Review of NBCC earthquake-resistant design requirements for cladding connectors

Abstract

As a consequence of recent increases in the severity of seismic design force requirements in Canada, practicing engineers who design cladding connectors should be concerned with their seismic resistance. The current design requirements of the 1990 edition of the National Building Code of Canada for nonstructural components call for unduly high prescribed design forces for the cladding connectors without providing justification, commentary, or substantiation for this constraint, nor guidance on how this is to be achieved. This paper offers some rationalization of these stringent design requirements based on a review of their evolution, outlines some of the shortcomings of the current design approach, recommends possible abatements of the requirements in special cases, and points toward future directions and alternate philosophies for the design of cladding connectors. In particular, the following are recommended: (i) the scope of Part 4 of the National Building Code of Canada should be modified to specifically indicate that cladding connectors are to be designed by a professional engineer, (ii) the latest cladding-connector seismic-resistant design philosophy of the Structural Engineers Association of California should be incorporated into the National Building Code of Canada; (iii) a distinction should be made between out-of-plane and in-plane cladding-connector seismic-resistant design requirements; (iv) a commentary should be written on cladding-related seismic-resistant design issues to clearly state current philosophy, uncertainties, and limits of knowledge be included in the building code, and (v) standardized seismic-resistant cladding connectors be developed with capacities to meet prescribed levels of ductile behavior and interstory drifts and widely distributed to the profession. Key words: cladding, connectors, earthquake, design, code, seismic.