Process Flow of a Project

Process Flow of a Project

It starts with a discussion

Our marketing personnel visits you to understand your project and specific requirements. This information is passed on for the further process. It all begins when you send the drawings.

Take a journey with the drawings to find out the processes and activities which it undergoes till the final execution at site.

Over to PTSI

Once your drawings reach us, our coordinator maintains a proper database. To provide the best possible solutions we route our all out-going communication through this central position.

We try to pick up your specific requirements as early as possible and forward for detailed feasibility check.

Feasibility check

Experience and expertise gained from working on various projects, PTSI is commited to deliver prompt, quality and effective solutions.

We understand the importance of the customer requirements. That is why we strive to check the feasibility and scope of work for the project at the utmost priority.

Prelim design and Estimation

As soon as the scope of work is decided, we prepare a preliminary design based on the structural configuration and feasibility.

This inputs are used to derive the quantity estimation for P-T Elements and other items.

Final design for construction

To provide continuous high performance solutions, PTSI uses the latest design software which is continually updated to reflect current national and international construction codes of practice.

PTSI prepares a set of drawings like forming plan, reinforcement plan and P-T drawings. This set of drawings are send to the site for further implementation of the system.

Product assembling

PTSI delivers outstanding post-tensioning solutions and products. The drawing displays the layout of P-T cable and its accessories.

This give the details of the BOQ and based on this, the final product is prepared for the respective project.

On site activities

PTSI is committed to maintain its quality both in design and at site. The installation and stressing activities at project site are followed by number of inspection and quality assurance formalities.

PTSI keeps the safety as upmost important aspect and takes care of necessary parameters related to safety at every stage.

Final review

PTSI understands its responsibility and assures its clients by issuing a Certificate of Stability after conducting gravity analysis and design of Post-Tensioning.

This affirms the stability and required capacity of the P-T members to provide intended function under the gravity condition.

General Criteria for the Design of Post-Tensioned Elements

(Ref.: ACI 318M-11, IS 1343 : 2012, IS 456 : 2000 and Post-Tensioning Manual, 6th Edition)
  • Live Load (LL): in kN/m2 (As per recommendation received from the Structural Consultant)
  • Floor Finish (FF): in kN/m2 (As per recommendation received from the Structural Consultant)
  • Wall Load: in kN/m2 (either as per recommendation of the Structural consultant or as per the information available about the wall layout, thickness and  unit weight of the material to be used)
  • Service Duct & False Ceiling Load: in kN/m2 (As per recommendation received from the Structural Consultant)
  • Self-weight of the members: as per the section size (considering pre-stressed concrete weight 23.5 kN/m3 as per IS 875 part 1 : 1987)
  • Minimum Grade of Concrete (fck): M35 (cube strength)
  • Grade of Steel: fe415 or fe500 (as per the recommendation from the consultant/client in advance for the prelim design)
  • Level of Prestressing as per ACI 318M-11 (clause 18.3.3):
    • For Two-Way Flat Slabs: Class U; Tensile Stress Limit of concrete slab section for "Serviceability Design Requirements as per ACI 318": less than or equal to 0.5*square root of equivalent cylindrical strength value of concrete grade at the mid-span bottom fiber zone.
    • For One-Way Slabs and Beams: Class T for the Normal Loading Criteria and Class C for heavy loads from floating (stub) column to the Girders as well as for member design for Fire Tender Loading.
  • Level of Prestressing as per IS 1343-2012 (clause 24.2.1):
    • For Two-Way Flat Slabs: Type-2 with tensile stresses below 3N/mm2 at the mid-span bottom fiber zone.
    • For One-Way Slabs and Beams: Type-2 for the Normal Loading Criteria, and Type-3 for heavy loads from floating (stub) column to the Girders as well as for member design for Fire Tender Loading.
  • Criteria for maximum spacing of tendon placement shall be followed as per ACI 318M-11 clause 18.12.4: 8*slab thickness and 5ft whichever is smaller  for the uniformly distributed tendons in slab.
  • Additional non-prestressed reinforcement provided as per the criteria of ACI 318M-11 clause 18.9 for minimum non-prestressed reinforcement and clause 18.7 for the required non-prestressed reinforcement to achieve required flexural strength at ultimate load combination case. Reinforcement requirement for temperature and shrinkage effects shall be as per clause 19.6.3.3 of IS 1343 : 2012 i.e. 0.15% of total cross section area of the concrete section.
  • Permissible Deflection values (Long Term with shrinkage and creep effect considering creep coefficient as 2) as per IS 1343 : 2012 clause: 20.3.1 a, b, c:
    • Final Downward Deflection due to SW + LL + FF + SDL + PT + Effects of Shrinkage and Creep (corresponding to SW + FF + SDL + PT) should not be    more than span/250
    • Downward Deflection (occurring after erection of partitions and the application of finishes) due to Shrinkage and Creep (corresponding to SW + FF + SDL + PT) and LL should not be more than span/350 or 20mm whichever is lesser shall be considered.
    • Total upward deflection should not exceed span/300 unless uniformity of camber between adjacent units can be ensured.
      Note: The criteria 12.1 and 12.2 same as prescribed in IS 456 : 2000 clause 23.2.a and 23.2.b respectively.
  • Anchorage of P-T Cable shall be placed such that the centroid of all the anchorage should fall under middle-third of the depth (kern) of member. Preferably, it shall not be more than 2/3 depth of the member when measured from the bottom.
  • The minimum CGS height of tendon at the mid-span shall not be less than 38 mm in case of slab and 55mm in case of beam when measured from the  bottom.
  • Minimum clear cover to the reinforcement shall be 20 mm for the slab and 35 mm clear from the longitudinal reinforcement for the beams.
  • PTSI submits moment of resistance (moment capacity) at respective sections for P-T beams when the Structural Consultant likes to consider them for the lateral force resisting system. The Consultant can provide necessary passive reinforcement based on the moment of resistance in addition to the requirements of gravity force design performed at PTSI.
  • Reference of National and International Codes

    IS 456 : 2000 Indian Standard Plain and Reinforced Concrete – Code of Practice
    Published by: Bureau of Indian Standards, New Delhi, India
    This standard deals with the general structural use of plain and reinforced concrete. It provides guidelines about the material used in building construction such as cement, mineral admixtures, aggregates, water, chemical admixtures, reinforcement, concrete, etc. In addition to this, general design considerations such as stability of structures, serviceability aspects, fire resistance, durability, workmanship, reinforcement detailing for various structural elements and general criteria for the arrangement of reinforcement to achieve necessary workmanship are prescribed.


    IS 1343 : 2012 Indian Standard Prestressed Concrete – Code of Practice
    Published by: Bureau of Indian Standards, New Delhi, India
    This standard deals with the general structural use of prestressed concrete. It covers both work carried out on site and the manufacture of precast prestressed concrete units. It describes about materials, workmanship, its inspection and testing, general design requirements, structural design based on limit state method. There are three classifications described under the serviceability aspects based on the amount (level) of prestressing; such as type 1, 2 and 3. The major revision was in the direction of activities related to grouting that are carried out after stressing of tendons in bonded (grouted) P-T system. All the provisions are mainly for prestressed beams and girders. Provisions for post tensioning in slab are not been incorporated.


    IS 13920 : 1993 Indian Standard Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces – Code of Practice
    Published by: Bureau of Indian Standards, New Delhi, India
    This standard covers the requirements for designing and detailing of monolithic reinforced concrete buildings so as to resist severe earthquake shocks without collapse.

    IS : 875 - 1987 Indian Standard Code of Practice for Design Loads (other than Earthquake) for Buildings and Structures
    Published by: Bureau of Indian Standards, New Delhi, India
    This standard guides for the consideration of loading during the design of structural members. The minimum requirements pertaining to the structural safety buildings are being covered in this code by way of laying down minimum design loads which have to be assumed for dead loads, imposed loads, wind loads, snow loads and other external loads, the structure would be required to bear. We follow this document in absence of the loading criteria - generally recommended by Structural Consultant of the project.

    IS 14268 : 1995 Indian Standard Uncoated Stress Relieved Low Relaxation Seven-Ply Strand for Prestressed Concrete – Specification
    Published by: Bureau of Indian Standards, New Delhi, India
    This standard covers the requirements for manufacture, supply and testing of un-coated, stress relieved low relaxation seven-ply steel strands for prestressed concrete.

    IS 1865 : 1991 Indian Standard Iron Castings with Spheroidal or Nodular Graphite – Specification
    Published by: Bureau of Indian Standards, New Delhi, India
    This standard covers grades and the requirements of iron casting with spheroidal or nodular graphite classified on the basis of mechanical properties measured on test pieces prepared from separately-cast test samples, and from cast-on test samples.

    IS : 9175 (Part 20) - 1986 Indian Standard Rationalized Steels for the Automobile and Ancillary Industry, Part 20: Mechanical and Physical Properties of 20MnCr5 Grade Steel
    Published by: Bureau of Indian Standards, New Delhi, India
    This standard covers the mechanical properties, hardenability and isothermal transformation characteristics of 20MnCr5 grade of steel for use by automobile and ancillary industry.

    ACI 318M-11 Building Code Requirements for Structural Concrete and Commentary
    Published by: American Concrete Institute, USA
    This Code covers the materials, design, and construction of structural concrete used in buildings and where applicable in non-building structures. The Code also covers the strength evaluation of existing concrete structures. Among the subjects covered are: contract documents; inspection; materials; durability requirements; Concrete quality; reinforcement details; analysis and design; strength and serviceability; precast concrete; prestressed concrete; strength evaluation of existing structures; and provisions for seismic design. The commentary is provided to mention the considerations of the committee in developing the criteria. 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 P-T slab as well as P-T beams. This also classifies the level of prestressing in terms of class U, T and C based on the tensile stresses permitted in the tension zones of P-T element.

    ACI 423.6-01 Specification for Unbonded Single-Strand Tendons and Commentary
    Published by: American Concrete Institute, USA
    These specifications provide specific performance criteria for materials for unbonded single strand tendons and detailed recommendations for fabrication and installation of unbonded single strand tendons.

    PTI Guide Specification for Unbonded Single Strand Tendons
    Published by: Post Tensioning Institute, AZ, USA
    These specifications provide specific performance criteria for materials for unbonded single strand tendons and detailed recommendations for fabrication and installation of unbonded single strand tendons.

    Value Engineering

    Value Engineering

    As a result of their wide experience gained from their involvement in 100s of projects of varying sizes in locations throughout the India, PTSI's employees are able to draw on the latest ideas and technologies from market to offer different perspectives on each and every project. Using value engineering methodology, PTSI can determine the optimum means by which the specific requirements of a structure may be met.

    Working Standards

    PTSI have dedicated, professional engineers having in-depth knowledge of reinforced and pre-stressed concrete and possess a considerable understanding of the design of structures.

    Designing

    At PTSI, exceptional design is not restricted to creating safe, elegant and durable structures, but also includes the delivery of cost-effective solutions which are fast and easy to build and which have due regard for sustainability. We believe in maintaining the designing standards and always seek for improvements.

    Drawing

    The design is actively supported by with finer detailing of particular elements in the form of drawings and schematics. It is our practice to graphically represent the elements which are easy to understand and conceivable by site engineers and contractors.

    Operations

    PTSI strictly follows the guidelines specified in the "Field Procedures Manual for Unbonded Single Strand Tendons", 3rd Edition, Post-Tensioning Institute. With adherence to that our team conducts inspection after every cycle of installation and stressing activity respectively. The inspection reports are regularly reviewed and necessary steps are taken accordingly.

    Construction Methodology

    Scope of Work for Mono-strand Unbonded Post-Tensioning System

  • Formwork shall be made (by general contractor) as per the forming plan issued by PTSI / Structural Consultant. There is nothing special except the wooden sides (shall be provided by general contractor) required for drilling holes (by PTSI) so that the cables can be passed through them at required places at certain height as per P-T detail.
  • Do not provide camber to any of the P-T elements (P-T slab or P-T beam) without prior consent to PTSI.
  • In case of P-T beam, the steel cage (i.e. open stirrups near the supports up to 2m and closed stirrups in mid-span zone with continuous longitudinal steel only) is prepared (by general contractor) as per regular practice with the detail provided. Do not place extra top steel at this time.
  • Support bars are fixed (by PTSI) at certain intervals and heights as per P-T drawing.
  • P-T cable to be placed over the support bars in PT beam (by PTSI).
  • The wooden sides of P-T beam or P-T slab are marked and drilled (by PTSI) at specific places. Anchorage assembly is fixed at the wooden side (by PTSI). The side is then fixed up to its place (by general contractor) after or before installation of cable (as per site condition).
  • Cable is passed through the assembly and the extra length kept beyond the side for stressing wherever required as per drawing (by PTSI).
  • After installation of P-T Cables, extra top steel shall be placed (by general contractor) in P-T beam and P-T slab as per drawing.
  • After installation of P-T Cables, Concealed conduits for electrical purpose must be placed (by Electrical Agency). ANY KIND OF ALTERATION IN PT CABLES ARE STRICTLY PROHIBITED while placing electrical conduits if there is any.
  • Final checking of the P-T system by the engineer of PTSI on site. It is recommended that the steel detail got checked on site by the engineer from the Structural Consultant as well.
  • Concrete must be well compacted especially at surrounding of the anchorages as well as in remaining area with due care (RMC / Concrete Agency).
  • Cubes are cast on site (by RMC / Concrete Agency) for 5 day and 28 day strength testing as per respective codal provisions. Certain cubes required to test (by other agency) between 5 to 7 days depending on the commitment of strength gain by the concrete supplier in accordance with respective codal provisions.
  • Stressing is commenced (by PTSI) once the target strength for stressing (25MPa) is ensured through the cube testing.
  • Stressing is performed as per stressing sequence already provided to the stressing personnel. Stressing platforms must be ready on site as well as electricity supply must be arranged on the floor (by general contractor) prior to stressing.
  • Elongations are measured on site; Stressing Record is generated (by PTSI) for our internal approval. Post stressing status is conveyed to the Structural Consultant, General Contractor, PMC and Owner for shuttering removal (by PTSI). Elongation Report is sent (by PTSI) to the Structural Consultant for his reference.
  • Shuttering can be started (by general contractor) for the successive floor above.
  • Sufficient propping (re-shoring) shall be provided (by general contractor) to the floor(s) up to one or more levels down (based on the mass of the wet concrete according to the thickness of PT slab + size of P-T beam) on which this form-work is resting. Re-shoring below the lower floor shall be removed only after getting approval of de-shuttering (removal of shuttering) for the successive (above) floor through email from PTSI.