Photo courtesy of PTI, University of Texas at Austin.

A Creative and Cost-Efficient Structural System

What is Post-Tensioning? Post-Tensioning (PT) is a method of reinforcing and prestressing concrete, masonry and other structural elements. Concrete and masonry are very strong in compression, but relatively weak in tension. In comparison, steel is very strong in tension. Combining steel with concrete or masonry, therefore, results in a product that can resist both compressive and tensile forces. Moreover, if concrete is prestressed or ‘squeezed together’ with the help of the steel (known as prestressing steel) during the construction phase, its tensile capacity and resistance to cracking increases. 

There are two methods of prestressing: pre-tensioning and post-tensioning. In pre-tensioning, the prestressing steel is stressed before the concrete is cast, and can only be done at a precast manufacturing facility. With post-tensioning, the prestressing steel is installed on the job site after the formwork and before concrete is poured. It is housed in a sheathing or duct to prevent it from bonding to the concrete. After the concrete has hardened, the prestressing steel is gripped at both ends, pulled and anchored, so as to prestress the concrete. The complete assembly of steel, duct and anchors is known as a tendon. The terms bonded and unbonded post-tensioning refer to the steel and whether or not it is bonded to the concrete after tensioning.

New Technology. Many technological advances have led to PT’s exponential growth since it was first used in the U.S. in 1949. Among them are low relaxation strand, improved analysis techniques and design software, the use of banded tendon distributions in PT floors, extruded sheathing, encapsulated anchors, and most recently, the development of prepackaged, non-bleed grouts for bonded post-tensioning.

Advantages & Benefits. Post-tensioned concrete is a very efficient and cost-effective structural system that has become especially important with the escalation of steel prices. Other key advantages include:

Functional flexibility
Longer spans/reduced structural depth
Lighter structure weight
Structural integrity
Deflection & vibration control
Crack control
Reduced maintenance

Applications. PT is used for a wide range of applications including office buildings, condominiums, hotels, parking structures, slab-on-ground foundations, ground anchors, storage tanks, barriers, nuclear containment structures, stadiums, silos and cable stays. Recent innovations include post-tensioning in pavements, masonry, bridge decks, seismic walls and concrete home construction.

It can be effectively combined with other structural materials and has been used to strengthen steel, masonry and timber structures, and enhance and extend the capabilities of precast, pre-tensioned elements. Examples include spliced precast bridge girders, segmental bridges and hybrid precast moment resisting frame buildings.

About PTI. Formed in 1976, The Post-Tensioning Institute’s (PTI) membership comprises post-tensioning material fabricators, prestressing strand manufacturers, accessory suppliers, contractors and over 700 practicing professionals.

It is the only major association in the world that deals exclusively with post-tensioning technology. Serving as the authority on post-tensioning, PTI is dedicated to expanding PT applications through education, research, marketing and code development, while advancing quality and safety.

Technical committees include: the Technical Advisory Board, Unbonded Tendons, Slab-on-Ground, Cable Stayed Bridges, Grouting, Rock and Soil Anchors, Post-Tensioning Systems, Bridges, Education and Certification.
Over the years, PT structures have performed extremely well. Where problems have been observed, it has often been related to poor workmanship and/or inadequate specifications. PTI has been instrumental in responding to these concerns and developing solutions.

Specifications. Recognizing the need for improved materials, fabrication and construction practices, PTI has worked to develop better specifications. In 1985, PTI issued a specification that has become the standard for unbonded applications. Recently, it published a new grouting specification to improve grouting on bonded post-tensioning.

Plant Certification. PTI has established a certification program addressing quality control and fabrication capability for plants producing unbonded tendons. Forty-one plants—representing over 90% of U.S. production—are now certified.

Photo courtesy of PTI.

Installer Training and Certification. PTI trains and certifies post-tensioning installers. Advanced courses are offered for those seeking further training.

Technical Publications. PTI publishes many authoritative publications with practical guidance on all aspects of PT technology (www.post-tensioning.org.) Many are looked to around the world as the standard of practice. The new PTI Technical Journal provides practitioners and researchers alike with a ready source for in-depth, state-of-the-art information.

Education. A cornerstone of PTI’s new initiatives is education and training for both practicing professionals and undergraduates. The Education Committee is developing programs that facilitate teaching post-tensioning technology at the university level.

PTI sponsors seminars for practicing engineers, architects and contractors. Two seminar series on PT building design and slab-on-ground design are scheduled this fall. PTI’s annual technical conference will be in Denver, May 15-17, 2005.

The Future. As more and more engineers, architects and contractors become familiar with post-tensioning, its use will continue to grow. The versatility afforded by post-tensioning is only limited by the imagination of the designer and the qualifications of the work force.

Comprised of multiple post-tensioning strands housed in ducts, a bonded tendon is designed to form a continuous bond along its length with the surrounding concrete. Bond is achieved by injecting cementitious grout into the tendon after stressing. The hardened grout acts with the duct that is encased in the concrete member to complete the bond path between the post-tensioning strands and the concrete member. Flat, corrugated plastic ducts that house between two and five strands are used in thinner members such as slabs, whereas larger, round ducts (plastic or galvanized metal) are used in beams and girders. Today, bonded post-tensioning systems are the industry standard for concrete bridge construction and are gaining popularity in the parking garage market.

“While monostrand post-tensioning systems have been used in the majority of post-tensioned concrete building applications, bonded systems are becoming more popular with long-term owners such as commercial building owners, airports, hospitals, government agencies and universities, because the annual maintenance costs can be much lower than alternative systems,” notes John Crigler, a senior vice president with VSL, a Maryland-based post-tensioning supplier. “Approximately 3.5 million sq ft of bonded post-tensioning slabs have been installed in the United States in buildings since 1995,” he adds.

Bonded systems offer a significant design advantage that leads to life-cycle savings. The key feature is that the hardened grout locks the movement of the post-tensioning tendons relative to the surrounding concrete. Hence, the force in a bonded tendon is a function of the deformation of the surrounding concrete. This is the well-known concept of strain compatibility and internal equilibrium used in reinforced concrete design. Also, there is no required minimum amount of mild steel reinforcement for flexural members with bonded post-tensioning.

Another design advantage of bonded post-tensioning is the inherent capacity to provide resistance to progressive collapse. This may be especially important in the event of localized blast loading. Like mild steel reinforcement, a bonded post-tensioning tendon is capable of developing its force at a relatively near distance along its length. In the event that an anchorage fails or a strand is severed, the loss of tendon force would be localized. The remainder of the tendon would retain its force at the development length away from the failure point and would remain functional. This functionality may be used in the design phase when planning for alternative load paths.

The most important practical benefit of bonded systems is the reduction of mild steel, particularly at the top of slabs. This is especially important because most parking garage maintenance costs are due to repairs associated with spalled concrete and corroded rebar. Another benefit is complete encapsulation: strands are fully protected by cementitious grout, duct and surrounding concrete. Bonded systems also offer more flexibility regarding structural modifications such as openings for stairwells, utility access and future expansion.

Due to the tremendous growth in the metropolitan D.C area, the Maryland Aviation Administration decided to construct a state-of-the-art parking garage to consolidate the operations of 10 rental car companies for the Baltimore Washington International Airport (BWI). The design involved a cast-in-place concrete system and was based on the desire for enhanced durability and minimized maintenance. The facility footprint included 3.5 million sq ft of parking space and more than 3 million linear ft of VSLAB+® bonded post-tensioning system.

While the project had many special features including fast-track scheduling, the feature that set it apart was the post-tensioning system used specifically to minimize life-cycle maintenance costs.

The durable VSLAB+® system provides total encapsulation of the strands by using high-density plastic duct and watertight mechanical duct to anchorage couplers. Permanent end-caps for both beam and slab tendons are included to completely seal the anchorages. High-performance grout pumped through the tendons provides an additional layer of protection.

STAY-CABLE TECHNOLOGY Cable-stayed bridges demand easy monitoring, stringent durability and corrosion protection. For more than 25 years, VSL has manufactured and installed its cable wedge/strand anchorage systems into over 90 projects. Its advanced SSI 2000 system incorporates multiple independent layers of protection for the prestressing steel.

Unbonded post-tension reinforcing, where the prestressing steel tendon is not bonded to the concrete after tensioning, provides a flexible reinforcing system that meets architecturally complex projects. Post-tensioning can increase span length while not significantly increasing structural framing depth. This reduces the number of vertical framing elements and affords owners and architects more flexibility and usable area when designing interior spaces.

In hotel construction, placing columns between every other room opens up the space in the lower levels where closely spaced columns can interfere with meeting rooms, lobbies and other amenity spaces. The Marriott Surf Club in Aruba used 10 5/8-in.-thick post-tensioned flat-plate slabs to span 39 ft, creating efficient use of floor space while resulting in a flat slab soffit that could be used for the ceiling of the unit below—achieving a reduced building height. Eliminating closely spaced columns also results in foundation savings. Individual footings may be larger, but there are fewer of them, which in most cases leads to a more economical foundation solution.

The 37-story 1000 Main Office Tower in Houston used post-tensioned girders to create a column-free interior floor space in order to maximize usable space while keeping the floor framing system to a minimum depth. The 36-in.-wide by 20-in.-deep post-tensioned girders spanned 44 ft from the perimeter columns to the central core’s vertical shear wall system. Post-tensioning the girders allowed the depth of the girders to be the same as the joists of the floor framing system. This saved both forming costs and concrete materials. It also saved building height and created an uninterrupted plenum space above the ceiling grid for the mechanical and electrical systems.

One of the most popular uses of unbonded post-tension reinforcing is in cast-in-place concrete parking structures. The durability of concrete and the elimination of joints in a cast-in-place post-tensioned floor system reduces maintenance costs and assures owners of long-lasting durable structures. Joints that are necessary in steel and precast systems can result in higher maintenance costs for structures exposed to the environment or corrosive de-icing chemicals.

The 1,676,000-sq-ft Consolidated Rent Car Facility at Phoenix’s Sky Harbor International Airport is a prime example of the benefits that post-tensioning has for long-term owners over other structural systems. The 3-level structure uses 14-in.-wide by 36-in.-deep post-tensioned beams placed at 20-ft centers spanning 61 ft in one direction, and 42-in.-wide by 51-in.-deep post-tensioned pick-up girders spanning 61 ft in the opposite direction—thus creating a very large 61-ft square column spacing. The post-tensioned slabs spanning between the post-tensioned beams is 5 1/2-in. thick. Suncoast Post-Tension supplied 2.4 million lb of 1/2-in.-diameter unbonded encapsulated tendons for the facility which is scheduled for completion in 2005.

In recent years, the majority of post-tensioning steel consumption has been in unbonded post-tension reinforcement of slab-on-ground foundations. Ribbed foundation systems used primarily in the Southwest are comprised of down-turned ribs ranging from 8 to 12-in. wide by 20 to 36-in.-deep with 4 to 5-in.-thick slabs.

Slabs of uniform thickness used primarily in the western portion of the U.S. do not use downturned ribs and typically range from 7 1/2 to 16-in. thick. The post-tensioning generally provides between 50 to 100 psi of compression. Both the ribbed and uniform thickness foundations have proven superior in performance and cost savings compared to traditionally constructed foundations. In 2004, Suncoast will provide materials and services for over 100,000 single-family residential foundations in the West and Southwest, plus several million sq ft of multi-family, commercial, industrial and sports court projects throughout the U.S.

Since 1983, Suncoast Post-Tension has provided post-tensioning materials, engineering, equipment and field services to contractors across the U.S. In 2001 it was acquired by London- based Keller Group plc. Suncoast, headquartered in Houston, TX, provides materials and services from nine strategically located PTI Certified Plants while maintaining a close relationship with local engineers and contractors from 14 operating offices.

Post-tensioning is a proven solution to the problems associated with ground-supported residential foundations on expansive soils. Ground-supported concrete foundations can be stiffened by non-prestressed reinforcement or by post-tensioning. For non-prestressed reinforcement to work, the concrete must deflect and crack before the steel comes into play. The post-tensioning system compresses the concrete, creating stresses that resist anticipated tension stresses induced by soil movements. Where many non-prestressed concrete foundations are not required to conform to published design standards, the majority of post-tensioning designs conform to the design criteria established by the Post-Tensioning Institute (PTI).

The original PTI design manual was published in 1980. It was based on years of research and development at Texas A&M University, and was reviewed and endorsed by representatives from the post-tensioning industry, the federal government (HUD-FHA), the U.S. Army Corps of Engineers and National Association of Home Builders. A second edition was published in 1996 and a third edition is currently in development using a consensus procedure by the slab-on-ground committee of PTI, chaired by Kenneth B. Bondy, P.E. In the third edition, the construction recommendations have been removed and published as a stand-alone document. Also, two companion documents are being developed in mandatory code language for incorporation into model building codes. Bondy says, “The 3rd edition incorporates state-of-the-art methods for determining internal forces and deformations in shallow concrete foundations, prestressed or non-prestressed, built on expansive clay soils. We anticipate this document will soon be widely codified and will become the standard of care for analysis and design of all types of residential foundations on expansive soils.”

In many areas, expansive clays are vulnerable to significant volumetric changes induced by moisture variation. The microscopic clay particles have the ability to attract and hold water to their surfaces. The attraction of available water during the wet seasons and loss of moisture during the dry seasons results in cycles of shrinkage and swelling. Moisture variations also occur when foundations are constructed over dry soils as moisture naturally moves into the covered dry soil causing it to swell.

A typical post-tensioned foundation on expansive soil consists of a monolithic “ribbed” foundation with a 4-in.-thick slab, a perimeter beam and interior beams spaced in both directions at 10 - 15 ft. maximum centers. A typical post-tensioned foundation on less expansive soil consists of a monolithic uniform thickness foundation, sometimes called a “California slab,” with a minimum 5-in.-thick solid slab with a perimeter beam and no interior beams or a minimum 7.5-in.-thick solid slab with no perimeter or interior beams. Post-tensioning is accomplished using 0.5-in. monostrand tendons distributed in both directions, initially stressed to 33,000 lb, to provide a residual compressive stress of approximately 50 - 100 psi. The compressive stresses resist the anticipated tension stresses induced by the soil movements, enhancing the performance over a typical non-prestressed foundation.

In addition to increased strength, cost benefits are typically achieved by reductions in quantities of concrete, steel and excavation which in turn reduce labor costs. B. Nelson Mitchell, Jr., president of History Maker Homes, Dallas-Fort Worth, notes, “Our company has been building affordable homes for four generations, since 1949. For 25 years we have chosen to use post-tensioned foundations because of the value proposition it offers. Post-tensioning gives us high quality at an economical price.”

The slab-on-ground market is the fastest-growing segment in the post-tensioning industry. According to PTI, slab-on-ground material shipments have increased an average of 13% per year over the last decade, with approximately 320,000 homes constructed in 2003 utilizing post-tensioning. In addition to residential construction, other applications include industrial, commercial, sport courts and paving. What started in Texas in the mid ’70s has spread throughout the southern U.S., in key home building states of California, Florida, Arizona, Nevada and others, as builders, contractors and engineers discover the inherent benefits of post-tensioning.

Text and photography by Jack W. Graves, Jr., President/Managing Partner, GSI Post-Tension, Dallas-Fort Worth, TX.

This is one of the largest cast-in-place post-tensioned garages in the U.S. An unbonded monostrand post-tensioning system was chosen for its economical life-cycle cost, speed of construction and long-term durability. The architect and structural engineer of record were the Cunningham Group and Palanisami & Associates Inc., respectively.

The framing system consists of 7-in. slab, spanning 27 ft, over 16 by 33-in. beams. The beams span 55 ft. The structure has a total of four helical covered ramps for efficient entry and exit. These helixes have post-tensioning tendons in the radial direction.

AMSYSCO Inc. of Addison, IL, supplied 4.6 million ft of tendons over a period of 17 months to M. A. Mortenson Co. of Minneapolis, the project's general contractor. Steve DeGroote, the senior executive of M. A. Mortenson Co. in charge of construction, says, “This project was an ideal application of post-tensioning. It provided the space savings, performance and cost benefits the project needed. The project's aggressive schedule was coupled with significant liquidated damage provisions. Our post-tensioning supplier, AMSYSCO, was a great asset in successfully completing the project on schedule. Their systems met the specifications and were delivered on time.”

POST-TENSIONING HELPS CONDO DEVELOPER MEET COST GOALS

In looking for a way to translate an architect’s vision for a highly styled condominium building into the project’s budget, a post-tensioning system was found to be the solution. The Village Green Condominium structure in Arlington Heights, IL, has won high praise from building residents and the community.

In view of the complicated layout of columns and other requirements, the original framing utilized a 10-in.-thick concrete slab with many beams. This system was driving up the cost of the structure. For a solution, the construction team called AMSYSCO Inc. AMSYSCO developed a new approach using a 6.5-in.-thick post-tensioned flat plate—eliminating all beams and thereby reducing the cost of the structure.

The redesign was executed concurrently with the actual construction and continuous architectural enhancements, allowing the original construction schedule to be met. AMSYSCO assisted the construction team in developing complete structural design and drawings. Although only six floors, a post-tensioning system proved its value to the project.

TWENTY-STORY HOUSING MAKES THE GRADE

The University Center of Chicago provides housing for 1,723 students who attend DePaul University, Roosevelt University and Columbia College University. The construction and design team of Turner Construction Co., Antunovich Assoc. V.O.A., and Chris P. Stefanos Associates, chose a post-tensioned concrete frame for the 20-story building.

Above the plaza level, the framing system consisted of a 9.5-in.-thick flat plate with no drop heads or beams. The PT tendons were installed in banded and uniform pattern. Spans varied in dimensions with a maximum span of 32 ft.

The ‘E’ shape of the structure, with the longest dimension of 355 ft, presented a few construction and design challenges on the thermal expansion and rapid construction schedule. AMSYSCO, the post-tensioning supplier on the project, worked with Adjustable Forms Inc., the concrete shell contractor, in developing a solution. Expansion joints were eliminated and the building was constructed as two independent structures.

A 10-ft-wide pour strip separated each structure, which was left open until both sections of the building were completed and thermally controlled. This option allowed dissipation of all elastic shortening and considerable shrinkage of the two separate sections. The operations manager of Adjustable Forms, Scott Kennedy, says, “The structural modification allowed us to place 1,285 cu yd of concrete, and finish 34,012 sq ft of typical supported work every week. This gave Turner Construction two months of additional-time to complete their finish trades, ensuring an on-time completion for the students.”

Toronto Ariport

In the past several years there have been few instances of Canadian owners selecting unbonded post-tensioning for projects, for reasons mostly concerned with fear of corrosion. It is therefore interesting to note that DYWIDAG®’s parking garage for the Lester B. Pearson International Airport in Toronto has both bonded and unbonded systems.

Part of the airport’s redevelopment is the Terminal Development Project. Obsolete Terminals 1 and 2 will be replaced by a new single terminal building capable of handling 50 million passengers per year. Included in the package is the parking garage with a capacity of handling 12,500 vehicles plus road access.

For the cast-in-place beams DYWIDAG® used bonded multistrand tendons, because their efficient design and compact size fit efficiently into highly congested reinforcing steel. But for the cast-in-place slabs of the parking structure, the company selected its new Zero-Void® monostrand unbonded tendons. Used for the first time, the new system, with its superior corrosion protection, met stringent water-tightness tests.

INSPECTING AND STRENGTHENING

Downer’s Grove, IL

Stanley Hall

Post-tensioning can be inspected and strengthened without demolition. In early 2003, DYWIDAG® was awarded the job of inspecting a set of four precast segmental bridges at the I-88 and I-355 interchanges in Downers Grove, IL, managed by the Illinois State Toll Highway Authority.

The scope of work consisted of preparing and implementing an inspection plan tailored to the different types of post-tensioning tendons present in the structures. DYWIDAG®’s Repair and Strengthening Business Unit organized the plan into five phases: a visual inspection, nondestructive testing using ground penetrating radar and impact echo, invasive inspection and vibration techniques.

The final report report noted that the bridges are an example of well-built structures, despite the relative weakness of corrosion protection and grouting specifications in use at the time. Recommendations are currently under review. Meanwhile, DYWIDAG®’s repair unit is well positioned for future bids on inspecting precast segmental bridges.


A REPLACEMENT BRIDGE

The Victory Bridge carries Route 35 over the Raritan River between Perth Amboy and Sayreville in New Jersey. Built in 1926, it was in an advanced stage of deterioration, had very narrow lanes and a low vertical clearance of just 29.5 ft. The swing span bridge needed to be replaced with a new crossing which increased the vertical clearance over the channel to 112 ft.

To be finished early next year, the new bridge constructed by DYWIDAG® will consist of two parallel concrete segmental structures each 4,000 ft long with a 440-ft precast match-cast main span, two 330-ft back spans and a series of approach spans varying in length from 140 ft to 151 ft.

The substructure has 22 piers with two abutments each. Each pier will be constructed from precast concrete hollow box sections that are post-tensioned together. The tendon configurations included 12 and 19 epoxy- coated .6-in.-diameter strands plus .6-in.-diameter high-strength prestressing bars.

The superstructure consists of precast concrete segmental box girders. The approach spans will be erected by the span-by-span method, while the main span will be erected by the balanced cantilever method. The approach spans with a typical length of 151 ft use 4 .6-in.-diameter internal flat tendons in the top deck to provide a long lasting durable riding surface. Five 19 .6-in.diameter external tendons per side are being used for the longitudinal post-tensioning.

Photo courtesy of PTI, Robert B. Anderson Constulting Engineers.

Citing the advantages of post-tensioning installed in three of its most recent condominium projects, PTE Strand lists a number of cost-saving details. All three buildings are in Miami: the 50-story Jade Residence and the 41-story Brickell Bay Plaza under construction, and the recently completed 34-story Brickell Bay Village.

The first saving is in the height of the building. If the structures had conventional rebar construction, the slabs would have to be 10 in. thick. By using post-tensioning, they need only be 8 in. thick, which, for the Jade Residence, reduces the height by 8 ft. It also reduces the cost of the foundation because fewer piles are needed.

Photo courtesy of PTI, International Bridge Technologies.

The second saving is in speed of construction. Instead of a 14-day or more cycle for the rebar method, post-tensioning takes three days to complete a cycle. On the first day steel cables are laid with anchors attached. The slab is poured the second day and allowed to cure while the process is repeated on the floors above. Cables are stressed and anchored on the third day, and the forms removed.

A third advantage is that because the concrete is under compression, there is minimal cracking while it cures. Maintenance costs will be less than if the buildings had rebar construction which has a higher likelihood of corrosion resulting from water infiltrating through cracks.

Another advantage is relative ease of repair. If a cable breaks—usually because of drilling through the slab—it is pulled out and measured. After determining where the break is, the concrete is chipped away, and the new cable inserted, coupled with the old, and prestressed.

Founded in 1979 and based in Miami, PTE Strand has completed post-tensioning projects on the east coast from Florida to Massachusetts, for parking garages and bridges to high rise buildings.

Post-tensioning proved an efficient solution to delivering slabs with an irregular column layout for the Suwaidan Complex in Sharjah, United Arab Emirates. Rather than specifying reinforced concrete floors, Emirates Post-Tension, the UAE affiliate of PBL Group Ltd, designed a secondary and tertiary banded post-tensioning system that provided a straightforward load-transfer mechanism.

The complex consists of three 41-story towers connected at the base by a five-story parking structure. PBL Group Ltd, whose headquarters are in Bangkok, Thailand, supplied the post-tension anchorage and hardware.

A similar post-tensioning system was delivered by Emirates Post-Tension for the city’s tallest structure, the Al Salam Tower located on the exclusive waterfront. Slab thickness for typical floors is 7.87 in. and tendons are a 4-strand bonded system encased in flat duct. Developed by Omram Global, the nearly 700-ft tower has luxury apartments, penthouses, and a helipad.

As consultant to B.B. Bar Company Ltd., the PBL Group provided post-tension anchorage and hardware plus several of their own installers for Phase l of the 2006 Asian Games Village. Owned by the Emirate of Qatar, the 31 buildings should be completed by year’s end.

Chucks, wedges and anchors are essential components in the post-tension industry, and the companies who manufacture them play a significant role. Formed two years ago, Precision Post Tension, LP (PPT)—its predecessor was Precision Screw Products—offers the widest selection.

Wedges are critical components in post-tension anchorage systems. They must meet precise dimensional and physical characteristics to mate with the anchor and grip the strand properly. The company sells the most and the broadest variety of wedges under the Sure-Lock® brand name, for use in both one-time and multiple-use applications. They are precision machined from high-quality steel, dimensionally inspected at each stage of the manufacturing process, and carefully tracked and controlled through heat-treatment processes, with each lot audited twice to assure the proper hardness range is provided.

Exports are a large part of PPT’s business. “We regularly ship to more than 25 countries, and have virtually every major post-tensioner buying from us,” says ceo Bob Van Noord.

Constrained by the human desire to stick to what is known, New York area developers have shied away from post-tensioning systems. Now, with the foresight and determination of Local 46 Metallic Lathers and Reinforcing Ironworkers, that may soon change.

Business manager and financial secretary treasurer Robert Ledwith has adopted a simple strategy: create a demand for cost-effective post-tensioning by first training a fleet of workers. Using its own new center in Queens, the 1,200-member union has already graduated 200 workers and will have 300 by year’s end—all certified with the out-of-state imprimatur of PTI.

With workers now demonstrating they can deliver up to 20,000 sq ft in an astonishing 2-day cycle for a 14-story apartment building in Queens and a 37-story high rise in White Plains, Ledwith is now convincing architects, contractors, owners and developers. “We’re pleased to support the union,” states Michael A. Russillo, president of Barker Post-Tensioning LLC. “We want to bring the benefits realized in other major markets to the New York area.”

Meanwhile, Ledwith is building a liaison with affordable housing developers. Three projects will be completed using traditional reinforcing methods. The next two will demonstrate the competitive advantages of post-tensioning with longer spans.