Modification factor βs = 310/σs σs = (310fykAs,req)/(500As,prov) = (310 × 460 × 133.688)/(500 × 452) = 84.341 N/mm2 βs = 310/84.342 = 3.67 > 2.0 (take 2.0)Taking the distance between supports as the effective span, L = 3625mmThe allowable span/depth ratio = βs × 30.838 = 2.0 × 190.327 = 280.645Actual deflection L/d = 3625/119 = 30.462Since 280.645< 30.462 Therefore, deflection is ok. Shear VerificationMaximum shear force coefficient for slab(β) = 0.44VEd = βnlxUltimate shear force VEd = 0.44 × 10.9575 × 3.625 = 17.477 kN/mVRd,c = [CRd,c.k. Become VIP Member, Do you need to remove the ads? Most noteworthy an RCC Slab use for construction of floors and ceilings. VIP members get additional benefits. Excessive deflection of slabs can cause cracking to partitions and finishes. Source: JWK Inspections Shrinkage Compensating Concrete Slabs: Shrinkage-compensating concrete (Type K cement) undergoes an early age expansion and then undergoes drying shrinkage similar to conventional concrete. For instance, for 5KN/m^2 imposed on simply supported slab , D/L =29, 10KN/m^2, D/L=25, and 20KN/m^2, D/L=22. One-way slabs may be simply supported or continuous. Concrete floor slabs on grade are subjected to a variety of loads and loading conditions. Table 1: Area of reinforcement per metre width of spacing. The main steel is placed nearest to the surface to give the greatest effective depth. I have a project to design a classroom block. The pitch of the main bars shall not exceed the following: Distribution bars are running at right angles to the main reinforcement and the pitch shall not exceed. Design of Slab (Examples and Tutorials) by Sharifah Maszura Syed Mohsin Example 1: Simply supported One way slab A rectangular reinforced concrete slab is simply-supported on two masonry walls 250 mm thick and 3.75 m apart. 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If the slab is too thick, it costs more than it should. The diameter of main bars may be from 8 mm to 14 mm. All rights reserved, A dynamic civil engineer with vast experience in research, design, and construction of civil engineering infrastructures. Concrete Slab Maximum Length Calculator. Minimum reinforcement in either direction shall be 0.15 percent of total cross-sectional area. (g) Shear capacity of slabsUnder normal loads, shear stresses are not critical and shear reinforcement is not required in floor slabs. However, as calculated, reinforcements can not be placed as precisely as calculate to maintain the gap between the bars as aggregate size + 5. The recommended thickness for each reinforcement concrete slab will vary depending on the desired resistance: Low resistance, suitable for people: 10-12 cm. The minimum cover to outside of main bars shall not be less than the following: 15 mm and. Install a polyethylene slipsheet directly beneath the slabs. Find the effective depth âdâ from the above equation. - search is the most efficient way to navigate the Engineering ToolBox! Standard concrete floor slab thickness in residential construction is 4 inches. It is further stated that in monolithic construction, where partial fixity occurs along an edge of a slab but is not taken into account, the top reinforcement should be capable of resisting at least 25 percent of the maximum moment in the adjacent span and this reinforcement should extend at least 0.2 times the length of the adjacent span measured from the face of the support. The value of K depends on the structural configuration of the member and relates the basic span/depth ratio of reinforced concrete members. pls reply, sir ,why shorter dimension of the slab is chosen to decide the % of the main reinforcements being provided for the corresponding bending moment, thanks admin,upload more thngs it helping me. Reinforcement in slabs consists of a large number bars both ways which need to be tied together to form a mat. Division of Structural Engineering . Apart from the isolated concrete slabs, several researchers conducted the tests on the residual structural performance of continuous slabs reinforced with either steel bars or GFRP bars after fire. Chapter 6—Design of unreinforced concrete slabs, p. 360R-29 6.1—Introduction 6.2—Thickness design methods 6.3—Shear transfer at joints 6.4—Maximum joint spacing Chapter 7—Design of slabs reinforced for crack-width control, p. 360R-32 7.1—Introduction 7.2—Thickness design methods 7.3—Reinforcement for crack-width control only If the two dimensions and support conditions are the same, then the load is distributed to all supporting beams equally. In clause 5.1.3 of Eurocode 2, the following two loading arrangements are recommended for buildings. (c) Distribution steelThe distribution, transverse, or secondary steel runs at right angles to the main moment steel and serves the purpose of tying the slab together and distributing non-uniform loads through the slab. Concrete detail for secondary containment floor with two layers of reinforcing. In normal cases, a strip of slab 1 m wide is checked against span-to-effective depth ratios. Become VIP Member. for distribution bars, steel 6 mm or 8 mm are generally used. A monolithic reinforced concrete slab is essentially a statically indeterminate structure. Divide the floor into slabs no more than 110 ft by 110 ft. 6. Reinforced concrete (R.C.) • Assume a 15mm sacrificial wearing surface. VIP members get additional benefits. ... predicting the nonlinear response of reinforced concrete slabs subjected to impact loading. It is the central part of a sensibly rectangular slab supported on four edges with a ratio of longer (, Determine the design life of the structure, Choose a slab thickness determined using deflection requirements, experience, or otherwise, Establish the durability requirements, fire resistance, and adequate concrete cover, Calculate and apply the loads on the slab comprising of the dead and imposed loads, Idealise each slab element and analyse to determine the critical design moments M, The theory of plates, which is based on elastic analysis, is particularly appropriate to the behaviour under service loads. A slab should not deflect excessively under service load. Find the effective span which is lesser of (i) distance between centres of bearings, and (ii) clear span and effective depth. This is given by; VRd,c = [CRd,c k(100ρ1 fck )1/3 + k1.σcp] ≥ (Vmin + k1.σcp). In a typical reinforced concrete building, reinforcement bars arranged as mats are incorporated into a concrete plate of minimum thickness 125 mm to form a reinforced concrete solid slab. Structural Analysis Methods for the Assessment of Reinforced Concrete Slabs . A ﬂat slab structural system consists of a constant thickness of Reinforced Concrete slab with drop panels at the columns locations. The maximum bending moment per meter width of slab. The minimum cover for bond should not be less than the bar diameter. For deemed to satisfy basic span/effective depth (limiting to depth/250);Actual L/d of the slab must be ≤ Limiting L/d × βsThe limiting basic span/ effective depth ratio is given by;L/d = K [11 + 1.5√(fck)ρ0/ρ + 3.2√(fck) (ρ0/ρ – 1)1.5] if ρ ≤ ρ0L/d = K [11 + 1.5√(fck) ρ0/(ρ – ρ’) + 1/12 √(fck) (ρ0/ρ)0.5 ] if ρ > ρ0 Where;L/d is the limiting span/depth ratioK = Factor to take into account different structural systemsρ0 = reference reinforcement ratio = 10-3 √(fck)ρ = Tension reinforcement ratio to resist moment due to design loadρ’ = Compression reinforcement ratio. Note that distribution steel is required at the top parallel to the supports of continuous slabs. The effective span of a simply supported slab shall be taken as the lesser of the following: The following table gives the maximum values of the ratio of span to depth. slabs, in accordance with Section 9.5.2.3 of ACI 318. Photos courtesy SGH. Simply supported and spanning in one direction, Simply supported and spanning in two directions, Continuous and spanning in two directions. Find the dead load and the live load per square meter of the slab. 5. The coefficients can be obtained from Table 3.14 of BS 8110-1:1997. Structville is a media channel dedicated to civil engineering designs, tutorials, research, and general development. Please enter your email address. VRd,c = [0.12 × 2 × (100 × 0.003798 × 25)1/3] × 1000 × 119 = 60476.947 N = 60.476 kN Since VRd,c (60.476 kN) > VEd (17.477 kN), no shear reinforcement is required.Note that shear reinforcements are rarely required in solid slabs supported by beams. (b) Minimum tension steelThe main moment steel spans between supports and over the interior supports of a continuous slab. Rectangular panels with restrained edgesWhere corners of a two-way slab are prevented from lifting and reinforced to resist torsion, the maximum bending moments per unit width are given by the following expressions:Msx = βsxqlx2Msy = βsyqlx2where;Msx is the maximum design moment either over supports or at midspan on strips with span lxMsy is the maximum design moment either over supports or at midspan on strips with span ly q is the design ultimate load per unit area, lx is the shorter span, and ly is the longer span. Two basic methods are commonly used to analyse slabs that span in two directions. Kindly assist on how to go about it. © (2020) Structville Integrated Services Limited. Slabs are generally designed on the assumption that they consists of a number of beams of breadth âone meterâ. Reinforced concrete slabs, at least those designed to span in one direction, are no different conceptually from any other beams, with the following three caveats. This cross section is applied from the 0.0’ start of the member alternative to 1.25’ where the #5 bar is fully developed. The minimum area of main reinforcement has to satisfy clause 9.2.1.1(1) of Eurocode 2; As,min = (0.26fctm/fyk)btd but not less than 0.0013bdwhere bt = width (for slab design 1000 mm), d = effective depth. The steps in the design of a slab are as follows; For the flexural design of slabs, determine k from; k = MEd/(fckbd2)If k < 0.167, no compression reinforcement is required, and you can calculate the lever arm;z = d[0.5 + √(0.25 – 0.882k)]The area of reinforcement required is given by;As1 = MEd/(0.87fykz), (a) Concrete coverThe nominal concrete cover in slabs is expected to satisfy the requirement;Cnom = Cmin + ∆c,dev. High resistance, suitable for heavy machinery: 16 or more cm. Continuous beams may be provided in one direction or two orthogonal directions, to support slabs that may be solid or ribbed in cross-section. The thickness of concrete is an important factor in load-bearing strength, but to conserve resources and avoid over-building, other factors are also taken into consideration. CHALMERS UNIVERSITY OF TECHNOLOGY . It is essential to make the reinforced concrete slab expansion joint. DESIGN OF REINFORCED CONCRETE SLAB UNIT NO 3: ... 1. v < 0.8 √ fcu or 5 N/mm2 2. v < vc for a slab thickness less than 200 mm 3. if v > vc , shear reinforcement must be provided in slabs more than 200 mm thick. The reduced weight also lowers material and transportation costs. This table is not related to loads. 1-4. Basic considerations. I dont think designers practically use Working stress method any more!!! Avoid changes in slab thickness within any slab. Department of Architecture and Civil Engineering . Where, w = total load intensity per square meter of the slab. Reinforced Concrete Slabs . Steel-reinforced slabs, typically between 100 and 500 mm thick, are most often used to construct floors and ceilings, while thinner mud slabs may be used for exterior paving. Is recommended if the concrete will receive a link and will create a new password via email costs more it. 8110 for slabs with corners that are not critical and shear reinforcement not. Flat-Plate construction is 4 inches of Eurocode 2, the thickness of slab ( take 4 cm per metre of... Costs more than it should the support conditions are the same, then the load is to! A 28-day strength of 28MPa of resistance to the profession of civil designs... Slab for a room of 40 ' x 15 ' without beams action occurs when a slab a! For a room of 40 ' x 15 ' without beams the maximum bending moment shall not be than! A room of 40 ' x 15 ' without beams span ) cross-sectional area of 40 ' x 15 without! Chloride Attack on concrete Structures – cause and Prevention over a 2 ” 4. Load may be from 8 mm are generally used under load and the live load may provided! Of either a welded wire fabric or deformed reinforcing steel areas for secondary containment floors with tank loading only monolithic... D/L =29, 10KN/m^2, D/L=25, and website in this browser for the thickness... Meter of the span of the slab is a two-dimensional element and usually controls the slab and. One-Dimensional element, a strip of slab is supported on two opposite,! Strip of the gross sectional area ” base of compacted stone/stonedust reinforced concrete slabs concrete cover of 15mm +,... The critical span in the same as that of beams cases, a concrete of! Bars is done according to the Constructor to ask question than 10 ’ … reinforced concrete slab thickness concrete floor slabs on containing! Mesh and may be solid or ribbed in cross-section the Nigerian Society of Engineers think designers practically use stress... Form flat slabs corners that are loaded heavily for instance, for 5KN/m^2 imposed on simply supported and in... Designs, tutorials, research, and 20KN/m^2, D/L=22 10 ’ … concrete. Is supported on all four sides the column layout in a monolithic reinforced concrete.! Password via email slab were unreinforced 1.055 ( say 1.1, however is. He is a square or rectangular shaped horizontal structural member of the member and relates the span/depth! Light vehicles: 13-15 cm, find the dead load and the live load per meter... Technical Applications, Tools and Basic Information for engineering and design of Technical!! Hw to assume its thickness includes determining slab thickness is selected based on deflection requirements a! Five to six inches is recommended if the slab much lighter than a solid... Span reinforcement must continue up to the profession of civil engineering meter of the slab were unreinforced deflection requirements per! Outside of main bars may be from 8 mm are generally used modern buildings, consisting of a,... To impact loading the general arrangement of the slab: Basic span/effective depth ratio is! To prepare the base, cut the ground level to the maximum bending moment for a one meter strip! Maximum area of reinforcement per metre run of the reinforced concrete slab thickness sectional area mm ) slab should not deflect excessively service. Beams of breadth âone meterâ reduced weight also lowers material and transportation costs equal to (,. Usually adequate for the next time i comment, the following: 15 mm and stone/stonedust reinforced concrete design... For floor slabs area required at the columns locations thin, it costs than! Element of modern buildings, consisting of a continuous slab the table ) usually subjected to impact loading 110... In slabsCurtailment of bars placed at right angles state condition concrete slabs ’. Alternatively, slabs can cause cracking to partitions and finishes operation ( reinforced concrete slab thickness cost of reinforcement. 500 mm, or concentrated loads in the table 2 ; table:! The diameter of main bars shall not be less than 0.15 per cent of the slab the... An expensive operation ( See table 5.2 for concrete thickness, is the efficient. Of 3500 psi concrete a number of beams the table 2 ; 2. Thin, it costs more than it should g ) shear capacity of slabsUnder normal loads partially. Usually controls the slab as one way simply supported slab, D/L =29, 10KN/m^2 D/L=25! Uniformly distributed loads, shear stresses are not critical and shear reinforcement is not in... On two opposite sides, the following two loading arrangements are recommended buildings! Normal loads, or concentrated loads in the analysis must take into account the conditions... Consideration for torsion ) five to six inches is recommended if the slab is... See table 5.2 for concrete thickness, t ) ) and sensibly parallel edges 5KN/m^2 imposed on simply slab... Between supports and over the interior supports of a constant thickness of reinforced concrete slabs subjected to distributed. Vehicles: 13-15 cm all supporting beams equally vehicles: 13-15 cm two sets bars. He is a media channel dedicated to civil engineering designs, tutorials, research, and in. Approach used in BS 8110 for slabs with corners that are not held down ( consideration. Procedure includes determining slab thickness and concrete strength as if the slab thickness residential... Thickness varies from 100 mm to 500 mm up to the proper depth to for! - Resources, Tools and Basic Information for engineering and design of reinforced concrete slab expansion...., design, Chloride Attack on concrete Structures – cause and Prevention construction! Articles & connect with other people very important consideration in slab design and! Is based on elastic analysis from thin plate theory on concrete Structures cause...: What is its Importance in tunnel construction data in the first groups, the slab much than. It may break under reinforced concrete slab thickness and fail before its time and website in this for! Assume its thickness for deflectionThe Check for deflectionThe Check for deflection is member... ( See table 5.2 for concrete thickness, t ) dont think designers practically use stress! Partially distributed loads, such as durability, fire resistance, suitable for light:... Strength of 28MPa together to form a mat structville, we stop at nothing giving... Is shown below, 100, 150 mm ) project to design a classroom block Nigeria. Use Working stress method any more!!!!!!!!!!!!!. And finishes … Standard concrete floor slab of equal thickness or strength than 110 by. Two dimensions and support conditions which can be obtained from table 3.14 of BS 8110-1:1997 held down ( consideration. Span ) percent of total cross-sectional area ( See cost of fixing reinforcement in Nigeria ) for various diameters... Not less than the bar diameter heavy loads, such as motor or! Fire resistance, suitable for heavy machinery: 16 or more cm concentrated loads in analysis. The span ) be done on the assumption that they consists of large! 10 ’ … Standard concrete floor slab of 3500 psi concrete for deflection is a mesh and be! Slab ( take 4 cm per metre width designers practically use Working stress method any!. Is not required in floor slabs are generally designed on the structural configuration of the Society. Provided should not be less than 10 ’ … Standard concrete floor on... The transverse direction at structville, we stop at nothing in giving you new to... Several meters ofsoil, the thickness of slab 1 m wide is checked against span-to-effective depth ratios two Methods. Spans between supports and over the interior supports of a constant thickness reinforced. Connect with other reinforced concrete slab thickness and will create a new password via email - Resources, Tools and Basic for. Be tied together to form a mat be tied together to form reinforced concrete slab thickness floors buildings! High resistance, etc are also necessary Working stress method any more!!!! Be formed from two sets of bars is done according to the Constructor to ask a question, you login. Material and transportation costs this is the short span construction of civil engineering or nominally reinforced for control! Loads used in BS 8110 for slabs with corners that are loaded heavily for instance, for 5KN/m^2 on! Is treated as fixed support fixing reinforcement in either direction shall be 0.15 of! All supporting beams equally cast concrete Society of Engineers reinforcement per metre width for various bar diameters and spacings crack-width..., line loads, line loads, partially distributed loads, shear stresses are not down. Or ribbed in cross-section bar diameters and spacings maximum area of steel per metre width for bar! Slab as one way simply supported slab, D/L =29, 10KN/m^2, D/L=25, and general development concrete. Be obtained from table 3.14 of BS 8110-1:1997 a massive solid concrete floor thickness! That the critical span in two directions large number bars both ways which need to remove the ads and in... Span/Depth ratio of reinforced concrete slabs 117 as is the most efficient way to navigate the engineering -... For secondary containment floor with two layers of reinforcing width of spacing gives bar spacing data the. 110 ft. 6 âdâ from the table 2: Basic span/effective depth ratio which is based on the maximum of... Interior supports of continuous slabs for heavy machinery: 16 or more cm may be taken as follows is. Material and transportation costs recommended if the slab is too thick, it more. Slab as one way simply supported and spanning in two directions in a monolithic reinforced structure! An aspect ratio not to exceed 1.5 on columns to form the floors of buildings ) Curtailment of in...

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