By Corey Rogers, P.E., Photos courtesy of MDOT (michigan.gov/mdot)

The Michigan Department of Transportation (MDOT) uses a Prefabricated Bridge Element Systems (PBES) approach under its Accelerated Bridge Construction (ABC) policy. Rapid bridge construction means less inconvenience and delay for the public, businesses and transportation users. Construction details and challenges encountered on two projects with multiple precast concrete bridge elements led to important improvements for the PBES approach going forward.

PBES Bridge Project 1: Parkview Avenue over
U.S. 131 substructure – smooth sailing in six-week schedule

In 2008, the Michigan Department of Transportation (MDOT) began PBES construction on Parkview Avenue Bridge over U.S. 131 in Kalamazoo County. The challenge was to build a 249-ft, four-span bridge on a 23-degree skew in 12 weeks. The solution was precast concrete elements. Time was of the essence, and an ambitious schedule was proposed to mitigate the impacts to traffic in this populated area of Kalamazoo.

The first six weeks of construction involved demolition of the existing structure and construction of the substructure. The substructure design was semi-integral, comprised of a single row of HP 12 x 53 H-piles supporting the precast abutment stems. The piers were supported by cast-in-place (CIP) spread footings. The CIP footings, concrete diaphragms, back wall and bridge railing were the only elements of the bridge cast in the field.

After demolition of the existing structure, the pier footings were cast. In order to ensure proper fit-up of the columns and the footings, a block-out template was created detailing the location of the threaded rod inserts in the bottoms of the columns and used to lay out the voids in the footings for the footing-to-column connections. After the footing concrete reached a compressive strength of 2,500 psi, the threaded rods were inserted into the bottoms of the columns, and the columns were set over the respective voids in the footings. The voids were grouted and the connections completed. The tops of the columns did not utilize the threaded inserts but had the connecting resteel precast with the columns to match the corrugated ducts in the pier caps. The corrugated ducts were then grouted after fit-up to complete the column-to-pier cap connections.

The abutment stems were precast, incorporating pile sleeves. In this regard, the pile driving operation and location tolerances were critical, and the contractor ensured all the pile sleeves in the abutments lined up appropriately. The sleeves were then grouted and allowed to reach a compressive strength of 3,000 psi before beginning the erection of the superstructure. The PBES allowed MDOT to complete the substructure within the six-week schedule by eliminating forming, large pours, sequencing and lengthy cure times – essentially reducing it to a grouting operation.

PBES Bridge Project 2: M-25 over the White River-two weeks ahead of schedule

M-25 over the White River is located along Lake Huron on the east coast of Michigan’s thumb in Huron County. Due to scour concerns and existing conditions, the bridge was programmed for replacement in 2011. This route is frequently traveled by tourists seeking recreational activities such as boating, fishing and camping. In order to reduce impacts to traffic and mitigate negative impacts to the local businesses, ABC techniques were a primary objective for MDOT.

A prefabricated bridge element system utilizing precast concrete abutments and precast decked box beams was chosen to expedite construction of a 48-ft-long, single-span bridge. MDOT’s first experience with decked box beams presented some unique challenges but resulted in a very successful project. Conventional CIP construction would have resulted in a 20-week closure of M-25. The goal of the White River Bridge replacement was a construction schedule of 12 weeks, which was achieved through the use of precast elements.

Conventional construction requires forming, placing and curing concrete in the field. Structural concrete must reach an acceptable strength prior to loading and moving on to the next stage in construction. MDOT specifications for bridge deck pours require a seven-day wet cure prior to loading and subsequent concrete pours. The use of precast decked beams eliminates the need for a seven-day wet cure, significantly reducing time on projects where every day counts.
The reinforced precast concrete segments consisted of two abutment stems, two wing wall segments, two slope walls and eight beam-deck segments. All were fabricated in an off-site precast plant and trucked to the job site.

The existing White River Bridge was removed and the footings were cast. After reaching a 2,500 psi compressive strength, the precast abutment segments were lifted into place with a 500-ton crane and positioned on the footing. The abutment stem segments and wing walls were connected to the footing with non-shrink, grout-filled mechanical splices. The vertical key between the two abutment segments was grouted, and the closure pour between the wing walls and the abutments was completed. Each abutment was assembled in one day.

The modular decked box beams were comprised of 21-in. prestressed box beams pre-topped with 10½ in. of deck. Typical bridge decks are approximately 9 in. thick; however, additional deck thickness was included to allow for deck surface corrections and ride quality of the structure. The beam-deck segments were spaced 6 ft on center and rested on the abutments via elastomeric bearings. Between each modular section, top and bottom longitudinal reinforcement was threaded through the overlapped D-hoops within the closure pour block-out.

The beams were preloaded to reduce variations in camber among the beams to ensure a smooth transition at the closure pour joint. High Performance Superstructure Concrete (HPSC), capable of attaining 7,000 psi compressive strength, was used for the closure pours between beam-deck segments. Transverse post-tensioning tendons comprised of four ½-in.-diameter strands were installed in 5-in. ducts cast into the six diaphragms of the modular sections, stressed to 182 kips and grouted with HPSC.

Upon removal of the preloading, irregularities were still present in the deck due to slight camber variations and imperfections from lifting-loop locations. The deck was diamond-ground and coated with a thin epoxy overlay to improve aesthetics and ride quality, and provide a waterproof barrier. The project was completed in 10 weeks – two weeks ahead of schedule, and proved to be another successful endeavor utilizing precast concrete elements.

Post-construction lessons learned

The collaboration between MDOT and the contractor was remarkable. Innovations and efficiencies made in the field during construction and recommendations to improve similar types of construction in the future were discussed. The MDOT Cass City Transportation Service Center managed the project and detailed all facets of the project, including a post-construction meeting that focused on recommendations for future improvements.

Recommendations brought forward
after construction:

1. Verify the availability of HPSC near the project location, especially in rural and remote project locations.
2. Use recessed lifting loops on the precast segments. Recessed lifting loops eliminate the need for cutoffs and allow for easy mortar patching and increased longevity of the patch.
3. Eliminate the preloading guesswork. A table estimating the required preloading, based on a given camber deflection, would assist contractors in obtaining materials and expedite the preloading process.
4. Create a strength-testing procedure for expansive grouts.
5. Use a Qualified Products List or testing to verify required strength throughout the construction process. Contractors may not be familiar with the process to create and test the cubes necessary for grout testing.
6. Use a thin epoxy overlay. Although the deck was precast 1½ in. thicker to accommodate the need for grinding imperfections, grinding often results in an unattractive deck appearance, micro-cracking and loss of the densified top layer of protective concrete. A thin epoxy overlay seals the deck and provides an aesthetically pleasing wearing surface.

PBES going forward

On the Parkview Bridge Project, MDOT implemented the PBES philosophy using multiple precast bridge elements, thus laying the foundation for future precast projects throughout Michigan. Ultimately, a bridge replacement that typically would have taken about seven months to complete was finished in about five months, even though the deck panel error resulted in a two-month delay. But more importantly, MDOT gained invaluable experience in PBES construction and techniques related to proper prefabricated element fit-up.

The efforts put forth by MDOT project staff and the contractor to document the positives and negatives of these projects are a huge asset to the department. The successes and the lessons learned validated the effectiveness of precast concrete bridge elements and have allowed MDOT to develop a PBES implementation policy with guidance on future project selection. By sharing lessons learned statewide, future decision making is improved and the effectiveness of precast elements can be utilized to the greatest benefit for both MDOT (in terms of quality construction) and the public (in terms of reduced impacts and delays).

Precast concrete elements have earned their place in bridge construction, and as engineers become more comfortable with their use, precast systems will surely become a standard building block for MDOT.

Corey Rogers, P.E., bridge construction engineer, bridge field services division, MDOT, is responsible for creating alignment in bridge construction practices, troubleshooting construction related issues and implementing new innovations in bridge construction on a statewide basis. Contact him at
RogersC5@michigan.gov.

I’ve still done my fair share of forecasting in the three years since then, but you may have noticed a slow-building positive trend in my rhetoric lately. It’s cautious optimism because we’re on firm(er) ground, with a more realistic path to recovery.

Despite the futility in Washington, ongoing uncertainty about regulations and taxes, and the slow nature of the recovery, the U.S. can only go so long without a meaningful investment in our roads, bridges, water and wastewater systems, and so on. Our infrastructure, which was once the benchmark all other countries strove for, has tumbled all the way to 25th on the World Economic Forum’s Global Competitiveness Report.

Lawmakers should ponder this, along with the fact that we are being outspent by China and other emerging economies big time when it comes to infrastructure. If we continue to ignore infrastructure, we risk national health, safety and economic growth. They simply cannot ignore it much longer. They’ll find a way to fund infrastructure work. When they do find a way to fund it, we’ll be waiting because we are the infrastructure people.

As investments are made in real, dirt-moving projects, there will be need for precast concrete – and lots of it. Are we ready as an industry? Are you ready as a supplier? I hope so. We know we have the best products for the job, now we just need to make sure the right people know that as well.

Ty Gable
President, National Precast Concrete Association

By Thomas G. Zink, P.E.
Photos Courtesy of Gannett Fleming Inc. (www.gannettfleming.com)

Modern materials and precast concrete components have been blended with turn-of-the-century architecture to create a truly unique structure recently constructed in central New Jersey.

The George Street Bridge is one of several structures included in the New Jersey Department of Transportation’s (NJDOT) Route 18 Improvement Project in the City of New Brunswick. The project consists of the construction of a collector/distributor roadway adjacent to the existing mainline to separate local traffic from through traffic in an effort to reduce congestion and improve safety within the corridor. However, the vision for this project extended well beyond conventional highway considerations as the NJDOT recognized the role this project would play in enhancing the urban redevelopment currently taking place in the project vicinity.

Connecting a city to its waterfront
Supporting 85,000 vehicles per day, the existing Route 18 roadway separated the historic city from the underutilized parklands situated along the Raritan River. Working with its design consultant, Gannett Fleming Inc., NJDOT sought to provide the missing connectivity between the city and its waterfront properties. As part of the Context Sensitive Solutions initiative, NJDOT created a Community Partnering Team (CPT) that would help steer the project in a manner acceptable to all major stakeholders including city officials, Rutgers University, Johnson & Johnson and nearby neighborhood associations.

At the southern end of the project, the George Street Bridge serves as the entrance to the new collector/distributor roadway, carrying local traffic over a portion of the riverfront parkland. At its crest, a signalized T-intersection permits local traffic and pedestrians to safely cross above the express lanes. The resulting T-shaped bridge measures approximately 600-ft long by 60-ft wide for the main portion located above the park. A single 135-ft-long span forms the portion over the mainline.

During the design process, both steel and concrete alternatives were evaluated for the new structure. However, feedback indicated a strong desire from the community for the new bridge to blend in with the architecture of the surrounding structures, many of which were vintage concrete and masonry arch bridges. With CPT guidance, Gannett Fleming worked with NJDOT to evaluate alternatives that would be visually compatible with nearby architecture.

Concepts included conventionally constructed stringer configurations with ornamental “faux-arch” appurtenances, haunched steel plate girders and long-span precast concrete arches. Ultimately, the precast concrete arches were selected for their durability, reduced life-cycle costs and aesthetic compatibility with the surrounding structures. However, the single span over Route 18 required a steel multi-stringer configuration due to limited available structure depth and the need to flare the beams at the intersection.

A first: precast arches and lightweight cellular overfill
The precast concrete arches are supported by multi-column piers, with each pier consisting of three 6-ft-diameter drilled shafts with a cast-in-place (CIP) concrete cap beam. A multi-column configuration allowed the space below the bridge to be utilized for vehicular circulation, thereby maximizing useable park space. However, this presented a unique challenge to the design team, as the arches required about 12,330 cu yd of overfill material, and supporting such mass on relatively slender columns created difficult loading conditions, particularly with respect to seismic forces.

To reduce the structure’s mass, an engineered flowable fill consisting of a lightweight cellular concrete mix with a density of 30 lb/cu ft was specified for the overfill material. This significantly reduced dead load and seismic forces on the piers when compared with the use of a more traditional soil overfill weighing three to four times as much. The George Street Bridge is unique in that it was the first structure of its kind, combining precast concrete arches with a lightweight cellular concrete overfill.

Precast barrel arch construction method
The project was awarded to The Conti Group of Edison, N.J., in 2005. As one of the last elements constructed under this contract, the erection of the precast concrete arch components at the George Street Bridge did not commence until June 2008. Conti constructed the eight precast concrete barrel arches using the TechSpan system furnished by The Reinforced Earth Company of Vienna, Va. Each arch spans 66 ft and has a vertical rise of 20 ft.

A twin-leaf configuration minimized shipping dimensions and pick weights. Each barrel arch required 16 precast pieces comprised of 5,500-psi concrete. At the crown of the arch, the precast pieces were mated using a CIP concrete closure pour in a preformed keyway. The TechSpan components were designed as three-hinged arches using finite element software to compute horizontal and vertical forces in each piece. Helser Industries of Tualatin, Ore., fabricated the steel forms so that Precast Systems Inc. of Allentown, Pa., could cast the pieces.

To expedite their placement and to eliminate the need for a second crane, each arch piece was lifted from the delivery truck and rotated into position in a single step. Adjustable-height hydraulic shoring towers provided temporary support at mid-span until the first four pieces were placed. Once the pieces were self-supporting and stable, the shoring towers were removed and relocated for reuse at the next span. Work continued on each barrel until all 16 arch pieces were installed. This placement method allowed Conti to complete arch barrel in two days.

Steel tie rods were installed between adjacent pier caps to stabilize them against excessive deflections due to unbalanced thrust loads developed during construction. This was done to ensure a proper fit for the precast concrete spandrel panels that were placed on the arches to contain the backfill material. The spandrel panels were cast with a cut-stone form-liner finish and were held in place with metal straps similar to those used on mechanically stabilized earth (MSE) walls. The project specifications provided limitations on the differential height of the overfill material between adjacent arch valleys to minimize differential thrust forces.

Precast concrete was also incorporated into other components of the structure. MSE retaining wall panels were used in all four approaches. Similar to the spandrel panels, the MSE panels were cast with form-liner finishes. Edge chamfers were eliminated from the precast panels to minimize the visual appearance of the panel joints, which further enhanced the faux-stone textures that replicate traditional masonry. Custom spray-on color, based on mock-up approval, was applied to the precast stone finish to give the George Street Bridge its authentic “turn-of-the-century” architectural stature.

Precast replaces CIP parapets

Conti opted to precast the bridge parapets as well. The parapets contained numerous architectural details and were fully detailed in the bid documents as CIP concrete elements. However, by utilizing adjustable forms in the precasting yard, Conti was able to achieve all desired aesthetics and met profile requirements using precast concrete parapet modules. Even though the bridge was constructed on a crest vertical curve, the parapet modules were fabricated and placed so that all pilasters and simulated balustrade patterns were plumb in their final condition. Although such details were not conducive to standardization and numerous parapet module variations were required, Conti found this precasting method to be more cost effective than CIP construction.

The bid documents required the contractor to construct full-scale mock-ups for various structural and architectural components, including formlined MSE panels, simulated balustrades, metal fencing and sidewalk treatments. The mock-ups helped the contractor identify fit-up and alignment issues and find ways to adjust construction techniques to improve quality while expediting construction. Final production work was not permitted until the mock-up panels were approved. After approval, the mock-ups served as a performance standard for all production work.

A level playing field: comparing steel and precast solutions
The total cost of the George Street Bridge was $11.6 million. This includes $9.6 million to construct the 36,000 sq ft of precast concrete arch structure over the waterfront park and $2 million to construct the 7,860 sq ft of steel girder/concrete deck structure over Route 18. This equates to a unit price of $266/sq ft for the arch bridge and $261/sq ft for the steel span.

This finding is of particular significance as both the steel and the concrete portions of the bridge were built at the same time, by the same contractor, on the same site and utilized the same architectural surface treatments. These similarities provided a unique opportunity to validly evaluate the cost of providing a “non-conventional” structure type to that of a more traditional design. On a square-foot basis, the precast concrete arch portion of the bridge was just under 2% more expensive to construct than the steel portion of the structure. However, without need for a paint system, bearings or joints to maintain, the life cycle cost of the precast concrete arch bridge is substantially less than a steel bridge alternative. The durability of the precast solution and its substantially lower life-cycle costs made this a very attractive solution for a very modest increase in initial cost.

A unique application, the use of long-span precast concrete arches with a lightweight cellular concrete overfill represents an engineering innovation that proved economical and exceeded the expectations of the client and the community. In addition, this structure was awarded the Eugene C. Figg Jr. Medal for Signature Structures at the 2010 International Bridge Conference for a “single recent outstanding achievement in bridge engineering that through vision and innovation provides an icon to the community for which it was designed.”

Thomas G. Zink, P.E., is a vice president of Gannett Fleming Inc. and serves as regional bridge practice manager in the northeast as well as the manager of the transportation division in Mount Laurel, N.J. With 20 years of experience in bridge design and rehabilitation projects, Zink was the lead structural engineer for NJDOT’s Route 18 Reconstruction Project.

To appreciate precast concrete’s contribution to the George Street Bridge project in historic New Brunswick, N.J., one look at the outstanding architecture of the finished structure will suffice. A completed project photo shows how precast concrete design plays a big role in delivering classic architecture and community connection to a riverfront park.
The main goals of the New Jersey Department of Transportation (NJDOT) improvements to Route 18 were to facilitate the flow of traffic, reduce congestion (85,000 vehicles per day), and improve road safety. But in addition to serving its primary transportation functions, the new George Street Bridge goes beyond the call of duty in contributing to the quality of life in the city.

Using the new bridge to connect the city with its waterfront in the most acceptable way possible to the Community Partnering Team (CPT) was part of NJDOT’s Context Sensitive Solutions Initiative. The CPT was comprised of city officials, Rutgers University, Johnson & Johnson and nearby neighborhood associations, all of who wanted to see a pleasing pedestrian link to the underutilized parklands along the Raritan River.

Both steel and precast designs were evaluated
During the design process, both steel and concrete bridge solutions were evaluated. Community feedback indicated a strong desire for the new bridge to blend in with the vintage architecture of the surrounding structures, many of which were concrete and masonry arch bridges. With CPT guidance, design consultant Gannett Fleming worked with NJDOT to evaluate alternatives that would be architecturally compatible.
Ultimately, precast concrete arches were selected for their durability, reduced life-cycle costs and architectural aesthetics. The single span over Route 18, however, required a steel multi-stringer configuration due to limited available structure depth and the need to flare the beams at the intersection.

A first: precast arches and lightweight cellular overfill
The precast concrete arches are supported by multi-column piers, with each pier consisting of three 6-ft-diameter drilled shafts with a cast-in-place (CIP) concrete cap beam. A multi-column configuration allowed the space below the bridge to be used for vehicular flow, thereby maximizing useable park space. However, this presented a unique challenge to the design team, as the arches required about 12,330 cu yd of overfill material, and supporting such mass on relatively slender columns created difficult loading conditions, particularly with respect to seismic forces.
To reduce loading, an engineered flowable fill consisting of a lightweight cellular concrete mix with a density of 30 lb/cu ft was specified for the overfill material. This significantly reduced dead load and seismic forces on the piers when compared with the use of a more typical soil overfill weighing three to four times as much. The George Street Bridge is unique in that it was the first structure of its kind to combine precast concrete arches with a lightweight cellular concrete overfill.

Precast barrel arch construction method
The Conti Group, general contractor for the project, erected the precast arches for George Street Bridge in June 2008. Each arch spans 66 ft and has a vertical rise of 20 ft.

A twin-leaf configuration minimized shipping dimensions and pick weights. Each barrel arch required 16 precast pieces comprised of 5,500-psi concrete. At the crown of the arch, the precast pieces were mated using a CIP concrete closure pour in a preformed keyway. Helser Industries of Tualatin, Ore., fabricated the steel forms so that Precast Systems Inc. of Allentown, Pa., could cast the pieces.

To expedite placement using one crane, the arch pieces were lifted from the delivery truck and rotated into position in a single step. Adjustable-height hydraulic shoring towers provided temporary support at mid-span until the first four pieces were placed. Once the pieces were self-supporting and stable, the shoring towers were removed and reused at the next span, allowing Conti to complete one arch barrel in two days.

Steel tie rods installed between adjacent pier caps stabilized them against excessive deflections during construction and ensured a proper fit for the precast spandrel panels placed on the arches to contain the backfill material. The spandrel panels were cast with a cut-stone form liner finish and were held in place with metal straps similar to those used on mechanically stabilized earth (MSE) walls.

Precast MSE retaining wall panels were used in all four approaches and were cast with form liner finishes. Edge chamfers were eliminated from the precast panels to minimize the visual appearance of the panel joints, which further enhanced the faux-stone textures that replicate the city’s traditional masonry. Custom spray-on color, based on mock-up approval, was applied to the precast stone finish to give the George Street Bridge its authentic “turn-of-the-century” architectural stature.

Precast replaces CIP parapets
Conti opted to precast the bridge parapets as well. The parapets were fully detailed in the bid documents as CIP concrete elements. However, by utilizing adjustable forms, Conti achieved all desired aesthetics and met profile requirements using precast parapet modules. Even though the bridge was constructed on a crest vertical curve, the parapet modules were fabricated and placed so that all pilasters and simulated balustrade patterns were plumb in their final condition. Although such details were not conducive to standardization and numerous parapet module variations were required, Conti found this technique to be more cost effective than CIP construction.

Full-scale mock-ups were required for various structural and architectural components, including form-lined MSE panels. The mock-ups helped the contractor identify fit-up and alignment issues and find ways to adjust construction techniques to improve quality while expediting construction. Final production work was not permitted until the mock-up panels were approved. After approval, the mock-ups served as a performance standard for all production work. (see Precast Solutions magazine, Fall 2011, for more details).

A level playing field: comparing steel and precast solutions
The total cost of the George Street Bridge was $11.6 million and includes $9.6 million to construct the 36,000 sq ft of precast concrete arch structure over the waterfront park; $2 million was spent to construct the 7,860 sq ft of steel girder/concrete deck structure over Route 18. This equates to a unit price of $266 per sq ft for the precast arch bridge and $261 per sq ft for the steel span.

This finding is particularly significant, as both the steel and the concrete portions of the bridge were built at the same time, by the same contractor and on the same site, and utilized the same architectural surface treatments. These similarities provided a unique opportunity to evaluate the cost of providing a “non-conventional” structure type to that of a more traditional bridge design.

On a square foot basis, the precast concrete arch portion of the bridge was just under 2% more expensive to construct than the steel portion of the structure. However, without requiring a paint system, bearings or joints to maintain, the life cycle cost of the precast concrete arch bridge is substantially less than a steel bridge alternative. The durability of the precast solution and its substantially lower life-cycle costs made precast a very attractive solution for a very modest increase in initial cost.

A unique application, the use of long-span precast concrete arches with a lightweight cellular concrete overfill represents an engineering innovation that proved economical and exceeded the expectations of the client and the community.

Thomas G. Zink, P.E., is vice president of Gannett Fleming Inc.

By Sue McCraven

On a muggy June morning in 1907, an inspection engineer noticed the steel girders on a Quebec bridge under construction – the biggest cantilever bridge in the world – were out of alignment by ¼ in. “Not serious,” was the verdict of the famous New York bridge designer, Theodore Cooper, who knew the design load for the 1,800-ft single span had been underestimated by 4,000 tons. Bridge work continued.

In late August, an inspection engineer reported that the girders had shifted further and were now noticeably bent. Pressure to complete the bridge on time for its scheduled opening ceremony with King George V overrode caution. Ironworkers continued riveting 150 ft over the St. Lawrence River. Two days later, the horrific screeching of twisting steel was heard more than six miles away in Quebec City, and was the last sound heard by the 75 workers who fell to their deaths.

Disaster and loss of human life led to the demand for a Canadian railway bridge standard and, subsequently,

the Canadian Standards Association (CSA) developed its first standard. CSA (www.csa.ca) has since grown and currently has more than 2,600 standards in 56 broad subject areas. In this article, Michael Mortimer, program manager for Built Environment Standards, and Muktha Tumkur, project manager for Concrete Standards, both of CSA, were asked to explain the main differences between CSA and U.S. standards like ANSI, PCI and ACI,¹ and to define what really drives the birth of a standard.

We know that the Canadian Standards Association is an independent, member-based, not-for-profit organization in Canada. How do CSA standards for cast-in-place and precast concrete differ from U.S. standards, like ACI and PCI?

Mortimer: In the States, you have hundreds of ANSI-accredited standards-writing organizations, like ASTM and ACI. In Canada, we have four standards-development organizations (accredited by the Standards Council of Canada, Canada’s equivalent to ANSI) and there is a good reason for this. America has 10 times the population of Canada, and U.S. standards are more specialized and in-depth. CSA, on the other hand, has adopted existing standards and is broader in its approach and scope.

CSA’s role is to ensure that technology and methods are locally relevant to Canada, taking into consideration local differences in geography, geology, as well as seismic and climatic conditions. CSA is a ‘standards-maker’ in technology areas where Canada is a world-class leader (examples are cold-weather engineering and alkali-aggregate reactivity). We are a ‘standards-taker’ where a world-class technology already exists. We do this via a combination of copyright agreements and/or references to other standards such as ASTM and ACI.

Specifically with regard to precast concrete standards, what U.S. standards would be the most similar to CSA and how are they different?

Tumkur: The closest American equivalents to CSA A23.4 are PCI standards MNL 116, 117, 122 and 135. ACI also has precast standards, but they are significantly different in scope to CSA A23.4, “Precast Concrete – Materials and Construction.” As a specific example, ACI has a precast design standard for structures in seismic zones. In Canada, CSA A23.3, “Design of Concrete Structures,” covers all Canadian structural design requirements for all concrete elements – both cast-in-place as well as precast.

What are the hot topics currently being considered by CSA Committee 23.4?

Tumkur: I would consider the harmonization of standards across North America a key issue, as is a trend to more performance-based as opposed to prescriptive requirements within standards. Performance-based specifications facilitate innovation without compromising safety. This is not just a hot topic in the precast area, but is a general trend in CSA construction standards. Permitting maximum freedom for technical development is CSA’s policy.

How does CSA measure precast concrete performance in a standard?

Tumkur: ‘Performance’ relates more to concrete as a material, which is covered in the CSA A23.1/.2 Standards. The CSA A23.4 precast standard deals with the precast concrete plant and processes. CSA’s A23.1 concrete standard includes a combination of prescriptive as well as performance-based requirements. The performance specifications also have test methods to verify that the performance has been met. Where reliable, proven performance tests do not yet exist, prescriptive specifications have been retained.

How many CSA technical committees are specific to the precast concrete industry?

Tumkur: There are five concrete design standard committees and four concrete material and construction committees (see the sidebar “CSA Standards”). CSA Standard 23.4, “Precast Concrete – Materials and Construction,” was first issued in 1978; it is updated about every five years, and the most recent edition was issued in 2009. Like ACI, CSA’s technical committees are a balanced representation of interest groups and comprised of volunteers who are experts in their field.

What happens when U.S. and Canadian standards for precast concrete differ? Can a contractor build a precast structure in Canada to American standards?

Mortimer: No. Any contractor building in Canada must be in compliance with the applicable Provincial or Territorial building code. The CSA A23.4 is indirectly referenced in Canadian building codes through other standards such as CSA A23.3, “Design of Concrete Structures.” Canada covers a broad expanse of geography, seismic zones and climates. The local building codes specify the local load factor requirements that vary significantly from region to region.

The collapse of the Quebec Bridge in 1907 obviously led to the demand for Canadian railway bridge standards and the beginning of CSA. But what drives the development of CSA standards today?

Mortimer: It’s true that concern for public safety was the “ticket of admission” for the development of most standards at the turn of the 20th century. But the need for safety is no longer the only driver of standards. In the ’40s and ’50s, “fitness for use” and “quality and performance” also started to drive standards development. When we had the oil shock in the ’70s, we saw energy efficiency standards development emerge. Today, in the 21st century, standards must be responsive to a number of drivers: safety, durability, quality, as well as sustainability issues – a combination of environmental stewardship, and socially responsible economic development. In the final analysis, for standards to remain relevant, they must constantly evolve in response to societal needs.

Does CSA perform precast plant certification inspections?

Mortimer: Yes. Both CPCI, the Canadian Precast/Prestressed Concrete Institute, and CSA have precast plant certification programs. CSA-certified plants utilize professional engineers that are part of a manufacturing plant with a qualified quality system. Personnel are tied directly to the manufacturing site and the supervising engineer is accountable for the production and quality of the product. CSA’s precast plant certification program is accredited nationally by the Standards Council of Canada.

What is the difference between CSA International and CSA Standards?

Tumkur: CSA International conducts product testing and certification. CSA is the standards-development organization.

CSA Standards

CSA Concrete Design Standards
(visit www.csa.ca for more information)

• CSA A23.3 – Design of concrete structures

• CSA S413 – Design of parking structures

• CSA S6 – Canadian highway bridge design code

• CSA S806 – Design and Construction of Building Components with Fibre-Reinforced Polymers

• CSA S16 – Limit states design of steel structures (precast connections)

CSA Concrete Material and Construction Standards

• CSA 23.4 – Precast concrete – Materials and construction

• CSA A23.1 – Concrete Materials and methods of concrete construction

• CSA A23.2 – Methods of test and standard practices for concrete

• CSA A3000-Series – Cementitious materials compendium

¹ANSI is the American National Standards Institute; PCI is the Precast/Prestressed Concrete Institute; and ACI stands for the American Concrete Institute (see “ACI – Strength through Consensus,” May-June 2011 Precast Inc.).

Sue McCraven, NPCA technical consultant and Precast Solutions magazine editor, is a civil and environmental engineer.

Don’t forget to check out all of our Meet a Precaster blog posts and if you’re an NPCA producer member and would like to be featured in a future Meet a Precaster post, please send an email to NPCA’s director of communication, Kirk Stelsel.

Q: Where are you located?
A: Hudson, N.H. and Londonberry, N.H.

Q: How long have you been in business?
A: CSI has been in business since 1972.

Q: How long have you been a member of NPCA?
A: Since 1974.

Q: What are the best benefits of NPCA membership?
A: To establish and strengthen the relationships with our associate members who are so very important to our day-to-day operations and to to keep abreast of the latest developments, opportunities, and challenges within the precast concrete products industry. NPCA also allows us to have face-to-face exchanges with other precast producers regarding these issues, and sharing ideas is commonplace and beneficial to all of our efforts. It boils down to having a shared commitment to a common goal.

Q: What products do you produce?
A: Manholes and catch basins; Uwall, T-Wall, and L-wall retaining wall systems; box culverts; rigid frame bridge systems; CON/SPAN and BEBO bridge systems; box structures; commercial septic tanks; stormwater retention systems; median barrier; sound walls/noise barriers; bridge decks/slabs /abutments/wingwalls; headwalls; fire cisterns; grease traps; tunnels; electrical vaults; rail platforms/stations; custom structures.

Q: Have you been introduced to any new products lately?
A: Yes, we have introduced a new retaining wall system which we are quite excited about – “Uwall” – short for Universal Wall System. We feel it is a very uniquely engineered wall system which offers many competitive advantages, and features large standard precast modular block sections measuring 4 ft x 8 ft; and a smaller 2 ft x 8 ft standard section. We can also add up to three additional feet monolithically to our standard 4 ft x 8 ft sections for single course wall applications – or for any top course section. Setting 4 ft x 8 ft sections up to 7 ft x 8 ft sections allows the contractor to install the system very rapidly. We can also supply sloped top course sections to follow whatever grading may be required on site, instead of stepping the wall. This provides the owner with a nice clean angle and better aesthetics. We are in the process of licensing the Uwall System throughout North America.

Q: What are the top attributes of precast concrete?
A: Its inherent durability characteristics and speed of installation.

Q: What has your company done to fight off the recession?
A: Leadership and lean training for all managers and supervisors. We have worked very hard to find the right number of (best) employees and place them in the correct position to work as efficiently and effectively as possible. To borrow a phrase – we have done our best to keep no stone left unturned.

Q: What have you see in your area as far as recovery?
A: Not a whole lot yet. Some home building is starting again which is good to see, but we are fortunate to at least have some interstate highway work progressing nearby.

Q: What are your plans for the future?
A: We feel we have right-sized our companies and are in a very good position to grow the CSI Group of Companies. We are going to concentrate on finding some progressive companies who are leaders within their marketplace to partner with us and introduce the Universal Wall System while continuing to seek more DOT approvals. We are also going to roll out two or three more new products in 2013 which have licensing opportunities. However, our number one focus will always be: Keeping the main thing, the main thing.

The opinions expressed in this blog post are solely those of the member, and not of NPCA or any of its employees.

Don’t forget to check out all of our Meet a Precaster blog posts and if you’re an NPCA producer member and would like to be featured in a future Meet a Precaster post, please send an email to NPCA’s assistant director of communication, Kirk Stelsel.

Q: Where are you located?
A: 8261 McCutchen Road, Bakersfield, California, 93311.  We are two hours north of Los Angeles in the beautiful Central Valley of California.

Q: How long have you been in business?
A: We have been StructureCast since January 1997. Prior to that time, we were Bakersfield Precast, founded in 1970.

Q: How long have you been a member of NPCA?
A: We have been a member of NPCA since 1990.

Q: Why did you join NPCA and what are the best benefits?
A: We joined NPCA to meet other precasters; share best practices, common experiences and goals; and expand our industry knowledge. In addition to the networking opportunities, other benefits are the educational programs (both online and at the Precast Show), the technical support, access to the resources on the NPCA website, and the certification program.  The high standards of NPCA membership and certification have helped us focus on quality control and efficiencies in production, which in turn have helped us to continue to improve and provide our customers with better precast products.

Q: What products do you produce?
A: Custom design-build products, architectural wall panels, Easi-Set & Easi-Span pre-engineered buildings, StoneTree fence systems, structural wall panels, retaining wall structures, sound walls, pre-stressed and post tensioned products, bridge girders, double tees, columns, box culverts, headwalls, vaults, stormwater structures, and drainage inlets. We consider ourselves a custom precaster and a strong value added team member for owners, architects, engineers and contractors in the design-build process.

Q: Have you introduced any new products lately?
A: Our newest product line is the Easi-Set/Easi-Span pre-engineered buildings and the Stonetree fence panel system. The Easi-Set/Easi-Span buildings offer fast installation and a maintenance free, cost effective and secure alternative to traditional masonry building. The Stonetree fence system, with its appearance of natural stone combined with the strength and durability of reinforced precast concrete, provides a decorative, secure fence product. In addition, the system allows for rapid placement of more than 1,000 linear feet per day, which dramatically cuts down time and cost on the jobsite for the contractor.

Q: What are the top attributes of precast concrete?
A: Production efficiency, durability, consistent quality, sustainability, custom applications, versatility and speed of installation, which is a cost savings for our customers.

Q: What has your company done to fight off the recession?
A: We have diversified by broadening our product line in an effort to expand our market base.  One of our strengths as a custom precaster is our willingness to take a look at any project – whether or not it’s designed as precast – and offer a precast solution for our customers and the market. We have streamlined all of our processes – sales, estimating, production, quality control and project management. We are also more carefully reviewing our budgets and costing systems so we can more accurately and effectively control our costs and increase our margins and overall profitability.

Q: What have you see in your area as far as recovery?
A: We are seeing a glimmer of a recovery here in California. However, California is a very large and a very competitive market and we cover all of it – with both architectural and structural precast. The volume and quality of our bidding opportunities is improving, but the contract awards and the money is still very tight out there. The owners and general contractors are trying to squeeze every last cent out of every contract.

Q: What are your plans for the future?
A: We want to continue to be out front as a precast producer and a leader in bringing precast concrete products to a larger market. We plan to aggressively market precast concrete solutions to architects and engineers for the design on their projects. We want to increase our partnerships with more design-build teams to develop more innovative opportunities for precast projects.  Most importantly, we are committed to producing the highest quality precast products, providing superior customer service, and unsurpassed on-time delivery. In short, we want to put precast concrete and StructureCast on the map!

The opinions expressed in this blog post are solely those of the member, and not of NPCA or any of its employees.

Precast Concrete Covered Bridge

Precast concrete has long been a staple of our nation’s infrastructure. Thanks to its durability, dependability, quality and ease of installation, DOTs have used it for a wide range of applications, including walls, bridges, barriers and more.

While some precast elements dutifully do their job but go largely unnoticed as they blend into roadway landscapes, others stand out thanks to integral colors, unique shapes, insets and finishes that give them a dual purpose.

These components are much more than just dependable infrastructure. In Florida, for example, highway sound walls now come to life with inset regional wildlife such as manatees, alligators, fish and flamingos. Other states have chosen designs that reflect the surrounding aesthetics such as natural stone, wood texture or brick.

With precast concrete, you get the desired look paired with a long service life and fast installation. And many times precast concrete can be put into place in a fraction of the time of competing materials. One example is a soundwall system released recently by an NPCA member with an integrated column that serves as the foundation for the wall as well as the panel joint. Many variations of form-finished MSE and retaining walls are also available from precast manufactures across the country.

Precast Concrete Architectural Bridge

When it comes to bridges, precast concrete can convey a community’s architectural style, protect the environment, and span everything from gullies to gorges. Whether the product you need is a short-span bridge or a comprehensive solution that can traverse a major river, precast can provide the attractive, long-lasting design you need. A story in our Fall 2011 issue of Precast Solutions highlighted one such bridge in NJ.

Across the map, State DOTs and road agencies are gaining public approval and strong support for custom precast infrastructure. See more of what precast concrete can do for you.

Precast Concrete Soundwall With Integrated Column

It boasts a prestige than many schools strive for but few have; however, like any school located in a major metropolitan area, the day-to-day safety of its students is a challenge not always easily achieved. Three seniors from its Department of Civil Engineering took note of one particular safety concern for a class project – the prevalence high traffic areas where students often need to cross roads or ride their bikes.

The three developed a proposal for a pedestrian bridge to help students navigate Charles Street, a busy thoroughfare that cuts across the east side of campus. Due to a burgeoning population, many students now reside on the east side of Charles Street in university-built housing, but are forced to cross it in order to get to the academic buildings and on the west side of the street. An article in The Baltimore Sun highlighted the students’ efforts, including team member Erin Kelly, whose sorority “big sister,” Miriam Frankl, was killed in a hit-and-run crash involving a chronic drunk driver.

In preparation for the pedestrian bridge design, the students precisely calculated weights, loads and horizontal wind forces and surveyed fellow students. They found that 84 percent feel unsafe crossing the road and cross it an average of eight times daily. They also accounted for disability access by connecting the bridge with an elevator-equipped dorm and consulted with a local engineering firm and construction company.

Their design is a 150 ft precast concrete bridge that spans Charles Street. In the proposal, the students note that the use of precast concrete offers high quality products with uniformity thanks to the controlled environment and tight quality control standards of plant-produced precast products. The proposal also cites the ease of transportation and construction of precast products that would allow for a quicker construction timeline and minimize the impact on vehicular traffic on Charles Street. In addition, a precaster could include inset features such as masonry elements or the school’s insignia and provide an architectural finish through the use of form liners, coloring or other methods to match the campus’s existing aesthetics.

To learn more about a wide variety of precast concrete products that can provide your next project with durable, quality products that install quickly and are delivered to your site in an “as needed” fashion, visit our precast products page.