Structural Engineering Issues for a

Large Cascadia Event

Overview

•Need a Framework and Methods for Structural Hazard

Assessment Under Long-Duration Motions

•Many Knowledge Gaps and Data Needs

•Two Zones• Coastal (intensity and tsunami

post-earthquake)

• Valley (attenuated motions and site specific responses)

Swiss Agency for Development and Cooperation

Seismic Hazard Analysis for Long-Duration Motions

• Event scenarios (fault rupture, magnitude)

• Attenuation (changes over distance)

• Site specific responses (local shaking, soil behavior)

• Structural fragility (how building responds to shaking)

• Performance (damage/collapse)

•FireRahman and Mashfiq, ADPC

Build Case for Investment

Predicts:

•Physical damage to residential and commercial buildings, schools, critical facilities, and infrastructure;

•Economic loss, including lost jobs, business interruptions, repair and reconstruction costs; and

•Social impacts, including estimates of shelter requirements, displaced households, and population exposed to scenario floods, earthquakes, and hurricanes.

HAZUS-MH

Building Inventory•Oregon • Growth prior to hazard

recognition (and after!)• Unengineered buildings• Foundations• Reinforced concrete and

masonry• UR masonry • Discontinuities• Large Openings• Soft stories• Short columns• Torsional eccentricities• Elevation and plan stiffness

changes• Parapet walls• Pounding

Fragility Curves for Building Inventory•Describes Damage to Building as Function of Input (PGA)• Slight damage to

collapse• Statistical Functions• Unengineered

buildings • Foundations?• New ones needed• PGA adequate

parameter? •Optimistic?

Key Issues

• Building stock• No shake out

• Fragility Curves for PBE

• Need input motions • Real and

synthetic

• Current Codes Adequate for New Design?

• Retrofit Methods for Existing Stocks

• High performance materials ($)

• Hybridized designs

• Tsunami • Tsunami after

Seismic