• Journal of Korean Society of Steel Construction
• /
• v.10 no.4 s.37
• /
• pp.701-708
• /
• 1998

The application of additional post-tensioning tendons has recently been widely considered and requires very little interference with the existing structure. Several bridges on the national roadway designed as the second class were strengthened by external post-tensioning for the capacity enhancement purpose, but much of that strengthening work was not verified analytically as well as experimentally. This paper examines experimentally the behavior of simple composite steel-concrete beams designed as the second class(DB-18) When they are strengthened with external post-tensioning tendon. Test results show that external post-tensioning increases the ultimate load and the magnitude of tendon force increases the yield load but not the ultimate load.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2012.11a
• /
• pp.169-170
• /
• 2012

It is analyzed that constructability of post-tensioning system applying HDPE greased strand that is greased and coated by high density polyethylene on a bare strand in reactor containment building. The improvement of corrosion resistance by greasing and HDPE coating on a strand makes transportation, handling and installation of tendon to be easier. Therefore, serial and repetitive process of post-tensioning composed of construction preparation, tendon installation, stressing and anchoring, grease injection could be improved parallel and lumping process of installation and grouting, stressing and anchoring.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2012.11a
• /
• pp.167-168
• /
• 2012

Analysis on structural effects which are reduction of friction coefficient and increase of tendon area by HDPE greased and large size strand in post-tensioning system of reactor containment building was carried out. Effective ratio of tendon force increases 67% to 83% by HDPE greased strand and vertical, horizontal internal section forces increased maximum 51%, 41% respectively. Tendon quantity could be reduced 30% by large size and HDPE greased strand that can maintain safety of ultimate internal pressure same as at present.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.11 no.5
• /
• pp.123-134
• /
• 2007

A method to determine the initial force of external tendon is proposed to improve the load carrying capacity in existing steel-concrete composite bridges. This method is applied to tensioning external tendons prior to and after concrete replacement for strengthening composite girders. A procedure to determine the number of tendon and initial tendon force is described with the proposed rating factor, which considers the increment of tendon force due to live loads. The method is applied to the improvement of rating factor in an existing composite bridge and its validity is confirmed.

• Structural Engineering and Mechanics
• /
• v.65 no.2
• /
• pp.129-139
• /
• 2018

Post-tensioning (PT) tendons are commonly used for the assembly of modularized concrete members, and tension is applied to the tendons during construction to facilitate the integrated behavior of the members. However, the tension in a PT tendon decreases over time due to steel corrosion and concrete creep, and consequently, the stress on the anchor head that secures the PT tendon also diminishes. This study proposes an automatic detection system to identify tension reduction in a PT tendon using pulsed-eddy-current (PEC) measurement. An eddy-current sensor is installed on the surface of the steel anchor head. The sensor creates a pulsed excitation to the driving coil and measures the resulting PEC response using the pick-up coil. The basic premise is that the tension reduction of a PT tendon results in stress reduction on the anchor head surface and a change in the PEC intensity measured by the pick-up coil. Thus, PEC measurement is used to detect the reduction of the anchor head stress and consequently the reduction of the PT tendon force below a certain threshold value. The advantages of the proposed PEC-based tension-reduction-detection (PTRD) system are (1) a low-cost (< $ 30), low-power (< 2 Watts) sensor, (2) a short inspection time (< 10 seconds), (3) high reliability and (4) the potential for embedded sensing. A 3.3 m long full-scale monostrand PT tendon was used to evaluate the performance of the proposed PTRD system. The PT tendon was tensioned to 180 kN using a custom universal tensile machine, and the tension was decreased to 0 kN at 20 kN intervals. At each tension, the PEC responses were measured, and tension reduction was successfully detected.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.05a
• /
• pp.239-242
• /
• 2005

The purpose of this research was focused on substantiating an effects of tendon-layouts and compressed stress($=f_{pc}$) induced by post-tensioning on seismic performance of post-tensioned flat plate slab-column connection designed as non-participating system. To accomplish this purpose, an experimental research of flat plate exterior slab-column connections subjected to gravity load and reversed lateral displacement history are presented. As a result, tendon-layout is a main variable to influence failure mechanism, dissipated energy and lateral deformation capacity. Furthermore, compressed stress ($=f_{pc}$) induced by post-tensioning enhanced the seismic performance of flat plate slab.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.1034-1039
• /
• 2004

The major objective of this study is to investigate the effects and application of reinforcement for steel plate girder railway bridge by the external prestressing method. It analyzed the mechanical behaviors of non-ballasted railway bridge with ballast reinforced and external post-tensioning reinforced on the finite clement analysis for the static and dynamic behavior. As a result, the reinforcement of ballasted railway bridge the external prestressing method are obviously effective for the additional dead force which is ballast. The analytical study are carried out to investigate the post-tension force decrease bending behavior and deflection in composite bridge for serviceability. To develop two type FEM model which reflect well the post-tension force transverse distribution behavior of servicing bridge. With the comparing the results of railway bridge with ballast which carried out before the post-tensioning with the results of railway bridge with ballast which carried out after post-tensioning, It is investigated that the additional dead load decrease effect and bending behavior of servicing bridge is effect by the post-tensioning. The reinforcement by using the external tendon can be reducing that structure of a degradation phenomenon by unusual stresses due to additional dead load and other problems.

• Journal of Korean Society of Steel Construction
• /
• v.12 no.5 s.48
• /
• pp.549-558
• /
• 2000

In strengthening structure, the external post-tensioning method which secure clearness in the structure analysis process is adopted to bridges as well as architecture structure. In this study, to investigate the behavior of composite beam in the process of post-tensioning, the amount of prestress force loss, the amount of prestressed compression stress at the lower flange and the behavior of lower flange connected with anchorage are analyzed by comparing the results of finite element analysis with the measured results of installed strain gauges. After finishing the post-tensioning, the strengthening effect of external post-tensioning method is analyzed by static loading test. It is also investigated that the strengthening effect of shear section in the harped external post-tensioning specimens.

• International Journal of Highway Engineering
• /
• v.11 no.1
• /
• pp.203-215
• /
• 2009

This study was conducted to develop the design methodology of longitudinal post tensioning for the post-tensioned concrete pavement (PTCP). The longitudinal stress distribution in the PTCP slab was analyzed when post tensioning was applied. Then, the tensile stress distribution in the PTCP slab due to the environmental and vehicle loads needed for the design was investigated. In addition, prestress losses were calculated considering the losses due to the frictional resistance between the slab and underlying layer and due to various reasons related to tensioning. The tensile stresses used for the design were obtained by adding the stresses from the critical conditions under both the environmental and vehicle loads. The prestress losses were obtained by considering actual field conditions. The effective post tensioning amount was determined by considering the design loads including environmental and vehicle loads and various losses, and the effect of the allowable tensile stress on the post tensioning amount was investigated. The initial stage of the design of the longitudinal post tensioning is to obtain the stresses under the design loads and the required prestress determined by subtracting the allowable tensile stress from the design stress. Then, the optimal tendon spacing and the tensioning amount can be obtained by comparing with the effective tensioning amount including various stress losses.

• Journal of Korean Society of Steel Construction
• /
• v.9 no.3 s.32
• /
• pp.441-455
• /
• 1997

The need for rehabilitation of the existing bridges is a growing concern in many countries and has been emphasized in various research reports and publications. Many bridges constructed between 1960s and 1970s in Korea were designed for relatively light traffic volumes, speeds and the weight, thus they are inadequate for the present traffic conditions. This together with some design deficiencies, has resulted in deficiencies of various degrees of many bridges. One strengthening method which has significant advantages is the application of external post-tensioning tendons. This paper presents an example of three span continuous composite bridge strenghtened by application of external post-tensioning.