Featured Research

from universities, journals, and other organizations

Double jeopardy: Building codes may underestimate risks due to multiple hazards

Date:
September 14, 2011
Source:
National Institute of Standards and Technology (NIST)
Summary:
As large parts of the United States recover from nature's one-two punch -- an earthquake followed by Hurricane Irene -- building researchers warn that a double whammy of seismic and wind hazards can increase the risk of structural damage to as much as twice the level implied in building codes.

Top: Wind zone map shows how the frequency and strength of extreme windstorms vary across the United States. Wind speeds in Zone IV (red), where the risk of extreme windstorms is greatest, can be as high as 250 miles per hour. Bottom: National seismic hazards maps display earthquake ground motions for various probability levels across the United States. These maps are the basis for seismic design provisions of building codes, insurance rate structures, and land-use planning.
Credit: Top -- Federal Emergency Management Agency / Bottom -- U.S. Geological Survey

As large parts of the United States recover from nature's one-two punch -- an earthquake followed by Hurricane Irene -- building researchers from the National Institute of Standards and Technology (NIST) warn that a double whammy of seismic and wind hazards can increase the risk of structural damage to as much as twice the level implied in building codes.

This is because current codes consider natural hazards individually, explains NIST's Dat Duthinh, a research structural engineer. So, if earthquakes rank as the top threat in a particular area, local codes require buildings to withstand a specified seismic load. In contrast, if hurricanes or tornadoes are the chief hazard, homes and buildings must be designed to resist loads up to an established maximum wind speed.

In a timely article published in the Journal of Structural Engineering, Duthinh, NIST Fellow Emil Simiu and Chiara Crosti (now at the University of Rome) challenge this compartmentalized approach. They show that in areas prone to both seismic and wind hazards, such as South Carolina, the risk that design limits will be exceeded can be as much as twice the risk in regions where only one hazard occurs, even accounting for the fact that these multiple hazards almost never occur simultaneously. As a consequence, buildings designed to meet code requirements in these double-jeopardy locations "do not necessarily achieve the level of safety implied," the researchers write.

Simiu explains by analogy: a motorcycle racer who takes on a second job as a high-wire performer. "By adding this new occupation, the racer increases his risk of injury, even though the timing and nature of the injuries sustained in a motorcycle accident or in a high-wire mishap may differ," he says. "Understandably, an insurer would raise the premium on a personal injury policy to account for the higher level of risk."

The researchers developed a method to assess risks due to wind and earthquakes using a common metric of structural resistance. With a consistent measure (the maximum lateral deflection), the combined risk of failure can be compared to the risk that design limits will be exceeded in regions vulnerable to only one of the hazards, the basis for safety requirements specified in current building codes.

They demonstrate their approach on three different configurations of a 10-story steel-frame building. One of the configurations used so-called reduced beam sections (RBS) to connect girders to columns. RBS technology was developed after California's Northridge earthquake in 1994, which resulted in significant structural damage in new and old buildings due to unanticipated brittle fractures in frame connections. Shaped like a dog bone, tapered RBS connections made the frames more ductile -- better able to deflect without breaking.

In this case study, the researchers found that RBS connections do not decrease the risk that a steel-frame building will exceed its design limit when used in a region exposed to high winds or a region exposed to high winds and earthquakes. Consequently, the risk of failure doubled under dual-hazard conditions, when those conditions are of similar severity. However, they note that RBS connections can decrease the risk that limits associated with seismic design will be exceeded during the structure's life.

The researchers are continuing to extend their methodology and are proposing modifications to building codes.


Story Source:

The above story is based on materials provided by National Institute of Standards and Technology (NIST). Note: Materials may be edited for content and length.


Journal Reference:

  1. Chiara Crosti, Dat Duthinh, Emil Simiu. Risk Consistency and Synergy in Multihazard Design. Journal of Structural Engineering, 2011; 137 (8): 844 DOI: 10.1061/(ASCE)ST.1943-541X.0000335

Cite This Page:

National Institute of Standards and Technology (NIST). "Double jeopardy: Building codes may underestimate risks due to multiple hazards." ScienceDaily. ScienceDaily, 14 September 2011. <www.sciencedaily.com/releases/2011/09/110913172713.htm>.
National Institute of Standards and Technology (NIST). (2011, September 14). Double jeopardy: Building codes may underestimate risks due to multiple hazards. ScienceDaily. Retrieved August 1, 2014 from www.sciencedaily.com/releases/2011/09/110913172713.htm
National Institute of Standards and Technology (NIST). "Double jeopardy: Building codes may underestimate risks due to multiple hazards." ScienceDaily. www.sciencedaily.com/releases/2011/09/110913172713.htm (accessed August 1, 2014).

Share This




More Matter & Energy News

Friday, August 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
7 Ways to Use Toothpaste: Howdini Hacks

7 Ways to Use Toothpaste: Howdini Hacks

Howdini (July 30, 2014) Fresh breath and clean teeth are great, but have you ever thought, "my toothpaste could be doing more". Well, it can! Lots of things! Howdini has 7 new uses for this household staple. Video provided by Howdini
Powered by NewsLook.com
Amid Drought, UCLA Sees Only Water

Amid Drought, UCLA Sees Only Water

AP (July 30, 2014) A ruptured 93-year-old water main left the UCLA campus awash in 8 million gallons of water in the middle of California's worst drought in decades. (July 30) Video provided by AP
Powered by NewsLook.com
Smartphone Powered Paper Plane Debuts at Airshow

Smartphone Powered Paper Plane Debuts at Airshow

AP (July 30, 2014) Smartphone powered paper airplane that was popular on crowdfunding website KickStarter makes its debut at Wisconsin airshow (July 30) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins