| NSF Org: |
CMMI Division of Civil, Mechanical, and Manufacturing Innovation |
| Recipient: |
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| Initial Amendment Date: | August 16, 2011 |
| Latest Amendment Date: | April 15, 2015 |
| Award Number: | 1131161 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Yick Hsuan
CMMI Division of Civil, Mechanical, and Manufacturing Innovation ENG Directorate for Engineering |
| Start Date: | September 1, 2011 |
| End Date: | August 31, 2015 (Estimated) |
| Total Intended Award Amount: | $95,000.00 |
| Total Awarded Amount to Date: | $111,000.00 |
| Funds Obligated to Date: |
FY 2012 = $6,000.00 FY 2014 = $5,000.00 FY 2015 = $5,000.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
915 BULL ST COLUMBIA SC US 29208-4009 (803)777-7093 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Sumter Street, Suite 510 Columbia SC US 29208-0001 |
| 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): | Structural and Architectural E |
| Primary Program Source: |
01001213DB NSF RESEARCH & RELATED ACTIVIT 01001415DB NSF RESEARCH & RELATED ACTIVIT 01001516DB 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 collaborative research aims at experimentally and theoretically quantifying the structural resilience of a new fiber reinforced earthen masonry system for dwellings in high wind regions. This goal will be achieved by engineering and prototyping stabilized earth blocks and mortar, both enhanced with addition of natural fibers, and verifying the structural response of full-scale walls through physical testing. Engineering of the mortar and blocks will be based on two criteria: optimization of the amount of stabilizer and fibers, and compatibility of block and mortar where the target strengths are defined to force failure in the mortar joints. Engineering of the wall system will be based on the formulation and verification of interaction laws between applicable in-plane and out-of-plane forces. The interaction laws will be based on constitutive models obtained from the characterization of materials and scaled subassemblies. The collaboration involves faculty at the University of South Carolina, the University of Nebraska-Lincoln and the University of Florida, with one PhD student at each institution. The engineering and characterization of the blocks and mortar will be lead by the University of Florida and the University of Nebraska-Lincoln, respectively. The engineering of the walls, including analysis and experimental verification, will be lead by the University of South Carolina, Columbia. The outcome will be a prototype block and mortar combination. The verification of the selected system will be based on proof-tests of full-scale wall specimens under in-plane, out-of-plane, and pendulum impact load simulating the impact energy of representative flying debris, which typically cause human deaths and injuries.
The proposed research will advance knowledge and technology by engineering both the mortar and blocks to enhance damage tolerance, and through the verification of structural system and predictive analytical models based on full-scale experiments. The final outcome of the project will be a novel, affordable, energy efficient and locally appropriate system for rural dwellings that is designed to withstand high wind loads, such as those experienced in the Midwestern and the Southeastern US. The outcomes of this project will be transferred to a broad audience of Indian reservations in Nebraska and to high-school students and teachers through a summer workshop program. New educational material will be incorporated in courses offered to engineering undergraduate and graduate students at the participating universities.
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.
Through this project, it has been shown that it is feasible to design and build earth masonry dwelling structures that are capable of resisting extreme wind loads. To this end, stabilized and compressed earth blocks and earth mortar including less than 10% of Portland cement in weight can be used. For example, wind loads representative of EF3 tornadoes (i.e., wind speeds up to 165 mph) and Category 4 hurricanes can be withstood using structural walls with conventional thickness (e.g., 400 mm) and roof tilt angle (up to 15°), provided that rigid and well-anchored horizontal diaphragm are used. Using a minimum amount of internal (steel) reinforcement is desirable to further reduce wall thickness while providing sufficient out-of-plane strength together with ductility and, most importantly, structural continuity at the foundation-wall and wall-roof connections. Unstabilized earth masonry offers unsuitable strength levels in addition to posing well-documented durability problems.
A high-strength and high-deformability earth masonry system, including compressed and stabilized earth blocks and earth mortar, was engineered and characterized. A local (Lexington, SC) soil was used. This soil is representative of widely available soils in tornado-prone areas in the US (including the “Tornado Alley”). Recycled plastic fiber reinforcement was incorporated in blocks and mortar to toughen the resulting masonry, making it resistant against wind-borne debris. The prototype block, mortar, and block-mortar (masonry) assemblages were tested in the laboratory to reliably quantify strength and deformability properties, and associated failure mechanisms, for use in the practical analysis and design of tornado- and hurricane-resistant dwelling structures.
The proof of concept was verified by means of flying-debris impact experiments on large-scale prototype earth masonry walls, in compliance with FEMA specifications for safety shelters. Experimental evidence highlights the transformation from brittle to deformable material imparted through the incorporation of low-cost recycled plastic reinforcement. As a result, the prototype earth masonry is capable of resisting extreme wind-borne debris impacts. In addition, it was verified that the incorporation of recycled plastic reinforcement in blocks and mortar resulted in a radical shift from brittle to highly deformable behavior in shear, highlighting untapped potential to use earth masonry for earthquake-resistant dwellings.
This project has demonstrated that, through engineering research, it is possible to transform highly sustainable and locally appropriate but fragile earth masonry into a radically stronger and more ductile system. The resulting masonry system lends itself to building affordable and safe dwellings in tornado- and hurricane-prone areas, and shows remarkable promise also for earthquake-resistant dwellings. These outcomes respond to the national need of devising affordable, sustainable and yet high-quality and hazard-resistant construction systems. Responding to this need is essential to tackle rising housing costs, create jobs, and provide safe shelter in hazard-prone areas, also including rural and remote areas where a significant and often underrepresented and underprivileged part of the population lives.
This project was leveraged towards numerous outreach activities, raising awareness of the broader impacts, and fostering an appreciation for the role of engineering education and research in solving real-world problems while broadening participation. In particular, in 2013-2015, over 80 gifted minority high-school students participated in three half-day workshops, including research presentations followed by hands-on active-learning activities and live demonstrations in the civil engineering laboratories.
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