Allowable stress design or working stress design wsd 2. Design of one way and two way slabs, design of staircases. This method was provided in the american concrete institute aci in 1963 to design twoway slabs carried by steel beams, deep beam, or walls. Simply supported one way slab a rectangular reinforced concrete slab is simplysupported on two masonry walls 250 mm thick and 3. Method 2 yieldlines may be successfully used for uniformly loaded slab panels with different boundary conditions. The program covers wide range of two way slab systems and can be used for more complex slab layouts. Two way reinforced concrete slab design spreadsheet working. Static analysis of twoway slabs, subjected to uniform load, is performed using tables, which give the fundamental support moments, span moments and shear forces.
Two way slab by coefficients beam structure bending. Design of two way slab moment coefficient method bnbc 1993. 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. Foreword the reinforced concrete design manual sp1711 is intended to provide guidance and assistance to professionals engaged in the design of castinplace reinforced concrete structures. No certain method can be found in the design codes or references for designing twoway slabs subjected to concentrated loads. Determine moments at critical sections in each direction, normally the negative moments at supports and positive moment near midspan. Slab being the first element to be designed has pretty much importance as the whole structural design is based on the design of slab. The second appendix explains the basic mathematical considerations and develops the application of the finite difference method to the solution of plate problems. Asce, secb course content slab on grades construction. Introduction concrete slabs on grade are a very common type of concrete construction. Floor slabs can range from a simple residential basement slab to a heavyduty industrial floor. The second appendix explains the basic mathematical considerations and develops the application of the finite difference method to. This spreadsheet performs an analysis and design of twoway spanning reinforced concrete slab.
Design of twoway edge supported slab by using moment coefficients. Autoplay when autoplay is enabled, a suggested video will. Figure a shows a slab supported over masonry wallbeam on both sides is expected to bend in the shorter direction due to its self weight. Oneway and twoway slabs oneway slabs transfer the imposed. 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. Slab shear strength twoway shear check the adequacy of slab thickness for punching shear twoway shear at an interior column figure 4. Slabs are primarily categorized as either one way or two ways. The program covers wide range of twoway slab systems and can be used for more complex slab layouts. The basic design procedure of a two way slab system has five steps. The construction and design of concrete slabs on grade.
The method of substitutive beams principal steps of the analysis. 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. Design the slab, following the provisions of the ack code. When the ratio of long span to short span is less than 2, then the slab is known as a slab spanning in two directions or two way slab. Dissatisfaction with results of previously required procedures of analysis and design for two way slab beam systems was the original reason for the massive research upon two way slab systems begun about 1955. Buildinghow team integrates all earthquake resistant building technologies. Twoway simply supported slab a slab simply supported on its four sides with no provision has been made to prevent lifting or to resist the torsion then the moment coefficient of table 3. In two way slabs, load will be carried in both the directions. The first appendix presents an example of application of the data to a typical structure. Accurately determining the moments on a two way slab is typically accomplished by finite element computer analysis. Twoway concrete slab with beams spanning between supports.
Dhang, department of civil engineering, iit kharagpur. Interior bay dimensions 20 24 this example is to be used for educational purposes only. The basic design procedure of a twoway slab system has five steps. However, plastic method can be the best method for designing such cases of twoway slabs. The slab was divided into strips middle and column or edge strip with the diemension as shown in figure below. Can be used for larger spans with relatively higher cost and higher deflections oneway joist system suitable span 6 to 9m with ll 46knm2. The output of the program for the slab in the example is shown in the following pages. Recommendations use method 2 or method 3 generally. The slab has to carry a distributed permanent action of 1. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types.
Moduleiii design of short and long columns with axial and eccentric loading, design of isolated column footing. There are several methods by which twoway slabs can be designed. Chapter 3 design of rectangular beams and oneway slabs 12. Slabs are usually used in floor and roof construction. Two way slab design coefficient method method 3 of aci. A simplified method for designing rc slabs under concentrated. Minimum thickness for two way slab construction designed as per methods provided by aci 31811 code namely, direct design method and equivalent frame method. Slabs may be simply supported or continuous over one or more supports and are classified according to the method of support. A slab supported on all four edges with an aspect ratio of longer to shorter theoretical span less than. This method has been used extensively since 1963 for slabs supported at the. The most efficient design would be a square with equal lengths. Abstractdesigning twoway slabs under transverse concentrated loads is one of the challenges in designing such structures.
The construction and design of concrete slabs on grade d. I know there are new methods for designing two way slabs, direct design method or equivalent frame method. Two way slab design spreadsheet the engineering community. In two way slabs shorter direction strip carry greater %age of load. The steel fixers formwork drawing of a twoway slab for reasons regarding behaviour, safety and economical design, the twoway slab is far more efficient than the equivalent oneway slab. Minimum thickness of two way slab as per aci 31811 for. The two way slabs are modelled and analyzed using direct design method. Method 2 gives a better rep resentation of internal forces in a slab panel than method i. Design of reinforced concrete structures ii twoway slabs 1 1. Design of reinforced concrete structures ii twoway slabs.
Direct design method of flat plates per aci 31802 two way slabs are inherently difficult to analyze by conventional methods of statics because of the two way bending occurring. Two way slab design as per method 3 aci concrete code. If the proportion of longer dimension of the slab panel to the shorter dimension is more than or equivalent to. The following example illustrates the example building. The intended audiences for the use of this document are members of ptis slab onground committee as well as engineers and others involved in the design of foundations for residential and other lowrise structures. 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. The coefficient method is a quick handmethod of calculating the moments in twoway slabs. Design of reinforced concrete structures ii two way slabs 1 1. Pdf a modified equivalent frame method for lateral load. Twoway concrete slab on beams floor analysis and design. Design of two way slab by coefficient design of two way. Deflection of two way slab could be calculated by using available methods to make sure that the deflection will not.
Various simplified methods are therefore adopted for determining moments, shears and reactions in such slabs. 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 as per method 3 minorchord2000 structural 24 oct 07 18. The same behavior is expected when it is subjected to floor loads. Figure 3 coefficient ct for gross moment of inertia of flanged sections. Nilsons concrete textbook, design of concrete structures, has some nice charts for two way slabs, using the ratio of the sides and the. Direct design method of flat plates per aci 31802 twoway slabs are inherently difficult to analyze by conventional methods of statics because of the twoway bending occurring.
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. This method was provided in the american concrete institute aci in 1963 to design two. The coefficient method is a method of designing twoway slabs that are supported by edge beams. Depending on the geometry you will apply a different value to that span length. Two way slabs have two way bending unlike one way slab. 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. Current design codes aci 31805, eurocode 2 and bs 8110 permit the efm for the analysis of two. Rectangular beams and one way slabs page 2 of 9 two methods. Aci 31811 code provides two methods for two way slab design one of which is direct design method. The first reinforced concrete design manual formerly titled aci design handbook was developed in. Design of slab examples and tutorials by sharifah maszura syed mohsin example 1. Distribute moments transverse at critical sections to column and middlestrip and if. Manual for highways and railways issued by the highways. Alternate design method design procedure of twoway slabs.
The design method outlined in this code of practice is the limit state. 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. Next, the video briefly shows how to assess the required values for the gotten formula e. Alternate design method design procedure of twoway slabs using aci moment coefficients and approved by bnbc 20 scope and limitations bnbc 6. In twoway slabs shorter direction strip carry greater %age of load. Pdf design comparison of slab system by direct design. Jun 23, 2015 two way slab design spreadsheet working stress design coefficient method. Reinforced concrete design 1 design of slab examples. All available load test results indicated that the flat plate or flat slab was a most efficient design with an adequate safety factor.
Accordingly, main reinforcement is required in the two directions. A reinforced concrete slab is built integrally with its supports and consists of two equal spans, each with a clear span of 15 ft. Code as a method to design twoway slabs supported on all four sides by walls, steel beams, or. The pca computer program pcaslab can be used to expedite the design of different slab systems. So, main reinforcement is provided in both direction for two way slabs. It can be used by both practicing engineers and students. Twoway concrete floor slab with beams design and detailing csa a23. Design of twoway slab by coefficient method the constructor. Twoway slab design using the coefficient method beam. Two way slab design spreadsheet working stress design. Apr 18, 2019 this spreadsheet performs an analysis and design of two way spanning reinforced concrete slab.
Two way reinforced concrete slab design spreadsheet working stress design coefficient method download spreadsheet. The equivalent frame method efm was developed for two way slabs as a simple approximate method. Oneway and twoway slabs oneway slabs transfer the imposed loads in one direction only. Direct design method alias ddm as well as coefficient method are used to design the slabs. Bending will take place in the two directions in a dishlike form. In many cases, however, rectangular slabs are of such proportions and are supported in such a way that. The dimensions of an interior bay are shown in figure 1. The minimum thickness of slab is specified by aci 31811, section 9. Oneway and twoway slabs university of asia pacific. Sep 03, 2011 design moments for top and bottom reinforcement in a panel of slab. In control theory, the coefficient diagram method cdm is an algebraic approach applied to a polynomial loop in the parameter space, where a special diagram called a coefficient diagram is used as the vehicle to carry the necessary information, and as the criterion of good design. The method is to apply a coefficient to each direction of the span, lets call them msx and msy.
Comparison of oneway and twoway slab behavior economic choices oneway slab on beams suitable span 3 to 6m with ll 35knm2. In two way slab, the ratio of longer span l to shorter span b is less than 2. In order to demonstrate the superiority of the presented method in. The design bending moment of twoway restrained slab can be calculated as follows. Two way slabs are the slabs that are supported on four sides and the ratio of longer span l to shorter span b is less than 2. The main structural action is one way in such cases, in the direction normal to supports on two opposite edges of a rectangular panel. Code of practice for structural use of concrete 20 buildings. Application of the yield line theory for more complex situations 8. Pdf this paper presents a cuckoo optimization algorithm coa. Application of limit state method to rectangular beams for flexure, shear, bond and torsion. Design of concrete structures 14th edition, 2009, by arthur h. Deep ribs, the concrete and steel quantities are relative low expensive formwork expected. The reinforced concrete design manual sp1711 is intended to provide guidance and assistance to professionals engaged in the design of castinplace reinforced concrete structures. Design methods are given for unreinforced concrete, reinforced concrete.
Direct design method for two way slab is based on dividing the slab into strips with half the center to center spacing in each direction as shown in the figure below. Twoway slab analysis and design using equivalent frame method efm. Lecture series on design of reinforced concrete structures by prof. Use the aci 318 direct design method to design an interior bay of a flat plate slab system of multi bay building. Twoway slab analysis and design using equivalent frame method efm aci 318 states that a slab system shall be designed.
The effect of fixing the corners of the slab against lifting 5. Accurately determining the moments on a twoway slab is typically accomplished by finite element computer analysis. 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. This is the constant now recognized as the coefficient or modulus of. What is the coefficient method of a twoway slab design. Flat slabs carried on columns and edge beams or walls with no interior beams. Direct design method, that could have been named the direct analysis method because it determines or prescribes moments for different parts of the slab panel without the need to conduct structural analysis, is explained in the following sections. 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.
Twoway slab analysis and design using elastic frame method efm. Twoway slabs concrete structures eurocode eurocode standards. Institute pti design procedure for designing posttensioned slabsonground. Rectangular beams and oneway slabs page 2 of 9 two methods. Twoway slab design using the coefficient method free download as pdf file. Cornell university, david darwin university of kansas, charles dolan university of wyoming 3. When the ratio of long span to short span is less than 2, then the slab is known as a slab spanning in two directions or twoway slab. Jan, 2020 unlike bs 8110 there is no specific guidance given in eurocode 2 on how to determine the bending moments for a two way slab. The assessment of the bending moment can be carried out using any suitable method from section 5 of the code. The coefficient method was first included in the 1963 edition of the aci. Design of two way slabs by coefficient method slab is one of the basic parts of a building. Chapter 3 design of rectangular beams and oneway slabs. Twoway slabs have two way bending unlike oneway slab. Department of mechanics, materials and structures english.
Design of two way slab by usd method and wsd method slab 1 case 2 slab dimension short span,a 20 long span,b 22 m ab 0. Analysis and design of slabs two way civil engineers pk. 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. Two way slab design by direct design method as per aci 31811. Slabs of uniform thickness bending and reinforced in one direction.