The value of 23 is appropriate for twoway spanning slab if it is continuous over one. These conditions are set out in last section dealing with one way ribbed slabs. 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. Waffle slab construction consists of rows of concrete joists at right. Chapter 3 design of rectangular beams and oneway slabs 12 h a 12 strip in a simply supported one way sl ab. Slabs are primarily categorized as either one way or two ways. Accordingly, main reinforcement is required in the two directions. Reinforced concrete ribbed slabs with widebeam lajes. These are the direct design method presented in chap. Effective depth d span ldbasic x modification factor for obtaining modification factor, the percentage of steel for slab can be assumed from 0.
Analysis of accidental loads on garage floors scielo. 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. In one way slab main tensile reinforcement is placed parallel to shorter side which will be the main steel. The ratio lb which is less than 2 is known 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. Slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs, bridges, and other types of structures. According to adoss, the interior spans due not meet the code requirements to neglect deflection. 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.
A study on a twoway posttensioned concrete waffle slab. Posttensioned twoway slab pennsylvania state university. 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. The slab may be supported by walls, by reinforced concrete beams usually cast monolithically with the slab, by s. Reference 5 focused on analysis of twoway ribbed slabs with. Cross sectional constant defines torsional properties c x.
In two way slabs, load will be carried in both the directions. Design of reinforced concrete structures ii two way slabs 1 1. Twoway joist concrete slab floor waffle slab system. Chapter 3 design of rectangular beams and oneway slabs 12. In twoway slabs shorter direction strip carry greater %age of load. Twoway slabs have two way bending unlike oneway slab. The twoway slab shown in figure below has been assumed to have a thickness of 7 in. Two way slabs are normally supported from four sides. 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 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.
Aug 15, 2016 download code ribbed slab design spreadsheet. Brendon burley structural option posttensioned twoway slab figure 23 details of the twoway slab. 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. Twoway joist waffle slab design approach and methodology. The one way waffle slab system contains a hollow slab. The equations for the analysis have been obtained from the reinforced concrete designers handbook by reynolds and steedman. Twoway flat plate concrete floor system design structurepoint. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types. Brendon burley structural option posttensioned two way slab figure 23 details of the two way slab. 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 simple. Design of slabtwo way excel sheet online civilforum. The results of this analysis are compared with the results of the finite element method by sap program. Ribbed slabs one way and two way waffle and how the blocks are placed. Use the aci 318 direct design method to design an interior bay of a flat plate slab system of multi bay building. The program covers wide range of twoway slab systems and can be used for more complex slab layouts. Analysis of two way ribbed and waffle slabs with hidden.
Chapter 3 design of rectangular beams and oneway slabs. One way slab is the slab having ratio of longer span to shorter span equal to or more than 2. The basic design procedure of a two way slab system has five steps. Oneway and twoway slabs university of asia pacific. Nevertheless, the code allows merging of the flexural steel with. 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.
The one way slab is deflected in one way direction and primary reinforcement is placed in one direction whereas. 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 minimum thickness of slab is specified by aci 31811, section 9. Difference between one way slab and two way slab system. Two way slab design to bs 8110 civil engineering community. Pdf there would be a variety of slab systems which can be used to reduce the slab.
In two way slab, the ratio of longer span l to shorter span b is less than 2. Civilax is the knowledge base covering all disciplines in civil engineering. 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. These conditions are set out in last section dealing with oneway ribbed slabs. Early codes distinguished between fourway reinforcement and twoway reinforcement systems. Two way shear is critical on a rectangular section located at d2 away from the face of the drop panel. Twoway slabs page 6 of 14 the pca computer program pcaslab can be used to expedite the design of different slab systems. Lrfd manual of steel construction 3rd edition 2001. 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. Prior to joining the pca, he was an associate partner with skidmore, owings. Different definitions of span length for oneway slabs, flat plates, beams and two.
Deep ribs, the concrete and steel quantities are relative low expensive formwork expected. Minimum thickness of two way slab as per aci 31811 for. Comparison of one way and two way slab behavior economic choices one way slab on beams suitable span 3 to 6m with ll 35knm2. Unlike bs 8110 there is no specific guidance given in eurocode 2 on how to determine the bending moments for a twoway slab. Two way slab design by direct design method as per aci 31811. Mathematical structural analysis of one way ribbed slabs was introduced in this paper. Generally, there are two types of slab which are one way and two way slabs. Hence, a study combining the effects of shrinkage restraint and loading history on the. If, it is below 2 then it is described as two way slab. This is attributed to the considerable reduction in dead load as compared to other floor systems. Two way edge supported solid slab d two way ribbed slabs.
Jul 02, 20 32 case study case 3 two way hollow block slabs 33. Reinforced concrete, 2014, 9th edition, aci 31811 code edition, by jack c. Design of concrete structures 14th edition, 2009, by arthur h. Pdf historical perspective on the evolution of twoway slab design. The major projects handled before joining zamil includes. Flexural strength and behaviour of sfrscc ribbed slab under four. 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. Several residential and office buildings which contain rooms have two way slab. Determine moments at critical sections in each direction, normally the negative moments at supports and positive moment near midspan. In this article, the author presents a parallel approach to the traditional teaching method of two way ribbed slabs. The load on the slab is carried by the short span in one direction. Ribbed floors consisting of equally spaced ribs are usually supported directly by columns. Deflection of two way slab could be calculated by using available methods to make sure that the deflection will not. Pdf reinforced concrete twoway slabs have evolved in the past century.
In this article, the author presents a parallel approach to the traditional teaching method of twoway ribbed slabs. Slab shear strength twoway shear check the adequacy of slab thickness for punching shear twoway shear at an interior column figure 4. Analysis and design of slabs two way civil engineers pk. Pdf transition from oneway to twoway shear in slabs. Design of reinforced concrete structures ii two way slabs 8 c. Difference between one way slab and two way slab slab.
The one way shear capacity for the ribbed slab portions shown is permitted to be increased by 10%. 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. Materials used for this redesign is normal weight concrete with compressive strength of 4ksi and steel rebar with a yield stress of 60 ksi. Design of reinforced concrete structures ii twoway slabs 1 1. Design of reinforced concrete structures ii twoway slabs. 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. 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.
However main reinforcement bar and distribution bar in transverse direction. Bending will take place in the two directions in a dishlike form. There were also ribbed slabs, which is a type of hollow slab. Distribute moments transverse at critical sections to column and middlestrip and if. Guide to design of reinforced twoway slab systems american.
The dimensions of an interior bay are shown in figure 1. Structural redesign two way slab drop panels my redesign of fordham place will comprise of a 9 flat slab with 5. 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. 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. Mathcad program and show its impact on teaching the analysis and design of twoway ribbed slabs.
However, coefficients may be obtained from table 8 taken from the manual for the design of building structures to eurocode 29 to determine bending. Check the applicable joist dimensional limitations as follows. The concept of waffle slab can be described in a relatively easy way. Cost optimization of a composite floor system, oneway waffle slab. 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. Moments for design may be taken from table 3 for slabs simply supported on four sides. Reference 5 focused on analysis of two way ribbed slabs with. Load transfer in a oneway slab, b twoway slab nilson fig. The ratio of the total costs was found to be within the range 1.
The program covers wide range of two way slab systems and can be used for more complex slab layouts. Slab resting on walls or sufficiently deep and rigid beams on all sides. 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. Lylx 2 one way slab one way slab longer spanshorter span 2.
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. Slabs are usually used in floor and roof construction. Analysis of two way ribbed and waffle slabs with hidden beams. The total requirement for stirrup intensity combining shear and torsion equals2. Two way slabs have two way bending unlike one way slab. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. 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. 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.
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. They are either oneway spanning systems known as ribbed slab or a twoway ribbed system known as a waffle slab. The general provisions for construction and design procedure are given in cop 20. 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. Pdf behaviour and strength of one way reinforced concrete. One way slab is supported by two parallel beams or walls. Ifon,all adjacentspanswith identical crosssection are merged into one span.
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 basic design procedure of a twoway slab system has five steps. Twoway slabs concrete structures eurocode eurocode standards. Twoway slabs, design of twoway slabs, sp183 engineering. Interior left, exterior right deflection analysis the final consideration in the design of the two way slabs is deflection. Two way slabs page 6 of 14 the pca computer program pcaslab can be used to expedite the design of different slab systems. The assessment of the bending moment can be carried out using any suitable method from section 5 of the code. Slabs are generally designed on the assumption that they consists of a number of beams of breadth one meter. Minimum thickness for two way slab construction designed as per methods provided by aci 31811 code namely, direct design method and equivalent frame method. Ribbed slab is a structure that consist of equally spaced ribs spanning in one way and. Oneway concrete slab design part 3 minimum spacing, shrinkage reinforcement, crack control duration.
Twoway concrete slab with beams spanning between supports. The slab may be supported by walls, by reinforced concret. In two way slabs shorter direction strip carry greater %age of load. 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. Waffle slab, twoway slab, rc slab, ansys, punching shear. Comparison of twoway slab analysis and design methods. Bending moments coefficiens have been taking from the bs code. The existing floor system, a twoway reinforced concrete flat plate. Interior left, exterior right deflection analysis the final consideration in the design of the twoway slabs is deflection. Teaching two way ribbed slab analysis and design using the mathcad program mohammed s. Load transfer in a one way slab, b two way slab nilson fig. The moments in beams, slab column strip and slab middle strip will be determined. This spreadsheet performs an analysis and design of two way spanning reinforced concrete slab. Twoway flat plate concrete floor system analysis and design.
Teaching twoway ribbed slab analysis and design using the mathcad program mohammed s. Rectangular beams and oneway slabs page 3 of 9 design of rectangular beams and oneway slabs continued a. Section aa in the figure shows the beam cross section. Most aci standards and committee reports are gathered together in the annually revised aci manual of. Teaching twoway ribbed slab analysis and design using the. The following example illustrates the example building. The oneway slab is deflected in one way direction and primary reinforcement is placed in one direction whereas. Jul 02, 2015 one way concrete slab design part 3 minimum spacing, shrinkage reinforcement, crack control duration. Neither this manual nor any part of it may be reproduced, edited, or altered by any means. 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.