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.