetrate through [5]. simplest; yet, shear failure of reinforced concrete beams is variables infuencing the degree of the size efect in shear. Tey looked at the variables that afect how strong fexural a very complex occurrence due to the participation of too manyvariables[6].Fivesheartransfermechanismshadbeen beamswithbig,lightreinforcementsareinshear.Teycame to the conclusion that, as the beams grew larger, members identifed: residual tensile stresses transmitted directly across cracks; shear stress in the uncracked compression without stirrups failed in shear at lower shear stresses. zone (the fexural compression zone); interfacial shear Moreover, high-strength concrete structures could collapse transfer caused by aggregate interlock or crack friction; atunexpectedlylowshearlevelsandweremorevulnerableto dowel action of the longitudinal reinforcing bars; and arch the size efect in shear. Tey recommended making a few action [7]. After cracks occur due to fexure the amount of minor changes to the current ACI shear design equation. shear force is taken compression zone. Since the concrete is Te infuence of concrete strength contribution on con- tinuous reinforced concrete beams with two spans was the uncracked, failure is due to a combination of shear and compressive stresses. Tis means that the shear force can be subject of MichaelMcCarty’s [13] M.Sc. thesis. He has made an efort to determine whether shear reinforcement at represented by the compressive strength of the concrete. Whenfracturesappearasaresultoffexure,thecompression maximumspacingcanregulateshearforcesandavertashear zone is accountable for the amount of shear force. Tis failure. Concrete had a compressive strength range of means that the concrete’s compressive strength may be used 4948psi (34MPa) to 6255psi (43MPa). Motamed [14] had to represent the shear force. Kani [8] concluded that small presented a Ph.D. dissertation about the behavior of (a/d) beams had higher shear strength. Te term (M/Vd) amonolithicbeamatexternalcolumnjointsandtheefectof contains a theoretical representation involving bending the central vertical bar (CVB) on joint shear behavior. Tey moment (M), shear force (V), and efective depth (d). (M/ employed two diferent types of concrete: high-strength Vd) still has physical signifcance at any cross-section of concrete, whose compressive strength ranged from 87.2MPa to 94.48MPa, and normal-strength concrete, abeam.Inaddition,Brianetal.[9]showedthatregardlessof thekindofthecoarseaggregatematerialemployed,theshear whose compressive strength ranged from 32.8MPa to 38.16MPa.Hecametotheconclusionthattheshearcapacity span-to-depth ratio was found to signifcantly infuence the shear strength of beams. Because continuous beams con- of NSC beams with the same geometry and reinforcement stitute the majority of the actual construction, un- and an a/d �3.02 span/depth ratio was lower or equal to the derstanding the efect of continuity on shear behavior is shear capacity ofHSC beams. In aresearch study byNwofor critical. Rodriguez et al. [10] had studied the efects of et al. [15], the most economical design for six continuous continuity on the shear strength of statically indeterminate reinforced concrete beams was compared to that of Euro- parts, the function of web reinforcement in shear strength, code 2 and BS 810-97. Tey came to the conclusion that the BS8110 shear forces at supports surpassed the Eurocode2 by and the minimal amount of web reinforcement required to prevent shear failures. Te test’s parameters included anaverageofaround1.19%forboththetopandlowerlimits ofshearforce.And,theEurocode2ismorecautiousinterms loading type, fexural reinforcement grade, spacing and percentage of web reinforcement, cut-of or extension of of partial factors of safety for loadings. For the combination longitudinal reinforcement, and a nominal compressive of live and dead loads examined in this study, the maximum strength of 3500psi (24.1MPa). A study on the behavior of design loads required by the BS 8110 were almost 1.3% simple and continuous fber-reinforced polymer beams was higherthanthoserequired bytheEurocode2.Tenecessary published by Grace et al. [11]. Te concrete’s compressive margin of safety was maintained while a more cost-efective strength was 48.26MPa. Tey came to the conclusion that designwaspossiblethankstoEurocode2.Twelvereinforced the use of GFRP stirrups signifcantly enhanced beam de- concrete beams, eight without stirrups, and four with shear fectionsanddeformedshear.Furthermore,theuseofGFRP reinforcement, had been tested by Aguilar et al. [16]. Te compressivestrengthofconcretevariedfrom48to105MPa. stirrups rather than steel stirrups resulted in a signifcant number of small, inclined cracks that covered roughly two- Teywantedtoknowifhigh-strengthconcretecouldusethe minimum and maximum shear reinforcement levels in- thirdsofthespan.Michael[12]releasedanarticledescribing a thorough experimental study to identify the critical dicated in the AASHTO LRFD 14 standards and the ACI Advances in Civil Engineering 3 Table 1: Mix proportions. Code 318-14. Tey came to the conclusion that both AASHTO LRFD and ACI 318’s conservatism had di- Types A B C D minished as the amount of shear reinforcement increased. Cement (kg/m ) 400 500 500 500 Ahmad et al.’s [17] investigation of moment redistribution Silika fume (kg/m ) — — 50 55 behavior under fexural and shear stresses in continuous 3 Sand (kg/m ) 900 904 900 840 concrete beams reinforced with glass fber-reinforced Gravel (kg/m ) 791 931 875 830 polymer (GFRP). Te analysis system (ANSYS) was used HRWRA (kg/m ) — 2.3 6.875 7.5 to generate a fnite element model. Te predictive shear Water (kg/m ) 170 190 160 125 capabilities of the analytical model, the produced fnite el- (w/cm) 0.425 0.38 0.291 0.23 f (MPa) 63.0 78.8 85.9 92.0 ement model, and the data from the literature were all compared. Tis study demonstrated the efectiveness of ANSYS software as a tool for simulating GFRP re- inforcement.Itwasfoundthattheresultsoftheexperiments and the fnite element analysis were in perfect accord. As was previously mentioned, a variety of factors afect how strong shear beams made of high-strength reinforced concreteare.Itischallengingtoanalyzeonecomponentand isolate it from other factors since the impacts of diferent factors interact with one another. Tere aremany studies on simply supported beams, but fewer studies than simply supported ones cover continuous beams. Terefore, the main objective of this study is to determine the efect of continuity on the shear strength of statically 0.1 1 10 indeterminate beams. Figure 2: Grading of fne aggregate with ASTM C33 limits [19]. 2. Objectives of the Study [19] limits, crushed stone with 12.5mm maximum size, the (1) To measure the shear strength of continuous beams grading conformed ASTM C33 [19] specifcations, shown in made of high-strength reinforced concrete without Figure3,andordinarydrinkingtapwaterwereused.Also,to web reinforcement achieve the workability and strength of concrete, a water (2) To study how the a/d ratio and compressive strength reducing admixture, Sika ViscoCrete 5930L super plasti- f afect the shear strength of high-strength rein- cizer, was needed to make the concrete mix workable, in forced concrete beams without stirrups when sub- addition to the Silica fume. Finally, deformed steel bars with jected to a concentrated loads nominal diameters of 20mm and 538MPa yield strength were used as fexural reinforcements and 8mm with 3. Methodology 520MPa yield strength were used for shear reinforcements, whose properties shown in Table 2. Tofulflltheabove-givenobjectives,aresearchprogramthat includes experimental and numerical phases is proposed. Te experimental phase consists of casting and testing 8 4.2. Beam Details. Te variables are concrete compressive concrete beams continuously over two spans. Also, the strength and shear span to efective depth ratio. All the comparison made between the ultimate shear strength ac- beams have the same cross-section (200mm width and quired from test data with values calculated from ACI and 300mm height) and longitudinal reinforcement ratio other researchers’ predictions. (3 ∅20mm). Beam details are explained in the Table 3. Te specimens were divided into four groups A, B, C, and D according to their concrete compressive strengths. In Fig- 4. Experimental Program ures 4 and 5 reinforcement details were explained. All the 4.1. Materials. To reach the required mix design of high- beams were designed so that failure will occur due to shear. strength concrete mixtures, instructions and directions of Also,theyweresochosenthattheydonotfailintheexterior ACI 211.4R [18] and ACI 363.2R [2] guides have been support regions. followed. To reach the required concrete strengths, four types of mixes were used. Tese mixes were obtained after conducting more than thirty trials. Te mixed proportions 4.3. Mechanical Properties of Concrete. Figure 6 show are summarized in Table 1. curves of stress-strain diagrams. To obtain Compressive Te selection of the raw components for concrete had Strength f three 150 ×300mm cylinders were taken been controlled by ASTM regulations. Ordinary Portland according to ASTM C 39/C 39M [20]. Tree cement, locally manufactured at the Tasluja factory in 100 ×100 ×500mm prisms were taken in accordance Sulaimani,NorthIraq,locallynaturalsandfromriver,whose with ASTM C78/C78M [21] utilizing simple beams with propertiesshowninFigure2,whichconformstoASTMC33 third-point stress in order to obtain the modulus of 4 Advances in Civil Engineering 120 100 0 500 1000 1500 2000 2500 3000 Microstrain Type A Type C 1 10 100 Type B Type D Figure 3: Grading of course aggregate with ASTM C33 limits [19]. Figure 6: Stress-strain curves. Table 2: Properties of the reinforcing steel bars. 4.4. Instruments. After the preparation of the molds using Steel bar Diameter (mm) f (MPa) f (MPa) Types of use y u plywood sheets, the next stage began with the construction 8 7.68 317 520 Stirrups of the cage, by assembling the main reinforcement bars with Main the stirrups as shown in Figure 7, and they were explained 20 19.72 538 680 reinforcement previously in the fgures and tables. Ten, the strain gauges were fxed to the predetermined location on the re- inforcements using glue. After that the strain gauges were covered with special tape, made for electrical joints, to Table 3: Details of specimens. protect their moisture, impact, or damage during casting. Dimensions Finally, the cage was placed inside the plywood mold after Longitudinal (mm) Groups Beam a/d f (MPa) c brushing inside with oil to make the removal of the forms reinforcement B H a easy after casting the beams. Casting was started along the length of the beams and 11 200 300 650 2.41 3∅20mm A 63.0 21 200 300 900 3.33 3∅20mm was flled in two layers each layer was compacted using an internalvibrator.Teuppersurfaceofthemoldswasleveled 11 200 300 650 2.41 3∅20mm B 78.8 with a steel trowel. Tis process was continued until the 21 200 300 900 3.33 3∅20mm casting of the group was completed. Side by side of this 11 200 300 650 2.41 3∅20mm C 85.9 process, nine cylinders (150∗300) mm and three prisms 21 200 300 900 3.33 3∅20mm (100∗100∗500) mm were cast to obtain compressive 11 200 300 650 2.41 3∅20mm D 92.0 strength, splitting tensile strength, modulus of rupture, and 21 200 300 900 3.33 3∅20mm modulus of elasticity. After 24hours, the sides of the molds andcontrolspecimenswereremoved.Tecuringprocessfor Ф 8 mm @ 80 mm C/C 3 Ф 20 mm 140 mm the beams and the control specimens started and all of them were covered with wet burlap and kept wet for more than 90days. Te beams were tested under a universal machine with a hydraulic jack of 2000kN (200ton), 700bar, and 3 Ф 20 mm 500 mm 650 mm maximum capacity as explained in Figures 8 and 9. Figure 4: Reinforcement detail for beam 1. To obtain reactions and loads, load cells of type S8920 were placed beneath the exterior reaction and loaded. As shown in Figure 10, these load cells were manufactured by 3 Ф 20 mm 140 mm Ф 8 mm @ 80 mm C/C SEWHACNM. Tree (linear variable displacement trans- ducer)LVDTwereused,thefrstonealongtheinclinedstrut location, the second on the compression fber of the load, 3 Ф 20 mm 500 mm 900 mm and the third one along the compression fber of the middle support. Also, precision electronic strain gauges were used Figure 5: Reinforcement detail for beam 2. along the diagonal strut between the middle support and loading points. For measuring the strain of stirrups and mainreinforcements,precisionelectronicstraingaugeswere rupture. Elasticity modulus were made in accordance used. Te positions of strain gauges were shown in with ASTM C 469/C 469M [22]. Finally, to determine Figures 11–14. splitting tensile strength, three additional 100 ×200mm A linear variable displacement transducer (LVDT) was cylinders were obtained in compliance with ASTM C used under the point load to measure the defection that 496/C 496M [23]. Table 4 presents the results for the occurred during the loading process. And, a data logger of control specimens. Stress (MPa) Advances in Civil Engineering 5 Table 4: Test results of the control specimens. 2 2 2 2 Types f (N/mm ) f (N/mm ) f (N/mm ) E (N/mm ) c r sp c strain gauge 1 strain gauge 1 A 63 5.1 4.0 33255 B 78.8 5.9 4.7 36371 500 mm a a 500 mm C 85.9 6.2 5.0 37670 Figure 11: Placement of concrete electronic strain gauges. D 92 6.5 5.2 38752 Figure 7: Reinforcement cages. Load Load Figure 12: Linear variable displacement transducer (LVDT). 500 mm aa 500 mm Figure 8: Test arrangement of typical beam specimen. Figure 13: Placement of steel strain gauges. Figure 9: Beam specimen under loading machine. Figure 14: Electronic steel strain gauges. leftsupporttodeterminethesupportreactionsinadditionto total load accurately to determine the shear force in each span. A wide fange steel beam was used to divide the hy- draulic jack force into two-point loads. A thick plate (200∗60 ∗20) mm was used to prevent the local bearing failure at the point of load application. Te test was started under force control with a specifc loadincreaseof10kNto15kNoncetheprecedingprocesses hadbeenfnished.Avisualinspectionwasconductedateach load increase, and any cracks were marked. Te crack propagation was examined at each load increment, and the location, load size, and newly formed cracks were noted and Figure 10: Load cells. documented.Teweightwasincreasedincrementallyduring this procedure until the beam fnally failed. the type Windmill 851 was used to collect all the data from 5. Test Results and Discussions the strain gauges, LVDTs, and loads cells. 5.1. Crack Propagation and Failure Load. Atbeginningofthe 4.5. Test Procedure. All the beams were tested in a loading loadingprocess,withloads,allthebeamsbehavedelastically. frame through one hydraulic jack of 2000kN capacity, with Te stresses were small and below proportional limits, three support reactions. Load cells had been put beneath the consequently, the beams were free of cracks and the 6 Advances in Civil Engineering Table 5: Failure load of the beams. defections were small. Te frst crack was vertical, due to fexural stress. After the formation of the frst crack, they Moment at Failure load Exterior reaction were followed by more similar fexural cracks. Further new Beams interior support (kN) (kN) fexural cracks formed in both the hogging and sagging (kN·m) fexural regions as the load was increased. With increasing A11 356.1 157.05 50.8575 the loads, the fexural cracks near the supports propagated A21 264.55 114.08 78.383 diagonally toward the loading point. Te cracks grew wider B11 433.099 192.08 60.6234 and propagated toward each other. Before the beams fail, B21 292.641 144.62 60.909 a diagonal crack is initiated at the midheight of the beam. C11 471.6 191.74 86.039 C21 325.74 160.59 68.34 Before the failure, as the load increased, the number of D11 542.2 231.21 86.5385 cracksdidnotincrease,butthedepthandwidthofthecracks D21 356.258 178.09 71.3062 had increased. Te failure loads of the beams are shown in Table 5. Te crack pattern of beams is shown in Figures15–18forcastinggroupsA,B,C,andD,respectively. 5.2. Efect of Compressive Strength on Load-Defection Be- havior and Ultimate Load. Te relation between defection andloadis showninFigures19 and20.Ingeneral,whenthe concrete compression strength increases, the ultimate load of failure of the beams increases too. Te experimental Figure 15: Crack pattern for beam of group A. resultsshowedthatfor beamseries1,beamswithshearspan to depth ratio (a/d) 2.41 when the compression of the concrete increased from 63MPa to 78.8MPa the ultimate load increased 121.6%. By changing the compressive strength from 63MPa to 85.9MPa the ultimate load in- creased132.4%.Whilethechangingofcompressivestrength from 63MPa to 92MPa lead to an increase in the ultimate load by 1.523%. For shear span to depth ratio (a/d) 3.33, beam series 2, when the compressive strength increased Figure 16: Crack pattern for beam of group B. 1.25% as well as the ultimate load increased 1.106%. Te increase in concrete strength of 136.4% was followed by the increase in the ultimate load of the beam by 123.1%. Also, raising the compressive strength by 146% was reasoned to increase the ultimate load by 134.7%. In contrast to the ultimate load, it was found that with increasing concrete compressive strength the defection response was not in the same attitude. In some groups, we observed that with increasing concrete strength displace- Figure 17: Crack pattern for beam of group C. ment decreases, but not in a constant proportion while in some other groups increasing compressive strength caused to increase in the defection of the beam. We noted that the load-defection curves could be divided into two distinct stages, precracking and postcracking. In the frst stage, the curvewasalmostlinear.Afterformationofthecrackscauses a reduction in the beam stifness and leads to a changing slope of the curve. Also, it was observed that when the compressivestrengthoftheconcretewasincreasedtheslope Figure 18: Crack pattern for beam of group D. of the frst stage of the curve, precrack, became steeper. 5.3. Efect of Shear Span to Efective Depth Ratio on Load- efective depth ratios (a/d) 2.41 and 3.33. Te results of the Defection Behavior and Ultimate Load. Te shear span to tested beams showed that for beams with compressive efective depth ratio is one of the most essential aspects strength of concrete 63MPa, changing a/d from 2.41 to 3.33 afecting the beam’s resistance and behavior. Te infuence the ultimate load decreased from 356.1kN to 264.55kN, of the force moment increases as the distance between the 74.3%, as shown in Figure 21. For beams, with concrete load and the support increases, and in the presence of the compressive strength of 78.8, MPa changing a/d led to force moment, the fractures in the section expand and the adecreaseintheultimateloadby67.57%,from433.1MPato efective depth of the section falls, reducing the section’s 292.64MPa, as shown in Figure 22. Beams of type C, with resistance to shear. In this study, we got two shear span to concrete compressive strength of 85.9MPa, changing in Advances in Civil Engineering 7 600 600 0 2468 Deflection (mm) A11 B11 C11 D11 A11 C11 B11 D11 Figure 19: Load-defection curve and ultimate load for beam 1. 0 2468 10 Deflection (mm) A21 B21 C21 D21 A21 C21 B21 D21 Figure 20: Load-defection curve and ultimate load for beam 2. 􏽱�� 􏽱�� shear span to efective depth ratio reduced the ultimate load V d ′ ′ V � 0.16 f + 17 ρ b dbut≤0.29 f b d, 􏼢 􏼠 􏼡􏼣 69.07%, from 471.6MPa to 325.74%, as shown in Figure 23. c c w w c w Te last group was beams of type D, with concrete com- (1) pressive strength of 92MPa. When the aspect ratio, a/d, changed the ultimate load changed too, from 542.2MPa to where V ; Nominal shear strength provided by concrete, N 356.26MPa, 65.71%, as shown in Figure 24. f ; Compressive strength of Concrete, N/mm , ρ ; Longi- c w It is commonly known that the defection grew along tudinal fexural reinforcement ratio, A /b d, V ; Shear force s w u withthespan.Temomentofforce increasesasthedistance at the section considered, N, M ; Moment at the section between the supports increases, increasing the defection as considered, N·mm, b ; Web width, mm, d; and Efective a consequence. We came to the conclusion that raising the depth, mm aspect ratio, a/d, produced an increase in the defection ACI stated that V d/M shall not be greater than 1.0. under the point load after examining the curves of the re- Table 6 presents the calculated shear strength versus lationship between load and defection of the tested beams. tested shear. Tese increases were varied rather than consistent. 6.2. Te Equation Proposed by Sudheer et al. for Shear Pre- 6. Comparing Test Results with diction [25]. In 2010, Sudheer et al. developed the linear Other Provisions regression equation in power series to calculate the shear resistanceofhigh-strengthconcretebeamswhileaccounting Inthisarticle,theresultsofthetestsarecomparedtotheACI for the concrete’s tensile strength, fexural reinforcement, code, with two diferent researcher approaches presented. and the (a/d) ratio: TeACI318M-19equationforcalculatingtheshearstrength provided by concrete for nonprestressed members Te 0.8 f ρ modifed Zsutty equation and the equation proposed by (2) V � 32 􏼠 􏼡 b d, c w Sdheer et al. were compared. (a/d) where V , Shear strength provided by concrete, N, f , c t 6.1. ACI 318M Equation for Shear Prediction. For member Tensile strength of concrete, N/mm , a/d, Shear span to subjected to shear and fexure ACI 318M-14 proposed the depth ratio. ρ Longitudinal fexural main reinforcement following equation [24]: ratio, and b , d Web width, efective depth, mm Force (kN) Force (kN) Force (kN) Force (kN) 8 Advances in Civil Engineering 0 2468 Deflection (mm) A11 A21 A11 A21 Figure 21: Load-defection curve and ultimate load for beams A11 and A21. 400 500 0 2468 10 Deflection (mm) B11 B21 B11 B21 Figure 22: Load-defection curve and ultimate load for beams B11 and B21. 0 2468 Deflection (mm) 200 C11 C21 C11 C21 Figure 23: Load-defection curve and ultimate load for beams C11 and C21. 0 2468 Deflection (mm) D11 D21 D11 D21 Figure 24: Load-defection curve and ultimate load for beams D11 and D21. Force (kN) Force (kN) Force (kN) Force (kN) Force (kN) Force (kN) Force (kN) Force (kN) Advances in Civil Engineering 9 Table 6: Test predicted shear result based on ACI code. V V c c ′ ′ Beam f f ρ V d/M b d V /V c w ACI Test ACI tested A11 0.0056 1 200 270 73718.7 356100 0.20701678 A21 0.0056 0.518312644 200 270 71242.42 264550 0.2692966 B11 0.0056 1 200 270 81837.53 433099 0.18895802 78.8 B21 0.0056 0.656154848 200 270 80069.89 292641 0.27361132 C11 0.0056 0.878231965 200 270 84592.28 471600 0.17937295 85.9 C21 0.0056 0.652480246 200 270 83431.74 325740 0.25612985 D11 0.0056 0.970288369 200 270 87860.03 542200 0.16204358 D21 0.0056 0.674630818 200 270 86340.11 356258 0.24235276 Table 7: Test and predicted shear result based on Sudheer et al. equation. Beam f ρ a/d V Sudheer V tested V /V c c t Sudheer Test A11 0.0056 2.4 41074.6 356100 0.11534564 A21 0.0056 3.33 31607.3 264550 0.11947554 B11 0.0056 4.26 29528.7 433099 0.06818009 4.7 B21 0.0056 5.19 25213.8 292641 0.08615954 C11 0.0056 6.12 23220.4 471600 0.04923741 C21 0.0056 7.05 20735.7 325740 0.06365724 D11 0.0056 7.98 19377.4 542200 0.03573839 5.2 D21 0.0056 8.91 17741.7 356258 0.04980008 Tepredictedresultsbasedonequation(2)arepresented a decrease the defection. Also, when the concrete inTable7,alongwithacomparisonofthepredictedandtest became stronger, the ductility reduced and the results. concrete became more brittle. Te V /V values measure the equation’s predicted tested (3) In beams with a/d �2.41, Increasing compressive conservation,andifthisnumberislessthan1.0,theequation strength by 125% caused the ultimate to increase is on the safe side because it overestimates the true value of by 121%. And, ultimate load 132% because of the beam. Te following broad conclusions can be drawn increasing compressive strength 136%. Also, this based on the information in these tables: increase continued and reached 152% when compressive strength increased by 146%. Also, (1) FortheACIequation,when a/dincreased,thevalues when a/d �3.33, the increase in ultimate load was became less conservative; this may be because of the 111%, 123%, and 135% when the compressive efect of the fexural moment strength increased 125%, 136, and 146%, (2) Te equation proposed by Sudheer et al. was more respectively. conservative, and the predicted values decreased as (4) When a/d increased, the defection of the beams the tensile strength of concrete increased increased, too. (5) For concrete strength of 63MPa, increasing a/ 7. Conclusions d from 2.41 to 3.33 caused to decrease in the ulti- mate strength of 74%, and defection increased by Te results of a study on the strength and behavior of 137%. reinforced high-strength continuous concrete beams were (6) For beams group B (78.8MPa) changing a/d led to summarizedinthispaper.Tefollowingconclusionsmaybe a decrease in ultimate load of 68% and increased taken from the scope of this study: defection by 143%. (1) As the compressive strength of concrete was in- (7) For beams group C (85.9MPa) the ultimate load creased, the concrete became more fragile and the decreased 69% and defection increased 152% be- correspondingstraindecreased.And,increasingthe cause of changing a/d from 2.41 to 3.33. compressive strength led to an increase in the ul- (8) For beams group D (92MPa) the ultimate load timate load of the beams. decreased 66% and defection increased 123%. (2) Te increase of concrete compressive strength (9) Te values for the ACI equation became less con- caused a slight decrease in the defection of the servative as a/d increased; the fexural moment beams because the increasing concrete strength might have had something to do with this. caused to increase in stifness and this led to 10 Advances in Civil Engineering [9] J. O. Brian, N. M. Raphael, N. Timothy, and A. G. Zachary, (10) Te values predicted by Sudheer et al.’s equation “Shear performance of concrete beams with a maximum size decreased as concrete’s tensile strength increased, ofrecycledconcreteaggregate,” Advances in Materials Science and they were more conservative. and Engineering,vol.2022,ArticleID6804155,17pages,2022. [10] J. J. Rodriguez, A. C. Bianchini, I. M. Viest, and E. K. Clyde, 8. Further Study Recommendations “Shear Strength of two-span continuous reinforced concrete beams,” Journal of the American Concrete Institute, vol. 30, Te following suggestions may be useful for further work: no. 10, pp. 1089–1130, 1959. [11] N. F. Grace, A. K. Soliman, G. Abdel-Sayed, and K. R. Saleh, (1) Experimental and analytical studies about the shear “Behavior and ductility of simple and continuous FRP behavior of continuous beams with diferent cross- reinforced beams,” Journal of Composites for Construction, sections, such as L-shaped and T-shaped sections. vol. 2, no. 4, pp. 186–194, 1998. (2) Inthisstudy,specimensweretestedunderone-point [12] P. Michael, “Collins and daniel Kuchma,” How Safe Are Our loads in each span. It is better to test a series of Large, Lightly Reinforced Concrete Beams, Slabs, and Foot- continuous beams under diferent loading arrange- ings?” ACI Structural Journal,vol.96,no.4,pp.482–491,1999. [13] C. Michael McCarty, “Behavior of two-span continuous ments than a one-point load in each span. reinforced concrete beams,” M. Sc. Tesis, Russ College of (3) Experimental and analytical study about the efect of EngineeringandTechnologyofOhioUniversity,Athens,OH, unsymmetricalspansonshearstrengthofreinforced USA, 2008. high-strength continuous beams. [14] J. Motamed, “Monolithic to external column joints in rein- forced concrete,” Ph. D. thesis, University of Westminster, UK, London, 2010. Data Availability [15] T.C.Nwofor,S.Sule,andD.B.Eme,“Acomparativestudyof BS8110 and Eurocode2 standards for design of a continuous Te data used to support the study are available from the reinforced Concrete Beam,” International Journal of Civil corresponding author upon request. Engineering and Technology, vol. 6, no. 5, pp. 76–84, 2015. [16] G. Aguilar, S. Villamizar, and J. A. Ramirez, “Evaluation of Conflicts of Interest shear reinforcement design limits in high-strength concrete beams,” ACI Structural Journal Concrete Beams, vol. 115, Te authors declare that they have no conficts of interest. no. 2, 2018. [17] H. Ahmad, A. Elnemrm, N. Ali, Q. Hussain, K. Chaiyasarn, and P. Joyklad, “Finite element analysis of glass fber- Acknowledgments reinforced polymer-(GFRP) reinforced continuous concrete beams,” Polymers, vol. 13, no. 24, p. 4468, 2021 Dec 20. TestudywassupportedbyUniversityofSulaimani,College [18] Aci 211 4R-11, “Guide for selecting proportions for high- of Engineering, Sulaymaniyah, Kurdistan Region, Iraq. strength concrete using portland cement and other cemen- titiousmaterials,”ReportedbyACICommittee211,American References Concrete Institute, Michigan, MG, USA, 2011. [19] AstmDesignationC33/C33M–13, Standard Specifcation for [1] Aci committee 363R-10, “Report on high strength concrete,” Concrete Aggregates, Annual Book of ASTM Standard, West Reported by ACI Committee 363, American Concrete In- Conshohocken, PA, USA, 2015. stitute, Michigan, MG USA, 2010. [20] AstmDesignationC39/C39M–03, Standard Test Method for [2] Aci committee 363.2R-11, “Guide to quality control and Compressive Strength of Cylindrical Specimens, Annual Book assurance of high strength concrete,” Reported by ACI of ASTM Standard, West Conshohocken, PA, USA, 2004. Committee 363, American Concrete Institute, Michigan, MG [21] AstmDesignationC78/C78M–15, Standard Test Method for USA, 2011. Flexural Strength of Concrete (Using Simple Beam with Tird- [3] D.Darwin,C.W.Dolan,andA.H.Nilson, Design of Concrete Point Loading), Annual Book of ASTM Standard, West Structures, McGraw-Hill Book Company, New York, NY, Conshohocken, PA, USA, 2015. USA, 2016. [22] Astm Designation C 469/C 469M – 14, Standard Test Method [4] J. G. M. van Mier, “Failure of concrete under uniaxial for Static Modulus of Elasticity and Poisson’s Ratio of Concrete compression: an over view,” Fracture Mechanics Of Concrete in Compression, Annual Book of ASTM Standard, West Structures, vol. 2, 1998. Conshohocken, PA, USA, 2015. [5] Q. Deng, Y. Wei-Jian, and T. Fu-Jian, “Efect of coarse ag- [23] Astm Designation C 496/C 496M – 11, Standard Test Method gregate size on shear behavior of beams without shear re- for Splitting Tensile Strength of Cylindrical Concrete Specimens, inforcement,” ACI Structural Journal, vol. 114, no. 5, Annual Book of ASTM Standard, West Conshohocken, PA, pp. 1131–1142, 2017. USA, 2015. [6] A. Ghafar, J. Afzal, and U. R. Habib, “Development of shear [24] Aci 318M-14, Building Code Requirements for Structural capacity Equations for rectangular reinforced concrete Concrete (ACI 318M-14) an ACI Standard and Commentary, beams,” Journal of Engineering and Applied Science, vol. 6, American Concrete Institute, Michigan, MG, USA, 2014. pp. 1–8, 2010. [25] L. Sudheer Reddy, N. V. Ramana Rao, and T. D. Gunneswara [7] ACI-ASCE committee 445 on shear and torsion, “Recent Rao, “Shear resistance of high strength concrete beams approaches to shear design of structural concrete,” Journal of without shear reinforcement,” International Journal of Civil Structural Engineering, vol. 124, no. 12, pp. 1375–1417, 1998. and Structural Engineering, vol. 1, no. 1, pp. 101–113, 2010. [8] G. N. J. Kani, “Basic Facts Concerning Shear Failure,” ACI Journal, vol. 63, pp. 675–692, 1966.

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