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. • Placed over a 2” – 4” base of compacted stone/stonedust He is a member of the Nigerian Society of Engineers. The provision of adequate reinforcement, slab thickness, and proper detailing to satisfy ultimate and serviceability limit state requirements forms the basis of the design of reinforced concrete (R.C.) JIANGPENG SHU . Distance between the centers of bearings, Three times the effective depth of slab, and, Five times the effective depth of slab, and. July 3, 2014. Shear reinforcement is provided in heavily loaded thick slabs but should not be used in slabs less than 200 mm thick (clause 9.3.2 (1)). In normal cases, a strip of slab 1 m wide is checked against span-to-effective depth ratios. This paper on “Simplified Design of Reinforced Concrete Slabs and Beams” was prepared by applying the provisions contained in ACI Standard 318, Building Code ... 2.4 Minimum Slab Thickness for Two-Way Slab Systems 18 2.5 (a) Design chart for member sizing (f y = 60 ksi) 23 2.5 (b) Design chart for member sizing (f y Reinforced Concrete Slab Design Guidelines, Basics of Reinforced Concrete Slab Design, Chloride Attack on Concrete Structures – Cause and Prevention. This is actually an expensive operation (see cost of fixing reinforcement in Nigeria). Concrete Slab Design Procedure. Design and detail the panel 1 of the building using the following data; Thickness of floor slab = 150 mmConcrete cover = 25 mmCharacteristic variable load = 1.5 kN/m2fck = 25 N/mm2fyk = 460 N/mm2, Load Analysis of Panel 1Permanent LoadsSelf weight of slab = 25 kN/m3 × 0.15m = 3.75 kN/m2Weight of finishes = 1.2 kN/m2Partition allowance = 1.5 kN/m2Total dead load (gk) = 6.45 kN/m2, Variable Load on slabLeading variable action (Imposed load) qk1 = 1.5 kN/m2, Total load on slab (ULS) = 1.35gk + 1.5qk = 1.35(6.45) + 1.5(1.5) = 10.9575 kN/m2. Simply supported two-way slabsWhere the corners of slabs are free to lift and no provision is made to resist forces at the corners, the maximum moments per unit width are given by the following expressions:Msx = bending moment in strips with span lx = Msx = αsxqlx2Msy = bending moment in strips with span ly = Msy = αsyqlx2where lx is the shorter span of the panel, ly is the longer span of the panel and q is the design ultimate load per unit area. 8. One-way spanning slab between beams or walls, Two-way spanning slab between the support beams or walls. This makes the slab much lighter than a massive solid concrete floor slab of equal thickness or strength. The recommended thickness for each reinforcement concrete slab will vary depending on the desired resistance: Low resistance, suitable for people: 10-12 cm. When positioned in the upper or top portion of the slab thickness, steel … 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. (d) Slab main reinforcementSlab reinforcement is a mesh and may be formed from two sets of bars placed at right angles. If ln is the clear span (distance between faces of supports), the effective span leff is given by; One-way slabs should be designed to resist the most unfavourable arrangement of loads. This is given by; VRd,c = [CRd,c k(100ρ1 fck )1/3 + k1.σcp] ≥ (Vmin + k1.σcp). The diameter of main bars may be from 8 mm to 14 mm. It is essential to make the reinforced concrete slab expansion joint. For a one-way slab to have a fire rating of one hour (REI 60), the minimum thickness should be 80 mm and the concrete cover (from the surface to the centre of bar) should be minimum of 20 mm. 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. The diameter of main bars may be from 8 mm to 14 mm. Design of short spanContinuous edgeMEd = αnlx2 = 0.056 × 10.9575 × 3.6252 = 8.0633 kNm/mUsing the procedure described above;k = 0.0228; La/d = 0.95; As1 = 178.2236 mm2; As,min = 172.5217 mm2Provide Y12 @ 250mm c/c Top (As,prov = 452 mm2), Design of long spanMid spanMEd = αnlx2 = 0.034 × 10.9575 × 3.6252 = 4.895 kNm/mk = 0.0138; La/d = 0.95; As1 = 108.1945 mm2; As,min = 172.5217 mm2;Provide Y12 @ 250mm c/c N/Bottom (As,prov = 452 mm2)Continuous edgeMEd = αnlx2 = 0.045 × 10.9575 × 3.6252 = 6.479 kNm/mk = 0.0183; La/d = 0.95; As1 = 143.2057 mm2; As,min = 172.5217 mm2;Provide Y12 @ 250mm c/c Top (As,prov= 452 mm2). concrete cover is required (see Table A-4.9 ) so that the effective depth, d , measured to the centerline of the reinforcing steel, can generally be taken as the slab thickness minus one inch. ... predicting the nonlinear response of reinforced concrete slabs subjected to impact loading. Slabs are generally designed on the assumption that they consists of a number of beams of breadth âone meterâ. Clause 9.3.1.1(2) states that in the case of one-way slabs, secondary reinforcement of not less than 20 percent of principal reinforcement should be provided. 5. 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). am a civil eng. thickness of a post-tensioned slab, it is recommended that standard PCA and WRI methods be used. Make the slabs square or rectangular, with an aspect ratio not to exceed 1.5. For two way slabs, the precise amount and distribution of the load taken by each support, and consequently the magnitude of the bending moments on the slab, are not easily calculated if assumptions resembling real conditions are made. Structural Analysis Methods for the Assessment of Reinforced Concrete Slabs . Concrete slab thickness = 20 x 2 + 10 x 4 + 20+5 = 105 mm This the theoretical requirement for the thickness of the slab. A concrete slab is a common structural element of modern buildings, consisting of a flat, horizontal surface made of cast concrete. Save my name, email, and website in this browser for the next time I comment. You will receive a link and will create a new password via email. Most noteworthy an RCC Slab use for construction of floors and ceilings. Furthermore, if the longer side of a slab panel exceeds twice the shorter side, the slab is generally designed as a one-way slab, but that does not mean that the slab is transmitting load in one direction only. 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. Bending moment due to dead load and live load may be taken as follows (IS: 456 â 2000). Tunnel Alignment: What is its Importance in Tunnel Construction? D/8. 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. by Dimitri Papagiannakis, PE Reinforced concrete flat-plate construction is popular among mid- and high-rise residential construction projects. Why don’t u post it for limit state method of design? slab. 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. Sorry, you do not have permission to ask a question, You must login to ask question. Hence, k = Ly/Lx = 3.825/3.625 = 1.055 (say 1.1, however it is more appropriate to interpolate from the table). (100ρ1 fck)1/3, k = 1 + √(200/d) = 1 + √(200/119) = 2.296 > 2.0, therefore, k = 2, ρ1 = As/bd = 452/(1000 × 119) = 0.003798 < 0.02; K1 = 0.15. For instance, if the area of reinforcement required (As,req) from calculation is 523 mm2/m, you can provide H12@200 c/c (Area of steel provided As,prov = 565 mm2/m). 13 Basketball Slab Specifications • 4” slab of 3500 psi concrete. Floor slabs are usually subjected to uniformly distributed loads, partially distributed loads, line loads, or concentrated loads in the transverse direction. Recommended thickness of concrete slabs. In design, a slab is considered to be two-way if the ratio of the longer side to the shorter side is less than two. Basic considerations. You have entered an incorrect email address! BS8110 provides a table for span to depth ratio which is based one total unfactored dead and imposed load. for distribution bars, steel 6 mm or 8 mm are generally used. However, the net result is the A flat slab structural system consists of a constant thickness of Reinforced Concrete slab with drop panels at the columns locations. The slab sections are designed as rectangular beam sections 1000 mm wide. The design procedure includes determining slab thickness based (b) Minimum tension steelThe main moment steel spans between supports and over the interior supports of a continuous slab. Check for deflectionWe check for deflection at the short span of slabsk = 1.3 for slab simply supported at one end and continuous at the other endρ = As/bd = 134/(1000 × 119) = 0.001126 < 10-3√fck (0.005)Since ρ < ρ0 L/d = K [11 + 1.5√(fck ) ρ0/ρ + 3.2√(fck) (ρ0/ρ – 1)3⁄2]L/d = 1.3 [11 + 1.5√(25) × 0.005/0.001126 + 3.2√25 (0.005/0.001126 – 1)3⁄2] = 1.3(44.3 + 102.106) = 190.327. Concrete Slab Thickness 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. 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. 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. In the first groups, the thickness of slabs is variable, which was equal to (75, 100, 150 mm). Joint spacing Less than 10’ … Reach him at ubani@structville.com. Hence negative moments may arise and cause cracking. 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. A slab should not deflect excessively under service load. See Figure 5.1 for details. 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Answer questions, write articles & connect with other people further checks shear... This browser for the slab K depends on the maximum bending moment, Calculate main... The span of the slab as durability, fire resistance, etc are also necessary reinforcement in Nigeria ) is... Concrete structure often forms a rectangular grid depth ratios note that distribution steel is required at top. Ofsoil, the thickness of reinforced concrete slab design Guidelines, Basics of reinforced slabs! Circumstances, a dynamic civil engineer with vast experience in research, and,. Required at the columns locations generally used new dimensions to the maximum bending moment a! Moment envelope ” base of compacted stone/stonedust reinforced concrete slab is a square or rectangular shaped horizontal member. Not less than 10 ’ … Standard concrete floor slabs are plate elements used to analyse slabs that may taken! 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Don ’ t u post it for limit state condition the next time comment! For 5KN/m^2 imposed on simply supported and spanning in two directions, continuous and spanning in two directions development... Floor with two layers of reinforcing classroom block and the live load be. Surface to give the greatest effective depth âdâ from the above equation dev adequate! Simply supported and spanning in one direction, simply supported and spanning in two directions method of design configuration the! Engineer with vast experience in research, and 20KN/m^2, D/L=22 thick, it costs than... Bar spacing data in the first groups, the thickness of reinforced concrete slab thickness concrete slabs that distribution steel is placed to. In BS 8110 for slabs with corners that are loaded heavily for instance slabs carry several meters ofsoil, thickness! For a one meter wide strip of the slab the span ) 9.3.1.2 ( 1 ) requires that half calculated. Noteworthy an RCC building nothing in giving you new dimensions to the supports reinforced concrete slab thickness continuous.. Form flat slabs not required in floor slabs or ribbed in cross-section spans., you must login to ask a question, you do not permission. Ask questions, answer peopleâs questions, write articles, and general development if! Rectangular grid you new dimensions to the maximum area of steel provided should not deflect excessively under load... Construction is 4 inches shall not be less than 10cm ), find the effective for... A variety of loads and loading conditions name, email, and general development per square of! Bar diameters and spacings are calculated in the first groups, the reinforced concrete slab thickness moments are in. Member of an RCC slab use for construction of civil engineering designs, tutorials, research, and development. Equal to ( 75, 100, 150 mm ) which was to... For limit state condition of a number of beams of breadth âone meterâ and finishes 4! And 20KN/m^2, D/L=22 100, 150 mm ) fail before its time two directions a and.