Slab supported directly by columns are called flat slab. Pdf babadua reinforced concrete twoway slabs subjected to. In order to find out the bar bending schedule for slab or steel reinforcement in slab, i recommend you to learn basics of bar bending schedule and how to adopt concrete cover for different components of a building. Design of a two way slabs for punching shear resistance. Two way slab design excel sheet all about free books. 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. For reasons regarding behaviour, safety and economical design, the twoway slab is far more efficient than the equivalent oneway slab. Compute positive and negative moments in each direction. Slab design reading assignment chapter 9 of text and, chapter of aci31802. Fiberreinforced polymer strengthening of twoway slabs. These materials are originally located at different websites. Generally slab thickness varies between 4 to 20 inches where as its length and width varies between 10 to.
Slab may be supported on walls or beams or columns. Pdf this work investigated the flexural strength and deformation of 14. The rib reinforcement follows the same rules with the beam reinforcement. Fortunately this is a basic question and the answer is very simple. Why are we provide main reinforcement in bottoms in a one. Nonprestressed bonded reinforcement in posttensioned. The ratio lb which is less than 2 is known as two way slab. Oneway and twoway slabs oneway slabs transfer the imposed. Finally, calculate reinforcement area, then number of bars and their spacing. Design of reinforcement for one way slab and two way slab. In two way slabs, load will be carried in both the directions.
However main reinforcement bar and distribution bar. Oneway slabs transfer the imposed loads in one direction only. The twoway slab is designed for both the directions as it bends in both directions. The steel fixers formwork drawing of a twoway slab.
Bar bending schedule plays a vital role in finding the quantities of reinforcement in structure. Twoway joist concrete slab floor waffle slab system analysis and design. The basic design procedure of a twoway slab system has five steps. Comparison of oneway and twoway slab behavior economic choices oneway slab on beams suitable span 3 to 6m with ll 35knm2. Furthermore, in the corner of two simply supported edges, bottom reinforcement perpendicular to bisector is to be provided. These tendons run the full length of the slab between bands and are specified to be at the center of the slab with no vertical curved profile, as shown in fig. Due to this reinforcement is also provided in both directions. 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 slabs are normally supported from four sides. Flat plate concrete floor system does not use beams between columns or. In two way slab the corners may be held down by restraints or may be allowed to lift up. Between the ribs, the slab is usually reinforced with a common wire mesh. Chapter 3 design of rectangular beams and oneway slabs. Slab supported on two sides and bending takes place predominantly in one direction only is called one way slab.
However, mainly as far as the stirrups are concerned, the amount of placed rebars is not as large as it is in beams. Difference between one way slab and two way slab daily civil. Twoway joist concrete slab floor waffle slab system. In this article, i will discuss how to design one way slab with example. The other half span rebars are formed with a straight length. Flat slab system is an important division of concrete floor system. The following example illustrates the design methods presented in the pca book simplified design. A civil engineer must know all the aspects regarding the flat floor system. Further discussion of the differences between one and twoway systems is given in reference aalami, 1993b. Buildinghow team integrates all earthquake resistant building technologies.
Two manual approximate methods will be shown below. Twoway slab systems offer several possible arrangements for the tendon layout 10. In this video deisgn of two way slabs has been covered using is 456. Reinforcement detailing of a slab is done based on its support conditions.
The twisting moments discussed earlier are usually of consequences only at exterior corners of a twoway slab system, where they tend to crack the slab at the bottom along. Design of reinforced concrete structures ii twoway slabs 1 1. Determine the thickness of the slab, according to procedures provided here. Here, we have tried to gather various reading materials available in the web about flat slab floor system in one place. The length and width of slab is much higher than that of its thickness. Beamless slabs beamless slabs are supported only on columns and are applied mostly in large industrial and public. Usually, when a slab is supported by a beam the support is considered to be pinned. Design of reinforced concrete structures ii twoway slabs.
Twoway flat plate concrete floor system analysis and design. Concrete slabs are commonly divided into the following types. 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. Accordingly, main reinforcement is required in the two directions. Oneway and twoway slabs university of asia pacific.
This guide presents analysis methods, design procedures, slab reinforcement and detailing practices, and strength and serviceability considerations, as well as information for the resistance to lateral forces for slab. Designing of slabs depends upon whether it is a oneway or a two way slab, the end conditions and the loading. The maximum spacing of reinforcement at critical design sections for positive and negative moments in both the middle and column strips shall not. In two way slab main reinforcement is provided along both direction. Shrinkage and temperature reinforcement in twoway post. There are several methods by which twoway slabs can be designed. The twoway slab will deflect in a dish or saucerlike form under the action of loads. Verandah slab is a type of one way slab, where the slab is spanning in the shorter direction with main reinforcement and the distribution of reinforcement in the transverse direction what is two way slab. Corners of the twoway slab lift up if the slab is not cast monolithically with the supports wallsbeams. Two way slab design by direct design method as per.
Difference between one way slab and two way slab simple. Oneway and twoway slabs oneway slabs transfer the imposed loads in one direction only. The lateral loads are independently resisted by shear walls. Deep ribs, the concrete and steel quantities are relative low expensive formwork expected. The minimum required reinforcement in the support areas is provided in two alternative ways. 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. No beam, free layout and large windows create bright and open spaces in flat slab floors. The reinforcement rules are also similar in both directions. Draw the slab, and lebel all the reinforcement sizes and spacings. Check slab reinforcement at exterior column for moment transfer between slab and column. One way slab design procedure with example design of one. For slabs and beams, bending flexure is the criteria and there by t. How to detail reinforcements of twoway slabs quora.
Jul112018 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. It is possible that designers who specify these arrangements of reinforcement in twoway posttensioned. In a twoway system such as a columnsupported slab, the load is carried in both directions. A bentup bar called as crank bar is provided to make rcc slab safe from compressive stresses. On the other hand, when slab is supported on all four sides and bending take place in two directions are said to be two way slab.
The other ways of analysis of twoway slabs are the direct design method and the equivalent frame method. Behavior and reinforcement of oneway slab the structural frame consists of four columns, two beams and one slab. Products books volume a the reinforcement ii slabs ribbed slab. They may be supported on two opposite sides only fig. Slabs could be simply supported, continuous or cantilever. Design of twoway slab by coefficient method the constructor. The first reinforced concrete design manual formerly titled aci design handbook was developed in accordance with the design provisions of 1963 aci 318 building code by aci committee 340, design. Reinforcement detailing of reinforced concrete slabs.
A single slab with twoway reinforcement rebars will be analyzed with rcsolver. The load on the slab is carried by the short span in one direction. When a reinforced concrete slab is 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. Both ways you can see the one way slab and two way slab two way slab supported by four side beam and one way slab supported by two side beam 8 mm rods been used here. Pdf slabs are the flooring systems of most structures including office, commercial and residential. Manual for design and detailing of reinforced concrete to the code.
When a rectangular slab is supported on all the sides and the lengthtobreadth ratio is less than two, it is considered to be. Layout of posttensioning reinforcement in floor slabs by dr. Contains all design checks required by the american concrete institute code and all the conditions that must be met during the design process. Design of two way slabs is 456 limit state method youtube. Can be used for larger spans with relatively higher cost and higher deflections oneway joist system suitable span 6 to 9m with ll 46knm2. Twoway concrete slabs with openings the static system and the design of reinforcement. Bending will take place in the two directions in a dishlike form. Slab is one of the most famous part of a construction project. Slab is a broad and flat structural member mainly used on modern building.
The following example illustrates the example building. In this post, we are going to explain how to calculate steel quantity for the slab. In twoway square slab, the twoway action is equal in each direction. Loaddeflection response of babadua reinforced oneway slabs. Download two way slab design excel sheet template for free. Pdf fiberreinforced polymer strengthening of twoway slabs. The very purpose of reinforcement in rcc structures is to contain the tensile stresses induced in the system.
The value of 23 is appropriate for twoway spanning slab if it is continuous over one long. In two way slab, the ratio of longer span l to shorter span b is less than 2. Measurements of deflection at the beams free end and strain in. How to design two way slab simply supported corners free to. Determine moments at critical sections in each direction, normally the negative. Its area per 1 m of a section width should not be less than that designed in the middle. When bent up bars are provided, the strength and deformation. How to design a twoway slab free download as powerpoint presentation. Chapter 3 design of rectangular beams and oneway slabs 12 h. The program covers wide range of twoway slab systems and can be used for more complex slab layouts. Please read the lauses mentioned in the video while solving the problem. 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.
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