Abstract Outline for Increasing Seismic Integrity of Wood Framed Structures

This research project is to determine economically feasible methods of improving the seismic integrity of wood frame structures in British Columbia. These methods will be applied to new as well as existing construction. Over the years, our understanding of earthquakes and methods of surviving them have drastically improved. However due to increased populations and ever increasing urban densities, it is a struggle to keep the risk factor to a minimum. Earthquakes are sudden tectonic shift in the earth geological plates. These Tectonic shifts release massive amounts of energy with cause the surface above to shake violently. These forces depending on the location and severity of the release can and have caused numerous structural failures of buildings big and small. Because earthquakes shake vertically and laterally, it is a challenge to ensure every building will properly resist them especially when every structure is unique.

Initial research has been done into various civil engineering websites as well as documents regarding increasing the strength of critical areas and connections using different methods such as, light gauge metal reinforcing of wood joints, and increasing lateral strength of bearing wall panels by doubling up the required sheeting. Also increasing the number of anchor bolts or adding steel strapping to tie the structure above to the foundation wall. More blocking may be added above the foundation sill plate to increase shear resistance. For large openings in critical walls, reinforcing the corners with steel plates may be an option. For existing buildings, masonry chimneys are a major issue. Their weight causes an extreme hazard during earthquakes. There are a number of methods to reduce this risk such as, replacing the brick chimney above the roof line with a metal flue, or adding metal bracing from the chimney to the structure. Additional plywood sheathing could be added to prevent portions of the chimney from falling through as well. Research is ongoing and additional ideas will be explored.

The upgrades researched to date would be relatively inexpensive to add to a new building. However upgrading an existing structure with these items would be somewhat more expensive but well worth the added safety especially in seismically active zones. Currently many jurisdictions are trying to implement new code items to cover these and other issues. The current BCBC (British Columbia Building Code) should be updated to increase the level of seismic protection especially considering the proposed increase to six story wood framed structures.

Academic References:

-Canada Mortgage and Housing Corporation, CMHC, Residential Guide to Earthquake Resistance, Canada Mortgage and Housing Corporation, 1998.

-J. Hans Rainer, Erol Karacabeyli, Performance of Wood-frame Building Construction in Earthquakes, Forintek Canada Corp., 1999.

-André Filiatrault, Elements of earthquake engineering and structural dynamics, Presses intl Polytechnique, 2002.

-Taranath Bungale S, Wind and earthquake resistant buildings : structural analysis and design,
New York : Marcel Dekker, c2005.

-Canada Mortgage and Housing Corporation, 1990. Earthquake damage in the San Fransisco Area and Projection to Greater Vancouver.

-Hans Rainer, Database For seismic design of Part 9 structures, Forinteck Canada Coorperation, Canadian Wood Council, 2002.

-Engineering Design In Wood, Canadian Standards Association, 2001.

-Allen, D.E, Seismic Evaluation and Upgrading of Buildings, National Research Council of Canada, 1999.

-Rainer, J.H. and Karacabeyli, E, Performance of wood-frame construction in past earthquakes. Proceedings, 12th world conference of earthquake engineering, Auckland, 2000.

-CMHC-SCHL, Canadian wood-frame house construction. Canada Mortgage and Housing Corporation, Ottawa, 2006.