| NSF Org: |
CMMI Division of Civil, Mechanical, and Manufacturing Innovation |
| Recipient: |
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| Initial Amendment Date: | September 1, 2010 |
| Latest Amendment Date: | November 8, 2011 |
| Award Number: | 1041633 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Joy Pauschke
jpauschk@nsf.gov (703)292-7024 CMMI Division of Civil, Mechanical, and Manufacturing Innovation ENG Directorate for Engineering |
| Start Date: | November 1, 2010 |
| End Date: | November 30, 2015 (Estimated) |
| Total Intended Award Amount: | $1,098,262.00 |
| Total Awarded Amount to Date: | $1,110,262.00 |
| Funds Obligated to Date: |
FY 2012 = $12,000.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
701 S NEDDERMAN DR ARLINGTON TX US 76019-9800 (817)272-2105 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
701 S NEDDERMAN DR ARLINGTON TX US 76019-9800 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | NEES RESEARCH |
| Primary Program Source: |
01001213DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
This award is an outcome of the NSF 09-524 program solicitation "George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES) Research (NEESR)" competition and includes the University of Texas at Arlington (lead institution), California State University at Chico (subaward), University of Illinois at Urbana-Champaign (subaward), and the University of Minnesota (subaward). The project will utilize the NEES equipment site at the University of Minnesota, the Multi-Axial Subassemblage Testing (MAST) Laboratory.
Reinforced concrete (RC) structures comprise a large number of the buildings and bridges around the world. The collapse resistance of RC structures is not well understood, even though the collapse resistance is fundamental to the life-safety of building occupants during earthquakes. One of the primary problems is that currently available experimental test data are insufficient to allow researchers to comprehensively understand the collapse behavior of a building and develop accurate computer simulation models to predict when a building would collapse in an earthquake. The objective of this research is to advance knowledge about the collapse behavior and safety of both modern RC frame buildings and high performance fiber reinforced concrete (HPFRC) frame buildings when subjected to extreme earthquakes. This research project involves testing a comprehensive set of full-scale RC components and subassemblages all the way to collapse (nearly all currently available test data stop short of collapse); this comprehensive set of tests has been specifically planned for the purpose of better understanding collapse behavior and creating improved computer simulation models to predict the collapse safety of RC buildings. To improve understanding of how internal damage develops at small scales within the materials, advanced imaging technology (ultrasonic tomography) will be utilized during testing to characterize the progression of internal damage. To improve understanding of the collapse behavior of full large-scale RC buildings, improved computer simulation models will be developed and the collapse of RC building models will be directly simulated.
Intellectual Merit: The following technical contributions are anticipated: (1) new calibrated RC/HPFRC component models, (2) new understanding of collapse resistance behavior of RC frame buildings constructed with RC and HPFRC materials; (3) development of internal imaging technology that could be used as an on-site structural assessment tool; and (4) understanding of the internal damage development and mechanisms for RC columns and slab-beam-column connections subjected to cyclic loading.
Broader Impacts: Results from this study will provide comprehensive information for collapse assessment of newly constructed RC moment frames, as well as moment frames constructed from an emerging high performance material (HPFRC). Such information will be necessary to support widespread use of HPFRC. The development of advanced imaging technology for concrete structures will provide new diagnostic capability to ascertain structural damage within concrete members, for example immediately after an earthquake event. The collapse simulation and imaging techniques developed in this research will be incorporated into educational tools to introduce undergraduate students to earthquake engineering research, the significance of earthquake effects, and the behavior of building structures subjected to collapse-level ground motions. Additionally, undergraduate students at the California State University at Chico will directly participate in the research. The interdisciplinary work plan will promote the development of professionally prepared graduate students who have exposure to a broad range of cross-cutting technologies. Data from this project will be archived and made available to the public through the NEES data repository. This award is part of the National Earthquake Hazards Reduction Program (NEHRP).
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
One of the most commonly used reinforced concrete (RC) earthquake-resistant system for mid- to high-rise buildings is RC moment frame. While modern RC moment frames were designed based on numerous research and engineering experiences in the past decades, a question remains concerning the capability of modern high-rise moment frames to withstand the “Big One” earthquake. The project advances the understanding of the response of modern RC, high-performance fiber-reinforced concrete (HPFRC), and ultra-high-performance fiber-reinforced concrete (UHP-FRC) moment frames subjected to extreme collapse-level earthquake motion. Collapse simulation models of the primary load-resisting components is improved through testing of full-scale columns (28”x28” and 36”x28” for space and perimeter frames respectively) and slab-beam-column sub-assemblages, and the fundamental understanding of internal damage progression is improved through the use of unique internal damage imaging technology based on ultrasonic tomography. Improved simulation of such structures is a critically important research topic: collapse resistance of most structural systems is not well understood, yet collapse resistance is fundamental to the life-safety of building occupants during seismic events. Currently available test data are insufficient for use in developing accurate models for collapse simulation because: 1) nearly all available test data do not continue to deformation levels large enough to exhibit the collapse-level behavior of the component; 2) nearly all available test data were obtained using loading protocols that do not realistically represent the number of cycles that a component would actually undergo if subjected to a collapse-level ground motion; 3) there are limited test data where identical components are subjected to multiple loading protocols, which is needed to allow proper component calibration; 4) nearly all available RC columns test data are limited to 24”×24” or smaller cross sections, which could present unknown size effects; 5) no known experimental data that show the slab participation effects at near-collapse deformation levels. This research addresses these deficiencies in the current state of knowledge and practice. Furthermore, the application of cutting-edge materials and inspection technology are used. Both UHP-FRC and HPFRC are emerging materials that exhibit high ductility tolerance to damage even under large deformations. UHP-FRC has a compressive strength that is five to six times of that of conventional concrete. Currently, only limited data are available to understand the seismic performance of UHP-FRC HPFRC components at full-scale level; this research was structured to increase this understanding. Ultrasonic tomography offers unique capabilities to characterize internal damage within materials, however true practical application of such methods to RC elements has not yet been achieved; accordingly, the necessary development work was an integral part of this planned research. The project utilized the NEES Multi-Axial Subassemblage Testing Laboratory (MAST) facility to test RC, UHP-FRC, and HPFRC frame sub-assemblages to obtain the critically needed test data for collapse simulation of moment frames.
Intellectual Merit of the Work: Key findings are: 1) columns and slab-beam-column sub-assemblages of modern RC moment frames could withstand extreme earthquake loading up to 5% to 10% story drift for high number of large amplitude revered displacement cycles and near-collapse loading history, respectively; 2) although RC members could sustain large earthquake load, the damage in those members are very severe; 3) the large size rebars used in full-scale columns exhibited a lateral buckling mode which lead to an earlier failure of concrete at corners of columns; 4) UHP-FRC column showed very minor...
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