Toward Rapid Return to Occupancy in Unbraced Steel Frames
Recently at the nees@berkeley lab, engineers subjected a full-scale, two-story steel frame to earthquake forces to test a new Linked Column Frame (LCF) system. The LCF system incorporates steel link elements designed to absorb the brunt of an earthquake's energy so that damage is minimized for the rest of the building. After an earthquake, the sacrificial links can be removed and easily replaced, making post-quake repair faster and less expensive.
A filmed interview with the researchers has been overlaid with test footage. It is available on YouTube.
“We want to design buildings so that they can be rapidly re-occupied and repaired after future large earthquakes,” said lead investigator Peter Dusicka, professor of structural engineering from Portland State University. “Because this system involves modest changes to current steel building designs, we hope that we can begin using it in U.S. building construction in the near future.”
The steel building frame subjected to the test was 30 feet long and 22 feet tall with four computer-controlled hydraulic actuators applying earthquake forces to the structure until the sacrificial links failed. Hybrid tests were conducted on two different frames, each with different structural characteristics as governed by the replaceable components and the contributions of the remainder of the system. The experimental frames were a single bay two story subsystem of a three story six bay structure modeled in OpenSees.
The nees@berkeley lab facilities made such hybrid testing possible, Dusicka said. "Using the hybrid testing methodologies the lab is capable of, we can look at a system behavior at a truly system scale."
These experimental research tests at nees@berkeley are part a project titled "NEESR-II: Toward Rapid Return to Occupancy in Unbraced Steel Frames" funded by the National Science Foundation under award number 0830414.
More information about the project can be found at the nees@berkeley project web site: http://nees.berkeley.edu/Projects/