The reason for this research work arose as a result of interviews and surveys of the professionals associated with steel industry which suggested that there is a concern that the main difficulty when reusing steel is the problem of identification of steel and its structural properties. Another issue which was brought up was related to the approval by building officials. It was decided that the investigation will be done to look into the national codes and steel standards to trace the evolution and identify potential problems, and ways to establish the characteristics of old steel.
General requirements
Although national standards and codes encourage new construction and use of new materials, the National Building Codes (NBC) definition of the scope includes “alteration, reconstruction, demolition, removal, relocation and occupancy of existing buildings”. Not only does the scope reiterate the application to old construction and new / different materials, but it has contained the following clause since 1985 - “Unless otherwise specified, used materials, appliances and equipment are permitted to be reused where they meet the requirements of this Code for new materials and are satisfactory for the intended use”. It should be noted that equivalence is defined for materials and components failing to comply with Part 4 and past performance, tests (for structure a full-scale test) or model analogue are accepted.
The third revision of the 1990 NBC included for the first time the relationship between NBC and other standards, testing and certification organizations, defining for designers authorities which can assist them to determine equivalencies. The 1995 Code was accompanied by the Structural Commentaries on the National Building Code of Canada 1995 which for the first time included a section entitled “Application of NBC Part 4 for the Structural evaluation and Upgrading of Existing Buildings”, assisting designers to deal with issues related to buildings designed to previous codes in the context of Part 4. This document is very important as it recognizes the shortcomings of Part 4 of the NBC with its focus on new construction (new or addition) and the lack of its application to existing buildings which may contain a structural system or materials no longer in use.
Used materials and systems are permitted if they comply with the NBC requirements for new construction. There is reasonable freedom given to designers to prove equivalency but the problem is that it is a departure from the prescriptive, requirement based process. The non-prescriptive approach challenges building department officials leading to inconsistent interpretation and varying attitudes and requirements. From the designer’s point of view it results in uncertainty about what may be required and acts as a deterrent to taking an alternative design approach.
The Ontario Building Code (OBC) 1997 has additional provisions which deal with existing buildings. Part 10 of the OBC deals with performance requirements related to change in use. Part 11 deals with Renovation. This part considers extensively the issue of fire safety resulting from change in use and increase in occupant load. It does not require a change in performance level in the case of alteration or repair which is consistent with the original design intention and use. However when the occupancy load is increased, this code requires remedial action to support the extra loads, although it accepts postings of restricted loading requirements for a portion of a floor.
The NBC 2005 has adopted a different, objective based approach. It specifies the objectives which the code aspires to achieve and in a separate division it describes how these can be met. There are no longer firm requirements which designers have to comply with. This approach will result in a significant change in the building approval process and the mind set of the building officials. There is no longer the norm and prescriptive solution but the designer has the freedom to address the objectives of the code and provide relevant documentation. This should make the approval process for innovative or non-standard construction far more readily achievable.