Establishing Accurate Benchmark Data to Effect Cost Savings

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The client:

The CANDU Owners Group (COG)

The problem:

Elevated temperatures can significantly influence the performance and behaviour of reinforced concrete. Typically, these effects result in reduced material and physical properties of the concrete and reinforcing steel, depending on the actual temperature and duration of exposure. This consideration is of particular concern for reinforced concrete containment structures at CANDU nuclear generating stations.

Project objectives:

This project was undertaken to develop an analytical method to model and predict the performance and behaviour of reinforced concrete structures subjected to elevated temperatures. The principal objective of the project was to use data and test results from previous laboratory testing at Kinectrics to analyze and/or predict the performance of full-size concrete structures under the influence of elevated temperatures.

With better predictions and enhanced understanding of the performance of reinforced structures subjected to elevated temperatures, revisions to the current operating guidelines and limits for containment concrete at CANDU stations might be facilitated.

Scope of work:

Conceptually, the approach involved modifying a candidate non-linear finite element analysis program for reinforced concrete. Appropriate temperature-dependent mathematical models were employed to account for changing material properties through a structure’s cross-section due to exposure to elevated temperatures. The modified program was then used to analyze the response and load-carrying capacity of a number of generic concrete members, typical of the size and scale of such members at a nuclear generating plant. Potential reductions in their load-carrying capacities were determined when exposed to various elevated temperatures and durations.

Results:

The analyses resulted in the identification of load-capacity reductions for structures subjected to elevated temperatures, as a function of:

• Structure type: girder, wall, slab
• Elevated temperature: 65° C, 95° C, 175° C, 250° C
• Duration: 0.1 day, 0.5 day, 1 day, 3 days, 7 days

Client Benefits:

• With comprehensive detailed data, the client gained a credible opportunity to revise current plant operating guidelines and temperature limits.
• Safety margins for the client’s current plant operations were validated.

For more information, contact;

Ron Cullen, 416.207.6000 x5543, ron.cullen@kinectrics.com