Background
In the spirit of international center-to-center collaboration, researchers from the National Center for Research in Earthquake Engineering (NCREE) in Taipei and Stanford University are busy preparing to test a full-scale composite moment frame. The test specimen is a three-story, three-bay “RCS” moment frame, consisting of reinforced concrete (RC) columns and composite steel (S) beams. Measuring 12 meters tall and 21 meters long, the frame is among the largest frame tests of its type ever conducted.
The three-story prototype structure is designed for a highly seismic
location either in California or Taiwan, following provisions for composite
structures in the International Building
Code 2000. The frame will be loaded pseudo-dynamically using input ground
motions from the 1999 Chi-Chi and 1989 Loma Prieta earthquakes, scaled to
represent 50%, 10%, and 2% in 50years seismic hazard levels. Following the pseudo-dynamic tests,
quasi-static loads will be applied to push the frame to interstory story drifts
up to 8 percent, which will provide valuable data to validate simulation models
for large deformation response.
The test has three primary objectives. First, it will provide data to evaluate and validate design
provisions for composite moment frames.
Particular topics of investigation include strong-column weak-beam
criterion, composite action of concrete slab and steel beams, integrity of the
pre-cast column and composite beam-column connections, and overall frame
response. Second, the test will
provide valuable information to validate models and computer codes for
nonlinear simulation and performance assessment. Finally, the full-scale test will provide validation to
support the use of innovative composite moment frames as alternatives to conventional
steel and concrete systems for high-seismic regions. Apart from these direct benefits, the frame will provide the
impetus to explore international collaboration and data archiving envisioned
for the NEES initiative.
Researchers are making extensive use of the OpenSees platform to simulate the
nonlinear frame response to input ground motions. This program is currently under development through
universities affiliated with the Pacific Earthquake Engineering Research Center
(PEER). Flexibility-based beam-column fiber elements, beam-column
joint elements, and steel and concrete material models have been calibrated to
data from subassembly tests of RC columns and composite beam-column connections
conducted at NCREE earlier this year.
Researchers at NCREE are applying the PISA2D computer program to
estimate the nonlinear frame responses in order to properly arrange the
hydraulic actuators and instrumentations. Both OpenSees and PISA2D simulations are still underway to finalize
the choice of input ground motions for the pseudo-dynamic tests and to make
“blind” predictions of the frame response.
This project is a collaborative effort between Professors Keh-Chyuan Tsai,
Cheng-Chih Chen, Chin-Tung Cheng and graduate students Chui-Hsin
Chen, Pei-Ching Chen and
Wen-Chi Lai from NCREE and Professor Gregory Deierlein and PhD candidate Paul
Cordova from Stanford. A PEER
fellowship recipient, Cordova has contributed to the frame design and spent
this past summer NCREE to monitor the specimen construction, conduct OpenSees
analyses, and coordinate plans for data archiving. These researchers, along with others from the US and Japan,
will visit NCREE to witness test planned for mid-October.
Financial support for the frame test has been provided by National
Science Council (NSC91-2711-3-319-200-14) and Ruentex Construction and Development
Company of Taiwan. Additional support for planning and US
collaboration has been provided by the NSF (CMS – 9975501)
and PEER.