The results of this analysis are compared with the results of the finite element method by sap program. However main reinforcement bar and distribution bar in transverse direction. The slab may be supported by walls, by reinforced concret. The minimum thickness of slab is specified by aci 31811, section 9. Reinforced concrete ribbed slabs with widebeam lajes.
Ca vent pipe between beams pilebeam foundation prepared subbase vent riser pipe to roof beton stop cupolex form pontex internal rib beam form cupolex concrete slab applications there may be many reasons for suspending a floor slab that may include. Prior to joining the pca, he was an associate partner with skidmore, owings. Ribbed slab design spreadsheet civil engineering community. Posttensioned twoway slab pennsylvania state university. Distribute moments transverse at critical sections to column and middlestrip and if. Design of slabtwo way excel sheet online civilforum. Reference 5 focused on analysis of two way ribbed slabs with. Chapter 3 design of rectangular beams and oneway slabs 12 h a 12 strip in a simply supported one way sl ab.
In one way slab main tensile reinforcement is placed parallel to shorter side which will be the main steel. 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 basic design procedure of a twoway slab system has five steps. Comparison of one way and two way slab behavior economic choices flat plate suitable span 20 to 25 ft with ll 60 100 psf advantages low cost formwork exposed flat ceilings fast disadvantages low shear capacity low stiffness notable deflection. Two way slabs have two way bending unlike one way slab. Brendon burley structural option posttensioned twoway slab figure 23 details of the twoway slab. Analysis of two way ribbed and waffle slabs with hidden beams ibrahim mohammad arman international journal of civil and structural engineering volume 4 issue 3 2014 343 four slabs are taken in this study to show the moments distribution in two way ribbed slab with hidden beams systems. Two way slabs page 6 of 14 the pca computer program pcaslab can be used to expedite the design of different slab systems. The basic design procedure of a two way slab system has five steps.
This form of construction is not very common because of the formwork costs and the low fire rating. The waffle slab is capable of providing the largest spans of the conventional concrete floor systems and can be economically used for spans up to 12. Difference between one way slab and two way slab slab. Twoway joist concrete slab floor waffle slab system. The ratio of the total costs was found to be within the range 1. 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. Ifon,all adjacentspanswith identical crosssection are merged into one span. Lrfd manual of steel construction 3rd edition 2001. 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.
Pdf historical perspective on the evolution of twoway slab design. 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. Neither this manual nor any part of it may be reproduced, edited, or altered by any means. Analysis and design of slabs two way civil engineers pk. In this article, the author presents a parallel approach to the traditional teaching method of twoway ribbed slabs. Design of reinforced concrete structures ii two way slabs 1 1. The assessment of the bending moment can be carried out using any suitable method from section 5 of the code. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types. Pdf analysis of two way ribbed and waffle slabs with.
The ratio lb which is less than 2 is known as two way slab. Mathematical structural analysis of one way 763 3 comparison between the results of finite element method and traditional method two bays one way ribbed slab is analyzed by both traditional and finite element methods to determine the induced moments of the rib. Slabs are usually used in floor and roof construction. In two way slabs shorter direction strip carry greater %age of load. Deep ribs, the concrete and steel quantities are relative low expensive formwork expected. These conditions are set out in last section dealing with one way ribbed slabs. Bending moments coefficiens have been taking from the bs code. Pdf behaviour and strength of one way reinforced concrete. Unlike bs 8110 there is no specific guidance given in eurocode 2 on how to determine the bending moments for a twoway slab. Comparison of one way and two way slab behavior economic choices one way slab on beams suitable span 3 to 6m with ll 35knm2. Materials used for this redesign is normal weight concrete with compressive strength of 4ksi and steel rebar with a yield stress of 60 ksi. Two way slab design to bs 8110 civil engineering community. Minimum thickness of two way slab as per aci 31811 for.
Ribbed slabs one way and two way waffle and how the blocks are placed. 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. Slab resting on walls or sufficiently deep and rigid beams on all sides. Waffle slab construction consists of rows of concrete joists at right. Chapter 3 design of rectangular beams and oneway slabs. Section aa in the figure shows the beam cross section. 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. 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. The slab may be supported by walls, by reinforced concrete beams usually cast monolithically with the slab, by s. 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. Most aci standards and committee reports are gathered together in the annually revised aci manual of. Early codes distinguished between fourway reinforcement and twoway reinforcement systems. This spreadsheet performs an analysis and design of two way spanning reinforced concrete slab. Brendon burley structural option posttensioned two way slab figure 23 details of the two way slab.
Deflection of two way slab could be calculated by using available methods to make sure that the deflection will not. Twoway concrete slab with beams spanning between supports. Flexural strength and behaviour of sfrscc ribbed slab under four. These conditions are set out in last section dealing with oneway ribbed slabs. Mathcad program and show its impact on teaching the analysis and design of twoway ribbed slabs. Twoway joist waffle slab design approach and methodology. Ribbed slab is a structure that consist of equally spaced ribs spanning in one way and. Design of reinforced concrete structures ii twoway slabs 1 1. Pdf transition from oneway to twoway shear in slabs. Oneway and twoway slabs university of asia pacific. Teaching twoway ribbed slab analysis and design using the. Interior left, exterior right deflection analysis the final consideration in the design of the two way slabs is deflection.
Oneway concrete slab design part 3 minimum spacing, shrinkage reinforcement, crack control duration. The total requirement for stirrup intensity combining shear and torsion equals2. 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. Load transfer in a oneway slab, b twoway slab nilson fig. Design of reinforced concrete structures ii two way slabs 8 c. The concept of waffle slab can be described in a relatively easy way. Generally, there are two types of slab which are one way and two way slabs. Introduction posttensioned construction has for a long period of time occupied a significant position, especially in the construction of bridges, storage tanks, but also in. However, coefficients may be obtained from table 8 taken from the manual for the design of building structures to eurocode 29 to determine bending. My graduation project with my mate ghassan faris, a two way ribbed slab of clear span of 18 x 25 m was designed by safe 2014, the building is 3storey concrete. Minimum thickness for two way slab construction designed as per methods provided by aci 31811 code namely, direct design method and equivalent frame method.
Teaching twoway ribbed slab analysis and design using the mathcad program mohammed s. The one way waffle slab system contains a hollow slab. Waffle slab, twoway slab, rc slab, ansys, punching shear. The major projects handled before joining zamil includes. Two way slab design by direct design method as per aci 31811. Under the general provisions of the 1995 code, chapter, the twoway joist portion may be combined with a solid column head or with solid wide beam sections on the column centerlines for uniform depth construction.
Load transfer in a one way slab, b two way slab nilson fig. Several residential and office buildings which contain rooms have two way slab. Twoway slabs, design of twoway slabs, sp183 engineering. Use the aci 318 direct design method to design an interior bay of a flat plate slab system of multi bay building. Lylx 2 one way slab one way slab longer spanshorter span 2. The moments in beams, slab column strip and slab middle strip will be determined.
Effective depth d span ldbasic x modification factor for obtaining modification factor, the percentage of steel for slab can be assumed from 0. Cost optimization of a composite floor system, oneway waffle slab. Nevertheless, the code allows merging of the flexural steel with. In twoway slabs shorter direction strip carry greater %age of load. Reference 5 focused on analysis of twoway ribbed slabs with. Traditionally, the term flat slab has represented a solid uniform depth slab with thicker drop panels supported upon mushroom head conical capitals with round columns or various prismatic brackets with square columns. According to adoss, the interior spans due not meet the code requirements to neglect deflection. Slab shear strength twoway shear check the adequacy of slab thickness for punching shear twoway shear at an interior column figure 4. The one way shear capacity for the ribbed slab portions shown is permitted to be increased by 10%. If, it is below 2 then it is described as two way slab. 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. The load on the slab is carried by the short span in one direction. Moments for design may be taken from table 3 for slabs simply supported on four sides.
Pdf reinforced concrete twoway slabs have evolved in the past century. Jul 02, 20 32 case study case 3 two way hollow block slabs 33. Jan, 2020 unlike bs 8110 there is no specific guidance given in eurocode 2 on how to determine the bending moments for a two way slab. Hence, a study combining the effects of shrinkage restraint and loading history on the. Two way slabs are normally supported from four sides. Analysis of two way ribbed and waffle slabs with hidden beams. It will be illustrated that the distribution of moments in two way slabs with hidden beams likes the distribution of moments in slabs without beams as the stiffness of the hidden beams is small. Reinforced concrete, 2014, 9th edition, aci 31811 code edition, by jack c.
This is attributed to the considerable reduction in dead load as compared to other floor systems. The one way slab is deflected in one way direction and primary reinforcement is placed in one direction whereas. 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. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. Square two way spanning slabs tend to be the most economical shape since each supporting beam or wall carries the same proportion of the total load from the slab and this leads to the minimum required slab and beam depth 1,2. Jul 02, 2015 one way concrete slab design part 3 minimum spacing, shrinkage reinforcement, crack control duration.
In this article, the author presents a parallel approach to the traditional teaching method of two way ribbed slabs. One way slab is supported by two parallel beams or walls. Comparison of twoway slab analysis and design methods. In two way slab, the ratio of longer span l to shorter span b is less than 2. Difference between one way slab and two way slab simple. Twoway flat plate concrete floor system analysis and design. Slabs are primarily categorized as either one way or two ways. 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 dimensions of an interior bay are shown in figure 1. Twoway slabs have two way bending unlike oneway slab. Aug 15, 2016 download code ribbed slab design spreadsheet. Difference between one way slab and two way slab system. The value of 23 is appropriate for twoway spanning slab if it is continuous over one. Interior left, exterior right deflection analysis the final consideration in the design of the twoway slabs is deflection.
Current study, such as lau and clark 4, assesses the performance of one and twoway ribbed slabs with widebeams by analyzing the structural. Analysis of accidental loads on garage floors scielo. It will be illustrated that the distribution of moments in twoway slabs with hidden beams likes the distribution of moments in slabs without beams as the stiffness of the hidden beams is small. A study on a twoway posttensioned concrete waffle slab. In two way slabs, load will be carried in both the directions. The general provisions for construction and design procedure are given in cop 20. The equations for the analysis have been obtained from the reinforced concrete designers handbook by reynolds and steedman. Civilax is the knowledge base covering all disciplines in civil engineering. Ribbed floors consisting of equally spaced ribs are usually supported directly by columns. Analysis of two way ribbed and waffle slabs with hidden beams ibrahim mohammad arman international journal of civil and structural engineering volume 4 issue 3 2014 343 four slabs are taken in this study to show the moments distribution in two way ribbed slab. Guide to design of reinforced twoway slab systems american. Different definitions of span length for oneway slabs, flat plates, beams and two. Twoway slabs page 6 of 14 the pca computer program pcaslab can be used to expedite the design of different slab systems. Slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs, bridges, and other types of structures.
The program covers wide range of two way slab systems and can be used for more complex slab layouts. Transition from oneway to twoway shear in slabs under concentrated loads article pdf available in magazine of concrete research 6717 april 2015 with 3,216 reads how we measure reads. Slabs are generally designed on the assumption that they consists of a number of beams of breadth one meter. Design of reinforced concrete structures ii twoway slabs. The following example illustrates the example building. Twoway slabs concrete structures eurocode eurocode standards. Two way shear is critical on a rectangular section located at d2 away from the face of the drop panel. Can be used for larger spans with relatively higher cost and higher deflections one way joist system suitable span 6 to 9m with ll 46knm2. The output of the program for the slab in the example is shown in the following pages.
By combining these two materials, the compressive strength of concrete can increase. Accordingly, main reinforcement is required in the two directions. Twoway flat plate concrete floor system design structurepoint. The twoway slab shown in figure below has been assumed to have a thickness of 7 in. Analysis of two way ribbed and waffle slabs with hidden. There were also ribbed slabs, which is a type of hollow slab. Check the applicable joist dimensional limitations as follows. One way slab is the slab having ratio of longer span to shorter span equal to or more than 2. The oneway slab is deflected in one way direction and primary reinforcement is placed in one direction whereas.
Design of concrete structures 14th edition, 2009, by arthur h. Cross sectional constant defines torsional properties c x. These are the direct design method presented in chap. The program covers wide range of twoway slab systems and can be used for more complex slab layouts.
Chapter 3 design of rectangular beams and oneway slabs 12. Pdf there would be a variety of slab systems which can be used to reduce the slab. Jul 22, 2015 my graduation project with my mate ghassan faris, a two way ribbed slab of clear span of 18 x 25 m was designed by safe 2014, the building is 3storey concrete. Mathematical structural analysis of one way ribbed slabs was introduced in this paper. The existing floor system, a twoway reinforced concrete flat plate. Manual for design and detailing of reinforced concrete to the code.
Teaching two way ribbed slab analysis and design using the mathcad program mohammed s. Structural redesign two way slab drop panels my redesign of fordham place will comprise of a 9 flat slab with 5. This symposium publication consists of 10 papers that give the designer an overview of some of the different analysis and design techniques currently being used. Determine moments at critical sections in each direction, normally the negative moments at supports and positive moment near midspan. Bending will take place in the two directions in a dishlike form. These slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs or other types of structures.