Types of one way slab one way slab may be solid hollow ribbed 6. Plan view of floor system assume partitions will not be damaged by deflections. One way spanning slabs should be treated as beams of unit width and chapter 2 should be followed except for minimum shear reinforcement. The ratio of the total costs was found to be within the range 1. Cornell university, david darwin university of kansas, charles dolan university of wyoming 3. One way slab 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. Determine moments at critical sections in each direction, normally the negative moments at supports and positive moment near midspan. Twoway concrete floor slab with beams design and detailing csa a23. This section will explain how the direct design method is used. Simply supported one way slab a rectangular reinforced concrete slab is simplysupported on two masonry walls 250 mm thick and 3. Simply supported slab upliftment of corners continuous slab no upliftment. If slab is supported on all four sides and r shorter side longer side 2 is one way slab lb london job ref. The following example illustrates the example building. Aci 31811 code provides two methods for two way slab design one of which is direct design method. May 02, 2017 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 oneway slabs transfer the imposed. No certain method can be found in the design codes or references for designing twoway slabs subjected to concentrated loads.
How accurate are the aisc design guide 11 predictions for. Twoway slabs belong to the types of construction forms made with reinforced concrete. The design steps have been presented in the following question how do i degisn two way slab. Aug 03, 2016 the design steps have been presented in the following question how do i degisn two way slab. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types. Load transfer in a oneway slab, b twoway slab nilson fig. Reduced cross section of a reinforced concrete beam. Difference between one way slab and two way slab simple. Two way slabs have two way bending unlike one way 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. Oneway concrete slab design part 1 concept explained and. Twoway flat plate concrete floor system analysis and design. Download the design of reinforced concrete slabs in pdf. Difference between one way slab and two way slab system.
Direct design method, that could have been named the direct analysis method because it determines or prescribes moments for different parts of the slab panel without the need to conduct structural analysis, is explained in the following sections. Accurately determining the moments on a two way slab is typically accomplished by finite element computer analysis. Ce 433, fall 2006 slab design example 1 6 design a oneway slab for an exterior bay of a multistory office building using the information specified below. The behavior and analysis of twoway simply supported.
Here ratio of longer span of slab to the shorter span of slab is greater than 2. The horizontal shear design according to ec4 offers two approaches which both necessitate serious laboratory work. Min and max reinforcement as a percentage of the gross csa. Department of mechanics, materials and structures english. It is an effective, inexpensive, and extensively recognized structural system. 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.
Difference between one way slab and two way slab system the one way and two way slab systems are the most commonly used floor system in the reinforced concrete structure. Analysis and design of slabs one way civil engineers pk. One way slab being supported on two opposite sides. Chapter 3 design of rectangular beams and oneway slabs. Slabs having supports on less than four sides can be designed as one way. Determine moments at critical sections in each direction, normally the negative moments at. Abstractdesigning twoway slabs under transverse concentrated loads is one of the challenges in designing such structures. They may be supported on two opposite sides only fig. Oneway spanning slabs should be treated as beams of unit width and chapter 2 should be followed except for minimum shear reinforcement. The total load of twoway slab loaded with uniformly distributed load and supported on all the four edges is assumed to be transmitted to the supporting walls or edge beams in the manner as shown in fig. In twoway slabs shorter direction strip carry greater %age of load. I have developed a microssoft excel software for design of a two way rcc slab.
Unless otherwise noted, all referenced table, figure, and equation. Dissatisfaction with results of previously required procedures of analysis and design for twoway slabbeam systems was the original reason for the massive research upon twoway slab systems begun about 1955. The one way slab is deflected in one way direction and primary reinforcement is placed in one direction whereas. Dissatisfaction with results of previously required procedures of analysis and design for two way slab beam systems was the original reason for the massive research upon two way slab systems begun about 1955. Two way slabs are normally supported from four sides. Master of science and hereby certify that, in their opinion, it is worthy of acceptance. The program covers wide range of two way slab systems and can be used for more complex slab layouts. Reinforced concrete design to bs8110 structural design 1. Accordingly, main reinforcement is required in the two directions. The design bending moment of two way restrained slab can be calculated as follows. For those who do not know what are the des ign requirements of a slab. In two way slab, load is delivered in both the directions. In two way slabs, load will be carried in both the directions. Oneway and twoway slabs university of asia pacific.
Slab shear strength two way shear check the adequacy of slab thickness for punching shear two way shear at an interior column figure 4. However, plastic method can be the best method for designing such cases of twoway slabs. In two way slabs shorter direction strip carry greater %age of load. The two classifications are one way slab and two way slab. What is the design of a one way slab and a two way slab. Design of slabs direct design method civil engineering.
Design of twoway slabs for oneway shear and for twoway shear. Reference 5 focused on analysis of two way ribbed slabs with. Two way slab design design of two way slab rc design. Reference 5 focused on analysis of twoway ribbed slabs with. Reinforced concrete design 1 design of slab examples and.
Design of a two way rcc slab structural engineering forum. Rectangular beams and one way slabs page 2 of 9 two methods. Design the slab system shown in figure 1 for an intermediate floor where the. Nov 27, 20 one way slab oneway slabs are those slabs with an aspect ratio in plan of 2. Aci 318 provides two alternative methods for designing twoway slabs for concrete, the equivalent frame method. Nov 04, 2017 in the first part of this series, we explain the concept of one way load transfer in concrete slabs and how to determine the minimum slab thickness based on deflection criteria. Bridge approach slab analysis and design incorporating elastic soil support presented by. Design of concrete structures 14th edition, 2009, by arthur h. Here are the steps for the design procedure for one way slab in steps. Design of slab examples and tutorials by sharifah maszura syed mohsin example 1.
These slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs or other types of structures. Direct design method of flat plates per aci 31802 two way slabs are inherently difficult to analyze by conventional methods of statics because of the two way bending occurring. 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. 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. Reinforced concrete design to bs8110 structural design 1 lesson 5 6 4. One way slab oneway slabs are those slabs with an aspect ratio in plan of 2.
The output of the program for the slab in the example is shown in the following pages. 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. 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. All available load test results indicated that the flat plate or flat slab was a most efficient design with an adequate safety factor. Structural redesign two way slab drop panels my redesign of fordham place will comprise of a 9 flat slab with 5. Reinforced concrete design 1 design of slab examples. The design bending moment of twoway restrained slab can be calculated as follows. Define the term slab, one way slab, two way slab, shrinkage and temperature reinforcement, main reinforcement. Therefore, primary reinforcement is presented in both directions for resisting the loads. The explicit transverse torsional member method is found to give good results for drifts and slabbeam actions, and is recommended for analysis and design of twoway slab systems under combined. Slab is a common term used to describe the structural elements such as floors and roofs where the thickness of the element is very small compared to the length and. Bending will take place in the two directions in a dishlike form. Please enter the practically physible spacing for main steel of two way slab based on summary.
Step 2 design forces draw panel of slab and indicate maximum design moments, shears and in plane loads, if any, per unit width of slab. Design procedure steps for one way slab slab design steps. 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. Materials used for this redesign is normal weight concrete with compressive strength of 4ksi and steel rebar with a yield stress of 60 ksi. Twoway concrete floor slab with beams design and detailing. Designing a composite slab, we encounter semiempirical formulas at this step. Slab moments calculated by various slab analysis methods are compared with each other for idealized flatplate and twoway slabonbeam structures. 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. Analysis and design of slabs two way civil engineers pk. Design of reinforced concrete structures ii twoway slabs 1 1.
Two way slab analysis and design 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. Pdf influence of longitudinal reinforcement strength on oneway. In two way slab, the ratio of longer span l to shorter span b is less than 2. Distribute moments transverse at critical sections to column and middlestrip and if. Distinction of two systems from one way systems is given by aci 31814 r8. Design of reinforced concrete structures ii twoway slabs. Slabs are usually used in floor and roof construction. Design the slab system shown in figure 1 for an intermediate. In case of one ways slabs, the aci approximate analysis is applicable to one way slab system where a one way slab is continuous with a one way slab. Allowable stress design or working stress design wsd 2.
These are the direct design method presented in chap. Twoway concrete slab on beams floor analysis and design. The total load of two way slab loaded with uniformly distributed load and supported on all the four edges is assumed to be transmitted to the supporting walls or edge beams in the manner as shown in fig. Here two examples for design of two way slab using the direct design method. 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. Design of slab examples and tutorials by sharifah maszura syed mohsin. Design of reinforced concrete structures ii two way slabs 1 1. This condition occur when the slabs are connected monolithically with support. The basic design procedure of a twoway slab system has five steps. Rectangular beams and oneway slabs page 2 of 9 two methods. Generally, there are two types of slab which are one way and two way slabs.
The orientation of the principle axes of bending modifies all through the slab. Application of lb ratio in first figure slab is supported on two opposite sides only. Twoway slab design panel select boundary condition of slab for upliftment of corners. In the first part of this series, we explain the concept of one way load transfer in concrete slabs and how to determine the minimum slab thickness based on deflection criteria. Design of a two way rcc slab structural engineering. If slab is supported on all four sides and r shorter side longer side way slab. A simplified method for designing rc slabs under concentrated. Accurately determining the moments on a twoway slab is typically accomplished by finite element computer analysis. One way and twoway slabs one way slabs transfer the imposed loads in one direction only. Load transfer in a one way slab, b two way slab nilson fig. Application of the yield line theory for more complex situations 8. The design procedure for a uniformly loaded oneway reinforced slab can be divided in the following steps. The ratio lb which is less than 2 is known as two way slab. The basic design procedure of a two way 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 twoway slab. The slab is assumed to be divided into two triangles and two trapeziums by lines, ap. Design according to ec4 the reassuring check of composite action between profiled steel sheeting and concrete has a crucial importance. The program covers wide range of twoway slab systems and can be used for more complex slab layouts. The effect of fixing the corners of the slab against lifting 5.
Direct design method of flat plates per aci 31802 twoway slabs are inherently difficult to analyze by conventional methods of statics because of the twoway bending occurring. Oneway concrete slab design part 1 concept explained. One way slab is supported by two parallel beams or walls. The pca computer program pcaslab can be used to expedite the design of different slab systems.
The following example illustrates the design methods presented in the pca book simplified design reinforced concrete buildings of moderate size and height third edition. Pdf analysis of slabs spanning in two directions under. Chapter 3 design of rectangular beams and oneway slabs 12. Twoway slabs have two way bending unlike oneway slab. 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. The slab has to carry a distributed permanent action of 1. 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. Analysis of two way ribbed and waffle slabs with hidden beams.
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