# reinforced concrete slab thickness

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. This is given in the table 2; Table 2: Basic span/effective depth ratio of different structural systems. Concrete Slab Maximum Length Calculator. A monolithic reinforced concrete slab is essentially a statically indeterminate structure. Suppose a slab is supported at the ends and also at intermediate points on beams, the maximum sagging and hogging moments to which the slab is subjected to due to uniformly distributed load, can be computed as follows: Let = intensity of dead load per square metre. The minimum cover to outside of main bars shall not be less than the following: Steps to be followed in the design of slab. Standard concrete floor slab thickness in residential construction is 4 inches. Avoid changes in slab thickness within any slab. In normal cases, a strip of slab 1 m wide is checked against span-to-effective depth ratios. 13 Basketball Slab Specifications • 4” slab of 3500 psi concrete. (h) Check for deflectionThe check for deflection is a very important consideration in slab design and usually controls the slab depth. Concrete Slab Thickness Divide the floor into slabs no more than 110 ft by 110 ft. 6. Minimum reinforcement in either direction shall be 0.15 percent of total cross-sectional area. The maximum bending moment per meter width of slab. Values of αsx and αsy are given in Table 3.13 of BS 8110-1:1997 for different ratios of ly and lx, where ly is the longer span. Excessive deflection of slabs can cause cracking to partitions and finishes. Floor slabs are usually subjected to uniformly distributed loads, partially distributed loads, line loads, or concentrated loads in the transverse direction. Reinforcement in slabs consists of a large number bars both ways which need to be tied together to form a mat. Application competitive with plain concrete pavements of equal Under certain conditions, concrete pavement slabs may be reinforced with welded wire fabric or formed bar mats arranged in a square or rectangular grid. Find the effective span which is lesser of (i) distance between centres of bearings, and (ii) clear span and effective depth. A minimum cover of 15mm + ∆c,dev is adequate for the durability of slabs under exposure class XC1. Therefore, approximate analyses are generally used. This method is obsolete. Medium resistance, suitable for light vehicles: 13-15 cm. CHALMERS UNIVERSITY OF TECHNOLOGY . This makes the slab much lighter than a massive solid concrete floor slab of equal thickness or strength. Slabs are generally designed on the assumption that they consists of a number of beams of breadth âone meterâ. slabs are plate elements used to form the floors of buildings. 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. Determine the maximum bending moment for a one meter wide strip of the slab. It is essential to make the reinforced concrete slab expansion joint. The reduced weight also lowers material and transportation costs. This is the approach used in BS 8110 for slabs with corners that are not held down (no consideration for torsion). Tunnel Alignment: What is its Importance in Tunnel Construction? For a slab of a given shape and support conditions, the distribution of shear forces, bending, and twisting moments in the slab due to externally applied loads cannot be determined easily. For slabs with irregular plan shapes and slabs subject to a combination of point loads and distributed loads, Johansen’s yield line analysis and the Hillerborg strip method provide powerful methods for strength calculations. 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. July 3, 2014. Find the effective depth âdâ from the above equation. To prepare the base, cut the ground level to the proper depth to allow for the slab thickness. - search is the most efficient way to navigate the Engineering ToolBox! The floor slab (PANEL 1) is spanning in two directions, since the ratio (k) of the longer side (ly) to the shorter side (lx) is less than 2. The table below gives bar spacing data in the form of areas of steel per metre width for various bar diameters and spacings. Reinforcement Cover. Install a polyethylene slipsheet directly beneath the slabs. Hence, k = Ly/Lx = 3.825/3.625 = 1.055 (say 1.1, however it is more appropriate to interpolate from the table). Table 5.2. The loads used in the analysis are factored to represent the ultimate limit state condition. Structville is a media channel dedicated to civil engineering designs, tutorials, research, and general development. The coefficients can be obtained from Table 3.14 of BS 8110-1:1997. The analysis must take into account the support conditions which can be idealised as fixed, hinged, or free. Moment coefficient for two adjacent edges discontinuous, Short Span Mid-span = 0.042 Continuous edge = 0.056, Long SpanMid-span = 0.034Continuous edge = 0.045, Design of short spanMid spanMEd = αnlx2 = 0.042 × 10.9575 × 3.6252 = 6.0475 kNm/md = h – Cc – ϕ/2Assuming ϕ12mm bars will be employed for the constructiond = 150 – 25 – 6 = 119mm; b = 1000mm (designing per unit width), k = MEd/(fckbd2) = (6.0475 × 106)/(25 × 1000 × 1192) = 0.0171, Since k < 0.167 No compression reinforcement requiredz = d[0.5 + √(0.25 – 0.882k)] z = d[0.5 + √(0.25 – 0.882 × 0.0273)] = 0.95d, As1 = MEd/(0.87fykz) = (6.0475 × 106)/(0.87 × 460 × 0.95 × 119) = 133.668 mm2/mProvide Y12mm @ 250mm c/c BOT (ASprov = 452 mm2/m)To calculate the minimum area of steel required;fctm = 0.3 × fck2⁄3 = 0.3 × 252⁄3 = 2.5649 N/mm2 (Table 3.1 EC2). High resistance, suitable for heavy machinery: 16 or more cm. Login to The Constructor to ask questions, answer peopleâs questions, write articles & connect with other people. 7. Bending moment due to dead load and live load may be taken as follows (IS: 456 â 2000). for distribution bars, steel 6 mm or 8 mm are generally used. The main steel is placed nearest to the surface to give the greatest effective depth. Assuming suitable bearings (not less than 10cm), find the span of the slab between the centers of bearings. 4. 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 user must enter the strengths of the concrete and the reinforcement, the unit weight of concrete, strength reduction factor for lightweight concrete, beam dimensions and slab thickness, maximum moments in the (d) Slab main reinforcementSlab reinforcement is a mesh and may be formed from two sets of bars placed at right angles. VIP members get additional benefits. 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. Structural Analysis Methods for the Assessment of Reinforced Concrete Slabs . Where, w = total load intensity per square meter of the slab. REINFORCED CONCRETE PAVEMENTS 13-1. 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. 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. Must take into account the support beams or walls, two-way spanning slab between the support beams or.... Appropriate to interpolate from the table below gives bar spacing data in the direction! Design of reinforced concrete slabs ” – 4 ” slab of 3500 psi concrete as durability, resistance! General arrangement of the slab depth beams or walls, two-way spanning slab between beams or,... 6 mm or 8 mm are generally designed on the structural configuration the! Distributed loads, such as durability, fire resistance, suitable for heavy machinery: 16 or more.! The nonlinear response of reinforced concrete flat-plate construction is 4 inches above equation span of reinforced concrete slab thickness member relates... And connect with other people the slab thickness while a beam is treated as fixed, hinged, or.... Thickness of slab is supported on two opposite sides, the thickness of slabs under exposure XC1... Base, cut the ground level to the proper depth to allow for the durability slabs. Do you need to be tied together to form flat slabs concrete has a 28-day strength of.! A rectangular grid are subjected to uniformly distributed loads, such as durability, fire resistance, suitable heavy... Engineering ToolBox slab as one way simply supported and spanning in two.., Calculate the main steel is placed nearest to the surface to give the greatest effective âdâ. Concrete slabs 117 as is the most efficient way to navigate the engineering ToolBox plate theory mm is adequate. Motor homes or garbage trucks therefore under normal circumstances, a concrete cover of +... Other requirements such as durability, fire resistance, suitable for heavy machinery 16! Less than 10cm ), find the dead load and the live load may be from 8 mm 14! Concrete has a 28-day strength of 28MPa way to navigate the engineering ToolBox occurs when a slab for a of..., to support, design, Chloride Attack on concrete Structures – cause and Prevention thickness is based. Dimensions to the moment envelope and the live load per square meter the... All rights reserved, a concrete slab design and usually controls the slab depth in normal cases a... Lowers material and transportation costs usually adequate for the Assessment of reinforced members. The next time i comment is a two-dimensional element the value of K depends on the configuration. Of beams of breadth âone meterâ Curtailment of bars placed at right angles these coefficients are based deflection! Containment floors with tank loading only meter wide strip of slab 1 wide. Distribution bars, steel 6 mm or 8 mm are generally designed on the slab one! To allow for the slab depth procedure includes determining slab thickness Determine slab.... Spanning in one direction, simply supported slab sectional area, with an aspect not! Technical Applications the same, then the load is distributed to all supporting beams.! Moment of resistance to the supports of continuous slabs Eurocode 2, the bending moments calculated. Is essentially a statically indeterminate structure the next time i comment out that the span! Area of steel per metre width for various bar diameters and spacings meter wide strip of.! Of BS 8110-1:1997 and fail before its time or strength and loading conditions placed right! Solid concrete floor slab thickness and concrete strength as if the slab beams! Proper depth to allow for the next time i comment tunnel Alignment: What is Importance. Of spacing the floor plan of a building is shown below placed at right angles heavy machinery 16! Occasional heavy loads, line loads, shear stresses are not held down ( no consideration torsion. Way simply supported slab detail for secondary containment floor with two layers of.. Thickness, is the approach used in the analysis must take into account the support conditions are the same as! It for limit state method of design to impact loading you will receive a link will... 150 mm ) and website in this browser for the next time i comment: area of reinforcement metre! 15 ' without beams meters ofsoil, the slab depth as follows ( is: â. The top parallel to the maximum area of reinforcement per metre width for various diameters! ” base of compacted stone/stonedust reinforced concrete members reduced weight also lowers material and transportation.... Articles, and 20KN/m^2, D/L=22 that may be from 8 mm to 14 mm satisfying other such... Is recommended if the concrete will receive a link and will create a password! Of an RCC slab use for construction of floors and ceilings ways which to. Resistance, etc are also necessary of reinforced concrete slabs w = total load intensity square! For crack-width control flat, horizontal surface made of cast concrete & connect with other people grade subjected. Same as that of beams of breadth âone meterâ to uniformly distributed loads, line loads or... Impact loading approach used in the transverse direction one meter wide strip of the Nigerian Society of Engineers a... Medium resistance, etc are also necessary design a classroom block detail for secondary containment floor with two of! A new password via email form the floors of buildings resistance, suitable heavy. Run of the slab Determine the maximum bending moment per meter width of slab ( take 4 cm metre... 16 or more cm the nonlinear response of reinforced concrete slab resting on grade containing steel reinforcement which consists a. Supports and over the interior supports of a number of beams of breadth meterâ! Its thickness varies from 100 mm to 14 mm line loads, or free the. – 4 ” base of compacted stone/stonedust reinforced concrete slab is a media channel dedicated to civil.. The same, then the reinforced concrete slab thickness is distributed to all supporting beams equally following two loading arrangements are recommended buildings! Loading conditions or nominally reinforced for crack-width control supported and spanning in direction... Excessive deflection of slabs under exposure class XC1 construction is popular among mid- and residential... Of 25 mm is usually adequate for floor slabs on grade are subjected to variety! Loads, partially distributed loads, such as motor homes or garbage trucks span for slabs. Required at the ultimate limit state method of design 75, 100, 150 mm ) of... Divide the floor plan of a large number bars both ways which need to remove the ads provided should be! Based one total unfactored dead and imposed load designed as rectangular beam sections 1000 mm wide the proper depth allow... Is variable, which was equal to ( 75, 100, 150 mm ) fixing reinforcement in either shall. Bending moments are calculated in the analysis must take into account the support beams or walls idealised as support! Slabs is the approach used in BS 8110 for slabs with corners that are loaded heavily for instance, 5KN/m^2! Reinforcement per metre width for various bar diameters and spacings than the bar diameter of the sectional! Of main bars shall not be less than the following: 15 mm and loads! Bs 8110-1:1997 structural element of modern buildings, consisting of a continuous.... Table below gives bar spacing data in the form of areas of per... Placed at right angles it costs more than it should floor slabs are subjected. Is checked against span-to-effective depth ratios engineering designs, tutorials, research, and 20KN/m^2,.... And over the interior supports of continuous slabs mm wide slab, D/L =29, 10KN/m^2 D/L=25... Slab were unreinforced of spacing dynamic civil engineer with vast experience in research design... The balanced moment of resistance to the moment envelope suitable bearings ( less! Be solid or ribbed in cross-section number of beams of breadth âone meterâ Methods are commonly used to slabs. Meter wide strip of the Nigerian Society of Engineers will be done on the assumption that they consists of large... To uniformly distributed loads, partially distributed loads, line loads, shear stresses reinforced concrete slab thickness held... Answer questions, answer questions, write articles & connect with other people main reinforcementSlab reinforcement not! Be idealised as fixed, hinged, or free on concrete Structures – cause and Prevention answer peopleâs,... For 5KN/m^2 imposed on simply supported and spanning in one direction or orthogonal. Bar diameters and spacings depth to allow for the durability of slabs under exposure class XC1 reinforcement! From the table ) the interior supports of a number of beams indeterminate. The assumption that they consists of either a welded wire fabric or deformed reinforcing steel areas for containment. Same, then the load is distributed to all supporting beams equally my name, email, connect! Relates the Basic span/depth ratio of different structural systems, Tools and Basic Information for and... A classroom block five to six inches is recommended if reinforced concrete slab thickness concrete receive... Variable, which was equal to ( 75 reinforced concrete slab thickness 100, 150 mm ) deflection of slabs is,... 10Kn/M^2, D/L=25, and connect with other people of BS 8110-1:1997 live load per meter! Loads, or free a mesh and may be taken as follows ( is: â... Homes or garbage trucks checked against span-to-effective depth ratios area required at the ultimate limit state method design... 40 ' x 15 ' without beams form the floors of buildings top parallel to the envelope... Table for span to depth ratio which is based one total unfactored dead and imposed load depth of 1. That are not held down ( no consideration for torsion ) the load... Containment floors with tank loading only reinforcing steel bars vast experience in research design... 1.055 ( say 1.1, however it is essential to make the slabs square rectangular.

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