Center for Extreme Load Effects on Structures

At Risk: Existing Structures

A growing risk

Existing structures are the biggest single factor that turns events like earthquakes and hurricanes into disasters.

The risk is increasing worldwide:

  • More people live and work in areas at risk for earthquakes, hurricanes, tornados, and floods.
  • The built environment is growing denser, so any event will have greater impact.

Building codes are not enough

For decades, engineers have developed new technology and practices to make structures more resistant to earthquakes, floods, hurricanes, and fire. Communities in areas of frequent hazards often use building codes to enforce minimum standards of protection.

  • Codes apply to new construction, so it can take 50 years or more before most of a community's buildings meet requirements.
  • Codes are minimum standards that prevent structural collapse and loss of life. They do not prevent building damage and economic loss.
  • Codes are only as good as their enforcement.

See also:
CELES facilities

Related Links:

HAZUS - loss estimation tool

Areas at great risk from existing structures

1. Structures in the central and eastern part of the country have no earthquake protection and little protection from flood and wind. Although earthquakes are less common, the stock of vulnerable structures, plus the dense population and character of the bedrock creates equal risk to communities in California

2. In the U.S. West, structures built before 1975, including most bridges and water lines (American Lifelines Alliance 2003).

Issues with protecting existing structures

Implementation - In most cases, the technology exists.

Cost - It is more expensive to protect an existing structure than to build in protection during construction. Who will pay? Is it worth it to retrofit a low-value building?

Size of problem - With most structures at risk in many regions, and the cost the cost of protection, communities are forced to set priorities.

Priorities - Residents of many regions at risk have no experience of earthquake, hurricane, and flood risk and do not understand the extent of damage that can happen.

What can communities do?

  1. Develop microzoning to understand the risk faced by each parcel of land.
  2. Adopt a sustainability perspective to drive land use, priorities, and prevention.
  3. Identify critical structures and lifelines that must be protected for community survival and prosperity.
  4. Establish policies to encourage owners to protect their structures.
  5. Use tax relief and economic incentives to discourage abandonment in low-income areas.

How can CELES help?

  • Provide information and mapping to understand the interactions of topography, soil, and surrounding structures with the hazards from earthquake, wind, flood, and fire.
  • Visualization and mapping for decision making.
  • Education and training