Post tensioning tendon installation and grouting manual fhwa. What is the difference between normal slab and post. Commercial opportunities ccl posttensioning results in thinner concrete slabs. Post tension slab advantages and disadvantages of post. The program is divided into three separate screens, which correspond to the three major areas of concern in the design of a posttensioned member.
A 2 2area 2 a c 2 2 posttensioned 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. Stronger, more efficient floor slab design creates longer spans and reduces the need for columns within the structure. Analysis and design of rcc and posttensioned flat slabs considering seismic effect. Usually a sign in the garage or stamp in the slab will indicate if. Developers, architects, engineers, contractors, educators and. Originally post tensioned, twoway slab framing systems were constructed with column and. Us posttensioning industry owes its existence to liftslab construction first liftslab 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, liftslab companies changed to posttensioned slabs.
General principales local zone design general zone design. Part three continues with the study of twoway, posttensioned slab systems, including. In this free webinar dirk bondy and bryan allred discusses the latest edition of their book, posttensioned concrete principles and practice. The pti design procedure is used to design a slabon grade foundation that will respond elastically to forces the foundation is exposed to including those that are the consequence of soil pressure and soil deformation. Construction of posttensioned slabs on grade is very similar to using reinforcing steel, except for the tensioning step. Twoway posttensioned design amsysco post tensioning. Pdf analysis and design of rcc and posttensioned flat. Posttensioning of foundations, transfer beams and plates, posttensioned masonry and the combination of precast elements with castinplace concrete by means of posttensioning offer other interesting opportunities. This location is typically congested with tendons near the top of the slab and shooting pins may cause damage to. Tensioned bonded strands bonded tendons unbonded tendons internal internal external. Posttensioned concrete is accomplished by tensioning high strength steel cables within the concrete mass. This method is achieved in a process where metal or plastic tubes which contain loose tensioning cables or rods are cast into the concrete. Posttensioned concrete design spreadsheet program a pdh.
Originally posttensioned, twoway slab framing systems were constructed with column and middle strips, similar to those used in conventionally reinforced twoway slabs. 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. The design is based on hong kong building code hkcop 2004 and its amendment of june 2007. 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. Structural calculations for posttensioned flat 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.
Csi etabs 2016flat slab design, strip design and punching shear. Posttensioning allows bridges to be built to very demanding geometry requirements, including complex curves, variable superelevation and significant grade changes. Tributary slab widths for equivalent frames aalami, b. 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 posttensioned together. Framing dead load selfweight superrimposed dead load 25 psf partitions, me, misc. Five underlying features of posttensioned construction allow greater flexibility in reinforcement layout. Pdf nowadays, design of modern an architectural building structures requires the use of slender and free from numerous supports slabs. In simple span beams the primary post tensioning pt moments induced by the prestressing force are. A 5inch posttensioned slab can handle up to 5,000 pounds, and a typical 9inchthick slab will bear a concentrated 9,000pound load. The thickness of a twoway, posttensioned slab for typical hotel. 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. Pdf the posttensioning method is now a days increasing widely, due to its application. Pdf posttensioned concrete longspan slabs in projects of.
Posttensioning also allows extremely long span bridges to be. Posttension basics how posttensioned slabs are built. Posttensioning for twoway flat plate construction figure 2. In posttensioned floor slab construction, the placement of posttensioning tendons and associated nonprestressed reinforcement does not strictly follow the practice of nonprestressed slabs.
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. 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. When planning for point loads, a safe rule of thumb is to figure on 1,000 pounds per inch of slab thickness. Guidelines for the design of posttensioned floors by bijan o. Stronger, more efficient floor slab design creates longer spans and. Fundamentals of posttensioned concrete design for buildings part one. This report presents the structural engineering calculations of a posttensioned floor using parallel beams and oneway slab construction. Demolition of posttensioned concrete structures presents the contractor with unique issues. If we take as an example a car parking, we can see that, in the case of simply reinforced concrete slab, the structure is made of a forest of pillars, with floor thickness considerably high. Fundamentals of posttensioned concrete design for buildings part one a. However, because the continuous twoway tendons had to be placed in a draped parabolic profile near the top of. The purpose of this publication is to widen the understanding of posttensioned floor construction and show the considerable benefits which include minimum storey heights, rapid construction, economy, maximum design flexibility, minimum number of columns, optimum. Posttensioned general principales local zone design general zone design examples from pratice published by vsl international ltd. Aalami a must have reference book for engineers, students, contractors, building officials, and researchers.
Post tensioning in buildings is not limited to floor slabs. 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. Posttensioning in buildings is not limited to floor slabs. Pti 3 structural material types structural steel prestressed concrete reinforced concrete pre. A normal slab is basically a rcc reinforce cement concrete slab where as a post tentioned slab is the psc prestressed concret slab. This hybridisation helps achieve the formation of a much thinner slab with a longer span devoid of any columnfree spaces.
Pt slabs offer the thinnest slab type, as concrete is worked to its strengths, mostly being kept in compression. Longer spans can be achieved due to prestress, which can also be used to counteract deflections. Posttensioning institutes design of posttensioned slabsonground, pti design procedure 3rd edition. Slab posttensioning systems page 5 38 reinforcing savings as steel and concrete increase in pricing, the savings with a post tensioned slab will increase, because the quantity of steel and concrete required for a posttensioned slab is less than for a conventionally reinforced foundation. This spreadsheet program provides for the design and analysis of posttensioned concrete oneway beam and slab systems and twoway flat plate slab systems. Many times inexperienced contractors may drill or shoot column collars into concrete on top of the slab. Members of the institute include major posttensioning material fabricators in the u. Members of the institute include major post tensioning material fabricators in the u. General overview of posttensioned concrete design instructor. Fundamentals of posttensioned concrete design for buildings. For residential construction, tendons at 48 inches on center are common.
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. 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. Tensioning building structures march 12, 2020 2020 educode las vegas. The advantages of the technique of slab posttensioning are several and clear. Cables are arranged as indicated by the engineer and chaired to run through the center of the slab. Post tension slab working principle, components and.
Now optimum efficiency is obtained because the posttensioned reinforcing is located in the tension zones, the concrete is being compressed, and the posttensioned reinforcing is creating an uplift force in the middle of the spans where it is needed the most. Ccl posttensioned slabs can bring unique freedom over conventional building methods. At the same time, the post tensioning selected was not to be less than the value necessary for lightly reinforced slabs to meet temperature and shrinkage. Posttensioned buildings design and construction bijan o. For economical design of similar structures a smaller slab thickness leading to values between 60% to 80% of balanced selfweight is generally selected. 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. The execution of the design will be explained with reference. Horizontal posttensioned connections for precast concrete. Pdf prestressed and posttensioned concrete yatniel. Posttensioning concrete increases the many benefits associated with a concrete framed building.