Continuous ribbed slabs concrete structures eurocode. Jul 02, 20 introduction hollow block and ribbed slabs are formed by placing blocks on the slab and concrete ribs. May 12, 2020 the ribbed part of the slab may be designed to span between solid areas. Design of slab examples and tutorials by sharifah maszura syed mohsin example 1.
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 name waffle comes from the grid pattern created by the reinforcing ribs. Design of slabs and ribs slabs assuming 10 square pans per slab. Reference 5 focused on analysis of twoway ribbed slabs with. Ribbed and waffle slabs provide a lighter and stiffer slab than an equivalent flat slab, reducing the extent of foundations. The intended audiences for the use of this document are members of ptis slab onground committee as well as engineers and others involved in the design of foundations for residential and other lowrise structures. Aug 09, 2014 ribbed slabs are suitable for medium to heavy loads, can span reasonable distances, are very stiff and particularly suitable where the soffit is exposed. In many cases, long spans are desirable in the building. To analyze and design three ribbed slabs manually of 10m square module, 12. Structural design versus cost comparison of solid and ribbed slab constructed building. In case of hollow block slab voided blocks are placed to reduce the total weight of the slab.
In case of ribbed slab the blocks are not permanent. The model provides the actual behavior for ribbed slab by analyzing the structure as oneunite in two dimensions. This manual p rescribes the criteria for the design of concrete floor slabs on grade in buildings for heavy loads and is applicable to all elements responsible for military construction. Mn and solving for the required effective depth d, given that b 12 in. The ribbed slab was analyzed exactly by finite element theory through sap 2000 program.
The ratio of the total costs was found to be within the range 1. Flat slab analysis and design pdf flat slab design pdf 1 this pdf lecture is created by eng. Ribbed slabs types and its advantages in construction purpose. Ribbed slabs oneway joists introducing voids to the soffit of a slab reduces dead weight and increases the efficiency of the concrete section. The system exhibits higher stiffness and smaller defections. Ribbed slab design spreadsheets to eurocode ribbed slabs are widely used in many countries. 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. Manual for design and detailing of reinforced concrete to. Sep 04, 2014 10 design of oneway solid slabs reinforcement, 2. However, having to accommodate torsions induced in supporting beams and columns usually makes it simpler to design from centreline of support to centreline of support. The slab is the flange of the beam and the extended part is the web. All the electrical appliances can be installed easily in the gap of the ribs which can be architecturally aesthetic.
Flat slab analysis, design and detailing pdf civil. However, there are significant differences between the behaviour of ribbed and plain plates, the increased ratio of flexural to torsional rigidities in a ribbed plate resulting in a substantial reduction in the load that is transmitted by. Jul 02, 2015 for the love of physics walter lewin may 16, 2011 duration. Experimental and computational results showed that the widebeam ribs connection is a critical point in the design of the slabs due to the. Design of reinforced concrete structures ii twoway slabs 1 1.
Slab design reading assignment chapter 9 of text and, chapter of aci31802 introduction aci318 code provides two design procedures for slab systems. Tensioning building structures march 12, 2020 2020 educode las vegas. A minimum rib spacing s of 6 ft shall be used in the design of ribbed slabs. The material consumption and economical aspects of ribbed slabs are often neglected by the designers. For slabs spanning in both directions published tables and charts should be used to find bending moment and shear per unit width of slab. Concrete slab behave primarily as flexural members and the design is similar to that of beams. The ribs span d 2 into the solid areas which are assumed to act as beams in the orthogonal direction. A slightly deeper section is required but these stiffer floors facilitate longer spans and provision of holes. Analysis of two way ribbed and waffle slabs with hidden beams. The equivalent thickness based on moment of inertia is used to find slab stiffness considering the ribs in the direction of the analysis only. Design of oneway slabs the structural action of a oneway slab may be visualized in terms of the deformed shape of the loaded surface. Institute pti design procedure for designing posttensioned slabs onground. This type of slabs or flooring system consists of series of small closed.
The waffle slab is also sometimes termed as ribbed slab system but you would find it interesting to know that ribbed and waffle slab are somehow two different things. For design such this slab i mean detailed reinforcement can be in robot. Analysis of two way ribbed and waffle slabs with hidden beams article pdf available in international journal for computational civil and structural engineering volume 4, no 3, 2014 january. The slab has to carry a distributed permanent action of 1. 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. 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. This is attributed to the rapid shattering, ease of construction, and the reduction in the time of erection.
Figure 1 shows a rectangular slab, simply supported along its two opposite long edges and free of any support along the two. Optimum design of reinforced concrete waffle slabs alaa c. Sep 03, 2011 design of reinforced concrete slabs 107 b 1. Appendix 6 design examples for steel frc slabs onground using yield line method, p. Oneway and twoway slabs university of asia pacific. Designed as a series of parallel tbeams and economical for medium spans with light to medium live loads. Accordingly, main reinforcement is required in the two directions. Long slab spans can be constructed through ribbed and waffle slabs. Structural ribbed concrete slabs cupolex sustainable. Reinforced concrete design 1 design of slab examples. These conditions are set out in last section dealing with oneway ribbed slabs. From the previous analysis of the ribbed slab in the traditional methods it is. Pti recommendations for ribbed slab design include spacing limitations for the ribs and limits on the rib depth and width. Simply supported one way slab a rectangular reinforced concrete slab is simplysupported on two masonry walls 250 mm thick and 3.
Introducing voids to the soffit of a slab reduces dead weight and increases the efficiency of the concrete. Shear strength of beamless slabs usually a controlling factor. Bending will take place in the two directions in a dishlike form. This type of slabs or flooring system consists of series of small closed spaced reinforced concrete tbeams. Slabs may be supported on monolithic concrete beam, steel beams, walls or directly over the columns. Reinforced concrete ribbed slabs with widebeam lajes. It would be a design delimiter for ribbed slabs since these widebeams are only dimensioned to resist the bending moment and beam shear. Appendix 6design examples for steel frc slabsonground using yield line method, p. Designing a one way ribbed concrete joist floor system per. Cost comparison between frames with solid slab and ribbed.
They provide a very good form of construction where slab vibration is an issue, such as laboratories and hospitals. 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. Check the applicable joist dimensional limitations as follows. A reinforced concrete slab is built integrally with its supports and consists of equal span of 15 ft. Able to carry heavier loads and span longer than ribbed slabs. In this research, optimum design of reinforced cement concrete rcc ribbed slab, also known as waffle slab according to the indian rcc code is 456. Dec 06, 2017 basic of ribbed slab with aci 31802 code requirements. 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 slab design spreadsheets to eurocode engineering books. Design of waffle slab without beams by direct design method.
Mathcad program and show its impact on teaching the analysis and design of twoway ribbed slabs. The blocks are considered as nonstructural element as they do not contribute to strength of. A concrete slab is a common structural element of modern buildings, consisting of a flat, horizontal surface made of cast concrete. Posttensioned pt slabs are typically flat slabs, band beam and slabs or ribbed slabs.
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. When one says ribbed slab it is actually a one way spanning system with ribs where as in waffle slab the joists form a two way system. The design procedure set forth in that publication had at that time been in use by the author for about 15 years. The minimum thickness can be determined by many factors. The cost is managed by supervision of non skilled laborers, following the recommendations in. Heavy loads in building s such as warehouses include moving load s, stationary live loads, and wall loads. Design and construction of conventionally reinforced ribbed mat slabs any ed material included in this document is identified at its point of use. Reinforced concrete ribbed slabs with widebeam slabs with widebeam could be assessed, four slabs supported on square columns with sides of 200 mm and thickness of 50 mm. Concrete rib construction method, crcm uses the engineering technology to design the elements structurals to handle the loads originated by climatic and or geographical location of the project. Tm 580912 concrete floor slabs on grade subjected to. The flat slab is a reinforced concrete slab supported directly by concrete columns or.
Use of the ed material apart from this document must have the permission of the ed holder. A computer program is written using matlab to formulate the problem and perform the structural analysis and design of those slabs by the direct design method. Ribbed slabs are made up of wide band beams running between columns with narrow ribs spanning the. In addition to general ultimate and serviceability limit state design issues, practical design considerations such as the formation of holes in the slab, support details, fire protection, and attachments to the slab are discussed. Ribbed slabs of dimensions 610, 810 and 1010 were analyzed to indicate the effect of connection between ribs and supported beams on b. Twoway joist concrete slab floor waffle slab system. The main advantages of using ribbed slabs are permitting a given minimum clear height to be maintained with a reduced overall story height, covering a big horizontal area, simple formwork and reduced own weight.
Teaching twoway ribbed slab analysis and design using the. Pro software was used which is unadapted or not well known in ethiopia. Slab cast integrally with a series of closely spaced joist which in turn are supported by a set of beams. The saving of materials tends to be offset by some. Slabs of uniform thickness bending and reinforced in two directions and supported directly by columns without beams. Moments for design may be taken from table 3 for slabs simply supported on four sides. Structural ribbed concrete slabs the cupolex floor slab can be fully or partially suspended on piles, stem walls or gradeedge beams. The live loads and effective depth of each slab were taken from standard code ebcs 11995, table 2. This pdf file contains a chapter of 23 pages with various aspects of flat slabs including four example of flat slab design. 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. Example on structural design of waffle slab structville. Flat slab analysis, design and detailing pdf civil engineering. A finite element model may be created to analyse a complicated loading arrangement.
The general provisions for construction and design procedure are given in cop 20. In addition, the scope of this study is to design oneway ribbed slab and twoway solid slab by using esteem software. Optimum design of a reinforced concrete ribbed slab. One way slab design procedure with example design of one. Manual for design and detailing of reinforced concrete to september 20 the code of practice for structural use of concrete 20 contents 1. Analytical design of ribbed flat slabs the institution. Ribbed and waffle slabs types, advantages, disadvantages. Egyptian code for design and construction of reinforcement concrete structures. 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.
Pdf structural design versus cost comparison of solid. They may be supported on two opposite sides only fig. Ribbed or waffle slabs are an easy solution for this purpose. After this publication, it was subsequently adopted by the uniform building. 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. In reality, sandwich slabs are ribbed slabs with a slab placed both to their upper and lower surface. The computational analysis helped to better understand the slabs. The structure is analyzed using the direct design method. Pt slabs offer the thinnest slab type, as concrete is worked to its strengths, mostly being kept in compression. It is important to think about the importance and efficacy of optimization of such structural elements. In the one way ribbed slab where the ribs are in one direction, it is assumed.
Ribbed slab design spreadsheets to eurocode engineering. Twoway joist waffle slab design approach and methodology. Nalitolela for the department of civil engineering of mbeya university of science and technology. These slabs were one way and the ribs were supported directly on the beams without solid part. Oneway and twoway slabs oneway slabs transfer the imposed loads in one direction only. The design of composite slabs and beams is discussed in detail in relation to the eurocodes and bs 5950. 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. Ribbed or waffle slab is a slab system which consists of series of parallel reinforced concrete t beams framing into reinforced concrete girders. The objective function is the combined cost of the reinforcement, concrete and formwork which sums up the cost of the ribbed slab.
1363 150 830 39 1349 827 1508 360 1433 232 468 724 483 1139 1043 1165 223 1240 989 554 790 1148 1351 1428 285 1228 305 1244 806 1478 1462 390 180 924