Posttension basics how posttensioned slabs are built. A detailed explanation will be given of the checksto. Post tensioning for twoway flat plate construction figure 2. Twoway posttensioned design amsysco post tensioning. Nowadays, design of modern an architectural building structures requires the use of slender and free from numerous supports slabs. The design of posttensioned flat slab can be done by. This course is intended to be an introductory course for structural engineers new to post tensioned.
For this, the concrete slab is tensioned with a process called prestressing and the slab of concrete which comes out after this process is known. Post tension design of slab there is document post tension design of slab available here for reading and downloading. Pdf analysis and design of rcc and posttensioned flat slabs. The following table of prestress losses is recommended for the design of post tensioned members, and does not include friction or wedge set losses. General overview of posttensioned concrete design instructor. To create a slab using this method, plastic sleevecovered steel cables are laid in a grid running in both directions. This video tutorial is about pts post tension slab design which is trained by master of structural engineering mr. While using this method more precautions has to be made for shear and deflection criteria for the slabs.
Jurgens his article presents a set of guidelines intended to t assist designers in routine post tensioning design, beginning with a discussion of the initial decisions that must be made to design post tensioned floor. April 8, 2017 admin design comments off on download tr43 post tensioned concrete floors design handbook 2nd by concrete society working party pdf by concrete society working party seeing that post tensioned concrete flooring was once first released in 1994, using put up tensioned concrete flooring in constructions has endured to develop always. It provides an architect the freedom to work freely with his designs. Posttension basics how posttensioned slabs are built the. The concrete centre provides material, design and construction guidance. Tendon profile of a continuous post tensioned beam. An overview is presented on the application and design of such floor systems, and the commonly selected castinplace floor system configurations are described. Design of post tensioned buildings for wind and seismic forces, including diaphragm design. Post tensioned slab has an advantage over others as it makes a very efficient base for floor design with thin slabs and columnless spaces in larger spans. Once the concrete has gained strength to 2000 psi, typically within the 3 to 10 days recommended by pti, the tendons are stressed. Limitations on slab dimensions and required material quantities are presented and discussed. Twoway slab systems twoway post tensioned slab systems have been widely used in building construction for many decades.
Post tension slab working principle, components and. This was achieved by using a post tensioned concrete slab with post tensioned upturn concrete beams. Post tensioned slabs application pt reinforcement is used more in the residential market than in any other sector of construction. Cables are arranged as indicated by the engineer and chaired to run through the center of the slab. Post tensioning concrete increases the many benefits associated with a concrete framed building. Net, which many engineers have come to trust over the years for its accuracy and flexibility. The concrete society in england publishes a design handbook6 for post tensioned concrete floors that includes recommendations for twoway slabs with both bonded and unbonded tendons. The preliminary design proposal was to build the entire slab in a single pour, but due to. Framing dead load selfweight superrimposed dead load 25 psf partitions, me, misc.
The design of post tensioned flat slab can be done by using load balancing and equivalent frame. Post tensioned pt concrete floors are now widely used in the uk, particularly for highrise buildings. Design objective to mitigate the probability of undesirable effects in. Nov 25, 2008 post tensioned concrete is a term heard more and more in the construction industry today.
Fewer joints large concrete areas, such as tennis courts, parking lots. Our aim is to enable all those involved in the design, use and performance of concrete and masonry to realise the potential of. Anyway, application for the post tensioning slabs system include. To maximize views for the premium units in the upper floors, more glazing and less concrete wall had to be incorporated into the design of the north back face of the tower at levels 30 through 38. It is based on the recommendations of aci318 as expounded in adapt technical note tn292. Jurgens his article presents a set of guidelines intended to t assist designers in routine post tensioning design, beginning with a discussion of the initial decisions that must be made to design post tensioned floor members. Tributary slab widths for equivalent frames aalami, b.
A more detailed guide to the design of pt floors can be found in the concrete societys technical report 43 tr43. Post tensioned concrete floors form a large proportion of all prestressed concrete construction. Posttensioning institute pti design manual6 gives recommended spantothickness ratios for slabs and. Reducing the slab thickness has the benefit of reducing the floor dead loads, which results in an economical design of the concrete columns and footings. 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 post tensioned slab. Use of post tensioned flat slab is now a day becoming cost effective solution. To maximize views for the premium units in the upper floors, more glazing and less concrete wall had to be incorporated into the design of the north back face of the tower at. Aalami a must have reference book for engineers, students, contractors, building officials, and researchers. Longer spans can be achieved due to prestress, which can also be used to counteract deflections.
The recommendations derived from these and other studies vary from extremely light to extremely heavy. 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. A residential post tensioned concrete slab will typically be 8 inches thick and use 3000 psi concrete. Design of slabs onground reported by aci committee 360 aci 360r06 this document presents information on the design of slabs onground, primarily industrial floors.
Jan 24, 2015 post tension slab although concrete is a strong material for construction, it is not resistant to breakdown especially where longer concrete slabs are required like in a bridge or a length of a beam. Low to high rise residential and commercial buildings industrial floor slabs on the ground. The execution of the design will be explained with reference. Fundamentals of posttensioned concrete design for buildings part one. Structural calculations for posttensioned flat slab. For slabs with both bonded and unbonded tendons, this handbook recommends exactly the same minimum amount of bonded reinforcement over. Design method may not be used for twoway, posttensioned slab systems. The design of posttensioned flat slab can be done by using load balancing and equivalent frame. Post tension slab advantages and disadvantages of post. Agenda design objective response of floor slabs to temperature effects design procedure for control of temperature cracks example. The use of post tensioned flat slab is increasing widely, due to its advantages over traditional concrete. The purpose of this publication is to widen the understanding of post tensioned floor construction and show the considerable benefits which include minimum storey heights, rapid construction, economy, maximum design flexibility, minimum number of columns, optimum clear spans, jointfree, crackfree. Tn342 design example 2way mondada 093090 adapt corporation.
Construction of post tensioned slabs on grade is very similar to using reinforcing steel, except for the tensioning step. The file extension pdf and ranks to the documents category. For professionals engaged in posttensioning design. Us post tensioning industry owes its existence to lift slab construction first lift slab buildings in the us were built in the mid 1950s using nonprestressed slabs problems with deflections and slab weight in long 2way spans to solve deflection and weight problems, lift slab companies changed to post tensioned slabs. However, the beams divide the plenum space into channels, reducing the overall utility. Design floors and foundations reliably and efficiently, saving time and money, and overcoming the most common concerns you face as a designer. Pt designer is a computer program for the design and analysis of linear post tensioned concrete floor systems. In post tensioned floor slab construction, the placement of post tensioning tendons and associated nonprestressed reinforcement does not strictly follow the practice of nonprestressed slabs. Use the download button below or simple online reader. Guidelines for the design of posttensioned floors by bijan o. The program is developed around the robust computational core of two popular programs ptdata. Concrete slab design software economically design post tensioned and reinforced concrete floors including slabs, mats, and rafts, with exceptional visibility into compliance, efficiency, and practicality.
Analysis and design of rcc and posttensioned flat slabs. Post tensioned concrete design table 11 list of symbols used in the aci 31808 code m bal design moment resistance of a section with tendons and the necessary mild reinforcement to reach the balanced condition, nmm m u factored moment at section, lbin n c tension force in concrete due to unfactored dead load plus live load, lb p. The alternative design proposed was a 250mm thick post tensioned base slab which was tapered to a 700mm thickening at the base of the walls to deal with the wall moments and base shear. Fundamentals of posttensioned concrete design for buildings part one a suncam online continuing education course. Part three continues with the study of twoway, post tensioned slab systems, including. Commercial opportunities ccl post tensioning results in thinner concrete slabs. Brendon burley structural option post tensioned twoway slab post tensioned twoway slab introduction the filigree beam system creates a thin lightweight floor system that leaves plenty of open plenum space for mechanical and electrical equipment. The posttensioned system was designed to span the same lengths as the composite system while maintaining a relatively thin. Precast posttensioned segmental construction is defined as a method of construction for bridges, buildings, tanks, silos, cooling towers, tunnels and other structures in which primary load carrying members are composed of precast concrete segments post tensioned together. Post tensioned slabs use highstrength tensioned steel strands to compress the slabs, keeping the majority of the concrete in compression. Example input for design of post tensioned slabs ongrade the 2000 international building code ibc includes special provisions for the design of post tensioned floor slabs on expansive soils. Clean out of the footings after a rain is much faster and neater than rebar type foundations. The advantages are many, when compared to non post tensioned systems, and include thinner slabs, lighter structures, lower floor to floor heights, less mild reinforcing steel, and less short and long term deflections.
The post tensioning method is the best way to create stronger, more reliable concrete slabs. This method is a better way to construct a slab foundation to be more resistant to cracking and deflection. Engineers had to learn how to design pt floor systems with levels of cracking normally accepted in nonprestressed floor systems. For example, the amount of fuel consumed during a fire test of an exposed concrete floor specimen is likely to be 10.
This article provides information on how to scheme a pt slab and how the use of post tensioning affects the rest of the structure. A 2 2area 2 a c 2 2 post tensioned concrete design table 11 list of symbols used in the aci 31808 code cp area enclosed by the outside perimeter of the section, in a g gross area of concrete, in a 2 l total area of longitudinal reinforcement to resist torsion, in a o area enclosed by the shear flow path, sqin a oh area enclosed by the centerline of the outermost closed. In california, post tensioned floor slabs are the primary choice in concrete floor construction. Review of the essential technical knowhow for efficient design.
Post tensioned floors design for temperature florian aalami april 28, 2015. Pt designer is a computer program for the design and analysis of linear posttensioned concrete floor systems. Deflection check of post tensioned floor systems this narrative outlines the procedure for deflection check in design of post tensioned floor systems. Five underlying features of post tensioned construction allow greater flexibility in reinforcement layout. Unbonded tendons offer unique structural advantages not found in. Allowable deflection limits refer to table 1 of the appendix.
This stronger, thinner slab also saves money on concrete. Post tensioning of foundations, transfer beams and plates, post tensioned masonry and the combination of precast elements with castinplace concrete by means of post tensioning offer other interesting opportunities. By doing the comparative analysis and design of post tensioned flat slab with a conventional slab, we can show how beneficial will be the process of making pt flat slab than other slabs. Unless otherwise noted, all referenced table, figure, and equation numbers are from these books. It was actually the widespread use of the post tensioned slab onground which induced this interest in design procedure and in many studies of reported slab failures.
The following example illustrates the design methods presented in aci 31805 and ibc 2003. These specifications are included chapter 18, division iii, section 1816 titled. The example presented here is for twoway posttensioned design. Post tensioned slabs can be designed to be 100% crack free, which means the slabs. As these slabs are very easy to construct, post tensioned slabs are preferred for industrial, commercial and residential floor slab construction. Roof floor roof floor oneway solid slabs 50 45 45 40 twoway solid slabs 4548 4045 na na.
Guidelines for the design of posttensioned concrete floors. Post tension slab although concrete is a strong material for construction, it is not resistant to breakdown especially where longer concrete slabs are required like in a bridge or a length of a beam. This method of reinforcing concrete enables a designer to take advantage of the considerable benefits provided by prestressed concrete while retaining the flexibility afforded by the castinplace method of building concrete structures. These results were compared with other information, i. The present study focuses on posttensioned flat slab systems with respect to strength. The decision to use bonded tendons in twoway posttensioned slabs must be made very carefully, particularly when the slab design is governed by aci 31811. Architectural benefits post tensioned slab has an advantage over others as it makes a very efficient base for floor design with thin slabs and columnless spaces in larger spans. Guidelines for the design of post tensioned floors by bijan o. Pt slabs offer the thinnest slab type, as concrete is worked to its strengths, mostly being kept in compression. The program is divided into three separate screens, which correspond to the three major areas of concern in the design of a post tensioned member. Post tensioning in buildings is not limited to floor slabs. It is based on data and knowledge considered to be true and accurate and is offered for consideration, investigation and verification by the user, but we do not warrant the results to be obtained. How to create a concrete slab using the posttensioning method. Developers, architects, engineers, contractors, educators and.
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