JIANGPENG SHU . The coefficients can be obtained from Table 3.14 of BS 8110-1:1997. Continuous beams may be provided in one direction or two orthogonal directions, to support slabs that may be solid or ribbed in cross-section. 8. 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 value of K depends on the structural configuration of the member and relates the basic span/depth ratio of reinforced concrete members. Structville is a media channel dedicated to civil engineering designs, tutorials, research, and general development. (d) Slab main reinforcementSlab reinforcement is a mesh and may be formed from two sets of bars placed at right angles. for distribution bars, steel 6 mm or 8 mm are generally used. See Figure 5.1 for details. Find the dead load and the live load per square meter of the slab. The column layout in a monolithic reinforced concrete structure often forms a rectangular grid. Tunnel Alignment: What is its Importance in Tunnel Construction? 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. The minimum cover for bond should not be less than the bar diameter. Find the effective span which is lesser of (i) distance between centres of bearings, and (ii) clear span and effective depth. A beam is similar to a slab in so many ways but there are fundamental differences in behaviour and stress distribution of the two elements. 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.) 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)). This cross section is applied from the 0.0’ start of the member alternative to 1.25’ where the #5 bar is fully developed. Hence no further checks for shear will be done on the slab. In earlier years, column capitals were used along with drop panels, but because of the higher formwork cost, column capitals are less favored in today’s construction practice. The diameter of main bars may be from 8 mm to 14 mm. 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. Design the slab as one way simply supported slab. 4. 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. 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. 5. It is essential to make the reinforced concrete slab expansion joint. thickness of a post-tensioned slab, it is recommended that standard PCA and WRI methods be used. Slabs may be simply supported or continuous over one or more supports and are classified according to the method of support as follows: Clause 5.3.1(5) of EN 1992-1-1:2004 suggests that a slab subjected dominantly to uniformly distributed loads may be considered as one-way spanning if either: In other words, when beams are provided in one parallel direction only, the slab is a one-way slab. The maximum bending moment per meter width of slab. Concrete Slab Maximum Length Calculator. Slab thickness and reinforcing steel areas for secondary containment floors with tank loading only. Division of Structural Engineering . 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. 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 effective span for one-way slabs is the same as that of beams. = intensity of live load per square metre. The advantages of using steel reinforcement include a reduction in the required slab thickness, CHALMERS UNIVERSITY OF TECHNOLOGY . (h) Check for deflectionThe check for deflection is a very important consideration in slab design and usually controls the slab depth. To check the shear capacity of slabs, the shear stress (vEd = VEd/bd) must be checked against the shear capacity of an unreinforced section (VRc,d). Continuity across a beam is treated as fixed support. Install a polyethylene slipsheet directly beneath the 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. 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. Assume the thickness of slab (take 4 cm per metre run of the span). slab. 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. 5. This is the approach used in BS 8110 for slabs with corners that are not held down (no consideration for torsion). It is necessary to point out that the critical span in the analysis of solid slabs is the short span. Reinforced Cement Concrete slab is a square or rectangular shaped horizontal structural member of an RCC building. It possesses two free (unsupported) and sensibly parallel edges. Reinforced concrete (R.C.) If the two dimensions and support conditions are the same, then the load is distributed to all supporting beams equally. One-way spanning slab between beams or walls, Two-way spanning slab between the support beams or walls. 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. As far as the author is aware, reinforced concrete slabs designed to the span/depth rules in the current BS 8110 [2] and its predecessors have generally performed acceptably in service. 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. 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. While a beam is generically a one-dimensional element, a plate is a two-dimensional element. This is given in the table 2; Table 2: Basic span/effective depth ratio of different structural systems. VIP members get additional benefits. Kindly assist on how to go about it. The minimum cover to outside of main bars shall not be less than the following: Steps to be followed in the design of slab. Two-way action occurs when a slab is supported on all four sides. Concrete floor slabs on grade are subjected to a variety of loads and loading conditions. The maximum area of steel provided should not exceed 0.04Ac. 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 The table below gives bar spacing data in the form of areas of steel per metre width for various bar diameters and spacings. Evaluating slab thickness in reinforced concrete flat-plate construction. Sorry, you do not have permission to ask a question, You must login to ask question. However, clause 9.3.1.2(1) requires that half the calculated span reinforcement must continue up to support. (b) Minimum tension steelThe main moment steel spans between supports and over the interior supports of a continuous slab. The recommended thickness for each reinforcement concrete slab will vary depending on the desired resistance: Low resistance, suitable for people: 10-12 cm. Most noteworthy an RCC Slab use for construction of floors and ceilings. Student. Therefore under normal circumstances, a concrete cover of 25 mm is usually adequate for floor slabs. 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. Country • The slab is cast-in-place and water cured. • Full depth diaphragms are used at lines of supports • Slab and girders are made composite • Traffic barriers are composite and structurally continuous with the overhang Simply supported and spanning in one direction, Simply supported and spanning in two directions, Continuous and spanning in two directions. The main steel is placed nearest to the surface to give the greatest effective depth. Table 1: Area of reinforcement per metre width of spacing. For one-way slabs supported on two opposite sides, the bending moments are calculated in the same way as for beams. 7. 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. VIP members get additional benefits. Reinforced Concrete Slabs . 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