COMPARISON BETWEEN STEEL ARCH BRIDGES

IN CHINA AND JAPAN

Kangming CHEN1, Shozo NAKAMURA2, Baochun CHEN3, Qingxiong WU3 and Takafumi NISHIKAWA4

1Student Member of JSCE, PhD Candidate, Dept. of Civil and Environmental Eng., Nagasaki University

(1-14, Bukyo-machi, Nagasaki 852-8521, Japan) 2Member of JSCE, Professor, Dept. of Civil and Environmental Eng., Nagasaki University

(1-14, Bukyo-machi, Nagasaki 852-8521, Japan) E-mail: shozo@nagasaki-u.ac.jp

3Professor, College of Civil Eng., University of Fuzhou (2, Xueyuan Road, Minhou, Fuzhou 350108, China)

4Member of JSCE, Assistant Professor, Dept. of Civil and Environmental Eng., Nagasaki University (1-14, Bukyo-machi, Nagasaki 852-8521, Japan)

A review of the current status and progress of steel arch bridges in China and Japan, as well as an outline of the design vehicle load and design method against global buckling for such bridges, is presented in this paper. The existing steel arch bridges in China and Japan were analyzed in terms of year of completion, main span length, structure type, main arch rib form and construction method. It is shown that the steel arch bridge in China has developed rapidly since 2000, characterized by a long main span, while in Japan it has stepped into a fast-growing period since 1955, with medium and small bridges holding a great majority. As for the main span length, most of the bridges have a span from 100m to 250m in China, while majority of bridges are shorter than 150m in Japan. Over 80% of the bridges in China are through and half-through bridge types, and the arch ribs are hingeless structures. However, over 88% of bridges in Japan are deck and through bridge types, and a two-hinged structure was mostly adopted in through and half-through bridges. Sin-gle-hinged and three-hinged arches were seldom adopted in the two countries. The rise-to-span ratios of the arches in China and Japan are mainly in the range of 1:6-1:4 and 1:7-1:5, respectively. Most of the arches both in China and Japan use solid box ribs, and only a small fraction uses truss ribs, in which box sections are mostly adopted for the truss members. The cantilever method and scaffolding method are the two main construction methods used in China and Japan, although some other construction methods have also been developed. Key Words : steel arch bridge, comparison, design vehicle load, design method, main span, structural

type, arch rib, construction method

1. INTRODUCTION

By the material used for the main arch, an arch bridge can be classified into five categories, i.e., stone, concrete, reinforced concrete (RC), concrete filled steel tube (CFST) and steel arch bridges. Steel arch bridges have been constructed only since the late 1800s. Their use began to spread before World War II and significantly expanded after the war, when steel became more available. The steel arch is aesthetically beautiful, highly stiff, efficient in cost, and can be in multiple structural forms, hence it has been widely accepted. Improved materials, products

and design capabilities contribute to make the steel arch bridge one of the main bridge types in the world, even though many bridge types have become avail-able in recent years. Lots of world-class achieve-ments have been witnessed in the field of steel arch bridge design and construction.

Steel arch bridges have been designed and con-structed for about 140 years in Japan since the first cast iron bridge, Shinmachi Bridge, was completed in 1872. Many steel arch bridges have been con-structed with various structure types by employing a variety of construction methods1), 2). A wealth of experience has been accumulated.

Journal of JSCE, Vol. 1, 214-227, 2013

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Very few steel arch bridges had been built before 2000 in China, but more and more steel arch bridges were built later on. Some of them have very long spans. The present span record of the steel arch bridge is held in China3), 4), and some new construc-tion methods have been employed, such as the swing method.

From a brief review of the history of the steel arch bridge in China and Japan, it can be seen that it is beneficial for engineers to learn from the rich ex-periences of Japan and their techniques for design and construction. The quick evolution of steel arch bridges in China is also worth knowing for engineers.

In this context, a large amount of data and litera-ture about steel arch bridges in China and Japan constructed before December of 2011 and 2008, respectively, have been collected, and are analyzed in terms of their history, main span length, structural form, construction method and aesthetics. In addition, a design vehicle load and design method against global buckling for steel arch bridges are outlined. 2. EVOLUTION OF STEEL ARCH

BRIDGES The evolution of arch bridges is closely related to

that of construction materials. Such evolution due to improvement in the technique of steel production is a common matter all over the industrial field. The industrialization of iron and steel enabled their initial use in arch bridges, which was the main long-span bridge type at that time. The world’s first cast iron bridge was constructed in the UK (completed in 1779). Some wrought iron bridges were also built during this period, such as the well-known Garabit Bridge in Massif, France, with a main span of 165m (completed in 1884), and the Maria Pia Bridge in Porto, Portugal, with a main span of 160m (com-pleted in 1877)3).

The steel arch bridge was first established in the USA (Eads Bridge, completed in 1874). Its success promoted the booming development of steel arch bridges worldwide. A number of steel arch bridges, such as the Hell Gate Bridge built in the USA in 1916 (main span: 298m), the Sydney Harbor Bridge con-structed in Australia in 1932 (main span: 503m), the Bayonne Bridge and the New River Gorge Bridge, with main spans of 504m and 518.3m, respectively, in the USA5), were built successively. (1) Evolution in China

Information on 82 steel arch bridges in China has been obtained from a website survey and a literature review6), 7). Among them, the main spans and com-

pletion years of 68 bridges are known. They are shown in Fig. 1 by markers with some representative bridges labelled. The red broken line and blue solid line show the development of the main span and the number of bridges, respectively. Twenty bridges with main spans of more than 200m are listed in Table 1.

It can be seen from Fig. 1 that the development of steel arch bridges in China can be partitioned roughly into two stages using the year 2000. Before 2000, only 10 bridges (13.2%) were built. Compared with steel arch bridges in other countries and RC and CFST arch bridges in China8), 9), the construction of steel arch bridges has obviously lagged behind.

The Dahong Bridge in Tianjin may have been the first steel arch bridge in China. It was first a wooden bridge and was reconstructed into a steel arch bridge in 1887, but was swept away by flood in 1924. Re-construction of the New Dahong Bridge was planed again in 1933, and completed in 1937. It is a through-type steel arch bridge with three spans; the main span is 57.37m10).

For a long time in China, scarcity of material and the backwardness of industrialization prevented a large number of steel bridges from being built. Steel was only used in key bridges crossing major rivers. When the Wuhan Yangtze River Bridge was built in the 1950s, the steel for its construction was imported from the former Soviet Union. Afterwards, it became possible to produce the type 16Mn steel (yield stress:

1935

1940

1945

1950

1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

2010

2015

050

100150200250300350400450500550600

Num

ber o

f brid

ges

New Dahong Bridge Und

er C

onstr

uctio

n

Chaotianmen BridgeLupu Bridge

Xinguang BridgeCaiyuanba Bridge

Jiujiang Yangtze River Bridge

Yingsuihe Bridge

Guandu BridgeMidi Bridge

Main

span

, m

Dukou Bridge

Completion year

0

10

20

30

40

50

60

70

Fig. 1 Main spans and completion year of steel arch

bridges in China.

Fig. 2 No. 2 Panzhihua Bridge.

215

343MPa, carbon content: 0.16%, low alloy) to build the Nanjing Yangtze River Bridge in the 1970s. However, this kind of steel showed quick degrada-tion in strength and ductility with an increase in thickness. A new type of steel, 15MnVNi (yield stress: 420MPa, carbon content: 0.15%, main alloy: manganese, vanadium and nickel) was developed and used in the Baihe Bridge in 1976. But poor weldability prevented it from further use except in the Jiujiang Bridge in 1992. It was really embar-rassing that no steel other than the 16Mn could be used in bridge engineering at that time11).

Very few steel highway bridges had been built before the 1990s. The No. 2 & 3 Panzhihua Bridges were two representatives from this early time. The former, shown in Fig. 2, is a steel box arch bridge with a main span of 180m, completed in 1966. The latter is a steel truss arch bridge with a main span of 180m, completed in 1969. Surely, the 16Mn steel type was the only choice12). With the slow devel-opment in steel arch bridge for almost 26 years, the Jiujiang Yangtze River Bridge, with a main span of 216m, was completed in 1992.

As a result of China’s Economic Reform and Opening Up from 1978, the steel industry has de-veloped rapidly and they are now the top producer in the world. There are rich types of steel products available now. At present, steel bridges in China mainly adopt the Q345q (Q denotes yield stress; number 345 means yield stress is 345MPa; q denotes

steel type for bridge) and the Q370q types, and more and more bridges use the Q420q steel. There is a tendency to use high-performance steel. Therefore, more and more steel bridges have been constructed in the last three decades of large-scale infrastructure construction. Steel arch bridges are becoming more popular even after many long-span steel cable-stayed bridges and steel suspension bridges have been built.

In the decade after 2000, 66 bridges were built, which accounted for 86.8% of the total. Most long-span bridges were built in this period, 60 bridges with main spans of 100m or longer, the av-erage main span being 216m. In 2003, a long-span steel arch bridge, the Lupu Bridge in Shanghai, was built (shown in Fig. 3). The completion of this bridge set a new world record for the steel arch span. The bridge type is a half-through steel tied arch. The main arch spans 550m, with a rise-to-span ratio of 1:5.5, and the other two side arches span 100m each. The steel used for the bridge is the normalized structural steel S355N, in accordance with the German indus-trial standard DIN10113-1993 for weldable fine-grained steel13).

Afterwards, several long-span steel arch bridges were built successively, such as the Xinguang Bridge in Guangzhou, with a main span of 428m (steel truss arch bridge, 2006); the Caiyuanba Yangtze River Bridge in Chongqing, with a main span of 420m (steel box arch bridge, 2007); the Chaotianmen Bridge in Chongqing, with the world’s longest main

Table 1 Long-span steel arch bridges in China (main span≥200m).

Order Bridge Name Main Span (m)

Structure Type Completion Year

1 Zhongzhaiwan Bridge in Xiamen 208 Half-through 2004 2 No.2 Mengshuai Bridge in Taiwan 210 Through 1996 3 Jiubao Bridge in Hangzhou 210 Through 2011 4 Xiangjiang Bridge in Changsha 210 Through Under construction 5 Jiujiang Yangtze River Bridge 216 Double-deck 1992 6 Rongjiang Railway Bridge in Shantou 220 Half-through 2011 7 Yuantongjinyan Yellow River Bridge in Lanzhou 230 Half-through Under construction 8 Dongpingshuidao Railway Bridge in Guangdong 242 Half-through 2009 9 Dongping Bridge in Foshan 300 Half-through 2006

10 Nanning Bridge in Guangxi 300 Half-through 2009 11 Dashengguan Yangtze River Bridge in Nanjing 336 Half-through 2009 12 Wangzhou Yangtze River Railway Bridge in Chong-

360 Half-through 2005

13 No.2 Hengqin Bridge in Zhuhai 360 Half-through Under construction 14 Daninghe Bridge in Chongqing 400 Deck 2010 15 Caiyuanba Yangtze River Bridge in Chongqing 420 Half-through 2007 16 Xinguang Bridge in Guangzhou 428 Half-through 2006 17 Mingzhou Bridge in Ningbo 450 Half-through 2011 18 Xijiang Railway Bridge in Zhaoqing 450 Half-through Under construction 19 Lupu Bridge in Shanghai 550 Half-through 2003 20 Chaotianmen Bridge in Chongqing 552 Half-through 2007

216

span of 552m (steel truss arch bridge, 2007, Fig. 4); the Daninghe Bridge in Chongqing, with a main span of 400m (steel truss arch bridge, 2010).

It is expected that the upper limit of the span of the steel arch bridge is far from being reached. Theo-retically, with the current construction technology

and material, the span limit of the steel arch bridge can be 1200m10).

(2) Evolution in Japan

Detailed information on 1509 steel arch bridges has been obtained from a website survey14) and a

Fig. 3 Lupu Bridge in Shanghai. Fig. 4 Chaotianmen Bridge in Chongqing.

Table 2 Long-span steel arch bridges in Japan (main span≥200m).

Order Bridge Name Main Span (m) Structure type Completion Year 1 Roppouzawa Bridge 200 Deck 1975 2 Togatani Bridge 200 Deck 1978 3 Miyagasenijinno Bridge 200 Deck 1985 4 Ryuten Bridge 200 Deck 1988 5 Shimminasegawa Bridge 200 Deck 1990 6 Maizuru yuragawa Bridge 200 Half-through 1996 7 Yakatagawa nijino Bridge 202 Deck 2003 8 Kitakami Bridge 208 Through 2002 9 Kitakyushu kuko renraku Bridge 210 Half-through 1999

10 Karematsuzawa Bridge 210 Deck 2006 11 Okususohana Bridge 215 Deck 2003 12 Rokko island Bridge 215.4 Double-deck 1992 13 Saikai Bridge 216 Deck 1955 14 Kobe Bridge 217 Double-Deck 1970 15 Utsumi Bridge 219.6 Through 1988 16 Seiun Bridge 220 Deck 1983 17 Okuaso Bridge 221 Deck 1989 18 Takiyamakyo Bridge 230 Deck 1997 19 Kushimoto Bridge 230 Half-through 1999 20 Shima Bridge 232 Through 2004 21 Otonase Bridge 236 Through 1993 22 Potopia Bridge 250 Through 1979 23 Imariwan Bridge 250 Half-through 2000 24 Nishinomiya kou Bridge 252 Through 1994 25 Shinhamadera Bridge 254 Through 1991 26 Kishiwada Bridge 255 Half-through 1993 27 Jogakura Bridge 255 Deck 1994 28 Chitose Bridge 259.9 Through 2003 29 Saigo Bridge 260 Half-through 1977 30 Ushine Bridge 260.1 Half-through 2007 31 Eto Bridge 275 Half-through 1994 32 Oamigawa Bridge 280 Deck 1999 33 Yumemai Bridge 280 Half-through 1999 34 Omishima Bridge 297 Half-through 1979 35 Shinkizugawa Bridge 305 Half-through 1993 36 Kuko Bridge 380 Deck 2008

217

literature review. Among them, the main spans and completion years of 1467 bridges are known. They are shown in Fig. 5 by markers with some repre-sentative bridges labelled. The red broken line and blue solid line show the development of the main span and the number of bridges, respectively. Thir-ty-six bridges with main spans of more than 200m are listed in Table 2.

It can be seen from Fig. 5 that the number of steel arch bridges in Japan had been increasing since 1920, almost stopped increasing between 1935 and 1955, increased conspicuously between 1955 and 2004, and then slowed down from 2004. The evolution of steel arch bridges in Japan can be partitioned roughly into two stages using the year 1955.

The Shinmachi Bridge was the first iron arch bridge constructed from imported cast iron in 1872. During the period 1883-1885, the Mikohata Bridge and Habuchi Bridge were constructed. They disin-tegrated and were reconstructed in parks as precious heritages. Now, they are the oldest existing cast iron arch bridges in Japan. The early arch bridges in Ja-pan were designed and manufactured with Western technology.

The Yamaga Bridge, with a length of 164.2m and height of 27m, was established in 1910. It was the largest two-hinged steel arch bridge and one of the representative bridges constructed by domestic technology in the Meiji Era. In 1913, the first through-type steel arch bridge, with a length of 41.4m, was constructed—the old Yatsuyama Bridge. Subsequently, some through-type steel arch bridges were constructed, such as the old Taisho Bridge, with a relatively larger span of 91.5m (two-hinged, completed in 1915); Rokugo Bridge, with a main span of 67m (completed in 1925); Choroku Bridge, with a main span of 73m (completed in 1927). The Juso Bridge was the first railway tied steel arch bridge, with a main span of 64m (completed in 1932). With the technological development of the steel arch bridge in Japan, the Arakawa Bridge with three spans was constructed in 1928. The three-hinged Sakuranomiya Bridge, with a main span of 104m, was constructed in 1931. Some combined-system bridges were also constructed. For example, Sumidagawa Bridge and Owari Bridge with rigid girder flexible arch ribs were constructed in 1932 and 1933, respectively1), 2).

Although the technology for steel arch bridges had kept developing and improving, just a few bridges were constructed before 1955 due to limited steel production. From 1872, when the first cast iron bridge was completed, to 1955, only 112 bridges (7.6%) were built in this duration of 85 years. Only 4 bridges’ main spans are 100m or longer. The longest

main span is 110m. Before 1955, the annual pro-duction of steel for bridges in Japan was 50 thousand tons, and most of them were employed in con-structing truss bridges.

After 1955, the steel production for bridges in-creased with the rapid economic growth, which came to a peak of 600 thousand tons in 1971. Although the steel production for bridges decreased to 350 thou-sand tons in 1975 because of the oil crisis, it re-bounded to 550 thousand tons in 1980, and has kept the output at more than 550 thousand tons for two decades2).With the developments in theory and in material, steel arch bridges of various structural types and with large spans and attractive appearances were constructed. In the decades after 1955, 1355 bridges were constructed, which accounted for 92.4% of the total. There are 531 bridges with a main span of 100m or longer, and the average main span is 98.5m. Saikai Bridge, with a main span of 216m (steel truss arch bridge, 1955, Fig. 6); Mitou Bridge, with a main span of 131.2m (first steel box arch bridge with X-shape, 1969); Kobe Bridge, with a main span of 217m (first steel box arch bridge with

1870

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1910

1920

1930

1940

1950

1960

1970

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1990

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2010

0

50

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Shinmachi Bridge

Kuko Bridge

Shinkizugawa Bridge

Omishima Bridge

Sakuranomiya Bridge

Main

span

, m

Completion year

Saikai Bridge

0

200

400

600

800

1000

1200

1400

1600

Num

ber o

f brid

ges

Fig. 5 Main spans and completion years of steel

arch bridges in Japan.

Fig. 6 Saikai Bridge in Nagasaki.

Fig. 7 Kuko Bridge in Hiroshima.

218

double-deck, 1970); Omishima Bridge, with a main span of 297m (steel box arch bridge, 1979); Yumemai Bridge, with a main span of 280m (mov-able steel arch bridge, 1999); Kuko Bridge, with a main span of 380m (the largest steel truss arch bridge in Japan, 2008, Fig. 7), are the representative ex-amples. 3. DESIGN TRAFFIC LOAD (1) Chinese code

For designing highway bridges in China, loads are specified in the “General Code for Design of High-way Bridges and Culverts”15), 16). The up-to-date code JTG D60-200415) was published to supersede the primary code JTJ 021-8916). In JTJ 021-89, four classes of truck-train loads, i.e., Vehicle-over 20, Vehicle-20, Vehicle-15 and Vehicle-10, were used as the standard traffic live loads. The number in the class name indicates the gross weight of a truck, e.g., the truck weight is approximately 20t (200 kN) in Vehicle-20. Fig. 8 shows the truck-train load of Vehicle-over 20 and Vehicle-20 in JTJ 021-89. In JTG D60-2004, the system of truck-train loading is superseded by equivalent lane loading, which con-sists of a uniform load accompanied by a concen-trated load, as shown in Fig. 9. Two equivalent lane loadings, Highway-I and Highway-II, are adopted to replace Vehicle-over 20, Vehicle-20 and Vehicle-15, while Vehicle-10 is abolished. Most of the steel arch bridges in China mentioned in this paper were de-signed according to Highway-I and Highway-II of the JTG D60-2004. The uniform load qk for High-way-I is 10.5 kN/m, and concentrated load Pk is 180 kN and 360 kN when the main span of the bridge is shorter than 5m and longer than 50m, respectively. When the main span falls from 5m to 50m, Pk can be interpolated in a linear manner. The loadings for Highway-II are 0.75 times those for Highway-I. The vehicle lane is determined according to the width of the bridge.

Pedestrian loads are 3.0 kN/m2 and 2.5 kN/m2 when the main spans are shorter than 50m and longer than 150m, respectively. For the main span from 50m to 150m, the pedestrian load may be interpolated in a linear manner. (2) Japanese code

The “L-load” is provided in specifications for highway bridges for the design of the main compo-nents of the steel arch bridge 17). The L-load consists of two kinds of uniform loads, p1 and p2. The dis-tribution and values of p1 and p2 are provided in Fig. 10 and Table 3, respectively. The width (lateral

direction) subjected to uniform loads p1 and p2 is 5.5m maximum, and the remaining portion is sub-jected to half-values of p1 and p2.

The same uniform load as p2 is specified as the pedestrian loads.

4. DESIGN METHODS AGAINST GLOBAL BUCKLING

(1) Chinese code18)

In-plane stability of the arch should be checked under the following assumptions: The arch rib is a member subjected to axial compressive load, the length of the member relates to the span of the bridge, and no favorable effects of suspenders and tie bars exist. The effective length is determined by the rise-to-span ratio and the structural style, since the critical load of steel arch bridges is significantly affected by those two parameters.

The critical flexure force Ncr of the arch for

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1307070 13013070

15m4m

1.4m

15m 4m15m4m10m15m4m

(a) Vehicle-20 (unit: kN)

140140

7m

1.4m1.4m

10m4m

13070

4m 15m 10m 4m 15m 4m15m 3m 15m

70 130 13070 70 130120

30 120

(b) Vehicle-over 20

Fig. 8 Truck-train load of Vehicle-20 and Vehicle-over 20 in JTJ 021-89 (unit: kN).

Pk

qk

Fig. 9 Lane load in JTG D60-2004.

Uni

form

load

P2

Uni

form

load

P1

Late

ral d

irect

ion

Longitudinal direction

P2/2

P2P2

/2

P 1P 1

/2P 1

/2

P2/2 P2/2

P2/2 P2/2

P2P2 P1+P2

(P1+P2)/2

(P1+P2)/2

Applied length D

Uniform load P2

Uniform load P1

Fig. 10 L-load in Japanese code.

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in-plane buckling is expressed by

20

2

LEIN x

crπ

= (1)

where E is the Young’s modulus of the arch rib, Ix is the geometrical moment of inertia of the arch rib and L0 is the effective length of the arch rib, which can be obtained by the following equation: LKLfL ⋅= /80 π (2)

where L is the span length of the bridge, f is the arch rise and K is a parameter determined by the structural style and rise-to-span ratio of the arch rib. The value of K is given in Table 4. When the rise-to-span ratio comes between the values shown in Table 4, it may be calculated through linear interpolation.

The Chinese code specifies that the arch rib can be treated as a Vierendeel truss with length equal to the arch axis for approximate checking of out-of-plane stability, and the truss is subjected to longitudinal force N on the quarter point of the arch rib. N is de-termined by the following equation: mHN φcos/= (3)

where H is the horizontal thrust and φm is the angle of the arch axis to the horizontal direction on the quarter point. The critical axial force Ncr is calcu-lated by

2

2

0 SEINcr

πα= (4)

where I is the geometrical moment of inertia of two chords around the common axis (central longitudinal axis of the bridge) and S is the length of the arch axis. The variable α0 is calculated as follows:

−⋅++

=

µπ

α

11

26121

1

2

20

yb EIa

EIab

SEI

(5)

where a is the panel length, b is the arch rib spacing,

Ib is the geometrical moment of inertia of the trans-verse bracing around the vertical axis and Iy is the out-of-plane geometrical moment of inertia of the arch rib. The μ-value can be obtained using equation (6):

y

cr

EIaN

2

2

2πµ = (6)

(2) Japanese code17)

The entire structural system of a steel arch bridge, which is a narrow, long-span structure, has a ten-dency to buckle laterally away from the arch plane, so the Japanese code establishes rules and regula-tions for verification of out-of-plane buckling. If the arch axis forms a symmetrical parabola in the verti-cal plane, and if lateral bracing and sway bracing are installed in accordance with the provisions, the verification of out-of-plane buckling may be per-formed using the following equation: cagAH σ85.0/ ≤ (7)

Table 3 L-load.

Vehicle load

Uniform load P1 Uniform load P2

Applied length D

Vehicle load (kN/m2) Vehicle load (kN/m2) For calculating

moment For calculating

shear force L≤80 80<L≤130 130<L

A-class 6m 10 12 3.5 4.3-0.01L 3

B-class 10m

Table 4 Value of K.

f/L 0.1 0.2 0.3 0.4 0.5 0.6 0.8 1.0 Fixed arch 60.7 101.0 115.0 111.0 97.4 83.8 59.1 43.7

Two-hinged arch 28.5 45.5 46.5 43.9 38.4 30.5 20.0 14.1 Three-hinged arch 22.5 39.6 46.5 43.9 38.4 30.5 20.0 14.1

Fig. 11 Loading state to be used for verifying

out-of-plane buckling.

Table 5 Value of βz.

Section Rise-to-span ratio f / L 0.05 0.10 0.20 0.30 0.40

IZ=constant 0.50 0.54 0.65 0.82 1.07 IZ=IZC / cosφx 0.50 0.52 0.59 0.71 0.86

220

where H is the horizontal component of the axial force acting on the members of one side arch under the loading shown in Fig. 11, Ag is the mean value of the gross cross-sectional area of the members of one side arch, and σca is the allowable axial compressive stress at the L/4 point of one side arch. In this regard the effective buckling length and radius of gyration is to be calculated as follows:

Ll zϕβ= , ggz AbAIr /

2

2

+= (8)

where Iz is the mean value of the geometrical moment of inertia around the vertical axis of the members of one side arch, b is the arch rib spacing and βz takes the values shown in Table 5. When the value of f/L falls between the values given in Table 5, βz may be interpolated in a linear manner. Values of φ are specified as follows: for a through stiffened arch, φ = 1-0.35k; for an upper-deck stiffened arch, φ = 1+0.45k; and for a mid-height-deck stiffened arch, φ = 1. Here, k is the ratio of the load shared by the hangers or shoring to the total load in the loading state shown in Fig. 11. In this regard, when the arch and stiffening girder in an upper-deck stiffened arch are not rigidly linked at the arch crown, the value of k is set at 1. 5. DISTRIBUTION OF MAIN SPAN

LENGTH Figs. 12 and 13 show the distribution of main span

length in China and Japan, respectively. The main span of steel arch bridges in China is mostly from 100m to 250m, for around 48 out of 76 (63.2%). The average main span length of the steel arch bridge in China is 172m. Meanwhile, more than 10 steel arch bridges with a main span of 300m or more have been constructed. There are some great rivers in China, i.e., the Yangtze River and the Yellow River. In order to cross such rivers using one span with a high stiff-weight ratio, an arch bridge is employed in some railway and rail-cum-road bridges. Some highway steel arch bridges with a large main span are con-structed focusing on the pursuit of a novel and graceful appearance. Most steel arch bridges in Ja-pan have short and medium main span lengths. The average main span length is 95m. Although the his-tory and distribution of main span length of steel arch bridges in China and Japan are different, the main span of majority of steel arch bridges in both coun-tries are from 100 to 150m, accounting for 36.8% and 26.7%, respectively. It means that the steel arch bridge is competitive from 100 to 150m since the

arch bridge can be the most economical bridge type in the span range of 100 to 200 m in China7) and 90 to 150 m in Japan19).

6. STRUCTURE TYPE (1) Deck, half-through, through and double-deck

steel arch bridges There are many forms of steel arch bridges. With

respect to the relative position of the bridge deck and the arch rib, steel arch bridges can be categorized into deck, half-through and through types. Although most of the bridges have only one deck, there are some bridges of double-deck type. As shown in Fig. 14, in the 80 steel arch bridges of China with deck relative location known, there are 9 (11.3%) deck bridges, 32 (40.0%) half-through bridges, 35 (43.7%) through bridges and 4 (5.0%) double-deck bridges.

02468

1012141618202224262830

Double-deck Deck Half-through Through

Num

ber o

f stee

l arc

h br

idge

s

Main span, m60055050045040035030025020015010090807060500

Fig. 12 Span distribution of steel arch bridges in China.

050

100150200250300350400

Nu

mbe

r of s

teel a

rch

brid

ges

Un-known Double-deck Deck Half-through Through

Main span, m

60055050045040035030025020015010090807060500

Fig. 13 Span distribution of steel arch bridges in Japan.

050100150200250300350400450500550600650

Num

ber o

f ste

el ar

ch b

ridge

s in

Chin

a

N

umbe

r of s

teel

arch

brid

ges i

n Ja

pan

Double-deckThroughHalf-through

Bridge in China Bridge in Japan

Deck0369

1215182124273033363942

Overall structure type Fig. 14 Number of steel arch bridges classified by structure type.

221

In the 1165 steel arch bridges of Japan with deck relative location known, there are 369 (31.7%) deck bridges, 129 (11.1%) half-through bridges, 662 (56.8%) through bridges and 5 (0.4%) double-deck bridges.

The through and half-through types of steel arch bridges are generally suitable for plain and urban areas. Deck-type steel arch bridges consist of an arch rib and a spandrel structure. It is ideal for crossing a valley with sound rock walls. In order to match the lightweight but strong characteristics of the arch, the spandrel structure of the bridge is usually con-structed with steel, accompanied by a steel-concrete composite decking system.

Fig. 12 shows that the through and half-through type steel arch bridges are employed mainly when the main span is longer than 80m in China. There exist only several deck-type steel arch bridges since they are generally uneconomic in mountainous areas compared to RC and CFST arch bridges, if there are no navigation and traffic requirements in site and construction time is sufficient. Fig. 13 shows that the through-type steel arch bridges in Japan are em-ployed mainly when the main span is shorter than 200m. Furthermore, Japan is a hilly, mountainous and earthquake-prone country. Consequently, deck types are commonly adopted. (2) Three-hinged, two-hinged, single-hinged and

hingeless steel arch bridges With respect to the articulation of the main arch,

they can be classified into four categories, i.e., three-hinged, two-hinged, single-hinged and hinge-less (or fixed) steel arch bridges.

For single-hinged and three-hinged arch bridges, the existence of a hinge in the arch crown increases the tendency of suffering damage from heavy impact loads, and the maintenance of the hinge is difficult. Therefore, there are very few single-hinged and three-hinged arch bridges worldwide. The two-hinged and fixed steel arch bridges are fre-quently employed, and mainly the two-hinged form was adopted in early times.

All steel arch bridges in China are hingeless since most of them were built in the last decade, and traffic in China is much heavier than in Japan. The articu-lation of the steel arch bridge in Japan is shown in Fig. 15. Only one bridge, Sakuranomiya Bridge, is three-hinged, and 7 bridges are single-hinged. However, they are different from the traditional one-hinged bridge having a hinge in the arch crown. They are asymmetrical, and the elevation of the two springings is different from each other. The higher springing is fixed, while the lower one is hinged, as in the Shibichari Bridge, completed in 1989 with a

67.59%

0.77%

31.53%0.11%

Three-hinged Two-hinged Single-hinged Hingeless

Fig. 15 Articulation of main arch in Japan.

02468

101214

1/4-

1/3

1/4

1/5-

1/4

1/5

1/6-

1/5

1/6

1/7-

1/6

1/8-

1/7

1/8

1/9-

1/8

Num

ber o

f br

idge

s in

Chin

aRise-to-span ratio

Bridge in China Bridge in Japan

050100150200250300350400450

Num

ber o

f br

idge

s in

Japa

n

Fig. 16 Rise-to-span ratios of steel arch bridges.

0 50 100 150 200 250 300 350 400 450 500 550 600

1/101/81/71/61/51/4

1/3

Rise

-to-sp

an ra

tio

Main span, m

Steel arch bridges in Chian Steel arch bridges in Japan

1/2

Fig. 17 Relationship between rise-to-span ratio and main span.

Rise-to-span ratio f/l

g/p=

2.0g/p=5

.0

p:Live loadg:Dead load

0 0.60.50.3 0.40.20.1

Vol

ume

of st

eel

Fig. 18 Relationship between steel volume and rise-to-span ratio.

11.76%

67.65%

20.59%

Parabola Catenary Others

Fig. 19 Arch axes of steel arch bridges in China.

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main span of 138.3m. Two-hinged forms were adopted in the majority of deck and half-through steel arch bridges, and there are 286 two-hinged bridges in total. (3) Rise-to-span ratio

The rise-to-span ratio is an important parameter of steel arch bridges. The distribution of rise-to-span ratios used in existing steel arch bridges in China and Japan are illustrated in Fig. 16. It shows that the rise-to-span ratios of steel arch bridges in China are in the range of 1:2 to 1:8, mostly from 1:4 to 1:6, while the rise-to-span ratios of steel arch bridges in Japan are in the range of 1:9 to 1:3, commonly be-tween 1:7 and 1:5. Other ratios such as beyond 1:8-1:3 and 1:9-1:3 are usually employed in short-span bridges. The rise-to-span ratio of steel arch bridges in China is slightly greater than Japan’s.

In addition, as shown in Fig. 17, there is no direct correlation between the rise-to-span ratio and the main span of steel arch bridges in China and Japan.

For parabolic arches, the relationship between steel volume, f/l and g/p, where g and p are the dead load and the live load acting on the arch rib, and f/l is the rise-to-span ratio, has been derived by the varia-tion method in Reference 19), as given in Fig. 18. Fig. 18 shows that the most material–saving struc-ture is when the f/l varies in the range of 1/6-1/5. In addition, the ratio of g/p has a significant influence on the amount of steel used. The larger traffic vol-ume in China than in Japan possibly causes the larger rise-to-span ratios of steel arch bridges in China. But the rationality of rise-to-span ratios commonly used

in China and Japan still requires further study. (4) Arch axes

Since data about arch axes of steel arch bridges in Japan have not been collected, arch axes of steel arch bridges in China are analyzed in this section.

To maximize the compressive resistance of the arch rib, the arch axis is expected to be close to the compression line of the dead load. Among the se-lected 82 steel arch bridges, the arch axes of 34 bridges (excluded were peculiarly shaped bridges or those with unknown shape) are shown in Fig. 19. It can be seen from Fig. 19 that 23 (67.6%), 7 (20.6%) and 4 (11.8%) bridges adopt the parabola, catenary and other curves (such as ellipse, circle, combination of parabola and catenary), respectively. It is obvious that the parabola is the most popular arch axis in steel arch bridges because of the approximately uniform spanwise distribution of its dead loads.

(5) Section of arch rib

The sections of arch ribs can be classified into solid type and truss type. There are 76 bridges in China and 912 bridges in Japan with known section types. They are selected for analysis here, as shown in Table 6. In China, solid ribs are used in 57 (75.0%) bridges and truss ribs are used in the remaining 19 bridges (25.0%). In Japan, solid ribs and truss ribs are employed in 900 bridges (98.6%) and in 13 bridges (1.4%), respectively. Therefore, mainly solid ribs are adopted in steel arch bridges in China and Japan.

The solid rib is usually adopted in short steel arch

Table 6 Section of arch rib.

Type Shape Bridge in China Bridge in Japan

Number Percentage Number Percentage

Solid

Rectangle 53 69.7% 870 95.3% Circle 0 0.0% 29 3.2% Ellipse 2 2.7% 0 0.0%

Octagon 1 1.3% 0 0.0% L-shape 1 1.3% 0 0.0% I-shape 0 0.0% 1 0.1%

Truss Rectangle 19 25.0% 11 1.2% Circle 0 0.0% 2 0.2%

Table 7 Construction methods for steel arch bridges.

Construction method Steel arch bridge in China Steel arch bridge in Japan

Number Percentage (%) Number Percentage (%) Cantilever method 18 36.7 231 50

Scaffolding method 21 42.9 198 42.9 Swing method 3 6.1 1 0.2

Launching method 2 4.1 0 0 Large block method 5 10.2 32 6.9

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bridges, and its section can be I- or L-shaped, a cir-cular tube or box-shaped, etc. The I- or L-shaped sections are used in a few short-span steel arch bridges in some countries. In China, the L-shaped section is adopted in a very small steel arch bridge. In Japan, the I-shaped section is employed in Sa-kuranomiya Bridge. Circular tubes adopted as arch ribs are usually filled with concrete in China, while mainly hollow circular tubes are employed in Japan. The box shape is the main section of steel arch bridges in China and Japan. Meanwhile, for the sake of an elegant appearance, some unfamiliar box sec-tions such as octagon-shaped (the No. 1 Bridge crossing the Chanba River in Xian) and elliptical (the Yangtze River Bridge in Zhongsan and the Liuwu Bridge in Lasa) are occasionally used in China. For some long-span bridges, a single box section with double cells is used in China, such as in the Lupu Bridge in Shanghai (main span: 550m) and the Mingzhou Bridge in Ningbo (main span: 450m).

Truss ribs can be more effective and are preferred when the arch span exceeds 200m. Members in truss ribs are smaller and lighter than those in solid section ribs; therefore, they facilitate delivery and erection. However, truss ribs are more difficult to fabricate in

member connection and the complexity sometimes affects their beauty. Because steel arch bridges have larger stiffness than cable-stayed bridges and sus-pension bridges, many have been used as high-speed railway bridges, which need very rigid structures. The sections employed in solid ribs may also be used in truss members of steel arches, such as I- or H-shaped, circular tube and box sections. However, mostly box section members are used in China and Japan for their great stiffness and simple configura-tion in long-span steel arch bridges. Other section members are rarely used.

7. CONSTRUCTION METHOD Similar to RC and CFST arch bridges8), 9), the

scaffolding method, cantilever method and swing method are used for steel arch bridge construction. In addition, the lightweight quality and high stiffness of steel arch bridges enable the use of launching and large block methods for the whole superstructure or large segments of the structure. The known con-struction methods used in selected steel arch bridges are shown in Table 7.

Fig. 20 Construction of Dashengguan Bridge. Fig. 21 Construction of Dongping Bridge by swinging vertically.

Fig. 22 Construction of Dongping Bridge by swinging horizontally. Fig. 23 Construction of Xinguang Bridge.

Fig. 24 Construction of 2nd Ondo Bridge. Fig. 25 Construction of Xiangjiang Bridge.

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Table 7 shows that about 36.7% and 50.0% of the steel arch bridges in China and Japan, respectively, were constructed using the cantilever method. This method can be used in long-span bridges. Besides the cable-stayed cantilever method, which is also mostly used for RC and CFST arch bridges, the free canti-lever method can also be used in steel arch bridge construction. The cable-stayed cantilever method requires complicated temporary structures such as pylons, cables and anchoring, whose design and construction are sometimes much more challenging and difficult than the bridge itself. The free cantile-ver method is the favorable choice for a steel truss arch rib because the rib has a great stiffness and load-carrying capacity; therefore the need for auxil-iary structures is minimized. This method was adopted in the construction of the Dashengguan Bridge (high-speed railway bridge, spans: 108+192+336+336+192+108), completed in August 2009 in China. As shown in Fig. 20, each side arch was erected using the free cantilever method via a short pylon and a pair of cables. The two central arches were erected by horizontal cables in three levels anchored back-to-back to each other. The deck truss was installed synchronously with arch ribs.

Quite a number of steel arch bridges (accounting for 42.9% in both countries) are constructed using the scaffolding method in China and Japan. When the river is shallow with little navigation, the scaf-folding method is appropriate. This method is also used for bridges with a flexible arch and a rigid girder, in which the arch ribs are erected through scaffolds on the rigid girder previously constructed.

The swing method is specially used for arch bridges in China. Approximately 6.1% of steel arch bridges are constructed using this method, even for some bridges with a large span. As shown in Figs. 21 and 22, the Dongping Bridge in Foshan city, Guangzhou province, with a main span of 300m, was constructed by swinging vertically and horizontally. In Japan, the swing method was employed only in

0

100

200

300

400

500

600

Construction methodLaunchingSwingScaffoldingLarge block

ChinaJapan

Main

span

leng

th, m

Cantilever

Fig. 26 Relationship between construction method and main span length.

Fig. 27 Dagu Bridge in Tianjing.

Fig. 28 Jiubao Bridge in Hangzhou.

Fig. 29 Fenghua Bridge in Tianjing.

Fig. 30 New Nishigawara Bridge in Ibaraki.

Fig. 31 Forest Bridge in Aichi.

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Ogatayama Bridge in the Yamanashi Maglev Test Line.

The large block method is a method in which the whole superstructure or large segments of the structure are hoisted by a floating crane or winch. This method was seldom employed in China. It was used in the construction of the Xinguang Bridge in Guangzhou of China, shown in Fig. 23. The arch rib was hoisted and assembled from three large seg-ments. The heaviest one, weighing 3078t, was hoisted to 85.6m high by 16 synchronous hydraulic jacks. In Japan, the large block method employing a floating crane, such as in the 2nd Ondo Bridge shown in Fig. 24, was relatively common.

The launching method was used for the Jiubao Bridge in Hangzhou and the Xiangjiang Bridge in Changsha of China. The construction of Xiangjiang Bridge is shown in Fig. 25. This method has not been adopted in Japan.

The cantilever method and scaffolding method are the main construction methods. Of the selected steel arch bridges in China and Japan, 79.6% and 92.9% employed these methods, respectively. The rela-tionship between construction method and main span length is illustrated in Fig. 26. The cantilever method can be adopted not only for small bridges but also for large bridges. Other methods are usually employed for bridges with spans shorter than 250m. Owing to the lightweight quality and high stiffness of the steel arch rib, it is possible to develop better construction methods to promote technological progress in con-struction. 8. AESTHETICS

There is no doubt that the arch bridge is a beautiful, functional, and expressive structural form. The lightweight but strong characteristics of the steel arch coincide with the architect’s vision on structural forms; therefore, there has been a trend to pursue the aesthetic appearance of steel arch bridges in China in recent years. The main approaches are done by 1) adopting outer-inclined arch ribs, such as the Dagu Bridge, with a main span of 106m, shown in Fig. 27; 2) spatial composition of arch ribs of various scales, such as the Jiubao Bridge in Hangzhou, with a main span of 210m, shown in Fig. 28; 3) deformed arch axial line, such as the Fenghua Bridge in Tianjing, with a main span of 138m, shown in Fig. 29.

In Japan, a few girder bridges are stiffened by a single arch rib or a couple of arch ribs without bracing. A few irregular steel arch bridges are found in highway and railway systems, such as the New Nishigawara Bridge in Ibaraki, which is a combined

high-low arch bridge with a main span of 78.8m (see Fig. 30)20). With regard to pedestrian bridges, lots of forms have been designed, including tilting arches and butterfly arches. An example is the Forest Bridge in Kenkounomori Park in Aichi prefecture21) (see Fig. 31).

It can be seen that the irregular steel arch bridges were constructed in China with not only small but also larger main spans, while they were only em-ployed in small highway and pedestrian bridges in Japan. If the appearance and aesthetics of a bridge are presumably very important and the increased costs are limited and acceptable, various arches may be considered. But they should not be excessively used for long spans or for heavily loaded bridges, because the likely result would be very expensive but not exactly beautiful bridges. 9. LAST REMARKS

The results of a comprehensive survey of steel arch bridges in China and Japan with respect to history, steel material, design traffic load, design method against global buckling, main span, struc-tural form and construction method have been re-ported in this paper. Statistical comparison of steel arch bridges in China and in Japan has also been briefly addressed.

Steel arch bridges have a long history in Japan. The experience and technique of design and con-struction of steel arch bridges in Japan provide a good reference for engineers worldwide. Steel arch bridges have been used relatively late and still on a small scale today in China. However, rapid progress has been made in recent years. The development of steel arch bridges in China has improved steel arch bridge engineering technologies in the fields of de-sign, fabrication and erection for long-span bridges.

Steel arch bridges remain popular structure types that are frequently adopted for modern bridges, even though designers now have many other structural types to choose from. Many steel arch bridges will be built for their elegant appearance and favored by designers and owners for highway and city roads. At the same time, this bridge type is strongly competi-tive in long-span high-speed railway bridges with a high requirement for stiffness. Therefore, the steel arch bridge still has a prosperous future in this era of large-scale transportation infrastructure construction in developing counties. The survey of steel arch bridges in China and Japan in this paper is expected to provide base data and a reference for its future research and construction.

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(Received September 18, 2012)

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