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