In most post-tensioned residential buildings, there is a fair amount of coordination between the post-tensioning (PT) contractor and MEP trades. A post-tensioned tendon is a bundle of steel strands encased in grouted concrete and wrapped in a protective sheathing and then tensioned. Although the technology by itself is known to work. These processes assure the durability of the PT tendons but if these processes are done improperly then it can compromise the durability of the tendons causing tendon failure. As a structural element, the PT tendons/anchors take precedence over MEP sleeves, openings/penetrations, embeds and even rebar. The design and calculation of all the components were performed according to the new European code ETAG-013, which verification is an . Figure 1: post-tensioned slab failure at live end of tendons. Second, balanced load allows the engineer to offset the weight of the slab and attached fixtures. This shows the human inspectors exactly where they need to repair or replace the tendons. The compression that results from the posttensioning counteracts the tensile forces created by subsequent applied loading (cars, people, the weight of the beam itself when the shoring is removed). 2. Once the concrete has gained strength to 2000 psi, typically within the 3 to 10 days recommended by PTI, the tendons are stressed. According to Concretenetwork Post-tensioning is a technique for reinforcing concrete. Tendons may be located either within the concrete volume (internal prestressing) or wholly outside of it (external prestressing). Post-tensioned anchorage components for bonded and unbounded tendons. Before casting, corrugated ducts are often installed into the concrete along the centroidal axis. Post-tensioning is an active reinforcing technique used to place the concrete structure under compressive stress where it can face tensile stress. Request Quote. Required fields are marked *. This method also provides better reinforcement and increases the integrity of structures. A monostrand tendon consists of a seven-wire strand that is coated with a corrosion-inhibiting grease and encased in an extruded plastic protectivesheathing. 11701 Belcher Rd, Suite 120, Largo, FL 33773, 2022 Infraspect. We supply single strand, unbonded post-tension tendons, stressing equipment, and installation drawings. This corrosion can allow for air, water, and other environmental contaminants to enter the steel and weaken the overall structure. Phone: (832) 390-2588 What causes post-tensioned tendon failure? In corrosive environments, the anchorages and exposed strand tails are usually covered with a housing and cap for added protection. As such it does not need constant supervision. 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. Notify me of follow-up comments by email. The case is from a project of 13 floors with the post-tension slab. This allows any department to correctly allocate its resources towards the particular fault. 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 . P ost-tensioning is a method of reinforcing (strengthening) concrete or other materials with high-strength steel strands or bars, typically referred to as tendons. 1) Profiling : Read the drawings and identify the type of tendons, layout, locations, number of strands per tendon, the sequence of laying, number of tendons per pour, etc. Externally-bonded FRP composites Once a tendon has been cut, it is very difficult to repair. 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. 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. Ground Penetrating Radar uses radar pulses to survey a sub-surface. The post-tensioning tendons (Pre-stressing steel cables) are kept inside plastic ducts or sleeves which are placed in the position before pouring concrete. The cells or cavity containing the tendons . Advanced Robotic Bridge Inspections provide more quantitative data to better budget for maintenance and repairs. Many project managers require scanning for concrete coring services. Post-tensioning Pretensioning Post-Tensioning Steel tendons are stressed after the concrete has been placed and gained sufficient strength at the construction Bonded PT Unbonded PT site NPCA 1 fThe Precast Show 2014 Pre-Tensioning: Pre-Tensioning: Precast elements are transported to the site. AURORA HEADQUARTERS 14800 E. Moncrieff Place Aurora, CO 80011 303-576-2200 [email protected]. Many post-tensioned slabs are often stamped to alert workers, as well as owners, in case any renovations take place in the future. All Rights Reserved. . As a client-centric company, we understand the importance of taking the time necessary to correctly complete a job. Because of this, its important to know where the tendons are located in the concrete. According toFHWA, the MFL (Magnetic Flux Leakage) methods can be used to detect the location and extent of corrosion in post-tensioned and precast prestressed strands in concrete girders, and breakage of wires and strands in post-tensioning tendons and pre-stressing strands. 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." Potable, lightweight, wireless, and accurate. This approach is often used in precast concrete structures such as parking garages, office buildings and others. Large concrete slabs would crack and break under their own weight without being reinforced. You can create post-tension tendons in Revit using: Structural rebar (in this case you must edit rebar shape ) Special Structural fraiming family (see attachment) Max Kotsar. Infraspects TendonScan will locate the loss of metallic area inside an external post-tension tendon. For more than 30 years, Tendon Systems has been an industry-leading provider of post-tensioning, barrier cable, and restoration services throughout the country. This means that it can bear its own weight. 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. Post-tensioning is applied with the help of a post-tensioned tendon which is an assembly of high-strength prestressing steel bar or strand, sheath, or protective duct often made up of plastic, grout, or corrosion preventing coating and anchorage. The Tendon Systems blog is a resource for industry news and analysis, gear care, maintenance and safety best practices. Statements about the condition of prestressed steel reinforcements are not only important for ensuring the stability and usability of structures under known load levels but also for the conversion and renovation of structures. This approach is often used in precast concrete structures such as parking garages, office buildings and others. The results speak for themselves as well. The tendon scanning systems couple themselves with the tendon and travel along the whole length of it while an inspector monitors progress from a remote control unit. This data may also inform the plans of the project. The tendon was put into the duct, strained, then fixed against concrete once the concrete had solidified and had suitable strength. Give us a call at (678) 835-1100. Coring is completed to analyze the strength of existing concrete. |, Protect tendons from damage and corrosion. The slab is designed with a camber and has a maximum span of 12 m. As per the Structural designer, the slabs must be stressed after achieving the strength of 28 MPa or 70% of concrete strength. MFL is also commonly used to test the cables of suspension or cable-stayed bridges. . Once formed within a large structure it tends to sag or deflect as soon as it is introduced to live loads like a vehicular load on a bridge. An online Transportation Research Board (TRB) report details the collapse of a segmental post-tensioned concrete bridge due to corrosion. The strands are anchored into the cast-iron anchor head using the standard wedges. While it is an integral part of all post-tensioning operations, its results can . The grade of concrete for slabs is M40 and the thickness of the slab is 250 mm. Improperly surveyed concrete could have disastrous effects on the structure as well as the cost and timeline of the project. It is used in many applications. The Benefits Of Magnetic Flux Leakage for bridge inspections and international bridge inspections. Post-tensioning is applied with the help of a post-tensioned tendon which is an assembly of high-strength prestressing steel bar or strand, sheath, or protective duct often made up of plastic, grout, or corrosion preventing coating and anchorage. The first ever structure built with a prototype of the DYWIDAG Bar Post-Tensioning System was the Alsleben arch bridge in Germany in 1927. Post-tensioning is a method of reinforcing (strengthening) concrete or other materials with high-strength steel strands or bars, typically referred to as tendons. Anchorages are another critical element. 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. Post-tensioning tendons, which are prestressed steel cables inside plastic ducts or sleeves, are positioned in the forms before the concrete is placed. Outstanding Support Infraspect has developed TendonScan. Many of these external post-tension tendons that are in our bridges are exposed to chloride, air, salt water, and other elements that can aid in their corrosion. GET A QUOTE. DYWIDAG Bar Post-Tensioning Systems - A successful Tradition. The anchorage consists of an iron casting and a conical, two-piece wedge which grips the strand. The fact the tendons are kept in a permanently stressed (elongated) state causes a compressive force to act on the concrete. It is important that concrete scanning is completed before any kind of concrete work. With post-tensioning, companies save money on material costs and labor. Many steel objects are constructed of post-tensioning tendons, which are coated with a protective coating located inside the duct or sheathing. All Rights Reserved. Post-Tension Tendon inspection service for bridge inspections helps keep our bridges and box girder roadways safe. From concrete scanning to post-tensioning services, we are committed to excellence. Post-tension anchors distribute the force from the tendon into the concrete around the tendon ends. The wedges thus maintain the applied force in the tendon and transfer it to the surrounding concrete. Infraspect specially configured software can provide results long before a tendon needs to be repaired or replaced. These methods the top of the line Electric Capacitance and Magnetic Flux. 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 finishing step in any construction is a very crucial step. As such it does not need constant supervision. It also identifies places where water or air might have collected in the post-tension tendons. Tendons The basic element used in post-tensioning systems is called tendons. However, cases of PT tendon corrosion have been found worldwide. Tendons when they are placed are sometimes not grouted properly and sometimes due to age or environmental issues the grout may crack. Besides inspecting the tendons at finishing, its regular inspection is also critical for its proper functioning. This corrosion occurs due to improper grouting procedures and the accumulation of bleed water. The unit is a 16lb battery-powered robot, that crawls along the tendon. Coring occurs when sections of concrete are removed. https://www.concretenetwork.com/post-tension/. Live VSL type S 6-4, Si 6-4 anchorage. Post-tensioning is a technique for reinforcing concrete. Tendons today are seven high-strength steel wires wound together and placed inside a plastic duct. In some cases, only a local scan may be necessary. Anchorages are another critical element, particularly in unbonded systems. Thus, it is felt that meaningful conclusions and recommendations can be drawn from the study executed herein. This allows for reduced quantities of reinforcing steel and thinner slabs for a given span. It was found that the grout had high moisture content, and high pore water pH and was most likely mixed improperly by the manufacturer. Post-tensioning allows construction to be conducted in less time and at a lower price. These include metals, asphalt and masonry, in addition to concrete. The GTI Zero Void Bonded Monostrand System is the premier corrosion protection system available for single strand tendons. The data collected from these sensors can be collected for real-time assessment and also stored for later comparison that can show progression in deterioration. Sometimes, when it all goes sideways, the person running the saw (or drill, or nailgun) realizes that something has gone wrong before the tendon is completely severed. Profiling. Contact Us. Post - Tensioning work is divided into three major activities. If the tendons are corrupted, then the concrete slabs overhead can collapse as well. The data in the report correctly highlights exactly where any discontinuations are as well as other faults. Jacking stress is 80% of the tendon's ultimate strength (F pu) = 216 ksi. Post-tensioning is a technique for reinforcing concrete. 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. 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. DYWIDAG Bar Tendons are mainly used for repair . Post-Tensioning Repair Products. The unit is automated and powered by a battery. On rare occasions, the ironworker/installer will need to detension an already-stressed post tensioning tendon. There are two main types of posttensioning: unbonded and bonded (grouted). If there is no defect, the flux in the output from the metal remains uniform. Once the concrete has gained strength to 2000 psi, typically within the 3 to 10 days recommended by PTI, the tendons are . Post-tensioning tendons are made up of more than one group of prestressing steel. Post-tensioning applications include high rising buildings, office and apartment buildings, parking, structures, slabs-on-ground, bridges, sports stadiums, rock and soil anchors, and . A tendon is inserted into the casing and then the casing is grouted. It helps the decision-makers to make the right decisions about repairing or replacing a PT tendon in the structure. The use of .5-in.-diameter, 270 ksi (1860 MPa) 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. Weak concrete may need to be reinforced or even demolished in some cases. At Tendon Systems LLC we provide all kinds of services: Our offices are located in Atlanta, but we provide services all around the United States. Once the grout has reached sufficient strength, the tendon is stressed. The magnetic field will spread out when it comes across the small air gap that is created by the crack because the air which cannot support as much magnetic field per the unit volume as the magnet can. Steel strands are placed in a duct, placed in the forms or outside the forms, and tensioned prior to loads being placed. Infraspects TendonScan was specifically calibrated with software written for the inspection of external post-tension tendons. 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 . Ground Penetrating Radar (GPR) is the best way to non-invasively scan concrete. The field or magnetic field exits in the north pole and reenters in the south pole. The materials used to post-tension concrete members are ultra-high-strength steel strands and bars.

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