Pdf optimum design of reinforced concrete waffle slabs. Longspan floor systems are also included in the discussion. This new system they invented is called the holedeck. Its typically used when stiffness is important or if there are abnormally heavy loads. Aug 20, 2016 design of waffle slab by safe according to b. A waffle slab or twoway joist slab is a concrete slab made of reinforced concrete with concrete ribs running in two directions on its underside. Cost optimization of a composite floor system, oneway waffle slab. Twoway joist concrete slab floor waffle slab system analysis and design. The deeper the beams the more stiffness the system has.
International journal of pure and applied mathematics. The construction of waffle slabs can be done by three ways as follows. Design of waffle slab without beams by direct design method 32 32 32 c 1 c 2 c 3 c 4 2 c 5 c 6 c 7 c 8 32 s ss 22 3 7 c 9 c 10 c 11 c 12 32 8 11 b 1210 bb c c 14 c 15 c 16 16. Reference 5 focused on analysis of twoway ribbed slabs with. Typical waffle slab for parking structure,with columns on a 33. Waffle slab this study has proposed two types of production for precast waffle slab, namely the semiprecast waffle slab and fullyprecast waffle slab.
A waffle slab foundation, also termed as ribbed slab foundation, is a structure that is plain at the top and has a gridlike system called the ribs at the bottom. The top of ribbed slab is normally thin and the bottom grid lines are generally ribs which are laid perpendicular to each other with equal depth. This waffled feature in slabs will help to take up heavy loads. Waffle slab foundation features and construction details. Actually the introduction of support hoists made waffle. The thickness of a floor slab must be determined early in design because the weight of the slab is an important part of the dead load of the structure. The ribs are categorized as ribbed slab and waffle slab. You can model an equivalent slab simple slab with same weight as that of waffle slab. Waffle pods are used in residential concrete slabs. Jan 28, 2018 a waffle slab gives a substance significantly more structural stability without using a lot of additional material. Oneway simply supported slab analysis and design of the slab similar to design of simply supported beam as indicate in the previous chapter. This paper deals with the problem of optimum design of reinforced concrete twoway ribbed waffle slabs using genetic algorithms.
Twoway joist concrete slab floor waffle slab system analysis and design design the concrete floor slab system shown below for an intermediate floor with partition weight of 50 psf, and unfactored live load of 100 psf. Waffle slab requires only 70% of concrete and 80 % of steel from the concrete and steel used for stiffened raft. The minimum thickness can be determined by many factors. Design of twoway floor slab system comparison of oneway and twoway slab behavior oneway slabs carry load. The more stiffness the slab has, the more it can resist ground movement. Waffle slab or ribbed slab construction procedure and. Since each floor of a hightech plant has different requirements on loading capacity, such capacity shall be designed according to the layout of the facilities on each floor. Ribbed and waffle slabs types, advantages, disadvantages. Waffle slabs provide stiffer and lighter slabs than an equivalent flat slab. The name waffle comes from the grid pattern created by the reinforcing ribs.
Waffle slab purpose, uses, advantages and disadvantages. Pdf this paper deals with the problem of optimum design of reinforced concrete twoway ribbed waffle slabs using genetic algorithms. Waffle slabs are preferred for spans greater than 40 feet 12 m, as they are much stronger than flat slabs, flat slabs with drop panels, twoway slabs, oneway slabs, and. Dynamic features of precast waffle slabs in cleanroom. A waffle slab gives a substance significantly more structural stability without using a lot of additional material. This paper presents an historical and analytical evaluation of the ribbed floor slab systems developed by. Example on structural design of waffle slab structville. As a result, waffle concrete slabs have become an effective alternative that meets these requirements, also to optimize the use of construction materials, working. The aim of the project is to learn more about structures behaviour what will help to find new design methods, both computer aided and ready solutions in form of tables and diagrams. They can be insulated, both underneath and on the edges.
Design the concrete floor slab system shown below for an. It uses 30% less concrete and 20% less steel than a raft slab. Flat slab analysis and design free version download for pc. C 5 is the slope correction coefficient co is the consolidation correction coefficient as an example. Ribbed slabs are made up of wide band beams running between columns with narrow ribs spanning the. For 1m slab width, moment, shear force, oneway continuous slab for continuous slab, moment and shear force can be obtained from table 3. In this paper, the optimum design of reinforced concrete waffle slabs is sought using the simple genetic algorithm.
Oneway and twoway slabs university of asia pacific. Waffle slabs are preferred for spans greater than 40 feet 12 m, as they are much stronger than flat slabs, flat slabs. The analysis and design follow the equivalent frame analysis method of the aci code, which considers a onebay wide strip of the floor system as a continuous frame. A waffle slab is a type of building material that has twodirectional reinforcement on the outside of the material, giving it the shape of the pockets on a waffle this type of reinforcement is common on concrete, wood and metal construction. Note that the polystyrene is not structural, it is simply a void former. Ufc 332006a concrete floor slabs on grade subjected to. Optimum design of reinforced concrete waffle slabs integrated. Waffle slab or ribbed slab construction procedure and advantages. Waffle slabs can be described as the equivalent of 2way solid slabs especially when the spans are large, and ribbed system is to be adopted. The lateral loads are independently resisted by shear walls. Due to the high formwork cost and degraded fire rating, this type of construction generally is not recommended.
They are either oneway spanning systems known as ribbed slab or a twoway ribbed system known as a waffle slab. A waffle raft uses polystyrene void formers or waffle pods to form up the edge beams and internal beams and give the slab the required stiffness, without using excessive amounts of concrete. In australia, waffle slabs are designed to comply with as2870 the. In ribbed slab, there is oneway spanning and in a waffle slab, there is twoway ribbed system. Concrete slab floors come in many forms and can be used to provide great thermal comfort and lifestyle advantages.
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. Pdf analysis of two way ribbed and waffle slabs with. In realty, precast slab floor would have a better vibration performance than the model predicts, since it is partially restrained. Design of twoway floor slab system comparison of oneway and. The speed of construction for such slab is faster compared to conventional slab.
Iconic landmarks using grid slabs chattrapati shivaji terminal, india it is recognized for its innovative column design which also consists waffle design. Reinforced concrete design 1 design of slab examples and. The design of waffle slabs is the same as that of ribbed slabs, with the difference being that waffle slabs have ribs spanning in both directions, and the coefficients used for analysing the slab is similar to those used for twoway restrained slab. First floor slab made by date dead load self weight of hollow pot slab knm2 superimposed dead load screed, plaster and finishes, 1.
Waffle slab or ribbed slab is a structural component which is plain on its top and contains grid like system on its bottom surface. General considerations the main components of castinplace concrete floor systems are concrete, reinforcement mild andor posttensioned, and formwork. The floor slab design procedure presented the maximum allowable stationary live load is lim herein is based on limiting the critical tensile stresses ited by both the positive bending moment stress produced within the slab by the vehicle loading, as under the load and the negative bending moment. The cost of the concrete, including placing and finishing, usually accounts for about 30% to 35% of the overall cost of the floor sys.
The drop panel depth for twoway joist waffle slab is set equal to the rib depth. Waffle slab analysis and design is similar to the procedure used with flat plates except that special considerations need. It is usually used where large spans are required e. Slabs can be onground, suspended, or a mix of both.
Various approaches available for the analysis of waffle slab from which few are as listed below. This form of construction is not very common because of the formwork costs and the low fire rating. For that purpose, calculate the weight of a waffle by considering centreline between two ribs calculate the weight of that section for a unit length. Reinforced concrete design 1 design of slab examples. Design of waffle slab without beams by direct design method. Twoway joist waffle slab design approach and methodology. Then equate that weight to weight of a equivalent slab same plan dimensions and calculate the required. Waffle slab construction consists of rows of concrete joists at right angles to each other with solid heads at the column needed for shear requirements or with solid. Design example a church building has a square grid of 7. This makes a waffle slab perfect for large flat areas like foundations or floors. Waffle slabs achieve their strength by varying the height of the slab above ground.
Feasibility of structural design of members has been ensured under the provision of is. Because there are joists in both directions, this floor system is the strongest and will have the least deflection. The ratio of the total costs was found to be within the range 1. A waffle slab is a type of slab with holes underneath, giving an appearance of waffles. Metropol parasol, italy it is the worlds largest wooden structure which is made up of waffle system. Twoway joist waffle slab design approach and methodology twoway joist slab often called twoway ribbed slab or waffle slab is an economical floor system when the spans are long andor loads are high. Mar 19, 2017 a waffle slab is a type of slab with holes underneath, giving an appearance of waffles. In this paper, the optimum design of reinforced concrete waffle slabs is so ught using the simple genetic algorithm. The objective of this work was to analyze the adequacy of a design method widely used in the modeling of. The design bending moments are zero at discontinuous ends, negative at continuous ends and positive at midspans. Design of waffle slab without beams by direct design method 32 32 32 c 1 c 2 c 3 c 4 2 c. For this slab, panel a has two discontinuous exterior edges and two continuous interior edges, panel b has one discontinuous and three continuous edges, while the interior panel c has all edges continuous. The waffle slab has been considered as monolithically connected to band beams.
Slabs that have span greater than 16m can make use of a waffle slab design. Twoway joist concrete slab floor waffle slab system. The higher the slab above ground the deeper the beams. Design of slab examples and tutorials by sharifah maszura syed mohsin example 1. The design procedure set forth in that publication had at that time been in use by the author for about 15 years. Flat slab analysis and design designs beamless concrete slab floors flat slab or waffle slab in accordance with aci 318. The ribs are formed due to the pouring of concrete over a set of plastic waffles arranged in series on the ground. After this publication, it was subsequently adopted by the uniform building. Ribbed floors consisting of equally spaced ribs are usually supported directly by columns. The slab has to carry a distributed permanent action of 1. Ribbed or waffle slab is a slab system which consists of series of parallel reinforced concrete t beams framing into reinforced concrete girders. Mar 01, 2018 slabs that have span greater than 16m can make use of a waffle slab design. Pdf twoway joist concrete slab floor waffle slab system. Composite floor system oneway waffle slab concrete slab formwork.
The top of a waffle slab is generally smooth, like a traditional building surface, but the underside has a shape reminiscent of a waffle. The historical discussion includes the evolution of the floor slab from a nonstructural element to an inspired structural. Simply supported one way slab a rectangular reinforced concrete slab is simplysupported on two masonry walls 250 mm thick and 3. They provide a very good form of construction where slab vibration is an issue, such as laboratories and hospitals. Contact gilcon engineering for waffle slab construction in sydney. Shear strength of beamless slabs usually a controlling factor.
International journal of pure and applied mathematics volume. Optimum design of reinforced concrete waffle slabs alaa c. Abstract in this paper, the optimum design of some floor systems, including composite. The slab is the flange of the beam and the extended part is the web. Numerical and experimental study of a real scale waffle slab. Waffle slab is good against shrinkage and it is lower than stiffened rafts and footing slabs.
1197 851 893 1427 900 134 1130 1030 792 1329 346 765 565 910 259 816 1016 637 498 1427 84 1283 1354 931 871 241 210 623 964 305 726 688 985 472 382 578 565 131 608 1462 434 144 1018 88 1244 868 7