Innovative External Bracings

Project
Structural Seismic Upgrade of Office Building
Location
Vancouver, BC, Canada
Timeframe
2015 - 2017
Client
City of Vancouver
Industry Sector
Industrial
Service Area
Environment & Sustainability; Infrastructure; Project Delivery
Solutions
Construction Support Services; Geotechnical; Basic Engineering; Seismic Studies; Detailed Design

The City of Vancouver retained Ausenco as prime consultant to carry out the structural seismic analysis and seismic upgrade design of one of their buildings.

The 1975-vintage building is very unconventional: a two-directional four storey steel moment frame over two storeys of basement constructed primarily with precast concrete.

Performance based design using 3D non-linear analysis showed that by adding energy-dissipating devices with specific strength/stiffness in the first floor, premature failure of the structure can be eliminated, and flexural yielding can safely occur in existing steel members on all levels to further dissipate the seismic-input energy.

An innovative series of sloped buckling restrained bracings (BRBs) was used. Located only at ground level, this high energy dissipation system represents a first in Canada, for BRB use externally in a seismic upgrade.

This scheme, as well as close liaison with the Owner and Contractor regarding scheduling and sequencing of construction activities enabled all 400 staff and tenants to continue regular operations throughout construction (work only in basement and ground floor, no impact on upperthree floors).

Fibre Reinforced Polymer was used extensively in the basement parking garage to reinforce the main floor and basement precast plank floors and transfer load to new shear walls.

Ausenco’s design minimized the number of basement shear walls and enabled visitors to safely park and access the facility throughout the construction.

Ausenco coordinated the electrical, mechanical, and architectural services related to the seismic upgrade structural work.

This upgrade achieves life-safety performance for full NBCC 2015 code seismic requirements at a cost of only 1/3 of industry average.

  

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