Post tensioned suspended concrete slabs are designed utilising flat ducts with end anchorages containing up to 5 strand. Post tensioned slab drawing tips was discussed in this topic. Studies have shown that the major costs over the life of a structure involve joint maintenance. Posttensioning for twoway flat plate construction figure 2. Posttensioned slabs use high strength tensioned steel strands to compress the slabs, keeping the majority of the concrete in compression. Hurd new manual covers the proper installation and stressing of post tensioning systems for light commercial and residential slabs on grade the new post tensioning institute manual includes plans and cross sections for both ribbed and uniformthickness slabs. The largest post tensioned slab on grade made by vsl without expansion joints covered the area of 30,000 square metres. Prestressed concrete is a form of concrete used in construction. Shortening crack mitigation crack evaluation tn451010616. Construction of posttensioned slabs on grade is equivalent to applying reinforcing steel, with the exception of the tensioning step. The design steps for a post tensioned composite bridge girder were prepared with the help of several sample design calculation demonstrated. Information on constructing posttensioned slabs on grade.
The post tensioned slab is thinner in comparison with the traditionally reinforced slabs and saves construction time, because smaller amounts of concrete are laid in larger areas per day, often round about 2,500 square metres. Cracking in groundsupported posttensioned slabs on expansive soils by ken bondy1. A groundsupported posttensioned slab acts as a buffer which. Posttensioned, belowgrade concrete foundation system. The strands are stressed and anchored using wedge grips, the duct is then pressure grouted so that the strand are bonded to the surrounding concrete. Several methods exist for prestressing concrete, with posttensioning being a very common one. The design steps for a posttensioned composite bridge girder were prepared with the help of several sample design calculation demonstrated. Posttensioning is an active rather than passive form of reinforcing. May 14, 2020 a posttension slab is a slab of concrete that has been prestressed using a specific method to increase the strength of the concrete. Post tensioned concrete is a variant of prestressed concrete where the tendons are tensioned after the surrounding concrete structure has been cast 25 the tendons are not placed in direct contact with the concrete, but are encapsulated within a protective sleeve or duct which is either cast into the concrete structure or placed adjacent to it. Posttensioned slabs are usually used for long spans andor high live loads where the control of deflections assumes a significant role. I too, was looking for the best solution for my home. For general design philosophy and analysis of post tensioned concrete, the reader should refer to pdhonline course s127. We will group the cables and space them throughout a slab, just as we would an elevated slab.
Standard requirements for design and analysis of shallow posttensioned concrete foundations on expansive soils. This slab will be modeled as a 2delement, allowing the analysis to be run in a general xyz environment. Hurd new manual covers the proper installation and stressing of posttensioning systems for light commercial and residential slabs on grade the new posttensioning institute manual includes plans and cross sections for both ribbed and uniformthickness slabs. The original installer of the post tension strands came out and repaired it under the supervision of the original engineer. Structural engineering continuing education for engineers. Posttension slabs on grade, policy phoenix, arizona. Some foundations used for light buildings on shrinkswell soils. Heavyduty posttensioned concrete girder that supports a. The placing of cables is done according to the suggestions provided by the engineer and managed to run through the center of the slab. A 5inch posttensioned slab can handle up to 5,000 pounds, and a typical 9inchthick slab will bear a concentrated 9,000pound load. After the concrete is poured, but before it permanently sets, the tendons are tightened to apply compression on the slab. Posttensioning is a method of reinforcing strengthening concrete or other materials with highstrength steel strands or bars, typically referred to as tendons. Post tensioned slab drawing reading tips civil click. We had a tenant fit out project in a cheap, junky strip mall where the very unskilled gc accidentally cut through multiple posttension strands in the foundation slab.
Our awardwinning work encompasses building, energy, civilinfrastructure, and sciencedefense projects in the united states, canada, and more than thirty additional countries. Posttensioned slabs use highstrength tensioned steel strands to compress the slabs, keeping the majority of the concrete in compression. The advantages of posttensioning for industrial floors are. Cracking in groundsupported post tensioned slabs on.
The present study focuses on posttensioned flat slab systems with respect to strength. The designs were analysed using adapt builder software with different panel sizes. April 25, 2016 the high cost of a lack of education, theodore neff. 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. Standard requirements for design and analysis of shallow post tensioned concrete foundations on expansive soils. Posttensioning institute events convention technical sessions. A 5inch post tensioned slab can handle up to 5,000 pounds, and a typical 9inchthick slab will bear a concentrated 9,000pound load. The extent of the restraint cracking in a posttensioned member depends on a number of factors, including the stiffness of the supports.
These strands or cables are also referred to as tendons. The parametric study of the post tensioned flat slab by varying the span by 0. Posttensioned slab on grade is more durable and economical than conventional slab reinforcement. Usually a sign in the garage or stamp in the slab will indicate if your home has a post tension slab. Post tensioning imparts an internal compressive force into the 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. 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. The foundation includes a posttensioned concrete floor slab formed on the soil base of a below grade excavation. Slabongrade and posttensioned slab software adaptsog. Reduced maintenance the use of fewer or even no joints significantly reduces the need for future maintenance. Ground flood is ground bearing and was cast in reinforced concrete. 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. Carboneco is a software package that gives owners an accurate assessment of the. Posttensioning concrete increases the many benefits associated with a concrete framed building.
Slab on grade post tensioning systems tendon systems. For general design philosophy and analysis of posttensioned concrete, the reader should refer to pdhonline course s127. The concrete is very strong in compression but lacks strength in tension. As we all know, autodesk revit doesnt provide posttensioned concrete modeling.
Prestress has a favourable influence, balancing a part of the. The advantages of post tensioning for industrial floors are. The course will address the vibration evaluation and design of ever more emerging open space floor designs of often thin slabs supported on nonorthogonal supports for aspirational support layouts. Post tension concrete slab in this example post tensioned cables are introduced on a concrete slab. Construction maintenance of post tensioned slab on ground. The facade is shaped by posttensioned concrete slab floor plates, whose curvature is a response to structural optimization of cantilevered distances. The gbs will consist of a reinforced and posttensioned concrete. Fundamentals of post tensioned concrete post tensioned. High density polyethylene sheathing pt coating 7 wire steel strand anchor 2. Posttensioned slabsonground provide a costefficient, highperformance solution for problems associated with groundsupported residential foundations on.
Part one gives a brief historical background and posttensioned members are differentiated from pretensioned members. Tennis court how to create your backyard play court the. April 28, 2015 structural design of posttensioned slabsonground, don illingworth. Concrete foundation walls are formed on the perimeter of the post tensioned floor slab. The benefits of faster construction schedules while decreasing the quantity of concrete and rebar saves money posttensioning imparts an internal compressive force into the concrete. A below grade, posttensioned concrete foundation system for use in the construction of residential dwellings and other structures is described. With a posttensioned slab, the costs of joint and crack repairs are reduced as too is the damage to.
In the succeeding years numerous posttensioned slabs were designed and constructed in. In part a a posttensioned member on very flexible supports shortens under the precompression, forcing the supports to follow the members moment. High tension steel tendons enable slab foundations to withstand the stresses of expansive and compressive soil conditions that are prevalent in texas. Flexural testing of the posttensioned twoway slabs was conducted to.
Posttensioning is a method of reinforcing strengthening a concrete slab on grade with high strength steel strands. Prestress concrete unbonded posttensioning youtube. Posttensioned slabs on grade beyond the build stewart. Inserting tendons in the concrete is a very tedious and timeconsuming procedure, even if we do it just as 2d annotation. Part one should be taken before parts two and three. Although some posttensioned slab structures had been constructed in europe quite early on, the real development took place in the usa and australia. General overview of post tensioned concrete design. For a lightly loaded industrial floor, the slab is placed 4 inches thick with tendons in both directions at 2 to 5foot intervals. A post tension pt slabongrade sog foundation is based on a typical raft sog foundation with one major difference. Post tensioning concrete increases the many benefits associated with a concrete framed building. Post tensioning for twoway flat plate construction figure 2.
Tendon profile of a continuous post tensioned beam. Suspended floor slabs post tensioned suspended concrete. The original installer of the posttension strands came out and repaired it under the supervision of the original engineer. Freyssinet have recently been awarded further posttensioned floor slab contracts for wade deacon high school in. In addition, posttensioned concrete slabs with proper posttensioning show. The use of posttensioned solutions in building design presents, in many cases, important technical and economical advantages.
Posttensioned slabs on grade beyond the build stewartperry. This course is intended to be an introductory course for structural engineers new to posttensioned concrete design, and is a good refresher for experienced structural engineers. In a posttensioned slab on grade, a grid of high strength posttensioning tendons replaces the weldedwire fabric or conventional rebar normally used. Posttensioning is a method of reinforcing strengthening concrete or other materials with high strength steel strands or bars, typically referred to as tendons.
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 clear spans, jointfree, crackfree. In order to take into account longterm losses, the user would estimate these losses and simply include. The underlying reasons and preference in selection of posttensioned floors in high seismic or wind. When concrete is post tensioned, internal forces are introduced into the concrete element which place the concrete in. Post tensioning is an active rather than passive form of reinforcing. The posttensioned slab is thinner in comparison with the traditionally reinforced slabs and saves construction time, because smaller amounts of concrete are laid in larger areas per day, often round about 2,500 square metres.
The foundation includes a post tensioned concrete floor slab formed on the soil base of a below grade excavation. The condominium building floors will have 8 inch thick post tensioned concrete slabs. Analytical model for deflections of bonded posttensioned concrete. The underlying reasons and preference in selection of posttensioned floors in high seismic or wind regions will be explained in detail.
The benefits of faster construction schedules while decreasing the quantity of concrete and rebar saves money. Posttensioned concrete slabs augi the worlds largest. Building better posttensioned slabs concrete construction. Have you ever cut a posttensioned slab forum archinect. The cost of a regulationsize posttensioned concrete tennis court with a cushioned surface can be double that of an equivalent asphalt court. Pt slabs offer the thinnest slab type, as concrete is worked to its strengths, mostly being kept in compression. The parametric study of the posttensioned flat slab by varying the span by 0. An installation, stressing and post construction activities such as.
Post tension pt slab there has recently been a lot of discussion regarding to a post tension, or pt slab on grade and a pier and beam foundation. 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. Dec 25, 2003 a below grade, post tensioned concrete foundation system for use in the construction of residential dwellings and other structures is described. When planning for point loads, a safe rule of thumb is to figure on 1,000 pounds per inch of slab thickness. Longer spans can be achieved due to prestress, which can also be used to counteract deflections. Post tensioned slab on grade is more durable and economical than conventional slab reinforcement. Adaptsog software for the design of posttensioned slabs on grade foundations on expansive and compressible soils. Before a posttension slab is poured, high strength steel strands or cables, called tendons, are laid in a tight grid. It is substantially prestressed during production, in a manner that strengthens it against tensile forces which will exist when in service 35 this compression is produced by the tensioning of high strength tendons located within or adjacent to the concrete and is done to improve the performance of the concrete in service. We had a tenant fit out project in a cheap, junky strip mall where the very unskilled gc accidentally cut through multiple post tension strands in the foundation slab. Structural reliability ccl post tensioned slabs show reduced cracking. Large tolerance value can lead to inaccurate results, and the tolerance was set to 0. An animation movie which illustrates almost all the activities related to mono strand unbonded post tensioning system.
Posttensioning institutes design of posttensioned slabsonground, pti design procedure 3rd edition. The largest posttensioned slab on grade made by vsl without expansion joints covered the area of 30,000 square metres. Concrete foundation walls are formed on the perimeter of the posttensioned floor slab. Sgh is a national engineering firm that designs, investigates, and rehabilitates structures, building enclosures, and materials. Stiffened slab on grade elevated structural slab on piers stiffened slab on grade and on piers thin post tensioned slab figure 1. For residential construction, tendons at 48 inches on center are mostly found. Estimating software, free construction estimating software excel download, free. Post tensioning design and construction administration and.
Post tensioning design and construction administration. 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. Grade the lot for positive drainage away from the foundation during and afterconstruction. After the concrete cures, the cables are tensioned causing the concrete slab to slightly bow upward in the middle making it stronger and able to hold more weight. Tendon new educational free software for posttensioned structures. Software for plates and shells, pineridge press, swansea, uk, 1984.
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