The oneway slab is a slab, which is supported by parallel walls or beams, and whose length to breadth ratio is equal to or greater than two and it bends in only one direction spanning direction while it is transferring the loads to the two supporting walls or beams, because of its geometry. Corners of the twoway slab lift up if the slab is not cast monolithically with the supports wallsbeams. Pdf analysis of two way ribbed and waffle slabs with hidden beams. A reinforced concrete slab is a broad, flat plate, usually horizontal, with top and bottom surfaces parallel or nearly so. The oneway slab is deflected in one way direction and primary reinforcement is placed in one direction whereas.
Design of reinforced concrete structures ii two way slabs 1 1. Aug 22, 2018 how to design two way slab simply supported corners free to lift limit state method is 4562000 duration. Pdf analysis of two way ribbed and waffle slabs with. The structural action of a oneway slab may be visualized in terms of the deformed shape of the loaded surface. Twoway slabs supported on beams the critical location is found at d distance from the column, where the supporting beams are stiff and are capable of transmitting floor loads to the columns. Aug 02, 2017 build house with concrete hollow blocks laying cement brick constriction engineer build house duration. Bending moment and shear force of twoway slab are depend on l y l x ratio and. In this example, the latter option will be used to achieve better understanding for the design of twoway joist slab often called twoway ribbed slab or waffle slab. Buildinghow products books volume b slabs twoway slabs. The name waffle comes from the grid pattern created by the reinforcing ribs. Load transfer in a one way slab, b two way slab nilson fig. Slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs, bridges, and other types of structures. Concrete slab types construction, cost, and applications.
Twoway concrete slab with beams spanning between supports. This work compares experimental results of six twoway reinforced concrete ribbed flat slabs with rectangular holes close to the column and. Analysis of two way ribbed and waffle slabs with hidden beams ibrahim mohammad arman international journal of civil and structural engineering volume 4 issue 3 2014 343 four slabs are taken in this study to show the moments distribution in two way ribbed slab. Two way slabs supported on beams the critical location is found at d distance from the column, where the supporting beams are stiff and are capable of transmitting floor loads to the columns.
How to design two way slab simply supported corners free to lift limit state method is 4562000 duration. In addition, the scope of this study is to design oneway ribbed slab and twoway. Corners of the two way slab lift up if the slab is not cast monolithically with the supports wallsbeams. This is a part of his project economic design of two way rcc slabs under prof s. Figure 1 shows a rectangular slab, simply supported along its two opposite long edges and free of any support along the two opposite short edges. Slabs are usually used in floor and roof construction. In sap program, the model has been divided to frame elements to represent ribs and beams and shell elements to represent the slab and solid part. Mpa f c 25 mpa f y 420 b a b a 3 evaluate load distribution in both directions. The structural action of a one way slab may be visualized in terms of the deformed shape of the loaded surface.
Determine moments at critical sections in each direction, normally the negative moments at supports and positive moment near midspan. Reference 5 focused on analysis of twoway ribbed slabs with. They are either oneway spanning systems known as ribbed slab or a twoway ribbed system known as a waffle slab. Pdf comparison between ribbed slab structure using. The slab may be supported by walls, by reinforced concrete beams usually cast monolithically with the slab, by s. Design of reinforced concrete structures ii twoway slabs 1 1.
Load transfer in a oneway slab, b twoway slab nilson fig. Shear reinforcement in two way slabs without beams. This form of construction is not very common because of the formwork costs and the low fire rating. Pdf ribbed slabs have been widely used in buildings due to their many advantages, especially the decrease of concrete below the neutral. One way slab design how to design one way slab daily civil. Jul 22, 2015 my graduation project with my mate ghassan faris, a two way ribbed slab of clear span of 18 x 25 m was designed by safe 2014, the building is 3storey concrete. In one way slab, the ratio of longer span l to shorter span b is equal or greater than 2, i.
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. 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. 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. Mathematical structural analysis of one way ribbed slabs was introduced in this paper. Skydome is a system of modular formwork in plastic used to build twoway ribbed slabs in residential and commercial buildings. The main reinforcement for two way slab are designed in two directions which are xdirection and ydirection. Oct 27, 2016 one way slab is a slab which is supported by beams on the two opposite sides to carry the load along one direction. In twoway slabs shorter direction strip carry greater %age of load. The results of the parametric analysis indicate that the deflection of posttensioned twoway slab is more affected by the span length than by the other variables. Interior left, exterior right deflection analysis the final consideration in the design of the twoway slabs is deflection. Ribbed slab design spreadsheet free download description. In two way slab, the ratio of longer span l to shorter span b is less than 2. According to adoss, the interior spans due not meet the code requirements to neglect deflection.
Twoway joist concrete slab floor waffle slab system. The covering materials weigh is 2knm 2, and the live load is 3knm 2. The basic design procedure of a two way slab system has five steps. The two way waffle slab is economical when it is used in the modular or prefabricated form. Twoway slab action is assumed in a ribbed floor made of the doubletee section precast, in the ribbed floor with integral beams. Slab resting on walls or sufficiently deep and rigid beams on all sides. The two way slab is designed for both the directions as it bends in both directions. The two way slab will deflect in a dish or saucerlike form under the action of loads. All about structural analysis and design 4,029 views 55. Twoway slab analysis and design using equivalent frame method efm aci 318 states that a slab system shall be designed by any procedure satisfying equilibrium and geometric compatibility, provided that strength and serviceability criteria are satisfied. Reinforced concrete, 2014, 9th edition, aci 31811 code edition, by jack c. Two way slab design by direct design method as per aci 31811. Teaching twoway ribbed slab analysis and design using the. Ca vent pipe between beams pilebeam foundation prepared subbase vent riser pipe to roof beton stop cupolex form pontex internal rib beam form cupolex concrete slab applications there may be many reasons for suspending a floor slab that may include.
Analysis of two way ribbed and waffle slabs with hidden beams ibrahim mohammad arman international journal of civil and structural engineering volume 4 issue 3 2014 343 four slabs are taken in this study to show the moments distribution in two way ribbed slab with hidden beams systems. Analysis and design of slabs two way civil engineers pk. Sandwich slabs may have the disadvantage of a larger weight compared to the ribbed ones but on the other hand, they have the advantage that their spans and supports behave in the same proper way. The load on the slab is carried by the short span in one direction. Oneway and twoway slabs oneway slabs transfer the imposed. Minimum free edge distance for punching shear 4 times slab thickness. Two way slabs have two way bending unlike one way slab. For uniformly distributed loads of w per square foot of the slab, each strip acts approximately like a simple beam uniformly loaded by its share of w. Twoway slab systems offer several possible arrangements for the tendon layout 10. Analysis of two way ribbed and waffle slabs with hidden beams. Comparison of one way and two way slab behavior economic choices flat plate suitable span 20 to 25 ft with ll 60 100 psf advantages low cost formwork exposed flat ceilings fast disadvantages low shear capacity low stiffness notable deflection.
The result of this study shows that one way ribbed slab with beam used in residential building is more preferable from the economical point of view since it is less expensive than the two way. Reference 5 focused on analysis of two way ribbed slabs with. Static analysis of twoway slabs, subjected to uniform load, is performed using tables, which give the fundamental support moments, span moments and shear forces. Twoway slab article about twoway slab by the free dictionary. In two way slabs shorter direction strip carry greater %age of load. The waffle slab is also sometimes termed as ribbed slab system but you would find it interesting to know that ribbed and waffle slab are somehow two different things. The general provisions for construction and design procedure are given in cop 20. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Brendon burley structural option posttensioned twoway slab figure 23 details of the twoway slab. Design of concrete structures 14th edition, 2009, by arthur h. 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. The ratio lb which is less than 2 is known as two way slab. The twoway waffle slab is provided with a bigger span as compared to the solid slab.
Two way slab action is assumed in a ribbed floor made of the doubletee section precast, in the ribbed floor with integral beams. Bb example 2 design the twoway ribbed slab the covering materials weigh 2. May 15, 2020 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. Accordingly, main reinforcement is required in the two directions. Generally, there are two types of slab which are one way and two way slabs. These conditions are set out in last section dealing with oneway ribbed slabs.
These conditions are set out in last section dealing with one way ribbed slabs. Verandah slab is a type of one way slab, where the slab is spanning in the shorter direction. Distribute moments transverse at critical sections to column and middlestrip and if. The one way slab is deflected in one way direction and primary reinforcement is placed in one direction whereas. The twoway waffle slab is economical when it is used in the modular or prefabricated form. The one way waffle slab system contains a hollow slab with a height more than. Two way joist concrete slab floor waffle slab system pdf. Oneway and twoway slabs university of asia pacific. When one says ribbed slab it is actually a one way spanning system with ribs where as in waffle slab the joists form a two way system. The results of this analysis are compared with the results of the finite element method by sap program. My graduation project with my mate ghassan faris, a two way ribbed slab of clear span of 18 x 25 m was designed by safe 2014, the building is 3storey concrete. Design of reinforced concrete structures ii twoway slabs. In reality, sandwich slabs are ribbed slabs with a slab placed both to their upper and lower surface. Introduction in reinforced concrete construction, slabs are used to provide flat, useful surfaces.
Lb2 is one way slab lb slab, 3 apply drop panels at columns, or 4 use two way joist slab system. Waffle slabs are preferred for spans greater than 40 feet 12 m, as they are much stronger than flat slabs, flat slabs. This is because its length to width ratio is longshort not big enough for loads to travel in the short direction onl. Ribbed floors consisting of equally spaced ribs are usually supported directly by columns. Comparison of oneway and two way slab behavior economic choices flat plate suitable span 20 to 25 ft with ll 60 100 psf advantages low cost formwork exposed flat ceilings fast disadvantages low shear capacity low stiffness notable deflection. They are either one way spanning systems known as a ribbed slab or a two way ribbed system known as a waffle slab.
One way slab is a slab which is supported by beams on the two opposite sides to carry the load along one direction. Minimum thickness of two way slab as per aci 31811 for deflection. Bending will take place in the two directions in a dishlike form. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types.
A slab supported on all four edges with an aspect ratio of longer to shorter theoretical span less than. In two way slabs, load will be carried in both the directions. Chapter 3 design of rectangular beams and oneway slabs. Two way rcc slab designing tool in microsoft excel developed by shankar tayal a 3rd year student of school of infrastructure, indian institute of technology, bhubaneswar.
The twoway slab is designed for both the directions as it bends in both directions. However main reinforcement bar and distribution bar in transverse direction. Rectangular beams and oneway slabs page 5 of 9 maximum permissible steel ratio, max an overreinforced beam will fail in a brittle manner while an underreinforced beam will. Bending moment and shear force of two way slab are depend on l y l x ratio and. Two way slabs are normally supported from four sides. The main reinforcement for twoway slab are designed in two directions which are xdirection and ydirection. A twoway slab tws is simply a slab carrying loads in both directions length and width to its supports beams or columns. Minimum thickness for two way slab construction designed as per methods provided by. They are either oneway spanning systems known as a ribbed slab or a twoway ribbed system known as a waffle slab. The two way waffle slab is provided with a bigger span as compared to the solid slab. In this case four options can be considered 1 increase the slab thickness further 2 use headed shear. The twoway slab will deflect in a dish or saucerlike form under the action of loads. Check the applicable joist dimensional limitations as follows. Difference between one way slab and two way slab daily civil.
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. Difference between one way slab and two way slab simple. One way shear in slab mrhershey structural 20 nov 17 15. The ratio of the total costs was found to be within the range 1. The result of this study shows that oneway ribbed slab with beam used in residential building is more preferable from the economical point of view since it is less expensive than the twoway. Cost optimization of a composite floor system, oneway waffle slab. Two way slab design bibloteka free online learning. The basic design procedure of a twoway slab system has five steps. 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. Twoway slabs have two way bending unlike oneway slab. Two way slabs beam structure column free 30day trial. A waffle slab or twoway joist slab is a concrete slab made of reinforced concrete with concrete ribs running in two directions on its underside. Analysis and design of twoway slabs page 1 chapter 3. Chapter 3 design of rectangular beams and oneway slabs 12.
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