Optimum design of reinforced concrete waffle slabs alaa c. 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. Flat slab analysis, design and detailing pdf civil. Waffle slabs are a reinforced concrete footing and slab system constructed on the ground. The lateral loads are independently resisted by shear walls. There are two common ways to build a slab for a house. A civil engineer must know all the aspects regarding the flat floor system.
For longerribbed slabs, the restraint due to the beams should be taken into. Waffle slabs moulds fg 900 moulds fg 900 moulds are used on the construction of waffle slabs with bidirectional orthogonal ribs, also called fungiform slabs, producing modules with 900 mm distance between the ribs axis. 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. Ribraft floors foundations concrete flooring nz firth. Cip 6 joints in concrete slabs on grade what are joints. Ribraft floors are an innovative method of raft concrete floor construction is quick and efficient to lay, it offers excellent insulation benefits and is seismically.
The whole footing and slab system is constructed on top of the ground. In present study some of these approaches are studied and compared with each other. With an interesting name, it can make you think that the slab floats like a raft. Feasibility of structural design of members has been ensured under the provision of is. Design of reinforced concrete structures ii twoway slabs. The structural modeling used in most commercially available software, where stems are considered as disjointed from the topping slab does not deliver the advantages associated with waffleslab slab construction. The analysis by stiffness method is carried out using, application. File type cad dwg plan reinforcement drawing format zip file containing. Ribbed and waffle slabs provide a lighter and stiffer slab than an equivalent flat slab, reducing the extent of foundations. Twoway joist concrete slab floor waffle slab system analysis and. Flat slab system is an important division of concrete floor system. If prefab concrete is not in the budget, consider purchasing casts for the concrete waffle slabs. Ribbed floors consisting of equally spaced ribs are usually supported directly by columns.
Manual for design and detailing of reinforced concrete to. This paper focuses on analysis of twoway ribbed and waffle slabs with hidden beams. Pdf optimum design of reinforced concrete waffle slabs. The stem wall supports the building loads and in turn is supported directly by the soil or a footing. Because the waffle slab is constructed on the ground, when the waffle slab is finished it sits about 400mm higher than the surrounding ground. Manual for design and detailing of reinforced concrete to the september 20 code of practice for structural use of concrete 20 2.
Each was examined through different slab aspect rations r of 1, 1. 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. They provide a very good form of construction where slab vibration is an issue, such as laboratories and hospitals. Powered by the equivalent frame method of analysis and design per latest american aci 31814 and canadian csa a23. A slab on grade with an independent stem wall is a concrete floor supported by the soil independently of the rest of the building. The comparison is done on the basis of flexural parameters such as bending moments and shear forces obtained from various methods. Upon completion of the waffle slab house, the ground around the slab is built up by the builder to reduce the height of the slab above the surrounding ground. The prefabricated waffle slab usually costs higher than the other two options. Design of reinforced concrete structures ii twoway slabs 1 1. Waffle raft slab this is the strongest form of standard slab. For slabongrade construction in sdcs d1 and d2, when the conditions described above require an interior braced wall line to have a foundation, the foundation depth along that interior wall must be at least 18 inches below the top of the slab as shown in figure 3. The behaviour and response of flat slab and post tensioned flat slab during earthquake is an important aspect which needs to be explored.
The waffle slab has been considered as monolithically connected to band beams. Evaluation of dynamic behavior of waffle slab to gym center latin american journal of solids and structures 11 2014 111411 the aim of this job is to evaluate the reinforced concrete waffle slab behavior due to the rhyth. The historical discussion includes the evolution of the floor slab from a nonstructural element to an inspired structural system, culminating in nervis patented. They consist of a perimeter footing edge beam and a series of narrow internal beams strip footings at one metre nominal centres running each way. This paper presents an historical and analytical evaluation of the ribbed floor slab systems developed by. The designing team, structural engineers and architects, works together to find the best possible solution that will fulfill the owners whishes. 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. Solid, waffle and banded flat slab systems were analysed. Manual for highways and railways issued by the highways department. Optimum design of reinforced concrete waffle slabs. A mockup precast waffle slab building has been tested with an instrumented hammer fig. Architectural floor plan, engineer plan and slab detail or soil test report.
Irregular cracks are unsightly and difficult to maintain but generally do not affect the integrity of concrete. Nowadays, waffle slabs are a demand for structural designers, as a consequence of architectural design evolution. The foundation is created by placing a series of singleuse plastic forms set directly on grade to create a grid of ribs, and then monolithically pouring a post tensioned, rebar or fiber reinforced concrete. They are either oneway spanning systems known as ribbed slab or a twoway ribbed system known as a waffle slab. Concrete waffle slabs may be purchased and shipped to the construction site as prefabricated the most expensive type or precast sections, or poured onsite.
Grid waffle slab compiled by, submitted to, husen khorajiya r16mce06 prof. The static analysis of waffle slabs aims to determine the range and distribution of displacements and stresses, and ultimate load carrying capacity of the structure, considering a nonlinear behaviour. There are three different types of fg 900 moulds, with heights of 225 mm, 325 mm and 425 mm. Pdf analysis of two way ribbed and waffle slabs with. The waffle pod slab systems allows more accurate specification of concrete quantities, reduces waste and provides a substantial boost to building site efficiency. One hundred and thirty real models were tested for the sake of comparing the traditional oneway composite slab and waffle composite slab in both construction and composite stages. Dynamic features of precast waffle slabs in cleanroom. There are various approaches available for analyzing the waffle slab system. A grid slab is a type of building material that has two directional reinforcement on the outside of the material, giving it the shape of the pockets on a waffle.
Waffle slabs are quickly gaining in popularity in construction projects as they can be shipped to site in different modes including. Design of waffle slab without beams by direct design method. Analysis and design of waffle slabs free download as pdf file. The simplest and most economical floor system is the flat plate, where a plain floor slab about 20. To compare the results obtained for a waffle slab with openings to a waffle slab without openings and find out the percentage reduction in the strength of the slab. Analysis and design of waffle slabs architectural elements civil. In this paper, the optimum design of reinforced concrete waffle slabs is so ught using the simple genetic algorithm. In fact, a lot of builders refer to this type of slab as a floating slab. Act,ext denotes the area of the tensile concrete external to the links. Concrete expands and shrinks with changes in moisture and temperature. Placing the steel any lower than this limit could, however, adversely affect the performance of the slab. Evaluation of dynamic behavior of waffle slab to gym center.
Analysis of steel concrete composite waffle slab with opening. Dynamic features of precast waffle slabs in cleanroom design ning tang, chris wu, blong xiong, michael gendreau, and hal amick. Waffle slab plan view reinforcement detail concrete structure. Where concrete is relatively expensive, spans are generous, and it is not critical to select the smallest floor thickness, a posttensioned waffle slab construction is. Pdf this paper focuses on analysis of twoway ribbed and waffle. Twoway joist concrete slab floor waffle slab system. Calculations for waffle pod slab requirements for plan take off and estimating. The overall tendency is to shrink and this can cause cracking at an early age. Pdf analysis of two way ribbed and waffle slabs with hidden beams. Direct design method is used for the structural analysis and design of slabs.
Slabs are usually used in floor and roof construction. In this paper, the optimum design of reinforced concrete waffle slabs is sought using the simple genetic algorithm. The cost function represents the cost of concrete, steel, and formwork for the slab. Analytical study on strengthening of waffle slab with opening using cfrp sheets and stiffening ribs jeenu mary victor1, soni syed2 1m. Bending will take place in the two directions in a dishlike form. Waffle pod slabs vs raft slabs simon anderson consultants. The waffle pod slab system is a better way of building concrete slabs for new homes, extensions or commercial industrial buildings.
This form of construction is not very common because of the formwork costs and the low fire rating. Numerical and experimental study of a real scale waffle slab. The shaded section depicts the area of the slab only 100mm thick whilst the lighter areas are beams typically 400mm deep. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types. A waffle slab foundation, also called a ribbed slab foundation, is an aboveground type of foundation used to provide loadbearing capacity in expansive, rocky or hydro collapsible soils. Code of practice for structural use of concrete 20 buildings. See more ideas about waffle ceiling, architecture details and architecture design. There are many methods that are used to analyze twoway slabs and the precision of these methods vary depending.