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. 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. Kindle file format pti post tensioning manual 6th edition. General overview of posttensioned concrete design an. Once the concrete has gained strength to 2000 psi, typically within the 3 to 10 days recommended by pti, the tendons are stressed. Pdf post tensioned slab vsl report dec structural consultant.
Longer spans can be achieved due to prestress, which can also be used to counteract deflections. Lightly reinforced slabs on stable soilsthese slabs may be. 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. The following example illustrates the design methods presented in aci 31805 and ibc 2003. Tendons today are seven highstrength steel wires wound together and placed inside a plastic duct. Horizontal posttensioned connections for precast concrete. Shortening crack mitigation crack evaluation tn451010616. For posttensioned concrete design, the user can specify the prestressing load pt by providing the tendon profile. Posttensioning methods for reinforcing concrete the. The post tensioning institute pti design manual6 gives recommended spantothickness ratios for slabs and spantodepth ratios for beams. Without post tensioning, this building would be much. Pdf nowadays, design of modern an architectural building structures requires the use of slender and free from numerous supports slabs. The execution of the design will be explained with reference.
Post tensioned concrete is made by casting concrete that contains ducts through which tendons can be threaded. The tension in the tendons results in an equivalent compression in the concrete, which causes the member to shorten fig. Posttensioned concrete design spreadsheet program a pdh. I already ran the analysis in safe but i never actually drawn a post tension slab before i saw how detailing in safe is but it is not very much good. Post tensioning is used in this manner in millions of square feet of warehouse floors, sport courts, housing and specialized paving applications. In any event, the maximum total length of post tensioned concrete slab bridges, without introducing a strand splice or interior span joints, is expected to be about 180 m 600. This location is typically congested with tendons near the top of the slab and shooting pins may cause damage to. Usually a sign in the garage or stamp in the slab will indicate if your home has a post tension slab. The program is divided into three separate screens, which correspond to the three major areas of concern in the design of a post tensioned. Use the download button below or simple online reader. Even congested tendons can be routed around obstructions. Structural engineers design concrete slabs with post tension cables to obtain greater span lengths between supporting columns and to allow thinner slabs. Applications of sustainable posttensioned concrete slabs. In post tensioned construction, the tendons are stressed and anchored after the concrete member they are embedded in has developed sufficient strength fig.
An alternative is to cast the concrete around tendons that are greased or encased in a plastic sleeve. Experimental and numerical assessment of bonded and unbonded posttensioned concrete members article pdf available in aci structural journal 1126 november 2015 with 1,895 reads. Post tensioning is used for many reasons, including economy and building efficiency as well as the reduction of deflection and cracking it provides. Unless otherwise noted, all referenced table, figure, and equation numbers are from these books. Post tension design of slab there is document post tension design of slab available here for reading and downloading.
Posttensioning is used for the last decades for different concrete elements such as slabs, beams, walls and mat foundations. Post tensioned concrete design spreadsheet program. Post tension cables are steel wires inserted into plastic sheathing laid in place while pouring the concrete slab. As is wellknown, in this method of post tensioning the prestressing steel is placed in ducts, and after stressing is bonded to the surrounding concrete by grouting. 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.
Cables are arranged as indicated by the engineer and chaired to run through the center of the slab. In corrosive environments, stuffed and heatsealed tendons have the inherent shortcoming of either trapping or allowing access of corrosive substances in the oversized sheathing. If your location is an area with expansive soils, always assume the slab is post tensioned. Once the concrete is poured and sets, the cables are tensioned.
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. Post tensioned slabs are a great tool to help reduce joints and control cracks. Joints in reinforced concrete slabs on grade have long been a cause of cost. Tension concrete compressed shorter than it wants to be.
Different layouts of the prestressing tendons are used in construction of flat slab system, these such as5. Construction of post tensioned slabs on grade is very similar to using reinforcing steel, except for the tensioning step. What are the drawings presented for a post tensioned slab. But i have to first modify the pdf files to delete the title blocks etc project the guilty. In certain applications, slabs in the order of 10,000m 2 have been constructed without movement joints. Identifying problems with post tension concrete post tensioning is a technique for reinforcing concrete with steel cables, typically referred to as tendons. This method will be used exclusively in this course. Serviceability limit state 11 41 crack limitation 11 42. Post tensioned slabs use highstrength tensioned steel strands to compress the slabs, keeping the majority of the concrete in compression. Post tension slab advantages and disadvantages of post. What are the drawings presented for a posttensioned slab. Cover is determined from the requirements for corrosion protection, fire protection, and wear. 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. A post tension slab is a concrete slab or foundation that contains high tension cables running through the concrete to increase strength and reduce cracking typically in areas with poor soil conditions.
Posttension basics how posttensioned slabs are built. This building is a wonderful example of the advantages of post tensioned concrete in tall buildings. So this tool was designed for free download documents from the internet. Pdf posttensioned concrete longspan slabs in projects of. Allowable deflection limits refer to table 1 of the appendix. Post tension slab construction is common in areas with expansive soils. Guide for shoringreshoring of concrete multistory buildings. Pdf tr 43 posttensioned concrete floorsdesign handbook. Guide for shoringreshoring of concrete multistory buildings reported by aci committee 347 aci 347. 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.
Pt slabs offer the thinnest slab type, as concrete is worked to its strengths, mostly being kept in compression. Clean out of the footings after a rain is much faster and neater than rebar type foundations. Posttensioned concrete haunched slab bridge standards. Fundamentals of posttensioned concrete design for buildings. It provides methods for developing safe construction. Fundamentals of post tensioned concrete design for buildings part one fundamentals of post tensioned concrete design for buildings part one. Pre tensioning is accomplished by stressing wires or strands, called tendons, to predetermined amount by stretching them between two anchorages prior to placing concrete as shown in fig. Hazards of post tensioned concrete slabs safety toolbox. Pdf fundamentals of posttensioned concrete design for. 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. Analytical model for deflections of bonded posttensioned concrete. The vsl post tensioned concrete slab on grade is cast in very large areas, often exceeding 2,500m 2 with no joints. Post tensioning tendons, which are highstrength steel cables inside plastic sheathing, are positioned in the forms before the concrete is placed.
The default load combinations for posttensioning are defined in the following sections. For general design philosophy and analysis of posttensioned concrete, the reader should refer to pdhonline course s127. This spreadsheet program provides for the design and analysis of post tensioned concrete oneway beam and slab systems and twoway flat plate slab systems. Developers, architects, engineers, contractors, educators and.
Ccl posttensioning results in thinner concrete slabs making the. This course is intended to be an introductory course for structural engineers new to post tensioned concrete design, and is a good refresher for experienced structural engineers. Pre tensioning and posttensioning in prestressed concrete design pre tensioning in prestressed concrete. Posttensioning with or without bonding of tendons 3 1. This paper presents a finite element analysis approach to evaluate the flexural behavior of posttensioned twoway slabs depending on the. Fewer joints large concrete areas, such as tennis courts, parking lots. Posttensioned, reinforced concrete slab design software ram. It is the intent of this chapter to establish the practices and specific requirements of the structure and bridge division for the design and detailing of prestressed and posttensioned concrete members. Post tensioning is a technique for reinforcing concrete. Post tension slab eliminating cracks and joints in concrete. Fundamentals of posttensioned concrete design for buildings part one. Prestressed, pretensioned and posttensioned concrete. The file extension pdf and ranks to the documents category. What is the difference between pretension and post tension.
Unbonded post tensioning system technology in building. Ccl post tensioned slab systems can be integrated into any type of slab, including. Post tensioning in buildings is not limited to floor slabs. Post tensioning tendons, which are prestressing steel cables inside plastic ducts or sleeves, are.
This gives a very efficient structure which minimises material usages and decreases the economic span range when compared to reinforced concrete. Tensioning force transfer by steel concrete bond force transfer at end anchor strain compatibility and force equilibrium. Post tension slab working principle, components and. Post tensioning elevated concrete beams and slabs can result in thinner concrete sections andor longer spans between supports. Course content this spreadsheet program provides for the design and analysis of posttensioned concrete oneway beam and slab systems and twoway flat plate slab systems. Pdf experimental and numerical assessment of bonded and. Plans having prestressed concrete members shall include a table with top of slab elevations at the following points along centerline of beams. Post tensioning is simply a way to reinforce in a more active way. When the concrete has sufficient strength the tendons are tensioned by means of portable jacks. The course content is contained in the following pdf file. Many times inexperienced contractors may drill or shoot column collars into concrete on top of the slab.
Pdf prestressed and posttensioned concrete yatniel. Twoway posttensioned design amsysco post tensioning. Pre tensioning and post tensioning both method are used under prestressing process which have few edge over the orthodox nonstressed structures like more span to depth ration, higher moment and shear capacity. Shallow post tensioned concrete foundations are commonly used in single family and multiresidential, light commercial, and lowfamily rise commercial construction. This paper investigates the structural behaviour of pt twoway concrete slabs. Download free, highquality cad drawings, blocks and details of post tensioned concrete organized by masterformat.
Design floors and foundations reliably and efficiently, saving time and money, and overcoming the most common concerns you face as a designer. Pretensioning and posttensioning in prestressed concrete. This hybridisation helps achieve the formation of a much thinner slab with a longer span devoid of any columnfree spaces. About us we believe everything in the internet must be free. A residential posttensioned concrete slab will typically be 8 inches thick and use 3000 psi concrete. In castinplace posttensioned flat plate construction, the slab is restrained against vertical deformation at the support, and such a restraint causes secondary moments in the slab as well as secondary axial forces in the column, both of which should be considered in the design. Download tr 43 post tensioned concrete floorsdesign handbook. Pdf finite element modeling of posttensioned twoway.
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