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dc.contributor.authorShao, Yun
dc.contributor.authorDarwin, David
dc.contributor.authorO’Reilly, Matthew
dc.contributor.authorLequesne, Rémy D.
dc.contributor.authorGhimire, Krishna P.
dc.contributor.authorHano, Muna
dc.identifier.citationShao, Y., Darwin, D., O'Reilly, M., Lequesne, R.D., Ghimire, K. P., Hano, Muna, "Anchorage of Conventional and High-Strength Headed Reinforcing Bars, " SM Report No. 117, The University of Kansas Center for Research, Inc., Lawrence, KS, August 2016, 234 ppen_US
dc.description.abstractHeaded bars are often used to anchor reinforcing steel as a means of reducing congestion where member geometry precludes adequate anchorage with a straight bar. Currently, limited data on the behavior of headed bars are available, with no data on high-strength steel or high-strength concrete. Due to a lack of information, current design provisions for development length of headed reinforcing bars in ACI 318-14 limit the yield strength of headed reinforcing steel to 60,000 psi and the concrete compressive strength for calculating development length to 6,000 psi. Current design provisions for developing headed bars in ACI 349-13, which are based on ACI 318-08, apply the same limits on the material strengths (60,000 psi and 6,000 psi, respectively, for headed bars and concrete). These limits restrict the use of headed bars and prevent the full benefits of higher-strength reinforcing steel and concrete from being realized. The purpose of this study was to establish the primary factors that affect the development length of headed bars and to develop new design guidelines for development length that allow higher strength steel and concrete to be utilized. A total of 233 specimens were tested, with four specimen types used to evaluate heads across a variety of applications. Two hundred two beam-column joint specimens, 10 beam specimens with headed bars anchored near the support in regions that are known as compression-compression-tension (CCT nodes, 15 shallow embedment specimens (each containing one to three headed bars for a total of 32 tests), and 6 splice specimens were evaluated. No. 5, No. 6, No. 8, and No. 11 bars were evaluated to cover the range of headed bar sizes commonly used in practice. Concrete compressive strengths ranged from 3,960 to 16,030 psi. A range of headed bar sizes, with net bearing areas between 3.8 and 14.9 times the area of the bar, were also investigated. Some of these heads had obstructions larger than allowed under current Code requirements. In addition, the amount of confining reinforcement, number of heads in a specimen, spacing between heads, and embedment length were evaluated in this study. The results of this study show that provisions in ACI 318-14 and ACI 349-13 do not accurately account for the effect of bar size, compressive strength, or the spacing of headed bars in a joint. The effect of concrete compressive strength on the development length of headed bars is accurately represented by concrete strength raised to the 0.25 power, not the 0.5 power currently used in the ACI provisions. Confining reinforcement increases the anchorage strength of headed bars in proportion to the amount of confining reinforcement per headed bar being developed. Headed bars with obstructions not meeting the Class HA head requirements of ASTM A970 (heads permitted by ACI 318-14 and ACI 349-13) perform similarly to HA heads, provided the unobstructed bearing area of the head is at least 4.5 times the area of the bar. Headed bars exhibit a reduction in capacity for values of center-to-center spacing less than eight bar diameters. These results are used to develop descriptive equations for anchorage strength that cover a broad range of material strengths and member properties. The equations are used to formulate design provisions for development length that safely allow for the use of headed reinforcing bars for steels with yield strengths up to 120,000 psi and concretes with compressive strengths up to 16,000 psi. Adoption of the proposed provisions will significantly improve the constructability and economy of nuclear power plants and other building structures.en_US
dc.description.sponsorshipElectric Power Research Institute, Concrete Steel Reinforcing Institute Education and Research Foundation, BarSplice Products, Incorporated, Headed Reinforcement Corporation, and LENTON® products from Pentair®en_US
dc.publisherUniversity of Kansas Center for Research, Inc.en_US
dc.relation.ispartofseriesSM Report;117
dc.subjectBeam-column jointsen_US
dc.subjectBond and developmenten_US
dc.subjectHeaded barsen_US
dc.subjectHigh-strength concreteen_US
dc.subjectHigh-strength steelen_US
dc.titleAnchorage of Conventional and High-Strength Headed Reinforcing Barsen_US
dc.typeTechnical Reporten_US
kusw.kuauthorDarwin, David
kusw.kuauthorLequesne, Remy D.
kusw.kudepartmentCivil, Environmental & Architectural Engineeringen_US
kusw.oanotes2016/01/06: The institute granted permission to share these on KU Scholarworks: From: Lequesne, Remy D Sent: Wednesday, January 06, 2016 10:13 AM To: Reed, Marianne A. <> Subject: RE: Question re: digital publishing


I’ve heard nothing but favorable feedback about getting the reports at into KU Scholarworks.

How do we get started? Can we try a couple and see how it goes?


************************************************ Rémy Lequesne, PhD

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