Okay, i know it is based on upper bound thorem and the solution might be unsafe. Generally, there are two types of slab which are one way and two way slabs. Design of reinforced concrete structures ii two way slabs 1 1. Designing of slabs depends upon whether it is a oneway or a two way slab, the end conditions and the loading. The output of the program for the slab in the example is shown in the following pages. Its typically used when stiffness is important or if there are abnormally heavy loads. How to determine the twoway slab design procedures step. The following example illustrates the example building. Design of reinforced concrete structures ii twoway slabs. Civilax is the knowledge base covering all disciplines in civil engineering. Slabs are usually used in floor and roof construction. The two classifications are oneway slab and twoway slab. One way slabs normally design as a beam with cables running in the direction of the span at uniform centres.
A slab strip of unit width is analysed using simple beam theory. Designing of slabs depends upon whether it is a oneway or a two way slab, the end conditions and the. The load on the slab is carried by the short span in one direction. Two way slab design by direct design method as per aci 31811. The sectional design model is appropriate for the design of a typical bridge girder, slabor other region, of components where the assumptions of traditional beam theory are valid. 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 2688 venado way rescue, ca 95672 phone. Mat or raft foundation is a large concrete slab supporting several columns in two or more rows.
Slabs having supports on less than four sides can be designed as one way. A civil engineer must know all the aspects regarding the flat floor system. The unit weight of reinforced concrete is assumed to be 24 knm3. The oneway slab is deflected in one way direction and primary reinforcement is placed in one direction whereas. Allowable stress design or working stress design wsd 2. One way slabs are such slabs in which the loads are shared only by the shorter direction of the slab.
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. Here discribed for two way simply supported slab with better solution and also told about of how to use is code in two way slab design. Twoway slabs structural engineering forum of india, sefi. Flat slab analysis, design and detailing pdf civil engineering. Design procedure steps for one way slab slab design steps. This spreadsheet performs an analysis and design of two way spanning reinforced concrete slab. I am submitting it to you and i want students or professional engineers to download it and use it for their studies or projects. Two way slab design by direct design method as per aci. If frame analyses are performed to check the flexural resistance of a slab, the design moment, m ed transferred from the slab to a column and the design shear, v ed are obtained from the relevant analysis. Two way slab design based on aci 31811 using finite element method. There are two types of slab classification based on the direction of bending occurs in these slabs. Design procedure the basic design procedure of a twoway slab system has five steps.
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. The process of design is usually the reverse of that for analysis, since it works. Because there are joists in both directions, this floor system is the strongest and will have the least deflection. Twoway slab analysis and design using equivalent frame method efm. In two way slabs shorter direction strip carry greater %age of load. Slab shear strength two way shear check the adequacy of slab thickness for punching shear two way shear at an interior column figure 4. Design of one way and two way slabs, design of staircases.
Design of slabtwo way excel sheet online civilforum. Chapter 3 design of rectangular beams and oneway slabs 12. Oneway and twoway slabs oneway slabs transfer the imposed. Limit state of collapse and limit state of serviceability. If slab is supported on all four sides and r shorter side longer side way slab. Alternate design method design procedure of two way slabs using aci moment coefficients and approved by bnbc 20 scope and limitations bnbc 6. Step 2 design forces draw panel of slab and indicate maximum design moments, shears and in.
The pca computer program pcaslab can be used to expedite the design of different slab systems. This pdf file contains a chapter of 23 pages with various aspects of flat slabs including four example of flat slab design. To see their result for this slab we will find the load factor. The coefficient method may be the simplest, easiest and the quickest approach for the design of two way slab supported by edge beam on all slab sides. Aci318 code provides two design procedures for slab systems. When zd is determined, the prestressing force required to balance an.
Slab resting on walls or sufficiently deep and rigid beams on all sides. It is used where the supporting soil has low bearing capacity. Types of one way slab one way slab may be solid hollow ribbed 6. Reinforced concrete slab design using the empirical method. That is, the load factor at which the uls moment equals the moment capacity. A three dimensional building is divided in to a series of two dimensional frames by cutting the buildings alone lines midway between columns. Beams of width and depth are provided on all column lines. Design of reinforced concrete structures ii twoway slabs 8 c. Two way 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. Analysis and design of slabs one way civil engineers pk. Flat slab system is an important division of concrete floor system.
Sep 11, 2017 design of two way slab design education. Reference 5 focused on analysis of two way ribbed slabs with. Following are the rcc slab design and detailing guidelines. Accordingly, main reinforcement is required in the two directions. Cross sectional constant defines torsional properties c x. Reinforced concrete slab design and detailing guide is456. In any span, the max cable sag, zd depends on the concrete cover requirements and the tendon dimensions. Flat slab analysis, design and detailing pdf civil. A monolithic reinforced concrete floor is to be composed of rectangular bays measuring, as shown. Design of a two way rcc slab structural engineering forum.
Here ratio of longer span of slab to the shorter span of slab is greater than 2. Here, we have tried to gather various reading materials available in the web about flat slab floor system in one place. Waffle slab two way pan joist two way joist slab, also called a waffle slab. Aug 03, 2016 the design steps have been presented in the following question how do i degisn two way slab. 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. Design procedure the basic design procedure of a two way slab system has five steps. In two way slabs, load will be carried in both the directions. 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. Ultimate behavior of oneway spanning slab linear elastic analysis methods such as moment distribution are linear elastic methods.
This condition occur when the slabs are connected monolithically with support. Application of lb ratio in first figure slab is supported on two opposite sides only. File is not passwordprotected, you may be asked for password if you open it in smartphones. Mention the parameters governing slab moment coefficients and explain their effects on moment. 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. A tendon is defined as sheathing duct, the strands within it and the corrosion inhibiting grease or grout filling its voids.
Load transfer in a one way slab, b two way slab nilson fig. Alternate design method design procedure of twoway slabs. However main reinforcement bar and distribution bar in transverse direction. The design bending moment of twoway restrained slab can be calculated as follows. The two classifications are one way slab and two way slab. Ultimate behavior of one way spanning slab linear elastic analysis methods such as moment distribution are linear elastic methods.
The other ways of analysis of twoway slabs are the direct design method and the equivalent frame method. In figure 1b, tie is shown connecting the footings. An optimal plan geometry with all same supports is a square, based on load distribution into both directions. When a slab is supported on all four sides and the ratio of long span to short span is equal or greater than two, it will be considered as one way slab. It can be used by both practicing engineers and students. Two way slab systems do not meet the limitations of the aci code. The one way slab is deflected in one way direction and primary reinforcement is placed in one direction whereas.
Seismic loads will be considered acting in the horizontal direction along either of the two. In two way slab, the ratio of longer span l to shorter span b is less than 2. Two way slab design spreadsheet the engineering community. Chapter 18 concrete slab structures january 2019 188 18. In many cases the slabs are of such proportions and are supported in such way that two way action results. For those who do not know what are the des ign requirements of a slab. Analysis and design of slabs two way civil engineers pk. Determine moments at critical sections in each direction, normally the negative moments at supports and positive moment near midspan. One way and twoway slabs one way slabs transfer the imposed loads in one direction only. I have developed a microssoft excel software for design of a two way rcc slab.
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. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types. From the slabs, the loads are transferred to the beam. Reinforced concrete slab design and detailing guidelines for depth of slab, loads on. Twoway concrete slab on beams floor analysis and design. Use the aci 318 direct design method to design an interior bay of a flat plate slab system of multi bay building. Effective depth d span ldbasic x modification factor for obtaining modification factor, the percentage of steel for slab can be assumed from 0. Preliminary design of slab thickness thickness design depends on boundary conditions supports. They may be supported on two opposite sides only fig. Design procedure of twoway slabs using aci moment coefficients. A design strip is a region assigned to a hypothetical support line that joins a line of columns and or walls in one direction. For those who do not know what are the design requirements of a slab. What are the difference between tender and contract documents.
The program covers wide range of two way slab systems and can be used for more complex slab layouts. The bearing capacity increased by combining all individual footings in to one mat since bearing capacity. Two way slabs have two way bending unlike one way slab. Determine the thickness of the slab panel using previous article. Reinforced concrete slab design and detailing guidelines for depth of slab, loads on slab, reinforcement guide for one way and two way slabs as per is 456. May 09, 2018 best is subjective, so i will give my opinion here.
Here are the steps for the design procedure for one way slab in steps. This method was provided in the american concrete institute aci in 1963 to design two way slabs carried by steel beams, deep beam, or walls. Direct design method ddm for slab systems with or without beams loaded only. The dimensions of an interior bay are shown in figure 1.
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. These materials are originally located at different websites. Design of two way floor slab system comparison of one way and two way slab behavior one way slabs. Oneway and twoway slabs university of asia pacific. Distribute moments transverse at critical sections to column and middlestrip and if. Distribute moments transverse at critical sections to. Early twoway flat slab construction was built and subjected to load tests in place and scaled models were later tested in laboratories. Bending moment and shear force of twoway slab are depend on l y l x ratio and. The specified design strength of the concrete, is 25 mpa and the specified yield strength of the reinforcement, fy, is 400 mpa. Nov 06, 2017 hello engineers, here i am uploading few sample cad files of structural plan.
Time saving design aid page 9 of 14 two way slabs pcaslab v2. Slab shear strength twoway shear check the adequacy of slab thickness for punching shear twoway shear at an interior column figure 4. 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. These are the direct design method presented in chap. This spreadsheet is compatible with microsoft excel version 20 or higher. Analysis and design of slabs two way two way edge supported slabs twoway slabs. The ratio of the total costs was found to be within the range 1. What is the laying and jointing procedure of concrete pipes. Bending will take place in the two directions in a dishlike form. Oneway spanning slabs should be treated as beams of unit width and chapter 2 should be followed except for minimum shear reinforcement. Twoway flat plate concrete floor system analysis and design. Early two way flat slab construction was built and subjected to load tests in place and scaled models were later tested in laboratories. Design strips are used to divide up the floor system in two essentially orthogonal directions in modeling the floor for design.
Before going to this topic, please read it there are two types of slab classification based on the direction of bending occurs in these slabs. Oneway slab design spreadsheet civil engineering community. Two way restrained slab if the slabs consist more than one panel or corner of the slab are prevent against lifting it is define as two way restrained slab. Dec 28, 2017 click here for latest videos check out my friends blog please send your house plans pdf files and house images ceiling. The design bending moment of two way restrained slab can be calculated as follows. Design of reinforced concrete structures ii two way slabs. Aug 15, 2016 download code one way slab design spreadsheet. Two way rcc slab designing excel sheet civil engineering. The effective depth d of two way slabs can also be assumed using cl. Twoway concrete floor slab with beams design and detailing. One way spanning slabs should be treated as beams of unit width and chapter 2 should be followed except for minimum shear reinforcement.
Design of a two way rcc slab structural engineering. Twoway slabs have two way bending unlike oneway slab. One way slab here i solve a probleam based on the one way slab, the diamentions are provided in the probleam 1st determine the aspect ration and with respect to the aspect ratio the type of slab. Twoway concrete slab with beams spanning between supports.
Rectangular beams and one way slabs page 2 of 9 two methods. Analysis of two way ribbed and waffle slabs with hidden beams. Example design of two way edgesupported solid slab. Designing of slabs depends upon whether it is a one way or a two way slab, the end conditions and the loading. The main reinforcement for twoway slab are designed in two directions which are xdirection and ydirection. Nov 27, 20 one way slab oneway slabs are those slabs with an aspect ratio in plan of 2. 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.
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