Changing neutral axis for effective post-tensioning of long span concrete girder

Tae Min Kim, Yun Mook Lim, Do Hak Kim, Moon Kyum Kim

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Abstract

Pre-stressed concrete (PSC) girder bridges had been introduced in Korea since 1960s and usually adopted for 25 ∼ 35m span length. PSC girder bridges have been proved its excellent performance with cost saving and constructability compared to other types of bridges. So, there have been made many efforts to develop longer span PSC girders. A lot of accomplishments have been made for longer PSC girder bridges by adopting optimized cross sections and pre/post-tensioning. However, in many cases, there are limitations of working space on the construction site in Korea. Also, it is difficult to transport the pre-fabricated pre-tensioning PSC girders from a factory to the sites. That is why the post-tensioning method was widely spread in Korea to overcome those difficulties. Thus, PSC girders with post-tensioning on the construction site are considered as the most appropriate method for PSC in Korea. However, the post-tensioning method has a certain level of friction loss when the post-tensioning is applied over the tendon. Especially the longer span of PSC girder is, the larger the loss becomes. Thus, the longer span girders have larger the loss in tension between end section and middle section, and it is difficult to make accurate estimation the losses. In this study, the research was performed to conduct the development of PSC girders with posttensioning that can solve these problems and makes the longer span possible. For this purpose, different from that adopted by the conventional PSC girder, the tendon was positioned at the bottom of the girder in a straight manner. So it can minimize the instant losses due to friction. The possible negative moment on the end sections of the girder due to the straight positioning of the tendon overcame by applying the variable cross section along the members to change neutral axis closed to the tendon at the ends of the girder. The determination of this profile of tendon was made based on the comparison between various cases using the optimized cross section of girder and cross section evaluation technique. The bridge was designed to meet the allowable stresses proposed by Korean Highway Bridge Design Code through the review of stress at the work stage taking into consideration the manufacturing process of the girder. The real size mock-up girder with 60 meter long was manufactured and tested. As a result, there was an initial bending crack near the 1,400 kN for four point bending test. The load at this time was evaluated to be 2 times larger than the load used for first class bridge in Korea.

Original languageEnglish
Title of host publicationEngineering for Progress, Nature and People
PublisherInternational Association for Bridge and Structural Engineering (IABSE)
Pages1678-1684
Number of pages7
ISBN (Electronic)9783857481352
Publication statusPublished - 2014 Jan 1
Event37th IABSE Symposium on Engineering for Progress, Nature and People - Madrid, Spain
Duration: 2014 Sep 32014 Sep 5

Publication series

NameEngineering for Progress, Nature and People

Other

Other37th IABSE Symposium on Engineering for Progress, Nature and People
CountrySpain
CityMadrid
Period14/9/314/9/5

Fingerprint

Prestressed concrete
Concretes
Concrete beams and girders
Tendons
Friction
Highway bridges
Beams and girders
Bending tests
Industrial plants
Cracks

All Science Journal Classification (ASJC) codes

  • Civil and Structural Engineering

Cite this

Kim, T. M., Lim, Y. M., Kim, D. H., & Kim, M. K. (2014). Changing neutral axis for effective post-tensioning of long span concrete girder. In Engineering for Progress, Nature and People (pp. 1678-1684). (Engineering for Progress, Nature and People). International Association for Bridge and Structural Engineering (IABSE).
Kim, Tae Min ; Lim, Yun Mook ; Kim, Do Hak ; Kim, Moon Kyum. / Changing neutral axis for effective post-tensioning of long span concrete girder. Engineering for Progress, Nature and People. International Association for Bridge and Structural Engineering (IABSE), 2014. pp. 1678-1684 (Engineering for Progress, Nature and People).
@inproceedings{37277cc7a54943dbb1b08cc9ccaac2f7,
title = "Changing neutral axis for effective post-tensioning of long span concrete girder",
abstract = "Pre-stressed concrete (PSC) girder bridges had been introduced in Korea since 1960s and usually adopted for 25 ∼ 35m span length. PSC girder bridges have been proved its excellent performance with cost saving and constructability compared to other types of bridges. So, there have been made many efforts to develop longer span PSC girders. A lot of accomplishments have been made for longer PSC girder bridges by adopting optimized cross sections and pre/post-tensioning. However, in many cases, there are limitations of working space on the construction site in Korea. Also, it is difficult to transport the pre-fabricated pre-tensioning PSC girders from a factory to the sites. That is why the post-tensioning method was widely spread in Korea to overcome those difficulties. Thus, PSC girders with post-tensioning on the construction site are considered as the most appropriate method for PSC in Korea. However, the post-tensioning method has a certain level of friction loss when the post-tensioning is applied over the tendon. Especially the longer span of PSC girder is, the larger the loss becomes. Thus, the longer span girders have larger the loss in tension between end section and middle section, and it is difficult to make accurate estimation the losses. In this study, the research was performed to conduct the development of PSC girders with posttensioning that can solve these problems and makes the longer span possible. For this purpose, different from that adopted by the conventional PSC girder, the tendon was positioned at the bottom of the girder in a straight manner. So it can minimize the instant losses due to friction. The possible negative moment on the end sections of the girder due to the straight positioning of the tendon overcame by applying the variable cross section along the members to change neutral axis closed to the tendon at the ends of the girder. The determination of this profile of tendon was made based on the comparison between various cases using the optimized cross section of girder and cross section evaluation technique. The bridge was designed to meet the allowable stresses proposed by Korean Highway Bridge Design Code through the review of stress at the work stage taking into consideration the manufacturing process of the girder. The real size mock-up girder with 60 meter long was manufactured and tested. As a result, there was an initial bending crack near the 1,400 kN for four point bending test. The load at this time was evaluated to be 2 times larger than the load used for first class bridge in Korea.",
author = "Kim, {Tae Min} and Lim, {Yun Mook} and Kim, {Do Hak} and Kim, {Moon Kyum}",
year = "2014",
month = "1",
day = "1",
language = "English",
series = "Engineering for Progress, Nature and People",
publisher = "International Association for Bridge and Structural Engineering (IABSE)",
pages = "1678--1684",
booktitle = "Engineering for Progress, Nature and People",

}

Kim, TM, Lim, YM, Kim, DH & Kim, MK 2014, Changing neutral axis for effective post-tensioning of long span concrete girder. in Engineering for Progress, Nature and People. Engineering for Progress, Nature and People, International Association for Bridge and Structural Engineering (IABSE), pp. 1678-1684, 37th IABSE Symposium on Engineering for Progress, Nature and People, Madrid, Spain, 14/9/3.

Changing neutral axis for effective post-tensioning of long span concrete girder. / Kim, Tae Min; Lim, Yun Mook; Kim, Do Hak; Kim, Moon Kyum.

Engineering for Progress, Nature and People. International Association for Bridge and Structural Engineering (IABSE), 2014. p. 1678-1684 (Engineering for Progress, Nature and People).

Research output: Chapter in Book/Report/Conference proceedingConference contribution

TY - GEN

T1 - Changing neutral axis for effective post-tensioning of long span concrete girder

AU - Kim, Tae Min

AU - Lim, Yun Mook

AU - Kim, Do Hak

AU - Kim, Moon Kyum

PY - 2014/1/1

Y1 - 2014/1/1

N2 - Pre-stressed concrete (PSC) girder bridges had been introduced in Korea since 1960s and usually adopted for 25 ∼ 35m span length. PSC girder bridges have been proved its excellent performance with cost saving and constructability compared to other types of bridges. So, there have been made many efforts to develop longer span PSC girders. A lot of accomplishments have been made for longer PSC girder bridges by adopting optimized cross sections and pre/post-tensioning. However, in many cases, there are limitations of working space on the construction site in Korea. Also, it is difficult to transport the pre-fabricated pre-tensioning PSC girders from a factory to the sites. That is why the post-tensioning method was widely spread in Korea to overcome those difficulties. Thus, PSC girders with post-tensioning on the construction site are considered as the most appropriate method for PSC in Korea. However, the post-tensioning method has a certain level of friction loss when the post-tensioning is applied over the tendon. Especially the longer span of PSC girder is, the larger the loss becomes. Thus, the longer span girders have larger the loss in tension between end section and middle section, and it is difficult to make accurate estimation the losses. In this study, the research was performed to conduct the development of PSC girders with posttensioning that can solve these problems and makes the longer span possible. For this purpose, different from that adopted by the conventional PSC girder, the tendon was positioned at the bottom of the girder in a straight manner. So it can minimize the instant losses due to friction. The possible negative moment on the end sections of the girder due to the straight positioning of the tendon overcame by applying the variable cross section along the members to change neutral axis closed to the tendon at the ends of the girder. The determination of this profile of tendon was made based on the comparison between various cases using the optimized cross section of girder and cross section evaluation technique. The bridge was designed to meet the allowable stresses proposed by Korean Highway Bridge Design Code through the review of stress at the work stage taking into consideration the manufacturing process of the girder. The real size mock-up girder with 60 meter long was manufactured and tested. As a result, there was an initial bending crack near the 1,400 kN for four point bending test. The load at this time was evaluated to be 2 times larger than the load used for first class bridge in Korea.

AB - Pre-stressed concrete (PSC) girder bridges had been introduced in Korea since 1960s and usually adopted for 25 ∼ 35m span length. PSC girder bridges have been proved its excellent performance with cost saving and constructability compared to other types of bridges. So, there have been made many efforts to develop longer span PSC girders. A lot of accomplishments have been made for longer PSC girder bridges by adopting optimized cross sections and pre/post-tensioning. However, in many cases, there are limitations of working space on the construction site in Korea. Also, it is difficult to transport the pre-fabricated pre-tensioning PSC girders from a factory to the sites. That is why the post-tensioning method was widely spread in Korea to overcome those difficulties. Thus, PSC girders with post-tensioning on the construction site are considered as the most appropriate method for PSC in Korea. However, the post-tensioning method has a certain level of friction loss when the post-tensioning is applied over the tendon. Especially the longer span of PSC girder is, the larger the loss becomes. Thus, the longer span girders have larger the loss in tension between end section and middle section, and it is difficult to make accurate estimation the losses. In this study, the research was performed to conduct the development of PSC girders with posttensioning that can solve these problems and makes the longer span possible. For this purpose, different from that adopted by the conventional PSC girder, the tendon was positioned at the bottom of the girder in a straight manner. So it can minimize the instant losses due to friction. The possible negative moment on the end sections of the girder due to the straight positioning of the tendon overcame by applying the variable cross section along the members to change neutral axis closed to the tendon at the ends of the girder. The determination of this profile of tendon was made based on the comparison between various cases using the optimized cross section of girder and cross section evaluation technique. The bridge was designed to meet the allowable stresses proposed by Korean Highway Bridge Design Code through the review of stress at the work stage taking into consideration the manufacturing process of the girder. The real size mock-up girder with 60 meter long was manufactured and tested. As a result, there was an initial bending crack near the 1,400 kN for four point bending test. The load at this time was evaluated to be 2 times larger than the load used for first class bridge in Korea.

UR - http://www.scopus.com/inward/record.url?scp=84929417106&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84929417106&partnerID=8YFLogxK

M3 - Conference contribution

AN - SCOPUS:84929417106

T3 - Engineering for Progress, Nature and People

SP - 1678

EP - 1684

BT - Engineering for Progress, Nature and People

PB - International Association for Bridge and Structural Engineering (IABSE)

ER -

Kim TM, Lim YM, Kim DH, Kim MK. Changing neutral axis for effective post-tensioning of long span concrete girder. In Engineering for Progress, Nature and People. International Association for Bridge and Structural Engineering (IABSE). 2014. p. 1678-1684. (Engineering for Progress, Nature and People).