Featured Research

from universities, journals, and other organizations

Seismic resistance: Model analyzes shape-memory alloys for use in earthquake-resistant structures

Date:
February 9, 2012
Source:
Georgia Institute of Technology Research News
Summary:
Recent earthquake damage has exposed the vulnerability of existing structures to strong ground movement. Researchers are now analyzing shape-memory alloys for their potential use in constructing seismic-resistant structures.

Georgia Tech researchers used a thermal camera to record the variation in surface temperature (top) of a shape-memory alloy experiencing loading and unloading. By inputting this information into their thermo-mechanical model, the researchers were able to accurately predict internal temperature and stress distributions for the material, which is being investigated for use in constructing seismic-resistant structures.
Credit: Reza Mirzaeifar

Recent earthquake damage has exposed the vulnerability of existing structures to strong ground movement. At the Georgia Institute of Technology, researchers are analyzing shape-memory alloys for their potential use in constructing seismic-resistant structures.

"Shape-memory alloys exhibit unique characteristics that you would want for earthquake-resistant building and bridge design and retrofit applications: they have the ability to dissipate significant energy without significant degradation or permanent deformation," said Reginald DesRoches, a professor in the School of Civil and Environmental Engineering at Georgia Tech.

Georgia Tech researchers have developed a model that combines thermodynamics and mechanical equations to assess what happens when shape-memory alloys are subjected to loading from strong motion. The researchers are using the model to analyze how shape-memory alloys in a variety of components -- cables, bars, plates and helical springs -- respond to different loading conditions. From that information, they can determine the optimal characteristics of the material for earthquake applications.

The model was developed by DesRoches, School of Mechanical Engineering graduate student Reza Mirzaeifar, School of Civil and Environmental Engineering associate professor Arash Yavari, and School of Mechanical Engineering and School of Materials Science and Engineering professor Ken Gall.

A paper describing the thermo-mechanical model was published online Feb. 3 in the International Journal of Non-Linear Mechanics. This research was supported by the Transportation Research Board IDEA program.

To improve the performance of structures during earthquakes, researchers around the world have been investigating the use of "smart" materials, such as shape-memory alloys, which can bounce back after experiencing large loads. The most common shape-memory alloys are made of metal mixtures containing copper-zinc-aluminum-nickel, copper-aluminum-nickel or nickel-titanium. Potential applications of shape-memory alloys in bridge and building structures include their use in bearings, columns and beams, or connecting elements between beams and columns. But before this class of materials can be used, the effect of extreme and repetitive loads on these materials must be thoroughly examined.

"For standard civil engineering materials, you can use mechanics to look at force and displacement to measure stress and strain, but for this class of shape-memory alloys that changes properties when it undergoes loading and unloading, you have to consider thermodynamics and mechanics," explained Yavari.

The Georgia Tech team found that the generation and absorption of heat during loading and unloading caused a temperature gradient in shape-memory alloys, which caused a non-uniform stress distribution in the material even when the strain was uniform.

"Shape-memory alloys previously examined in detail were really thin wires, which can exchange heat with the ambient environment rapidly and no temperature change is seen," said Mirzaeifar. "When you start to examine alloys in components large enough to be used in civil engineering applications, the internal temperature is no longer uniform and needs to be taken into account."

To predict the internal temperature distribution of shape-memory alloys under loading-unloading cycles, which could then be used to determine the stress distribution, the researchers developed a model that used the surface thermal boundary conditions, diameter and loading rate of the alloy as inputs.

The team included ambient conditions in the model because shape-memory alloys for seismic applications could operate in a variety of environments -- such as water if used in bridge structures or air if used in building structures -- which would produce different rates of heat transfer. The researchers used a thermal camera to record the variation in surface temperature of shape-memory alloys experiencing loading and unloading.

Using their model, the researchers were able to accurately predict internal temperature and stress distributions for shape-memory alloys. The model results were verified with experimental tests. In one test, they found that a shape-memory alloy loaded at a very slow rate had time to exchange the heat created with the ambient environment and exhibited uniform stress. If it was loaded very rapidly, it did not have enough time to exchange the heat, leading to a non-uniform stress distribution.

"Our analytical solutions are exact, fast and capable of simulating the complicated coupled thermo-mechanical response of shape-memory alloys considering temperature changes and loading rate dependency," said Mirzaeifar.

In future work, the researchers plan to examine more complicated shapes and the effects of combination loading -- tension, bending and torsion -- to optimize shape-memory alloys for earthquake applications.


Story Source:

The above story is based on materials provided by Georgia Institute of Technology Research News. The original article was written by Abby Robinson. Note: Materials may be edited for content and length.


Journal Reference:

  1. Reza Mirzaeifar, Reginald DesRoches, Arash Yavari, Ken Gall. Coupled thermo-mechanical analysis of shape memory alloy circular bars in pure torsion. International Journal of Non-Linear Mechanics, 2012; DOI: 10.1016/j.ijnonlinmec.2012.01.007

Cite This Page:

Georgia Institute of Technology Research News. "Seismic resistance: Model analyzes shape-memory alloys for use in earthquake-resistant structures." ScienceDaily. ScienceDaily, 9 February 2012. <www.sciencedaily.com/releases/2012/02/120209135846.htm>.
Georgia Institute of Technology Research News. (2012, February 9). Seismic resistance: Model analyzes shape-memory alloys for use in earthquake-resistant structures. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2012/02/120209135846.htm
Georgia Institute of Technology Research News. "Seismic resistance: Model analyzes shape-memory alloys for use in earthquake-resistant structures." ScienceDaily. www.sciencedaily.com/releases/2012/02/120209135846.htm (accessed July 28, 2014).

Share This




More Matter & Energy News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

The Carbon Trap: US Exports Global Warming

The Carbon Trap: US Exports Global Warming

AP (July 28, 2014) AP Investigation: As the Obama administration weans the country off dirty fuels, energy companies are ramping-up overseas coal exports at a heavy price. (July 28) Video provided by AP
Powered by NewsLook.com
Shipping Crates Get New 'lease' On Life

Shipping Crates Get New 'lease' On Life

Reuters - Business Video Online (July 25, 2014) Shipping containers have been piling up as America imports more than it exports. Some university students in Washington D.C. are set to get a first-hand lesson in recycling. Their housing is being built using refashioned shipping containers. Lily Jamali reports. Video provided by Reuters
Powered by NewsLook.com
Europe's Highest Train Turns 80 in French Pyrenees

Europe's Highest Train Turns 80 in French Pyrenees

AFP (July 25, 2014) Europe's highest train, the little train of Artouste in the French Pyrenees, celebrates its 80th birthday. Duration: 01:05 Video provided by AFP
Powered by NewsLook.com
TSA Administrator on Politics and Flight Bans

TSA Administrator on Politics and Flight Bans

AP (July 24, 2014) TSA administrator, John Pistole's took part in the Aspen Security Forum 2014, where he answered questions on lifting of the ban on flights into Israel's Tel Aviv airport and whether politics played a role in lifting the ban. (July 24) 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