Bond mechanism of 18-mm prestressing strands: New insights and design applications

Canh N. Dang , José R. Martí-Vargas , W. Micah Hale

Abstract

Pretensioned concrete (PC) is widely used in contemporary construction. Bond of prestressing strand is significant for composite-action between the strand and concrete in the transfer and flexural-bond zones of PC members. This study develops a new methodology for quantifying the bond of 18-mm prestressing strand in PC members based on results of a pullout test, the Standard Test for Strand Bond (STSB). The experimental program includes: (a) twenty-four pretensioned concrete beams, using a wide range of concrete compressive strength; and (b) twelve untensioned pullout specimens. By testing beams, the transfer length, flexural-bond length, and development length were all measured. In the STSB, the pullout forces for the strands were measured. Experimental results indicate a significant relationship between the bond of prestressing strand to the code-established design parameters, such as transfer length and development length. However, the code-predictions can be unconservative for the prestressing strands having a low STSB pullout force. Three simplified bond equations are proposed for the design applications of PC members.

Key Words

pretensioned concrete; prestressing strand; bond; transfer length; development length; STSB; design application

Address

Canh N. Dang — 1Department for Management of Science and Technology Development, Ton Duc Thang University, Ho Chi Minh City, Vietnam 2Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam
José R. Martí-Vargas — Institute of Concrete Science and Technology (ICITECH), Universitat Politècnica de València, 4G, Camino de Vera s/n, 46022 Valencia, Spain
W. Micah Hale — University of Arkansas, Department of Civil Engineering, 4190 Bell Engineering Center, Fayetteville, AR 72701, USA

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