Disaster led to the birth of CSA’s first standard.
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 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.