Slabs and flat slabs lecture 5 19 th october 2016 contents lecture 5 designing for shear in slabs including punching shear detailing solid slabs flat slab design includes flexure worked example exercise punching shear. Aci318 code provides two design procedures for slab systems. Its scope includes proposing the inclusion of two new equations. The following example illustrates the design methods presented in aci 31805 and ibc 2003. In two way slab, the ratio of longer span l to shorter span b is less than 2. This condition occur when the slab are supported at four side of the beams or walls and the ratio of long span to short span is equal or less than 2. Prior to the 1950s, two way waffle slabs and two way flat slabs were designed and constructed with column capitals and some with drop panels. The slab position, visible in your attached images, reflects the situation where two nearby slabs exist in such a way that one slab is at a slightly higher level than the other. The basic design procedure of a twoway slab system has five steps. Critical section a distance d from the face of column or capital.
The floor system consists of six panels in each direction. Two way columnsupported slabs two way columnsupported slabs. Example design of two way edgesupported solid slab. Design of flat slab with drop in safe 2016 part youtube. In the slab with drop panel examples presented herein, it will be assumed that the designer, faced with a live load and span requiring an excessively large col. Flat slabs are twoway slabs supported by pointlike.
Design of a two way slabs for punching shear resistance. It shows possible solutions of two way prestressed floors depending on different factors. Slab is one of the most famous part of a construction project. Flat slab with column head flat slab with drop panel and column head. Structural redesign two way slab drop panels my redesign of fordham place will comprise of a 9 flat slab with 5.
Oct052018 two way flat slab concrete floor with drop panels system analysis and design csa a23. Determine the thickness of the slab panel using previous article. M ed is that part of the unbalanced slab bending moments that is transferred into the column at the support. Waffle slabs are able to carry heavier loads and span longer distances than flat slab. Definition of beamtoslab stiffness ratio, accounts for. Drop panels increase the shear strength of flat slab floor. Before the start of two way slab design, slab depth should be determined in addition to specify column strips and middle strips. In this example, the calculating value of the effective depth d v is equal to the effective depth d minus the concrete cover c on the bottom surface of the slab.
A civil engineer must know all the aspects regarding the flat floor system. Slab are considered as oneway if the main reinforcement is designed only in one direction. They may be supported on two opposite sides only fig. Two way slabs have two way bending unlike one way slab. Posttension two way slab two way slab flat slab w drop panels stair slab one way slab simple supt. Distribute moments transverse at critical sections to column and middlestrip and if. Analysis and design of slabs two way civil engineers pk. Oneway slab on beams suitable span 3 to 6m with ll 35knm2. Drop in slabs concrete design structural engineering.
A projection below the slab used to reduce the amount of negative reinforcement over a column or the minimum r. Download file pdf flat slab manual design bs flat slab manual design bs flat slab design example part 1 how to design a flat slab, step by step explained in this video. So part of the load is carried by one set and the remainder by the other. A potential diagonal crack extends in a plane across the entire width l2 of the slab. Two way flat slab concrete floor with drop panels system analysis and design design the concrete floor slab system shown below for an intermediate floor considering partition weight 20 psf, and unfactored live load 60 psf. History of two way slabs the feeling at start that only part of the load to be carried in each direction, so that statics somehow did not apply to slab construction. Pdf twoway flat slab concrete floor with drop panels. Department of mechanics, materials and structures english courses. Design the 4 marked slab panels of an ordinary house.
Materials used for this redesign is normal weight concrete with compressive strength of 4ksi and steel rebar with a yield stress of 60 ksi. Csi etabs 2016flat slab design, strip design and punching. A six storey building for a commercial complex has plan dimensions as shown in figure 1. Fundamentals of post tensioned design for buildings. Introduction in reinforced concrete construction, slabs are used to provide flat, useful surfaces. Design and detailing for bending moment i division of panels and bending moments flat slab panels are divided into column strips and middle strips as shown in figure 1. Part two of the course was example intensive, and key concepts were introduced along the way. Analysis and design of twoway slabs page 1 chapter 3. Pdf historical perspective on the evolution of twoway slab design. Analysis and design of two way slabs page 4 simple beam, uniformly loaded by its share of q. Introduction within the last several years there has been a lot of interest in a design procedure for the. As mentioned, drop panels reduce the stresses due to shear and negative bending moment around the columns.
Department of mechanics, materials and structures english. Feb 22, 2018 civil engineering for construction informatics csi etabs 2016flat slab design, strip design and punching shear check please have a look in this video thank subscribe our youtube channel to get. The two way slab shown in figure below has been assumed to have a thickness of 7. Using a drop panel without a column capital in flat. A flat slab is a twoway slab reinforced in two directions that usually does not have beams or girders, and the loads are transferred directly to the supporting columns. My redesign of fordham place will comprise of a 9 flat slab with 5. In this article, it is assumed that slab thickness is determine but calculation of column and middle strips is.
The lateral loads are independently resisted by shear walls. The thickened portion ie the projection below the slab is called drop or drop panel. In such a case, drop may be at any location, provided it is properly. The basic design procedure of a two way slab system has five steps. Design considerations for reinforced concrete flat slab. The slab has to carry a distributed permanent action of 1. Framing dead load selfweight superrimposed dead load 25 psf partitions, me, misc. What is the difference between a drop panel and a column. Here the slab or slab panel is supported along its four edges by relatively deep, stiff, monolithic concrete beams or walls or steel girders. Minimum slab thickness for two way construction slabs without drop panels meeting. In lieu of detailed calculation for deflections, csa a23. Design procedure of twoway slabs using aci moment coefficients.
Flat slab analysis, design and detailing pdf civil. Flat slab seminar report, ppt, pdf for civil engineering. 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. Nov 30, 2018 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. Bending moment and shear force of twoway slab are depend on l y l x ratio and. Tn342 design example 2way mondada 093090 adapt corporation.
Column heads reduce the clear or effective span, and therefore, reduce the moment in the flat slab floor drop panel is. Reinforced concrete design 1 design of slab examples. This condition occur when the slabs are connected monolithically with support. Pdf the article is about design of prestressed slabs. Twoway flat slab concrete floor with drop panels system. His analysis suggested that the current slab design. Beams of width and depth are provided on all column lines. Without drop panels with drop panels yield stress f y, psi exterior panels interior panels exterior panels interior. Basic steps in two way slab design choose layout and type of slab. No redistribution is allowed when method 1 or method 2 of analysis in section 3. Design the concrete floor slab system shown below for an intermediate floor considering partition weight 20 psf, and unfactored live load 60 psf.
The same is true for a two way slab or any other floor system where. Design rules of thumb in the early stages of a project, we are often asked how large structural elements will be before we have had a chance to perform the nec. In two way slabs, load will be carried in both the directions. Column heads reduce the clear or effective span, and therefore, reduce the moment in the flat slab floor. These slabs do not have beams but they have drop panels or.
Summary of design procedure for two way edge supported solid slabs using the. Punching shear on flat slabs, columns drop panels, and the. A floor slab in a building where stability is provided by shear walls. This report is intended to serve as a manual of good practice for the design of prestressed concrete flat slabs in addition to the recommended procedures, other methods are described for the sake of completeness and to compare different methods of design. Moreover, lower slab is a cantilever, acting as a support for the free edge of of upper slab. In this example, the latter option will be used to achieve better understanding for the design of twoway slab with drop panels often called flat slab. Twoway flat slab concrete floor with drop panels system analysis and design. Download two way slab design excel sheet template for free. This method was provided in the american concrete institute aci in 1963 to design twoway slabs carried by steel beams, deep beam, or walls. The main reinforcement for twoway slab are designed in two directions which are xdirection and ydirection. Design of slab examples and tutorials by sharifah maszura syed mohsin example 1.
The hollow tile and concrete slab is a type of waffle slab that dates back to at least 1918 gamble et al. Department of mechanics, materials and structures english courses reinforced concrete structures code. How to design a two way slab free download as powerpoint presentation. Oneway and twoway slabs oneway slabs transfer the imposed. Determine moments at critical sections in each direction, normally the negative moments at supports and positive moment near midspan. Twowayconcreteslabfloorwithdroppanelsdesigndetailing. Pdf reinforced concrete twoway slabs have evolved in the past century. In some cases, the section of column at top as it meets the floor slab or drop panel, is enlarged so as to increase primarily the perimeter of the critical section, for shear and increasing the capacity of slab for resisting twoway shear and to reduce ve bm at the support. Flat slab analysis, design and detailing pdf flat slab system is an important division of concrete floor system. This condition occur if the slab supported by two side of beam or walls. Bending will take place in the two directions in a dishlike fo. If we have a drop panel, what is the use of the extra drop assuming it is less or larger than the slab thickness.
Contains all design checks required by the american concrete institute code and all the conditions that must be met during the design process. Hwang and moehle 1993 carried out an experimental study on nine panel model having a slab supported without beams, drop panels, slab shear reinforcement. Two way flat slab concrete floor with drop panels system analysis and design. It is convenient to think of such slabs as consisting of two sets of parallel strips, in each direction and intersecting each other. Effects of inclusion of boundary condition factor in the proposed h min equation were studied and. A reinforced concrete slab is a broad, flat plate, usually horizontal, with top and bottom surfaces parallel or nearly so. Redistribution of 10% may be allowed when method 3 or method 4 is adopted. Flat slabs are two way slabs supported by pointlike supports. Drops should be ignored if the smaller dimension of the drop is less than onethird of the smaller dimension of the panel. A monolithic reinforced concrete floor is to be composed of rectangular bays measuring, as shown.
Slab resting on walls or sufficiently deep and rigid beams on all sides. This educational solved example for the design of reinforced concrete flat slab with drop panel, and check for punching shear. Two way slab design by direct design method as per aci 31811. When a rectangular slab is supported on all the sides and the lengthtobreadth ratio is less than two, it is considered to be a two way slab. Pdf design of reinforced concrete flat slab with drop panel. The flat slab is a two way reinforced concrete slab that usually does not have beams and girders, and the loads are transferred directly to the supporting concrete columns the column tends to punch through the slab in flat slabs, which can be treated by three methods using a drop panel and a column capital in flat slab. Two types of shear may be critical in the design of the flat slabs. In this example, the latter option will be used to achieve better understanding for the design of twoway slab with drop panels often called flat. In 1914 nichols used statics to compute the total moment in a slab panel. Oneway and twoway slabs university of asia pacific.
Bending will take place in the two directions in a dishlike form. The reinforcement for the column strip was design for the direction from easttowest only. Analysis and design of slabs two way two way edge supported slabs two way slabs. The design bending moment of twoway restrained slab can be calculated as follows. The building is located in seismic zone iii on a site with medium soil. Flat slab analysis, design and detailing pdf civil engineering. Minimum thickness of slabs without interior beams without drop panels with drop panels. One way and two way slabs one way slabs transfer the imposed loads in one direction only. Manual for design and detailing of reinforced concrete to the september 20 code of practice for structural use of concrete 20 2. Design by the direct design method a typical interior flat slab with drop panels to carry a dead load of 7.
Oneway and twoway slabs oneway slabs transfer the imposed loads in one direction only. Part three we will now continue with the study of two way, posttensioned slab systems, including a complete design example using the equivalent frame concept. A waffle slab is a two way concrete slab reinforced by ribs in two directions. Example slab a flat plate floor system with panels 24 by 20 ft is supported on 20 in. Shear strength of flat slab is increased by using column heads. 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. Shear strength of beamless slabs usually a controlling factor. Two way edgesupported slabs two way edgesupported slabs. Extend horizontally from center line column at least 16 center line span.
The column lends to punch through the slab, which can be treated by three methods a. Flat slab with drop caps mondana building floor system roya construction building division. 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. In this article, it is assumed that slab thickness is determine but calculation of column and middle strips is explained in the following section. Pdf design of reinforced concrete flat slab with drop. 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. Simply supported one way slab a rectangular reinforced concrete slab is simplysupported on two masonry walls 250 mm thick and 3. Distribution of moments in reinforced concrete slabs with continuous drop panels. Design of reinforced concrete structures ii two way slabs 1 1. The design shear force can be reduced to account for the loads applied inside the outer perimeter. Slab with drop and column with head design step of flat slab link to click here. Unless otherwise noted, all referenced table, figure, and equation numbers are from these books. Manual for design and detailing of reinforced concrete to. If slab supported by four side of beams or walls, the slab is considered one way if ratio of long span ly to short span lx greater than 2.
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. Distribution of moments in reinforced concrete slabs with continuous drop panels article pdf available in canadian journal of civil engineering 291. Check the drop panel dimensional limitations as follows. Design of reinforced concrete structures ii twoway slabs. At any point, such slabs are curved in both directions resulting in biaxial bending moments. Pdf distribution of moments in reinforced concrete slabs. How to design flat slab with drop panel in robot duration. Using a column capital without drop panel in flat slab. A of the part slab was designed for gravity and wind load in accordance with aci 31883. To compare these systems, a typical interior panel was selected from the northeast wing, which is highlighted in figure 1 on page 7.