Bending will take place in the two directions in a dishlike fo. It depends of methods of design of such structures in domestic building branch that are bad developed. Therefore it is applied in designing of halls and other buildings where it is necessary to design a large space without columns. The new formscaff coffers can support a slab thickness of 0. Fill height the vertical distance from the top of the top slab of a. 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. The coffer slab is ideal for longer span slabs, carrying heavier loads, and having a. Cofferdam design and construction overview mdot perspective. The lateral loads are independently resisted by shear walls. Ribs between the coffers are reinforced creating concrete beams spanning two ways to support the concrete slab. The design procedures included in this manual are in common use today by most engineers involved in the design of sheet pile retaining structures.
It depends of methods of design of such structures. This provides the perfect connection for service hangars via a wedge nut or similar type device. Here the following topics of flat plate slab is discussed. Simply supported one way slab a rectangular reinforced concrete slab is simplysupported on two masonry walls 250 mm thick and 3. Easy to use software becoming more widely available very accurate if used properly better than grillage. In this paper considered the technology of arrangement of this slabs. Flat slab analysis, design and detailing pdf civil engineering. A reinforced concrete slab is a crucial structural element and is used to provide flat surfacesfloors and ceilings in buildings.
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 waffle slab slab construction. Grid waffle slabs slideshare pdf this paper deals with the problem of optimum design of reinforced concrete twoway ribbed waffle slabs. Technical report 2 penn state college of engineering. Slabs are usually used in floor and roof construction. Introduction concrete slabs on grade are a very common type of concrete construction. The primary purpose of a cofferdam is to create a dry environment for a project to proceed. Design optimization of reinforced concrete waffle slab using. Design of concrete structure i ppt video online download.
Direct design method is used for the structural analysis. A waffle slab is a twoway concrete slab reinforced by ribs in two directions. Usace publications o er 111028152 planning and design of temporary cofferdams and braced excavations technical publications o american institute of steel construction, manual of steel construction 9th ed. 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. Design of waffle slab without beams by direct design method. A copy of the cofferdam design and working drawings shall be provided and maintained at the job site as required by miosha construction safety standard vibratory hammers are permitted see plan notes for exclusions do not pull up or redrive sheeting to match cut off elevation. It provides a working flat surface or a covering shelter in buildings. Troughs are used to form one way spanning concrete slabs. Designer individuals designated by the structural engineer to use this manual to design and detail culverts. The cost function represents the cost of concrete, steel, and formwork for the slab. Twoway joist concrete slab floor waffle slab system. 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. Dec 01, 2016 iconic landmarks using grid slabs chattrapati shivaji terminal, india it is recognized for its innovative column design which also consists waffle design. The part 1 of rcc slab design in etabs 2016 deals the preliminar.
The thickness of the slab is first estimated, based on the minimum thickness of table 1 we have l 15. Waffle slab or ribbed slab is a structural component which is plain on its top and contains grid like system on its bottom surface. Civilknowhow presents the rcc slab design in etabs 2016. Flat slab analysis and design pdf flat slab design pdf 1. The advantage of a coffered slab compared to traditional reinforced concrete slab is a possibility of bridging large spans. 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. Coffered slabs as a perspective type of the reinforced concrete. This makes the williams coffer slab system an extremely cost effective concrete slab. The slab has to carry a distributed permanent action of 1. These enclosures normally consist of sheet piling driven around the perimeter of the excavation. Now let us have a numerical on it to get a full concept on the procedure to design of one way slab.
Flat slab analysis, design and detailing pdf civil. Viewing the published literatures about reinforced concrete slabs, types of slabs and methods of analysis and design of slabs. Waffle slab or ribbed slab construction procedure and advantages. If a bond is used is it something like 5 psi, and then do you check theslab as an unreinforced slab. Metropol parasol, italy it is the worlds largest wooden structure which is made up of waffle system. The slab is represented by a mesh of slab segments called elements joined to each other at nodes. 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.
This paper aims to evaluate the optimum thickness and rebar percentage of solid, hollow block, flat slab and waffle slab based on the simplified design methods stated in most reinforced concrete design codes. Experimental and computational results showed that the widebeam ribs connection is a critical point in the design of the slabs due to the difference in stiffness in the transition zone. Here, we have tried to gather various reading materials available in the web about flat slab floor system in one place. The coffer slab is ideal for longer span slabs, carrying heavier loads, and having a more solid frame to work on. Though the remaining systems are plausible substitutes, the failed to provide. Code description masskg 8005005 form coffer 900 x 525 23.
The axial force, moments and shears for a particular strip are recovered from the analysis on the basis of the wood armer tech. Fire performance of the slab the dovetail presents a very small opening and contributes little to the transfer of heat through the slab in the event of fire. Design of reinforced concrete structures ii twoway slabs 1 1. Asce, secb course content slab on grades construction. The objective of this work was to analyze the adequacy of a design method widely used in. Twoway joist waffle slab design approach and methodology. Culvert extension a portion of a culvert built beyond the limits of a previously existing culvert. 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. Flat slab system is an important division of concrete floor system. A properly reinforced coffer or waffle slab can span the same distances as a regular slab would, weighing far less. The williams coffer slab has superior strength compared to alternative concrete slabs due to the geometric shape of the coffer void, the depth of the slab and the 2 way spanning reinforcing steel bars and steel mesh. Oneway spanning slabs should be treated as beams of unit width and chapter 2 should be followed except for minimum shear reinforcement. The reinforcements are integrated into the slab while being manufactured, without needing to reinforce the assembly on site. Aug 23, 2015 waffle slab can be efficiently cantilevered in two directions up to of a main span.
The steel design was immediately rejected because of floor depth and the lack of necessity to change from a concrete design. Step 2 design forces draw panel of slab and indicate maximum design moments, shears and in. A series of these sunken panels was often used as decoration for a ceiling or a vault, also called caissons boxes, or lacunaria spaces, openings, so that a coffered ceiling can be called a lacunar ceiling. Coffer slab waffle slab twoway joist slab eco built. Design of reinforced concrete structures ii twoway slabs. Waffle slab construction process includes fixing forms, placement of pods on. Reinforced concrete design 1 design of slab examples. Flat slab analysis and design designs beamless concrete slab floors flat slab or waffle slab in accordance with aci 318. Q design a floor slab for an interior room, with clear dimensions of 3. 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.
Concrete slab types construction, cost, and applications. Reinforced concrete design 1 design of slab examples and. The name waffle comes from the grid pattern created by the reinforcing ribs. The concrete is then poured, incorporating all of the abovementioned into a much lighter flat slab. Check the applicable joist dimensional limitations as follows. The direct design method and equivalent frame method for gravity load analysis differ essentially in. Optimum design of reinforced concrete waffle slabs citeseerx. A civil engineer must know all the aspects regarding the flat floor system. The strength of this system means that, depending on loading, spans up to 7 meters can be achieved using wooden purlins and 10. The kwikstrip system produces a coffer grid spacing of 0. A cofferdam is a temporary enclosure in or around a body of water that is constructed to allow dewatering, diversion or damming of an enclosed area.
The slabs are made somewhere else and then brought to the site and assembled. Direct design method is used for the structural analysi s and design of slabs. Twoway joist concrete slab floor waffle slab system analysis and design. A coffer or coffering in architecture is a series of sunken panels in the shape of a square, rectangle, or octagon in a ceiling, soffit or vault.
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. For this slab casting, the special order has to be given for preparing of moulds as per drawing of coffer slab and this will give the extra costing for the floor slab for the design purpose. The benefit of coffered slabs compared to solid slabs was investigated and it was confirmed. Waffle slab or ribbed slab construction procedure and. 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. The construction and design of concrete slabs on grade. These methods have consistently provided successful retaining structures that have performed well in service. 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. The waffle slab or twoway joist slab is a reinforced system covered with in situ concrete.
The hollow core slab was also rejected, again for unsatisfactory floor depth. General a slab is a flat two dimensional planar structural element having thickness small compared to its other two dimensions. According to the way loads are transferred to supporting beams and columns, slabs are classified into two. Design the slab, following the provisions of the aci code. Quick guide to design of one way slab with is code 456. Design of reinforced concrete structures ii twoway slabs 8 c.
Design of slab examples and tutorials by sharifah maszura syed mohsin example 1. Waffle slab analysis and design is similar to the procedure used with flat plates except that special considerations need. 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. Numerical and experimental study of a real scale waffle slab. Design the concrete floor slab system shown below for an. Rcc slab design in etabs 2016 part 1 beginners tutorial. This study presents the information of behaviour punching shear in waffle slabs at slab. Nowadays, waffle slabs are a demand for structural designers, as a consequence of architectural. This lesson covers materials, methods and techniques associated with concrete formwork design and construction for walls slab formwork design will be covered in lesson 2. One way ribbed slab design example pdf material ui icons version. After casting and curing of coffer slab, removing of moulds is difficult and it can be used after the whole process has been. Willem david visser 25072791 submitted in fulfilment of part of the requirements for the. The elements can be triangular, rectangular or quadrilateral. The locations of the strips are usually governed by the locations of the slab supports.
Considering the material used in their construction, cofferdams may be. Pdf coffered slabs as a perspective type of the reinforced. When designing the tremie seal slab, does the weight of the slab need to completely resist the hydrostatic pressure, or is a bond between the sheet piles and the concrete included. Appendix 6 design examples for steel frc slabs onground using yield line method, p. The construction and design of concrete slabs on grade d. Thus a lesser slab depth is needed for fire design. Most of the work is done by the steel anyways, and all the steel needed is alread. The minimum rib width should be determined by consideration of cover, bar spacing. Case study on effective and elegant view of coffer slab. However, when considering design for shear, the spherical void formers used in the cobiax system result in concrete web widths that not only change through the depth of the section, but also in a horizontal direction. Ribbed slabs of dimensions 610, 810 and 1010 were analyzed to indicate the effect of connection between ribs and supported beams on b. Design of slabs and ribs slabs assuming 10 square pans per slab. Cross sectional constant defines torsional properties c x.
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