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Seismic Criteria for Marine and Coastal Structures in Vancouver, British Columbia

Updated: May 19, 2022

Marine Structures

Marine Structures and their components shall be designed to meet seismic requirements in

accordance with the Canadian Highway Bridge Design Code (CSA-S6, 2019) and its Commentary by implementing an importance category of "Other Bridges" and assuming equivalence to a "Regular Bridge".

There are two different design approaches are recognized for seismic events within CSA-S6, 2019:

  1. Performance-Based Design: this is a design philosophy, which is based on satisfying certain and structural, functional, and service performance criteria under a specified seismic hazard. There are Three (3) earthquake Return Periods are required to be investigated:



2475 year

Structures shall meet the minimum performance levels and criteria of Table 4.15 and Table 4.16 of CSA-S6, 2019, respectively. For implementing an importance category equivalent to "Other Bridges", the performance levels and general performance criteria to obtain the specified performance levels are summarized in Table 1 below.

Table 1 - Performance Levels and Criteria for Other Bridges (CSA-S6, 2019)

2. Force-Based Design: this is a design philosophy using a minimum lateral earthquake load based on the 2475-year Return Period seismic event. Force-Based Design is permitted only in certain cases, one of those being Regular Other Bridges. The performance of structures designed with this approach is expected to be consistent with Performance-Based Design at the 2475-year Return Period. The minimum lateral earthquake force for elastic analysis is to be calculated in accordance with Clause of CSA-S6, 2019.

Coastal Structures

Coastal Structures shall be designed in accordance with the Seismic Design Guidelines for

Dikes, developed by Golder Associates in 2014, which provide guidelines for seismic stability and integrity of High Consequence Dikes in Southwestern British Columbia and Vancouver Island.

Similarly to seismic design of highway bridges, seismic design of dikes has evolved in recent years to include Performance-Based Design criteria, which investigates the damage

associated to different earthquake levels. The Seismic Design Guidelines for Dikes defines three performance categories associated to three earthquake Return Periods: namely 100-year, 475-year and 2475-year. High Consequence Dikes are to meet the requirements shown in Table 2 of the Seismic Design Guidelines of Dike, which are summarized below in Table 2.

Table 2 - Performance Level and Criteria for Dikes

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