Excessive strand end slip in prestressed piles

Petrou, MF; Wan, BL; Joiner, WS; Trezos, CG; Harries, KA

dc.contributor.author	Petrou, MF	en
dc.contributor.author	Wan, BL	en
dc.contributor.author	Joiner, WS	en
dc.contributor.author	Trezos, CG	en
dc.contributor.author	Harries, KA	en
dc.date.accessioned	2014-03-01T01:49:52Z
dc.date.available	2014-03-01T01:49:52Z
dc.date.issued	2000	en
dc.identifier.issn	0889-3241	en
dc.identifier.uri	https://dspace.lib.ntua.gr/xmlui/handle/123456789/25954
dc.subject	pile	en
dc.subject	prestress	en
dc.subject	slip	en
dc.subject	strand	en
dc.subject.classification	Construction & Building Technology	en
dc.subject.classification	Engineering, Civil	en
dc.subject.classification	Materials Science, Multidisciplinary	en
dc.subject.other	DEVELOPMENT LENGTH	en
dc.subject.other	CONCRETE	en
dc.subject.other	STRENGTH	en
dc.subject.other	BOND	en
dc.subject.other	GIRDERS	en
dc.title	Excessive strand end slip in prestressed piles	en
heal.type	journalArticle	en
heal.language	English	en
heal.publicationDate	2000	en
heal.abstract	This paper presents the results of a research project that investigated excessive strand end slip observed recently in some prestressed piles. From measurements taken in the field, it is apparent that the problem of excessive initial strand slip is independent of pile shape and size. Strand end slip is evident in piles of different manufacturers in different states in the Southeast. Excessive strand end slip was found in both the top and bottom of the cross section of the piles, although the top portion of the cross section generally exhibited much higher initial slip. Several preventive measures ran be adopted to reduce the excessive strand end slip. These preventive measures include: a) proper concrete mixture proportioning to reduce top bar effect; b) use of higher-strength concrete with the lowest possible slump and setting time; c) assessment of the condition of the strands prior to installation to insure excellent bond characteristics; d) gradual release of prestress, with an optimal release sequence; and e) use of adequate vibration to ensure consolidation. The strand end slip measured at five prestressing plants in the Southeast is considerably higher than the allowable end slip and is expected to affect the pile performance. If the strand slip theory is adopted the strand development length increases substantially die to the excessive strand end slip. A top bar effect factor similar to the one used in reinforced concrete design is recommended. To maintain the excellent quality of precast and prestressed concrete products, manufacturers should adopt a dynamic quality control process that follows the rapid changes in the industry. More tests are necessary to ensure excellent quality such as the Moustafa or an equivalent test, to assess the bond capabilities of the strands, end slip measurements. and direct measurement of the transfer length. Installation of piles should proceed in a manner to alleviate the top bar effects by placing piles alternately in their best and worst directions.	en
heal.publisher	AMER CONCRETE INST	en
heal.journalName	ACI STRUCTURAL JOURNAL	en
dc.identifier.isi	ISI:000165454100011	en
dc.identifier.volume	97	en
dc.identifier.issue	5	en
dc.identifier.spage	774	en
dc.identifier.epage	782	en