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. Pretensioned concrete is a variant of prestressed concrete where the tendons are tensioned prior to the concrete being cast 25 the concrete bonds to the tendons as it cures, following which the endanchoring of the tendons is released, and the tendon tension forces are transferred to the concrete as compression by static friction 7 pre tensioning is a common prefabrication technique. Pdf prestressed and posttensioned concrete yatniel. 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. Comparing pre tensioned and post tensioned concrete. Solid slab is ideal for short spans with shallow construction depths. A normal slab is basically a rcc reinforce cement concrete slab where as a post tentioned slab is the psc prestressed concret slab. Difference between pretensioning and posttensioning. Concrete slab design software economically design post tensioned and reinforced concrete floors including slabs, mats, and rafts, with exceptional visibility into compliance, efficiency, and practicality. This article provides information on how to scheme a pt slab and how the use of post tensioning affects the rest of the structure. General overview of post tensioned concrete design instructor. The prestressed concrete design of a structure is influenced by either of the two processes, pretensioning, and post tensioning.
Unless otherwise noted, all referenced table, figure, and equation numbers are from these books. Structural engineers select appropriate beams for example hollow. Cover page i prestressed concrete design page ii this page intentionally left blank. Guidelines for the design of post tensioned floors by bijan o. The execution of the design will be explained with reference. 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. The program is divided into three separate screens, which correspond to the three major areas of concern in the design of a post tensioned. From the design criteria, the posttensioned slab is designed for a uniformly. This video describes the benefits and challenges of both methods and describes how they are built.
Pt slabs offer the thinnest slab type, as concrete is worked to its strengths, mostly being kept in compression. Fundamentals of post tensioned concrete design for buildings part one. Cables are arranged as indicated by the engineer and chaired to run through the center of the slab. Construction of post tensioned slabs on grade is very similar to using reinforcing steel, except for the tensioning step. Post tensioned slabs use highstrength tensioned steel strands to compress the slabs, keeping the majority of the concrete in compression. Pretensioning and posttensioning in prestressed concrete. Caprani in pre tensioned members, the strand is directly bonded to the concrete cast around it. Developers, architects, engineers, contractors, educators and. Pdf there are many fully or half precast slab systems in construction industry.
Solid slab deck infill deck, beam and slab deck, voided bridge deck. To provide a complete idea, the stress computation, the reinforcement detailing, shear design, the jacking procedure etc. Prestressed, pre tensioned, tendons are tensioned by a jack without any concrete. Precast and prestressed concrete design is based on the provisions of aci 31805. Consumption of prestressing steel in the usa cumulative curves. The design prestressing force in each span will be cho.
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. Precast and prestressed concrete design is based on the provisions of aci 318 05. 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 reinforcement is not limited to necessary areas. For residential construction, tendons at 48 inches on center are common. Post tensioning by controlling the amount of prestress, a structural system can be made either flexible portal frame, or rigid floor slab without influencing its strength. This spreadsheet program provides for the design and analysis of post tensioned concrete oneway beam and slab systems and twoway flat plate slab systems. The behaviour and response of flat slab and post tensioned flat slab during earthquake is an important aspect which needs to be explored. Pre tensioning can be further classified into two categories such as linear pre tensioning and circular pre tensioning. Jurgens his article presents a set of guidelines intended to t assist designers in routine post tensioning design. Difference between pretensioning and post tensioning. The recommendations derived from these and other studies vary from extremely light to extremely heavy. 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. These methods are generally adopted in the making of psc girders, sleepers etc.
Post tensioned pt concrete floors are now widely used in the uk, particularly for highrise buildings. The behavior of post tensioned flat plates in the critical column area is of great concern to designers. This is part two of a threepart course that covers the fundamentals of post tensioned concrete for building structures using unbonded tendons. Pre tensioning is accomplished by stressing wires or strands, called tendons, to predetermined. Therefore, at the ends of the member, there is a transmission length where the strand. Structural calculations for posttensioned flat slab. Prestressed concrete is concrete that has had internal stresses introduced to counteract, to the degree desired, the tensile stresses that will be imposed in service. The following example illustrates the design methods presented in aci 31805 and ibc 2003. It was found that a certain amount of poor design was prevalent, and the. Longer spans can be achieved due to prestress, which can also be used to counteract deflections. Information has been gathered from a number of sources. 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.
The purpose of this report is to pre sent an overview of pertinent informa. Pdf design of twoway prestressed slabs piotr sokal academia. Typical products for pre tensioned concrete are roof slabs, piles, poles, bridge girders, wall panels, and railroad ties. What are the differences between prestressed, pretensioned and post tensioned concrete. A more detailed guide to the design of pt floors can be found in the concrete societys technical report 43 tr43. Ce 437537, spring 2011 pretensioned beam example 1 15 pretensioned beams are typically manufactured by a vendor in a prestressing yard. Comprehensive design example for prestressed concrete psc girder superstructure bridge with commentary task order dtfh6102t63032 us customary units submitted to the federal highway administration prepared by modjeski and masters, inc. Finally, an example of a flat slab floor system is pre sented to illustrate the practice. By doing the comparative analysis and design of post tensioned flat slab with a conventional slab, we can show how beneficial will be the process of making pt flat slab than other slabs. Pretensioning and posttensioning in prestressed concrete design. This lab manual was prepared with the help of the renowned text book design. Page iii prestressed concrete design second edition m.
Pretensioning and post tensioning both methods are used under pre stressing process which has few edges over the orthodox nonstressed structures like greater span to depth ratio, higher moment and shear capacity. Posttensioned, reinforced concrete slab design software ram. Pdf new concept of semiprecast concrete slab on pre. Post tensioning in buildings is not limited to floor slabs. Pretensioned prestressed concrete bridge beams and bridge. Framing dead load selfweight superrimposed dead load 25 psf partitions, me, misc. The example presented here is for twoway post tensioned design. Posttensioned concrete design spreadsheet program a pdh.
What is the difference between pretension and post tension. Unfortunately, specific design provisions for shear strength and flexural strength of unbonded prestressed slabs are not provided in the present aci code aci 31871. Design floors and foundations reliably and efficiently, saving time and money, and overcoming the most common concerns you face as a designer. 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.
Twoway posttensioned design amsysco post tensioning. Pre tensioned precast double t units for very long spans e. Post tension slab working principle, components and. Pre compression of concrete forcearea or pa also helps to. Fundamentals of posttensioned concrete design for buildings. This hybridisation helps achieve the formation of a much thinner slab with a longer span devoid of any columnfree spaces. A psc is applied with a compressive stress on the cross section in advance before the application of loading on. The concrete slab consisted of pre tensioned concrete boards as a bottom formwork and reinforcement as well as. These results were compared with other information, i. Pdf design of twoway prestressed slabs researchgate.
General principales local zone design general zone design examples from pratice published by vsl international ltd. You will learn about the load balancing concept, hyperstatic moments, pre stress losses, the basic requirements of the. 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. General principales local zone design general zone design. Pdf prestressed concrete design andres dela cueva academia. What is the difference between normal slab and post.
Results of fire tests of 18 slabs and beams with post tensioned reinforcement constitute a major source. Posttension basics how posttensioned slabs are built. Prestressed, pretensioned and posttensioned concrete. Comprehensive design example for prestressed concrete. Pre tensioned and post tensioned concrete is not well understood.