Regulatory Perspective for the Definition of Probabilistic Acceptance Criteria for CANDU Pressure Tubes

For the assurance of fitness-for-service of CANDU Pressure Tubes (PTs), guidelines and acceptance criteria are provided in Canadian Standard Association (CSA) N285.8-15, Technical requirements for in-service evaluation of zirconium alloy pressure Tubes in CANDU reactors. With respect to the assessment of risk of operation associated with degradation mechanisms and aging of the PTs in the entire core of a given reactor Unit, Clause 7 of CSA N285.8 allows Licensee’s to use either a deterministic or probabilistic method to assess the likelihood of PT failures. When a probabilistic method is used, the Licensee is obligated to demonstrate that the combined frequency of PT failure(s) over the evaluation period, due to the various potential degradation mechanisms, is less than the maximum acceptable frequency provided in Table C.1 of CSA N285.8-15. The maximum acceptable frequency provided in Table C.1 of CSA N285.8-15 was developed in the early-1990’s based on reactor operating experience and knowledge at that time, Station Siting Guides and Consultative Regulatory Guide C-006 (Revision 1). A task group was established by the CSA N285.8 Technical Steering Committee to re-evaluate the allowable failure frequencies to confirm that they remain relevant given the current state of knowledge and the additional evaluation tools available. This paper provides Canadian Nuclear Safety Commission staff views regarding the technical basis for revisions to the allowable frequencies based upon current industry practices in conducting probabilistic core assessments.

Development of soy-based adhesives for the manufacture of wood composite products

Soy-based resins have recently attracted great attention as adhesives in the wood composite industry. This article is focusing on hydrolysis and modification of soy protein concentrates to formulate soy-based resins for wood composites. The soy-based resins have been evaluated in terms of bondability on wood substrates and bonding performance in plywood products. The performance of plywood was found to meet the relevant CSA standard (Canadian Standard Association) requirements under both of dry and wet conditions, if the soy-based resins were obtained from low hydrolyzed soy flour. Hydrolysis is an effective and efficient tool for reducing the viscosity of soy resins. However, hydrolysis also reduces the bond strength of soy-based resins as hydrolysis cleaves the macromolecules of soy proteins into smaller molecules. Modified soy-based resins have a certain potential for production of interior- and exterior-used plywood.

Safety of gravity-load columns in shear wall buildings designed to Canadian standard CSA A23.3

It has been a Canadian code requirement for 25 years to check whether concrete gravity-load columns can tolerate the building deformations due to the design earthquake; but the way this has typically been done using linear analysis significantly underestimates the seismic demands on gravity-load columns. Concern about the safety of gravity-load columns over the plastic hinge height of concrete shear walls, particularly elongated wall-like gravity-load columns, has resulted in new design requirements in Update No. 3 of Canadian Standard Association (CSA) A23.3–04 issued in August 2009. The current paper provides the background to these new requirements. If nonlinear analysis is not done, closely spaced seismic hoops shall be provided in all columns and walls that support gravity loads, and these members shall meet the same limit on maximum compression strain depth as concrete shear walls. The results of nonlinear analyses were used to validate this simple design rule, and to investigate factors that increase seismic demands on gravity-load columns such as diagonal cracking of concrete shear walls, localized damage of columns from cover spalling and bar buckling, and larger first storey heights. Nonlinear analysis has shown that 2.4 m (8 ft) long columns can lose over 50% of their axial load carrying capacity at an inelastic drift ratio of only 1%.

Reliability-Based Design and Assessment Standards for Onshore Natural Gas Transmission Pipelines

Onshore pipelines have traditionally been designed with a deterministic stress-based methodology. The changing operating environment has, however, imposed many challenges to the pipeline industry, including heightened public awareness of risk, more challenging natural hazards, and increased economic competitiveness. To meet the societal expectation of pipeline safety and enhance the competitiveness of the pipeline industry, significant efforts have been spent for the development of reliability-based design and assessment (RBDA) methodology. This paper will briefly review the technology development in the RBDA area and the focus will be on the progresses in the past years in standard development within the American Society of Mechanical Engineers (ASME) and the Canadian Standard Association (CSA) organizations.

Development of Reliability-Based Design and Assessment Standards for Onshore Natural Gas Transmission Pipelines

Onshore pipelines have traditionally been designed with a deterministic stress based methodology. The changing operating environment has however imposed many challenges to the pipeline industry, including heightened public awareness of risk, more challenging natural hazards and increased economic competitiveness. To meet the societal expectation of pipeline safety and enhance the competitiveness of the pipeline industry, significant efforts have been spent for the development of reliability-based design and assessment (RBDA) methodology. This paper will briefly review the technology development in the RBDA area and the focus will be on the progresses in the past years in standard development within the American Society of Mechanical Engineers (ASME) and the Canadian Standard Association (CSA) organizations.

Beam-to-column connections in steel frames

The importance of beam-to-column connections in determining the load–deformation behaviour of steel building frames has been recognized for more than 70 years. Yet steel design specifications, including Canadian Standard Association standard CAN3-S16.1-M84, still mandate that connections be treated as either "pinned" or "rigid," and prescribe approximate design assumptions accordingly. Structural analysis procedures and tools exist that can account adequately for connection behaviour. What is not complete is the knowledge of the force–deformation behaviour of the various connection types.In this paper, what is known of the force–deformation behaviour of the commonly used connection types is described. The factors influencing that behaviour are outlined. Procedures for modelling connection behaviour and for incorporating it into structural analysis computer programs are described. The effects of connections on the behaviour of the overall structure are described and illustrated with examples. Finally, the areas where additional research is needed are discussed. Key words: connections, steel, structural analysis, columns, semirigid design.