What is the coefficient method of a twoway slab design. Mendoza, it really is not economical to design two types of slabs, unless the requirement is that they are sufficiently different for to be setup as two slabs. In case of two way slabs, the moment coefficient tables are applicable to two way slab system where a two way slab is continuous with a two way slab. Two way reinforced concrete slab design spreadsheet working. The main structural action is one way in such cases, in the direction normal to supports on two opposite edges of a rectangular panel. There should be no reversal of moments at the critical design sections near. Tables for use with coefficient method for two way slab design.
Title reinforced concrete slab design using the empirical method publication no. Bss090119991 abstract this design example illustrates the empirical design method for composite concrete bridge decks specified in article 9. Slabs are usually used in floor and roof construction. Design of slab examples and tutorials by sharifah maszura syed mohsin example 1. Design of reinforced concrete structures ii twoway slabs. Home software slab analysis by coefficient method v2. Two way slab design using the coefficient method free download as pdf file. The coefficient method is a method of designing two way slabs that are supported by edge beams. Bending will take place in the two directions in a dishlike fo. A simplified method for designing rc slabs under concentrated.
Twoway slab design using the coefficient method beam. This situation happen when slab connected by monolithic with the supporter or slab panel connected by monolithic between one and another and moment acting at slab edge. Two way flat plate concrete floor system analysis and design the concrete floor slab system shown below is for an intermediate floor to be designed considering partition weight 20 psf, and unfactored live load 40 psf. In this video deisgn of two way slabs has been covered using is 456. Two way slab design coefficient method method 3 of aci.
Please read the lauses mentioned in the video while solving the problem. The basic difference between the two types of slabs is that. Oneway and twoway slabs university of asia pacific. Twoway slab design coefficient method tables qn85e8pkopn1. Each single slabs are referred to as panels, if the slab is continuous over supports. Two way slab design as per method 3 aci concrete code. Direct design method alias ddm as well as coefficient method are used to design the slabs. Design of concrete structures 14th edition, 2009, by arthur h. The aci coefficient method is declared obsolete because the end results are more conservation more factor of safety.
Oneway and twoway slabs oneway slabs transfer the imposed. Slabs are primarily categorized as either one way or two ways. Lecture series on design of reinforced concrete structures by prof. Mention the parameters governing slab moment coefficients and explain their effects on moment. If the proportion of longer dimension of the slab panel to the shorter dimension is more than or equivalent to 2 then it is defined as one way slab. Direct design method uses coefficients to compute positive and negative slab moments 4. Design of two way slab moment coefficient method bnbc 1993. Slab design reading assignment chapter 9 of text and, chapter of aci31802 introduction aci318 code provides two design procedures for slab systems. Introduction analysis of plates and shells to attain internal actions for designing structural elements is one of the fields that scientists and engineers have been working on for years. Generally, there are two types of slab which are one way and two way slabs. Design the slab, following the provisions of the ack code. Analysis and design of slabs two way civil engineers pk. Bending will take place in the two directions in a dishlike form.
Two way slab design to aci free download and software. Mar 14, 2018 two way slab constrained have more than one panel or in section slab edge can be prevent from lifted. Two way slab by coefficients beam structure bending. Nov 15, 2018 the method is to apply a coefficient to each direction of the span, lets call them msx and msy.
Alternate design method design procedure of twoway slabs using aci. Download our free two way slab design spreadsheet only from samotech. No certain method can be found in the design codes or references for designing two way slabs subjected to concentrated loads. In one way slab load is carried by one direction only that is the shorter one and hence main. Applicability of code design methods to rc slabs on secondary. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types. Various simplified methods are therefore adopted for determining moments, shears and reactions in such slabs. 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. The coefficient method makes use of tables of moment coefficients for a variety of.
Flat plate concrete floor system does not use beams between columns or. However, plastic method can be the best method for designing such cases of two way slabs. Depending on the geometry you will apply a different value to that span length. Two way slab a bending of center strip, b grid model. This spreadsheet is an extremely efficient tool and allows to quickly design two way slabs to aci code. In two way slabs shorter direction strip carry greater %age of load. Simply supported one way slab a rectangular reinforced concrete slab is simplysupported on two masonry walls 250 mm thick and 3. Analysis of two way slabs by coefficient method the determination of exact moments in two way slabs with various support conditions is mathematically formidable and not suited to design practice.
But i think, many structural designers are still using the old method which is coefficient method or method 3 of the aci 1963 building code and which for me i think is still preferable. Design of two way slab by coefficient method behaviour of two way slabs one way slab deform under load into an approximately cylindrical surface. It is designing for moments in a two way slab by using coefficients listed for column strips and mid strips for each direction with different edge conditions. I would guess that you are referring to method 2 and method 3 in the 63 code my personal favorite. Mar 09, 2019 direct design method ddm is the preferable method for designing the conventional two way slab system and other floor system like flat slabs and flat plate slab system. 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. 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 one way slab is deflected in one way direction and primary reinforcement is placed in one direction whereas. Dec 20, 2017 in this video deisgn of two way slabs has been covered using is 456. Two way slab design static equilibrium of two way slabs total moment in both beams full load was transferred eastwest by the planks and then was transferred northsouth by the beams. Aci coefficient method for analysis of twoway slabs. Alternate design method design procedure of twoway slabs. Two way concrete floor slab with beams design and detailing design the slab system shown in figure 1 for an intermediate floor where the story height 12 ft, column cross sectional dimensions 18 in.
Dec 01, 20 9 aci moment coefficient for two way slab 12120 10. 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. 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. Alternate design method design procedure of twoway slabs using aci moment coefficients and approved by bnbc 20 scope and limitations bnbc 6. Design of two way slab by coefficient design of two way. 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. I know there are new methods for designing two way slabs, direct design method or equivalent frame method. Slabs can be designed by direct design method known as ddm and another method for design is coefficient method which is the easier one. Reinforced concrete slab design using the empirical method. If the ratio of longer dimension of the slab panel to the shorter dimension is greater than or equal to 2 then it is designed as one way slab. Given below, the sample spreadsheet for creating the design of two ways slab with the help of coefficient method.
Nonetheless, the coefficient method is not included in the current edition of the aci code. The slab was divided into strips middle and column or edge strip with the diemension as shown in figure below. The most efficient design would be a square with equal lengths. Two way slab design coefficient method tables free download as pdf file. A reinforced concrete slab is built integrally with its supports and consists of two equal spans, each with a clear span of 15 ft. Accordingly, main reinforcement is required in the two directions. How to design for slab reinforcement using aci method if the. Twoway concrete slab with beams spanning between supports.
This method was provided in the american concrete institute aci in 1963 to design twoway slabs carried by steel beams, deep beam, or walls. The basic design procedure of a twoway slab system has five steps. The slab has to carry a distributed permanent action of 1. Reinforced concrete design reinforced concrete design twoway. A slab or panel is said to be two way slab if the ratio of longer span to the shorter span is not greater than 2 two. This method requires various formulas for different conditions of rc slab. Dec, 2017 beam and slab arrangement can be the best example for one way and two way slabs. The method is to apply a coefficient to each direction of the span, lets call them msx and msy. Design of twoway slab by coefficient method the constructor. Direct design method ddm for slab systems with or without beams loaded only.
Reinforced concrete slabs on secondary beams differ from twoway slabs on. Dhang, department of civil engineering, iit kharagpur. Design procedure of twoway slabs using aci moment coefficients. This condition occur when the slabs are connected monolithically with support. Two way slab design by direct design method as per aci 31811.
The design bending moment of twoway restrained slab can be calculated as follows. Two way reinforced concrete slab design spreadsheet working stress design coefficient method. Design of two way slab by usd method and usd method slab case slab dimension short. Two way slabs have two way bending unlike one way slab. Notes author staff bridgesight software sponsor bridgesight software. Reinforced concrete, 2014, 9th edition, aci 31811 code edition, by jack c. Jun 03, 2016 design of two way slab moment coefficient method bnbc 1993. Reinforced concrete design 1 design of slab examples and. For twoway slabs on beams, there are a number of code design methods that can. Beamslab system designation, static moment coefficients, negativetostatic. The service live load is 100 psf, and 4000 psi concrete is specified for use with steel with a yield stress equal to 60,000 psi. Reinforced concrete design reinforced concrete design two way slabs design of two way slab moment coefficient method load transfer from two way slab bar detailing design example slab on ground. Design of reinforced concrete structures ii two way slabs 1 1. This is because it is considered to be too conservative and more precise approaches can be employed.
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