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. Specialised post tensioning flooring systems construction. The example presented here is for twoway posttensioned design. The tensile face indicates what portion of the beam requires reinforcing for strength. In the design section they have started from the very basics so that even a new comer will be able to understand without any difficulty. 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. Page 2 of slab post tensioning technical document system main features the advantages of the technique of slab post tensioning are several and clear. When zd is determined, the prestressing force required to balance an. Notice the assumptions required for the post tensioned design fig. The choice of concrete mix and curing methods along with quality workmanship also play a key role.
Cables are arranged as indicated by the engineer and chaired to run through the center of the slab. Post tensioned pt concrete floors are now widely used in the uk, particularly for highrise buildings. Tributary slab widths for equivalent frames aalami, b. Longer spans can be achieved due to prestress, which can also be used to counteract deflections. Structural calculations for posttensioned flat slab.
Because this course is intended to illustrate simplified analysis methods, we will use the efm exclusively. 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. Figure s42 three dimensional view of the post tensioned slab and its support arrangement s5 loading assumptions and values from the design criteria, the post tensioned slab is designed for a uniformly distributed superimposed dead load of 3. When moment is drawn on the tension side, the diagram matches the general drape of the tendons. Pre tensioning is accomplished by stressing wires or strands, called tendons, to predetermined. Posttensioned pt slabs are typically flat slabs, band beam and slabs or ribbed slabs. To get the excel sheet join as loving fansub member to this channel. Framing dead load selfweight superrimposed dead load 25 psf partitions, me, misc. Difference between pre tensioning and post tensioning. Twoway posttensioned design amsysco post tensioning. Economically design post tensioned and reinforced concrete floors including slabs, mats, and rafts, with exceptional visibility into compliance, efficiency, and practicality. Tensioning building structures march 12, 2020 2020 educode las vegas. Crack free performance vsl post tensioning axially compresses the concrete slab to counteract tensile stresses which.
Recommended practice for precast posttensioned segmental. Tensioning force transfer by steelconcrete bond force transfer at end anchor strain compatibility and force equilibrium. Anchorages provide for the safe introduction of post tensioning forces into the concrete. 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. Pretensioning and posttensioning in prestressed concrete. A slab strip of unit width is analysed using simple beam theory. Lin in the early 1960s and extended to nonprismatic members by the author, has led to increased application of post tensioning in building construction. The company helps its partners design and build more imaginative, efficient and durable structures. For general design philosophy and analysis of post tensioned concrete, the reader should refer to pdhonline course s127. M ed is that part of the unbalanced slab bending moments that is transferred into the column at the support. In pt design, it is preferable to draw moment diagrams to the tensile face of the concrete section. Usually a sign in the garage or stamp in the slab will indicate if your home has a post tension slab. The following example illustrates the design methods presented in aci 31805 and ibc 2003.
The execution of the design will be explained with reference. Consider all major aspects of slab design, including service, ductility, and strength limit states, punching shear requirements, longterm deflections, and walking vibration. Uniformthickness slabs are typically about 9 inches thick throughout, except at the. Part three continues with the study of twoway, post tensioned slab systems, including. Pdf new methods in efficient posttensioned slab design using. The design moment of the slab is modified for each design section to include the twisting moment of the same section woodarmer approximation. Oneway slabs normally design as a beam with cables running in the direction of the span at uniform centres.
Post tension slab working principle, components and. 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. Stronger, more efficient floor slab design creates longer spans and. Posttensioned concrete design spreadsheet program a pdh. Fundamentals of posttensioned concrete design for buildings part one a suncam online continuing education course. This course is intended to be an introductory course for structural engineers new to post tensioned. Tendon profile of a continuous post tensioned beam. It provides an architect the freedom to work freely with his designs. Pre tensioning is accomplished by stressing wires or. Precast post tensioned 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 are intrinsically waterproof and. Tensioning building structures miroslav vejvoda, p. We therefore apologize for the odd lapse into commercialism.
Commercial opportunities ccl post tensioning results in thinner concrete slabs. The design steps for a post tensioned composite bridge girder were prepared with the help of several sample design calculation demonstrated. When a concrete slab is stressed by the post tensioning method, it means the steel is being tensioned and the concrete is being compressed. Ccl posttensioned slabs can bring unique freedom over conventional building methods. General overview of posttensioned concrete design pdh online. Pre tensioning can be further classified into two categories such as linear pre tensioning and circular pre tensioning.
Post tensioning tendon installation and grouting manual fhwa. General principales local zone design general zone design. Design of posttensioned slabs posttensioning institute. Post tensioning is a method of reinforcing strengthening concrete or other materials with highstrength steel strands or bars, typically referred to as tendons. Five underlying features of post tensioned construction allow greater flexibility in reinforcement layout.
Design method may not be used for twoway, posttensioned slab systems. Post tensioned foundations can be used for these types of soils by using other rational design methods. Our future vision pti envisions a future in which post tensioning is the first choice for reinforcing all structures. The vsl post tensioned concrete slab on grade is cast in very large areas, often exceeding 2,500m 2 with no joints. Post tensioned concrete foundations designed by thi s standard generally meet the requirements for plain concrete specified in chapter of aci 31814 14 1. The default load combinations for post tensioning are defined in the following sections. Post tension design of slab there is document post tension design of slab available here for reading and downloading. Stronger, more efficient floor slab design creates longer spans and reduces the need for columns within the structure. 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.
Tn342 design example 2way mondada 093090 adapt corporation. Thanks to lift slabs 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. Jun 04, 2019 basic load balancing, introduced by t. Post tension slab advantages and disadvantages of post. Ccl is an expert in post tensioned and pre tensioned concrete technology and is the number one supplier of prestressed concrete solutions in buildings. 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. Structural calculations for posttensioned beam and oneway. What is post tensioning introduction post tensioning is a method of producing prestressed concrete, masonry and other structural elements. From the design criteria, the posttensioned slab is designed for a uniformly distributed superimposed dead load of 3. The recommendations derived from these and other studies vary from extremely light to extremely heavy. What is posttensioning introduction post tensioning is a method of producing prestressed concrete, masonry and other structural elements. Pretensioning and posttensioning in prestressed concrete design.
General overview of post tensioned concrete design. Posttensioned tendons are stressed after concrete is cast and hardened. Sep 09, 2016 course study on post tension slab design. Schematic comparing a conventially reinforced concrete member to a post tensioned membaer. Unless otherwise noted, all referenced table, figure, and equation numbers are from these books. The prestressed concrete design of a structure is influenced by either of the two processes, pre tensioning, and post tensioning. These methods are generally adopted in the making of psc girders, sleepers etc.
Typical applications of post tensioned slabs as already mentioned, this report is concerned exclusively with post tensioned slab structures. 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. Sarkisian and others published new methods in efficient posttensioned slab design using topology optimization. Posttension flat slab design example free download as pdf file. These foundations will typically contain less reinforcement prestressed and. Construction of posttensioned slabs on grade is very similar to using reinforcing steel, except for the tensioning step. Design floors and foundations reliably and efficiently, saving time and money, and overcoming the most common concerns you face as a. Use the download button below or simple online reader.
A combination of these values will determine the slab stresses at the time of stressing and at service loads. Post tensioning is a special form of prestressed concrete in which the prestressing tendons are stressed after the concrete is cast. Construction maintenance of post tensioned slab on ground. Nevertheless, it may be pointed out here that post tensioning can also be of.
Design elevated concrete slabs with or without post tensioning. Tributaries used when computing average precompression. Twoway pt slab design tutorial with adaptfloor pro. Difference between pretensioning and posttensioning. Fundamentals of post tensioned design for buildings. Design method may not be used for twoway, post tensioned slab systems. In the general case, the design moments used for the. Pt slabs offer the thinnest slab type, as concrete is worked to its strengths, mostly being kept in compression. Post tensioned slabs advantages the primary reason for the initial economy of post tensioned industrial floors is the reduced thickness of the concrete slab, permitted because of the compressive stress induced in the concrete by the post tensioning tendons. Achievement of this objective depends upon careful design, detailing and construction. In any span, the max cable sag, zd depends on the concrete cover requirements and the tendon dimensions. Post tensioning for twoway flat plate construction figure 2. Pre tensioning and post tensioning both methods are used under prestressing process which has few edges over the orthodox nonstressed structures like greater span to depth ratio, higher moment and shear capacity. This hybridisation helps achieve the formation of a much thinner slab with a longer span devoid of any columnfree spaces.
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. Nov 25, 2008 post tensioning is done onsite by installing post tensioning tendons within the concrete formwork in a manner similar to installing rebar. A more detailed guide to the design of pt floors can be found in the concrete societys technical report 43 tr43. Post tensioned slabs can be designed to be crack free and therefore waterproof slabs are possible. Fundamentals of posttensioned concrete design for buildings part one. Fundamentals of posttensioned concrete design for buildings. This article provides information on how to scheme a pt slab and how the use of post tensioning affects the rest of the structure. Post tensioning utilizes high quality high strength steel such that 1 kg of post tensioning strand may replace 3 or 4 kg of ordinary nonprestressed reinforcement. The file extension pdf and ranks to the documents category. Course content this spreadsheet program provides for the design and analysis of post tensioned concrete oneway beam and slab systems and twoway flat plate slab systems. For residential construction, tendons at 48 inches on center are common. 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. Tension concrete compressed shorter than it wants to be.
Chapter 9 design of post tensioned slabs onground, p. Banded tendons when designing twoway, post tensioned slab systems, in addition to the code. Two examples, one of a flat slab and one of a foundation raft, illustrate the design of these structures and the application of the present recommendations. Approved by the former fip commission 3 practical design and the fip council, it is hoped that these recommendations will facilitate the correct design of post tensioned slabs and. 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. In certain applications, slabs in the order of 10,000m 2 have been constructed without movement joints.
The loadbalancing method did away with the complexity of post tensioning design, which hindered its widespread adoption by structural engineers. Experienced specialty contractors and engineers have the knowhow to develop and execute repairs of unbonded post tensioning tendons, make modifications to existing unbonded post tensioned structures. Posttension basics how posttensioned slabs are built. Ribbed slabs there are two basic types of post tensioned residential slabs. In design examples they have covered all types of structures where pt is used including seismic diaphragm, slabs on grade and external post tensioning. The term prestressing is used to describe the process of introducing internal forces or stress into a concrete or masonry element during the construction process in order to.
For post tensioned concrete design, the user can specify the prestressing load pt by providing the tendon profile. Aalami a must have reference book for engineers, students, contractors, building officials, and researchers. Developers, architects, engineers, contractors, educators and. 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. Post tensioning in buildings is not limited to floor slabs.
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