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. The dimensions of an interior bay are shown in figure 1. Reinforced concrete design 1 design of slab examples. 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.
Moduleiii design of short and long columns with axial and eccentric loading, design of isolated column footing. The oneway slab is deflected in one way direction and primary reinforcement is placed in one direction whereas. One way slabs are such slabs in which the loads are shared only by the shorter direction of the slab. Step 2 design forces draw panel of slab and indicate maximum design moments, shears and in. The steps of design were according to the aci code provisions. 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. Flat slab analysis, design and detailing pdf civil. Slab is one of the most famous part of a construction project.
Analysis and design of slabs two way civil engineers pk. A program to design of two way slab by direct design method, a report submitted to the. Design of reinforced concrete structures ii twoway slabs. In two way slabs, load will be carried in both the directions. Slabs are usually used in floor and roof construction. Difference between one way slab and two way slab simple. In two way slab, the ratio of longer span l to shorter span b is less than 2. Oneway spanning slabs should be treated as beams of unit width and chapter 2 should be followed except for minimum shear reinforcement.
Lb2 is one way slab lb procedure a oneway slab is designed by considering a onefootwide strip of slab. The design steps have been presented in the following question how do i degisn two way slab. Design of reinforced concrete structures ii two way slabs 1 1. The design bending moment of two way restrained slab can be calculated as follows. Slab shear strength two way shear check the adequacy of slab thickness for punching shear two way shear at an interior column figure 4. 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. Mention the parameters governing slab moment coefficients and explain their effects on moment. This method was provided in the american concrete institute aci in 1963 to design two. For the design of columns and beams frame analysis is done by limit state method to know the moments they are acted upon.
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 twoway slab. The ratio lb which is less than 2 is known as two way slab. Design procedure steps for one way slab slab design steps. Twoway slabs have two way bending unlike oneway slab. 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. Oneway and twoway slabs university of asia pacific. Dhang, department of civil engineering, iit kharagpur. In two way slabs shorter direction strip carry greater %age of load. Generally, there are two types of slab which are one way and two way slabs. Pdf design of reinforced concrete circular slabs by twoway.
Distribute moments transverse at critical sections to column and middlestrip and if. Designing of slabs depends upon whether it is a oneway or a two way slab, the end conditions and. 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. Accordingly, main reinforcement is required in the two directions. These conditions are set out in last section dealing with oneway ribbed slabs. Here ratio of longer span of slab to the shorter span of slab is greater than 2. One way slab being supported on two opposite sides only leads to the structural action in single direction. Design of a two way rcc slab structural engineering. For those who do not know what are the des ign requirements of a slab. This condition occur when the slabs are connected monolithically with support. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types. Twoway slab analysis and design using equivalent frame method efm aci 318 states that a slab system shall be designed by any procedure satisfying. Design of reinforced concrete structures ii twoway slabs 1 1.
Whatever may be the width of the slabs it should always be designed for a width of equal to one metre and the same design should be adopted for the rest of the slab. Pdf slabs are the flooring systems of most structures including office, commercial and residential. Top view of continuous rc circular twoway ribbed slab advertisement. Design of concrete structures 14th edition, 2009, by arthur h. Here are the steps for the design procedure for one way slab in steps. The general provisions for construction and design procedure are given in cop 20. Two way slab design by direct design method as per aci 31811. Slab designing is done depending upon the type of slab one way or two way. Manual for design and detailing of reinforced concrete to the code. Bending will take place in the two directions in a dishlike form. Two way slabs are normally supported from four sides. It is recommended to create the design of slab with the use of excel sheet as the process will be very simple and lots of time will be saved. Pdf cost optimum design of reinforced concrete simply.
They may be supported on two opposite sides only fig. Design procedure the basic design procedure of a twoway slab system has five steps. I have developed a microssoft excel software for design of a two way rcc slab. The design procedure for a uniformly loaded oneway reinforced slab can be divided in the following steps. If the ratio of long span to short span is less than or equal to 2, the slab is to be defined as two way slab or slab spanning in one direction. Design of slab examples and tutorials by sharifah maszura syed mohsin example 1. Simply supported one way slab a rectangular reinforced concrete slab is simplysupported on two masonry walls 250 mm thick and 3. Moments for design may be taken from table 3 for slabs simply supported on four sides. Interior bay dimensions 20 24 this example is to be used for educational purposes only. Therefore, primary reinforcement is presented in both directions for resisting the loads. The behaviour of reinforced concrete beam sections at ultimate loads has.
This pdf file contains a chapter of 23 pages with various aspects of flat slabs including four example of flat slab design. Use the aci 318 direct design method to design an interior bay of a flat plate slab system of multi bay building. Design procedure the basic design procedure of a two way slab system has five steps. 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. The two classifications are one way slab and two way slab. Oneway and twoway slabs oneway slabs transfer the imposed. Shear strength of beamless slabs usually a controlling factor. I am submitting it to you and i want students or professional engineers to download it and use it for their studies or projects. Slab shear strength twoway shear check the adequacy of slab thickness for punching shear twoway shear at an interior column figure 4. 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. A 2 2area 2 a c 2 2 posttensioned concrete design table 11 list of symbols used in the aci 31808 code cp area enclosed by the outside perimeter of the section, in a g gross area of concrete, in a 2 l total area of longitudinal reinforcement to resist torsion, in a o area enclosed by the shear flow path, sqin a oh area enclosed by the centerline of the outermost closed.
Design reinforcement for moments from steps 5 and 6. In twoway slabs shorter direction strip carry greater %age of load. Min and max reinforcement as a percentage of the gross csa. 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. Civilax is the knowledge base covering all disciplines in civil engineering. Cornell university, david darwin university of kansas, charles dolan university of wyoming 3.
For twoway spanning slabs the check should be carried out on the basis of the shorter span. Design of one way and two way slabs, design of staircases. The slab has to carry a distributed permanent action of 1. Reinforced concrete design to bs8110 structural design 1 lesson 5 6 4. Load transfer in a oneway slab, b twoway slab nilson fig. The design bending moment of twoway restrained slab can be calculated as follows. In two way slab, load is delivered in both the directions. Two way slabs have two way bending unlike one way slab. Lecture series on design of reinforced concrete structures by prof. 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 slab design spreadsheet civil engineering community. Aci318 code provides two design procedures for slab systems.
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