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Rapid
In-situ Load Testing
The Need
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Load tests and structural
monitoring are used to gain information regarding the health and performance of an
existing structure. Both are more representative than analytical approaches to evaluate
the structure, especially when little is known about the structure's geometry and
composition. For structures using relatively new materials, such as fiber reinforced
polymer, the use of load tests can answer the question of structures' capability. Yet to
justify the time and expense associated with full-scale load testing is difficult since it
needs a long period of time over a large portion of the structures.
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Shear crack in unstrengthened (white) web and CFRP sheet
(blue) U-wrapped strengthened web.
Deflection vs. Loading
Hydraulic jacks were used to apply loads.
Measurement of deflections using LVDT and the data
acquisition units.
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The Technology
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Rapid in-situ load testing is
intended to be much simpler and can be carried out in a fraction of the time and at a much
lower cost. The testing procedure was originally developed at Center for Infrastructure
Engineering Studies, University of Missouri-Rolla to offer a non-destructive yet
conclusive demonstration of the performance of new construction techniques and
technologies. The key concept of this
technique is the identification of the structural component and its response. The load
test involves applying loads to the structural component through the use of hydraulic
jacks. To gain critical responses in the structure without doing any permanent damage, the
location and magnitude of loads are carefully designed. Deflections and strains induced
are measured, and the structure's performance is evaluated based on the linearity of its
response to loading.
This rapid in-situ load test system is
easily shipped to a site; the equipment contains two gang boxes. The boxes include
hydraulic jacks and a remotely controlled hydraulic pump for applying loads; several
instruments for measuring deflections, strains, elongations, and slopes; and a digital
data acquisition system that records data to a portable computer. |
The Benefits
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This rapid load test system
can be a powerful tool for the assessment of new construction technologies and for
evaluation of structure when little is known about the structure's geometry and
composition. The system also provides the information
of structure with less risk of damage to the entire structure. The system's approach allows a much simpler
evaluation of structures and can be carried out in a fraction of the time and at a much
lower cost. The installation of the system may take 3 to 4 hours depending on the
applications. The actual test takes less than one hour. |
Status
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Currently the rapid in-situ
load test system has been implemented to evaluate seven different structures with bonded
carbon fiber reinforcement. This system is being considered as way of testing fiber
reinforced concrete, concrete structures reinforced with carbon fiber rods, and pultruded
glass fiber reinforced plastic bridge sections. |
Points of Contact
- Dr. Antonio Nanni, Civil Engineering,
University of Missouri - Rolla, 224 Engineering Research Lab, 1870 Miner Circle Rolla, MO
65409-0710, Phone: (573) 341-5113, Fax: (573) 341-6215, Email: nanni@umr.edu
References
- 1999 Nova Award Nominations, The Nova Award,
Construction Innovation Forum, Inc., October 1998
- Rapid In-situ Load Testing of a Two-Way
Post-Tensioned PC Slab Strengthened with CFRP Sheets, http://www.umr.edu/~cies/Project/RapidLoad1/Summary.html
- Rapid In-situ Load Testing of Double-Tee PC
Beams Strengthened with CFRP Sheets, http://www.umr.edu/~cies/Project/RapidLoad2/Summary1.html
Disclaimer Statement
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Neither the Construction
Industry Institute nor Purdue University in any way endorses this
technology or represents
that the information presented can be relied upon without further investigation. |
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