FY 2013 Research Problem Statement

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29 Νοε 2013 (πριν από 3 χρόνια και 8 μήνες)

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FY 2013 Research Problem Statement

ODOT Research Section
200 Hawthorne Ave. SE
Suite B-240
Salem OR 97301-5192

Phone (503) 986-2700
Fax (503) 986-2844



I. TITLE

13-056 Ductility of Concrete Compression Members Made with ASTM A 706, Grade 80, High Strength Rebar
Ductility of Concrete Compression Members made with ASTM A 706, Grade 80, High Strength Rebar

II. PROBLEM
In seismic design of compression me
mbers for bridge structures, the potential plastic hinge region needs to be
carefully detailed for ductility in order to ensure that earthquake will not cause collapse. The most important
design consideration for ductility in plastic regions of compression members is the adequacy of transverse and
longitudinal reinforcement in order to confine the compressed concrete to prevent flexural and shear failure.
Earlier tests by Mander et al (1988), and Priestly et al (1996) for mild ASTM A615 or A706, Grade 60 reinforcing
steel have shown that the confinement of concrete by suitable arrangement of longitudinal and transverse
reinforcement in the form of spirals, hoops, ties results in a significant increase in both strength and strain of
compressed concrete. In particular, the strength enhancement from confinement and the slope of the descending
branch of the concrete stress-strain curve have a considerable influence on the strength and ductility of reinforced
concrete compression members.
The stress-strain model of the AASHTO Guide Specifications for LRFD Seismic Bridge Design for confined
concrete need to be updated for ASTM A706, Grade 80 High Strength steel reinforcement. The Seismic Guide
Specifications requirement for concrete modeling, plastic moment capacity, moment curvature analysis, and
ductility need to be investigated for concrete compression members made with high strength steels. The analytical
stress-strain model of confined concretes made with high strength steel reinforcing bars, similar to Mander’s
model of Seismic Guide Specifications Section 8.8.4, need to be developed and adopted by the specifications.
Furthermore, the suitability of high strength steel for joints and members adjacent to plastic hinging regions needs
to be investigated.
III. PROPOSED RESEARCH, DEVELOPMENT, OR TECHNICAL TRANSFER ACTIVITY
The objective of this research is to develop analytical equations supported by experimental testing that allow
engineers to rationally estimate the resistance, stiffness and deformation of concrete compression members
made with ASTM A706, Grade 80 high strength steels. Develop and evaluate analytical models to predict the
performance of compression members made with high strength steel reinforcement subjected to seismic
loading. Establish practical equations for stress strain limits of confined and unconfined concrete and limits for
transverse and longitudinal reinforcement within the confinement regions. An energy balanced approach,
similar to AASHTO Guide Specifications for LRFD Seismic Bridge Design Section 8.4.4 for Concrete
Modeling, based on the strain energy stored in the concrete as a result of the confinement needs to be
investigated. This approach should allow predicting the longitudinal compressive strain in the concrete
corresponding to first fracture or yielding of transverse reinforcement or steel casing.
This research as a minimum should include the following tasks:
Task 1: Literature review summarizing the latest testing and research outcomes using high strength steels.
Task 2: Determine the current design methodologies used in the States and elsewhere to account for the
stress-strain of confined concrete in ductile behavior.
Task 3: Conduct laboratory testing of confined columns made with high strength steel for both longitudinal
and transverse reinforcement subjected to seismic loadings.
Task 4: Develop analytical stress-strain model of confined columns made with high strength steel.
IV. POTENTIAL BENEFITS

ASTM A 706, Grade 80, Rebar has 33% more strength than traditional grade 60 rebar at an estimated cost
premium of approximately $0.04/Lb. Use of this type of rebar would significantly reduce the steel quantity and
thereby result in a significant cost saving for typical bridge projects.
There is a lack of design guidelines in the AASHTO LRFD bridge design specifications and LRFD Guide
Specifications for seismic Bridge Design for accurate calculation of ductility of compressive concrete made
with high strength steel. This research will eliminate the concerns on the applicability of AASHTO
specifications for high strength steels in seismic applications, resulting in significant improvement in the
structural capacity and performance of bridge compression members.
This research meets many of the Business Needs in three major areas: Enhanced Materials, Structural Systems
and Technologies; Enhanced Specifications for Improved Structural Performance; and Efficient Maintenance,
Rehabilitation, and Construction.
V. IMPLEMENTATION
The product of this research is the analytical equations, supported by experimental testing, that will allow
engineers to rationally estimate the resistance, stiffness and deformation of concrete compression members
made with ASTM A706, Grade 80 high strength steels.
Equations and procedures for using ASTM A 706, Grade 80, rebar will be added to the ODOT Bridge Design
and Drafting Manual. Through this manual, all the information needed to successfully use this material in
design will be available to both ODOT bridge designers and consultant bridge designers.
VI. LIST OF REFERENCES (optional)
No records found based on the search criteria from the Research Information Services (TRIS)
http://trisonline.bts.gov/sundev/search.cfm and http://rip.trb.org/search.
The previous related research by
Mander et al (1988), and Priestly et al (1996) are available through ASCE Journals.
VII. CONTACT INFORMATION

Your name: Craig Shike Person Responsible for Implementation: Bruce Johnson
Affiliation: ODOT Bridge Engineering Section
Affiliation: State Bridge Engineer, ODOT Bridge Engineering Section
Telephone: 50
3-986-3323 Telephone: 503-986-3344
Email: Craig.L.SHIKE@odot.state.or.us Email: Bruce.V.JOHNSON@odot.state.or.us