EFFECTS OF SHEAR SPAN-DEPTH RATIO ON THE BEHAVIOR OF HYBRID REINFORCED CONCRETE CONTINUOUS STRAIGHT DEEP BEAM

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 12, December 2018, pp , Article ID: IJCIET_09_12_101 Available online at aeme.com/ijciet/issues.asp?jtype=ijciet&vtype= =9&IType=12 ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed EFFECTS OF SHEAR SPAN-DEPTH RATIO ON THE BEHAVIOR OF HYBRID REINFORCED CONCRETE CONTINUOUS STRAIGHT DEEP BEAM Saja A.S. Al-Sultany Student, College of Engineering/University of Babylon Hayder M.K. Al-Mutairee Asst. Prof. Lecture, College of Engineering/University of Babylon ABSTRACT The main objective of this paper is to study the effects of the shear span-depth ratio a/h on the behavior of hybrid reinforced concrete continuous straight deep beams RCCSDB. The proportions of a/h ratio were (2, 1.75, 1.5, 1.25, 1, and 0.75).The study also includes investigation about the effects of strengthening the RCCSDB by high strength concrete HSC, at top and bottom for all a/h ratios, and the effects of a/h ratio on the ultimate deflection of RCCSDB. Three dimensional nonlinear finite element analyses had been done. The results showed that when the a/h ratio decreases from 2 to 0.75 the ultimate load of RCCSDB increases by 99% and the deflection decreases by98% for the same compressive strength, and the strengthening of RCCSDB by HSC layer from top is better than from bottom. The study proved that the increments in the ultimate load of RCCSDB increased by 2.17%, 14.03%, 11.02%, 17.08%, 33.2%, and 50.8% for a/h 2, 1.75, 1.5, 1.25, 1, and 0.75 respectively, due to strengthening by 25% HSC layer from top. Keywords: Continuous Deep Beam; Deep Beam; Effects of The Shear Span-Depth Ratio; Hybrid Concrete; Cite this Article: Saja A.S. Al-Sultany and Hayder M.K. Al-Mutairee, Effects of Shear Span-Depth Ratio On The Behavior of Hybrid Reinforced Concrete Continuous Straight Deep Beam, International Journal of Civil Engineering and Technology (IJCIET) 9(12), 2018, pp et/issues.asp?jtype=ijciet&vtype=9&itype e= editor@iaeme.com

2 Saja A.S. Al-Sultany and Hayder M.K. Al-Mutairee 1. INTRODUCTION Reinforced concrete RC deep beams are common structural elements. They are characterized as being relatively short and deep, having a small thickness relative to their span or depth. Typical applications of deep beams include transfer girders, pile caps, tanks, folded plates and foundation walls. The influence of section depth on shear behavior of beams was more pronounced on continuous deep beams than simple ones as presented by Yang et. al[1], also they found the size effect was more prominent in beams having concrete strength of 65 MPa than those having concrete strength of 32 MPa. The effects of shear span-to-overall depth ratio (a/h) on the normalized load capacity for normal strength concrete NSC continuous deep beams have been studied by Yang and As hour [2], with different area and spacing of the horizontal and vertical shear reinforcement, and they found that the normalized load capacity commonly decreases with the increases of a/h ratio take from 0.5 to 2 as predicted by both methods the strut and-tie model and mechanism analysis. The behavior and analysis of continuous RC deep beams investigated by Beshara et. al [3], the analysis proved that the smaller a/h ratio given higher load carrying capacity, less deformation, and lower ductility than of higher a/h ratio, and the increasing of concrete compressive strength leads to a more brittle behavior with increased load carrying capacity and stiffness at different levels. In this study deep RC beams with different variables developed the same mode of failure. In 2017 the behavior of hybrid continuous deep beam investigated by Al-Mutairee, and Al-Hamdani [4], [5] they concluded that the HSC as a top layer in the RCCSDB is better than as a bottom layer, and when the thickness of HSC is equal to (25and 50)% of total depth as a top layer for a/h equal to 1.67, an increase in the ultimate flexural strength is obtained and equal to (14 and 21)% respectively, for specimens with web reinforcement, and (39 and 58%) for specimens without web reinforcement, while the ultimate shear strength increased by (17and 34)% for specimens without web reinforcement. As shown all previous investigations and studies did not appear the effects of shear spanto-overall depth ratio on the behavior of hybrid RCCSDB clearly, this effect is very important to achieve best strength and performance of RCCSDB. Therefore, the main objective of this research is to study this effect. Notation Cp α 1, α 2 γ 1, γ 2, γ 3 Ec Es fy ƒʹc ft υ Ԑu Plasticity coefficient Tension-stiffening parameters Shear retention parameters Modulus of elasticity of concrete (MPa) Modulus of elasticity of steel(mpa) Yield strength of steel(mpa) Uniaxial compressive strength of concrete, cylinder test, (MPa) Uniaxial tensile strength of concrete, (MPa) Poisson s ratio Ultimate concrete strain Nonlinear Finite Element Program The computer program coded NFHCBSL (Nonlinear Finite element analysis of Horizontally Curved Beam under Static Load) Fortran90 language presented by Hayder [6] and used by other researches [7], [8], and [9]was adopted and developed to deal with NSC and HSC (hybrid section), in this program20-node is oparametric brick element used to represent the editor@iaeme.com

3 Effects of Shear Span-Depth Ratio On The Behavior of Hybrid Reinforced Concrete Continuous Straight Deep Beam concrete elements while reinforcing bars are idealized as axial members embedded within the concrete elements without any relative displacement between them. Effects of shear span-to-overall depth ratio (a/h) on the behavior of RCCSDB Asix ratios of (a/h) selected were (2,1.75, 1.5, 1.25, 1, and 0.75) to evaluate the behavior of deep beam with different location of HSC and length of deep beams. The properties of materials and the parameters adopted in the analysis are as detailed listed in Table 1, the geometry of beam is as shown in Fig.1. The loads were applied as a non-uniform increments as shown in Table 2. Fig.1: Geometry and Loading Conditions of RCCSDB Table 1 Properties of materials and parameters adopted in the analysis. Materials Properties The compressive strength of concrete (NSC) ƒʹc= 30 MPa (HSC) ƒʹc = 60MPa The yield strength for longitudinal reinforcements (Ø6mm) ƒ yl =480MPa The yield strength for stirrups reinforcements (Ø5 mm) ƒ ys =520 MPa The modulus of elasticity of concrete (NSC)E c =25.74GPa (HSC)E c =32.62GPa The tensile strength of concrete (NSC) ƒ t =1.6 MPa (HSC) ƒ t =2.25MPa Poisson s ratio and ultimate strain of materials Concrete: (NSC ) (HSC) Reinforcement: υ = 0.2, ε u = υ = 0.2,ε u = υ = 0.0, ε u = 0.2 The modulus of elasticity of steel E s = 200 GPa Parameters α 1 =40 α 2 =0.4 γ 1 =10 γ 2 =0.5 γ 3 =0.1 C P =0.3(NSC) C P =0.6(HSC) TOL=0.1% Table 2 The incremental analytical scheme of applying the load of beam Number of Increments The Applied Load P(kN) CONVERGENCE STUDIES The numbers of elements taken from the convergence studies results in each case of a/h ratios were (352, 320, 256, 224, 192, and 160) for a/h equal to (2, 1.75, 1.5, 1.25, 1, and 0.75) respectively. This means that the lower a/h required the lower number of elements. All editor@iaeme.com

4 Saja A.S. Al-Sultany and Hayder M.K. Al-Mutairee convergence studies were adopted for NSC. The following Table 3 and Fig.2 show the reason for the adoption of these elements for each case of a/h by extracting the percentage difference between the last two successive meshes. The curves of convergence study of each beams is shown in Fig.2. In all cases, the mesh contained two elements in the direction of the width and four elements towards through the depth (i.e. 8 elements in each side section, to decrease the band width of stiffness matrix and running time [10,11]). As for the length, the divisions were increased until reached a state of convergence. The types of failure that occurred in most cases wereof crushing of concrete, rupture of the longitudinal, and/or rupture stirrup reinforcement. a/h ratios Table 3 Proportion of convergence, for different a/h ratio. Proportion of convergence 2 the difference between 288 element and 352 element meshes is equal to 0.5% 1.75 the difference between 288 element and 320 element meshes is equal to 1.8% 1.5 the difference between 224 element and 256 element meshes is equal to 1.69% 1.25 the difference between 256 element and 224 element meshes is equal to 1.9% 1 the difference between 224 element and 192 element meshes is equal to 2.08% 0.75 the difference between 192 element and 160 element meshes is equal to 2.08% Fig.2: Convergence Studies Curves editor@iaeme.com

5 Effects of Shear Span-Depth Ratio On The Behavior of Hybrid Reinforced Concrete Continuous Straight Deep Beam The effect of HSC on the ultimate load of RCCSDB for different ratios of a/h The present paragraph illustrate the effects of a/h ratio on the behavior of RCCSDB as well as the effects of strengthening the RCCSDB by HSC for different ratios of a/h. In each case of a/h eight cases of strengthening studied, the results are shown in Fig.3. Table 4 shows the amount of increase in ultimate load at each reinforcement with HSC for all cases of a/h, and shows that when the beam is made up of NSC, the increase in the ultimate load when the variation of a/h from 2 to 0.75 was 35%.Thelower a/h gives the higher increase, while when strengthening the RCCSDB by HSC layer of 25% from top and bottom the increase were 99% and 22% respectively, i.e. the addition of HSC from top gave an increased rate equivalent to four times than the bottom. Similarly, when use 50% HSC from the top, an increase of 95% obtained while for 50% HSC at bottom the increase was 33%. The use of 75% HSC at the top gave an increase of 90% and at bottom gave 33%. The results proved that when a/h decreased the efficiency of strengthening by HSC increased, and the deference between the results of 25% HSC from top and fully HSC decrease. The use of fully HSC gave an increase of 70% in ultimate load. The results illustrated and fixed clearly that when a/h ratio decreases the importance of strengthening of RCCSDB by HSC increased, for example when a/h equal to 2, 0.75 the increases were 24%, 56% respectively for strengthening fully HSC (when compare between the results of fully HSC and fully NSC). From Fig.3, the results showed that the load capacity increase and the deflection decreases when a/h ratio decreases for the same compressive strength, and the strengthening of RCCSDB by HSC layer from top is better than from bottom and these results were identical with the experimental results of Al-Mutairee, and Al-Hamdani [4]. Table 4 proved that the strengthening of fully HSC is the highest, then 75% HSC at top, while the (50 and 25) %HSC were the amount of increase between them is very close. In addition, decreases in mid span deflection can be noticed when the length decreases. Table 4 Effect of a/h ratio on the ultimate load of hybrid RCCSDB Location of HSC a/h ratios Fully NSC %HSC from TOP %HSC from BOTT %HSC from TOP %HSC from BOTT %HSC from TOP %HSC from BOTT Fully HSC editor@iaeme.com

6 Saja A.S. Al-Sultany and Hayder M.K. Al-Mutairee a/h=2 a/h=1.75 a/h=1.5 Fig.3: The effect of Strengthening on Ultimate Load of Hybrid RCCSDB. a/h=1.25 a/h=1 a/h=0.75 Fig.3: Continue. Increment in ultimate load of RCCSDB due to strengthening by HSC at top Due to the strengthening by HSC from the top is better than from the bottom, so will focus on the amount of increment of ultimate load from the top only for all types of strengthening, i.e., fully HSC, 75%, 50% and 25% from top and for different a/h ratios as shown in Fig.4. Fig.4 shows the best a/h was equal to 0.75, because it gives the largest increase in the ultimate load for all types of strengthening. It shows also the amount of increase in ultimate load at each strengthening for all cases of a/h. The results proved that when the ratio of a/h decreases the differences among the ratios of increase of strengthening decreases (i.e. the efficiency of hybrid by 25% from top increases). It is important to note that the results of Table (5) were based on the ultimate load of beam is made up of NSC, and the results were compared with results of RCCSDB strengthening from the top because it gives higher results, which was explained previously. As the strengthening of the RCCSDB by 25% HSC from top gave the optimal strengthening and this phenomenon is identical with practical results achieved by Al- Mutairee, and Al-Hamdani [4], and [5]

7 Effects of Shear Span-Depth Ratio On The Behavior of Hybrid Reinforced Concrete Continuous Straight Deep Beam Fig.4: Effect of Strengthening the RCCSDB by HSC at Top on the Ultimate Load. Table5: Increment in ultimate load from TOP for each a/h ratio. a/h ratios Increment in ultimate load % HSC 75% 50% 25% The effect of deflection From Fig.(3) the results showed that when decreasing a/h ratio for the beams, the deflection was decreased. At load equal to kN, when the beam is made up of fully HSC the decrease in ultimate deflection when the variation of a/h from 2 to 0.75 is 97%. While when strengthening the RCCSDB by HSC layer of 25% from the top the decrease in ultimate deflection was about 98%. Similarly, when use 25% HSC from the bottom the decrement was 96%. This means the effect of strengthening of RCCSDB by HSC layer at top or at bottom is the approximately from side deflection. 3. CONCLUSION According to the presented analytical investigations, the following conclusion can be drawn for RCCSDB: Presence of HSC as a top layer in the RCCSDB is better than as a bottom layer. The deflection at the same load decreased with increased percentage of high strength concrete at any location. The25% HSC at top represent the optimal strengthening for RCCSDB, and the increment were 2.17%, 14.03%, 11.02%, 17.08%, 33.2%, and 50.8% for a/h 2, 1.75, 1.5, 1.25, 1, and 0.75 respectively editor@iaeme.com

8 Saja A.S. Al-Sultany and Hayder M.K. Al-Mutairee When a/h ratio decrease the importance of strengthening of RCCSDB by HSC increased, for example when a/h equal to 2, 0.75 the increments were 24%, 56% respectively for strengthening fully HSC (when compare between the results of fully HSC and fully NSC). When the ratio of a/h decreases the differences among the ratios of increments of strengthening decreases (i.e. the efficiency of hybrid by 25% from top increases). When a/h decreases the ultimate load increased, and this phenomena was more efficient for HSC, where the increments in the ultimate load (when a/h decreases from 2 to 0.75) were 35%, and 70% for NSC and HSC respectively. REFERENCES [1] Yang K-H, Chung H-S, Ashour AF. Influence of section depth on the structural behavior of reinforced concrete continuous deep beams. Magazine of Concrete Research. 2007; 59: [2] Yang KH, Ashour AF. Load Capacity of Reinforced Concrete Continuous Deep Beams. Journal of Structural Engineering. 2008; 134: [3] Beshara F, Shaaban I, Mustafa T. Behavior and Analysis of Reinforced Concrete Continuous Deep Beams. 12 th Arab Structural Engineering Conference2012. [4] Al-Mutairee HM,Al-Hamdani HA. Flexure Behavior of Hybrid Continuous Deep Beam Strengthened by Carbon Fiber Reinforced Polymer. Journal of University of Babylon. 2017;25: [5] Al-Mutairee HM, Al-Hamdani HA. Shear behaviours of hybrid continuous deep beams strengthened with carbon fibre reinforced polymer. IOP Conference Series: Materials Science and Engineering. 2018;433: [6] Hayder M.K. Al-Mutairee, Nonlinear Static and Dynamic Analysis of Horizontally Curved Beams, Ph.DThesis, University of Babylon, [7] Al-Mutairee HM, AbdulAbbas AI. THE ANALYTICAL STUDY OF STRENGTHENING THE HORIZONTALLY CURVED STEEL BEAM WITH CFRP LAMINATES. European Scientific Journal, ESJ. 2015;11. [8] Hayder M. K. Al-Mutairee, Dolfocar A. U. Witwit. Analytical Study of Reinforced Concrete Horizontally Curved Beam of Rectangular Hollow Section. Civil and Environmental Research. Vol.8, No.5, ;131: [9] Hamza BA, Radhi AR, Al-Madhlom Q. Effect of (B/D) ratio on ultimate load capacity for horizontally curved box steel beam under out of plane concentrated load. Engineering Science and Technology, an International Journal [10] Hayder M.K. Al-Mutairee. Optimal systematical nodes numbering technique in the three dimensional analysis of structural elements. Journal of Engineering and Applied Sciences. 2018; [11] Kadhim Naief Kadhim and Ghufran A. (The Geotechnical Maps For Gypsum By Using Gis For Najaf City (Najaf -Iraq) (IJCIET), Volume 7, Issue 44, July-August 2016, pp editor@iaeme.com