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. Please read the lauses mentioned in the video while solving the problem. Design procedure the basic design procedure of a two way slab system has five steps. In two way slabs shorter direction strip carry greater %age of load.
Slab shear strength twoway shear check the adequacy of slab thickness for punching shear twoway shear at an interior column figure 4. These conditions are set out in last section dealing with one way ribbed slabs. Design of slab examples and tutorials by sharifah maszura syed mohsin example 1. Ce 403, fall 20 oneway slab design 2 4 aci 31811 referenced pp 2 4 typical concrete floor systems copied from ceco concrete construction pamphlet design procedure a oneway slab is designed by considering a onefootwide strip of slab. Alternate design method design procedure of twoway slabs using aci moment coefficients and approved by bnbc 20 scope and limitations bnbc 6. Preliminary design of slab thickness thickness design depends on boundary conditions supports. Bending will take place in the two directions in a dishlike form. Two way slabs have two way bending unlike one way slab. Design of reinforced concrete structures ii twoway slabs 1 1. Aci 318 states that a slab system shall be designed by any procedure satisfying equilibrium and. In two way slab, the ratio of longer span l to shorter span b is less than 2. Chapter 18 concrete slab structures january 2019 188 18.
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. Distribute moments transverse at critical sections to column and middlestrip and if. Nov 27, 20 one way slab oneway slabs are those slabs with an aspect ratio in plan of 2. Here are the steps for the design procedure for one way slab in steps. The one way slab is deflected in one way direction and primary reinforcement is placed in one direction whereas. Slabs are usually used in floor and roof construction.
The procedure of the design of twoway slabs will have all the six steps mentioned in sec. One way spanning slabs should be treated as beams of unit width and chapter 2 should be followed except for minimum shear reinforcement. In this example, an interior strip of a flat plate floor system is designed and detailed for the effects of gravity loads according to aci 31805. Efm is the most comprehensive and detailed procedure provided by the aci 318 for the analysis and design of twoway slab systems where. Flat slab system is an important division of concrete floor system. Types of one way slab one way slab may be solid hollow ribbed 6. Load transfer in a oneway slab, b twoway slab nilson fig. Here the ratio of longer span of slab to the shorter span of slab is less or equals to 2. 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.
Generally, there are two types of slab which are one way and two way slabs. Calculate aspect ratio aspect ratio 2 longer spanshorter span 2. Design procedure of two way slabs using aci moment coefficients. This strip is designed basically as if it were a 12inchwide beam, t inches thick. The pca computer program pcaslab can be used to expedite the design of different slab systems. An optimal plan geometry with all same supports is a square, based on load distribution into both directions. Twoway flat plate concrete floor system design structurepoint. Alternate design method design procedure of twoway slabs.
Jul 02, 2010 lecture series on design of reinforced concrete structures by prof. The dimensions of an interior bay are shown in figure 1. Simply supported one way slab a rectangular reinforced concrete slab is simplysupported on two masonry walls 250 mm thick and 3. Reference 5 focused on analysis of twoway ribbed slabs with. The design bending moment of twoway restrained slab can be calculated as follows. Two way slabs are normally supported from four sides. Design of two way slabs is 456 limit state method youtube. Twoway slabs have two way bending unlike oneway slab. They may be supported on two opposite sides only fig. The oneway slab is deflected in one way direction and primary reinforcement is placed in one direction whereas. The basic design procedure of a twoway slab system has five steps.
Twoway concrete slab on beams floor analysis and design. 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. Oneway and twoway slabs oneway slabs transfer the imposed. 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. A rectangular reinforced concrete slab is simply supported on two masonry walls 250 mm thick and. Lecture series on design of reinforced concrete structures by prof. This condition occur when the slabs are connected monolithically with support. Assume partitions cannot be damaged by deflections. Difference between one way slab and two way slab simple. The design bending moment of two way restrained slab can be calculated as follows. The program covers wide range of two way slab systems and can be used for more complex slab layouts. Lb2 is one way slab lb des ign requirements of a slab. In two way slabs, load will be carried in both the directions. Oct 27, 2016 one way slab is a slab which is supported by beams on the two opposite sides to carry the load along one direction.
In twoway slabs shorter direction strip carry greater %age of load. 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. However main reinforcement bar and distribution bar in transverse direction. Design procedure the basic design procedure of a twoway slab system has five steps. In this video deisgn of two way slabs has been covered using is 456.
Determine the thickness of the slab panel using previous article. Pdf this research introduces a new simple, efficient, and practical procedure to design the reinforced concrete rc circular slabs which have. Analysis of two way ribbed and waffle slabs with hidden beams. For those who do not know what are the des ign requirements of a 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. Determine moments at critical sections in each direction, normally the negative moments at supports and positive moment near midspan. Use i wsd, ii usd to design the twoway slab shown below, carrying floor finish 30 psf, random wall 50 psf and live load 60 psf given. 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. Oneway and twoway slabs university of asia pacific. Use the aci 318 direct design method to design an interior bay of a flat plate slab system of multi bay building. This method was provided in the american concrete institute aci in 1963 to design twoway slabs carried by steel beams, deep beam, or walls.
May 15, 2020 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. Pdf design of reinforced concrete circular slabs by twoway. Reinforced concrete design 1 design of slab examples. Procedures of two way slab design by direct design method. One way and twoway slabs one way slabs transfer the imposed loads in one direction only. One way slab design how to design one way slab daily civil. I am submitting it to you and i want students or professional engineers to download it and use it for their studies or projects. Verandah slab is a type of one way slab, where the slab is spanning in the shorter direction.
Design of reinforced concrete structures ii two way slabs 1 1. The ratio lb which is less than 2 is known as two way slab. Flat slab analysis, design and detailing pdf civil engineering. The load on the slab is carried by the short span in one direction. Design of reinforced concrete structures ii twoway slabs. Slab shear strength two way shear check the adequacy of slab thickness for punching shear two way shear at an interior column figure 4. 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. Dhang, department of civil engineering, iit kharagpur. Design procedure of twoway slabs using aci moment coefficients. How to determine the twoway slab design procedures stepby. Oneway spanning slabs should be treated as beams of unit width and chapter 2 should be followed except for minimum shear reinforcement.
Aci 31811 code provides two methods for two way slab design one of which is direct design method. One way slab is supported by two parallel beams or walls. Analysis and design of slabs two way civil engineers pk. 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. Step 2 design forces draw panel of slab and indicate maximum design moments, shears and in. Accordingly, main reinforcement is required in the two directions. In one way slab, the ratio of longer span l to shorter span b is equal or greater than 2, i. Difference between one way slab and two way slab daily civil.
Design of a two way rcc slab structural engineering forum. Distribute moments transverse at critical sections to. Twoway slabs structural engineering forum of india, sefi. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types. Two way slab being supported on four sides the load will be carried in both the directions. A combination of these values will determine the slab stresses at the time of stressing and at service loads. Dec 20, 2017 in this video deisgn of two way slabs has been covered using is 456. Here, we have tried to gather various reading materials available in the web about flat slab floor system in one place. 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. Application of lb ratio in first figure slab is supported on two opposite sides only. The procedure of the design of two way slabs will have all the six steps mentioned in sec. Calculation of approximate depth from deflection criteria cl 23. 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. The two classifications are oneway slab and twoway slab.
Design procedure steps for one way slab slab design steps. Load transfer in a one way slab, b two way slab nilson fig. Reinforced concrete design 1 design of slab examples and. There are two types of slab classification based on the direction of bending occurs in these slabs. Two way slab design by direct design method as per aci 31811. Design of a two way rcc slab structural engineering. The ratio of the total costs was found to be within the range 1. One way slab oneway slabs are those slabs with an aspect ratio in plan of 2. 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. Reference 5 focused on analysis of two way ribbed slabs with. The following example illustrates the example building. The output of the program for the slab in the example is shown in the following pages. Twoway concrete slab with beams spanning between supports. I have developed a microssoft excel software for design of a two way rcc slab.
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