Design the slab, following the provisions of the ack code. The coefficient method is a method of designing twoway slabs that are supported by edge beams. Slabs are usually used in floor and roof construction. Twoway slab design using the coefficient method beam. Two way slab by coefficients beam structure bending. Mar 09, 2019 direct design method ddm is the preferable method for designing the conventional two way slab system and other floor system like flat slabs and flat plate slab system. Time saving design aids 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. Bending will take place in the two directions in a dishlike form. Reinforced concrete design reinforced concrete design twoway slabs design of twoway slab moment coefficient method load transfer from twoway slab bar. Design of a structural member is governed by what kind of forces it has to resist. Design of two way slab by coefficient design of two way. Design of two way slab by usd method and usd method slab case slab dimension short. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types.
There are several methods by which two way slabs can be designed. Analysis of twoway slabs by coefficient method the determination of exact moments in twoway slabs with various support conditions is mathematically formidable and not suited to design practice. Reinforced concrete design 1 design of slab examples and. In case of one ways slabs, the aci approximate analysis is applicable to one way slab system where a one way slab is continuous with a one way slab. Analysis of two way ribbed and waffle slabs with hidden beams. Slabs can be designed by direct design method known as ddm and another method for design is coefficient method which is the easier one.
Design of twoway slab by coefficient method behaviour of two way slabs one way slab deform under load into an approximately. In case of one ways slabs, the aci approximate analysis is applicable to one way slab system where a one way slab is. If the proportion of longer dimension of the slab panel to the shorter dimension is more than or equivalent to 2 then it is defined as one way slab. Ce 403, fall 20 oneway slab design 3 4 aci 31811 referenced pp 2 4 rating. Accordingly, main reinforcement is required in the two directions. There should be no reversal of moments at the critical design sections near. The design bending moment of twoway restrained slab can be calculated as follows.
The same is true for a two way slab or any other floor system where. In this article, it is assumed that slab thickness is determine but calculation of column and middle strips is explained in the following section. Analysis and design of slabs two way two way edge supported slabs twoway slabs. 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. I know there are new methods for designing two way slabs, direct design method or equivalent frame method.
These materials are originally located at different websites. Two way slab design static equilibrium of two way slabs total moment in both beams full load was transferred eastwest by the planks and then was transferred northsouth by the beams. Bss090119991 abstract this design example illustrates the empirical design method for composite concrete bridge decks specified in article 9. In this video deisgn of two way slabs has been covered using is 456. Slab resting on walls or sufficiently deep and rigid beams on all sides. This condition occur when the slabs are connected monolithically with support. Jul 02, 2010 lecture series on design of reinforced concrete structures by prof. Download our free two way slab design spreadsheet only from samotech. Flat slab analysis, design and detailing pdf civil engineering. Method 2 yieldlines may be successfully used for uniformly loaded slab panels with different boundary conditions. Two way slab design coefficient method tables free download as pdf file. Here, we have tried to gather various reading materials available in the web about flat slab floor system in one place. The aci coefficient method is declared obsolete because the end results are more conservation more factor of safety. No certain method can be found in the design codes or references for designing two way slabs subjected to concentrated loads.
Reinforced concrete, 2014, 9th edition, aci 31811 code edition, by jack c. Analysis and design of slabs two way civil engineers pk. It is designing for moments in a two way slab by using coefficients listed for column strips and mid strips for each direction with different edge conditions. Slab design example 02 design of simply supported slab two way spanning span of slab 4. Two way concrete floor slab with beams design and detailing design the slab system shown in figure 1 for an intermediate floor where the story height 12 ft, column cross sectional dimensions 18 in. Rectangular beams and oneway slabs page 2 of 9 two methods. Slab design the slabs are designed according to bending moment, shear and torsion.
But i think, many structural designers are still using the old method which is coefficient method or method 3 of the aci 1963 building code and which for me i think is still preferable. Chapter 3 design of rectangular beams and oneway slabs 12. There are many methods that are used to analyze two way slabs and the precision of these methods vary depending. Finally, since shear reinforcement is not used in oneway slabs, the concrete must be able to resist the maximum shear force. Twoway concrete floor slab with beams design and detailing design the slab system shown in figure 1 for an intermediate floor where the story height 12 ft, column cross sectional dimensions 18 in. Dhang, department of civil engineering, iit kharagpur. Design of slab examples and tutorials by sharifah maszura syed mohsin example 1. A reinforced concrete slab is built integrally with its supports and consists of two equal spans, each with a clear span of 15 ft. From the study it is considered that post tension slab is more economical than twoway slab. This paper focuses on analysis of twoway ribbed and waffle slabs with hidden beams.
Direct design method ddm is the preferable method for designing the conventional two way slab system and other floor system like flat slabs and flat plate slab system. Slab design reading assignment chapter 9 of text and, chapter of aci31802 introduction aci318 code provides two design procedures for slab systems. Twoway slab design using the coefficient method free download as pdf file. Alternate design method design procedure of twoway slabs using aci. Design of reinforced concrete structures ii twoway slabs 1 1. Title reinforced concrete slab design using the empirical method publication no. There are many methods that are used to analyze twoway slabs and the precision of these methods vary depending. Design procedure of twoway slabs using aci moment coefficients.
Twoway concrete slab with beams spanning between supports. The following example illustrates the example building. Twoway slab design coefficient method tables qn85e8pkopn1. Before the start of two way slab design, slab depth should be determined in addition to specify column strips and middle strips. Each single slabs are referred to as panels, if the slab is continuous over supports. Design of concrete structures 14th edition, 2009, by arthur h.
Chapter 3 design of rectangular beams and oneway slabs. The service live load is 100 psf, and 4000 psi concrete is specified for use with steel with a yield stress equal to 60,000 psi. Yield line pattern for the general case of twoway slab bending moment. Dec 20, 2017 in this video deisgn of two way slabs has been covered using is 456. The slab has to carry a distributed permanent action of 1. Direct design method ddm for slab systems with or without beams loaded only. Oneway and twoway slabs oneway slabs transfer the imposed. There are several methods by which twoway slabs can be designed.
Slabs are primarily categorized as either one way or two ways. The main structural action is one way in such cases, in the direction normal to supports on two opposite edges of a rectangular panel. General steps for the design of two way slab system by efm. Design of two way slab moment coefficient method bnbc 1993. Introduction analysis of plates and shells to attain internal actions for designing structural elements is one of the fields that scientists and engineers have been working on for years. Lecture series on design of reinforced concrete structures by prof. Dec, 2017 beam and slab arrangement can be the best example for one way and two way slabs. This method requires various formulas for different conditions of rc slab. However, plastic method can be the best method for designing such cases of twoway slabs. Dec 01, 20 9 aci moment coefficient for two way slab 12120 10. For example, the minimum slab thickness for a twohour fire rating is 4.
Two way slabs have two way bending unlike one way slab. Reinforced concrete design reinforced concrete design two. Two way slab design as per method 3 aci concrete code. Oneway and twoway slabs university of asia pacific. Rectangular beams and one way slabs page 2 of 9 two methods. Recommendations use method 2 or method 3 generally. Mention the parameters governing slab moment coefficients and explain their effects on moment. Design of two way slab by coefficient method behaviour of two way slabs one way slab deform under load into an approximately. 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.
The coefficient method may be the simplest, easiest and the quickest approach for the design of twoway slab supported by edge beam on all slab sides. Twoway concrete slabs with openings these problems cannot be solved by analytical methods since such structures like concrete slabs with openings, especially strengthened with carbon fibres, are too complicated. Strength design or ultimatestrength design usd strength design or ultimatestrength design usd with strength design method, the working dead load dl and live load ll are. Design of twoway slab by coefficient method the constructor. Please read the lauses mentioned in the video while solving the problem. Flat plate concrete floor system does not use beams between columns or. Design of reinforced concrete structures ii two way slabs 1 1. For the method of design coefficients use is made of the moment and shear coefficients given in the code, which have been obtained from yield line analysis.
A civil engineer should study these lectures and materials for structural engineering acumen. Alternate design method design procedure of twoway slabs using aci moment coefficients and approved by bnbc 20 scope and limitations bnbc 6. Design of reinforced concrete structures ii twoway slabs. Fanella, which appeared in the october 2001 edition of structural engineer magazine.
All methods are viable provided that the safety and serviceability of the elements are within the acceptable limits. This method was provided in the american concrete institute aci in 1963 to design two way slabs carried by steel beams, deep beam, or walls. If the ratio of longer dimension of the slab panel to the shorter dimension is greater than or equal to 2 then it is designed as one way slab. One way slab and twofigure 1 way slab in figure 2a slab is supported on two opposite sides only. Twoway slabs have two way bending unlike oneway slab. Beam and slab arrangement can be the best example for one way and two way slabs. Alternate design method design procedure of twoway slabs. Pdf design comparison of slab system by direct design method. Allowable stress design or working stress design wsd 2. The basic design procedure of a twoway slab system has five steps. Analysis and design of slabs two way two way edge supported slabs two way slabs. Application of limit state method to rectangular beams for flexure, shear, bond and torsion. The coefficient method may be the simplest, easiest and the quickest approach for the design of two way slab supported by edge beam on all slab sides. Method 2 gives a better rep resentation of internal forces in a slab panel than method i.
Reinforced concrete design 1 design of slab examples. Sep 03, 2011 design moments for top and bottom reinforcement in a panel of slab. In a two way slab the slab has to resist the following forces. Two way slab design by direct design method as per aci 31811. Various simplified methods are therefore adopted for determining moments, shears and reactions in such slabs. Twoway restrained slab if the slabs consist more than one panel or corner of the slab are prevent against lifting it is define as twoway restrained slab. Two way reinforced concrete slab design spreadsheet working stress design coefficient method. Multi storey, post tension, two way, design, comparison. Aci coefficient method for analysis of twoway slabs. Reinforced concrete design reinforced concrete design two way slabs design of two way slab moment coefficient method load transfer from two way slab bar detailing design example slab on ground.
However, it should be known that the coefficient method is still applied for twoway slabs. Simply supported one way slab a rectangular reinforced concrete slab is simplysupported on two masonry walls 250 mm thick and 3. In case of two way slabs, the moment coefficient tables are applicable to two way slab system where a two way slab is continuous with a two way slab. 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. The same is true for a twoway slab or any other floor system where. Reinforced concrete slab design using the empirical method. Two way reinforced concrete slab design spreadsheet working. In case of twoway slabs, the reinforcement against bending is estimated for. I would guess that you are referring to method 2 and method 3 in the 63 code my personal favorite.
Analysis of two way slabs by coefficient method the determination of exact moments in two way slabs with various support conditions is mathematically formidable and not suited to design practice. A simplified method for designing rc slabs under concentrated. Notes author staff bridgesight software sponsor bridgesight software. Direct design method alias ddm as well as coefficient method are used to design the slabs.
Keywords yield line method, twoway slab, analysis of slab, slab moments coefficients. However, plastic method can be the best method for designing such cases of two way slabs. Limit state of collapse and limit state of serviceability. Reinforced concrete design reinforced concrete design twoway. Bending will take place in the two directions in a dishlike fo. The slab was divided into strips middle and column or edge strip with the diemension as shown in figure below. This paper focuses on analysis of two way ribbed and waffle slabs with hidden beams. No certain method can be found in the design codes or references for designing twoway slabs subjected to concentrated loads. Nowadays, access to powerful computers and advanced software gives possibility to create accurate models by means of the finite. Twoway slab design static equilibrium of twoway slabs total moment in both beams full load was transferred eastwest by the planks and then was transferred northsouth by the beams. Tables for use with coefficient method for two way slab design. In this case the structural action of the slab is essentially one way. A slab is a concrete structure constructed to provide a flat surface.
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