How has engineering for small buildings changed under the 2012 Building Code?

In the 2012 Building Code, the requirement for seismic resistance is, for the first time, included in Part 9. This means that single family residences must be constructed to withstand earthquakes.

As far as structural engineering goes, however, little will change.

Structural engineers have been required to consider earthquake loads since June 2008 when the Council of the Association of Professional Engineers and Geoscientists of British Columbia (APEGBC) adopted a new guideline for the provision of structural engineering services for residences and other small buildings. This Guideline provided a practice standard for structural design of housing and small buildings that come under Part 9 of the British Columbia Building Code(BCBC). One reason for adopting the new guideline is to improve public safety by ensuring that small buildings provide adequate resistance to earthquake forces. There were concerns that new homes are being built with nontraditional open concept floor plans, incorporating more and larger windows and door openings, longer spans, higher walls and that consequently, newer homes have less resistance to earthquakes than older homes.

After the adoption of the guidelines in 2008, APEGBC issued a statement that “failure to meet the intent of these Guidelines could be evidence of unprofessional misconduct and lead to disciplinary proceedings.”

The Building and Safety Policy Branch of British Columbia, then, added its voice to that of the Association of Professional Engineers when, in September 2008, they issued their “Information Bulletin” and “Revised Appendix Notes” to Section 9.4 of the 2006 British Columbia Building Code. This reads, in part, not all Part 9 buildings have configurations or details that will provide adequate resistance to lateral loads. For example, newer houses may have few interior partitions and very large openings in the exterior walls. Mercantile buildings might be long and narrow with almost entirely windowed walls on the ends and few structurally attached interior partitions. The Engineering Guide for Wood Frame Construction (the CWC Guide) published by the Canadian Wood Council also identifies situations where the Part 9 prescriptive requirements are considered to be inadequate for resisting lateral loads. The CWC Guide may be used to provide acceptable engineering solutions that are alternative to Part 4.

Section 9.4 of the brand new 2012 Code reads in part,

9.4.1.1. General  (See Appendix A.)

1) Subject to the application limitations defined elsewhere in this Part, structural members and their connections shall

a) conform to requirements provided elsewhere in this Part,

b) be designed according to good engineering practice such as that provided in CWC 2009, Engineering Guide for Wood Frame Construction or

c) be designed according to Part 4 using the loads and deflection and vibration limits specified in

i) Part 9, or

ii) Part 4.

This portion of the 2012 Code is almost identical to the same section in the 2006 Building Code. Prior to the new code, most structural engineers designed according to clauses b) and c) since no engineering is required for building components falling under clause a). This is also the case under the new code.

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