IJSTE - International Journal of Science Technology & Engineering | Volume 3 | Issue 06 | December 2016 ISSN (online): 2349-784X
Design and Experimental Analysis of Composite Grating Mr. Akash H. Barhe PG Student (Design Engineering) Department of Mechanical Engineering S.N.D. College of Engineering & Research Center, Yeola (Nasik), India
Prof. Bhamre V.G. Head of Dept. Department of Mechanical Engineering S.N.D. College of Engineering & Research Center, Yeola (Nasik), India
Abstract Steel grating has been the standard industrial foot walk products and has been a popular grating choice for many years. The steel grating is widely used in refineries on landing and operating platforms. These industries has great interest in a cheaper, but quality alternative for steel grating since it offers great techno-commercial advantage to them. In this paper the design and experimental analysis of composite grating is carried out. The numerical design of composite grating is conducted as per IS guidelines used in industrial practices for grating design. The model prepared for composite grating is evaluated in finite element analysis. For experimental testing, Composite grating plate is fabricated from hand lay-up process. This grating plate is analyzed experimentally against predefined load test. Finally the results are discussed to conclude the paper. Keywords: Grating Platform, Gratings ________________________________________________________________________________________________________ I.
INTRODUCTION
The gratings are widely used in factories, workshops, mining, ports of various platforms, refineries, power plants and petrochemical industries on landing and operating platforms. Gratings are used at different walkways, access zones in to take live and/or dead loads depending on application. These industries has great interest in a cheaper, but quality alternative for steel grating since it offers great techno-commercial advantage to them.
Fig. 1: Typical Grating Platform Made of Carbon Steel
Typically manufactured from mild carbon steel, aluminum and stainless steels, bar gratings are also available in specialty metal alloys to suit nearly any application. The metallic gratings used in industrial applications are having certain limitations as listed below. 1) The metallic gratings are made from stainless steel, aluminum, carbon steel which have high density and hence the grating is heavy. This directly effect on the design of supporting structure and civil foundation of the plant. 2) The carbon steel grating is corrosion prone. Therefore they cannot be used in corrosive atmosphere without galvanizing treatment. The introduction of composite gratings will help in designing structural platform with same strength at lesser cost and equal quality and reliability. Being corrosion resistant, the grating will not require additional galvanizing or painting. This will further save the cost of project. II. DESIGN CALCULATIONS Following sections will provide the design and sizing of composite grating.
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Loading on Grating Platform As the composite grating is being designed as an alternative to steel grating, the composite grating shall be suitable to withstand the equal load which is applicable for carbon steel grating. Therefore imposed loads in this case will remain same as that of steel grating. Sr. No. 1 a. b.
c.
Table – 1 IS 875 Parts 2, 1987, Imposed Floor Loads for Different Occupancies Occupancy Classification Uniformly Distributed Load (UDL), kN/nm3 Industrial Building Work area without machinery / equipment 2.5 Work area with machinery / equipment Light Duty 5.0 Medium Duty 7.0 Heavy Duty 10.0 Boiler rooms and plant rooms 5.0
Concentrated Load, kN 4.5 4.5 4.5 4.5 6.7
Accordingly, Total imposed load on the grating [10] = đ?‘Šđ?‘–đ?‘šđ?‘?đ?‘œđ?‘ đ?‘’đ?‘‘ = 5.0 đ?‘˜đ?‘ = 5000 đ?‘ Total dead load on the grating = đ?‘Šđ?‘‘đ?‘’đ?‘Žđ?‘‘ = 400 đ?‘ đ?‘Šđ?‘Ąđ?‘œđ?‘Ąđ?‘Žđ?‘™ = 5400 đ?‘ Total number of flats in 1m X 1m grating platform is given by, đ??şđ?‘&#x;đ?‘Žđ?‘Ąđ?‘–đ?‘›đ?‘” đ?‘†đ?‘?đ?‘Žđ?‘› 1000 đ?‘ đ?‘“đ?‘™đ?‘Žđ?‘Ą = = đ?‘†đ?‘?đ?‘Žđ?‘?đ?‘–đ?‘›đ?‘”đ?‘“đ?‘™đ?‘Žđ?‘Ą 40 đ?‘ đ?‘“đ?‘™đ?‘Žđ?‘Ą = 25 Total load taken by single flat is given by, đ?‘Šđ?‘Ąđ?‘œđ?‘Ąđ?‘Žđ?‘™ 5400 đ?‘Šđ?‘“đ?‘™đ?‘Žđ?‘Ą = = đ?‘ đ?‘“đ?‘™đ?‘Žđ?‘Ą 25 đ?‘Šđ?‘“đ?‘™đ?‘Žđ?‘Ą = 216 đ?‘ Each bearing bar will carry equal load of 216 N. This load will be uniformly distributed on the complete span. The bearing bars are simply supported on side plates. Now, Total length of each flat = Lflat = 1000 mm or 1 m. Uniform Distributed Load (UDL) on each flat is given by, đ?‘Šđ?‘“đ?‘™đ?‘Žđ?‘Ą 216 đ?‘ˆđ??ˇđ??żđ?‘“đ?‘™đ?‘Žđ?‘Ą = = đ??żđ?‘“đ?‘™đ?‘Žđ?‘Ą 1000 đ?‘ˆđ??ˇđ??żđ?‘“đ?‘™đ?‘Žđ?‘Ą = 0.216 đ?‘ /đ?‘šđ?‘š Design of Grating for Bending Stresses Maximum bending moment for simply supported beam having uniform load distribution is given by, đ?‘¤đ?‘™ 2 đ?‘€đ?‘?đ?‘’đ?‘›đ?‘‘đ?‘–đ?‘›đ?‘” = 8 Therefore, đ?‘ˆđ??ˇđ??żđ?‘“đ?‘™đ?‘Žđ?‘Ą Ă— đ??ż2đ?‘“đ?‘™đ?‘Žđ?‘Ą đ?‘€đ?‘?đ?‘’đ?‘›đ?‘‘đ?‘–đ?‘›đ?‘” = 8 0.216Ă—10002 đ?‘€đ?‘?đ?‘’đ?‘›đ?‘‘đ?‘–đ?‘›đ?‘” = 8 đ?‘€đ?‘?đ?‘’đ?‘›đ?‘‘đ?‘–đ?‘›đ?‘” = 27000 đ?‘ . đ?‘šđ?‘š The material of construction for composite grating is Fibre Reinforced Plastic (FRP). It has ultimate tensile strength in the range of 480 to 1650 MPa depending upon the properties of parent materials. Sr. No. 1 2 3
Reinforcing Material Steel Glass FRP Basalt FRP
Table – 2 Mechanical Design Properties of FRP Yield Strength ksi (MPA) Tensile Strength ksi (MPA) 40-75 (276-517) N/A N/A 70-230 (480-1,600) N/A 150-240 (1,035-1,650)
Elastic Modulus ksi (MPA) 29,000 (200) 5,100-7,400 (35-51) 6,500-8,500 (45-59)
Therefore we will take the lowest UTS for glass FRP i.e. 480 MPa to design the grating bearing bars. The maximum allowable stress in bending is given as below: đ?œŽđ?‘Žđ?‘™đ?‘™đ?‘œđ?‘¤đ?‘Žđ?‘?đ?‘™đ?‘’ = 0.66 Ă—đ?‘“đ?‘ˆđ?‘‡đ?‘† đ?œŽđ?‘Žđ?‘™đ?‘™đ?‘œđ?‘¤đ?‘Žđ?‘?đ?‘™đ?‘’ = 0.66 Ă—480 đ?œŽđ?‘Žđ?‘™đ?‘™đ?‘œđ?‘¤đ?‘Žđ?‘?đ?‘™đ?‘’ = 316.8 đ?‘ /đ?‘šđ?‘š2 All rights reserved by www.ijste.org
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The section modulus of the beam is given by, đ?‘€đ?‘?đ?‘’đ?‘›đ?‘‘đ?‘–đ?‘›đ?‘” đ?œŽđ?‘Žđ?‘™đ?‘™đ?‘œđ?‘¤đ?‘Žđ?‘?đ?‘™đ?‘’ 27000 đ?‘?đ?‘“đ?‘™đ?‘Žđ?‘Ą = 316.8 đ?‘?đ?‘“đ?‘™đ?‘Žđ?‘Ą = 85đ?‘šđ?‘š3 Since the bearing bars for composite grating will be rectangular shaped, it will have section modulus which is given by, đ?‘?â„Ž2 đ?‘?đ?‘“đ?‘™đ?‘Žđ?‘Ą = 6 Therefore, đ?‘?â„Ž2 0.085 = 6 Here we can select either height or width and then the remaining dimension can be derived. Let’s consider the thickness of flat as 5mm for ease of manufacturing and higher strength. Therefore, 5 Ă— â„Ž2 0.085 = 6 â„Ž = 10 đ?‘šđ?‘š Since the height of the bearing bar is derived from the opted thickness, will select 20.0 mm height for bearing bar for composite grating. đ?‘?đ?‘“đ?‘™đ?‘Žđ?‘Ą =
Design of Grating for Deflection due to Loading Maximum deflection for simply supported beam having uniformly distributed load across the span is given by, đ?‘¤đ?‘™ 4 5 đ?›żđ?‘šđ?‘Žđ?‘Ľ = Ă— đ??¸đ??źđ?‘‹đ?‘‹ 384 Where, w = Uniformly Distributed Load (UDL)on beam, N/mm l = Total length of beam over which load is distributed, mm E = Modulus of Elasticity for glass FRP = 35 N/mm2 bh3 IXX = Moment of Inertia, mm4 = 12 Therefore, bh3 IXX = 12 5Ă—203 IXX = 12 IXX = 3334 mm4 Maximum deflection can be obtained as, 0.216 Ă—10004 5 δmax = Ă— 3 35 Ă—10 Ă—3334 384 δmax = 24 mm Allowable deflection for any load carrying member is given by, Lflat δallowable = 400 1000 δallowable = 400 δallowable = 2.5 mm Comparing the deflections, đ?›żđ?‘šđ?‘Žđ?‘Ľ ≼ đ?›żđ?‘Žđ?‘™đ?‘™đ?‘œđ?‘¤đ?‘Žđ?‘?đ?‘™đ?‘’ Hence the bearing bar is failing for deflection which is the most commonly observed failures in composites. In order to overcome this failure, we will increase the flat height to 50mm. Rechecking the deflection, 5Ă—503 đ??źđ?‘‹đ?‘‹ = 12 đ??źđ?‘‹đ?‘‹ = 52083 đ?‘šđ?‘š4 Maximum deflection can be obtained as, 0.216 Ă—10004 5 đ?›żđ?‘šđ?‘Žđ?‘Ľ = Ă— 3 384 35 Ă—10 Ă—52083 All rights reserved by www.ijste.org
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đ?›żđ?‘šđ?‘Žđ?‘Ľ = 1.54 đ?‘šđ?‘š Comparing the deflections, đ?›żđ?‘šđ?‘Žđ?‘Ľ ≤ đ?›żđ?‘Žđ?‘™đ?‘™đ?‘œđ?‘¤đ?‘Žđ?‘?đ?‘™đ?‘’ Now, the deflection of bearing bar is within the permissible limit under given loading conditions.
Fig. 2: Composite Grating Drawing
III. FABRICATION OF GRATING For fabrication of composite grating, combination of fibers and matrix shall be used. Glass fiber reinforcement with Epoxy resin is used as major constituents. Continuous Fibre Reinforced Plastic (FRP) strings are used as reinforcement. In preparation of matrix two solution are used namely resin and hardener. First the sufficiently thin layer of gelcoat is applied on the mould. The FRP strings are arranged in two handles from opposite ends. Two operators lay down the strings in zig-zag manner overlapping each other inside the square mesh grooves provided on the mould surface. Matrix is then applied on this reinforcement by hand brush. Then air is removed by pressing the laminate b y metal plate.
Fig. 3: Mould for Composite Grating
Same process is repeated several times until the desired thickness of grating plate is achieved. After applying matrix the arrangement is kept to dry at least for next 24 hours as the curing time of this matrix is 24 hrs. After this curing, the grating plate is removed from mould by manual hammering. The grating plate is then deburred by portable electric operated grinding machine. The ends of grating plates are trimmed by portable cutting machine to obtain desired outer dimensions.
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Design and Experimental Analysis of Composite Grating (IJSTE/ Volume 3 / Issue 06 / 030)
Fig. 4: Measurement of Composite Grating
IV. EXPERIMENTAL VALIDATION AND RESULTS Composite grating plate is analysed against pre-defined load conditions by using Universal Testing machine. Experimental Procedure 1) 2) 3) 4) 5) 6) 7)
Arrange grating with help of fixture on the base of machine. Adjust the actuator on the center of grating with loading plate. Arrange the strain gauges on both side of grating. Start the machine & apply the load of 5400 N on center of grating. Record the reading of load, deflection & stress. Store the data in computer to generate the graph of load Vs deflection & stress. Release the load, so that actuator moves in original position. Sr. No. 1 2 3 4 5 6 7
Table – 3 Observation Table for UTM Readings Description Min Max Flat Thickness, mm Span Length, mm Span Width, mm Grating Area, m2 Applied Load, kN Shear Stress, kN/m2 192 X 10^3 Deflection, mm 2.5
Set 1 5 1000 1000 1 5.4 538 2.3
Set 2 5 1000 1000 1 5.5 537 2.7
Results from Experimental Analysis The results obtained in analytical design calculations and experimental testing for composite grating are summarized below. Sr. No. 1 2 3
Table - 4 Test Results for Composite Grating Result Description Analytical Calculations Total Load Applied on Grating, N 5400 Deflection due to loading, mm 1.54 Induced shear force, kN/m2 432
Experimental Testing 5400 2.3 538
1) The weight of the composite grating for equivalent area and strength is 13.8 kg as compared to 24.5 kg of metallic grating. This will have a significant impact on the supporting structural design. 2) The composite grating is limited to use for ambient temperature conditions only. Use of grating at elevated temperatures i.e. above 60 degree has direct impact on the strength of the plates. 3) Since the composite grating is completely made of non-corrosive substances, it is purely corrosion resistance. This gives advantage over metallic grating which needs galvanizing treatment before using in saline atmosphere. 4) The grating is giving 2.3 mm deflection when loaded with 5400 N. However this deflection is within acceptable limit of 2.5 mm. 5) The flexibility of composite grating absorbs the shock or impact loads which metallic grating cannot absorb and will bend permanently. 6) FRP Composite is purely non-conductive in nature and hence the grating can be used for electrical machinery platforms where metallic grating cannot be used for safety reasons. All rights reserved by www.ijste.org
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Design and Experimental Analysis of Composite Grating (IJSTE/ Volume 3 / Issue 06 / 030)
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