This location is typically congested with tendons near the top of the slab and shooting pins may cause damage to the tendons. The main objective of the bulletin is to point out the benefits of using post tensioning for. Jan 24, 2015 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 as post tension slab. Warehouses, distribution centres, container terminals, airports, pavements, residential slabs and recreational slabs for tennis courts and skating rinks are common applications. 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. Bridges, posttensioning, tendons, grout, grouting, strands, bars, protection, ducts, inlets, outlets, tests, prestressed concrete, pretensioning, stressing. Dec 24, 2014 objectives the objective of the present report is to summarize the experience available today in the field of post tensioning in building construction and in particular to discuss the design and construction of post tensioned slab structures, especially post tensioned flat slabs a detailed explanation will be given of the checks to be carried. Market for post tensioning tendons over 40% of all pt tendons sold in the usa are for residential foundations. Various notations used in this chapter are listed in table 11. Construction maintenance of post tensioned slab on ground.
Ptg supply and advise on the latest techniques, designs and practices from around the globe and undertake a number of services. Martins university of algarve, portugal summary the specification of maximum span to thickness ratios allows the. Check slab stresses separately calculate the maximum positive and negative moments in the frame for the dead, live, and balancing loads. Post tension slabs superior foundations services jackson. There are several problems that can occur with post tensioning components in balcony and garage slabs in service.
A subsequent report established the feasibility of using post tensioning in slab onground construction and verified many of the brab assumptions. Post tensioning in concrete slab benefits and advantages. Post tensioned wafflejoist slab constriction1 where concrete is relatively expensive, spans are generous, and it is not critical to select the smallest floor thickness, a post tensioned waffle slab construction is likely to be the economical alternative. As we all know, autodesk revit doesnt provide posttensioned concrete modeling. Posttensioned pt slabs are typically flat slabs, band beam and slabs or ribbed slabs. Lightly reinforced slabs on stable soilsthese slabs may be. Experimental and numerical assessment of bonded and unbonded post tensioned concrete members article pdf available in aci structural journal 1126.
This hybridisation helps achieve the formation of a much thinner slab with a longer span devoid of any columnfree spaces. Posttension basics how posttensioned slabs are built. Post tensioning is a method of reinforcing strengthening concrete or other materials with highstrength steel strands rebars, typically referred to as tendons. Do not alter the drainage pattern of the site provide a minimum of 3%. Post tensioning in buildings is not limited to floor slabs. Post tensioned pt concrete floors are now widely used in the uk, particularly for highrise buildings. Originally post tensioned, twoway slab framing systems were constructed with column and. In addition, both the international building codeand the uniform building codeprovide design methods for determining the capacity of a post tensioned slab to. For residential construction, tendons at 48 inches on center are common. The behaviour and response of flat slab and post tensioned flat slab during earthquake is an important aspect which needs to be explored.
This is part three of a threepart course that covers the fundamentals of post tensioned concrete for building structures using unbonded tendons. Ppt posttensioning powerpoint presentation free to. There is a danger that if a nonprofessional cuts or drills into the slab, that they may sever, cut or damage the post tension cable. Fundamentals of posttensioned concrete design for buildings part one. General overview of post tensioned concrete design instructor. In posttensioned floor slab construction, the placement of postten sioning tendons and associated nonprestressed reinforcement does not strictly follow the. Post tensioned concrete slabs have been used since the 1930s, and have become commonplace in the last 30 years. This slab is much stronger as well as more durable than the normal concrete slabs. Standard requirements for design and analysis of shallow post tensioned concrete. 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.
Experimental investigation on the effect of impact loading. Abstract this paper describes an experimental study of the punching resistance of unbonded post tensioned flat slabs supported on edge. Post tension slab advantages and disadvantages of post. Pdf experimental and numerical assessment of bonded and. 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.
Remove concrete to make the opening, using a disc cutter to cut through tendons. Fundamentals of post tensioned concrete design for buildings part one a suncam online continuing education course. Park plaza post tensioned parking structure demolition. Fundamentals of posttensioned concrete design for buildings. In the succeeding years numerous post tensioned slabs were designed and constructed in conjunction with the lift slab method. Almeida tecbnical university, lisbon, portugal, julio a. Post tensioning in buildings foreword working party wp1. Longer spans can be achieved due to prestress, which can also be used to counteract deflections. The advantages of the technique of slab post tensioning are several and clear.
In this free webinar dirk bondy and bryan allred discusses the latest edition of their book, post tensioned concrete principles and practice. Originally post tensioned, twoway slab framing systems were constructed with column and middle strips, similar to those used in conventionally reinforced twoway slabs. This article will explore features of posttensioned concrete. What is the difference between normal slab and post. Follow the slab strengthening plan, including any provisions that need to be implemented during the cutting operations. However, because the continuous twoway tendons had to be placed in a draped parabolic profile near the top of. A normal slab is basically a rcc reinforce cement concrete slab where as a post tentioned slab is the psc prestressed concret slab. Posttensioning institutes design of posttensioned slabsonground, pti design procedure 3rd edition. Detension and reanchor those tendons at the perimeter of the intended opening. Posttension basics how posttensioned slabs are built the.
Post tensioning concrete increases the many benefits associated with a concrete framed building. 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 advantages are many, when compared to non post tensioned systems, and include thinner slabs, lighter structures, lower floortofloor heights, less mild reinforcing steel, and less short and long term deflections. It has the following benefits as compared to unbonded post tensioning. 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.
Inserting tendons in the concrete is a very tedious and timeconsuming procedure, even if we do it just as 2d annotation. 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. Posttensioned concrete slabs augi the worlds largest. The advantages of post tensioned structures a technique that allows long beams lengths to be achieved reduces deflections and allows highspan depth ratios improves durability by the reduction or elimination of cracking more efficient utilization of steel and concrete material. Finally, an example of a flat slab floor system is presented to illustrate the practice.
Posttensioned concrete haunched slab bridge standards. This type of deck construction is highly specialized and should be carried out only by skilled. Appleton tecbnical university, lisbon, portugal, carlos a. General after making an initial selection of the slab thickness, the second step in slab design is to determine the amount and distribution of prestress. Eliminate joints joints in reinforced concrete slabs on. Posttensioned concrete design spreadsheet program a pdh. Guidelines for the design of post tensioned floors by bijan o. Developers, architects, engineers, contractors, educators and. A combination of these values will determine the slab stresses at the time of stressing and.
This may weaken the structural strength of the slab. Rebar slabs may 03 2016 0 comments concrete, nishkian dean 0 reinforced concrete slabs have been used in buildings from the middle of the 19 th century. Post tensioning tendon installation and grouting manual fhwa. 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. Superior began their journey into the foundation repair business, only after they had mastered the post tension engineering process for new construction post tension slabs superior foundations services jackson, madison, brandon, flowood mississippi. Post tension slab working principle, components and. Several methods exist for prestressing concrete, with post tensioning being a very common one.
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. 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. Herein describes in detail the various aspects of the posttensioned concrete design procedure with the american code aci 31808 aci 2008. This article provides information on how to scheme a pt slab and how the use of post tensioning affects the rest of the structure. This technical note offers several views of post tensioned waffle slab constructions, and. 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. Apr 05, 2020 a post tension slab is a slab of concrete that has been prestressed using a specific method to increase the strength of the concrete. Part three continues with the study of twoway, post tensioned slab systems, including. A ccldesigned posttensioned slab can contain less concrete 20% 30%, less reinforcement and less complicated rebar shaping than conventional reinforced. Fundamentals of post tensioned design for buildings. A 5inch post tensioned slab can handle up to 5,000 pounds, and a typical 9inchthick slab will bear a concentrated 9,000pound load.
Construction of post tensioned slabs on grade is very similar to using reinforcing steel, except for the tensioning step. Post tension slabs answers to questions buyers ask. Brendon burley structural option post tensioned twoway slab load analysis when considering twoway slabs in a post tensioned system, it is important to perform an advanced analysis of the loads and their effects at different locations in the building. Balcony slabs in typical post tension buildings with balconies, the balcony slab. The execution of the design will be explained with reference to an example.
Post tensioning applications include office and apartment buildings, parking structures, slabs onground, bridges, sports stadiums, rock and soil anchors, and watertanks. Post tensioning terminology ptt november 20 page 8 of 33 backup bars for unbonded single strand tendons, minimum nonprestressed reinforcement parallel to slab edge used to resist tensile forces in the concrete caused by the applied prestressing force. What is the difference between normal slab and posttensioned. Fundamentals of post tensioned concrete design for buildings part one a.
Posttensioning software post tensioning software builder floor pro. Tn342 design example 2way mondada 093090 adapt corporation. Slab on grade the vsl post tensioning system is widely used in the construction of slabs on grade. 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. Many times inexperienced contractors may drill or shoot column collars into concrete on top of the slab. Aalami a must have reference book for engineers, students, contractors, building officials, and researchers. A psc is applied with a compressive stress on the cross section in advance before the application of loading on. 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. Before a post tension slab is poured, highstrength steel strands or cables, called tendons, are laid in a tight grid. However, should this happen, it can be repaired and even if not repaired, the slab may still function well. In any event, the maximum total length of posttensioned concrete slab bridges, without introducing a strand splice or interior span joints, is expected to be about 180 m 600. Bonded post tensioned concrete is the descriptive term for a method of applying compression after pouring concrete and the curing. Cables are arranged as indicated by the engineer and chaired to run through the center of the slab. Punching of reinforced and posttensioned concrete slab.
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. 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. For economical design of similar structures a smaller slab thickness leading to values between 60% to 80% of balanced selfweight is generally selected. Effective inspection and monitoring of posttensioned. Twoway slab systems twoway post tensioned slab systems have been widely used in building construction for many decades. For referencing to the pertinent sections of the aci code in this chapter, a prefix aci followed by the section number is used. Slab post tensioning 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 post tensioned slab is less than for. Balcony slabs in typical post tension buildings with balconies, the balcony slab is an extension of the concrete. Pt slabs offer the thinnest slab type, as concrete is worked to its strengths, mostly being kept in compression. Pdf the post tensioning method is now a days increasing widely, due to its application. Fundamentals of post tensioned concrete design for buildings part one. This spreadsheet program provides for the design and analysis of post tensioned concrete oneway beam and slab systems and twoway flat plate slab systems. Identify planned intersection locations of post tensioned tendons.
Load balancing is used, a portion of the load on slab is balanced by the transverse forces imposed by the draped. Request pdf punching of reinforced and posttensioned concrete slabcolumn connections data collected from shaketable tests of two, approximately scale, twostory flat plate frames using. In the succeeding years numerous posttensioned slabs were designed and constructed in conjunction with the lift slab method. The rc slab was a flat slab with a thickness of 320 mm, while the other two slabs were pt with a thickness of 250 mm.
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