Subject and Keywords:
Soil-steel structures have been part of Canadian design codes since the 1970s. The inclusion in the Ontario design codes was necessary due to a growing use of flexible buried structures in practice. Since those early developments, the subsequent code committees have always strived to find the appropriate balance between the primary objective of providing design criteria that reflect the safety and serviceability requirements of the code and incorporating the significant practical experience of owners, engineers and industry. Each decade has seen innovations in products and applications as well as advances in research and numerical modelling. Editions of the code have acknowledged these changes, often in the non-mandatory sections, but have sometimes struggled to provide specific criteria. Instead it has provided general guidance or framework for design. Currently, many of the existing design clauses do not directly cover the applications of both flexible and rigid buried structures in regular use today. This paper describes the key updates being proposed for the Buried Structures section of the Canadian Highway Bridge Design Code. These changes are based on input from owners, engineers and industry describing the needs for current design and practice as well as a modem framework for permitting innovation. The major changes include areas such of finite element analysis, foundation design, conduit wall buckling and the use of flexible structures in cold regions susceptible to permafrost. These major changes will be discussed conceptually as final approval is still pending before inclusion in the 2019 version. The paper will describe some of the background and rationale for the proposals. Finally, the paper will discuss the challenges faced by the sub-committee in determining what should be included in the mandatory sections of the code or in commentary.