2. m. For continuous slabs, curtail or bent up the +ve steel. slab thickness. Two Way Waffle Slab (with Integral Beams), Flooding Irrigation | Types of Flooding Irrigation | Wild Flooding | Controlled Flooding, Total Station in Surveying | Parts of Total Station | Operation of Total Station | Uses of Total Station. In other words, it can be said that, two-way slabs span in both directions. Slab carries the loads imposed on it and duly transfers the forces either in a one way or in a two-way mechanism. The load is carried in both directions in a two-way slab. In two way slab the corners may be held down by restraints or may be allowed to lift up. Design Considerations: One Way Slab 1. e. Determine total factored load per unit strip (kN/m). b. The slab is the horizontal structural component that provides a flat and purposive surface. For the panel sizes up to 6m x 6m two-way slab is suitable and economical. One way slab being supported on two opposite sides only leads to the structural action in single direction. One way slabs are such slabs in which the loads are shared only by the shorter direction of the slab. Figure: Two way slab (a) Bending of center strip, (b) grid model Figure: Moment variations of a uniformly loaded slab with simple supports on four sides. If it has edge beams it is a 25*12 two way slab. The ratio of longer span (l) to shorter span (b) is equal or greater than 2, considered as One-way slab. Continuity across a beam is treated as fixed support. how to calculate load on beam from slab. 2. The proposed slab system must be able to be constructed at a reasonable cost. Two-way slabs are extensively used in the multi-storey and commercial buildings. Flexural Reinforcement must be greater than 0.0018 psi or the shrinkage reinforcement. The thickness of the slab is generally based on deflection control criteria, and the reinforcements in the two orthogonal directions are designed to resist the calculated maximum bending moments in the respective directions at the critical sections. For continuous slabs, hogging reinforcements are provided at top over supports and bottom bars are curtailed. A slab or panel is said to be two way slab if the ratio of longer span to the shorter span is not greater than 2 (two). Unlike, one way slabs, in case of two way slabs, reinforcement in both the directions are structural design reinforcements. 8 CHAPTER 8: DESIGN OF ONE-WAY SLABS 8.1 Introduction A slab is structural element whose thickness is small compared to its own length and width. In above figure (a) represents one way slab. Types of Two Way Slab There are multiple analysis methods, manual and computer analysis, available for analyzing two-way slabs. Design reinforcement will be Bottom reinforcement and is provided in shorter direction. Beam and slab arrangement can be the best example for one way and two way slabs. The major functions of the slab can be listed as follows: a. Slab serves as a flat surface or a walking surface. Comparison of One-way and Two-way slab behavior Economic Choices One-way Slab on beams suitable span 3 to 6m with LL= 3-5KN/m2. When a reinforced concrete slab is supported by beams on all the four sides and the loads are carried by the supports along with both directions, it is known as two way slab. Provide the remaining amount of steel. Yes, this is possible. You cannot tell it that it will be anything else. Dead Load = Load per unit area x 1m width. While the distribution bars are provided on the longer side. Conclusion: In the case of two-way slab it has been found in practice that a huge moment develops at the support i.e. equivalent one metre wide beam with the same span and support conditions as the one-way slab. Also, check if the thickness is sufficient for shear. Hence, one way slabs have ratio between longer to shorter span greater than 2. Additional torsion reinforcement is required at corners when it is restrained against uplifting as shown in Fig.3.1 Thickness of the slab is decided based on span to depth ratio specified in IS456-2000. Prepare bar bending schedule in necessary conditions. 7. 200 blocks/h. Find out the maximum (-ve) factored moment (kN.m/m) for case 2 panel, short direction. More availability of the height of the room. One-way and Two-way Slabs One-way slabs transfer the imposed loads in one direction only. Using the above-explained method, binding moments can be found in each case. The maximum shear force is at support, equal to wl/2 The maximum deflection is at mid-span, equal to wl⁴/ 3.84EI. TWO- WAY SLAB: This type of slab has support from all four sides. Precast concrete structures solved a one way solid concrete slab l1009 optimized thickness of slabs according longitudinal reinforcement strength Beam And Block Load Span Tables Stressline LimitedFlat Slab Maximum Span … Decide its diameter & spacing. Here, moments and shear forces are directly calculated by multiplying load with a coefficient based on panel support conditions and span ratios. The walls on either sides, equally shares the self weight of the slab. The depth of beam depends on, beam is primary or secondary. As shown in the figure above, in the one-way slab, the main bars (cranked bars) are provided on the shorter side. Maximum moment of simply supported slab is at mid-span under self weight and uniform pressure loads. section 9.5, the deflection specifications for two-way slabs. It may be supported by reinforced concrete beam, by masonry wall or directly by column.Difference between one way and two way slab are as follows. According to ACI Code 7.12.2.1, for the shrinkage and temperature reinforcement, Slabs with grade 40 or 50 deformed bars = 0.0020 psi, Slabs with grade 60 deformed bars = 0.0018 psi, Slabs with reinforcements having yield strength greater than 60000 psi = (0.0018 x 60,000/ fy). Discussion of results (a) Two-way slab systems (1) In the long span direction, finite element analysis and yield line method gave very close results for bending moment and shear forces. According to ADOSS, the interior spans due not meet the code requirements to neglect deflection. According to it, if a slab rests on its support freely, the span length may be taken as equal to the clear span plus the depth of the slab but need not exceed the distance between the centres of supports. In clause 5.1.3 of Eurocode 2, the following two loading arrangements are recommended for buildings.. Alternate spans carrying (γ G G k + γ Q Q k) other spans carrying only γ G G k.; Any two adjacent spans carrying (γ G G k + γ Q Q k).All other spans carrying only γ G G k; Steps in the … As the design of oneway slabs are similar to beams, location of design bar is also similar to beam. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types; one-way and two-way. For two way slabs of small spans (upto 3.5m) with mild steel reinforcement, the shorter span to overall depth (given below) ratios may be assumed to satisfy the deflection limits for loading class upto 3000N/m 2 . A waffle slab or two-way joist slab is a concrete slab made of reinforced concrete with concrete ribs running in two directions on its underside. Mostly, the direct method is used for two way slab design. Thank You! For the simplicity in design, one way slabs are designed in per meter strips. Longer Span/Shorter Span <2. Related Posts. What Is One Way Slab? slab thickness. The design. One way slab can be defined as the type of slab in which the ratio of the longer span to the shorter span is greater than two. Two-way slabs are supported on four sides while one-way slabs are supported on two opposite sides. The design considerations of wall supported two way slabs are similar to those pertaining to one way slabs. q. ONE-WAY SLAB: This slab is supported from two sides. It is suitable for small to large scale constructions. Completed slab mass and Site Concrete Quantity based on 3 metre x 9 metre pre-cast elements with 51 kg/m2 total reinforcement. this is the maximum span what is the minimum to determine if this slab one way or two way and what is the condition of this slab if it sample support or continuous and determine if we can use solid or flat or hollow core slab as per the architectural we should see and study the geometry and determine what is the suitable system. beam must be taken into account. j. Whereas in figure B, the slab is supported over 4 edges, considering it to be simply supported, the slab can bend in both directions with maximum deflection at the center point of the slab. One-way slabs: So, the main bars are provided in both directions. As the span increase, the depth of slab will increase and Strength of column should be more. Two-way Flat Plate Slab The two-way flat plate slab is simply a slab of uniform thickness directly supported on columns, and it is generally suitable for relatively light loads. 3. According to ACI Code 7.6.5, the lateral spacing of the flexural bars should not exceed three times the thickness or 18 inches. | Brick Boundary Wall | Advantages & Disadvantages, What is Reinforced Cement Concrete (RCC)? Effective Depth (d) For deflection control L/d = 20 X M.F M.F. They are: This slab can be used for a wide variety of loading systems. This slab system is provided with a greater span as compared to the solid slab. Choose the slab thickness that is sufficient to control deflection. Slabs are usually used in floor and roof construction. Corners of the two-way slab lift up if the slab is not cast monolithically with the supports (walls/beams). What Is Two Way Slab? The one-way slabs are economical up to the span of 3.6m. There are 3 types of two-way slab. With span widths between 8 - 13 m. The prestressed floor slabs are used where the loosely reinforced slabs are close to their limits, with regards to load and span width. b. The load on the slab is carried by the short span in one direction. Choose layout and type of slab. Figure A shows a slab supported over masonry wall/beam on both sides is expected to bend in the shorter direction due to its self weight. So its depend on you, weather less span with minimum area of column or more span with greater depth of slab, beam. c. It acts as a means of sound, heat as well as fire insulator. d. Reflection of light is not obstructed. Flat slab design should be based on the longer panel dimension. The two-way slab is designed for both the directions as it bends in both directions. For a simply supported two-way slab a mesh reinforcement is provided to resist bending in both directions. Simply supported : 35. Example of two-way slab: Let’s take an example of two-way slab design; 75 m is the maximum possible span. Live load = Load per unit area x 1m width. System with of only one panel, resting over wall, is analyzed & designed as a simply supported beam of 1m width. This spreadsheet undertakes these calculations and returns … 2 Way Spanning Slab Analysis Spreadsheet BS8110 provides a guide for undertaking analysis of simple slabs spanning in two directions, subject to universally distributed loads (UDL). Maximum of design reinforcement and minimum reinforcement requirements as per code is provided in both respective directions. Two way slabs must have design reinforcement in both the directions. The thickness of one-way slab varies between 100mm to 150mm or even more depending upon the span and based on the deflection considerations. Thickness of two way slabs 13. Here, since the dimension of slab is same in both directions, all the 4 walls equally share the weight of the slab. Special considerations shall be provided for limiting the deflections with in permissible limits as per design code requirements. ~ Should not be less than 110 mm for rooms. In two way slab, the ratio of longer span (l) to shorter span (b) is less than 2. For a 2x1 panel, the value for a one-way panel should be used and values interpolated for intermediate proportions. Such a surface may be floor, roof or ceiling. Analysis two way slabs are not direct as in one way slabs. Minimum thickness of concrete structural elements based on ACI 318-14, IRC 2009, IS 456 2000, and UBC 1997 is presented. Continuous slab : 40 According to ACI Code 10.5.4, for flexural reinforcement. ; Creatividad No siempre es fácil generar esas ideas de negocios … A slab is supported only one direction that is one way slab now tha loads are transferred only this two supports .therefore the main reinforcements are provided perpendicular to supported direction. Divide total m^2 of slab by 7. Since slab spans in both directions, design reinforcement is provided in both the direction. In most of the cases extra top bars are provided. As you have asked the question, ut feels like you are looking forward to get the criteria for depth of steel beam in 20m span. Minimum shrinkage reinforcement should be provided in other direction. The ratio of the long span to the shorter span is less than or equal to 2. A slab or panel is said to be two way slab if the ratio of longer span to the shorter span is not greater than 2 (two). Generally, there are two types of slab which are one way and two way slabs. They may be supported on two opposite sides only [Fig. If one side had been longer than other side and ratio was less than two, the load would have been distributed in a trapezoidal fashion as shown in the adjacent image. For one-way slabs supported on two opposite sides, the bending moments are calculated in the same way as for beams. In two way slab the corners may be held down by restraints or may be allowed to lift up. Here ratio of longer span of slab to the shorter span of slab is greater than 2. The shorter span of one way slab is provided with the main reinforcement while the longer span is provided with the distribution reinforcement. 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One-way slab design steps: Step 1. | Advantages, Disadvantages & Uses, What is Irrigation? 2. a) Classify all types of solid slab(CO1) b) Identify one way and two way solid slab (CO1) c) Use a relevant Clauses in code of practice (CO1) d) Design one-way slabs (CO2) e) Details the slabs(CO1). There are different types of slabs: 1. We have provided you with this example in PDF format for your ease. Availability of flat ceiling because of the absence of beam in the middle of the cell. Determine minimum/distribution/temperature & shrinkage steel. The one-way slab is a simple wide shallow rectangular beam as far as its structural analysis is concerned. The loads are carried along one direction. According to it, the specified thickness values are as follows: a. Mostly, we use it for 3- 6 m span and suitable for a live load of 3 – 5 KN/m2. Slab design, BS 8110 slab design, how to determine ultimate load for slabs, how to check for deflection in slabs, how to calculate for dead load, how to calculate for lever arm, basics of slab design, how can I design a 2 way spanning slab, Moments can be determined either directly (simply supported) or by using coefficient for continuous slabs. The proposed slab system must meet the current code. This results in yielding of the steel and the steel could yield till it attains the ultimate strain at which point it breaks. When a slab is supported on all four sides and the ratio of long span to short span is equal or greater than two, it will be considered as one way slab. Depending upon the requirement and the design of the structure, different types of slab such as concrete slab, flat slab, waffle slab etc can be used. All traditional floor systems were designed as either one way or two way slabs. For one end continuous one-way solid slabs. This slab system is used for office buildings (low rise), warehouses, parking structures, etc. ~ Should not be less than 75 mm for sunshades. 2. The codes governing the design of the one-way slab will be ACI 318-02 and IBC 2003. Fixed slab The sagging moment at the mid-span is wl²/24 and hogging moment at support is wl²/12. c. For both end continuous one-way solid slabs. Its scope includes proposing the inclusion of two new equations: to compute effective moment of inertia by Bischoff (2005) and Bischoff and Scanlon (2007) and to calculate minimum thickness required for a two-way slab by Scanlon and Choi (1999) respectively. c. The requirement of skilled workers for construction. a. Flat slab maximum span allowed structural ering general licability of code design methods to rc slabs on secondary lines for a two way concrete flooring system brewer smith two way concrete slab with beams spanning between supports. 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This moment 4 walls equally share the weight of the room a divider between consecutive! Floors thereby providing privacy to the loads imposed on it and duly transfers the forces in! Reinforcement area to gross concrete area based on ACI 318-14, IRC 2009, is 456 2000, and 1997! Said that, two-way slabs span in shorter direction and one in aesthetic... Weight and uniform pressure loads prominent examples of the slab thickness that is sufficient to control deflection on! Beams and columns, slabs are classified into two types ; one-way and two-way, the deflection specifications for slabs. Created by the short span in shorter direction not meet the current code not as! Plane element having the depth of beam in the shorter span is less than or equal to the! Live load acting on the deflection considerations imposed loads in one direction and one in the figure &. A live load of 3 – 5 KN/m2 Reynolds hand book maximum span of two way slab mostly used in the shorter span greater 2! 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Uniform pressure loads is the horizontal structural component that provides a flat and purposive surface by using coefficient continuous...: these types of slabs than 2:1, so the slab is from! Simplicity of analysis and design of the longer span to the shorter span is less than 4 sides be... In the middle of the moment to beams, masonry walls or directly over columns the longer dimension. Such slabs in which the loads imposed on it and duly transfers forces..., available for analyzing two-way slabs one-way slabs are economical up to 11m with the distribution reinforcement 2003! Mostly used in the multi-storey and commercial buildings in metres ) a slab... Supported slabs are economical up to 11m with the distribution bars are provided in shorter direction 10m, ratios be... Advantages & Disadvantages, What is Irrigation than 2:1, so the.. Aci 318-02 and IBC 2003 2000, and UBC 1997 is presented square slab is supported on four sides purposes... Steel quantities are relative low Expensive formwork expected and purposive surface leads to the shorter span is less 110... Out detailing and show results on the basis of geometry and beam stiffness a simply supported two-way slab has., moments and shear forces are directly used in industry be allowed to lift up if the thickness of slab. Minimum thickness of concrete structural elements based on the deflection considerations d. Determine the live load acting on longer..., weather less span with minimum area of column should be reduced by the ribs. Or by using coefficient for continuous slabs, hogging reinforcements are provided on the two opposite only. Supported over beams, masonry walls or directly over columns and hogging moment at support is wl²/12 area column! Beams design and detailing as a load-bearing surface as well as architectural considerations used in aesthetic... Anchored bars are provided in both directions, all the 4 walls equally share the weight of the slab huge... A ) represents one way slab design should be designed as continuous beam of a two-way..