• Structural Engineering and Mechanics
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• v.76 no.1
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• pp.67-81
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• 2020

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.

• Magazine of the Korea Concrete Institute
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• v.6 no.6
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• pp.35-41
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• 1994

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.355-358
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• 1999

In recent times, large strands have become increasingly popular in the pretensioned prestressed industry and have found wide applications in varying geometries of sections. However, use of such elements and their behavior in several situations have been questioned with respect to anchoring of these strands in concrete. In addition, the experimental results available on bond are limited and information relating to large strands is rare. This study was conducted to determine the influence of some of the inadequately examined properties on transfer length of prestressing strand. The principle variables considered were strand size, concrete strength and clear bottom cover. The experimental results indicate clearly that concrete strength at transfer and cover size influence transfer length significantly. An attempt was made to suggest prediction equation for transfer length including above parameters.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.25-28
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• 2005

The elastic buckling load or strength of a concentrically loaded slender metal column may be increased many times by reinforcing it with an assemblage of pretensioned stays and rigidity connected crossarm members. The complete system is herein referred to as a 'stayed column'. The purpose of the pretensioned stays and crossarm members is to introduce, at several points along the length of the column, restraint against translation and rotation and thereby decrease the effective unsupported buckling length of the column. This paper verifies that pretensioned cable of stayed column is effective for cyclic load and increases strength of shear wall against earthquake by reinforcing side of wall. Design process of stayed column which satisfies demanded capacity and ductility of wall is presented by analyzing result of experiment.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.95-96
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• 2009

In this paper, the transfer lengths in pretensioned prestressed Ultra High Performance Concrete members are verified to collect the basis data of UHPC increased in practical uses recently. The cover sizes and pretension forces were the main parameters of UHPC.

• Smart Structures and Systems
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• v.17 no.4
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• pp.577-591
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• 2016

In this study, the transfer length of 2400 MPa, seven-wire high-strength steel strands with a 15.2 mm diameter in pretensioned prestressed concrete (PSC) beams utilizing high strength concrete over 58 MPa at prestress release was evaluated experimentally. 32 specimens, which have the variables of concrete compressive strength, concrete cover depth, and the number of PS strands, were fabricated and corresponding transfer lengths were measured. The strands were released gradually by slowly reducing the pressure in the hydraulic stressing rams. The measured results of transfer length showed that the transfer length decreased as the concrete compressive strength and concrete cover depth increased. The number of strands had a very small effect, and the effect varied with both the concrete cover depth and concrete strength. The results were compared to current design codes and transfer lengths predicted by other researchers. The comparison results showed that the current transfer length prediction models in design codes may be conservatively used for 2400 MPa high-strength strands in high-strength concrete beams exceeding 58 MPa at prestress release.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.368-373
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• 2008

This paper describes the dynamic shock effects on the pretensioned concrete member by the detensioning using finite element analysis. The investigation was performed by linear and nonlinear dynamic analysis. In nonlinear dynamic analysis, Brittle Cracking Model was applied for concrete behavior. It was shown that the amplitude of stress wave was significantly decreased when time for cutting of tendon was above 0.05sec. The maximum stress values obtained from linear and nonlinear dynamic analysis was nearly same. However, the position forthe maximum tensile stresses were different.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.139-140
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• 2009

In this paper, the dynamic behavior of pretensioned concrete structures was investigated experimentally during detensioning for two different releasing methods: flame-cutting and hydraulic-jacking. According to the experimental results of strain changes, although detensioning time of hydraulic-jacking is shorter than that of fame-cutting, the prestressing force loss of fame-cutting is larger than that of hydraulic-jacking.

• Steel and Composite Structures
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• v.31 no.3
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• pp.217-232
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• 2019

Modular steel buildings consist of prefabricated room-sized structural units that are manufactured offsite and installed onsite. The inter-module connections must fulfill the assembly construction requirements and soundly transfer the external loads. This work proposes an innovative assembled connection suitable for modular buildings with concrete-filled steel tube columns. The connection uses pretensioned strands and plugin bars to vertically connect the adjacent modular columns. The moment-transferring performance of this inter-module connection was studied through monotonic and cyclic loading tests. The results showed that because of the assembly construction, the connected sections were separated under lateral bending, and the prestressed inter-module connection performed as a weak semirigid connection. The moment strength at the early loading stage originated primarily from the contact bonding mechanism with the infilled concrete, and the postyield strength depended mainly on the tensioned strands. The connection displayed a self-centering-like behavior that the induced deformation was reversed during unloading. The energy dissipation originated primarily from frictional slipping of the plugin bars and steel strands. The moment transferring ability was closely related to the section dimension and the arrangements of the plugin bars and steel strands. A simplified strength calculation and evaluation method was also proposed, and the effectiveness was validated with the test data.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.365-372
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• 1997

This study is aimed for manufacturing a High performance Concrete(HPC) Pile as using steel fibers, investigation the mechanical properties of HPC Pile and proposition the potential application. At this study. We found that mechanical properties(cracking moment and fracture moment) of Pretensioned spun High strength Concrete (PHC) Pile using steel fibers is much superior to without steel fibers. Therefore. we think that using steel fibers in Concrete Pile is to progress flexural strength energy absorption capacity and post-cracking resistance.