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Services
Welcome To NOOR Systems



Our Field Services Department is second to none and takes great pride in completing our jobs in an efficient and timely manner. We have daily contact with all of the PT engineers in town to coordinate our stressing operations. We track our pour dates on our computer program daily so that we can insure that cables are stressed in accordance with the engineer of record’s specifications. We also do PT repairs as needed and are always here to answer any questions or concerns that might arise during the construction process.

Services:

NOOR is ready to serve you the customer by picking up your foundation plans direct from the engineer. Our Estimating Department will do your take offs, and supply bids in a very time efficient manner. Our Expediting Department will be ready to ship your materials in our standard (2) day delivery time. We also have all of our materials ready for immediate pick up on CPU orders. Our Field Services Department (stressing, cutting, grouting and repairs) is second to none and your jobs will be done in a timely, cost efficient manner. Builders Post-Tension is ready to serve you with the highest quality of materials and service. NOOR exports on a worldwide basis to USA, Europe, The Middle East and Asia through a network of established agents.

Design:

design With the staff of qualified specialist, excellent theoretical support and unique experience, our company offers a professional level of design.
We carry out complex calculation according to ACI Code, standards, prepare the necessary technical documentation for successful realization of the projects (monolith carcass structures).
We design buildings of complicated configuration, working out and offering the client rational alternative solution towards traditional construction, applying monolith post-tensioning technology. We have all the necessary information data base - our work process is supported by accurate documentation on post-tensioning and the latest licensed software applied all over the world. All our specialist are of a profile education, constantly polishing their knowledge, taking in consideration the gained experience, applying up, to date products and technologies, studying new software and methods of structural design and construction.
Our company is quite young; nevertheless the team of our competent certified specialist is successfully cooperating with the leading professionals of Europe and USA in the field of design. Carrying out the project we materialize creative ideas of the architects, supporting them by engineering solutions.
We ensure both internal and external design sectors, as well as the author supervision of the construction itself.
Each project is a many-sided process. We are flexible to the requests of its every participant, if this doesn't contradict with the safety of the solution.
We react fast on the changes made in the project, offering adequate constructive and economical solutions.
Work organization and quality control system, staff that constantly enriches their knowledge in post-tensioning, our professional managers allow us to maintain the terms and high quality of our work.
design


Facts about Post-Tensioned Slabs:


  1. Approved Foundation Construction - Post-tensioned slabs are approved by the F.H.A. and V.A. since 1967. All National Building codes approved post-tensioning. Current IBC / IRC indicates that in expansive soils with the Plasticity Index greater than 15, requires that the foundation system be designed according to WRI /CRSI (Wire Reinforcement - Concrete Reinforcing Institute) or PTI (Post-Tension Institute)
  2. Control of Cracks - Post-tensioned slabs control cracks much better than other reinforced slabs, due to the squeezing pressure (tension) of the cables compressing the cracks.
  3. Time Savings - Post -tensioned can be installed much faster that other reinforced foundation systems. A typical residential foundation takes 3-4 hours to install. Time is also saved by, using fewer joints, narrower footings, less digging, and easier to clean up in the event of inclement weather.
  4. Reinforcing Savings - As steel and concrete increase in pricing, the savings with a post- tensioned slab will increase, because the quantity of steel and concrete required for a post-tensioned slab is less than for a conventionally reinforced foundation. Clean out of the footings after a rain is much faster and neater than re-bar type foundations.
  5. Engineered Foundations - The F.H.A., V.A. IBC and IRC accept post-tensioning, but it must be engineered and stamped by a licensed engineer.
  6. Fewer Joints - Large concrete areas, such as tennis courts, parking lots, warehouses, metal buildings can have joint spacing increased to minimize cost of joints and long- term maintenance of the joints.
  7. Deflection Control - Expansive soils, which can move when wet and shrink when drying can cause foundation movements and cracking. Post- tensioning increases the slab stiffness and by its increased flexural and tensile capacities, is more resistant to problematic soils. Movement of soils can sometimes be significant enough to move the structure. Slab on ground support foundation systems are still interactive with the soil.
  8. Improved Modulus of Rupture - It is a fact that concrete shrinks when it dries and cracks. By utilizing a two part tensioning process, shrinkage cracking can be reduced.
  9. Possible Less Concrete - (This depends on the foundation and what it is being compared to.) Typical post- tension beams (ribs) are 12 inches wide versus 16 inches wide for conventional. For an equivalent slab design, (stiffness) post-tensioning will require less concrete.
  10. Improved Flatness and Slab Levelness - With fewer joints and greater joint spacing, slab curling is greatly reduced. This produces a smoother ride for forklifts.

















Post-tensioning prestressed concrete elements
Attachment 1: Work method statement


WORK METHOD STATEMENT SLAB POST TENSIONING – INSTALL / STRESS / SEAL & GROUT

ITEMDETAILSACTION
1Confirm site drawings are the latest revision and are approved for construction.
2Complete formwork/falsework and stop-ends for relevant concrete pour (by others).Check that access and required work areas are clear and safe for installation requirements.
3Check and confirm that stressing material deliveries are as per delivery docket issued and retain docket in site file.
4Set out location of stressing anchorages and pockets in accordance with the issued ‘for construction’ drawings.If drawing is issued ‘for approval’ only, confirm with supervisor if OK to use.
5Slot and drill forms (if required).
6Install anchorages onto edge board as per approved drawings.Ensure that all necessary personal protective equipment is worn at all times – i.e. gloves, safety glasses, protective footwear, and safety helmets.
7Mark out tendon spacings and lay duct as per approved drawings.
8Lay pre-stressing duct, install any anti-burst reinforcement and tape duct to anchorages.
9Carefully place strand coil in strand frame prior to cutting retaining straps with tin snips.If strand frame needs to be lifted into position (by crane), use lifting frame.If frame has no lifting lugs, ensure slings pass through coil, and not off frame only.
10Position strand frame (coil) adjacent to work area and away from thoroughfares.Use safety goggles whenever strand is being cut. Ensure area is of sufficient strength to support weight of coil (3 tonne).DO NOT use heat-type cutting devices to cut strand.
11Push stand for all tendons as per drawing details.Ensure pushing area is barricaded and signage is placed to maintain safe work areas.Stand clear of strand being drawn from coil into duct.DO NOT stand between pusher and coil.
12After correct amount of stand has been placed into duct for each tendon, create dead-end (onion) on each strand.
13Straighten and profile duct as per drawing details. Check straights and profile before fixing to deck using staples. Place grout tube into anchor head grout port, and into end of duct at dead end.
14Ensure that anchorages are positioned according to the design and fixed so they do not move during normal construction activities. Ensure that anti-burst reinforcement is present and fixed central to anchorage zone (both live and dead end).
15Check installation has been completed to the best of your ability, and advise design engineer or builder/contractor that installation is complete, and ready for engineer’s inspection. Sign off relevant areas.
16During concrete pour, check that ducts and strands are not damaged by concreter. If damage occurs, notify concreter and arrange to fix.
17At completion of concrete pour, check that all anchors are clear of slurry etc. Check that test cylinders have been taken during pour and stored on site in conditions similar to slab being poured. Notify supervisor if cylinders are not taken.
18After edge board/ pan has been stripped, grease holes in anchor block/coupling block, place anchorage components over protruding strands and hard up against casting. Place two-piece wedges such that join is vertical in seat. Seat firmly with hammer. Ensure anchor is hard up to anchorage casting and clear of all slurry. Paint strand to show datum for stressing extensions.
19Check stressing jack and gauge are accompanied by valid and up-to-date calibration (kept in gauge box).Check nose on jack (or curved nose) to ensure 7 mm recess is maintained.Ensure jack operator is experienced in the use of the equipment.
20Prior to applying full stress, check that all test cylinders taken have reached 22 MPa (for 12.7 mm strand) or 25 MPa (for 15.2 mm strand). Obtain written confirmation of approved testing prior to applying any further stress.
21Inform site superintendent that stressing is to commence in the area.Ensure that a clear area is maintained to a minimum of 2 m radius around anchorages (live and dead ends) being stressed. Place twin plywood barricade directly behind line of jacks, and place and maintain all “Stressing in Progress” signs in appropriate locations around the stressing area. If formwork has been removed below (i.e. Perri system or similar), barricade the areas below the slab to the same requirements as above.
22Check the required load on the calibration chart, and confirm the gauge pressure required.
23Stress tendons in order from furthest to closest reachable position to ensure no person is standing in direct line of the jack, or previously stressed strands. Place stressing jack into position over chosen strand. Connect hydraulic pump to jack, and pressure gauge to pump.
24Stress tendons to the required load and in accordance with the calibration report and check seating of wedges at live anchorages after lock-off. Ensure that stressing load is applied gradually and evenly.
25Measure tendon extensions, complete standard stressing form and forward to the principal contractor for review and approval. (Note: Designated slabs reports to be forwarded to design engineer for approval).
26At completion of each tendon stressing, ensure barricading and signage is maintained for a period of at least two hours after full stress has been completed. Notify builder/client that no drilling/coring is to be performed on the area until grouting is completed or unless otherwise approved. Notify supervisor that stressing is completed and that signage is in place.
27Obtain verbal approval of stressing results from principal contractor or design engineer prior to cutting off excess strand and barging up anchorages recesses.
28Cut all tendons, ensuring that specified concrete cover can be achieved, using friction cutter, and place off-cuts in bins provided by others. DO NOT use heat-type cutting devices.Wear safety goggles during all cutting operations.
29Dry pack any edge recesses with sand/cement mix and fill ‘top of slab’ recesses with concrete. Use rubber gloves to prevent cement burns to skin.
30Grout tendonsBefore commencing grouting, all vents/drains should be opened and blown through to check for clear. Grout mix to be 8 litres of water per 20 kg bag of cement. Any required additives (i.e. shrinkage agents etc) to be added only on design engineer’s request. Grout cube to be taken only on engineer’s request.If formwork has been removed below barricade areas directly below slab. Dust masks, safety goggles and gloves should be worn at all times when grouting.
31Commence grouting tendon from one end through standard hose connected to dead end grout tube. Bleed minimum of 1 litre into bucket at other end, and then close vents when grout issues of same consistency as that at point of injection. Grout injection should be continuous, to avoid blockages or the formation of voids in the grout column.
32Once outward vent is closed, pressurize duct to minimum of 100 kPa, maximum of 250 kPa and hold for a period of 1 minute using pressure relief valve on pump.
33Remove grout tubes not less than 24 hours after tendon grouting is completed. Top up any vents as necessary.
34Clean up works areas and make safe any obstruction caused by stressing works.
35Forward all records and documentation to supervisor/project engineer for filing in project file.




1.4 Post-tensioning Systems and Devices
This section covers the following topics
  • Introduction
  • Stages of Post-tensioning
  • Advantages of Post-tensioning
  • Disadvantages of Post-tensioning
  • Devices
  • Manufacturing of a Post-tensioned Bridge Girder

1.4.1 Introduction
Prestressing systems have developed over the years and various companies have patented their products. Detailed information of the systems is given in the product catalogues and brochures published by companies. There are general guidelines of prestressing. The information given in introductory in nature, with emphasis on the basic concepts of the systems. The prestressing systems and devices are described for the two types of prestressing, pre-tensioning and post-tensioning, separately. This section covers post-tensioning. Section 1.3, “Pre-tensioning Systems and Devices”, covers pre-tensioning. In posttensioning, the tension is applied to the tendons after hardening of the concrete. The stages of post-tensioning are described next.
1.4.2 Stages of Post-tensioning
In post-tensioning systems, the ducts for the tendons (or strands) are placed along with the reinforcement before the casting of concrete. The tendons are placed in the ducts after the casting of concrete. The duct prevents contact between concrete and the tendons during the tensioning operation. Unlike pre-tensioning, the tendons are pulled with the reaction acting against the hardened concrete. If the ducts are filled with grout, then it is known as bonded post-tensioning. The grout is a neat cement paste or a sand-cement mortar containing suitable admixture. The grouting operation is discussed later in the section. The properties of grout are discussed in Section 1.6, “Concrete (Part-II)”. In unbonded post-tensioning, as the name suggests, the ducts are never grouted and the tendon is held in tension solely by the end anchorages. The following sketch shows a schematic representation of a grouted post-tensioned member. The profile of the duct depends on the support conditions. For a simply supported member, the duct has a sagging profile between the ends. For a continuous member, the duct sags in the span and hogs over the support.



Figure 1-4.1 Post-tensioning


Among the following figures, the first photograph shows the placement of ducts in a box Girder of a simply supported bridge. The second photograph shows the end of the box Girder after the post-tensioning of some tendons.
The various stages of the post-tensioning operation are summarized as follows.
1) Casting of concrete.
2) Placement of the tendons.
3) Placement of the anchorage block and jack.
4) Applying tension to the tendons.
5) Seating of the wedges.
6) Cutting of the tendons.
The stages are shown schematically in the following figures. After anchoring a tendon at one end, the tension is applied at the other end by a jack. The tensioning of tendons and pre-compression of concrete occur simultaneously. A system of self-equilibrating forces develops after the stretching of the tendons.
Casting bed
Duct
Side view
(a) Casting of concrete
Jack
(b) Tensioning of tendons
Anchor
(c) Anchoring the tendon at the stretching end
1.4.3 Advantages of Post-tensioning
The relative advantages of post-tensioning as compared to pre-tensioning are as follows.
  • Post-tensioning is suitable for heavy cast-in-place members.
  • The waiting period in the casting bed is less.
  • The transfer of prestress is independent of transmission length.

1.4.4 Disadvantage of Post-tensioning
The relative disadvantage of post-tensioning as compared to pre-tensioning is the requirement of anchorage device and grouting equipment.
1.4.5 Devices
The essential devices for post-tensioning are as follows.
1) Casting bed
2) Mould/Shuttering
3) Ducts
4) Anchoring devices
5) Jacks
6) Couplers (optional)
7) Grouting equipment (optional).
Casting Bed, Mould and Ducts
The following figure shows the devices.
Casting bed
Mould
Duct
Anchoring Devices
In post-tensioned members the anchoring devices transfer the prestress to the concrete.
The devices are based on the following principles of anchoring the tendons.
1) Wedge action
2) Direct bearing
3) Looping the wires
Wedge action
The anchoring device based on wedge action consists of an anchorage block and wedges. The strands are held by frictional grip of the wedges in the anchorage block. Some examples of systems based on the wedge-action are Freyssinet, Gifford-Udall, Anderson and Magnel-Blaton anchorages. The following figures show some patented Anchoring devices.
Direct bearing
The rivet or bolt heads or button heads formed at the end of the wires directly bear against a block. The B.B.R.V post-tensioning system and the Prescon system are based on this principle. The following figure shows the anchoring by direct bearing.
Looping the wires
The Baur-Leonhardt system, Leoba system and also the Dwidag single-bar anchorage system, work on this principle where the wires are looped around the concrete. The wires are looped to make a bulb. The following photo shows the anchorage by looping of the wires in a post-tensioned slab. The anchoring devices are tested to calculate their strength. The following photo shows the testing of an anchorage block.
Sequence of Anchoring
The following figures show the sequence of stressing and anchoring the strands. The Photo of an anchoring device is also provided.
Jacks
The working of a jack and measuring the load were discussed in Section 1.3, “Pretensioning Systems and Devices”. The following figure shows an extruded sketch of the anchoring devices.
Couplers
The couplers are used to connect strands or bars. They are located at the junction of the members, for example at or near columns in post-tensioned slabs, on piers in posttensioned bridge decks. The couplers are tested to transmit the full capacity of the strands or bars. A few types of couplers are shown.
Grouting
Grouting can be defined as the filling of duct, with a material that provides an anticorrosive alkaline environment to the prestressing steel and also a strong bond between the tendon and the surrounding grout. The major part of grout comprises of water and cement, with a water-to-cement ratio of about 0.5, together with some water-reducing admixtures, expansion agent and pozzolans. The properties of grout are discussed in Section 1.6, “Concrete (Part-II)”.
The following figure shows a grouting equipment, where the ingredients are mixed and the grout is pumped.

1.4.6 Manufacturing of Post-tensioned Bridge Girders
The following photographs show some steps in the manufacturing of a post-tensioned Igirder for a bridge (Courtesy: Larsen & Toubro). The first photo shows the fabricated steel reinforcement with the ducts for the tendons placed inside. Note the parabolic profiles of the duct for the simply supported girder. After the concrete is cast and cured to gain sufficient strength, the tendons are passed through the ducts, as shown in the second photo. The tendons are anchored at one end and stretched at the other end by a hydraulic jack. This can be observed from the third photo.
(a) Fabrication of reinforcement
(b) Placement of tendons
(c) Stretching and anchoring of tendons
The following photos show the construction of post-tensioned box girders for a bridge (Courtesy: Cochin Port Trust). The first photo shows the fabricated steel reinforcement With the ducts for the tendons placed inside. The top flange will be constructed later. The second photo shows the formwork in the pre-casting yard. The formwork for the Inner sides of the webs and the flanges are yet to be placed. In the third photo a girder is Being post-tensioned after adequate curing. The next photo shows a crane on a barge That transports a girder to the bridge site. The completed bridge can be seen in the last Photo.
(a) Reinforcement cage for box girder
(b) Formwork for box girder
(c) Post-tensioning of box girder
(d) Transporting of box girder
(e) Completed bridge