Reinforced concrete flat slabs are extensively used in buildings and parking garages. C two way slabs improves considerably the structural behaviour of such slabs leading. Reinforced concrete ribbed slabs with widebeam scielo. Current study, such as lau and clark, assesses the performance of one and twoway ribbed slabs with widebeams by analyzing the structural behavior of the.
Unless otherwise noted, all referenced table, figure, and. A st as distribution bars in longer direction of slab. Check slab shear and flexural strength at edge column due to direct shear and unbalanced moment transfer. How to detail reinforcements of twoway slabs quora. 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. Now in one way slab as one side is bigger than the other side most of the load is carried by that side only so providing main reinforcement corresponding to that load carrying. Figure 1 twoway slab with beams spanning between all supports. Assume partitions cannot be damaged by deflections.
The ratio of the total costs was found to be within the range 1. Reinforcement detailing of reinforced concrete slabs. Generally, there are two types of slab which are one way and two way slabs. Twoway slabs have two way bending unlike oneway slab. Slab supported directly by columns are called flat slab.
The dominating failure mode for two way slab, flexural, or punching shear is based on the slab steel reinforcement ratio. These slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs or other types of structures. Bridge approach slab analysis and design incorporating elastic soil support presented by. Accordingly, main reinforcement is required in the two directions. In twoway slabs shorter direction strip carry greater %age of load. Steel reinforcement strong in tension, and strong in compression as long as the concrete can stop it bowing myth busting. Unlike two way systems, where it is possible to design a floor with no bottom rebar, the code. Chapter 3 design of rectangular beams and oneway slabs 12. Steelreinforced slabs, typically between 100 and 500 mm thick, are most often used to construct floors and ceilings, while thinner mud slabs may be used for exterior paving see below. Rectangular beams and oneway slabs page 5 of 9 maximum permissible steel ratio, max an overreinforced beam will fail in a brittle manner while an underreinforced beam will.
Thus, the maximum reinforcement ratio corresponds to a net tensile stain in the reinforcement. Bending will take place in the two directions in a dishlike form. Analysis and design of slabs two way civil engineers pk. Nonprestressed bonded reinforcement in posttensioned. In two way slab, the ratio of longer span l to shorter span b is less than 2. Plain slabs similar in shape to ground slabs take the load directly from the floor and transmit it to the beams. Use the equivalent frame method efm and compare the results with spslab model results. Plan view of floor system assume partitions will not be damaged by deflections. 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 nominal shear stress acting on the slab is then determined from bd v u v t 8. Slab shear strength twoway shear check the adequacy of slab thickness for punching shear twoway shear at an interior column figure 4. In many cases the slabs are of such proportions and are supported in such way that two way action. A concrete slab is a common structural element of modern buildings, consisting of a flat, horizontal surface made of cast concrete. Reinforcement detailing of a slab is done based on its support conditions. Slab resting on walls or sufficiently deep and rigid beams on all sides. Tn342 design example 2way mondada 093090 adapt corporation. Experimental behavior of a masonry wall supported on a rc. Mathematical structural analysis of one way ribbed slabs was introduced in this paper. Difference between one way slab and two way slab simple. In sap program, the model has been divided to frame elements to represent ribs and beams and shell elements to represent the slab and solid part.
The dominating failure mode for twoway slab, flexural, or punching shear is based on the slab steel reinforcement ratio. In two way slabs, load will be carried in both the directions. One way slab are slab in which one side is very large compared to the other one. This indirect, somewhat complex, method for determining the required amount of bonded reinforcement does not offer a direct comparison to the minimum reinforcement requirements for unbonded slabs specified in aci 31811, 3. Two way slabs are surface members acting in a both directions. The following example illustrates the example building. In two way slabs shorter direction strip carry greater %age of load. Postpunching behavior of reinforced concrete slabs infoscience. Contains all design checks required by the american concrete institute code and all the conditions that must be met during the design process. Design of reinforced concrete structures ii two way slabs 1 1. One way slab oneway slabs are those slabs with an aspect ratio in plan of 2. Unlike twoway systems, where it is possible to design a floor with no bottom rebar, the code. Ce 433, fall 2006 slab design example 1 6 design a one way slab for an exterior bay of a multistory office building using the information specified below. The concrete strength was fc250 kgcm the details and steel reinforcement in the slab were designed using conventional procedures, such a s.
Twoway flat plate concrete floor system analysis and design. Chapter 3 design of rectangular beams and oneway slabs. If the length to breadth ratio of the room is less than 2, the slab is designed as a twoway reinforced slab. Twoway concrete slab with beams spanning between supports. Maximam reinforcement ratio reinforcement ratio is the ratio of reinforcement area to gross concrete area based on total depth of 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.
Two way slabs are normally supported from four sides. Testing on two way posttensioned slabs with a banded tendon distribution2 contained neither the nonprestressed reinforcement shown in fig. Oneway and twoway slabs university of asia pacific. The oneway slab is deflected in one way direction and primary reinforcement is placed in one direction whereas. Design of reinforced concrete structures ii twoway slabs. Flexural analysis of oneway concrete slabs r einforced with t. Oneway solid slabs are designed as rectangular sections subjected to shear and moment. In the design of twoway reinforced concrete slabs, e. Experimental behavior of a masonry wall supported on a rc two. In many domestic and industrial buildings, a thick concrete slab supported on. They may be supported on two opposite sides only fig. At the end of this lesson, the student should be able to. Two way concrete slab having 100mm thickness and dimension as shown in figure below, supported deal load of 6knm2 and live load of 3knm2 wu 1. Postpunching strength predicted by simplified method and.
C twoway slabs improves considerably the structural behaviour of such slabs leading. Analysis of two way ribbed and waffle slabs with hidden beams. Concrete slabs come in a variety of forms depending on their locations. This video describes how the the reinforcement is placed at the site.
Unless you have an engineering drawing that says otherwise make sure the reinforcement is in the right position by insisting on bar chairs. Oneway and twoway slabs oneway slabs transfer the imposed loads in one direction only. Its scope includes proposing the inclusion of two new equations. Internal force distribution in rc slabs subjected to. The results show that the existence of corner reinforcement in r. Aug 23, 2017 this video describes how the the reinforcement is placed at the site. In this example, the latter option will be used to achieve better understanding for the design of two way joist slab often called two way ribbed slab or waffle slab.
Lots of concretors will tell you we put steel the reinforcement close to the bottom of a driveway slab because when you load a slab, the bottom is in tension,which needs the steel, and the top compresses. Two way slabs page 1 of 14 the following example illustrates the design methods presented in the article timesaving design aids for reinforced concrete, part 2. The shear design of reinforced concrete rc slabs under. Reference 5 focused on analysis of twoway ribbed slabs with. Proceed with the same method for each type of bar listed in the bar bending. The minimum area of this reinforcement in each way is a maximum from values a s,x and a s,y in midspan pink color. Apr 4, 2012 this is a typical reinforced concrete cantilever slab reinforcement detail with a constant slab width. Pdf fiberreinforced polymer strengthening of twoway slabs. Difference between one way slab and two way slab system.
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. The results of this analysis are compared with the results of the finite element method by sap program. Slabs beam reinforcement detailing linkedin slideshare. For some slabs reinforcement bars are required in two layers within the slab. Cantilever slab supported on a reinforced concrete beam with top and bottom reinforcement as well as middle torsion reinforcement. Reinforced concrete rc twoway slabs without shear reinforcement are commonly used in many struc tural systems. Fanella, which appeared in the october 2001 edition of structural engineer magazine.
Define the term slab, one way slab, two way slab, shrinkage and temperature reinforcement, main reinforcement. 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. In case of oneway slab, the main reinforcement of the slab, span along the width of the room while the distribution bars, laid at right angles to the main reinforcement, lie parallel to the length of the room. Portion of total unbalanced moment transferred by flexure. Slab may be supported on walls or beams or columns. 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. The ratio of length to width of one slab should less than 2 otherwise one way action is obtained, even though supports are provided on all sides. Reference 5 focused on analysis of two way ribbed slabs with. One way slab is supported by two parallel beams or walls. One way slab reinforcement details online civilforum. The ratio lb which is less than 2 is known as two way slab. The reinforcement ratios were chosen to serve the purpose of demarcating. Civilax is the knowledge base covering all disciplines in civil engineering. 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.
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. Slab supported on two sides and bending takes place predominantly in one direction only is called one way slab. Types of one way slab one way slab may be solid hollow ribbed 6. Design of reinforced concrete structures ii twoway slabs 1 1. Generally if one side is more than double of the other one, the slab will be one way. If an equilibrium method is applied, the reinforcement bars in the entire slab. Ce 433, summer 20 slab design example 1 5 design a one. It is independent of the loading, service stresses, and span length. Twoway joist concrete slab floor waffle slab system. One way and two way slabs one way slabs transfer the imposed loads in one direction only. Design of a two way slabs for punching shear resistance. Preliminary design of slab thickness thickness design depends on boundary conditions supports. These tests demonstrated that adequate, codeconformant behavior in two way posttensioned slabs fig. Check the applicable joist dimensional limitations as follows.
Shrinkage and temperature reinforcement in twoway post. One way slab vs two way slab civil engineering community. The best place to put steel mesh reinforcement in a concrete slab, cast on the ground, is about rd of the depth from the top. Bar bending schedule of two way slab bbs of two way slab engineering tactics duration. Reinforced concrete constant width cantilever slab detail. If the length to breadth ratio of the room is less than 2, the slab is designed as a two way reinforced slab. Two way slab is a slab in which the ratio of longer side to the shorter side is less than or equal to two. Two way slabs have two way bending unlike one way slab. In the table 1 sb is the tested slab identification, d is the effective depth of the sections. Two way slab design by direct design method as per aci 31811. Slab reinforcement in detail two way slab reinforcement.
Master of science and hereby certify that, in their opinion, it is worthy of acceptance. Oneway slab design spreadsheet civil engineering community. Shear in reinforced concrete slabsexperimental investigations in. The details and steel reinforcement in the slab were designed using conventional procedures, such a s. The one way slab is deflected in one way direction and primary reinforcement is placed in one direction whereas. Check slab reinforcement at exterior column for moment transfer between slab and column. In case of one way slab, the main reinforcement of the slab, span along the width of the room while the distribution bars, laid at right angles to the main reinforcement, lie parallel to the length of the room. How to design a twoway slab free download as powerpoint presentation. Two way slabs are such slabs in which the loads are shared by both the shorter and longer direction of the slab.
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