Mechanical and Bond Properties of 18-mm- (0.7-in.-) Diameter Prestressing Strands
Publication: Journal of Materials in Civil Engineering
Volume 24, Issue 6
Abstract
For several years, 18-mm- (0.7 in.-) diameter strands have been successfully used in cable bridges and for mining applications. The use of these large diameter strands in pretensioned concrete girders could allow approximately 35% increase in the prestressing force compared to the same number of 15-mm- (0.6 in.-) diameter strands and 92% increase compared to 13-mm- (0.5 in.-) diameter strands. Consequently, this process will allow for longer spans, shallower structural depth, and/or wider girder spacing in bridge construction. For the same prestressing force, the use of 18-mm- (0.7 in.-) diameter strands results in fewer strands to jack and release, fewer chucks, and greater flexural capacity due to lowering the center of gravity of the strands. Despite the advantages of using large diameter strands in pretensioned concrete girders, the lack of data on their mechanical and bond properties hinder their wide use in bridge construction. In this paper, the mechanical and bond properties of 18-mm- (0.7 in.-) diameter strands are evaluated. One hundred and two strand specimens were obtained from different strand producers and production cycles to evaluate the ultimate strength, yield strength, modulus of elasticity, and elongation at two different laboratories. Test results indicated that all strands adequately met the requirements of the ASTM standard A416-06, with the exception of the minimum yield strength requirements (90% of the specified ultimate strength). The power formula for stress-strain relationship was used to provide an accurate predictor of the behavior of strands. Also, 58 strand specimens were tested for their bond in mortar and concrete using the North America Strand Producers (NASP) test method. Test results demonstrated that the bond of 18-mm- (0.7 in.-) diameter strands is proportional to the concrete strength. A formula for predicting the NASP pull-out test value as a function of concrete strength was also developed. In addition, NASP test results for clean and rusted strands were measured and compared at different slip values.
Get full access to this article
View all available purchase options and get full access to this article.
Acknowledgments
The authors thank NDOR for their financial and technical support of this project. The authors are also very thankful for Ivy Steel & Wire and InSteel Industries Inc. for material donation and technical support.
References
ASTM. (2005). “Standard test methods and definitions for mechanical testing of steel products.” A370, West Conshohocken, PA.
ASTM. (2006). “Standard specification for steel strand, uncoated seven-wire for prestressed concrete.”A416, West Conshohocken, PA.
ASTM. (2007). “Standard test method for evaluating bond strength for 15.2 mm (0.6″) diameter prestressing steel strand, grade 270, uncoated, used in prestressed ground anchors.” A981, West Conshohocken, PA.
ASTM. (2008). “Standard test method for compressive strength of hydraulic cement mortars (using 2-in. or [50-mm] cube specimens).” C109/C109M, West Conshohocken, PA.
ASTM. (2001). “Standard test method for flow of hydraulic cement mortar.” C1437, West Conshohocken, PA.
Bryan, J. L. (2008). “Bond and material properties of grade 270 and grade 300 prestressing strands.” M.S. thesis, Virginia Polytechnic Institute and State Univ., Blacksburg, VA.
Logan, D. R. (1997). “Acceptance criteria for bond quality of strands for pretensioned prestressed concrete application.” PCI J.PCIJEE, 42(2), 52–90.
Mattock, A. H. (1979). “Flexural strength of prestressed concrete sections by programmable calculator.” PCI J.PCIJEE, 24(1), 32–54.
Morcous, G., Hanna, K., and Tadros, M. (2010). “Transfer and development length of 0.7 in. diameter strands in pretensioned concrete bridge girders.” 〈http://www.hpcbridgeviews.com/i64/Article3.asp〉 (Apr. 2012).
Morcous, G., Hanna, K., and Tadros, M. (2011). “Use of 0.7 in. diameter strands in precast/prestressed bridge girders.” PCI J.PCIJEE, 54(4), 65–82.
Moustafa, S. (1974). “Pull-out strength of strand and lifting loops.” Concrete Technology Associates Technical Bulletin, 74-B5, Precast/Prestressed Concrete Institute, Chicago.
Peterman, R. J. (2009). “A simple quality assurance test for strand bond.” PCI J.PCIJEE, 54(2), 143–161.
Precast/Prestressed Concrete Institute. (2010). PCI design handbook, (7th Ed.), Chicago.
Preston, H. K. (1985). “Testing 7-wire strand for prestressed concrete—the state of the art.” PCI J.PCIJEE, 30(3), 134–155.
Ramirez, J., and Russell, B. (2008). “Transfer, development, and splice length for strand/reinforcement in high-strength concrete.” NCHRP Report 603, Washington, DC.
Russell, B. W., and Burns, N. H. (2008). “NASP test protocols.” Appendix I, NCHRP Report 603, Washington, DC.
Russell, B. W., and Brown, M. D. (2004). “Evaluation of test methods in assessing bond quality of prestressing strands.” Final Report, NASP Round III Strand Bond Testing, OK.
Russell, H. G., Volz, J. S., and Bruce, R. N. (1997). “Optimized sections for high-strength concrete bridge girders.” Federal Highway Administration (FHwA), FHwA-RD-95-180, Washington, DC.
Schuler, G. (2009). “Producer’s experience with 10,000 psi concrete and 0.7-in. diameter strands.” 〈http://www.hpcbridgeviews.com/i54/Article4.asp〉 (Apr. 2012).
Vadivelu, J., and Ma, Z. (2008). “Potential impact of 0.7-inch strands on precast/prestressed concrete bridge i-girders: Spacing of large diameter strands.” Proc., 2008 PCI National Bridge Conf., Precast/Prestressed Concrete Institute, Chicago.
Information & Authors
Information
Published In
Copyright
© 2012. American Society of Civil Engineers.
History
Received: Jun 7, 2011
Accepted: Nov 10, 2011
Published online: Nov 12, 2011
Published in print: Jun 1, 2012
Authors
Metrics & Citations
Metrics
Citations
Download citation
If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download.