In the one way ribbed slab where the ribs are in one direction, it is assumed. Ribbed or waffle slab is a slab system which consists of series of parallel reinforced concrete t beams framing into reinforced concrete girders. This is attributed to the rapid shattering, ease of construction, and the reduction in the time of erection. In this section, two types will be discussed, oneway solid slabs and oneway ribbed slabs. Optimum design of reinforced concrete waffle slabs alaa c. They are either oneway spanning systems known as ribbed slab or a twoway ribbed system known as a waffle slab. Flat slab system is an important division of concrete floor system. Jul 02, 20 introduction hollow block and ribbed slabs are formed by placing blocks on the slab and concrete ribs. Ribbed and waffle slabs provide a lighter and stiffer slab than an equivalent flat slab, reducing the extent of foundations. The design procedure set forth in that publication had at that time been in use by the author for about 15 years. Analysis of two way ribbed and waffle slabs with hidden beams. Manual for design and detailing of reinforced concrete to the september 20 code of practice for structural use of concrete 20 2. In this example, the latter option will be used to achieve better understanding for the design of twoway joist slab often called twoway ribbed slab or waffle slab.
In reality, sandwich slabs are ribbed slabs with a slab placed both to their upper and lower surface. In waffle slab design where the drop panels create a large critical shear perimeter, the factor b o d has limited contribution and is traditionally neglected for simplicity and conservatism. The ratio of the total costs was found to be within the range 1. The saving of materials tends to be offset by some. Ribbed slab design spreadsheets to eurocode engineering books. This paper focuses on analysis of twoway ribbed and waffle slabs with hidden beams. Ribbed slab design spreadsheet civil engineering community. Design of reinforced concrete structures ii twoway slabs 1 1. Depending on the wide beams width and the top slabs thickness the shear surface area to form.
Pdf structural design versus cost comparison of solid. In case of ribbed slab the blocks are not permanent. In oneway ribbed slab, loads are transferred in one direction, and the main reinforcement is distributed in the same direction of the load. The general provisions for construction and design procedure are given in cop 20. In the analysis of ribbed slab as solid slab traditional, the structural system of the ribs is considered as beams supported on main cross beams which are considered as rigid supports. It would be a design delimiter for ribbed slabs since these widebeams are only dimensioned to resist the bending moment and beam shear. Civilax is the knowledge base covering all disciplines in civil engineering. Twoway joist waffle slab design approach and methodology. Ribbed slab design spreadsheets to eurocode engineering. Ribbed slab free download as powerpoint presentation.
One way slab being supported on two opposite sides only leads to the structural action in single direction. The relative position of one with respect to the other provides the stiffness characteristic of a ribbed slab. The model adopts the shear perimeter as that in bs81105, at 1. There are various established methods for analysing ribbed slabs and dealing with the solid areas. One method is to ignore the weight of the solid part of the slab in the analysis of the ribbed slab and the weight of the solid area added to the supporting beam. The service live load is 100 psf and 4000 psi concrete is specified for use with steel with a yield stress equal to 60000 psi. In addition, the scope of this study is to design oneway ribbed slab and twoway solid slab by using esteem software. 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. Ribbed and waffle slabs types, advantages, disadvantages. Structural design versus cost comparison of solid and ribbed slab constructed building. From the previous analysis of the ribbed slab in the traditional methods it is.
Continuous ribbed slabs concrete structures eurocode. Flat slab analysis, design and detailing pdf civil. One way slab design how to design one way slab daily civil. Moments for design may be taken from table 3 for slabs simply supported on four sides. Using udls simplifies the analysis and remains popular. 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. Experimental and computational results showed that the widebeam ribs connection is a critical point in the design of the slabs due to the. Aci commentary states that limiting the values of fy and fyt used in design of shear reinforcement to 60,000 psi provides a control on diagonal crack width. Design of slabs and ribs slabs assuming 10 square pans per slab. Manual for design and detailing of reinforced concrete to. In many domestic and industrial buildings, a thick concrete slab supported on.
Pdf structural design versus cost comparison of solid and. But crcm uses concrete a material used more than 3,000. Ribbed slab design spreadsheets to eurocode ribbed slabs are widely used in many countries. Ribbed slabs are made up of wide band beams running between columns with narrow ribs spanning the. Structural ribbed concrete slabs cupolex sustainable. Design of reinforced concrete structures ii twoway slabs. Example on structural design of waffle slab structville.
See more ideas about waffle ceiling, architecture and ceiling design. Reference 5 focused on analysis of twoway ribbed slabs with. Egyptian code for design and construction of reinforcement concrete structures. Here, we have tried to gather various reading materials available in the web about flat slab floor system in one place. This paper presents an experimental and computational study on ribbed slabs with widebeam, two oneway slabs and two twoway slabs. The equivalent thickness based on moment of inertia is used to find slab stiffness considering the ribs in the direction. Accordingly, main reinforcement is required in the two directions.
Ribbed slabs have been widely used in buildings due to their many advantages, especially the decrease of concrete below the neutral line. Sandwich slabs may have the disadvantage of a larger weight compared to the ribbed ones but on the other hand, they have the advantage that their spans and supports behave in the same proper way. Extend horizontally from center line column at least 16 center line span. In general, it is seen that in solid slab a portion of concrete below the. With accurate to temperature and shrinkage, minimum. For 1m slab width, moment, shear force, oneway continuous slab for continuous slab, moment and shear force can be obtained from table 3. Reinforced concrete ribbed slabs with widebeam lajes. Ribbed slabs oneway joists introducing voids to the soffit of a slab reduces dead weight and increases the efficiency of the concrete section.
The proposed design model takes the section variations of a ribbed slab into account while predicting the punching capacity. Introduction hollow block and ribbed slabs are formed by placing blocks on the slab and concrete ribs. They are either oneway spanning systems known as a ribbed slab or a twoway ribbed system known as a waffle slab. Steelreinforced slabs, typically between 100 and 500 mm thick, are most often used to construct floors and ceilings, while thinner mud slabs may be used for exterior paving see below. After this publication, it was subsequently adopted by the uniform building. Additional reinforced internal ribs are then used in the slab by introducing pontex, the structural cupolex accessory to provide a structure capable of spanning between foundations or piles. Structural ribbed concrete slabs the cupolex floor slab can be fully or partially suspended on piles, stem walls or gradeedge beams. Ribbed slab design spreadsheet free download description.
Dec 06, 2017 basic of ribbed slab with aci 31802 code requirements. Teaching twoway ribbed slab analysis and design using the. Slab design reading assignment chapter 9 of text and, chapter of aci31802 introduction aci318 code provides two design procedures for slab systems. A concrete slab is a common structural element of modern buildings, consisting of a flat, horizontal surface made of cast concrete. These conditions are set out in last section dealing with oneway ribbed slabs. In case of hollow block slab voided blocks are placed to reduce the total weight of the slab. For the purpose of this document, rrms is defined as a system of stiffening beams and slab constructed of. In this study, the aci direct design method is used as a manual. In general, it is seen that in solid slab a portion of concrete below the neutral axis remains ineffective.
The slab is the flange of the beam and the extended part is the web. Design of waffle slab without beams by direct design method. Ribbed floors consisting of equally spaced ribs are usually supported directly by columns. The blocks are considered as nonstructural element as they do not contribute to strength of.
For the purposes of analysis and design, the ribbed slab will be replaced with a solid slab of equivalent moment of inertia, weight, punching shear capacity, and oneway shear capacity. Find depth of slab using deflection control criteria. Check the applicable joist dimensional limitations as follows. Slab depth calculation based on the design span and the imposed load it is possible to make a preliminary assessment of the required thickness of a skydome slab, as shown in the chart to the right. Twoway joist concrete slab floor waffle slab system. Ribbed slab floors are most economical for buildings such as hospitals, schools, hotels, and apartment construction where loads are somewhat small and the spans are relatively large. Bending will take place in the two directions in a dishlike form. Tensioning building structures march 12, 2020 2020 educode las vegas. Crcm manual 4 crcm means concrete rib construction method, the word method, can create confusion, because the icc ibc uses such word in the section 1701. Mathcad program and show its impact on teaching the analysis and design of twoway ribbed slabs.
This document provides guidance for the design and construction of conventionally reinforced ribbed mat slab rrms foundation systems. A reinforced concrete slab is built integrally with its supports and consists of equal span of 15 ft. These materials are originally located at different websites. Jul 02, 2015 oneway concrete slab design part 1 concept explained and minimum slab thickness canadian code duration. They provide a very good form of construction where slab vibration is an issue, such as laboratories and hospitals. A civil engineer must know all the aspects regarding the flat floor system. This form of construction is not very common because of the formwork costs and the low fire rating. 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. For the purposes of analysis and design, the ribbed slab can be replaced with a solid slab of equivalent moment of inertia, weight, punching shear capacity, and oneway shear capacity. Flat slab analysis, design and detailing pdf civil engineering. This paper deals with the problem of optimum design of reinforced concrete twoway ribbed waffle slabs using genetic algorithms. In the analysis of ribbed slab as solid slab traditional, the structural system of. Oneway simply supported slab analysis and design of the slab similar to design of simply supported beam as indicate in the previous chapter.