Analysis and design of slabs two way civil engineers pk. It is possible that designers who specify these arrangements of reinforcement in twoway posttensioned. There are multiple analysis methods, manual and computer analysis, available for analyzing twoway slabs. The reinforced concrete design manual sp1711 is intended to provide guidance and assistance to professionals engaged in the design of castinplace reinforced concrete structures. Experimental results by bollinger14 also confirm the role of the critical shear crack in the punching strength of slabs. Designing of slabs depends upon whether it is a oneway or a two way slab, the end conditions and the loading. Design of reinforced concrete structures by punmia pdf concrete bridges part v. The ratio lb which is less than 2 is known as two way slab. This paper introduces a strengthening technique of twoway slabs using steel plates and steel bolts. Oneway and twoway slabs oneway slabs transfer the imposed. Minimum area of reinforcement at bottom of slab minimum area of reinforcement at top of slab reinforcement in ydirection to resist m x about xaxis reinforcement in xdirection to resist m about y. Design of slabtwo way excel sheet online civilforum. The original slab reinforcement ratio was chosen as 1. Testing on two way posttensioned slabs with a banded tendon distribution2 contained neither the nonprestressed reinforcement shown in fig.
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. For better view, please read this post in landscape mode if you are on the mobile device. Typical slab reinforcement structure design detail. Introduction features in modeling and analysis distribution of moments to strips 9. When a rectangular slab is supported on all the sides and the lengthtobreadth ratio is less than two, it is considered to be a twoway slab. Determine moments at critical sections in each direction, normally the negative moments at supports and positive moment near midspan.
Twoway slabs have two way bending unlike oneway slab. Slab supported directly by columns are called flat slab. The first reinforced concrete design manual formerly titled aci design handbook was developed in. Pdf strengthening of twoway slabs using steel plates. Punching shear strength of reinforced concrete slabs without. Punching shear strength of reinforced concrete slabs without transverse reinforcement by aurelio muttoni. So from the diagram, reinforcement in the xdirection provides a moment capacity of x m parallel to the yaxis. For b oth one way and two way slab with an example.
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. 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. The unit weight of reinforced concrete is assumed to be 24 knm3. Apart from the column region, where a concentration of reinforcement becomes necessary to avoid column hinge failure fig. Reinforced concrete buildings of moderate size and height third edition.
Two way slab concrete design structural engineering. Two way rcc slab designing excel sheet civil engineering. The program covers wide range of twoway slab systems and can be used for more complex slab layouts. Reinforced concrete slab design and detailing guidelines for depth of slab, loads on slab, reinforcement guide for oneway and twoway slabs as per is. A tendon is defined as sheathing duct, the strands within it and the corrosion inhibiting grease or grout filling its voids. Distribute moments transverse at critical sections to column and middlestrip and if. Member design reinforced concrete two way spanning. These tests demonstrated that adequate, codeconformant behavior in two way posttensioned slabs fig. Accordingly, main reinforcement is required in the two directions. In twoway slabs shorter direction strip carry greater %age of load.
Mathematical structural analysis of one way 763 3 comparison between the results of finite element method and traditional method two bays one way ribbed slab is analyzed by both traditional and finite element methods to determine the induced moments of the rib. Chapter 3 design of rectangular beams and oneway slabs. A tendon may contain one or more sevenwire strands. 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. Oneway and twoway slabs university of asia pacific. Its scope includes proposing the inclusion of two new equations. In two way slab, the ratio of longer span l to shorter span b is less than 2. Draw the slab, and lebel all the reinforcement sizes and spacings. Bubbledeck is the patented integration technique of linking air, steel, and concrete in a two way structural slab. Fanella, which appeared in the october 2001 edition of structural engineer magazine.
Example on design of slab bridge design data and specifications superstructure consists of 10m slab, 36m box girder and 10m tgirder all simply supported. Typical slab reinforcement detail with the detail of distribution bar, spacing between bars etc. Two way slab design by direct design method as per aci 31811, step by step procedure and limitations of direct design method for two way slab is presented. Use the equivalent frame method efm and compare the results with spslab model results. Chapter 3 design of rectangular beams and oneway slabs 12. Twoway concrete floor slab with beams design and detailing. Slab is one of the most famous part of a construction project. Structural consideration in design of reinforced concrete. Reinforced concrete slab design using the empirical method bridgesight solutions for the aashto lrfd bridge design specifications bridgesight software tm creators of effective and reliable solutions for the worlds bridge engineers. Generally, there are two types of slab which are one way and two way slabs. While there is a dearth of published research available describing the behavior of two. Only the design of slab bridge will be used for illustration.
As they are oneway slabs i treat them as wide beams. Jun 14, 2017 download two way slab design excel sheet template. Behavior of two way slabs a rectangular slab supported on four edge supports, which bends in two orthogonal directions and deflects in the form of dish or a saucer is called two way slabs. Step 2 design forces draw panel of slab and indicate maximum design moments, shears and in plane loads, if any, per unit width of slab. It can be used by both practicing engineers and students. Design of reinforced concrete structures ii twoway slabs. 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. Typically i stay away from using live load reduction when designing the slab because it may restrict the future use of this floor. The following example illustrates the example building. When a rectangular slab is supported on all the sides and the lengthtobreadth ratio is less than two, it is considered to be. In practical, oneway is supported by only two parallel beams or walls. Analysis and design of twoway slabs page 1 chapter 3. A reinforced concrete slab is a broad, flat plate, usually horizontal, with top and bottom surfaces parallel or nearly so. Two way rcc slab designing tool in microsoft excel developed by shankar tayal a 3rd year student of school of infrastructure, indian institute of technology, bhubaneswar this is a part of his project economic design of two way rcc slabs under prof s.
Slab supported on two sides and bending takes place predominantly in one direction only is called one way slab. In this post, we are going to explain how to calculate steel quantity for the slab. Twoway flat plate concrete floor system analysis and design. Two way slabs are normally supported from four sides. The basic design procedure of a two way slab system has five steps. Two way slab is a slab in which the ratio of longer side to the shorter side is less than or equal to two. Twoway slabs structural engineering forum of india, sefi. Difference between one way slab and two way slab system. Flat plate concrete floor system does not use beams between columns or. Limit state design design design of beams and slabs a comprehensive book for reinforced concrete structures of all kind. Reinforced concrete slab design and detailing guide is456.
Behavior and reinforcement of one way slab the structural frame consists of four columns, two beams and one slab. Main reinforcementrft is provided in one direction for oneway slabs. When a slab is designed as a continuous slab, negative moment capacity of the slab shall also be checked, as will be discussed later. Approved plans were obtained and analyzed with emphasis on detailing. Typical slab reinforcement structure design detail autocad. Oneway slab supported by two beams in the design and analysis of one way slab systems a 1m strip of. Tensioning and passive reinforcement in floor slabs,4 section 3. Triangular load distribution in two way slabs civildigital. Usually, when a slab is supported by a beam the support is considered to be pinned.
They may be supported on two opposite sides only fig. Aug 23, 2017 this video describes how the the reinforcement is placed at the site. Member design reinforced concrete two way spanning slab. Layout of posttensioning reinforcement in floor slabs by dr.
Member design reinforced concrete two way spanning slab bs8110 v2015. Since slab spans in both directions, design reinforcement is provided in both the direction. This system is similar to the twoway flat plate system except there is a drop panel to provide extra thickness around the columns. Download two way slab design excel sheet template for free. 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. Would love to provide these pictures for better clarity of the viewers.
May 02, 2017 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. The specified design strength of the concrete, is 25 mpa and the specified yield strength of the reinforcement, fy, is 400 mpa. A monolithic reinforced concrete floor is to be composed of rectangular bays measuring, as shown. Punching shear strength of reinforced concrete slabs. Consider the minimum development lengthrequired for the two. Introduction in reinforced concrete construction, slabs are used to provide flat, useful surfaces. The one way slab is deflected in one way direction and primary reinforcement is placed in one direction whereas. One way shear in slab structural engineering general. Two way slab design spreadsheet the engineering community. Slab may be supported on walls or beams or columns. Thus any yield line parallel to the yaxis will be opposed by xdirection reinforcement and hence the x m capacity of the slab. The following observations can be made from the loadrotation.
One way and two way slabs one way slabs transfer the imposed loads in one direction only. Design of reinforced concrete structures ii twoway slabs 1 1. Analysis two way slabs are not direct as in one way slabs. Check slab reinforcement at exterior column for moment transfer between slab and column. Difference between one way slab and two way slab system the one way and two way slab systems are the most commonly used floor system in the reinforced concrete structure. For a reinforcement bar to reach its yield stress at a critical cross. The same goes for yield lines in the xdirection opposed by the y m capacity of the slab. The rest of the floor can be slightly thinner with less dead weight. Oneway and twoway slabs oneway slabs transfer the imposed loads in one direction only. Shrinkage and temperature reinforcement in twoway post.
Summary of bill of quantities civil works bar bending schedule. One way and two way slab reinforcement in detail at sit duration. Structural consideration in design of reinforced concrete slabs with openings. If playback doesnt begin shortly, try restarting your device. The following example illustrates the design methods presented in the pca book simplified design. In two way slabs, load will be carried in both the directions. This alternate interpretation is further supported by the analogy between one way beam and slab framing and two way posttensioned slabs with a banded tendon distribution, where no reinforcement is normally supplied parallel to and between the banded tendons. Twoway concrete slab with beams spanning between supports. Calculate the live load that can be carried by the slab shown below, if it is reinforced longitudinally as shown below. Reinforcement detailing of a slab is done based on its support conditions.
Steps to be followed for the determination of punching shear reinforcement in slabs. Atr crosssectional area of the transverse reinforcement along the development length lsy. These slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs or other types of structures. While there is a dearth of published research available describing the behavior of twoway slabs with bonded tendons, the author has received. Course objectives general by the end of this course, the student will be able to. One way spanning slabs should be treated as beams of unit width and chapter 2 should be followed except for minimum shear reinforcement. A bentup bar called as crank bar is provided to make rcc slab safe from compressive stresses. One way concrete slab bends or deflects in a direction perpendicular to the supporting. This spreadsheet performs an analysis and design of twoway spanning reinforced concrete slab. Design of reinforced concrete components of a house. However, twoway slabs with bonded tendons are widely used in other parts of the worldnotably, asia, europe, and australia. I am doing oneway slabs and hope you can clean up my doubts about the one way shear in slab. Reinforced concrete slab design using the empirical method. Drawing shows typical slab structure detail through plan, sections and required legendguidelines.
The flexural resistance in the positive bending, as well as the vertical shear capacity, determined per ansisdi c2017 are checked for simple supported slabs. Beams of width and depth are provided on all column lines. Simplified design of reinforced concrete buildings, fourth edition, 2011. Oneway slabs transfer the imposed loads in one direction only. Example design of two way edgesupported solid slab. Behavior and reinforcement of oneway slab the structural frame consists of four columns, two beams and one slab. Bending will take place in the two directions in a dishlike form. Our friend mohit sharma has already highlighted the essentials for a one way slab. It is possible that designers who specify these arrangements of reinforcement in two way posttensioned.
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. Design of slab two way excel sheet design spreadsheets the specified design strength of the concrete, is 25 mpa and the specified yield strength of the reinforcement, fy, is 400 mpa. Design of reinforced concrete slabs 115 1 the first failure zone is from the face of the loaded area to the perimeter 1. Figure 1 twoway slab with beams spanning between all supports. Unless otherwise noted, all referenced table, figure, and. Normally it works fine but this time after carrying out the calculations the slabs fail in shear because of there are some huge point loads near the support. Difference between one way slab and two way slab simple. Bubble deck slab joints have a chamfer on the inside to ensure that concrete surrounds each bar and does not allow a direct route to air from the rebar surface. That isnt to say that it cant be used for twoway slabs. Design of reinforced concrete structures ii two way slabs 1 1.
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