Frequently asked post-tensioning questions are listed below, You may reach us through contact form for quotation and technical queries.
Post tensioning is a innovative technique for reinforcing concrete. Post-tensioning tendons, which are prestressing steel cables inside plastic / GI ducts or sleeves, anchorages are positioned in the forms before the concrete is placed. Afterwards, once the concrete has gained strength but before the service loads are applied, the cables are pulled tight, or tensioned, and anchored against the outer edges of the concrete.
RCC structural elements are reinforced to compensate the tensile requirements based on loading and building configuration the self weight of the structures are increased due to reinforcement and concrete weight. In Post-tensioning system tendons are profiled to compensate the tension and compression requirements and the external forces applied through stressing jack which is reduces plenty of steel and concrete.
The present state of development in the field of prestressed concrete is due to the continuous research done by engineers and scientists in this field during the last 90 years. in 1886, Jackson of San Francisco applied for a patent for "construction of artificial stone and concrete pavements" in which prestress was introduced by tensioning the reinforcing the rod set in sleeves.
The development of vibration techniques for the production of high strength concrete and the invention of the double-acting jack for stressing high-tensile steel wires are considered to be the most significant contributions made by Freyssinet between 1928 and 1933.
Refer to the history the continuous research and application over 90 years. post-tensioning structures stability is generally greater than RCC due to thin slab elements, reduced self weight, axial forces and post-tensioning hogging effect provides better controls over the deflection of slab and beams.
post-tensioning is comparatively cost effective, faster construction, high structural stability, control of structural cracks, reduced deflection, flat plate provides more floor to floor clearance, eliminate short span columns, eliminate additional beams, larger spans with thin slab, clear spaced car parks, reduces building self weight, reduced axial loads saves cost on foundation and column elements.
The savings of post-tensioning elements slightly varies based on loading and building configuration. Post-tensioning utilization reduced concrete in the tension and compression zone in the range of 20 to 35%. The savings in steel are even higher, 60 to 80%, mainly due to the high permissible stresses allowed in the high-tensile wires. the decrease in structural weight reduces the design loads and the cost of foundations.
Post-tensioning raft foundation saves time on deep individual foundation excavation and tie beams installation and complicated reinforcement fixing process. avoid unexpected de-watering expenses. raft foundations are designed based on reduced PT slab self weight which is reduce the reinforcement and concrete requirements on foundation. eliminate foundation and ground floor concreting process and save time & cost.
Post-tensioning slab form work shall be removed immediately after completion of final stressing [Generally 3rd day after concreting].
Back propping need to be provided as per structural engineer recommendation.
 Form work decking  Bottom steel laying  Complete all slab edge shuttering  Fixing of PT anchors at edge shutters  Installation duct and tendons  Profile the tendons  Fixing of top bars and punching hooks  Pre-Pour Inspection  Pouring concrete  Remove edge shutters after 16 hours Obtain 3rd day cube test report  Fina Stressing  Grouting of slab after removal of back propping
The maximum design load for post-tensioning tendons is 80% of the ultimate tensile strength of the strand.
The cube compressive strength is various between the codes but the general rage is 25 to 28 Mpa.
Car Park, High Rise Towers, Villa, Residential Building, Commercial Building, Girder Beams, Raft, Micro Piles, Ground Anchor, Air Ports, Public Buildings, Shopping Mall, Mosque, Industrial Building, Long Span Structures, Stadium, Township Developments, Precast, Prestressing, Silos and Bridges
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