Post tensioning in buildings is not limited to floor slabs. The example presented here is for twoway posttensioned design. In addition, already built structures will be described. The design moment of the slab is modified for each design section to include the twisting moment of the same section woodarmer approximation. 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. Design method may not be used for twoway, posttensioned slab systems. Tributaries used when computing average precompression stress for stemmed members. Anyway, application for the post tensioning slabs system include. Model specification bonded and unbonded posttensioned.
Tn462 temperature design 060116 adapt software help. The real development took place in the usa and australia. Developers, architects, engineers, contractors, educators and. Because of post tensioning s ability to balance loads and greatly reduce service load deflections, there is a 25 percent to 35 percent reduction in slab thickness in post tensioned structures compared with mild reinforced. The pti design procedure is used to design a slab on 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. Part three continues with the study of twoway, post tensioned slab systems, including a complete design example using the equivalent frame concept. For most projects, conventional materials should be specified. Hollow core slab, bridge i girders post tensioning. Prestressed concrete is a form of concrete used in construction. Analysis and design of post tension slab using etabs software. This design should always be used unless approval to use a thinner deck is obtained from the state bridge engineer.
The following graph in figure was made to show the shear distribution along the post tensioned slab. Users manual posttensioned concrete haunched slab bridges. Framing dead load selfweight superrimposed dead load 25 psf partitions, me, misc. Low to high rise residential and commercial buildings industrial floor slabs on the ground.
In pt design, it is preferable to draw moment diagrams to the tensile face of the concrete section. Steel tendons are stressed after the concrete has been placed. Note that the coefficients of thermal expansion for concrete and steel are similar, and for design purposes, they can be considered to be the same. Unless otherwise noted, all referenced table, figure, and equation numbers are from these books. The format is similar to the existing standards available for reinforced concrete haunched slab bridges rcsh. An example of a post tensioning tendon p rofile for a. From the design criteria, the posttensioned slab is designed for a uniformly distributed superimposed dead load of 3. Post tensioned slabs prestressed concrete architectural.
General principales local zone design general zone design. International advanced research journal in science. Due to this, there arises an urge to study the behaviour and response of flat slabs and post tensioned flat slabs during an earthquake. To get the excel sheet join as loving fansub member to this channel. Stronger, more efficient floor slab design creates longer spans and reduces the need for columns within the structure. Notice the assumptions required for the post tensioned design fig. 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.
From the design criteria, the post tensioned slab is designed for a uniformly distributed superimposed dead load of 3. These checks are carried out at serviceability and ultimate limit states. The structure is checked both at serviceability and ultimate limit states. Tension concrete compressed shorter than it wants to be. Posttensioning institutes design of post tensioned slabs onground, pti design procedure 3rd edition. Tensioning force transfer by steelconcrete bond force transfer at end anchor strain compatibility and force equilibrium. The first two loss calculation methods on the form can be used to specify the prestress losses. Pti 3 structural material types structural steel prestressed concrete reinforced concrete pre.
Tensioning building structures miroslav vejvoda, p. Longer spans can be achieved due to pre stress, which. The execution of the design will be explained with reference to an example. When planning for point loads, a safe rule of thumb is to figure on 1,000 pounds per inch of slab thickness. Find out about the latest and inspiring applications of post tensioning in building. 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. 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. The tensile face indicates what portion of the beam requires reinforcing for strength. It is supported by 16 x 16 columns that are at 200 on center both ways. Black canyon highway suite 103 phoenix, arizona 85021 telephone. A post tensioned prestressed banded flat slab floor system for an office complex is shown in figure. Design of post tensioned prestressed concrete beam using excel spreadsheet with visual basic applications proceedings of 34th the ires international conference, jeju island, south korea, 02nd may 2016, isbn. Pt slabs offer the thinnest slab type, as concrete is worked to its strengths, mostly being kept in compression. The design is sensitive to differing subgrade strengths and requires the slab to be isolated from the rest of the s tructure to allow unrestrained shrinkage movement of the slab.
These secondary moment effects when combined with lateral loading become a critical issue in the design of slab. When the design of pt slab is done properly against the. Post tensioned concrete design table 11 list of symbols used in the aci 31808 code m bal design moment resistance of a section with tendons and the necessary mild reinforcement to reach the balanced condition, nmm m u factored moment at section, lbin n c tension force in concrete due to unfactored dead load plus live load, lb p. Posttension flat slab design example prestressed concrete. The stress in the post tensioning steel, f ps is then calculated and the area of required tension reinforcement, a s, is determined by imposing force equilibrium, i. A 5inch post tensioned slab can handle up to 5,000 pounds, and a typical 9inchthick slab will bear a concentrated 9,000pound load. Post tensioned slabs application pt reinforcement is used more in the residential market than in any other sector of construction. Dec 19, 2006 for example, an 8inchthick slab is typical for a 30footlong floor span 30 feet x 12 inchesfoot 45 8 inches. Equivalent tensile stress design appendix 5 examples using shrinkagecompensating concrete, p. Design method may not be used for twoway, post tensioned slab systems. Fundamentals of posttensioned concrete design for buildings.
Structural calculations for posttensioned beam and oneway. The following settings are required for this structure. To obtain maximum benefit from ccl post tensioned slabs it is recommended that they are incorporated. By design, unbonded tendons have a continuous plastic sheath ing to prevent the strand from bonding with the concrete along its length. Steel reinforcement are stressed prior to concrete placement, usually at a precast plant remote from the construction site example. Anchorages provide for the safe introduction of post tensioning forces into the concrete. 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. In the next decade numerous post tensioned slabs were designed and. General overview of post tensioned concrete design. 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. The recommendations derived from these and other studies vary from extremely light to extremely heavy.
Posttensioned concrete haunched slab xcsh design and details included in this manual are intended for the use of bridge details that can be obtained from kdot bridge section for the preparation of bridge plans. The format is similar to the existing standards available for reinforced concrete haunched slab. Appendix 3 design examples using corps of engineers charts, p. If the edge of the slab is 50 feet away from the nearest shear wall, when post tensioned this edge will. Further guidance can be found in technical report no. A good rule of thumb is that a post tensioned system will move about 1 inch for every 100 feet of slab that is not restrained by a lateral system. Aug 28, 2015 post tensioned concrete design in building works will be discussed and worked examples illustrated, where appropriate.
Objectives design specifics, detailing of post tensioning works and relevant hard wares to comply with euro codes will be highlighted. 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 highstrength tendons located within or adjacent to the concrete and is done to improve the performance of the concrete in service. Post tensioned parking structure using beam frames and oneway. The following parameters are used to represent a typical post tensioned floor slab. Post tensioned pt slabs post tensioned pt slabs are typically flat slabs, band beam and slabs or ribbed slabs. The design of a post tensioned slab on grade must address the effects of both applied loads and imposed deformations.
Posttensioned concrete design spreadsheet program a pdh. A post tensioned system will move 20% to 30% more than conventionally reinforced concrete. The following temperature change example illustrates the impact of temperature load on post tensioned members. We therefore apologize for the odd lapse into commercialism. Pdf fundamentals of posttensioned concrete design for.
Tensioning building structures march 12, 2020 2020 educode las vegas. While analyzing the post tensioned slab, there are some secondary moment effects observed. A post tensioned podium slab separate the parking below from the light residential framing above. Twoway posttensioned design amsysco post tensioning. For general design philosophy and analysis of post tensioned concrete, the reader should refer to pdhonline course s127. The following example illustrates the design methods presented in aci 31805 and ibc 2003. In addition to general design guidance and information on detailing practices, this section contains three design examples.
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