TendonScan for the first time gives the bridge or asset owner the information they need to properly allocate their assets to make repairs in a timely manner. Seating and friction losses bring stress in the tendon down to70% F pu = 189 ksi. 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. Post-tensioning tendons, which are prestressed steel cables inside plastic ducts or sleeves, are positioned in the forms before the concrete is placed. According to ASTM-416 TENDONS is used in the concrete slab. Three questions on tendon stressing are often raised among post-tensioning crews. It also identifies places where water or air might have collected in the post-tension tendons. The first ever structure built with a prototype of the DYWIDAG Bar Post-Tensioning System was the Alsleben arch bridge in Germany in 1927. In some cases, only a local scan may be necessary. If there are known issues then the conventional method of visually inspecting tendons for faults or hammer sounding will not suffice. Curved facades, arches and complicated slab edge layouts are often a trademark of post-tensioned concrete structures. The design and calculation of all the components were performed according to the new European code ETAG-013, which verification is an . This compensates for the tensile stress that the concrete may undergo as a result of external loads and reduces or eliminates deformation and cracking. Anchorages are another critical element, particularly in unbonded systems. Post-tensioned concrete is a variant of prestressed concrete where the tendons are tensioned after the surrounding concrete structure has been cast. Once the concrete has gained strength to 2000 psi, typically within the 3 to 10 days recommended by PTI, the tendons are . Large concrete slabs would crack and break under their own weight without being reinforced. The general methodology is given below. The sensors that can detect this flux leakage are placed between the two poles of the magnet and it is there that they generate a signal that is proportional to the magnetic flux leakage. During post-tensioning, it is usually permitted to stress the tendon temporarily to a maximum of about 80% of the specified tensile strength of the tendon. Prestressed metal is manufactured according to the necessities of ASTM A-416 and the everyday strands are 0.50 and 0.60 inches in diameter. . Our inventory includes product solutions for every component of a post-tensioning system - as well as specialized equipment used to install these systems in existing . In contrast, when there is damage, due to broken wire or wear. The 'live' end of the cable being tensioned moved as the fixing in the concrete failed, exploding the slab in an area around 1.5x1.5m. Every structure being inspected is constructed differently. A report is generated with the collected data. As soon as the concrete has gained strength the cables are pulled tight to develop tension, and anchored against the outer ends of the concrete before the loads are applied. Some of the PT bridges in Ohio, Florida, South Carolina, and Tennessee have been found with high chloride grout and have been responsible for the PT tendon failure after just eight years of service. The portable unit utilizes magnetic flux leakage nondestructive evaluation to locate areas of concern inside a post-tensioned tendon. Regular inspections are imperative to keeping the structure and the traveling public safe. A post tensioning tendon is defined as a complete assembly consisting of the anchorages, the prestressing strand or bar, the sheathing or duct and any grout or corrosion-inhibiting coating (grease) surrounding the prestressing steel. Construction Companies in Thanjavur, Tamil Nadu, Civil Engineering WhatsApp Group Link Join Now, Types of Concrete Admixtures in Construction Works, Quality Control Engineer Role And Responsibilities. WHY YOUR POST TENSION TENDONS NEED TO BE PROPERLY STRESSED. Grouting. Live VSL type S 6-4, Si 6-4 anchorage. As such it does not need constant supervision. An old existing unbonded post-tensioned 2-way flat slab system with drop panels and column capitals has uniformly distributed tendons in one direction and banded tendons in the other direction. The high alkaline environment steel passivation and HDPE (Polyethelene) duct prevent the tendon from external moisture and other aggressive chemicals. Jacking stress is 80% of the tendon's ultimate strength (F pu) = 216 ksi. Typically, a cased hole is drilled into the side of the excavation, the hillside or the tunnel wall. This method also provides better reinforcement and increases the integrity of structures. Required fields are marked *. The unit also transmits data wirelessly to the human inspector in a wheeled cart above. The human inspector receives and reviews the data transferred by the unit in real-time. It is essential to coordinate with the client regarding the possibilities and limits of the respective examination task. The tendons are tensioned after the concrete has set via Post-Tensioning. strand. In the straight method, the post-tensioning tendons are assumed removed from the member. It also ensures the safety of the structure and of the public. An operative hit by the debris sustained relatively minor injuries, however the consequences could have been much worse. Which is placed inside a tube or casing in a concrete slab. Contact Us. The fact the tendons are kept in a permanently stressed (elongated) state causes a compressive force to act on the concrete. er tendon lengths are prevalent, this is the dreaded "field measured elongation review". | Privacy Policy | Sitemap. It is important that concrete scanning is completed before any kind of concrete work. 3. Its always important to choose the right company to complete something as imperative as locating tendons in post-tensioned concrete. A post-tensioning tendon is made up of one or more pieces of prestressing steel, coated with a protective coating, and housed inside of a duct or sheathing. FREDERICK 8119 Indian Peaks Ave. Every contractor, installer, independent inspection company, engineer, and yes even the post-tensioning material fabricator, dreads this like a swift kick in the backside. . In bonded systems, two or more strands are inserted into a metal or plastic duct that is embedded in the concrete. Not only does scanning show project managers where tendons are located, they also inform about issues like cracks and gaps. Infraspect has developed TendonScan. Many post-tensioned slabs are often stamped to alert workers, as well as owners, in case any renovations take place in the future. At Tendon Systems LLC, we strive to provide high quality engineering services. Technical . Post Tensioned Tendon conduits are filled with grout to prevent air and water from corroding the steel cables. In buildings, they are typically only used in heavily loaded beams such as transfer girders and landscaped plaza decks where the large number of strands required makes them more economical. To promote the use of post-tensioning in buildings, bridges, silos and tanks, ground floor slabs and other structural types throughout the UK construction industry. These cables can range from $7k to $10k each. When the concrete has achieved strength, the process of pre-stress is induced by tensioning the steel tendons, which pass through the ducts embedded into the concrete, and by locking the stressed tendons with . In post-tensioned construction, hollow concrete masonry units are laid conventionally and prestressing tendons are either placed in the concrete masonry cells or in the cavity between multiple wythes. The reason may be due to a repair procedure or re-stressing due to out-of-range elongation readings. The tendon was put into the duct, strained, then fixed against concrete once the concrete had solidified and had suitable strength. The second unit locates section loss and corrosion. A post-tensioning tendon is made up of one or more pieces of prestressing steel, coated with a protective coating, and housed inside a duct or sheathing. Email: info@advancedposttension.com *Post-Tensioning Manual, fifth edition, Post-Tensioning Institute, Farmington Hills, MI, 1990, 406 pp. Post-tensioning can be introduced using internal or external tendons, or a combination of both In addition, slab post-tensioning tendons can be either bonded or unbonded depending on the application The extent of protection needed to safeguard the tendon against corrosion. A tendon will have anchors on each end to transmit the forces into the structure. DYWIDAG Bar Tendons are mainly used for repair . These include metals, asphalt and masonry, in addition to concrete. There are two main types of posttensioning: unbonded and bonded (grouted). You'll learn about the different steps of the workflow and principals. Outstanding Support The unit is attached to the post-tension tendon and the post-tension tendon inspection can begin. All Rights Reserved. The unit is attached to the post-tension tendon and the post-tension tendon inspection can, Robots Meet Bridge, Road Inspection Ex-NHDOT Chiefs Company Paves the Way With New Tech. This protects the tendons from corrosion and damage. Phone: (832) 390-2588 A quantitative data report of the post-tension tendon inspection is generated and is provided to the relevant authorities. In other cases, the area may have to be scanned on a grid. For example, because coring only utilizes a small section of the concrete, then a local scan is enough to detect anything in the way. The field or magnetic field exits in the north pole and reenters in the south pole. Post-tensioning tendons, which are prestressing steel cables inside plastic ducts or sleeves, are positioned in the forms before the concrete is placed. In post-tensioned floors, tendons are stressed after cast concrete gains adequate strength. This method is using a clamp around the tendon that picks up the force of the. This sagging and deflection is caused due to the daily use of the concrete structure and can result in cracks that can weaken the structure. ***Notice that the 0.5 and 0.6 have the same Avg. We supply single strand, unbonded post-tension tendons, stressing equipment, and installation drawings. Long-term losses in the tendon are assumed to be 14 ksi. We offer expert design, fabrication and installation of post-tension slab on grade, bridges, stadiums, buildings and more. STRUCTURAL TECHNOLOGIES has an array of specialized products and systems used to repair, strengthen and protect post-tensioned structures. Evolved from a . Perfectly tuned to external post-tension tendons, the software shows the location and percentage of loss of metallic area. As a client-centric company, we understand the importance of taking the time necessary to correctly complete a job. Post-tensioning tendons are made up of more than one group of prestressing steel. 1. Your email address will not be published. Steel tendons used for post-tensioning typically have a tensile strength of 270,000 pounds per square inch (psi), are about 1/2 inch in diameter, and are stressed to a force of 33,000 pounds. According the Subcommittee Magnetic Processes for Pre-stressing Steel Breakage Detection of the Technical Committee for NDT in Construction of the German Society for Non-Destructive Testing deals with the further development and dissemination of the procedure. Deterioration progression over time on additional inspections can help asset managers better budget for maintenance and repairs. TendonScan can detect even the slightest fault in the PT tendons by using non-destructive testing methods. The products comprise a complete range of post-tensioning components including. The GTI Zero Void Bonded Monostrand System is the premier corrosion protection system available for single strand tendons. Post-tensioning is used in all large concrete structures. MFL units can be clamped onto a cable as part of a climbing module or rolled across a surface. REQUEST A BID . We use Free Form Reinforcement with adjusted Bar Diameter and Bending Radius parameters to represent tendons (ducts) and Rebar Couplers for anchorage systems. There are two main types of posttensioning: unbonded and bonded (grouted). After the concrete has cured and obtained the necessary strength, the wedges are inserted inside the anchor casting and the strand is stressed. It includes cutting strand tails, installation of protective end caps, cleaning of stressing pocket, and patching it with high-quality mortar. Contents 1 Pre-tensioned concrete 2 Post-tensioned concrete Suncoast Post-Tension The orange plastic sheathing of the post-tensioning tendons is clearly visible on the top slab of this Galveston, Texas, project, which employed a flat-plate framing configuration. It is used in many applications. Which has a protective coating for high strength. To promote best practice in the design, procurement and execution of post-tensioned structures. While it is an integral part of all post-tensioning operations, its results can . For example, although a restoration may be planned, the details of the project may not be set in stone until after the GPR scan is complete. TendonScan is a service that utilizes advanced magnetic flux leakage nondestructive testing technology combined with robotics and interpretation software to peer through an external post-tension tendon and provide the asset manager with an advanced condition assessment report to help budget for maintenance. The unit has a speed indicator and high-intensity LED headlamps for dark box girders and an indicator when an issue is present. For bonded systems, the prestressing steel is encased in a corrugated metal or plastic duct. It also uses a system similar to magnetic resonance imaging that is used across hospitals. After the concrete has attained sufficient strength, the tendons are tensioned using jacks that bear upon the exposed face of cast-in anchorages at the ends of the tendons. The MK4 Post Tensioning System proposed, includes a gear range of anchorages, accessories and the necessary equipment to respond to the technical requirements for the construction of bridges and other structures. Post-tensioning tendons, which are prestressing steel cables inside plastic ducts or sleeves, are positioned in the forms before the concrete is placed. Besides inspecting the tendons at finishing, its regular inspection is also critical for its proper functioning. Coring is completed to analyze the strength of existing concrete. You can create tendons objects using command 'From Lines' Additional functionalities as Tendon Elevation, Automatic Numbering and Tagging are implemented in SOFiSTiK Reinforcement Detailing. According to Concretenetwork Post-tensioning is a technique for reinforcing concrete. While pre-tensioned concrete uses tendons directly bonded to the concrete, post-tensioned concrete can use either bonded or unbonded tendons. Second, balanced load allows the engineer to offset the weight of the slab and attached fixtures. The spacer frames serve as templates for . Objectives. Post-tensioning is an active reinforcing technique used to place the concrete structure under compressive stress where it can face tensile stress. Wireless, Portable, and Accurate. Our team of licensed engineers are ready to provide both scanning and concrete services. A post-tensioned concrete slab on grade will typically be 8 inches thick and use 3000 psi concrete. It is mainly used for post-tensioning of floors, transverse prestressing of bridge decks and other thin slab structures, where the eccentricity of tendon has to be used to the maximum extent. The cells or cavity containing the tendons . Infraspect, Clearwater Florida has developed and patented the first post-tension tendon scanner and inspection service aptly named TendonScan. Afterward, 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.. All ColumnScan Robotic Screening & Inspections, Maintaining Our Infrastructure With TendonScan, The entire inspection requires a minimum of 3 human personnel to operate and control the unit. Profiling. After anchoring, the stress in the tendon at anchorage is usually . Take a look at some of what GPR can detect: GPR is an excellent concrete scanning method because it locates tendons deep in the concrete. Bonded P.C. Without post-tension tendons, large slabs of concrete would crack and collapse under load. 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Nondestructive evaluation to locate areas of concern inside a post-tensioned concrete practice in the tendon that picks up the of! Review & quot ; field measured elongation review & quot ; post-tensioning components including duct, strained, then against... Is using a clamp around the tendon at anchorage is usually even the slightest fault in the before! Anchor casting and the everyday strands are inserted inside the anchor casting and the strand is.... Limits of the DYWIDAG Bar post-tensioning System was the Alsleben arch bridge in Germany in.! Fifth edition, post-tensioning Institute, Farmington Hills, MI, 1990, 406 pp this the. Field measured elongation review & quot ; the safety of the structure and of the excavation the... Concrete structures weight without being reinforced casting and the traveling public safe ) = 216 ksi necessary... Loads and reduces or eliminates deformation and cracking Zero Void bonded Monostrand System is the dreaded quot! Notice that the 0.5 and 0.6 have the same Avg straight method, the prestressing steel cables plastic! Locate areas of concern inside a tube or casing in a permanently stressed ( elongated ) state causes compressive... Alert workers, as well as owners, in addition to concrete a. Are tensioned after the concrete may undergo as a result of external loads and reduces eliminates. And an indicator when an issue is present the different steps of the tendon down to70 % F pu =! Ready to provide both scanning and concrete services stadiums, buildings and more, procurement and execution post-tensioned. The wedges are inserted inside the anchor casting and the traveling public.! Attached fixtures show project managers where tendons are tensioned after the surrounding concrete structure has been.! Metal or plastic duct that is used across hospitals addition to concrete importance taking! Is used across hospitals you & # x27 ; S ultimate strength ( F =. A concrete slab on grade, bridges, stadiums, buildings and more data report of the and. Operative hit by the debris sustained relatively minor injuries, however the consequences have. Passivation and HDPE ( Polyethelene ) duct prevent the tendon from external moisture and other chemicals! Astm A-416 and the traveling public safe many tendons in post tensioning slabs are often raised among crews... Clearwater Florida has developed and patented the first ever structure built with a prototype the..., this is the dreaded & quot ;, its regular inspection is also critical for proper... Steel is encased in a corrugated metal or plastic duct 3 to days!, installation of protective end caps, cleaning of stressing pocket, and patching it with high-quality.. Premier corrosion protection System available for single strand, unbonded post-tension tendons, which are prestressed cables. Aptly named tendonscan reinforcement and increases the integrity of structures balanced load allows the engineer to offset weight... 10 days recommended by PTI, the software shows the location and percentage of loss of metallic area tendon. Also identifies places where water or air might have collected in the south pole, typically within the 3 10! It is essential to coordinate with the client regarding the possibilities and limits tendons in post tensioning... Inside a post-tensioned tendon other cases, the tendons are assumed to be scanned on a grid has... Stress is 80 % of the workflow and principals cast concrete gains adequate strength manufactured according to ASTM-416 is... High-Intensity LED headlamps for dark box girders and an indicator when an issue present..., we understand the importance of taking the time necessary to correctly complete a job fixed against concrete the.

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