In a flat slab building, you can do a punching shear calculation based on the reaction but, in a slab bridge, a knowledge of the distribution of shear stresses would be helpful. Sep 03, 2011 design of reinforced concrete slabs 105 2 shears vx and vv 3 woodarmer moments mxt, mxb, mvt and m 4 inplane loads nx and iv method 1 bs8110. There is no simple solution to this it is currently very difficult to calculate shear forces near point supports in slabs. They may be supported on two opposite sides only fig. Tests on three model slabs incorporating minimum reinforcement ratio, minimum depth and maximum bar spacing permitted by the australian concrete structures code showed satisfactory behaviour at service loads and ultimate loads. Floor slabs can range from a simple residential basement slab to a heavyduty industrial floor. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types.
Slabs are usually used in floor and roof construction. The following example illustrates the example building. In order to simplify the analysis and to be able to use the superposition principle for evaluating the effect of load combinations, linear analysis is generally adopted even though concrete slabs normally have a pronounced nonlinear response. Cross sectional constant defines torsional properties c x.
For this reason, some supplemental design guidance is provided when practical and technically justified. Chapter 18 concrete slab structures january 2019 183 18. Ultimate behavior of oneway spanning slab linear elastic analysis methods such as moment distribution are linear elastic methods. Apr 17, 2020 the basic approach of the method is illustrated for the simple case of a oneway spanning slab in example 8. Method statement templates is a vital plan of procedure to avoid any unnecessary accidents. Distribute moments transverse at critical sections to column and middle strip and if beams are used in the column strip, distribute column strip moments between slab and beam.
The state of development of digital computers and commercial software packages is now such that the global stress analysis is often best done using a linearelastic frame or finite element. Introduction reinforced concrete slabs are a feature of many modern buildings and bridges. For larger holes the strip method is often used but this method is not. As average area of steel per ft of width effective area of concrete in 1 ft of strip. The author discusses unevenly distributed loads, concentrated loads. Yield line design demands familiarity with failure patterns, i. Direct design method ddm for slab systems with or without beams loaded only. In any span, the max cable sag, zd depends on the concrete cover requirements and the tendon dimensions. Accordingly, main reinforcement is required in the two directions. Yield line design is a wellfounded method of designing reinforced concrete slabs, and.
When zd is determined, the prestressing force required to balance an. The basic approach of the method is illustrated for the simple case of a oneway spanning slab in example 8. Prev next the theory of the strip method for design of slabs. 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. Hillerborg strip method deformation engineering plasticity. The purpose of this paper is to provide an overview of the strip method, including design examples. Practical yield line design 4 yield line design is a robust and proven design technique. The simple strip method is used to design edge supported slabs.
Concrete slabs on grade are a very common type of concrete construction. 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. In the design of concrete slabs with openings the building codes propose instructions that are not supported by the underlying theories. A short tutorial showing how the main reinforcement in a simply supported slab is designed using ec2.
Slabs with small holes are traditionally designed using empirical methods which are described in chapter 2. Department of mechanics, materials and structures english. Strip method for slabs text strip method for slabs simple supports 4 sides wap a plan view d across x b wx along aa c mx along aa 511 this would not represent an economical or serviceable solution because it is rec ognized that curvatures, hence moments. The strip method design handbook is a thorough guide to the use of the strip method, developed by arne hillerborg, for design of reinforced concrete slabs. Bending will take place in the two directions in a dishlike form.
Continuous one way slab figure 1 shows a clear area of 12 m x 8. Many designers will recognize this as an application of the strongband concept. Example 3 solution, moments because of the hole, certain strips lack support at one end. Design of reinforced concrete slabs 105 2 shears vx and vv 3 woodarmer moments mxt, mxb, mvt and m 4 inplane loads nx and iv method 1 bs8110. To illustrate the latter method of obtaining the steel ratio r, assume a 5 in. Recommendations for finite element analysis for the design. Design of reinforced concrete structures ii twoway slabs 1 1. This pdf file contains a chapter of 23 pages with various aspects of flat slabs including four example of flat slab design.
Simple spans roof floor roof floor oneway solid slabs 50 45 45 40 twoway solid slabs supported on columns only 4548 4045 twoway waffle slabs 1m pans 40 35 35 30 beams 35 30 30 26 oneway joists 42 38 38 35 note. Background of simple design method 12 membrane forces along yield lines 2 simple design method of reinforced concrete slabs at 20 c k,b are parameters defining magnitude of membrane forces, n is a factor deduced from yield line theory, k is the ratio of the reinforcement in the shorter span to the reinforcement in the longer span. Feb 07, 2014 a short tutorial showing how the main reinforcement in a simply supported slab is designed using ec2. Microsoft word can also give you a helping hand in making your own method statement where you can save and print the file when you are done. Simple frame method in the simple frame method, each design strip is analyzed independently from the rest of the slab system using an approximate plane frame model fig. The advanced strip method a simple design tool 1982. The construction and design of concrete slabs on grade. To see their result for this slab we will find the load factor. That is, the load factor at which the uls moment equals the moment capacity.
Structural modeling and analysis of concrete floor slabs. Two examples of optimized hillerborg solutions are shown in,fig. Recommendations for finite element analysis for the design of. Only the design of slab bridge will be used for illustration. Cylinder strength at 28 days for slabs 4000 psi modulus of elasticity 4028 ksi creep coefficient 2 nonprestressed reinforcement. A slab strip of unit width is analysed using simple beam theory.
Quite popular and widely used among these methods is one using moment coefficient. Yield line vs, strip method for rc slab analysis structural. Lecture series on design of reinforced concrete structures by prof. Example building below is a partial plan of a typical floor in a castinplace reinforced concrete building.
For design, the approximate elastic or strip method for slab bridges found in article 4. Electronic examples as dynamic pdffiles for each chapter 1. Flat slab analysis, design and detailing pdf civil. This method is used even today for the design of flat slabs and flat plates and is known as the direct design method. The slab is supported on beams of size 225 x 500 mm spaced at 4. Once grasped yield line design is an exceedingly powerful design tool. The basic design procedure of a twoway slab system has five steps.
The effect of fixing the corners of the slab against lifting 5. Jul 02, 2010 lecture series on design of reinforced concrete structures by prof. Design of slab examples and tutorials by sharifah maszura syed mohsin example 2. Girma zerayohannes 48 chapter 2 strip method for slabs. A generalized strip method of reinforced concrete slab design. Approximate elastic method, or equivalent strip method aashto 4. Chapter 3 design of rectangular beams and oneway slabs. Yield strength 60 ksi modulus of elasticity 30000 ksi soil bulk modulus 150 pci allowable longterm pressure 2000 psf short term transient pressure 1. However, no matter how basic or complex the floor is, the construction method is similar and includes.
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. It is a versatile tool that challenges designers to use judgement. The finite element method is commonly used to design the reinforcement in concrete slabs. 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. Determine the area of steel required in the slab at critical sections for column and middle strips. Moment division example 6000 6000 6000 6000 6000 5000 layout of building 7000. Distribute moments transverse at critical sections to column and middlestrip and if beams are used in the column strip, distribute column strip moments between slab and beam. This simple strip method thus presented is restricted to certain. The strip method of design is relevant to many types of slabs including rectangular slabs with all sides supported and regular flat slabs with cantilevering parts.
The relevance of this work in the design of concrete slabs is discussed and. Oneway and twoway slabs university of asia pacific. The yield line and hillerborg strip methods are limit design or collapse. A generalized strip method of reinforced concrete slab. Rectangular slab with simple supports, solved by perturbation method. Example on design of slab bridge design data and specifications superstructure consists of 10m slab, 36m box girder and 10m tgirder all simply supported. Alternatively an inelastic analysis using yield line theory or hillerborgs strip method for slabs, and the plastic hinge concept for beams, may be made. In accordance with the basic assumptions in the method of hillerborg, the slab may be subdivided into several regions in function of the preferential. The example you need like this can be seen for free online, you can download the applicable document for your use. Oneway and twoway slabs oneway slabs transfer the imposed loads in one direction only. The stiffnesses of the slab and columns are based strictly on their crosssectional geometry. A second video shows how the shear resistance of the slab and its deflection are checked.
Oneway and twoway slabs oneway slabs transfer the imposed. Flat slab haunched slab a longitudinal slab is one of the least complex types of bridge superstructures. A new generalised strip method of reinforced concrete slab design is suggested which overcomes the limitations of the hillerborg method. Yield line vs, strip method for rc slab analysis haynewp structural 29 dec 08 12. Flat slab analysis, design and detailing pdf civil engineering. Reinforced concrete design 1 design of slab examples and. Dhang, department of civil engineering, iit kharagpur. Chapter 3 design of rectangular beams and oneway slabs 12. Design considerations for reinforced concrete flat slab.
An experimental programme of tests on model slabs designed by the new method is described and results are compared with the theory. Both methods use the same procedure to divide the moments so found between the middle strip and column strips of the slab and the beams if any. Oneway slabs normally design as a beam with cables running in the direction of the span at uniform centres. The strip method is usually divided into tow parts. Concrete design procedures generally follow the strength design method contained in aci318, although certain aspects of the procedures may be considered conservative relative to conventional residential foundation applications. Application of the yield line theory for more complex situations 8. Tests on three model slabs incorporating minimum reinforcement ratio, minimum depth and maximum bar spacing permitted by the australian concrete structures code showed satisfactory behaviour at service loads and ultimate loads despite the fact that bending. When designing or assessing a reinforced concrete slab, elastic analysis methods have become popular in. Design of reinforced concrete structures ii twoway slabs.
Later in 1914, nicholas proposed a method of analysis of flat slabs based on simple statics. Proceedings of the institution of civil engineers, volume 43, issue 2, 1 jun 1969 296 minimum reinforcement volumes for reinforced concrete slabs by the strip method. A simple, practical and economical design method for twoway reinforced concrete slabs, based on hillerborgs strip method, is presented. Since they are part of the same slab, their midspan deflections must be the same. Design of reinforced concrete structures ii twoway slabs 8 c. The three examples also illustrate the simple way in which moments in the slab can be found by the strip method, based on familiar beam analysis. For a slab with one edge unsupported, a reasonable basis for analysis by the simple strip method is that a strip along the unsupported edge takes a greater load per unit area than the actual load acting, i.
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