International Journal of Advanced Engineering, Management and Science (IJAEMS)
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
Performance Evaluation of RC Deep Beams P. Karthik M.Tech, Civil Department, PRIST University, Tamil Nadu, India
Abstract— Deep beam is a very important structural element in various types of concrete structures such as pile cap, transfer girder, panel beams, foundation walls of rectangular walls of rectangular tanks, bins, shear walls, folded plate of roof structures etc. The inclusion of steel fibers in concrete deep beams resulted in enhanced stiffness and increased spall resistance at all stages of loading up to failure and reduced crack widths. This project work is to investigate influence of Poly propylene fibers in enhancing shear strength in combination with steel fibers. Shear strength of series of Reinforced Cement Concrete (RCC) deep beams with three shear span to effective depth ratios (0.7, 0.8 and 0.9), three span to over all depth ratios (1.5,1.75,2.0), three steel fiber volume fractions (0%,1%,1.25%), two combination of steel and Poly propylene fiber volume fractions ((1.0, 0),(1.0, 1.0))% and three combinations of web reinforcement were evaluated. A total of 21 beams are tested to failure under two point loading. Loads were estimated using ACI code 318-99 method. Analytical results were compared with the experimental results. The test results indicate that the steel fibers in combination with poly propylene fibers have significant influence on the shear strength of a longitudinally reinforced concrete beams. Shear strength increases with increasing steel fiber volume, using combination of steel and poly propylene fiber and decreasing shear span toeffective depth ratio. Steel fibers in combination with Polypropylene fibers can replace the conventional web reinforcement in RCC deep beams I. INTRODUCTION Deep beam can be defined as a beam in which either clear span is equal to or less than four times the overall member depth or concentrated loads are within a distance equal to or less than two times the depth from the face of support (ACI Committee 318, 2008). As the general rule Deep beams are recognized by relatively small values of spanto-depth ratio. Deep beam is a very important structural element in various types of concrete structures such as pile cap, transfer girder, panel beams, foundation walls of rectangular walls of rectangular tanks, bins, shear walls, folded plate of roof structures etc. The inclusion of steel fibers in concrete deep beams resulted in enhanced stiffness and increased spall resistance at all stages of
loading up to failure and reduced crack widths. Most of the properties of fibrous concrete can be used to enhance the behaviour of concrete members reinforced with conventional bar reinforcement. Concrete for various shear span ratio and web reinforcement are investigated. II.
MATERIALS AND METHODS
2.1 INTRODUCTION This chapter deals with the details of the test specimen and the experimental investigation carried out to study the behavior of RC deep beam subjected to two point loading until failure. For any successful investigation, it is essential that the specimens, should have identical properties with regard to the dimension and the strength. This can be achieved by the use of correct formwork, use of good quality materials, and a properly designed mix, adhering to strict quality control during casting and maintaining identical curing condition. Appropriate precautions were taken to achieve the above objective. 2.2 MATERIALS: 2.2.1 Cement Ordinary Portland cement 53 grade with specific gravity of 3.15 was used. 2.2.2 Fine Aggregate The fine aggregate used in this investigation was clean river sand passing through 3.75mm sieve with specific gravity of 2.65 and Fineness modulus of sand 2.25 was used. 2.2.3 Coarse Aggregate Crusher Coarse aggregate of 20mm procured from local crusher with specific gravity is 2.6 and fineness modulus of 6.1 was used. 2.2.4 Water The potable water available in college campus was used for mixing and curing of concrete. The cast specimen was cured in water tank by complete immersion. 2.2.5 Steel fiber Steel fiber used in this investigation was supplied by STEWOLS INDIA (P) Ltd., Nagpur, Maharashtra State, India and their properties are Fiber type : Hooked end type Diameter : 0.45mm Length of fiber : 25mm Aspect ratio : 55.55 Page | 83
International Journal of Advanced Engineering, Management and Science (IJAEMS)
Tensile strength : 1250 MPa Young's modulus : 200GPa Cost : Rs.70/Kg 2.2.6 Polypropylene fiber: Polypropylene fiber used in this investigation RECRON 3S made by Reliance India Ltd., and their properties are such as Type : Micro fibers Length of fiber : 12mm Tensile strength : 690 MPa Young's modulus : 5000 MPa Cost : Rs.600/Kg 2.3 Samples for strength test Iron cube moulds of size 150x150x150 mm and cylinder of 300mm height and 150mm diameter were used for casting test samples for both normal concrete and Fiber Reinforced Concrete. The fresh mix was poured into the mould and the top surface was smoothened with the trowel. The specimen was left in the mould for 24 hours and then demoulded. Identification marks were made on the exposed face of specimen and was immersed in curing tank for 7 days and 28 days. After curing the 3 numbers of samples in each mix were tested to determine the strength. 2.3.1 MIX PROPORTIONS Indian Standard method of mix design was adopted to arrive at the mix proportion for M25 grade of concrete. Table 3.1 shows the details of mix proportion. Final mix Proportion adopted = 1:1.8:3.3 Water - Cement ratio = 0.5 Table 3.1: Mix details for M25 grade Sl. No Materials Quantity (Kg/m3)(by mass) 1. Cement (OPC) 375 2. Fine aggregate 675 3. Coarse aggregate 1190 4. Water (W/C =0.5) 187.5 2.3.2 Fiber Content A tendency towards balling or formation of fiber module is a serious problem in FRC. Balling reduces workability and increases segregation. To arrive at the fiber contents for the experimental investigation compressive strength of SFRC was determined for various fiber volume fractions and it was found that beyond 2.0% volume fractions of fiber the compressive strength is reduced and therefore steel fiber content was restricted to 2.0% and poly propylene fiber is restricted to 1%. 2.3.3 Mix for Test specimen The volume fraction of fibers for the test specimen were fixed as 1% and 1.25% for steel fiber, and 1% for
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
polypropylene fiber, based on the compressive and split tensile strength of concrete. 2.4 SPCIMEN DETAILS A total of 21 simply supported deep beams were cast. All beams were of rectangular cross section, 90mm wide and 300mm deep with 2 bars of 10 mm diameter as longitudinal reinforcement. The effective span to overall depth ratio was varied from 1.5 to 2,so as to achieve the desired shear span- to-effective depth ratio (a/d). The test specimens were divided into three series, namely, series A for a/d =0.7, series B for a/d =.8 and series C for a/d =.9. Each series consisted of seven types of deep beams with different amount of web reinforcement, varying volume fraction of steel fibers and combination of steel and poly propylene fibers. The details of the test beams are given in Table 3.2, web reinforcement details given in table 3.3 and specimen drawings are given in fig 3.1 to 3.6. Table 3.2 Specimen details: Steel Beam Le Le/D av/d fibers Designation % 1A 450 1.5 .7 0 2A 450 1.5 .7 3A 450 1.5 .7 4A 450 1.5 .7 5A 450 1.5 .7 1 6A 450 1.5 .7 1.25 7A 450 1.5 .7 1 1B 525 1.75 .8 0 2B 525 1.75 .8 3B 525 1.75 .8 4B 525 1.75 .8 5B 525 1.75 .8 1 6B 525 1.75 .8 1.25 7B 525 1.75 .8 1 1C 600 2.0 .9 0 2C 600 2.0 .9 3C 600 2.0 .9 4C 600 2.0 .9 5C 600 2.0 .9 1 6C 600 2.0 .9 1.25 7C 600 2.0 .9 1
Poly propylene fibers % 0 1 0 1 0 1
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International Journal of Advanced Engineering, Management and Science (IJAEMS)
Table 3.3 Web Reinforcement ratio details for Test beams Beam Le Le/D av/d Sv Sh v h mm mm % % 2A 450 1.5 .7 200 .25 127.5 .49 3A 450 1.5 .7 200 .25 85 .74 4A 450 1.5 .7 100 .5 127.5 .49 2B 525 1.75 .8 225 .25 127.5 .49 3B 525 1.75 .8 225 .25 85 .74 4B 525 1.75 .8 112.5 .5 127.5 .49 2C 600 2.0 .9 250 .25 127.5 .49 3C 600 2.0 .9 250 .25 85 .74 4C 600 2.0 .9 125 .5 127.5 .49
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7A = Beam with combination of steel fibers 1% and polypropylene fibers 1% and without web reinforcement 2A = Beam with .25% vertical web reinforcement ration and 0.49% horizontal web reinforcement ratio
Fig. 2.2 L.S and C.S of beams 3A and 4A-Beams with a/d = 0.7 and le/D = 1.5 where 3A = Beam with .25% vertical web reinforcement ration and 0.74% horizontal web reinforcement ratio 4A = Beam with .5% vertical web reinforcement ration and 0.49% horizontal web reinforcement ratio
Fig. 2.1 L.S and C.S of beams 1A,5A,6Aand 7A with a/d = 0.7 and le/D = 1.5 Where 1A = Beam without web reinforcement 5A = Beam with Steel fibers 1% and without web reinforcement 6A = Beam with Steel fibers 1.25% and without web reinforcement
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International Journal of Advanced Engineering, Management and Science (IJAEMS)
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
Fig. 2.4 L.S and C.S of beams 3B and 4B-Beams with a/d = 0.8 and le/D = 1.75 where 3B = Beam with .25% vertical web reinforcement ration and 0.74% horizontal web reinforcement ratio 4B = Beam with .5% vertical web reinforcement ration and 0.49% horizontal web reinforcement ratio Fig. 2.3 L.S and C.S of beams 1B,5B,6B and 7B-Beams with a/d = 0.8 and le/D = 1.75 Where 1B = Beam without web reinforcement 5B = Beam with Steel fibers 1% and without web reinforcement 6B = Beam with Steel fibers 1.25% and without web reinforcement 7B = Beam with combination of steel fibers 1% and polypropylene fibers 1% and without web reinforcement 2B = Beam with .25% vertical web reinforcement ration and 0.49% horizontal web reinforcement ratio
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International Journal of Advanced Engineering, Management and Science (IJAEMS)
Fig. 2.5 L.S and C.S of beams 1C,5C,6Cand 7C-Beams with a/d = 0.9 and le/D = 2 Where 1C = Beam without web reinforcement 5C = Beam with Steel fibers 1% and without web reinforcement 6C = Beam with Steel fibers 1.25% and without web reinforcement 7C = Beam with combination of steel fibers 1% and polypropylene fibers 1% and without web reinforcement 2C = Beam with .25% vertical web reinforcement ration and 0.49% horizontal web reinforcement ratio
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
Fig. 2.6 L.S and C.S of beams 3C and 4C-Beams with a/d = 0.9 and le/D = 2 where 3C = Beam with .25% vertical web reinforcement ration and 0.74% horizontal web reinforcement ratio 4C = Beam with .5% vertical web reinforcement ration and 0.49% horizontal web reinforcement ratio 2.5 CASTING AND CURING THE RC DEEP BEAM: Cement, fine aggregate, coarse aggregate were weighed and batched as per the design mix. The mixing of concrete was done using concrete mixer. The main purpose of mixing is to produce an intimate mixture of cement, water, fine aggregate, coarse aggregate of uniform consistency throughout the batch. Beam samples were cast for various fiber content. For RC beam the empty mould were kept ready for placing the concrete. The mould was placed on a smooth surface before concreting. After that reinforcement cafe was kept in the mould with suitable cover block the concrete was filled in the mould in three layers. The mould was placed in the vibrating table for a few seconds. After 24 hours curing was done by immersing the specimen in the curing tank for 28 days from the date of casting. The purpose of curing is to prevent the loss moisture in concrete due to evaporation thereby preventing the development of high temperature gradient within the concrete. After the curing period the specimens Page | 87
International Journal of Advanced Engineering, Management and Science (IJAEMS)
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
were taken out from the curing tank and dried. The specimens were cleaned .Reference points were marked on the specimens.
Fig 3.9 Reinforcement details of 3A, 3Band 3C
Fig 2.7 Reinforcement details for 2A,2B and 2C beams
Fig 3.10 Cast beams
Fig 3.8 Reinforcement details for 4A, 4Band 4C
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International Journal of Advanced Engineering, Management and Science (IJAEMS)
III. EXPERIMENTAL PROGRAMME 3.1 INTRODUCTION: The behaviour of deep beam is studied by applying two point loads using loading frame. The test method is developed to study the shear behaviour of the beam with varying shear span to depth ratio. 3.2 TESTING PROCEDURE: All the specimens were tested for finding inding out the Ultimate load carried by the Deep beams under two point loading at the age of 28 days. The beams are tested under gradually increasing load using a 500 kN loading frame. The beam is simply supported using knife edge support which are placed on two support beams (I sections) .The specimen is loaded using a 500kN jack which has a load cell to monitor the load. The load was transferred from the jack to specimen at two points using a spreader beam. Based on the a/d ratio the support beams on which whic the simple supports are placed and adjusted. LVDT is provided at mid span to measure deflections. The load that produced the diagonal crack and the ultimate shear crack are recorded. Crack patterns are marked on the beam. The average response of seven beams be tested in a series, is taken as the representative response of the corresponding series. The test set up is presented in Figures 4.1, LVDT arrangement is presented in Fig.4.4 and the results are presented in chapter 7.
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Fig 3.2 Beam and LVDT arrangement in 500 kN loading frame.
Fig 3.1 Details of test beams with arrangement of loads and supports.
Fig 3.3 .3 Loading frame and test set up IV.
ANALYTICAL ANALYSIS
4.1 .1 THEORETICAL CALCULATIONS Page | 89
International Journal of Advanced Engineering, Management and Science (IJAEMS)
Ultimate load carrying capacities of beams were predicted by ACI code 318-99 method. 4.2 Shear capacity by ACI code Equation According to ACI Building Code 318 -99, the shear strength of concrete deep beams is given by following equation: The shear strength at the critical section (at a distance a/2 from the support) is given below where Pu1=Pc + Ps Pc = (3.5- 2.5 Mu/Vud) (1.9√fc + 2500 ρ Vud/Mu) bd Ps = [(Av/ 12 sv) (1+Ln/d )+(Ah /12 sh) (11-Ln/d) ] fy.D • ρ = ratio of main longitudinal reinforcement, As/b.d • ρh = ratio of horizontal web reinforcement, Ah/b.Sh • ρv = ratio of vertical web reinforcement, Av/b.Sv • sh = spacing of horizontal web reinforcement • sv = spacing of vertical web reinforcement • vf = volume fraction of steel fibers • Vu = nominal shear strength of concrete as per ACI-318-1995 • Ln = clear span measured from face to face of the support • b = width of beam • d = effective depth of beam • D = overall depth of beam • fc = compressive strength of various mixes of concrete with and without fibers • Mu = factored moment at the critical section = ultimate load applied to the beam at • Pu failure 4.3 Ultimate load carrying capacity of beams 4.3.1 Ultimate load carrying capacity of beam 1A Pc = (3.5- 2.5 Mu/Vud) (1.9√fc + 2500 ρ Vud/Mu) bd Mu/Vud=0.7 ρ = 100xAst/bd =100x2xx102�/(90x275) =0.58% fc =33N/mm2 Pc =45kN Ps = [(Av/ 12 sv) (1+Ln/d )+(Ah /12 sh) (11-Ln/d) ] fy.D Ln =450mm d =275mm
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D =300mm Ps =124kN fy =415 N/mm2 Ps + Pc=45+124 kN Pu1 =169 kN 4.3.2 Ultimate load carrying capacity of beam 3A Pc = (3.5- 2.5 Mu/Vud) (1.9√fc + 2500 ρ Vud/Mu) bd Mu/Vud=0.7 ρ = 100xAst/bd =100x2xx102�/(90x275) =0.58% fc =33N/mm2 Pc =45kN Ps = [(Av/ 12 sv) (1+Ln/d )+(Ah /12 sh) (11-Ln/d) ] fy.D Av =14x�x62/4 =395 mm2 Ah =4x �x62/4 =113mm2 Sh =127.5mm Sv =125mm Ln =450mm d =275mm D =300mm fy =415 N/mm2 Ps =164kN Ps + Pc=45+167 kN Pu1 =212 kN 4.3.3 Ultimate load carrying capacity of beam 5A Steel fiber added = 1% Pc = (3.5- 2.5 Mu/Vud) (1.9√fc + 2500 ρ Vud/Mu) bd Mu/Vud=0.7 ρ = 100xAst/bd +1% =100x2xx102�/(90x275) +1% =1.58% fc =35N/mm2 Pc =46kN Ps = [(Av/ 12 sv) (1+Ln/d )+(Ah /12 sh) (11-Ln/d) ] fy.D Ln =450mm d =275mm D =300mm fy =415 N/mm2 Ps =133kN Ps + Pc=46+133kN Pu1 =179 kN
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International Journal of Advanced Engineering, Management and Science (IJAEMS)
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
Table 4.1 Load predicted by ACI code method Beam
Le
Le/D
av/d
ρv %
ρh %
1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.75 1.75 1.75 1.75 1.75 1.75 1.75 2.0 2.0 2.0 2.0 2.0 2.0 2.0
.7 .7 .7 .7 .7 .7 .7 .8 .8 .8 .8 .8 .8 .8 .9 .9 .9 .9 .9 .9 .9
.25 .25 .5 .25 .25 .5 .25 .25 .5 -
.49 .74 .49 .49 .74 .49 .49 .74 .49 -
in mm
1A 2A 3A 4A 5A 6A 7A 1B 2B 3B 4B 5B 6B 7B 1C 2C 3C 4C 5C 6C 7C
450 450 450 450 450 450 450 525 525 525 525 525 525 525 600 600 600 600 600 600 600
Ultimate load carrying capacity of all the 21 beams were calculated using the ACI method and presented in table 5.1 where 1A, 1B, 3B -Beams without web reinforcement 2A, 3A, 4A, 2B, 3B, 4B, 2C, 3C, 4C -Beams with three types of web reinforcement 5A, 5B, 5C - Beams with steel fiber 1% as replacement of web reinforcement 6A, 6B, 6C - Beams with steel fiber 1.25% as replacement of web reinforcement 7A, 7B, 7C - Beams with steel fiber 1% and Poly propylene fiber 1% as replacement of web reinforcement 4.4 FINITE ELEMENT ANALYSIS 4.4.1 MODELING OF CONCRETE AND REINFORCEMENT ANSYS and CIVILFEM bundled product is the most advanced, comprehensive and reputable finite element analysis and design software package available for civil engineering projects. The concrete has been modeled using ‘ANSYS CIVILFEM’ shown in fig 5.1. The compressive strength and tensile strength are established based on test data of the specimens cast and tested along with the rectangular beams. The data was
SF %
PPF %
Pc (kN)
Ps (kN)
Predicted load (kN) Pu1 0 0 45 124 169 45 174 219 45 167 212 45 135 180 1 46 133 179 1.25 47 135 182 1 1 53 134 187 0 0 39 124 163 39 174 213 39 170 209 39 138 177 1 40 132 172 1.25 41 134 175 1 1 46 133 179 0 0 32 124 156 32 159 191 32 173 205 32 134 166 1 33 129 162 1.25 34 131 165 1 1 38 130 168 used for defining concrete (‘CONCR’) properties in ‘ANSYS’. Before cracking or crushing, concrete is assumed to be an isotropic elastic material. After crushing, the concrete is assumed to have lost its stiffness in all directions. The concrete young’s modulus is taken as 25000MPa and the Poisson’s ratio as 0.2. In the present analysis a constant mesh size of 10mm is assumed. The longitudinal reinforcement i.e., the High Yield Strength Deformed (HYSD) have been modeled using ANSYS CIVILFEM. The cross sectional area of each element is given as area equivalent to each rebar. 5
The rebar young’s modulus is taken as 2 x 10 MPa and Poisson’s ratio as 0.3. For the rebar the same mesh size as that of concrete element is adopted. Perfect bond between concrete and reinforcement is ensured between the two elements in ANSYS.
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International Journal of Advanced Engineering, Management and Science (IJAEMS)
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
Table 5.2 ANSYS model detail CATEGORIES TYPES OF ELEMENT Concrete Steel
ANSYS MODEL ANSYS CivilFEM M25 fy415 4
MATERIAL PROPERTISE Concrete Steel
E = 2.5x10 µ = 0.2
CATEGORIES MODEL DESCRIPTION Modeling approach Size of the beam
ANSYS MODEL Full size model 90x300x800mm 90x300x725mm 90x300x650mm
BOUNDARY CONDITIONS Left End Right End
UY DOF restrained
LOADING TYPE
Two point loading
c
5
E = 2x10 µ = 0.3 s
Fig.4.1 Properties of Modeled Beam
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International Journal of Advanced Engineering, Management and Science (IJAEMS)
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
Fig 4.2 ANSYS modeled beam
Fig 4.3 Deflection of modeled beam for a/d =0.7
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International Journal of Advanced Engineering, Management and Science (IJAEMS)
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
Fig 4.4 ANSYS modeled beam for a/d = 0.8
Fig 5.5 Deflection of modeled beam for a/d =.9
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International Journal of Advanced Engineering, Management and Science (IJAEMS)
Fig 5.1, 7 and 28 days strength for concrete cubes 5.2.2 SPLIT TENSION TEST 5.3 SHEAR TEST RESULTS Table 6.4 to 6.6 shows the test results of RC deep beams observed during test. Table 6.3 Beam -1A(eff. length=450, a/d=.7)
SF = 1.25%
SF = 1% + PPF =1%
SF = 1% + PPF =.5%
28 day strength in N/mm2
28 day‌
SF = 1%
7 day strength in N/mm2
4.5 4 3.5 3 2.5 2 1.5 1 0.5 0
PPF =1%
33 35.34 36.71 35.7 47 42.15 36.45 35.38
PPF =.5%
50 45 40 35 30 25 20 15 10 5 0
21 25 27 25 31.5 28.1 25.8 24.63
Control mix
Control mix SF = 1% SF = 1.25% SF = 2% SF = 1% + PPF =1% SF = 1% + PPF =.5% PPF =1% PPF =.5%
control mix SF =1.25% SF =1% + PPF =1% PPF =1%
Compressive strenght in N/mm2
1. 2. 3. 4. 5. 6. 7. 8.
5.2 PRELIMINARY INVESTIGATIONS: Results of compression and split tension test to determine the strength of concrete to be used for calculating the shear capacity is presented in table 6.1 and 6.2 5.2.1 COMPRESSION TEST The compressive strength of cubes after 7 days and 28 days are tabulated in table 6.1and fig 6.1. The split tensile strength of cylinders after 28 days curing are shown in table 6.2 and fig 6.2. Table 6.2 Split Tensile strength Sl.no Description of specimen Split Tensile Strength of Concrete (N/mm2) 1. Control mix 2.53 2. SF = 1% 2.5 3. SF = 1.25% 2.6 4. SF = 1% + PPF =1% 4 5. SF = 1% + PPF =.5% 3.93 6. PPF =1% 2.2 7. PPF =.5% 2.3
Split Tesile strength of concrete N/mm2
V. RESULTS AND DISCUSSIONS 5.1 GENERAL In this chapter the experimental behaviour and mode of failure of RC Deep beams are discussed. The beams were tested under two point loading and their and their behaviour for fiber content and web reinforcement were observed and presented in this chapter. All the beam specimens were loaded up to failure and corresponding deflections were noted. Table 5.1 Compressive strength at 7 days and 28 days Trial Description of specimen Compressive strength no. of cubes N/mm2 7 days 28 days
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
Fig 5.2 Split tensile strength for cylinder From the above tables 6.2 and 6.3 it is seen that beyond 2.0% volume fractions of steel fiber the compressive strength is reduced and therefore fiber content was restricted to 2.0% and poly propylene fiber is restricted to 1%. Hence beams were cast for these volume fractions. Sl. No Load in kN Mid span deflection in mm 1. 25 0.19 2. 50 0.32 Page | 95
International Journal of Advanced Engineering, Management and Science (IJAEMS)
3. 4.
98(initial crack ) 150
1.67
5.
182 (ultimate )
2.4
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1.03 Table 6.5 Beam -3A(eff. length=450, a/d=.7) Sl.No Load in kN Mid span deflection in mm 1. 25 0.08 2. 50 0.19 3. 98(initial crack ) 0.65
Table 6.4 Beam -2A(eff. length=450, a/d=.7) Sl.No Load in kN Mid span deflection in mm 1.
25
0.17
2.
50
0.29
3.
1.16
4.
103(initial crack ) 150
5.
199 (ultimate )
2.6
4.
150
0.67
5.
178 (ultimate )
0.94
4.
150
0.97
5.
195 (ultimate )
1.3
Table 6.6 Beam -4A(eff. length=450, a/d=.7) Sl.No Load in kN Mid span deflection in mm 1. 25 0.032 2. 50 0.072 3. 84(initial crack ) 0.42
1.73
5.
222 (ultimate )
6.2
5.
218 (ultimate )
3.9
Ultimate load in kN
250 Table 6.7 Beam -5A(eff. length=450, a/d=.7) Sl.No Load in kN Mid span deflection in mm 1. 25 0.13 2. 50 0.64 3. 113(initial crack ) 1.03 4. 150 2.04
1A
200
2A
150
3A
100
4A 5A
50
6A 0 Table 6.8 Beam -6A(eff. length=450, a/d=.7) Sl.No Load in kN Mid span deflection in mm 1. 25 0.45 2. 3. 4. 5.
50 115(initial crack ) 150 220 (ultimate )
0.89 1.78 2.32 4.1
Table 6.9 Beam -7A(eff. length=450, a/d=.7) Sl.No Load in kN Mid span deflection in mm 1. 25 0.86 2. 50 1.32 3. 113(initial crack ) 2.12 4.
150
3.45
7A 0
5 Deflection in mm
10
Fig.5.3 Ultimate load Vs Deflection of a/d=0.7 Fig. 5.A shows the Load Vs Deflection behaviour of A series beams (a/d=0.7). It is observed that the Ultimate load of the Beam 7A is more than that of all other beams indicating that the inclusion of combination of steel and polypropylene fiber is contributing to the strength.
Table 5.10 Beam -1B(eff. length=525, a/d=.8) Sl.No Load in kN Mid span deflection in mm 1. 25 0.59 2.
50
0.82
3.
95(initial crack )
1.93 Page | 96
International Journal of Advanced Engineering, Management and Science (IJAEMS)
150
2.37
5.
175 (ultimate )
3.8
Table 5.11 Beam -2B (eff. length=525, a/d=.8) Sl.No Load in kN Mid span deflection in mm 1. 25 0.32 2.
50
0.78
3. 4.
84(initial crack ) 150
1.52 2.07
5.
178 (ultimate )
3.53
Table 5.12 Beam -3B (eff. length=525, a/d=.8) Sl.No Load in kN Mid span deflection in mm 1. 25 0.64 2. 50 1.03 3.
89(initial crack )
2.37
4. 5.
150 179 (ultimate )
3.52 4.1
Table 5.13 Beam -4B (eff. length=525, a/d=.8) Sl.No Load in kN Mid span deflection in mm 1. 25 0.18 2. 50 0.68 3.
83(initial crack )
1.23
4. 5.
150 174 (ultimate )
2.32 3.6
Table 5.14 Beam -5B (eff. length=525, a/d=.8) Sl.No Load in kN Mid span deflection in mm 1. 25 0.79 2. 50 1.89 3. 108(initial crack ) 2.69 4. 150 3.52 5.
212 (ultimate )
5.
214 (ultimate )
5.3
Table 5.16 Beam -7B (eff. length=525, a/d=.8) Sl.No Load in kN Mid span deflection in mm 1. 25 1.12 2. 50 2.56 3. 106(initial crack ) 4.67 4. 150 5.23 5.
216 (ultimate )
9.6
250
Ultimate load in kN
4.
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200
1B 2B
150
3B
100
4B 5B
50
6B 0
7B 0
5
10
15
Deflection in mm Fig. 5.4 Ultimate load Vs Deflection Fig. 6.4 shows the Load Vs Deflection behaviour of B series beams (a/d=0.8). It is observed that the Ultimate load of the Beam 7B is more than that of all other beams indicating that the inclusion of combination of steel and polypropylene fiber is contributing to the strength. Table 5.17 Beam -1C (eff. length=600, a/d=.9) Sl.No load in kN Mid span deflection in mm 1. 25 0.73 2. 50 1.72 3. 94(initial crack ) 2.83 4. 150 3.67 5. 171 (ultimate ) 4.2
4.9
Table 5.15 Beam -6B (eff. length=525, a/d=.8) Sl.No Load in kN Mid span deflection in mm 1. 25 0.67 2. 50 1.81 3. 110(initial crack ) 2.72 4. 150 3.63
Table 5.18 Beam -2C (eff. length=600, a/d=.9) Sl.No Load in kN Mid span deflection in mm 1. 25 0.93 2. 50 1.83 3. 87(initial crack ) 2.94 4. 150 4.3 5. 174 (ultimate ) 5.7
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International Journal of Advanced Engineering, Management and Science (IJAEMS)
Table 5.19 Beam -3C (eff. length=600, a/d=.9) Sl.No Load in kN Mid span deflection in mm 1. 25 0.79 2. 50 1.58 3. 86(initial crack ) 2.76 4.
150
3.79
5.
175 (ultimate )
4.5
2. 3.
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
50 103 (initial crack ) 150 212 (ultimate )
4. 5.
4.79 6.46 10.04 13.21
Table 5.20 Beam -4C (eff. length=600, a/d=.9) Sl.No Load in kN Mid span deflection in mm 6. 25 0.81 7. 50 1.74 8. 81 (initial crack 2.69 ) 9. 150 3.65 10. 169 (ultimate ) 4.6
Ultimate load in kN
250
1C
200
2C
150
3C
100
4C
50
5C
0
6C 0
5
10
15
7C
Deflection in mm Fig. 5.5 Ultimate load Vs Deflection
Table 5.22 Beam -6C (eff. length=600, a/d=.9) Sl.No Load in kN Mid span deflection in mm 1. 25 1.03 2. 50 2.73 3. 107(initial crack 3.94 ) 4. 150 5.4 5. 209 (ultimate ) 6.4
Table 5.23 Beam -7C (eff. length=600, a/d=.9) Sl.No Load in kN Mid span deflection in mm 1. 25 2.23 where Curve 1 represent Ultimate loads of beam 1A,1B,7C Curve 2 represent Ultimate loads of beam 2A,2B,7C Curve 3 represent Ultimate loads of beam 3A,3B,7C Curve 4 represent Ultimate loads of beam 4A,4B,7C Curve 5 represent Ultimate loads of beam 5A,5B,7C
Fig. 6.5 shows the Load Vs Deflection behaviour of C series beams (a/d=0.7). It is observed that the Ultimate load of the Beam 7C is more than that of all other beams indicating that the inclusion of combination of steel and polypropylene fiber is contributing to the strength. 300
Ultimate load in kN
Table 5.21 Beam -5C (eff. length=600, a/d=.9) Sl.No Load in kN Mid span deflection in mm 1. 25 0.79 2. 50 1.72 3. 103(initial crack 2.93 ) 4. 150 4.5 5. 205(ultimate ) 5.8
1 200
2 3 4
100
5 6
0 0.6
0.7
0.8
0.9
shear span/ eff. depth ratio Fig. 5.6 Ultimate load Vs Shear span /depth ratio Curve 6 represent Ultimate loads of beam 6A,6B,7C Curve 7 represent Ultimate loads of beam 7A,7B,7C Fig. 5.6 shows the Ultimate Load Vs shear span /depth ratio behaviour of A,B and C series beams (a/d=0.7,0.8,0.9). It is observed that the Ultimate load
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International Journal of Advanced Engineering, Management and Science (IJAEMS)
constantly decreasing when increasing the shear span to depth ratio. Table 5.24 Summary of shear test results Beam
Le
Maximum Deflection (mm)
Initial Ultimate crack Load load (kN) (kN) 1A 450 2.4 98 182 2A 450 2.6 103 199 3A 450 1.3 98 195 4A 450 0.94 84 178 5A 450 3.9 113 218 6A 450 4.1 115 220 7A 450 6.2 113 222 1B 525 3.8 95 175 2B 525 3.53 84 178 3B 525 4.1 89 179 4B 525 3.6 83 174 5B 525 4.9 108 212 6B 525 5.3 110 214 7B 525 9.6 106 216 1C 600 4.2 94 171 2C 600 5.7 87 174 3C 600 4.5 86 175 4C 600 4.6 81 169 5C 600 5.8 103 205 6C 600 6.4 107 209 7C 600 13 103 212 uring testing time the initial crack load, first crack location and the ultimate failure load were taken. All the beams failed under shear failure. The initial crack started from the supports and run through the loading point.
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
Summary of shear test results where 1A, 1B, 3B -Beams without web reinforcement 2A, 3A, 4A, 2B, 3B, 4B, 2C, 3C, 4C -Beams with three types of web reinforcement 5A, 5B, 5C - Beams with steel fiber 1% 6A, 6B, 6C - Beams with steel fiber 1.25% 7A, 7B, 7C - Beams with steel fiber 1% and Poly propylene fiber 1% From table6.24 it is observed that Ultimate load is maximum for the beams 7A, 7B and 7C when compared to all other beams, where these beams contain the combination of steel and polypropylene fibers as replacement of web reinforcement. 5.5 Crack Pattern The crack patterns of the specimens are shown in Fig 6.76.10 all the beams were tested under two point loading. D
Fig. 5.7 Cracking Pattern and Mode of Failure of beam 1C In the fig 6.7 Beam 1B crack starts at the mid span and run through the top. While increasing load crack starts form one support and propagates towards the loading point.
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International Journal of Advanced Engineering, Management and Science (IJAEMS)
Fig 5.8 Cracking Pattern and Mode of Failure of beam 7C The fig. 6.8 shows the crack pattern of beam 7C. There is no mid span crack in the beam. Crack starts from one edge of the support and propagates towards the loading point.
Fig. 5.9 Cracking Pattern and Mode of Failure of beam 4B In the fig 6.9 Beam 4B crack starts at the mid span and run through the top. While increasing load crack starts form the two supports and propagates towards the loading points.
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
Fig. 5.10 Cracking Pattern and Mode of Failure of beam 2A In Fig 6.10 perfect shear failure of beam 2A is observed. Crack starts from one side support and ran through the loading point. Sudden failure was occurred. 5.6 DISCUSSIONS 5.6.1 VARYING SHEAR SPAN / EFF. DEPTH Typical load-deflection (at mid span) relationships are shown in Figure 6.3, 6.4 and 6.5 for the beam series A,B and C with a/d ratio of 0.7, 0.8 and 0.9. As the web reinforcement increased, both the first crack and maximum applied load increased. Decrease in shear span reduced the occurrence and extent of flexural cracking. For example, in beam series B, which had a/d ratio 0.8 (fig 6.9), flexural cracks formed first within the constantmoment region (near mid span), and later, diagonal cracks formed within the region of constant shear leading to failure. In case of beam series B (a/d = 0.8), both flexural and diagonal cracking occurred almost simultaneously, whereas for beam series A (a/d = 0.7), diagonal cracks lead to failure. 5.6.2 VARYING WEB REINFORCEMENT As the load was increased inclined cracks propagated towards the support and loading points. Further increase in load resulting in the propagation and widening of the existing cracks leading to shear failure. When horizontal web reinforcement ratio increased to .25 % to 0.5 % then 11to 16 percentage increases in Ultimate load was observed. When the vertical web reinforcement ratio increased from 0.49 % to 0.74 % then a close variation of 1 to 3 % is observed. 5.6.3 VARYING FIBER CONTENT For beams having volume fraction of steel fibers as 1.0%, 1.25%, combination of Steel fibers 1% and Polypropylene fibers 1% maximum load applied was more than for the Page | 100
International Journal of Advanced Engineering, Management and Science (IJAEMS)
450 450 450
169 219 212
182 199 195
4A
450
180
178
5A
450
179
218
6A
450
182
220
7A
450
187
222
1B
525
163
175
2B
525
213
178
3B
525
209
179
4B
525
177
174
5B
525
172
212
6B
525
175
214
7B
600
179
216
1C
600
156
171
2C
600
191
190
3C
600
205
175
4C
600
166
169
5C
600
162
205
6C
600
165
209
7C
600
168
212
where 1A,1B,3B -Beams without web reinforcement 2A,3A,4A,2B,3B,4B,2C,3C,4C -Beams with three types of web reinforcement
Load in kN
1A 2A 3A
150 100
1A ANSYS
50 0 0
1
2
3
Deflection mm 200 150
Load in kN
Table 5.25 Summary of Predicted loads and Ultimate loads Beam Le Predicted Ultimate Designation Load load (kN) ACI code (kN) method
5A,5B,5C - Beams with steel fiber 1% 6A,6B,6C - Beams with steel fiber 1.25% 7A,7B,7C - Beams with steel fiber 1% and Poly propylene fiber 1% Table 6.25 explains the summary of predicted load and ultimate loads of beam series A,B and C with shear span to depth ratio 0.7,0.8 and 0.9 and span to depth ratio is 1.5, 1.75 and 2. When comparing the Ultimate load value for the beams containing fiber content is less when compared to the Ultimate load value for the beams with web reinforcement. But, in experimental values Ultimate load values is high for the beams with fiber content. Especially, beam containing steel fiber 1% and polypropylene fiber 1% posses high ultimate load. 5.6.5 COMPARISON OF ANALYTICAL(ANSYS) AND EXPRIMENTAL 200
100
2B ANSYS
50 0 0
2
4
Deflection mm
200
Load in kN
beams containing web reinforcement. No cracking was observed in any beam up to about 50 percent of ultimate load. At about 52- 60 percent of ultimate load a diagonal tension crack formed in beams without steel fiber. Whereas in beams with steel fibers first diagonal crack formed at about 58-65 percent of the ultimate load almost in the middle of the shear span. The tested beams are shown in Figure 6.8, 6.9, 6.10, 6.11. It is evident from Table 6.24 and Figure 6.6 that ultimate strength decreased with increasing a/d ratio in all types of beams. 5.6.4 COMPARSION OF ANALYTICAL AND EXPERIMENTAL VALUES
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
150 100
1C ANSYS
50 0 0
2 Deflction in 4mm
6
Fig 5.11 Comparison of response of load - deflection for experimental and ANSYS Page | 101
International Journal of Advanced Engineering, Management and Science (IJAEMS)
The Load- Deflection response of Deep beams without shear reinforcement has been compared with the experimental results in Fig-6.11. The illustration articulate, at the initial stage of loading the ANSYS model data slightly parallel with the test data, where as in the post crack regime it was found to be smoother compared to experimental results. The variation in the results may be attributed to the difference in bond characteristics of concrete and reinforcement in the model and the test. The ANSYS model could predict the results modestly up to the ultimate load. The model could not predict the loaddeflection response in the post crack regime as the elements are distorted above the specified limit leading to failure of the specimen. The behaviour of concrete elements modeled in ANSYS is as such that after crushing to maximum extent the material shows a softening behaviour in all direction resulting in distortion of all the linked elements. The first crack observed in the shear span during the testing of the beam was found to be similar in the ANSYS predicted model. In further stages of loading of ANSYS predicted model the cracks propagated through the shear span and new cracks emerged at the constant moment zone at the loads closer to ultimate load. The orientations of cracks predicted by the model are inclined in the shear span region and vertical in constant moment region. The crack patterns and the order of cracks predicted by ANSYS model are in confirming with experimental observations. During the test process, at ultimate load the inclined crack in shear span widened and concrete under the load point crushed. The ANSYS model predicted the crushing of concrete at ultimate by indicating large distortion of element nodes. VI. CONCLUSION Based on the test results presented in this study the following conclusions can be drawn. • The inclusion of short steel fibers and combination steel and polypropylene fibers in concrete mix provides effective shear reinforcement in deep beams and provides better crack control and deformation characteristic of beams. • Both the first crack strength and ultimate strength in shear increase with the provision of web reinforcement. More significant increase was found for the fiber reinforced beams because of their increased resistance to propagation of cracks. • Shear strength increases with increasing fiber content and decreasing a/d ratio. • The theoretical prediction of ultimate shear strength on the basis of methods used in the study gives
•
•
•
•
•
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
results close to the observed values in most of the beams tested. Maximum increase of 18 percent in Ultimate load for beam containing combination of steel and poly propylene fibers was observed when compared with beam containing no web reinforcement. Also for all the beams tested in this programme maximum shear strength was attained in beams reinforced with combination of steel and poly propylene fibers followed by beams containing web reinforcement. These results support the use of steel fibers in combination with poly propylene fibers as an alternative to conventional web reinforcement is deep beams. The steel fiber and poly propylene fiber as web reinforcement, enhances the behaviour of the specimen in terms of initial crack load, ultimate shear strength, and deflection characteristics. The general behaviour of the deep beam in finite element models represented by the load-deflection plots at mid span show good agreement with test data from the full-scale beam tests.
REFERENCE [1] S.K. Madan , G. Rajesh Kumar And S.P. Singh Asian Journal Of Civil Engineering (Building And Housing)Vol. 8, No. 5 (2007) [2] “Steel Fibers As Replacement Of Web Reinforcement For Rcc Deep Beams In Shear" T.M. Yoo, J.H. Doh, H. Guan, S. Fragomeni 2003; 544553 [3] “Experimental Work On Reinforced And Prestressed Concrete Deep Beams With Various Web Openings" Gerardo Aguilar, Adolfo B. Matamoros, Gustavo J. Parra-Montesinos, Julio A. Ramírez, And James K. Wight 2003;Technical Paper; Title No. 99-S56 [4] "Experimental Evaluation Of Design Procedures For Shear Strength Of Deep Reinforced Concrete Beams" Shah D.L. And Modhera C.D. IJAET/Vol.I/ Issue II/July-Sept.,2010/292-305 [5] "Evaluation Of Shear Strength Of Self - Compacting Concrete Deep Beam" Young Mook Yun VOL. 5, NOS 1-2 (2004) [6] "Ultimate Strength Analysis Of Structural Concrete Deep Beams Using Strut-Tie Models" Vengatachalapathy.V , Ilangovan.R International Journal Of Civil And Structural Engineering Volume 1, No 3, 2010 [7] "A Study On Steel Fibre Reinforced Concrete Deep Beams With And Without Openings" Soo-Yeon Page | 102
International Journal of Advanced Engineering, Management and Science (IJAEMS)
SEO, Seung-Joe YOON, Woo-Jin LEE August 1-6, 2004 [8] “Structural Behavior Of R/C Deep Beam With Headed Longitudinal Reinforcements"T.R. Naik, S.S. Singh, C.O. Huber And B.S. Brodersen Construction And Building Materials 26 (2012) 423–436;July 2011 [9] "Use Of Post-Consumer Waste Plastics In CementBased Composites" Wen-Yao Lu; Cement & Concrete Composites 27 (2005) 413–420 [10] "Shear Strength Prediction For Steel Reinforced Concrete Deep Beams" IS: 456-2000, Code Of
[Vol-1, Issue-2, May- 2015] ISSN: 2454-1311
Practice For Plain And Reinforced Concrete (Fourth Revision), Bureau Of Indian Standards, New Delhi, 2000. [11] ACI Committee 318, Building Code Requirements For Structural Concrete (318-95) And Commentary, American Concrete Institute, Farmington Hills, MI, 1995. [12] ACI Committee 318, Building Code Requirements For Structural Concrete (318-99) And Commentary, American Concrete Institute, Farmington Hills, MI, 1999
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