Kwang Ahn Bridge
Korea
Introduction
The port city of Pusan, located at the southern end of the Korean
peninsula, constructed a
road and bridge
transportation system to
connect surrounding
islands blessed with
beautiful natural
resources and with the
new harbours.
Kwang Ahn Bridge, Korea
The Kwang Ahn bridges form a 7.42 km long highway bridge system, comprising a
suspension bridge (200 + 500 + 200 = 900 m), continuous 120 m span truss bridges,
and continuous 60 m span steel box girder bridges. The bridge has 18 m wide twin
decks providing 4 traffic lanes in each direction. The construction site is located in
front of the beach, and the average depth of the sea is about 12 m.
The design criteria are as follows: a maximum velocity of the tidal current of 0.4
m/s, a tidal range of less than 1 m, and a wind velocity of 45 m/s.
Tower
Kwang Ahn Bridge, Korea
The tower of the
suspension bridge, with a
maximum height of 105
m, is a portal steel frame
with three cross beams.
The shape of the upper
and lower cross beams are
semicircular for
aesthetical reasons and
the tower legs are of
octagonal cellular cross section. The base plate of the tower is levelled with mortar
grout and tightened with prestressed anchor bolt.
Cables
The main cables of d 601 mm (void ratio: 20%) are composed of 37
strands, each strand comprising 312 d 5.0 mm wires (tensile strength = 1600 Mpa).
The erection method for the cable is the aerial spinning method. The cable will be
protected against corrosion by the dry air blowing system, and the maximum
tensile force in each cable is 125 MN.
Stiffening Truss Girder
The stiffening truss girder is of Warren type with
verticals. The cross section of girder is of a frame type with a double deck. The
noncomposite orthotropic deck mainly consists of a 14 mm deck plate stiffened by
longitudinal uribs (340x260x8 mm). The stiffening truss girders of the suspension bridge are erected by the vertical lift method for large truss blocks with lifting beams. Each block is 18 m long (two panels of truss) and 4.5 to 5 MN in weight.
The tower comprises three blocks: 31 m lower (9.85 MN), 36.4 m middle (9.45MN), and 33.7 m upper (12.12 MN). These blocks are transported vertically on the 100 MN barge in pairs, and erected at the site with 30 MN floating crane. The verticality of the tower should be L/5000 and the deviation from the vertical of the completed tower is less than 21 mm. The final precision of the tower erection was checked after erection of the tower, and the deviation was found to be less than 10 mm.
Erection of Truss Girder Bridge
The weight of a 120 m span truss is 40 MN. They were assembled at the fabrication yard and transported on a 300 MN barge to the site. The truss was lifted by strand jacks, installed at 4 lifting towers of the barge. After lifting the truss to the specified elevation, the barge was released by adjusting the ballast. The middle part of the truss span was erected after the construction of the approach trusses. The cat heads were installed at the ends of each approach span and the middle span was lifted by strand jacks and connected to be continuous over the three spans.
Kwang Ahn Bridge, Korea
TDV was in charge to execute an independent check of the structural analysis together with TDV’s representative in Korea, BT Consultants Ltd.
 Contract:
 Owner:
 Consultant:
 State of Construction:
 TDV Involvement:
 Definitions of the detailed geometry of the suspended structure.
 Simulation of the whole sequence of construction stages including geometry control, precamber, fabrication shape and the check of structural behaviour in all construction phases.
 Final stage analysis for all relevant loadings including full traffic load analysis for the double deck structure (5 independent traffic lanes per deck).
 Full dynamic analysis for seismic load (calculation of eigenvalues and subsequent modal analysis by using response spectra) based on a “tangent stiffness” approximation for the geometrically nonlinear structure.
