In 1980 fip had published recommendations for the design of flat slabs in post tensioned concrete out of print already for many years. Unfortunately, specific design provisions for shear strength and flexural strength of unbonded prestressed slabs are not provided in the present aci code aci 31871. But while using this method more precautions has to be made for the shear and the deflection criteria for the slabs. The program is divided into three separate screens, which correspond to the three major areas of concern in the design of a post tensioned. The pti design procedure is used to design a slabon grade foundation that will respond. Part three continues with the study of twoway, post tensioned slab systems, including. 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 post tensioned design for buildings. 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. Part three is an exampleintensive course, with key concepts introduced along the way.
Indications are given concerning preliminary design and indirect control of deflections in posttensioned flat slabs. Posttension basics how posttensioned slabs are built. Jurgens his article presents a set of guidelines intended to t assist designers in routine post tensioning design. Where design requirements demand more reinforcement that is generally assigned to a typical interior waffle stem, solid strips along the lines of. Transmission forces reinforcement reinforcement transverse tension. Developers, architects, engineers, contractors, educators and. In post tensioned floor slab construction, the placement of post tensioning tendons and associated nonprestressed. Reinforced concrete design 1 design of slab examples. Brendon burley structural option post tensioned twoway slab figure 23 details of the twoway slab.
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. A more detailed guide to the design of pt floors can be found in the concrete societys technical report 43 tr43. Post tensioned pt concrete floors are now widely used in the uk, particularly for highrise buildings. Analysis of posttensioned flat slab by using safe shriraj s. Reinforced and posttensioned concrete slab design software. 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.
Tendon layout, including dimensions, which locates the tendons in the horizontal plane. This article will explore features of posttensioned concrete. 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. Pdf experimental and numerical assessment of bonded and. The file extension pdf and ranks to the documents category. Detail horizontal curvature of tendons at blockouts, openings and. In this video, he will describe his experiences at the site as. Cables are arranged as indicated by the engineer and chaired to run through the center of the slab. The advantages of the technique of slab post tensioning are several and clear. The idea of prestressed concrete has been around since the latter decades of the 19th century, but its use was limited by the quality of the materials at the time. Three post tensioned slabs with unbounded tendons were designed figures 4 and 5.
Pt slabs offer the thinnest slab type, as concrete is worked to its strengths, mostly being kept in compression. A design strip is a region assigned to a hypothetical support line that joins a line of columns and. Posttensioned twoway slab pennsylvania state university. Attempts were made to improve knowledge by in depth theoretical studies and experiments on posttensioned plates. Soils are wetter at slab edge than at any point inside. Users manual posttensioned concrete haunched slab bridges. Deflecuon limits prestressing in posttensioned slabs fundamentally influences the behaviour of the structure under service loads.
A normal slab is basically a rcc reinforce cement concrete slab where as a post tentioned slab is the psc prestressed concret slab. New developments in structural engineering and construction. When the concrete reaches a certain design strength, the cables are then tensioned to a pre. Post tension slab advantages and disadvantages of post. 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.
Post tension slab working principle, components and. Pdf prestressed and posttensioned concrete yatniel. The design steps for a two way post tensioned slab. Environmental impact assessment of post tensioned and conventional reinforced concrete slab design dane miller1, jeunghwan doh and tim peters2 1griffith school of engineering, griffith university, gold coast, australia 2adg engineering, gold coast, australia this research determines environmental advantages achievable through application of. This video tutorial is about pts post tension slab design which is trained by master of structural engineering mr. 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 post tensioned concrete members. Threedimensional 3d finite element software for the integrated analysis and design of concrete and posttensioned floor and foundation systems. University of houston master construction specifications insert project name ae project number.
It took until the 1920s and 30s for its materials development to progress to a level where prestressed concrete could be used with confidence. Model specification bonded and unbonded posttensioned. Post tensioned concrete is used more frequently today than in the past, and presents several hazards to firefighters. Pt slabs castinplace beams, slabs and columns liquid retaining and containment structures beams and design strips of post tensioned slabs xy and xz projections of design strips with post tensioned tendon safe and comprehensible fast and optimized design of. This is part three of a threepart course that covers the fundamentals of post tensioned concrete for building structures using unbonded tendons. The main objective of the bulletin is to point out the benefits of using post tensioning for. Design method may not be used for twoway, post tensioned slab systems. There are several problems that can occur with post tensioning components in balcony and garage slabs in service. Fundamentals of post tensioned concrete design for buildings part one a suncam online continuing education course. Twoway posttensioned design amsysco post tensioning.
Fundamentals of posttensioned concrete design for buildings part one. Longer spans can be achieved due to prestress, which can also be used to counteract deflections. The following example illustrates the design methods presented in aci 31805 and ibc 2003. 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. Guidelines for the design of post tensioned floors by bijan o. Post tensioned buildings design and construction bijan o. This lab manual was prepared with the help of the renowned text book design of prestressed concrete structures, 3rd edition by t. Post tensioned concrete is accomplished by tensioning high strength steel cables within the concrete mass. Gustaferro consulting engineer the consulting engineers group, inc. Post tensioned slabs use highstrength tensioned steel strands to compress the slabs, keeping the majority of the concrete in compression. University of houston master construction specifications. Load balancing is used, a portion of the load on slab is balanced by the transverse forces imposed by the draped.
Advantages of using post tensioning for your next slab onground project. 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. 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. This tension makes the concrete slab and foundation much stronger than concrete without reinforcement and helps reduce cracking. Actual losses, whether greater or smaller than computed values, have little effect on the design strength of the member but do affect service load conditions i. In this free webinar dirk bondy and bryan allred discusses the latest edition of their book, post tensioned concrete principles and practice 3rd edition as well as present the latest version.
Reports on an analysis of 18 full scale fire tests of concrete slabs and beams prestressed by post tensioning. Post tensioned slabs can be designed to be crack free and therefore waterproof slabs are possible. A psc is applied with a compressive stress on the cross section in advance before the application of loading on. The design of the post tension flat slab can be done by using load balancing. Gregory havel takes a look at this aspect of modern building construction. The commentary is provided to mention the considerations of the committee in developing the criteria. The behavior of post tensioned flat plates in the critical column area is of great concern to designers. Interior left, exterior right deflection analysis the final consideration in the design of the twoway slabs is deflection.
What is the difference between normal slab and posttensioned. This slab is much stronger as well as more durable than the normal concrete slabs. Achievement of this objective depends upon careful design, detailing and construction. The execution of the design will be explained with reference. To provide a complete idea, the stress computation, the reinforcement detailing, shear design, the jacking procedure etc. The materials to be used are grade c25 concrete and grade 500 reinforcement. Post tensioned slabs are intrinsically waterproof and. Fundamentals of posttensioned concrete design for buildings.
In 1980 fip had published recommendations for the design of flat slabs in posttensioned concrete out of print already for many years. Banded tendons when designing twoway, post tensioned slab systems, in addition to the code. Tn342 design example 2way mondada 093090 adapt corporation. Salunke mgms college of engineering and technology, kamothe, india mgms college of engineering and technology, kamothe, india abstract the use of posttensioned flat slab is increasing day by day, due to its advantages over traditional concrete. In addition, results of tendonanchor assembly tests performed at high temperatures. This spreadsheet program provides for the design and analysis of post tensioned concrete oneway beam and slab systems and twoway flat plate slab systems. Here, in chapter 18, which is exclusively for prestressed concrete, all the aspects related to unbonded post tensioned system are nicely described which includes criteria for pt slab as well as pt beams. Unless otherwise noted, all referenced table, figure, and equation numbers are from these books.
In addition, both the international building codeand the uniform building codeprovide design methods for determining the capacity of a post tensioned slab to. This hybridisation helps achieve the formation of a much thinner slab with a longer span devoid of any columnfree spaces. The choice of concrete mix and curing methods along with quality workmanship also play a key role. The slab is outside buildings which subjected to 1 hr fire resistance and design for 50 years design life. Posttensioned concrete design spreadsheet program a pdh.
The project scope consists of design and plan preparation for a 3span, posttensioned concrete haunched slab bridge, referred to by the kdot bridge superstructure log code as xcsh in this manual. Model specification for bonded and unbonded post tensioned concrete floors. 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. Posttensioning software post tensioning software builder floor pro. In the present study the design of the posttensioned flat slab is done by using both methods, load balancing. 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. This model specification offers guidance to organisations. A 5inch post tensioned slab can handle up to 5,000 pounds, and a typical 9inchthick slab will bear a concentrated 9,000pound load.
Fundamentals of post tensioned concrete design for buildings part one. The behaviour and response of flat slab and post tensioned flat slab during earthquake is an important aspect which needs to be explored. Post tensioning in buildings foreword working party wp1. Post tension design of slab there is document post tension design of slab available here for reading and downloading. Part three also covers related topics such as punching shear for twoway slabs and moment transfer at the column.
Balcony slabs in typical post tension buildings with balconies, the balcony slab is an extension of the concrete. For economical design of similar structures a smaller slab thickness leading to values between 60% to 80% of balanced selfweight is generally selected. Construction maintenance of post tensioned slab on ground. Mar 27, 2017 this video tutorial is about pts post tension slab design which is trained by master of structural engineering mr. Experimental and numerical assessment of bonded and unbonded post tensioned concrete members. Less concrete and steel are needed for the same structural capacity and the slab stiffness is increased so that the slab is better able to resist bending caused by differential soil movements. Experience and expertise gained from working on projects. Framing dead load selfweight superrimposed dead load 25 psf partitions, me, misc. For residential construction, tendons at 48 inches on center are common. Aalami a must have reference book for engineers, students, contractors, building officials, and researchers. Posttensioned pt slabs are typically flat slabs, band beam and slabs or ribbed slabs.
Posttension basics how posttensioned slabs are built the. The example presented here is for twoway post tensioned design. Post tensioning will reduce cracking and keep any cracks that might. 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. This article provides information on how to scheme a pt slab and how the use of post tensioning affects the rest of the structure. Construction of post tensioned slabs on grade is very similar to using reinforcing steel, except for the tensioning step. Post tensioning in buildings is not limited to floor slabs. Because this course is intended to illustrate simplified analysis methods, we will use the efm exclusively. Ccl carries out complete designs for posttensioned concrete applications. Given the widespread use of pt flat plate systems in the u. Joint efforts by researchers, design engineers and. The following table of prestress losses is recommended for the design of post tensioned members, and does not include friction. For professionals engaged in posttensioning design. This lab manual was prepared with the help of the renowned text book design of.
This report is intended to serve as a manual of good practice for the design of prestressed concrete flat slabs in addition to the recommended procedures, other methods are described for the sake of completeness and to compare different methods of design. General overview of post tensioned concrete design instructor. This is part two of a threepart course that covers the fundamentals of post tensioned concrete for building structures using unbonded tendons. Use the download button below or simple online reader.
Design a spread footing using 3000 psi normal weight concrete and grade 60 bars. The recommendations derived from these and other studies vary from extremely light to extremely heavy. Originally post tensioned, twoway slab framing systems were constructed with column and. This method is achieved in a process where metal or plastic tubes which contain loose tensioning cables or rods are cast into the concrete. The following table of prestress losses is recommended for the design of post tensioned members, and does not include friction or wedge set losses. Part three will continue with the study of twoway, post tensioned slab systems, including a design example using the equivalent frame concept. Joint aciasce committee 352 is therefore currently revising aci. Nonprestresed bonded reinforcement in posttensioned building design pdf. According to adoss, the interior spans due not meet the code requirements to neglect deflection. There are four 4 span arrangements and five 5 roadways plus one 2 offset crown roadway for each span arrangement included in the manual.493 1205 684 389 143 986 938 520 629 1625 292 1079 1220 1580 586 1510 1368 1586 176 171 586 1351 1442 485 1461 1632 155 1290 230 772 1399 122 1429 1182 796 1543 3 1425 707 304 114 409 833 1245 1172 60 403