The lateral loads are independently resisted by shear walls. Analysis and design of slabs two way civil engineers pk. A widely spread type of the twoway slabs used is the twoway ribbed slab or waffle slab composed of closely spaced parallel tsection small beams in each of the. Twoway joist concrete slab floor waffle slab system. Flat slab for heavy industrial loads suitable span 6 to 9m with ll 57. Figure 1 twoway flat concrete floor system version. Twoway slabs have two way bending unlike oneway slab.
I like to debate structural engineering theory a lot. They are either oneway spanning systems known as ribbed slab or a twoway ribbed system known as a waffle slab. It is common to have twoway ribbed slabs with spans from six to nine meters. Analysis and design of twoway slabs page 1 chapter 3. A widely spread type of the two way slabs used is the two way ribbed slab or waffle slab composed of closely spaced parallel tsection small beams in each of the two directions of the slab. Bending moment and shear force of twoway slab are depend on l y l x ratio and. The general provisions for construction and design procedure are given in cop 20. Difference between one way slab and two way slab simple. Reinforced concrete ribbed slabs with widebeam scielo.
Unless otherwise noted, all referenced table, figure, and. The following example illustrates the example building. Chapter 3 design of rectangular beams and oneway slabs 12. Twoway flat plate concrete floor system analysis and design. It will not be necessary to carry out deflection computation if these limitations are met. Waffle slabs can be used for spans that may reach up to twelve meters. There are many methods that are used to analyze twoway slabs and the precision of these methods vary depending on method assumptions. Pdf comparison between ribbed slab structure using. They are either one way spanning systems known as ribbed slab or a two way ribbed system known as a waffle slab. The slab is two way ribbed slab of 450mm thickness. In terms of economy of material, especially of steel, the twoway slab is often best because of the large effective depths of the beams. Aci documents are requested to contact aci via the errata website at.
The twoway slab shown in figure below has been assumed to have a thickness of 7 in. To see their result for this slab we will find the load factor. Waffle slabs can be used in halls, industrial buildings and parking floors. Twoway ribbed slabs are commonly used in residential and office buildings. A slightly deeper section is required but these stiffer floors facilitate longer spans and provision of holes.
Thermal simulation for a room with solid and oneway ribbed. Twoway flat plate concrete floor system analysis and design the concrete floor slab system shown below is for an intermediate floor to be designed considering partition weight 20 psf, and unfactored live load 40 psf. This condition occur when the slab are supported at four side of the beams or walls and the ratio of long span to short span is equal or less than 2. In two way slabs, load will be carried in both the directions. Design of reinforced concrete structures ii twoway slabs. Analysis and design of one way ribbed slab systems addis ababa institute of technology april 21, 2016 10.
Design of concrete structures 14th edition, 2009, by arthur h. A waffle slab or twoway joist slab is a concrete slab made of reinforced concrete with concrete. As they are one way slabs i treat them as wide beams. Mathcad program and show its impact on teaching the analysis and design of twoway ribbed slabs. Load paths, one and two way slabs structural concepts and design duration. Four slabs are taken in this study to show the moments distribution in two way ribbed slab with hidden beams systems. This is attributed to the considerable reduction in dead load as compared to other floor systems. Ribbed slabs oneway joists introducing voids to the soffit of a slab reduces dead weight and increases the efficiency of the concrete section. Guide to design of reinforced twoway slab systems american.
Additional reinforced internal ribs are then used in the slab by introducing pontex, the structural cupolex accessory to provide a structure capable of spanning between foundations or piles. Cost comparison between frames with solid slab and ribbed. Oneway and twoway slabs oneway slabs transfer the imposed loads in one direction only. One way spanning system is called ribbed slab while two way ribbed system is known as waffle slab. This work compares experimental results of six twoway reinforced concrete ribbed flat slabs with rectangular holes close to the column and. I am doing one way slabs and hope you can clean up my doubts about the one way shear in slab.
Generally, there are two types of slab which are one way and two way slabs. Jul 08, 2015 slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs, bridges, and other types of structures. This paper focuses on analysis of two way ribbed and waffle slabs with hidden beams. Flat plate for relatively light loads as in apartments or offices suitable span 4. There are many methods that are used to analyze two way slabs and the precision of these methods vary depending. Twoway slabs page 1 of 14 the following example illustrates the design methods presented in the article timesaving design aids for reinforced concrete, part 2. Two way flat plate concrete floor system analysis and design the concrete floor slab system shown below is for an intermediate floor to be designed considering partition weight 20 psf, and unfactored live load 40 psf. Two way slab design by direct design method as per aci 31811, step by step procedure and limitations of direct design method for two way slab is presented. A reinforced concrete slab is one of the most important structural elements of modern buildings.
In this article, the author presents a parallel approach to the traditional teaching method of twoway ribbed slabs. Chapter 3 design of rectangular beams and oneway slabs 12 h a 12 strip in a simply supported one way sl ab. Introduction in reinforced concrete construction, slabs are used to provide flat, useful surfaces. Accordingly, main reinforcement is required in the two directions.
Flat plate concrete floor system does not use beams between columns or. Teaching twoway ribbed slab analysis and design using. In order to prevent excessive deflections and avoid calculation of two way slab deflection which is a complicated procedure, aci 31811 restricts the minimum thickness of two way slab by applying three empirical limitations. The main reinforcement for twoway slab are designed in two directions which are xdirection and ydirection. Teaching two way ribbed slab analysis and design using the mathcad program mohammed s. That is, the load factor at which the uls moment equals the moment capacity. Teaching twoway ribbed slab analysis and design using the. However, in terms of labor in building the floor, the flat plate is.
The choice between two way and beamless slabs for more normal situations is complex. Mathematical structural analysis of one way 763 3 comparison between the results of finite element method and traditional method two bays one way ribbed slab is analyzed by both traditional and finite element methods to determine the induced moments of the rib. The used concrete block has a width of 500mm and a height of 380mm forming a rib of t section of flange width of 650mm. One way shear in slab structural engineering general. A reinforced concrete slab is a broad, flat plate, usually horizontal, with top and bottom surfaces parallel or nearly so. Twoway edge supported solid slab d twoway ribbed slabs. Determine moments at critical sections in each direction, normally the negative moments at supports and positive moment near midspan. Thermal simulation for a room with solid and oneway. Ribbed floors consisting of equally spaced ribs are usually supported directly by columns. Rectangular beams and oneway slabs page 2 of 9 two methods. Most often, these concrete slabs are used to construct floors and ceilings in high rise buildings and skyscrapers. The basic design procedure of a two way slab system has five steps.
Ribbed slab grid slab, solid slab, filler slab, folded plate 6 basis of spanning directions. Design of reinforced concrete structures ii twoway slabs 1 1. Normally it works fine but this time after carrying out the calculations the slabs fail in shear because of there are some huge point loads near the support. The saving of materials tends to be offset by some. I am doing oneway slabs and hope you can clean up my doubts about the one way shear in slab. Two way slabs are those slabs supported by columns arranged generally in rows so that they can deflect in two directions. Fanella, which appeared in the october 2001 edition of structural engineer magazine. The choice between twoway and beamless slabs for more normal situations is complex. Cant get the attachment to take on the slide show pdf.
Oneway and twoway slabs oneway slabs transfer the imposed. Analysis of an ultrahigh performance concrete twoway ribbed bridge deck slab. In this section, two types will be discussed, oneway solid slabs and oneway ribbed slabs. There are many methods that are used to analyze twoway slabs and the.
Formwork for ribbed concrete floors waffle moulds two way. As they are oneway slabs i treat them as wide beams. Sap2000, slab, twoway, ribbed, waffle, direct design method, beams. Teaching twoway ribbed slab analysis and design using the mathcad program mohammed s.
The following example illustrates the design methods presented in the pca book simplified design reinforced concrete buildings of moderate size and height third edition. Moments for design may be taken from table 3 for slabs simply supported on four sides. The slab was 610m simply supported on four sides and subjected to uniform load 1tm 2 and as shown in. The domeshaped forms create a matrix of voids surrounded by orthogonal ribbing, producing a two way configuration very suitable for largespanning slabs. This document is a technical summary of the unpublished federal highway administration report, analysis of an ultrahigh performance concrete twoway ribbed bridge deck slab, available only through the national technical information service. Design of two way ribbed slab 18 x 25 m clear span 1. What links here related changes upload file special pages permanent link page. Structural ribbed concrete slabs the cupolex floor slab can be fully or partially suspended on piles, stem walls or gradeedge beams. Pdf analysis of two way ribbed and waffle slabs with.
The main reinforcement for two way slab are designed in two directions which are xdirection and ydirection. This form of construction is not very common because of the formwork costs and the low fire rating. Two way slab design by direct design method as per aci 31811. Bending will take place in the two directions in a dishlike fo. Analysis and design of slabs two way two way edge supported slabs two way slabs. Oneway and twoway slabs university of asia pacific. The program covers wide range of twoway slab systems and can be used for more complex slab layouts. Slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs, bridges, and other types of structures. And this is possible only in monolithically cast concrete which is the twoway grid of beams. Chapter 3 design of rectangular beams and oneway slabs. In comparison with the normal reinforced solid flat plate, the reinforced waffle slab system proves to be much more efficient with carrying design loads, hence the various applications on office buildings, auditoriums, hotels, theater halls.
In this article, the author presents a parallel approach to the traditional teaching method of two way ribbed slabs. Application of lb ratio in first figure slab is supported on two opposite sides only. Two way ribbed slabs are slabs with concrete blocks while waffle slabs are slabs with removable forms. Ultimate behavior of oneway spanning slab linear elastic analysis methods such as moment distribution are linear elastic methods. The basic design procedure of a twoway slab system has five steps.
Two way slabs have two way bending unlike one way slab. Home market sectors formwork for ribbed concrete floors waffle moulds two way span previous next waffle moulds are a reusable formwork system for constructing twoway spanning ribbed concrete floors, which can achieve greater spans and use less concrete when compared to traditional flat slabs. The system was designed to decrease the weight of traditional fullconcrete slabs. Such as ribbed slab, flat slab, solid slab, continuous slab. Types of one way slab one way slab may be solid hollow ribbed 6. Two way slab is a slab supported by beams on all the four sides and the loads are carried by the supports along both directions, it is known as two way slab. Momentcoefficient method introduction the moment coefficient method included for the first time in 1963 aci code is applicable to twoway slabs supported on four sides of each slab panel by walls, steel beams relatively deep, stiff, edge beams h 3hf. One way and two way slabs one way slabs transfer the imposed loads in one direction only. Reinforced concrete, 2014, 9th edition, aci 31811 code edition, by jack c. One way slab oneway slabs are those slabs with an aspect ratio in plan of 2. The waffle slab is capable of providing the largest spans of the conventional concrete floor systems and can be economically used for spans up to 12.
Bending moment and shear force of two way slab are depend on l y l x ratio and. They may be supported on two opposite sides only fig. In comparison with the normal reinforced solid flat plate, the reinforced waffle slab system proves to be much more efficient with carrying design loads, hence the various applications on office. Pdf twoway joist concrete slab floor waffle slab system. Two slabs were supported on both edges of the x direction only. Section aa in the figure shows the beam cross section.
Analysis of two way ribbed and waffle slabs with hidden beams. Ribbed slabs one way joists introducing voids to the soffit of a slab reduces dead weight and increases the efficiency of the concrete section. In two way slab, the ratio of longer span l to shorter span b is less than 2. The slab may be supported by walls, by reinforced concrete beams usually cast monolithically with the slab, by s. Introduction addis ababa institute of technology april 21, 2016 3. In terms of economy of material, especially of steel, the two way slab is often best because of the large effective depths of the beams. Under the general provisions of the 1995 code, chapter, the twoway joist portion may be combined with a solid.
Under the general provisions of the 1995 code, chapter, the twoway joist portion may be combined with a solid column head or with solid wide beam sections on the column centerlines for uniform depth construction. These conditions are set out in last section dealing with oneway ribbed slabs. Analysis and design of slabs two way two way edge supported slabs twoway slabs. Analysis of two way ribbed and waffle slabs with hidden.
The effect of beams stiffnesses 196 methodology sap2000 program is used to analyze twoway ribbed simply supported rectangular slab models ranging from 5 x 5m to 5 x 25m. Minimum thickness of two way slab as per aci 31811 for. These are the direct design method presented in chap. A ribbed slab gives considerable extra strength in one direction while a waffle slab gives added strength in both directions. The design process described in analysis of an ultrahigh performance concrete twoway ribbed bridge deck slab is a step toward the development of design specifications for uhpc.
Slab resting on walls or sufficiently deep and rigid beams on all sides. Reduced slab soil contact area itional ribbed slab. This paper focuses on analysis of twoway ribbed and waffle slabs with hidden beams. Both are devices to reduce stresses due to shear and negative bending around the columns. One way and two way slab reinforcement in detail at sit duration.
Twoway joist concrete slab floor waffle slab system analysis and design design the concrete floor slab system shown below for an intermediate floor with partition weight of 50 psf, and unfactored live load of 100 psf. Analysis of an ultrahigh performance concrete twoway ribbed. Analysis of an ultrahigh performance concrete twoway. Current study, such as lau and clark, assesses the performance of one and twoway ribbed slabs with widebeams by analyzing the structural behavior of the. Twoway joist concrete slab floor waffle slab system analysis and design. Jul 22, 2015 design of two way ribbed slab 18 x 25 m clear span 1.
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