STRUCTURAL BEHAVIOR OF HIGHLY STRENGTH REINFORCED CONCRETE BEAMS WITH SEGMENTAL ARCHED BOTTOM

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1 International Journal of Civil Engineering and Technology (IJCIET) Volume 9, Issue 13, December 2018, pp , Article ID: IJCIET_09_13_072 Available online at aeme.com/ijciet/issues.asp?jtype=ijciet&vtype= =9&IType=13 ISSN Print: and ISSN Online: IAEME Publication Scopus Indexed STRUCTURAL BEHAVIOR OF HIGHLY STRENGTH REINFORCED CONCRETE BEAMS WITH SEGMENTAL ARCHED BOTTOM Maryam Hameed Naser Al-Mamoori Civil Engineering Department, Al-Mustaqbal University college Prof. Dr. Nameer A. Alwash College of Engineering, Civil Engineering Department, University of Babylon ABSTRACT The present study includes an experimental and numerical investigations for the behavior and the load carrying capacity of simply supported beam with segmental arch bottom of high strength concrete (HSC) subjected to static loading condition. The goals were to evaluate the effect of arch dimensions on the behavior of beam with the same volume of concrete and amount of steel reinforcement and to find the optimum ratio of the arch length to beam span for the maximum load capacity as well as to validate the numerical results taken from the finite element model. The experimental program consists of testing four simply supported beams containing arch at the bottom face and tested under two-point load. The beams are different spans of arch (1180 mm, 900 mm, 740 mm, and 600 mm) with the same volume of concrete and amount of steel reinforcement. Among conclusions of this work, it is concluded that the increase of the arch length to beam span ratio increased the ultimate load capacity to more than 60 %. FEM appears efficient and gives good accuracy through comparison with the experimental results where the maximum difference in the ultimate load value was less than 4%. Keywords: High Strength Concrete (HSC), Segmental Arch Beam, Non-Prismatic Beam. Cite this Article: Maryam Hameed Naser Al-Mamoori and Dr. Nameer A. Alwash, Structural Behavior of Highly Strength Reinforced Concrete Beams with Segmental Arched Bottom, International Journal of Civil Engineering and Technology (IJCIET) 9(13), 2018, pp et/issues.asp?jtype=ijciet&vtype=9&itype e=

2 Maryam Hameed Naser Al-Mamoori and Dr. Nameer A. Alwash 1. INTRODUCTION In the past, the arch represents one of the few structural systems which make it possible to cover large spans. Nowadays, the same importance is presented especially in construction of bridges and arched structures which are constructed in different shapes and from various materials such as brick, steel, reinforced concrete, ferro cement and timber. The main objective of the arch is to support a load more than straight beam. This may be attributed to the stiffening behavior of the membrane action which leads to reduce the bending moment [1]. This situation is consistent with concrete material, which is relatively low in carrying tension and shear stresses but is able to withstand compressive stress. Numerous specialists introduced experimental and analytical investigations of reinforced concrete arches. These examinations were initiated in 1960 by Jain [2]. Also, the curved beam behavior under static load over various cross-sectional forms and special requirements have been studied by many authors through many experimental programs such as; Al-Thabhawee (2012) [3], and Hamza (2013) [4], most of them focus on the use of normal weight concrete (NWC); but although, there are several studies on high strength concrete (HSC) such as those carried out by Hameed (2010) [5], and Annadurai, A. & Ravichandran A. (2014) [6]. Extensive experimental and analytical studies have been performed to investigate the behaviors of non-prismatic beam under different loading methods which are widely used in numerous engineering structures such ashans et.al in 2012 [7], In 2013, Rojas [8], Orr et al. (2014) [9], and Nabbat (2015) [10,11]. However, there is no study found yet on the behavior of reinforced concrete beams with arched bottom using high strength concrete which will be studied in the current research. 2. EXPERIMENTAL PROGRAM 2.1. Description of Test Specimens This study includes casting four simply supported beams of segmental arch at bottom face and were tested under two-point load. The width (b) for all beams was 150 mm, the beams have total length (Lt) of 1500 mm, the effective span (L) was 1350 mm, and the shear span (a) was 450 mm. Also, the overall depth at each beam end (hmax=250 mm) and then reduced at the centre according to area and span of the arch as shown in Figure (1). Figure 1 Geometry, Loading Scheme and Details of Reinforcement of Tested Specimens Each beam was fabricated and tested under static load condition with the same volume of concrete and amount of steel reinforcement but, with different span of arch (1180 mm, 900 mm, 740 mm, and 600 mm). All specimens are identified in Table (1) editor@iaeme.com

3 Structural Behavior of Highly Strength Reinforced Concrete Beams with Segmental Arched Bottom Sample Name Identification S1 Beam containing Segmental arch with arch span (Lc = 1.18 m) S2 Beam containing Segmental arch with arch span (Lc = 0.90 m) S3 Beam containing Segmental arch with arch span (Lc = 0.74 m) S4 Beam containing Segmental arch with arch span (Lc = 0.60 m) Where: S: Segmental arch, 1, 2, 3, & 4: refer to span of arch (1180 mm, 900 mm, 740 mm, and 600 mm) respectively. To achieve the same volume of concrete, all specimens have the same area of arch. V total area of sectionarea of arch:width of beam V area of arch:0.15 let,area of arch 0.06 m " )constant+ The segmental arch is made up of part of a circle with angle less than 180 degrees as shown in Figure (2). ( " # $%&' 2 )*sin*+ * 2 sin,-. /0 2 ( 2 ) Table 1 Identification of The Specimens ( " )/0 2+ " 7)(80+ " ( )/0/2+" 780 " 280 Where: Lc: Span of arch yc: Height of arch R: Radius of segment circle depends on (Lc & yc) θ: Angle of segment circle Aarch: Area of the arch L: Beam span Figure 2 Segmental Arch Geometry As stated before, this research included four specimens with different span of arch (1180 mm, 900 mm, 740 mm, and 600 mm) as shown in Table (2) and Figure (3). Table2 Details of Specimen of Segmental Arch Specimen Lc (m) yc (m) Lc/L ratio R (m) θ (degree) θ (radian) Aarch (m2) S ππ 0.06 S ππ 0.06 S ππ 0.06 S ππ editor@iaeme.com

4 Maryam Hameed Naser Al-Mamoori and Dr. Nameer A. Alwash Figure 3 Specimens of Segmental Arch 2.2. Material Properties Highly strength concrete is obtained by selecting suitable materials, good quality control and proportioning. The material must be conforming to ACI committee 363R, 1997 requirements. Three different diameter of reinforcement were tested ( 12, 10, and 6). Bar size of (Ø12 mm, Ø10 mm) Ukrainian organize were used as longitudinal reinforcement, and bars of size (Ø6 mm) Ukrainian organize were used as lateral reinforcement (closed stirrups). Ordinary Portland Cement known as KAR Cement was used in the present study. Natural sand from Al-Akhaidur region in Iraq with maximum size of (4.75 mm) and fineness modulus of (2.94) was used. Natural crushed gravel of maximum size 19 mm was used in this work. It was selectedfrom Al-Nebai region. Also, Silica fume and superplasticizers are used to achieve the high workability needed to produce High-Strength Concrete (HSC). The superplasticizers used in this study was of type SikaViscocrete Mixing, Casting, Curing and Concrete Testing of Specimens The mixing is carried out in drum laboratory mixer with a capacity of 0.04 m3. Therefore, for each specimen and corresponding cubes, cylinders, and prisms, two batches were used. HSC was used to cast allbeams. The mix was by weight at 1:1.25:2.03:0.31 for cementitious material, sand, gravel and water ratios respectively. Figure 4 Casting and Curing Process Moulds for flexural strength testing were prepared with internal dimensions of 150 mm width, 1500 mm length and, variable height along length of the beam. four beam samples editor@iaeme.com

5 Structural Behavior of Highly Strength Reinforced Concrete Beams with Segmental Arched Bottom were cast and cured under laboratory conditions at the Civil Engineeringg Department in the University of Babylon. Also, three standard cubes ( ) mmm for Compressive Strength Test, three standard cylinders ( ) mm for Splitting Tensilee Strength Test and three prisms ( ) mm for Modulus of Rapture Test were cast from the concrete of each beam specimens. After the water curing period, the beam models were painted by white emulsion to ensure clear appearance of crack growth during the test as described in Figure (4). 3. EXPERIMENTAL RESULTS AND DISCUSSION 3.1. Mechanical Properties Table (3) explainsthe mechanical properties of concrete. Each value in this Table is the average of three samples. Table 3 Mechanical Properties of Mixing Concrete for All Beams Compressive Tensile Strength MPa Sample Strength )@A Modulus of Elasticity* MPa f sp f r (Ec)GPa C.CD S S S S *ACI 363R-92 ( Ec=3320 f c +6900) 3.2. Cracking Behavior and Ultimate Load During testing, flexural, flexural-shear (diagonal) and splitting cracks were formed as shown in Figure (5). Flexural cracks were observed firstly, while diagonal cracks and splitting cracks developed as loading continued. Figure 5 Recording the Development of Cracks The first flexural cracks in all the beams was between two-point load region occurred randomly on the tension face of the beam. As the load increased, cracks formed along arch at bottom face. Then, the longitudinal cracks formed along the arch toward mid-span. The cracks pattern of each of thesee specimens is described in Table (4) and Figure (6) editor@iaeme.com

6 Maryam Hameed Naser Al-Mamoori and Dr. Nameer A. Alwash Sample Name Table 4 Experimental Results for Servility Requirement First Cracking Load P cr (kn) Location Δ cr (mm) P u (kn) P s (kn) (0.7P u ) Δ s (mm) S cm from mid span S cm from mid span S cm from mid span S cm from mid span Figure 6 Cracks Pattern for Beams with Segmental Arched Bottom at Failure 3.3. Load-Deflection Curves Three dial gages were put one at mid span, one at the point load (225 mm) from the center of the beam and one at the beginning point of the arch. Table (5) shows the ultimate load, type of failure and deflection at mid-span, under point load and start of arch. Table 5 Deflections at Ultimate Load and Type of Failure Ultimate Load Sample Name P u (kn) % decrease in Failure Mode Ultimate load S crushing of concrete and flexural failure S crushing of concrete and flexural failure S crushing of concrete and flexural failure crushing of concrete S and flexural-splitting failure At mid span Deflection Δu (mm) Under point load Beginning of arch editor@iaeme.com

7 Structural Behavior of Highly Strength Reinforced Concrete Beams with Segmental Arched Bottom Figure (7) represent the load deflection curves for the tested specimens. It can be concluded that, decreasing the arch length to beam span ratio reduced the ultimate load capacity (compared with S1) by about 36.94% for S2, 43.44% for S3, and 63.47% for S4. Also a significant decrease in stiffness of beam were noticed when the length span of arch is smaller. The axial force was generated in the arch by the hinge supports and this tends to spread along the arch. Such axial force has more effect when the length of the arch increases. Figure 7 Load Deflection Curves of Beams with Segmental Arch For Figure (8), It is observed that beam (S1) has more stiffness and deflection compared with other beams due to the distribution of stresses on larger length where leads to less intensity of stress. Figure 8Comparison of Load-Mid Span Deflection Curves for Beams The relation between the ultimate load and arch length / beam span ratio is described in Figure (9) editor@iaeme.com

8 Maryam Hameed Naser Al-Mamoori and Dr. Nameer A. Alwash Figure 9 Effect of The Arch Length / Beam span Ratio on The Ultimate Load. 4. NUMERICAL RESULTS AND DISCUSSION 4.1. Description of Specimens in Finite Element This research includes the analysis of beams tested by using a powerful nonlinear finite element method package ABAQUS that provides a relatively acceptable numerical procedure for investigating the behavior of beam containing arch at bottom face using high strength concrete, assuming full bond between concrete and steel reinforced. In the modeling of the concrete, plates support and shaft a three-dimensional eight-node element C3D8 was used, and for reinforcement a three-dimensionain Figure two-node truss element T3D2 was used as shown (10). Figure 10 Details Modeling of Beam Models 4.2. Results of Finite Element Analysis The validity and accuracy of the adopted finite element models by using ABAQUS computer program are studied and checked by analyzing all members that have been studied experimentally in this work. From the load-deflection behavior of all beams it can be noticed that results of experimental work and numerical analysis have three regions, elastic- when the cracks uncracked, elastic-cracked and elas to-plastic, the first region was terminated happen. Also, it is concludedd that the FE results showed rather stiffer structures than the experimental results for all beams as shown in Figure (11) editor@iaeme.com

9 Structural Behavior of Highly Strength Reinforced Concrete Beams with Segmental Arched Bottom Figure 11 Load-Deflection Curve for Beams The deflected shape at ultimate load for S1 to S4 is shown in Figure (12). Figure 12Deformed Shape of for The Tested Beams at Ultimate Load Table (6) shows that the FEM result appears efficient and gives good accuracy by comparison with the experimental results where the maximum difference of the deflection in

10 Maryam Hameed Naser Al-Mamoori and Dr. Nameer A. Alwash ultimate load was less than 7%. Also, it was found that the different between numerical and experimental ultimate load for all beams wasn't more than 4%. Table 6 Comparison Between Experimental and FEM at First Cracking Load, Ultimate Load and Deflections at Mid Span Sample Name First Cracking Load Ultimate Load (kn) Deflection Δu (mm) F AG )KHL F B )KHL F AG )KHL F F B )HIJ F B )KHL Δ AG )HIJ F u ) Exp Δ u ) FEM B )HIJ F AG )HIJ M B )KHL M B )HIJ S S S S CONCLUSIONS Based on the results obtained from the experimental work and finite element analysis, the following conclusions can be stated within the scope of this study: 1. It can be concluded that the increase in the arch length/ beam span ratio increase the ultimate load capacity where it was found when beams with segmental arch, the increase in the ultimate load may reach to more than 60%. 2. Generally, the failure often occurred due to the top chord concrete crushing due to compression stresses. 3. The first cracking load of numerical data showed results less than the experimental data recorded with ratio N OP )QRS N OP )RTU from ( ). 4. It can be concluded that the FE results showed rather stiffer structures than the experimental results for all beams. 5. The FEM model appears efficient and gives good accuracy by comparison with the experimental results where the maximum difference in the deflection at ultimate load was lower than 7%. Also, it was found that the ultimate numerical load for all beams was about 4 % higher than the ultimate experimental load. REFERENCES [1] Yousif R. F., (2006), "Nonlinear Dynamic Analysis of Reinforced Concrete Arch Structures by Finite Element Method" M.Sc. Thesis in civil Engineering, University of Babylon, Iraq. [2] Jain, O.P., (1960),''Ultimate Strength of Reinforced Concrete Arches'' ACI Journal, Vol. 77, No. 6, December, pp [3] Al-Thabhawee, D. W., (2012) ''Nonlinear Analysis for Behavior of R.C. Arch Beams with Opening", M.Sc. Thesis in civil Engineering, University of Babylon. [4] Hamza, B. H., (2013)"Behavior of RC Curved Beams with Openings and Strengthened by CFRP Laminates", Ph.D. Thesis in civil and structural Engineering, University of Basrah. [5] Hameed D. H. (2010), " Mix Design for High Strength Concrete with Silica Fume" M.Sc. Thesis in civil Engineering, University of Babylon, Iraq. [6] Annadurai, A. & Ravichandran A., (Jan. 2014), "Development of Mix Design for High Strength Concrete with Admixtures" Department of Civil Engineering, Sathyabama University Chennai, Volume 10, Issue 5, PP editor@iaeme.com

11 Structural Behavior of Highly Strength Reinforced Concrete Beams with Segmental Arched Bottom [7] Hans I. A, Arturo T, Alejandro. G Behavior of reinforced concrete haunched beams subjected to cyclic shear loading Departmental de Materials, Universidad Autónoma, Engineering Structures 49 (2013) [8] Rojas A. L., (2013) "Mechanical Elements of Rectangular Non-Prismatic Members for Symmetrical Parabolic Haunches Subjected to a Uniformly Distributed Load" Architectural Engineering Technology, Volume 2, Issue 2, , [9] Orr J. J., Ibella T. J., Darbya A. P., Everndena M., Lavab P. and Debruyneb D., (2014) Shear Behavior of Non-Prismatic Steel Reinforced Concrete Beams Department of Architecture and Civil Engineering, University of Bath. [10] Nabbat R. A., (2015), "Flexural and Shear Behavior of Non-Prismatic Reinforced High Strength Concrete Beams with Openings and Strengthened with CFPR Products" M.Sc. Thesis in Civil Engineering, University of Babylon, Iraq. [11] [11] Hassan I. and K.N.Kadhim "Development An Equations For Flow Over Weirs Using MNLR And CFD Simulation Approaches". International Journal of Civil Engineering & Technology (IJCIET), Volume 9, Issue 3, (Feb 2018) editor@iaeme.com