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Tailor Made Concrete Structures – Walraven & Stoelhorst (eds)© 2008 Taylor & Francis Group, London, ISBN 978-0-415-47535-8

Rapid construction of long span precast concrete box girders for IncheonBridge viaducts constructed with FSLM

K.Y. Choi, D.O. Kang, K.L. Park, C.H. Lee, H.Y. Shin & M.G. YoonSamsung Corporation, Seoul, Korea

ABSTRACT: The FSLM (Full Span Launching Method) is being successfully applied to the viaducts of theIncheon Bridge. This method made it possible to construct the long marine viaducts over 8kilometers within3 years. The integrated monitoring of a girder with 50 m span was conducted through the whole constructionsequences. It verified the applicability and efficiency to the rapid construction of marine bridges with FSLM.

1 INTRODUCTION

Incheon bridge is the longest causeway in Korea that isunderway presently.The viaduct part of Incheon bridgeis about 8 km and this comes to the 75% of the wholespan. For the successful construction within the shortperiod, around 3 years, the FSLM has been appliedto the viaduct part(Shin et al, 2007). In this study, abrief introduction and several new concepts applied tothe FSLM are presented for the whole sequences fromfabrication to erection of a 50 m precast concrete boxgirder. Simple static loading test was conducted andthe result verified the safety and stability of the girderwith FSLM.

2 INCHEON BRIDGE PROJECT

Incheon bridge is designed based on the AASHTOLRFD Bridge Design Specification (AASHTO, 1998).

Table 1. General outline of Incheon bridge project.

Spanlength Sub-structure

Item (m) (Drilled Shaft) Super-structure

West Viaduct 5,950 (�1.8, �2.4 or �3.0) + �-shaped bent FSLMApproach 889 (�2.4) BCM

Cable Stayed Bridge Side span 80 + 260 (�3.0) Steel DeckMain span 800 (�3.0) + Inversed Y shaped concrete PylonSide span 260 + 80 (�3.0)

East Approach 889 (�2.4) BCMViaduct 2,450 (�1.8, �2.4 or �3.0) + �-shaped bent FSLM

Sum 11,658 (on shore part is excluded )

It is composed of 3 types of bridges, cable stayedbridge, approach bridge and viaduct. General outlineof this bridge project is presented in Table 1. Themain span of the cable-stayed bridge is 800 m, butthe viaduct is the longest as 8,400 m, which makesup around 75% of the whole spans.

The superstructure of viaduct is designed to be a5 span continuous pre-stressed concrete box girder,of which the length is 50 m for each span with theuniform height of 3 m and the design strength for 28days of applied concrete is 45 MPa. The full viaductis consisted of 336 units and the weight of each oneis around 1350 tons. The simple dimension of eachsegment is shown in figure 1.

In this project, several developed technologies areapplied for rapid construction. Each 50 m-long con-crete box girder is fabricated by 2 day cycle usingsteam-curing system and pre-tension method. Oneproduction line is composed of a series of two sets,where one is for rebar work and the other is for

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Figure 1. Sectional dimension and holding up/down device.

Table 2. Construction sequence.

pre-tensioning, concrete placing and steam-curing.The pre-tensioning method simultaneous in both lon-gitudinal and transverse directions is one of thecore technologies in rapid fabrication. Furthermore,deflected pre-tensioned tendons were designed inthese long span girders using the specially designedholding up/down devices as shown in figure 1.

This speedy fabrication is exquisitely harmo-nized with FSLM using large facilities and spe-cially designed equipments. The overhead crane with1400 ton-capacity pulls up a girder and loads it on abarge. Then, the girder is loaded again on the spe-cially manufactured carrier by F/C(floating crane). It

Figure 2. Static loading test for the check of long-termstability.

is designed to distribute the whole weight to both lines,which elevates the sectional effectiveness of the girderdesign. Transporting by this carrier not only solvesthe access problem of F/C due to the shallow sea butconsiderably accelerates the transporting time. Finally,the girder is settled on a pier by launching gantry andthe launching gantry proceeds to the next pier. Thefabrication and erection sequences of the viaducts atIncheon bridge project are summarized in Table 2.

3 MONITORING PROGRAM

For the check of long-term stability of the erectedgirder, simple static loading test was conducted forone year. The dead load of a new girder on the carrieris the governing load in the serviceability limit state,so some of the repeated loading times were chosen forthe test. Strains and stresses were measured at bothtop and bottom fibers using strain gages and effectivestress meters. The exact weight of the loading wasalso measured and its location was recorded. Figure 2shows the test and its result. Under the repeated load-ing, the influence lines show the same value andconsistent result with the analytical one. At the maxi-mum load, the stress of bottom fiber was maintainedin the compressive region as shown in figure 2. Allthe responses showed the linear-elastic behavior underthe repeated instantaneous loading, so the long-termstability could be verified.

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4 CONCLUSION

– The applicability and efficiency of FSLM has beenverified from the engineering viewpoint.

– The long-term stability of the girder has been ver-ified through the repeated static loading test. Thestress at the bottom fiber was stably maintained incompressive region.

REFERENCES

AASHTO LRFD Bridge Design Specifications, AmericanAssociation of State Highway and Transportation Offi-cials, 2nd Edition, Washington, D.C., USA, 1998.

Shin, H.Y., Okamoto, H., Park, K.L. and Lee C.H., “Man-ufacture and Erection of FSLM Concrete Box Girder atIncheon Bridge”, Magazine of the KCI,Vol.19, No.3, May,2007, pp. 31–37.

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