Construction maintenance of post tensioned slab on ground. Construction of posttensioned slabs on grade is very similar to using reinforcing steel, except for the tensioning step. Actual losses, whether greater or smaller than computed values, have little effect on the design strength of the member but do affect service load conditions i. Example input for design of posttensioned slabsongrade. The execution of the design will be explained with reference. Decisions required for the preliminary design of a floor system that are not discussed in this article, but are covered in other literature, include establishing slab and beam dimensions and concrete cover. Choice of type of slab floor the choice of type of slab for a particular floor depends on many factors. Post tension slab working principle, components and. Design design of slab by strip method aci and bs column strip and middle strip.
Here, we have tried to gather various reading materials available in the web about flat slab floor system in one place. Safe is the ultimate tool for designing concrete floor. Tm 580912 concrete floor slabs on grade subjected to. The codes governing the design of the oneway slab will be aci 31802 and ibc 2003.
Posttension basics how posttensioned slabs are built. Evolution of design methods earliest methods 1965 were semiempirical based upon simplified mathematical models assumed loss of support spanability confirmed by actual performance pti method 1980 based upon rigorous mathematical study of soilstructure interaction most comprehensive design method ever developed. Then, in chapter 3 a wide range of posttensioning applications are illustrated, including foundations, structural walls and service cores. The study was addressed to flat slab systems currently adopted in building designo a square interior panel, with spans between 7. Chapter 9design of posttensioned slabson ground, p. The result is a lightly reinforced slab designed to offset the effects of temperature and shrinkage of the concrete. The example presented here is for twoway posttensioned design.
Whether the project is local or overseas, design codes from around the globe are available for reinforced concrete and posttensioned slab design. Economy of construction is obviously an important consideration, but this is a qualitative argument until specific cases are discussed, and is a geographical variable. Fundamentals of post tensioned design for buildings. The compressive stresses resist the anticipated tension stresses induced by the soil movements, enhancing the performance over a nonprestressed foundation. A normal slab is basically a rcc reinforce cement concrete slab where as a post tentioned slab is the psc prestressed concret slab. Stresses in floor slabs on grade resulting from vehicular loads a re a function. Oneway simply supported slab analysis and design of the slab similar to design of simply supported beam as indicate in the previous chapter. The pti ongdesign ong procedure is used to design a slabon grade. This standard is based upon design of posttensioned slabs onground, 3rd. Solid, waffle and banded flat slab systems were analysed. Someone recommended pt slab design software slab on grade structural engineering general discussion engtips. Concrete floor slabs on grade are subjected to a variety of loads and loading conditions. Construction type continuous span simple span roof floor roof floor oneway solid slabs 50 45 45 40 twoway solid slabs 4548 4045 na na beams 35 30 30 26 oneway joists 42 38 38 35 typically tendons are located near the bottom fiber at positive moment regions and near the top. Framing dead load selfweight superrimposed dead load 25 psf partitions, me, misc.
Does not require trenching into grade or forming fill. Pdf in a developing country like india the benefits of. For a lightly loaded industrial floor, the slab is placed 4 inches thick with tendons in both directions at 2 to 5foot intervals. Part three we will now continue with the study of twoway, posttensioned slab systems, including a complete design example using the equivalent frame concept. Preparing for concrete placement adequately brace forms check the form layout.
Permanent loads include the self weight of the slab and an additional dead loadof 2. Grade the lot for positive drainage away from the foundation during and afterconstruction. The pca and wri slab on grade design methods for industrial floors led to a design for concrete fatigue, even though 2. Concrete design for buildings part three by john p. These materials are originally located at different websites. What is the difference between normal slab and post. Powered by the equivalent frame method of analysis and design per latest american aci 31814 and canadian csa a23. For 1m slab width, moment, shear force, oneway continuous slab for continuous slab, moment and shear force can be obtained from table 3. With some limitations, reinforcement for slabs can be sized using the subgrade drag theory in order to increase the spacing of control or construction joints.
Posttensioned slab on grade eliminated footings and was designed and. It simply requires that all elevation measurements on the slab surface vary by not more than 34 in. Attempts were made to improve knowledge by in depth theoretical studies and experiments on posttensioned plates. Design criteria there are three criteria which must be considered for the design of a conventional one way slab system. The pti design procedure is used to design a slabon grade foundation that will respond. In a posttensioned slab on grade, a grid of highstrength posttensioning tendons replaces the welded wire fabric or conventional rebar normally used.
A3design examples using coe charts a4slab design using posttensioning a5shrinkagecompensatingconcreteexamples chapter lintroduction l. Pdf geotechnical evaluation of the design of posttensioned. The following example illustrates the design methods presented in aci 31805 and ibc 2003. Posttensioned concrete slabs in buildings have many advantages over reinforced.
Increase your efficiency with bidirectional links to the industry leading bim products. Ptislab can be used to design or analyze both posttensioned and conventionally reinforced slabsonground for single and multifamily residential and commercial foundations on expansive and. The design procedure includes determining slab thickness based. Soil design parameters edge moisture variation distance. A detailed explanation will be given of the checksto be carried out, the aspects to be considered in the design and the construction procedures and sequences of a posttensioned slab. Design strips are used to divide up the floor system in two essentially orthogonal directions in modeling the floor for design. A new method for designing floor slabs on grade due to the. After this publication, it was subsequently adopted by the uniform building. The proposed slab system must be able to be constructed at a reasonable cost. Design of posttensioned slabsonground 3rd edition yumpu. To get the excel sheet join as loving fansub member to this channel. The following table of prestress losses is recommended for the design of posttensioned members, and does not include friction or wedge set losses. For residential construction, tendons at 48 inches on center are common. Slab on grade free download as powerpoint presentation.
A4 slab design using posttensioning a5shrinkagecompensatingconcreteexamples chapter lintroduction l. 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. The posttensioning institute pti design manual6 gives recommended spantothickness ratios for slabs and spantodepth ratios for beams. A design strip is a region assigned to a hypothetical support line that joins a line of columns and or walls in one direction. For example, in a 4inch 100 mm thick slab the joint spacing should be about saw cut tooled wall or column expansion joint material slab on grade column contraction joints intersect at diagonals of the square form openings which will be filled after floor has hardened concrete cracks below joints slab isolated from. This should help the reader to rationally select an efficient overall structural concept for a building. Institute pti design procedure for designing posttensioned slabs onground. Flat slab system is an important division of concrete floor system.
Stiffened slab on grade elevated structural slab on piers stiffened slab on grade and on piers thin post tensioned slab figure 1. Concrete slab on grade analysis calculator for post or. For further information on these issues, see construction of elevated concrete slabs, a threepart series in concrete construction, november 1990, january 1991, and march 1991. For most large pt slabs, we also have to model the drop panels at the column supports. Powered by a sophisticated fem solver increasing capacity and substantially speeding up solution for large and complex models, spmats v8. In this context, design is defined as the decisionmaking process of planning, sizing.
Slab design reading assignment chapter 9 of text and, chapter of aci31802 introduction aci318 code provides two design procedures for slab systems. Flat slab analysis, design and detailing pdf civil. Unless specifically stated otherwise, all foundation parameters. Posttensioned oneway slab pennsylvania state university. Slabs on grade are pavements not generally structural elements. This hybridisation helps achieve the formation of a much thinner slab with a longer span devoid of any columnfree spaces. Concrete slab resting on grade containing steel reinforcement which consists of either a welded wire fabric or deformed reinforcing steel bars. Posttensioned concrete slabs augi the worlds largest. Pavements pass loads through compression to the supporting soil as long as the soils deformations are low, there is negligible bending in the slab. Post tension slab is a combination of conventional slab reinforcement and additional protruding highstrength steel tendons, which are consequently subjected to tension after the concrete has set. Online concrete slab on grade analysis calculator for slab subjected to interior concentrated post or wheel loading assuming slab is reinforced for shrinkage and temperature only.
The design procedure set forth in that publication had at that time been in use by the author for about 15 years. Ongrade concrete floor slabs shall be placed on a 4inch fill of coarse aggregate or on a 2inch sand bed over a moisture barrier membrane. Some foundations used for light buildings on shrinkswell soils. In general they recognize the influence of the live load levei, at least qualitatively. A psc is applied with a compressive stress on the cross section in advance before the application of loading on. The concrete slab on grade is the most popular foundation type in the southeast. Selection of design strips and the design procedure are not the subject of discussion. Aci 360, design of slabs on grade, refers to this as a type b slab. Calculators for structural engineers, construction professionals and steel building specifiers. The design sections along the various design strips are checked for strength at service stage and ultimate stage conditions. First model a flat slab for the entire area, then model the drop panels as separate slabs from the bottom of the flat slab. Slabonground posttensioned slabsonground provide a costefficient, highperformance solution for problems associated with groundsupported residential foundations on shrinkswell soils. Similarly the fpa used the option determine per pti 3 rd edition manual charts in.
Hi all, can anyone recommend a good design software for posttension slab on grade slab. Reinforcing bars shall be spaced at intervals not exceeding 16 inches each way. The design uses the program adapt floor pro release 20092010 featuring the hong kong code. A civil engineer must know all the aspects regarding the flat floor system. Cables are arranged as indicated by the engineer and chaired to run through the center of the slab. Unless otherwise noted, all referenced table, figure, and equation numbers are from these books. Development of the design approach the primary design issues for stiffened slabs on grade are the sizing of the beams that stiffened the slab and the.
Pdf several changes have been introduced in going from the 2 nd edition to the 3 rd edition of the pti procedure for the design of slabsongrade on. Most of these documents point out that the slendemess limits are only indicated to give some guidance in estimating the slab thickness. Pti design method based on ribbed foundation system. The proposed slab system must meet the current code.
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