Post Tension Slab Problems

The Post-tensioning Institute designed Post-tensioned foundations. 5 kip/in2 w L = 0. Sections are tension-controlled when the tensile strain in the extreme tension. There are four basic options for slab leak pipe repairs: Direct Access. 5 kip / (28/12) = 9. Re-bar is seldom used throughout a post-tension slab. The slab is reinforced in two directions at 75% of its depth. Low water pressure, especially a sudden drop, can indicate a major slab leak. Curtain wall engineers can assist in heading off problems with post tension slabs. In most residential jobs, poured concrete foundations will receive a modicum of steel reinforcement to strengthen them. ASD vs LRFD. If you are having problems with your pier and beam foundation, your floor will likely feel much less stable. This eliminates cracking in the floor which gives additional protectin against termites as well as many other benefits. Post-tensioned foundations are significantly more stable than conventional rebar foundations, because stresses have to exceed the tensioned strength before a crack could form. Just a few months ago we noticed cracks in some of our ceramic floor tile that go straight across the tile and along the grout line and nothing was dropped on the tiles. The cable is going to be in the centre of the slab. In fact, back before slab technology was refined, most homes were elevated by pier and beam structures. For such slabs, a welded wire mesh with six-inch holes will suffice to reinforce the slab. Post-tension reinforcement are stranded cables that are contained typically in a plastic sheath. The Concrete Institute of Australia is an independent, not for profit organisation made up of many members who share a common interest in staying at the forefront of concrete technology, design and construction in this country. This eliminates cracking in the floor which gives additional protectin against termites as well as many other benefits. Once inside I observed a hole in the ceiling about 5 inches in diameter and 1 inch deep. Post tension is the norm on the west coast. Note: a C- average is equivalent to a GPA of. Could this be a foundation issue?. Good curtain wall engineers will address the issue early if they are responsible for designing embeds in post tension slabs. If it’s a hot water line you may notice warm areas on the floor, and infrared thermal image can quickly locate the problem. Results are compared with those obtained from the method contained in the. Without seeing the situation its impossible for me to speculate if you’ve got a problem. Murrah Federal Building in Oklahoma City and the World Trade Center towers in 2001 spawned many vows to never let anything like those events happen again. Post-tensioning is a form of prestressed concrete in which high-strength steel strands are cast into a concrete slab or beam and tensioned to a high degree of stress following curing. A CCL-designed post-tensioned slab can contain. the successes and the possibilities, we boast of; proud of our achievement, and eagerto enthuse and to generate new and bolder projects. An understanding of the use and operation of post tension systems allows Vector Corrosion Services (VCS) to effectively assess their current condition and recommend rehabilitation options. This study seeks to analyze cost estimating of the structural frame (column and slab) by considering cast-in-place and precast concrete slabs and columns, respectively. These categories of cracks are caused by entirely different phenomena and have very different characteristics. A New Post-Tensioned Continuity Detail for Super Tees—David Molloy Code Issues AS5100. The term 'cross-sectional area' (CSA) is used to refer to the area of the section under consideration, both for the concrete and for the steel. You can also ask if the corporation has had any problems with cables and if they have had issues, what they are doing to address them. Considering these technical problems combined with time life and economical analysis, it has been. When the cables are tensioned, the concrete is placed in compression. For most projects, conventional materials should be specified. My experience with foundation repairs on post tension slabs is that they are seldom if ever stabilized to the point that they will not move in the future. Bonded and unbounded post-tension structures present unique challenges for maintenance and repair. Mild-reinforced ribbed mat foundations are rarely used in these areas. You’ll want to locate these (and anything else that is lurking within) before you begin any drilling, coring or cutting. Each metal cable is inside a plastic tube that protects it and allows the cable to move during the tensioning (tightening) operation. cable you can. From that link it seems that usually happens 3-10 days after pour, it has been 17 days. L&C Building Design was founded in 2010 by Max Pham, a skillful civil engineer. ) and Bridge Special Provisions. Reinforcement is generally put into concrete to cater for its relative weakness in tension compared with compression. 00 m, find the tension in the wire and the components of the force exerted by the wall on the left end of the beam. Additionally, the perimeter “beam” of a post-tension slab does not go very deep into the ground, and the slab is more likely to. Post-tensioning (PT) is one of the most advanced and efficient technologies used to reinforce concrete. a piled foundation). This is particularly true for post tension cable systems. This test is very important to make sure our repair has been completed properly, there are. He has achieved this through quality work, vigourous employee training and upgrades to all equipment. , their strength. This is a HUGE mistake for a slab to be trowel finished. A pier-and-beam foundation is slightly less affected by soil type and moisture content, especially if the piers are resting on top of a rock layer. Aalami] on Amazon. This report investigates why post-tensioned ribbed mat foundations are more common in these areas than mild-reinforced. yielding, or may be in excess of the critical local buckling load due to beneficial post-buckling reserve. Tendons can also be swept around openings within a floor slab with little relative effort giving designers more freedom. Just verified through two engineers and numerous termite companies. Once you have wet drywall, mold quickly grows inside the walls. Under slab leak detection typically involves water pipe inspection and water line video. In monolithic foundations, the exterior cracks translate directly to the interior floor. Cutting post tension cables can be very dangerous. Slab-on-Grade Foundations. The section at the support is subjected to a negative moment, the slab being under tension and ignored, and the beam width is that of the web b. Below is a non-exhaustive list of underground services or elements bound in concrete that Construction X-ray can detect:. Post-tensioned foundations are particularly susceptible to this problem because, until the stressing is applied to the post-tensioned cables, there is no reinforcement in these slabs. The PCI Design Handbook1 recommends limits onspan-depthratiosforthehollowcoreslabs. A raised foundation with a crawl space is one of three types of foundations; the other two are concrete slab foundations and full-height basements. Raised foundations and full basements were by far the most common prior to the 1970s,. A residential post-tensioned concrete slab will typically be 8 inches thick and use 3000 psi concrete. If the house has dropped 2" you have a pretty significant problem. (5-mm) diam­ eter wires. Prestressed concrete. In areas where there are expansive clays or soils with low bearing capacity, post-tensioned slabs-on-ground and mat foundations reduce problems with cracking and differential settlement. This is because it assists them with finding and avoiding possible problem areas that could cause project delays, or even cancellations. This can help to minimize cracking and differential settlement in adverse conditions. Disadvantages of Post tension slab: The post tension slab can be made only by skillful professionals. Our clients are home remodeling contractors, architects, home owners and engineers. Post tension courts seldom have structural cracks, but often develop hairline cracks. Problems may not become evident for some time after construction (often when the house is occupied) possibly due to factors such as abnormally dry weather conditions during building. First, a definition is in order: A slab foundation is created by digging about a foot or so into the ground where the house is to be located, pouring concrete into the hole and reinforcing it with. When I was building post tension slab homes, and we needed to trench for something, we had a "locator" come out and tell is where the cables were, then it was all jackhammer work from there, going very slowly. As a rule of thumb, a properly designed post-tensioned slab can resist a post load of about 1,000 pounds per inch of slab thickness, so a 5-inch-thick slab can resist a 5,000-pound post load. A wider blade requires more tension than a narrow blade, and it’s best to align your wheels under the most tension they’re likely to receive. Tendons are typically ½" diameter made of 7 steel wire strands that is then greased and encased in a plastic coating. 7) Authenticity with 3d software finite element for design and drawings. and Design of Residential Slabs-on-Ground, BRAB Report #33. The focus is on field issues that often arise, which may affect the. Post tensioning can also have a large impact on the design and deflections of balconies. If you really want to move the drain then have someone come in and x-ray the slab. 17 Moment vs. checked in beams and slabs in water retaining structures and bridges, but don't need to be for columns). PT slabs offer the thinnest slab type, as concrete is worked to its strengths, mostly being kept in compression. A Post-tensioned slab on grade has many advantages over conventional reinforcements. What is post-tension anyway? Particularly in the 1970s and 1980s, many buildings in Calgary were built with post-tension cable construction in one or more of the horizontal concrete slabs. Thanks to Lift-Slabs!! US post-tensioning industry owes its existence to lift-slab construction First lift-slab buildings in the US were built in the mid 1950s using non-prestressed slabs Problems with deflections and slab weight in long 2-way spans To solve deflection and weight problems, lift-slab companies changed to post-tensioned slabs. If you have 2" PVC, chip away enough concrete to replace the drain and go from there. It is critical for all cable anchors and post-tension cables to undergo proper maintenance. 0 INTRODUCTION Post-tensioned floor slabs in Australia and South East Asia are now universally regarded as the most cost effective form of construction for shopping centres, office buildings, and carparks where spans exceed 7. April 2013 NMDOT BRIDGE PROCEDURES 1-1 AND DESIGN GUIDE CHAPTER ONE GENERAL INFORMATION The New Mexico Department of Transporta-tion uses the Current Edition of the AASHTO. I too, was looking for the best solution for my home; which is the most cost effective, and what are the pros and cons of each type. This eliminates cracking in the floor which gives additional protectin against termites as well as many other benefits. Organic soil is a type of soil that contains a high percentage of organic matter. This can help to minimize cracking and differential settlement in adverse conditions. Just fill it !. The section at the support is subjected to a negative moment, the slab being under tension and ignored, and the beam width is that of the web b. Resists cracking & heaving. Crack Control-Watertightness: Post-tensioned structural systems eliminate closely spaced joints and help ensure water-tightness by placing the floor in bi-axial compression, thereby controlling and counteracting shrinkage and flexural cracks. The cables are utilized frequently in the elevated concrete decks and sometimes in the ground floor slabs of condominium structures (including the associated parking garages). This project explains how to repair a large wide crack in my patio concrete slab with Emecole 555 Fast polyurea resin. Advantages of the post-tension slab: Longer life expectancy. A New Post-Tensioned Continuity Detail for Super Tees—David Molloy Code Issues AS5100. The Concrete Centre, part of the MPA. To study the behavior of post tensioned flat slabs typical office floor plate of 9. On the premise that "Those who ig-nore history will be condemned to relive it," this paper attempts to docu-ment those types of problems that lead to cracking in post. Practical Yield Line Design 2 Notation Symbols The symbols used in this publication have the following meaning: Symbol Description Units A Area of column cross-section m2 a, b, c Plan dimensions of slab supported on several sides m D Dissipation of internal energy kNm E Expenditure of energy by external loads kNm. • Cracks caused by applied loads (flexural or shear cracks). Re-bar is seldom used throughout a post-tension slab. There is no such thing as a crack-free slab, but there are slab systems that use rebar and post-tensioning that can greatly reduce the WIDTHS of the cracks. A CCL-designed post-tensioned slab can contain. This paper compares the different structural response between unbonded and bonded post-tensioned concrete slabs under fire conditions. These are: (i) In post-tensioned structures. ƒConsider vertical resistance ƒLimit shear deformation for horizontal loads ƒCompression over the entire face of the bearing pad ƒAvoid direct contact in case of rotation ƒAvoid that the bearing protrudes outside the edges. 2—Construction load factors 4. b) The proper procedures and equipment to perform reinforcing steel and post-tensioning activities and; c) Employees involved in reinforcing bar and post-tensioning operations shall be certified by a qualified evaluator (third-party). Results are compared with those obtained from the method contained in the. According to the Seattle Daily Journal of Commerce, this is due to the relatively high cost of structural steel, such as rebar. In corrosive environ-ments, stuffed and heat-sealed tendons have the inherent shortcoming of either trapping or allowing access of corrosive substances in the oversized sheathing. Suncoast post-tension materials serve a multitude of construction projects, including high-rise and slab on ground, plus innovative solutions for complex problems. Slab modeling, analysis, and design procedures feature a suite of sophisticated tools and applications, couple with post-tensioning, punching-shear, and beam detailing, and integrate the influence of soils, ramps, columns, braces, walls (rectilinear or curvilinear), and other interfacial elements. nary design of reinforced concrete slabs. Post-tensioned slabs-on-ground provide a cost-efficient, high-performance solution for problems associated with ground-supported residential foundations on shrink-swell soils. It's a 14 year old pocket. " Today's flat‐slab post‐tensioned buildings, for example, with columns spaced (12 m) on center and span‐depth ratios of 40 are more complex and require more engineering attention than typical flat‐slab buildings of 40 years ago, with columns spaced at (6 m) on center and span‐. As a rule of thumb, a properly designed post-tensioned slab can resist a post load of about 1,000 pounds per inch of slab thickness, so a 5-inch-thick slab can resist a 5,000-pound post load. Post-Tensioning Tendon Type Prestress Loss-PSI Slabs Beams & Joints Stress Relieved 270K Strand 30,000 35,000 Low Relaxation 270K Strand 15,000 20,000 Bars 20,000 25,000 The diagram on this slide illustrates the impact of friction and wedge set (i. In this case, the cladding has to be refitted. Poor drainage can result in ponding ofwater, which allows clays to absorb water, expand, and cause problems. Post-tension reinforcement are stranded cables that are contained typically in a plastic sheath. This is to make sure that your foundation repair can stand the test of time and resist the problems that you've had to deal with in the past. The Index of Computer Programmes now maintained in the Institution’s Library contained, at the end of 1962, about 150 items, under the following headings: aircraft and ships (3), arches (3), bridges (13), chimneys (2), composite action (7), continuous beams (7), general mathematical (lo), jetties (3), piles (3), piping (4), plane frame structures (47), plates and slabs (4), properties of sections (9), shells (6), soil mechanics (7), stairs (2), tanks (2), vibration (3) and miscellaneous (10). My experience with foundation repairs on post tension slabs is that they are seldom if ever stabilized to the point that they will not move in the future. the strain of the outermost layer of pretensioning, M-ε psN, relationship for different post tensioning jacking force, P p, for the PCI 8 girder 46. The results from 16 tests conducted at ambient and elevated temperatures on unbonded and bonded post-tensioned one-way spanning concrete slabs are presented. The steel ratio should be greater than or equal to the minimum required steel ratio per ACI Code 318-11 Section 10. Corrosion of post-tensioned tendons due to moisture is the most common cause of failure. History of the Post-Tensioned Concrete System. 8) Substandard specifications for tendon finishing and inspection. tendon too deep in the Slab, and the r-meter cannot find any other tendons, re-bar, or mesh anywhere in the foundation. backshores—shores placed snugly under a concrete slab or structural member after the original formwork and shores have been removed from a small area at a time, without allowing the slab or member to deflect; thus, the slab or other member does not yet support its own weight or existing construction loads from above. In areas where there are expansive clays or soils with low bearing capacity, post-tensioned slabs-on-ground and mat foundations reduce problems with cracking and differential. Down here, they use humongeous beams and post-tension slabs due to the clay soils. I'm trying to understand the pros/cons of my foundation options. If movement began to effect this home, the already ill fitting cladding can bow out to a greater extreme. 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 The Precast Show 2014 Pre-Tensioning: Pre-Tensioning: Precast elements are transported to the site. Most often the cracks extend across the entire foundation and occur prior to tensioning of the tendon cables. They are: • Cracks caused by the restraint to axial slab shortening (RTS cracks). These help support and give strength to the slab once the concrete has been cured and they have been tensioned at the proper pressure. has specialized in Foundation Repair for Commercial and Residential structures. We can even find voids and delamination and tell you slab-thickness. Identifying Grouting Problems on Post-Tensioned Bridges What Was the Need? To strengthen concrete after it has hardened, engineers have sometimes used a method called post-tensioning, which involves running steel strands through a hollow plastic or metal duct within a concrete beam. side, the A Nc value is consequently reduced. Slab deterioration is a cyclical problem that can start out small and become significant with time. Slab leak repair has become a major repair item because the piping that is laid underneath the slab is prone to leaking. My experience with foundation repairs on post tension slabs is that they are seldom if ever stabilized to the point that they will not move in the future. Further, deflections do not normally need to be checked in columns. Suspended concrete slab is referred to a cement slab that is not in contact with the ground. Quad-Deck uses patented technology to create an energy efficient and quality insulating concrete floor and roof system. Steel strands are placed in a duct. The superimposed dead load (SDL) is 1. After about 10 days the post tension cables were pulled to tension and the cracks appear to have closed a little bit, but still visible. A post tension slab has tensioned cables running through the floor. Murrah Federal Building in Oklahoma City and the World Trade Center towers in 2001 spawned many vows to never let anything like those events happen again. This is Houston’s only website dedicated to providing Houston area home buyers, sellers, and homeowners with independent, unbiased information about slab-on-ground foundations for single family homes. What is a Post Tension Slab. Ensuring the construction of post tension slabs as per the specifications and drawings. Design of stiffened slabs-on-grade on shrink-swell soils are thin post tension slab on grade, slab on grade and on piles, and elevated structural slab Problems associated with shrink-swell. For the repair and modification of post tensioning (PT) systems as well as post-tensioned concrete structure repair and protection, STRUCTURAL TECHNOLOGIES offers highly specialized products and services including investigation, repair design support, repair and replacement components, corrosion protection products, strengthening solutions as well as new or replacement post-tensioning systems. Lastly, there is the possibility that the foundation would need repair before any work on other parts of the building could proceed. Post tension slab is a combination of conventional slab reinforcement and additional protruding high-strength steel tendons, which are consequently subjected to tension after the concrete has set. Post-tensioning applications include office and apartment buildings, parking structures, slabs-on-ground, bridges, sports stadiums, rock and soil anchors, and water-tanks. I too, was looking for the best solution for my home; which is the most cost effective, and what are the pros and cons of each type. "An architect’s dream, a delight for developers, a great tool for builders and kind on the environment. concrete, post tensioned slab construction or vacuum dewatering. Large concrete slabs would crack and break under their own weight without being reinforced. ANALYSIS AND DESIGN OF POST-TENSIONED DECK TYPE BOX-GIRDER BRIDGE A post- tensioned deck type Box – Girder Bridges of clear span 30m and width of roadway is 7. Post-Tensioned vs. From small concrete repair projects to multi-faceted multi-million dollar full scale restoration projects in Canada and the U. Lastly, there is the possibility that the foundation would need repair before any work on other parts of the building could proceed. Sample Design Calculations. : The slip sheet must be installed directly under the slab Inconsistent Slab Thickness. Structural analysis to understand breakage tolerance Under conditions where tendon failures are suspected or known, a structural analysis is performed to understand the structure's load-carrying capacity, as well as the level of tolerance available for post-tensioning failure before the structure no longer provides an acceptable level of safety. a) The nature of the hazards associated with reinforcing steel and post-tensioning activities; and. How can I tell if I have a post tension slab? A. The prestressing strands in PT structures, however, are. To study the behavior of post tensioned flat slabs typical office floor plate of 9. MATERIALS SCIENTISTS. 5) Do not consider the impact of the slabs on the tendon profile. Excel, for example, is a powerful spreadsheet. • Cracks caused by applied loads (flexural or shear cracks). This includes slab on grade foundations, basements and crawl space homes like pier and beam foundations or block and base builds. Slab-on-grade construction for commercial, institutional, recreational, and industrial floor slab applications use a wide range of design options, including reinforced concrete, unreinforced concrete, post-tensioned concrete, and fiber-reinforced concrete for both structural and non-structural slabs. Though this system is not currently for sale, GSSI continues to support our StructureScan Mini customers and clients. The cables are utilized frequently in the elevated concrete decks and sometimes in the ground floor slabs of condominium structures (including the associated parking garages). 0m was considered. 6) Over balancing the dead load in your designs. The design of the foundation will be dependent on many factors, from potential vertical rise of the soil, vegetation around the foundation, the size and shape of the structure' etc. Pre-tensioning and Post-tensioning both method are used under pre-stressing process which have few edge over the orthodox non-stressed structures like more span to depth ration, higher moment and shear capacity. Post-Tensioning in Prestressed Concrete. Post Tensioning Solutions LLC - 130 37th Street Northeast, Auburn, Washington 98002 - Rated 5 based on 3 Reviews "The only answer to a Post Tensioning. Barring the introduction of a new source of moisture (a. A pier-and-beam foundation is slightly less affected by soil type and moisture content, especially if the piers are resting on top of a rock layer. We will group the cables and space them throughout a slab, just as we would an elevated slab. We can furnish all or part of the foundation package including reinforcing materials, stressing of tendons, and system repairs. Could this be a foundation issue?. side, the A Nc value is consequently reduced. This type of concrete slab construction requires different concrete slab design from the one we normally see that is cast on the ground. The thickness of slab and drop was 200/400mm considered based on the standard span / depth ratio of post tensioned flat slabs. However, with the cable wrapped in concrete, can't imagine any problems. MJM Engineering is NCEES certified, a national certification recognizing MJM Engineering as a Model Engineering Firm. 17 Moment vs. STRUCTURAL RELIABILITY CCL Post-Tensioned Slabs show reduced cracking. When I walked through the house the slab was cracked from one side to the other. According to the way loads are transferred to supporting beams and columns, slabs are classified into two types; one-way and two-way. Suncoast post-tension materials serve a multitude of construction projects, including high-rise and slab on ground, plus innovative solutions for complex problems. A shower with a drain against the pipe wall is unacceptable. We had one customer come back with the "VE the slab to post tension" and the cost savings was offset by the redesign fee. How To Detect And Fix A Slab Leak A slab leak is a break in a pipe that runs beneath the concrete foundation of your home. Post-tensioning offered a potential solution to the problem of weight and deflection in lifted slabs in buildings. Wet subbases/subgrades. Suncoast post-tension materials serve a multitude of construction projects, including high-rise and slab on ground, plus innovative solutions for complex problems. If the house has dropped 2" you have a pretty significant problem. Current design practice provides post-tensioned on-grade slabs with stiffness equal to or better than other post-tensioned slab types, but with less susceptibility to swell pressures exerted by expansive soils. for improved durability and lower maintenance costs. It was actually the widespread use of the "post-tensioned" slab-on-ground which induced this interest in design procedure and in many studies of reported slab failures. Slab Foundations. However, if expansive soils are present, the slab may move up, behaving like a. With the addition of Post-Tensioning, they can be used in grounds containing poor quality or loose or expansive (clay) soil. Unlevelled Floor. The design of the foundation will be dependent on many factors, from potential vertical rise of the soil, vegetation around the foundation, the size and shape of the structure' etc. anchorage seating) losses on the effective post-tensioning force in a strand. The Post-Tensioned slab is thinner which reduce the construction time for clients. Our uniformed, professional GPR Technicians are trained to handle a wide variety of residential and commercial Concrete X-ray issues. Construction, Designs, Stressing. Most often the cracks extend across the entire foundation and occur prior to tensioning of the tendon cables. A post tension slab is a concrete slab that has steel cables running through it that have been placed under 33,000 +/- pounds of tension. Post Tension Cable Locators, Inc. A floor slab in a building where stability is provided by shear walls in one direction (N-S. pdf), Text File (. A Post-tensioned slab on grade has many advantages over conventional reinforcements. It is a concrete slab that has steel cables running through it that have been put under lots of stress to reduce cracking of the concrete and increases the strength of the slab. Helical Piles. Due to presence of piers, the slab cannot move down. BBB File Opened:. Our company, DYWIDAG-Systems International USA Inc. AAA Foundation Service of Houston began repairing slab foundations back in 1955 when Houston was still a small bustling Texas city. In this era of fierce competition L & C Building Design provides effective design and engineering solutions to our Clients at very reasonable rates. We moved into a brand-new home in 2015 that was built with a post-tension slab. A water leak under slab moves from the floors into drywall which soaks the water up like a sponge. Most concrete is not prestressed. Contrary to popular opinion, post-tensioned slabs are no more difficult to alter or demolish than other structural forms. Despite the improved grouting practices over the past decade, existing post-tensioning systems may have significant amount of grout defects, which could lead to corrosion of the strands. Slabs are usually used in floor and roof construction. This type of building wrap is “liquid water closed” and “vapor water open. Slabs can be on-ground, suspended, or a mix of both. txt) or read online for free. This is particularly true for post tension cable systems. A spreadsheet is a computer application that simulates a paper worksheet where becoming increasingly popular in solving engineering related problems. Steel can stretch under tension and the concrete around it cracks and loses efficiency. Once tensioned, the cables cannot be de-tensioned. VSL provides repair, strengthening and protection for concrete structures including bridges, office and residential buildings, factories and warehouses. Pier and Beam vs Slab Foundations – Dallas Fort Worth When shopping for a home in the Dallas Fort Worth area, there are seemingly endless decisions to be made. In the Chapters 5 and 6 are described the possibility of assembly of components behaviour into the whole joint behaviour for resistance and stiffness separately. They cannot be used where you have a lot of fill dirt under the home (such as homesites where a lot of holes have been filled) because the concrete will tend to crack. ADVANTAGES AND BENEFITS OF UNBONDED POST-TENSIONING By Larry B. 10 mil poly under a slab seams a bit thin now that 20 mil is available for this use. I asked one of the people who worked for Blanford Homes about the crack. Cutting post tension cables can be very dangerous. AMSYSCO places our construction customers' need for outstanding service, quality and responsiveness as a top priority. Usually a sign in the garage or stamp in the slab will indicate if your home has a post tension slab. Once the concrete has gained strength to 2000 psi, typically within the 3 to 10 days recommended by PTI, the tendons are stressed. Yet there are some significant problems with monolithic foundations. As slabs become thinner and spans become longer in residential units, the need to counterbalance the forces and stresses in the slab is provided with post tensioning (PT). Slab Design Example Post-tensioned, un-bonded one-way slab with draped tendons (midspan moments will be assumed to control) , where is the area of the entire section shown above and is the shaded area. To mitigate this problem, post tensioned steel tendons are inserted at the time of concreting and tensioned after concreting with conventional rebars. The main results of a study performed on the influence of the. The main problem with using post tension slab is that if care is not taken while making it, it can lead to future mishaps. The thin post tension slab on grade is not a good solution for the foundation of light. The result is a stiffer concrete member that is being actively compressed and has more capacity to resist tensile forces. As part of a proactive effort, the owner selected the Investigate-Design-Build (IDB) team led by STRUCTURAL and STRUCTURAL TECHNOLOGIES to provide assessment, engineering and solution implementation for the parking structure. - Hard surface, takes a toll on your body/joints - Difficult to run additional wires/pipes - HVAC typically located in the attic (unconditioned space) - A leak in a water supply line in the slab is very expensive to fix - Entrance at ground level, not as eye appealing - High likelihood of radon issue. This can help to minimize cracking and differential settlement in adverse conditions. The purpose of watering a foundation, Ray says, is to keep the soil’s moisture consistent around and under the slab. Many a times, ignorant workers do not fill the gaps of the tendons and wiring completely. Once tensioned, the cables cannot be de-tensioned. ASD vs LRFD. Bowman School of Civil Engineering Purdue University Joint Highway Research Program Project Number: C-36-5600 File Number: 7-4-41 SPR-2151 Conducted in Cooperation with the Indiana Department of Transportation and the U. 1 m thick) is a very good solution for flat surfaces which are not carrying any structures such as tennis courts. Once the tendons were threaded into the ducts, vertical joints were formed and certified PTI (Post-Tensioning Institute) personnel administered circumferential post-tensioning. HVAC air ducts located inside concrete slab floors invite a surprisingly broad range of building problems that fall into two broad categories: functional troubles such as lack of air flow or collapsed ductwork, and environmental problems such as radon, odors, flooding, mold, insects, and where transite - cement asbestos - ductwork was used, asbestos particle contamination. What is a Tendon? Let’s take a look at basically what a tendon is and why it is important. Avoiding Post-Tension Errors Which Result in Cracking Installing the Slip Sheet Incorrectly. Homeowners Are Getting Crushed By Flawed Post-Tension Cable Foundations. They are used to minimize the. As a leading post-tensioning supplier, we are dedicated to provide value with our products and engineering services at competitive prices. Slab-on-grade construction for commercial, institutional, recreational, and industrial floor slab applications use a wide range of design options, including reinforced concrete, unreinforced concrete, post-tensioned concrete, and fiber-reinforced concrete for both structural and non-structural slabs. The way we do this at JEI is by raising the issue in an RFI. It is critical for all cable anchors and post-tension cables to undergo proper maintenance. Effectively, a post-tensioned slab "floats" in the ground, like a cracker on soup. The main advantages of using monolithic slabs are as follows: The slabs can be very sturdy, especially after the addition of steel and fiber mesh. The Post-Tensioning Institute is dedicat­ed to expanding post-tensioning applications through marketing, education, research, teamwork, and code development. Below is a non-exhaustive list of underground services or elements bound in concrete that Construction X-ray can detect:. can help you avoid rebar, post-tension cables, and electrical conduits. - Post tension design for the slabs and beams - Perform Seismic design for the transfer slab Turramura Residential Unit Development Building, Jones Consulting Engineers Pty Ltd, Australia. A Post-Tension Slab DOES NOT, I repeat, DOES NOT need the same treatment a floating slab does. There are various causes of this type of leak, but most of the leaks can be detected visually. Foundation Type 1: Poured Concrete. What is a Post Tension Slab. ARCHITECTS. All concrete cracks it’s just a matter of if the cracks are caused by shrinkage, settlement, or a serious structural problem. The Index of Computer Programmes now maintained in the Institution’s Library contained, at the end of 1962, about 150 items, under the following headings: aircraft and ships (3), arches (3), bridges (13), chimneys (2), composite action (7), continuous beams (7), general mathematical (lo), jetties (3), piles (3), piping (4), plane frame structures (47), plates and slabs (4), properties of sections (9), shells (6), soil mechanics (7), stairs (2), tanks (2), vibration (3) and miscellaneous (10). For the railing post to fail, it must rip the tension tie out of the joist. Also There is a cheaper way than X-ray. Steel cables inside plastic sleeves are run across the floor slab along with regular reinforcing steel where needed before the concrete is placed. They took the most direct path from the nearest gas source (in the laundry room) and exposed seven post-tension cables. The slabs were also made up of eight segments but were not prestressed in the longitudinal direction. So now the home builder is trying to ‘squeeze’ 40 or 60 or more feet of a flat concrete slab plus the attached concrete beams plus the soil between the concrete beams. Flat Slab Analysis, Design and Detailing pdf Flat slab system is an important division of concrete floor system. At the same time, the post-tensioning selected was not to be less than the value necessary for lightly reinforced slabs to meet temperature and shrinkage requirements, and also act satisfactorily as a diaphragm in distributing the. The scope of the seminar includes elevated post-tensioned slabs and beams.