Later in 1914, nicholas proposed a method of analysis of flat slabs based on simple statics. Recommendations for finite element analysis for the design. The construction and design of concrete slabs on grade. Two examples of optimized hillerborg solutions are shown in,fig. To illustrate the latter method of obtaining the steel ratio r, assume a 5 in. Hillerborg strip method deformation engineering plasticity. 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. Moment division example 6000 6000 6000 6000 6000 5000 layout of building 7000. Alternatively an inelastic analysis using yield line theory or hillerborgs strip method for slabs, and the plastic hinge concept for beams, may be made. However, no matter how basic or complex the floor is, the construction method is similar and includes. To see their result for this slab we will find the load factor.
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. The purpose of this paper is to provide an overview of the strip method, including design examples. Design of reinforced concrete structures ii twoway slabs 8 c. Accordingly, main reinforcement is required in the two directions. Chapter 3 design of rectangular beams and oneway slabs 12. A generalized strip method of reinforced concrete slab. 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. Example on design of slab bridge design data and specifications superstructure consists of 10m slab, 36m box girder and 10m tgirder all simply supported. The advanced strip method a simple design tool 1982. 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. Ultimate behavior of oneway spanning slab linear elastic analysis methods such as moment distribution are linear elastic methods.
For design, the approximate elastic or strip method for slab bridges found in article 4. Yield line design demands familiarity with failure patterns, i. Oneway slabs normally design as a beam with cables running in the direction of the span at uniform centres. 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. The slab is supported on beams of size 225 x 500 mm spaced at 4.
Slabs with small holes are traditionally designed using empirical methods which are described in chapter 2. Chapter 3 design of rectangular beams and oneway slabs. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types. That is, the load factor at which the uls moment equals the moment capacity. Cylinder strength at 28 days for slabs 4000 psi modulus of elasticity 4028 ksi creep coefficient 2 nonprestressed reinforcement. Bending will take place in the two directions in a dishlike form. The example you need like this can be seen for free online, you can download the applicable document for your use. 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. 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.
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. The basic design procedure of a twoway slab system has five steps. The stiffnesses of the slab and columns are based strictly on their crosssectional geometry. The following example illustrates the example building.
For this reason, some supplemental design guidance is provided when practical and technically justified. Floor slabs can range from a simple residential basement slab to a heavyduty industrial floor. 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. It is a versatile tool that challenges designers to use judgement.
Slabs are usually used in floor and roof construction. 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. The yield line and hillerborg strip methods are limit design or collapse. 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. A generalized strip method of reinforced concrete slab design. 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 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. 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. A second video shows how the shear resistance of the slab and its deflection are checked. 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. Yield line vs, strip method for rc slab analysis haynewp structural 29 dec 08 12. The author discusses unevenly distributed loads, concentrated loads. This method is used even today for the design of flat slabs and flat plates and is known as the direct design method. Reinforced concrete design 1 design of slab examples and. A slab strip of unit width is analysed using simple beam theory. They may be supported on two opposite sides only fig. Many designers will recognize this as an application of the strongband concept. Oneway and twoway slabs oneway slabs transfer the imposed loads in one direction only. A simple, practical and economical design method for twoway reinforced concrete slabs, based on hillerborgs strip method, is presented. Approximate elastic method, or equivalent strip method aashto 4.
Concrete slabs on grade are a very common type of concrete construction. When designing or assessing a reinforced concrete slab, elastic analysis methods have become popular in. Oneway and twoway slabs university of asia pacific. Chapter 18 concrete slab structures january 2019 183 18. Determine the area of steel required in the slab at critical sections for column and middle strips. Design considerations for reinforced concrete flat slab. Girma zerayohannes 48 chapter 2 strip method for slabs. Once grasped yield line design is an exceedingly powerful design tool. Direct design method ddm for slab systems with or without beams loaded only. Apr 17, 2020 the basic approach of the method is illustrated for the simple case of a oneway spanning slab in example 8. 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. When zd is determined, the prestressing force required to balance an. Application of the yield line theory for more complex situations 8.
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. The finite element method is commonly used to design the reinforcement in concrete slabs. This simple strip method thus presented is restricted to certain. Cross sectional constant defines torsional properties c x.
Structural modeling and analysis of concrete floor slabs. In accordance with the basic assumptions in the method of hillerborg, the slab may be subdivided into several regions in function of the preferential. Recommendations for finite element analysis for the design of. As average area of steel per ft of width effective area of concrete in 1 ft of strip. The strip method is usually divided into tow parts.
Quite popular and widely used among these methods is one using moment coefficient. A new generalised strip method of reinforced concrete slab design is suggested which overcomes the limitations of the hillerborg method. Yield strength 60 ksi modulus of elasticity 30000 ksi soil bulk modulus 150 pci allowable longterm pressure 2000 psf short term transient pressure 1. Introduction reinforced concrete slabs are a feature of many modern buildings and bridges. Rectangular slab with simple supports, solved by perturbation method. Method statement templates is a vital plan of procedure to avoid any unnecessary accidents. Example building below is a partial plan of a typical floor in a castinplace reinforced concrete building. Dhang, department of civil engineering, iit kharagpur. Design of slab examples and tutorials by sharifah maszura syed mohsin example 2. 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. There is no simple solution to this it is currently very difficult to calculate shear forces near point supports in slabs. Continuous one way slab figure 1 shows a clear area of 12 m x 8. Design of reinforced concrete structures ii twoway slabs 1 1.
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. Lecture series on design of reinforced concrete structures by prof. Example 3 solution, moments because of the hole, certain strips lack support at one end. The basic approach of the method is illustrated for the simple case of a oneway spanning slab in example 8. Design of reinforced concrete structures ii twoway slabs. Flat slab analysis, design and detailing pdf civil engineering. Only the design of slab bridge will be used for illustration. Practical yield line design 4 yield line design is a robust and proven design technique.
The relevance of this work in the design of concrete slabs is discussed and. Feb 07, 2014 a short tutorial showing how the main reinforcement in a simply supported slab is designed using ec2. 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. Department of mechanics, materials and structures english. 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. 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. Flat slab haunched slab a longitudinal slab is one of the least complex types of bridge superstructures. Since they are part of the same slab, their midspan deflections must be the same. Jul 02, 2010 lecture series on design of reinforced concrete structures by prof. In any span, the max cable sag, zd depends on the concrete cover requirements and the tendon dimensions. For larger holes the strip method is often used but this method is not. Oneway and twoway slabs oneway slabs transfer the imposed. Flat slab analysis, design and detailing pdf civil. Electronic examples as dynamic pdffiles for each chapter 1.
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. Yield line vs, strip method for rc slab analysis structural. Prev next the theory of the strip method for design of slabs. 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. The effect of fixing the corners of the slab against lifting 5. Yield line design is a wellfounded method of designing reinforced concrete slabs, and. A short tutorial showing how the main reinforcement in a simply supported slab is designed using ec2.