Introduction of steel wires in concrete to make flower pots, pipes, arches and slabs by Monier, J., (France)
First patent for Post-Tensioning (inserted steel rods into masonry units and stressed them with a threaded device) by Jackson, P. H., (USA)
Introduction of the concept of tightening steel tie rods in artificial stone and concrete arches by Jackson, P. H., (USA)
Concrete slabs and small beams manufactured with embedded tensioned steel by Doehring, C. E. W., (Germany)
Study of applying prestressing to counteract the stresses due to loads by Mandl (Austria)
Formation of American Section of the International Association for Testing and Materials (now known as ASTM).
Formation of American Concrete Institute (ACI), USA
Freyssinet introduced permanently acting forces in concrete to resist the elastic forces developed under loads. "The Birth of Prestressing.
M Koenen (Germany) studied the losses of prestress due to elastic shortening of concrete.
Steiner, C. R., (USA) analysed the losses due to shrinkage and creep was recognised, and introduction of retightening the rods to recover lost prestress.
Emperger, F., (Austria) introduced the method of winding and pre-tensioning high tensile steel wires around concrete pipes developed.
Introduction of hoop-stressed horizontal reinforcement around walls of concrete tanks through the use of turnbuckles by Hewett, W. H., (USA)
Dill, R. H., (USA) used high strength unbonded steel rods. The rods were tensioned and anchored after hardening of the concrete.
Professor Gustave Magnel emphasised on the Principle of Precompression.
Eugène Freyssinet (France) introduced of the use of high-strength wire and concrete.
Patent of Concrete anchoring device by Holmes Samuel A
First practical application of ‘long line’ pre-tensioning method by Hoyer, E., (Germany)
Eugène Freyssinet (France) introduced design for conical wedges and special jacks for stressing and anchoring the wires.
Gustave Magnel (Belgium) developed an anchoring system for post-tensioning, using flat wedges.
Shortage of steel in post-war years brought strong evidence for using P-T in replacing war damaged bridges in Europe.
Patent of means anchoring tensioned cable for prestressed concrete by Eugène Freyssinet (France)
Emile Jules Lucien Blaton introduced the method of tensioning and anchoring wire bundles for prestressed concrete structural elements patented.
Button head wire post-tensioning system BBRV patented.
Connection for precast concrete girders and beams
The Walnut Lane Bridge in Philadelphia was the first application of P-T in USA.
Use of “Basket Weave” layout with 60/40 to 75/25 ratio used for the tendons in the Column Strip (CS) / Middle Strip (MS)
First application of P-T in building was in USA by Colorado Prestressed Concrete for a Cold Storage Warehouse.
Patent of Post-stressed concrete structure by Stressteel Corp.
Formation of Prestressed Concrete Institute (PCI), USA
ACI-ASCE Joint Committee 323 published "Tentative Recommendations for Prestressed Concrete
Nuclear containment using Post-Tensioning
Hydraulic jack for the prestressing of concrete reinforcements
Edward Rice introduced Strand Tendon P-T System.
T. Y. Lin (USA) introduced the “load-balancing” design method
Prestressed concrete was first included in ACI Building Code (ACI 318)
Patent for "Prestressed girder“ by Gregory Greulich Gerald
The First Strand/Wedge Anchorage replaced by Ductile Iron Castings
Patent for anchors for stressed cables by William F. Kelly
Parma Domenico used the system for post-stressing concrete slabs, beams or other structures
Apparatus for post-tensioning prestressed concrete invented by William F. Kelly
Edward K. Rice introduced the anchorage for post-stressed concrete structures
“Banded Flat Plate” (banded/distributed) was used in the Watergate Apartment in Washington, D.C.
Patent for Tendon anchorage by Howlett Machine Works
System introduced for post-tensioning and anchoring prestressing tendons by Yegge Lawrence R
Ductile iron casting and wedge chuck anchorages were used in most unbonded P-T applications in USA
Corrosion Protection for Unbonded Tendons” was added in ACI 318
Edwards H. introduced tendon anchorage assembly with threaded support member for concrete formwork.
The publication of first Post-Tensioning Manual was initiated by the PCI Post-Tensioning Division prior to organisation of the PTI
Antonio Brandestini used the anchorage body for anchoring tendons with wedges
Patent for extruded sheathing
Reyes Cesar D emphasized on anchoring system used in post stressing concrete.
Plastic sheathing exclusively used for greased, unbonded strand
Ashraf Habibullah introduced the First structural engineering software for PCs
Formation of Post Tensioning Institute (PTI), USA
ACI 318 reduced the allowable water/cement ratio (w/c) for structures in corrosive environments from 0.50 to 0.45
Significant deterioration of parking structures was recognised in parking structures due to the effects of chlorides and corrosion
Morris Schupack and Mario G. Suarez introduced electrically isolated reinforcing tendon assembly and method
Michael Arthur Smith and David Brearley introduced wedge type anchorage device
Soum Rene P. started using prestressed cable anchorage system
Introduction of professional software for structural design and analysis
Hydraulic jack for stressing elongate elements
Raymond E. Hutchinson registers patent for "Tendon for post-tensioning prestressed concrete." (Present day system of extruding plastic sheathing around the greased strand)
Per C. Hansen and Gero Herrmann registered the patent for "Wedge anchorage for a tension member in a prestressed concrete structure.
PTI published an article in the Journal of Prestressed Concrete “Specification for Unbonded Single-Strand Tendon Materials and Commentary” specifying encapsulation of the unbonded post-tensioning system in aggressive environment. This marked the first industry standards for the sheathing and coating used in unbonded post-tensioning systems.
Importance of air content, water-cement ratio, chloride ion content, and cement type when designing for corrosion protection was added in “Specification for Unbonded Single-Strand Tendon Materials and Commentary” ACI 318
Post-Tensioning Institute (PTI) regulated the type of sheathing material, the types of coatings used, and the dimensional tolerance of the system as it is applied to the strand.
Tech Research, Inc., USA started using anchor apparatus for a tendon in prestressed concrete slab
Peter Reinhardt introduced post-tensioning anchorages for aggressive environments.
Dyckerhoff & Widmann Aktiengesellschaft registers the patent for "Corrosion protected tension member for use in prestressed concrete and method of installing same.
Incast Anchorage Systems, Inc. started using Post tensioning anchor system
PTI published, "Specification for Unbonded Single Strand Tendons", 1st Edition
PTI addressed the corrosion protection standards for the PT coating of strands.
PTI submitted the specification to ACI Committee 423 for processing as an ACI/ANSI standard
Felix L. Sorkin registered the patent for "Corrosion protection tube for a post-tension anchor system.
Felix L. Sorkin registered patent for "Corrosion protection seal for an anchor of a post-tension system.
ACI 423.6-01, Specification for Unbonded Single-Strand Tendons and Commentary, published by ACI Committee 423, ACI
Introduction of Pocket former for post-tension anchor
Felix L. Sorkin registered patent for tendon tensioning anchor system having polymeric encapsulation with reduced shrinkage effects
Formation of Post Tension Services India Pvt. Ltd. (PTSI)
PTSI introduced Unbonded Post-Tensioning System for the first time in India
First project with Unbonded P-T System in Surat, Mangaldeep II
Satsang Hall for Govind Devji Temple got acclaimed by Guinness World Records for Largest Reinforced Cement Concrete Flat Roof with a Single Span of 119 Ft. which was made possible by using Unbonded P-T System provided by PTSI
Tej Tower, Mumbai, acclaimed as one of the Top 10 Skyscrapers in India where Unbonded P-T was applied by PTSI