Journal of JSCE, Vol. 2, 54-61, 2014 (Invited Paper)

THE ORIGIN OF TIMBER ARCH BRIDGES IN

Yan YANG1, Shozo NAKAMURA2, Baochun CHEN3 and Takafumi NISHIKAWA4

1Assistant researcher, College of Civil Eng., University of (2, Xueyuan Road, Minhou, Fuzhou 350108. China) E-mail: [email protected] 2Member of JSCE, Professor, Dept. of Civil and Environmental Eng., Nagasaki University (1-14, Bukyo-machi, Nagasaki 852-8521, Japan) E-mail: [email protected] 3Professor, College of Civil Eng., University of Fuzhou (2, Xueyuan Road, Minhou, Fuzhou 350108. China) E-mail: [email protected] 4Member of JSCE, Assistant Professor, Dept. of Civil and Environmental Eng., Nagasaki University (1-14, Bukyo-machi, Nagasaki 852-8521, Japan) E-mail: [email protected]

The main structure of timber arch bridges in China consists of two longitudinal polygonal arch systems made of straight logs. According to their present situation, location, and structural details, these timber arch bridges can be further divided into two types: one is exemplified by the non-extant ancient Bianhe rainbow bridge, and the other by the extant Min-zhe timber arch bridge. However, the historical origin of these two bridges is not clear and is still being argued. In this paper, the two types of timber arch bridges are struc- turally and historically analyzed and compared to determine which one is the pioneer from the techno- logical development viewpoint. Results of our research indicate that, compared with the Bianhe rainbow bridge, the Min-zhe timber arch bridge has better traffic performance and can provide additional service performance. The spandrel structure, X-bracings as well as inserted wood blocks among logs in the Min-zhe timber arch bridge play important parts in carrying loads and enhancing the integrity and stability of its main structure, while the covering house adds dead load to the main structure to improve its resisting capacity against uplift loads. Therefore, from a reasonable consideration of technological development, the authors support the opinion that the Bianhe rainbow bridge is the origin of the Chinese timber arch bridges.

Key Words: Chinese timber arch bridges, origin, Bianhe rainbow bridge, Min-zhe timber arch bridge, structure technology development

1. INTRODUCTION called the ancient Bianhe rainbow bridge; ‘Bianhe’ is the transliteration of Bian River. This kind of bridge The Chinese timber arch bridge is a woven arch can now be seen only in the famous painting of bridge; its main structures are two longitudinal po- Chhing-Ming Shang Ho Thu shown in Fig.1 (a)1). lygonal arch systems consisting of straight logs. It More than one hundred Min-zhe timber arch can be further classified into two branches, one is the bridges, typified by the Guangli Bridge as shown in non-extant ancient Bianhe rainbow Bridge, and the Fig.1 (b), are still extant in mountainous areas other is the extant Min-zhe timber arch bridge1). northeast of Province and southeast of According to historical records, the first Chinese Province. Since the short names of Fujian timber arch bridge was built from 1032 to 1033; Province and Zhejiang Province are “Min” and many such timber arch bridges had been built in “Zhe” respectively, they are called Min-zhe timber several places over the Fen and Bian Rivers in North arch bridges1), 3). China after that. The local people greatly benefited Both of these two kinds of timber arch bridges from these bridges. These bridges were sometimes could achieve large spans by weaving longitudinal called “No Foot Bridge,” “Fly Bridge,” or “Rainbow and transverse straight logs in a special way, alt- Bridge” in many masterpieces of the Song Dynasty hough their structural types are somewhat different. (960~1279)2). In this paper, this kind of bridge is The historical relationship between these two bridges

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(a) Bianhe rainbow bridge (b) Min-zhe timber arch bridge Fig.1 Two types of Chinese timber arch bridges. concerning their origin is not clear and is still being Min-zhe timber arch bridge. The former had been argued. Insufficient historical records and frequent built in the Song Dynasty, while archaeological repair/rebuilding make archeological investigations discovery found no evidences to prove that the difficult, and there has been no consensus on the Min-zhe timber arch bridge had existed before the origin of the Chinese timber arch bridges. In this South Song Dynasty (1126 - 1279) 9). paper, three opinions on the origin of the Chinese 2) Most families with strong backgrounds in tra- timber arch bridges are introduced and evaluated ditional construction technologies come from the from the structural and technological points of view. north of China. Therefore, the timber bridge tech- This paper aims to discuss the origin of the Chinese nology must have spread from north to south through timber arch bridges. these families9). 3) The cradle of the Bianhe rainbow bridge was in the capital of China in the Song Dynasty, which had 2. BRIEF REVIEW OF LITERATURE better economy and advanced technology. At the same time, the Fujian and Zhejiang provinces were There are three different opinions on the origin of major areas in the Song Dynasty, planting and pro- the Chinese timber arch bridges. One considers the ducing tea for the imperial group. The economy, Bianhe rainbow bridge as the original; the other technology, and information exchanges were rela- maintains that the Min-Zhe timber arch bridge is the tively frequent between the north of China and Fujian original one, while the third opinion states that the and Zhejiang provinces at the south of China in those two branches developed independently. days. Therefore, it was possible that merchants and craftsmen spread advanced technology from the 9) (1) Opinion A: Bianhe rainbow bridge is the capital to other places . original In the History of Technique of Archaian Bridges in (2) Opinion B: Min-zhe timber arch bridge is the 4) original China published in 1986, the author conjectured 10)~13) that the Chinese timber arch bridge originated from Some other researchers conjectured that the the Bianhe rainbow bridge, and the extant Min-zhe Chinese timber arch bridges originated from the timber arch bridge was introduced after the ancient Min-zhe timber arch bridge based on the following Bianhe rainbow bridge when the capital of the investigations: Northern Song Dynasty moved from Dongjing to 1) A piece of tile made in the Tang Dynasty (618 - Lin’an (now , Zhejiang Province) in the 907) was found on the roof of a covering house in one South Song Dynasty to start a new period. The dif- of the extant Min-zhe bridges, the Santiao Bridge ferences between the Min-zhe timber arch bridge and located in of Zhejiang Province. the Bianhe rainbow bridge stemmed from differences From this fact, some researchers inferred that the in local geographical conditions and characteristics Santiao Bridge had been built in the Tang Dynasty (618 - 907 AD), much earlier than the time the first of architecture. The Min-zhe timber arch bridge is a 10) combination of the Bianhe rainbow bridge and local Bianhe rainbow bridge was built . wooden craftsmanship4). 2) Historical records and field surveys show that a This conjecture has been accepted by many re- series of wooden construction bridges had been built searchers5)~9). In addition, experts and scholars in Fujian and Zhejiang Province. These bridges in- brought forth further arguments as follows: clude simple beam bridges, timber beam bridges with 1) Many historical records have shown that the columns, timber beam bridges with inclined braces, Bianhe rainbow bridge appeared earlier than the secondary beam-braced timber bridges, timber bridges with combined braces, and woven timber

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Table 1 A series of timber bridges in Fujian and Zhejiang provinces. No. Type Simplified plane schemes Bridge name, location Photo 1 Simple beam Hua Bridge, bridge Pingnan county of Fujian province

2 Timber beam Guangtong Bridge, bridge with Pingnan county of column Fujian province

3 Timber beam Jichuan Bridge, bridge with Pingnan county of inclined braces Fujian province

4 Secondary Shengxian Bridge, beam braced Shouning county of timber bridge Fujian province

5 Timber bridge Meishuban Bridge, with combined of braces Zhejiang Province

6 Double Xingrong Bridge, secondary Shuncang county of beam braced Fujian province timber bridge

7 Min-zhe timber Yingfeng Bridge, arch bridge Pingnan county of Fujian province

arch bridges shown in Table 1, forming a complete chains of woven timber arch bridges, and may indi- construction development system in timber structural cate that the Min-zhe timber arch bridge must have bridges10)~13). Theses bridge types consists of whole developed solely from local timber bridges.

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60 830 (3) Opinion C: The two kinds of timber arch 60 bridges developed independently

The third opinion is that the two types of bridges 30 30 9), 14) 30 40 perhaps originated and developed independently . 21×45＝945 Researchers supporting this opinion consider that there were no technology exchanges and communi- cation between the builders due to inconvenience in The first system The second system transportation and communication as well as long Fig.2 Sketch of Bianhe rainbow bridge. and frequent wars. In addition, there are no historical records due to the wars. The other reason is that these

Coveringthe coveredhouse house two kinds of bridges differ in appearance and in Covered house structural forms. Transverse beamthe transverse of 2ndbeam of thesystem second system Transverse beamthe transverse of 1st beam ofsystem the first system Spandrelthe spandrel structure structure (horse-leg) (horse-leg) the longitudinal beam 3. ANALYSIS OF THE ORIGIN OF THE Longitudinal beam the rails Spandrel protection plates CHINESE TIMBER ARCH BRIDGES X-bracingthe X-bracing FROM THE TECHNOLOGICAL Transversethe transverse beam of the beam second system of 2nd system DEVELOPMENT VIEWPOINT 2ndthe second system system of the arch of ring arch ring the frist system of the arch ring 1st system of arch ring (1) Description of Bianhe rainbow bridge and Min-zhe timber arch bridge Fig.3 Sketch of Min-zhe timber arch bridge1). A sketch of the ancient Bianhe rainbow bridge 15), 16) structure is shown in Fig.2 based on Fig.1 (a), which lows: has 21 groups of log arch frameworks arranged in a 1) Both have an arch structure made by weaving parallel pattern. One system consists of three arch longitudinal and transverse straight logs in a special frameworks of the same length with 10 groups, and way. Two longitudinal polygonal arch systems con- the other system is composed of two long arch sisting of straight logs are connected to the transverse frameworks and two short ones with 11 groups. The beams. The first system is a three-line polygonal arch two systems are tiered and interwoven by transverse rib with three longitudinal straight logs of the same timber members to form intersection points at the length and two transverse beams. timber frame. The longitudinal members are com- 2) Both successfully utilize the short construction pression dominant; five logs are laid to traverse the element to achieve a large span. All the members are whole bridge, connecting the arch frameworks, sta- straight. This makes processing the members easier. bilizing the structure and distributing the live load in 3) Their longitudinal members are mainly sub- the transverse direction. jected to compressive forces and take full advantage A typical structure of a Min-zhe timber arch bridge of compressive strength of timbers parallel to their is illustrated in Fig.31). It consists of abutments, arch fiber. The transverse members contribute to an im- ring, spandrel structure, deck system, covering provement of the load bearing capacity by integrating house, etc. the whole structural system. The main arch ring of the Min-zhe timber arch Meanwhile, there are differences in their structural bridge is similar to that of the ancient Bianhe rainbow details, which result in different bridge functions and bridge. Its bearing structure also consists of two structural behaviors. They could be clues to identi- longitudinal polygonal arch systems by weaving fying technology development routes. straight logs. The two systems with different po- a) Spandrel structure lygonal sides are interlaced to a single structure, The extant Min-zhe timber arch bridge has span- resulting in making the longitudinal members re- drel structures and floor systems, making it easy for sistant to compressive forces. Its transverse beams passengers and carriages to pass through, while the play a part in connecting arch frameworks, stabiliz- ancient Bianhe rainbow bridge does not have them; ing the structure and distributing the live load in the this arch-shaped structure with extrados, has steps for transverse direction. pedestrians, instead. For the main structure, the Bianhe rainbow bridge (2) Comparison of structure and behavior of the consists of three members in the first system and four Bianhe rainbow bridge and the Min-zhe tim- members in the second systems connected by five ber arch bridge transverse beams as illustrated in Fig.2 and Fig.4 (a). The Bianhe rainbow bridge and the Min-zhe tim- The first system of the typical Min-zhe timber arch ber arch bridge have similarities in structure as fol- bridge also has three members, while the second

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4(4') 3 3' 6 2 7 7' 2'

8 8' 1 1' (a) Bianhe rainbow bridge 2.46 3.20 3.59

18.5

Fig.5 Simplified plane calculation model of Bianhe rainbow bridge (Units: m).

(b) Min-zhe timber arch bridge Fig.4 Main structures of Chinese timber arch bridges. Simplified calculations of the ancient Bianhe rainbow bridge and the Min-zhe timber arch bridge 7), 16) system has five members with six transverse beams, had been carried out by some researchers . In the 7) as illustrated in Fig.4 (b). China Timber Arch Bridge published in 2010, the In the Min-zhe timber arch bridge, the spandrel Bianhe rainbow bridge with a span of 18.5m was structures and the longitudinal beams of the floor analyzed both with and without a covering house. A system take part in carrying loads and enhancing the simplified in-plane model shown in Fig.5 was used integrity of the arch structure17). for the analysis. For the model with covering house, Therefore, it can be said that the Min-zhe timber the self-weight of the covering house is simplified as arch bridge is better in traffic function and more the concentrated force at each point in the longitu- reasonable in structure than the ancient Bianhe dinal direction on average. The results of the simple rainbow bridge. calculations are shown in Table 2. Comparing the b) Covering house results, the maximum axial forces in the timber arch All the Min-zhe timber arch bridges are covered by ribs of Bianhe rainbow bridges with and without various houses, while the Bianhe rainbow bridge has covering house are 54.44kN and 27.61kN, respec- no covering houses. In terms of function, the cover- tively; but the bending moment are 16.19kN･m and ing house protects its arch structure from heavy 28.44kN･m, respectively. Although the axial force in rainwater in the southeast mountain area, giving a the arch ribs of the bridge with covering house is more reasonable design than the Bianhe rainbow almost two times as large as that of the bridge without bridge, and makes it possible for many Min-zhe covering house, the bending moment decreases by timber arch bridges to survive until today. At the 40%. Further analysis shows that the stress in the same time, the covering houses also serve as a resting arch ribs decreases in the whole structure. In general, place for travelers through the mountainous path, and the diameter of arch ribs with covering house is also serves as a public place for talking, trading, and smaller than that of the bridge without covering religion activities, and even as a shrine for idols house in the same structure7). This fact implies that where villagers offer sacrifices. Thus, the bridge not the covering house is beneficial for the performance only has a transportation function but also provides of timber arch bridges against in-plane loadings. comprehensive uses for the local people’s daily liv- The covering house increases the drag force ing. Covering houses also show different architec- against wind. However, all the Min-zhe timber arch tures. Their ceiling structures are quite varied, espe- bridges are located in mountainous areas where ty- cially near shrines and altars, where elaborately phoons are uncommon and the wind is generally not carved and painted coffered domes are common. very strong. Consequently, no bridges destroyed by There are many beautiful paintings and calligraphy wind have been discovered or recorded in history. on the walls, pillars and roofs, like the churches with Although the covering house is beneficial for many luxuriant frescoes in the west. bridges as described above, only few footbridges in From the function of structure, the timber arch city business centers or parks are covered because bridge is light in self-weight and joint connections most of these footbridges are built by concrete and/or are weak in tension, therefore enough attention steel, which are not necessary for a covering house should be paid to not only downward dead and live from a structural point of view. For road or rail loads of the structures but also to the uplift loads from bridges, covering houses can interfere with the traf- flood torrents. The covering house in the Min-zhe fic. Furthermore, the importance of covering houses timber arch bridge could increase its self-weight that has been waning even in remote villages. Therefore, is beneficial for resisting the uplift forces. covered bridges are not very common these days.

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Table 2 Internal force calculation results.

N1-3(kN) N3-3(kN) N1-2(kN) N2-4(kN) M8(kNm) M6(kNm) M7(kNm) With covering 54.44 44.68 54.02 45.04 16.19 -14.07 13.45 house (1) Without covering 27.61 22.82 27.47 23.02 28.44 23.78 23.03 house (2) ((1)－(2))/(2) 0.97 0.96 0.97 0.96 -0.43 - -0.42

Fig.6 Binding node of Bianhe rainbow bridge.

Longitudinal member

Straight tenon

Transverse beam

Swallow Tail tenon

Longitudinal member

Fig. 7 Mortise and tenon joints in the Min-zhe timber arch bridge. c) Methods for connecting joints erection and the joint has better performance for In the ancient Bianhe rainbow bridge, members of sustainability than the lashing joint as in the Bianhe main arches were tied by ropes, and the transverse rainbow bridge. beams were joist members. The binding nodes of d) X-bracings some timber arch bridges modeled in the ancient In the Min-zhe timber arch bridge, the floor system Bianhe rainbow bridges in those years are shown in over the main arch provides a space for X-bracings to Fig. 61). improve the main arch’s transverse stability. In gen- In the Min-zhe timber arch bridge, the longitudinal eral, a long span timber arch bridge has two groups of logs are oined together through the transverse beams X-bracings, as shown in Fig.8 (a) and Fig.8 (b), by mortise and tenon joints. Two kinds of mortise while a short one has only one group of X-bracing, as and tenon joints have been used in the Min-zhe shown in Fig.8 (c). No such X-bracing has been found timber arch bridge. One is the swallow tail tenon in the Bianhe rainbow bridge. joint, which has a variable cross-section in the tenon Besides, wooden blocks are inserted among the log head as shown in Fig.7, and can bear some tension members to enhance the integrity of the structure as forces; the other is the straight tenon joint shown in shown in Fig.9. These structural details are also not Fig.7, which has a constant cross-section in the tenon found in the Bianhe rainbow bridge. head and sometimes with a step shape. The straight tenon joint cannot bear tension forces. In general, slant arch ribs are connected to the transverses beam 4. DISCUSSION ON THE ORIGIN OF by straight tenons since the arch ribs and the trans- CHINESE TIMBER ARCH BRIDGES verse beams are not easily separated by gravity, as shown in Fig.7. For construction facilitation, the (1) Discussion on opinion A: Bianhe rainbow second groups of slant arch ribs of the second system bridge is the original are connected to the transverse beams by swallow tail From the comparison of the two types of the tenons, as shown in Fig.7. Chinese timber arch bridges, it can be found that the This connection method is more convenient for Min-zhe timber arch bridge with floor system and

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(a) One side of two groups of X-bracings (b) Other side of two groups of X-bracings (c) One group of X-bracings Fig.8 X-bracings in the Min-zhe timber arch bridge.

Fig.9 Blocks of main arch in the Min-zhe timber arch bridge. covering house is more functional than the Bianhe raised as follows: rainbow bridge. The road slope of the bridge deck of This opinion mainly stands on a piece of tile made the Min-zhe timber arch bridge is small and easy for in the Tang Dynasty found in Santiao Bridge. Except passengers and carriages to pass through; the cover- for a member or a piece of tile, no other proof and ing house can provide relaxing and public space for available historical record, such as folk story or passengers and villagers. In the structural details, the bridge stone tablet record, can show that one of the spandrel structure, the X-bracings, as well as the Min-zhe timber arch bridges was built earlier than the inserted wood blocks among the logs in the Min-zhe Bianhe rainbow bridge. The evidence is inconclu- timber arch bridge take part in carrying loads and sive, as we all know that timber structures need fre- enhancing the integrity and stability of the arch quent maintenance, repair, and rebuilding. In those structure. The covering house can add dead load to times, it was customary to use not only the original the structure to improve the structure’s resisting ca- members of the building but also members from pacity to the uplift load. Therefore, it can be con- other buildings. Thus it is possible that the tile made cluded that the Min-zhe timber arch bridge is better in Tang Dynasty was obtained from other buildings. in traffic function and more reasonable in structure The complete system of timber bridges listed in than the ancient Bianhe rainbow bridge. Table 1 is the other main argument for opinion B. From a reasonable consideration of technological However, there is no sound evidence to show that the development, an advanced bridge structure generally series of the bridge structures developed in that order. evolves from experiences with a primitive one. In this From the present investigation, we found few pieces sense, it is more reasonable to consider that the of evidence that the development sequence of the Min-zhe timber arch bridge developed from the series bridge structures does not agree with the Bianhe rainbow bridge. opinion. For example, according to opinion B, the Furthermore, the reasons for opinion A presented double three-member timber arch bridge as shown in in Section 2(1) seem more reasonable from the his- the sixth row of Table 1, should be built earlier than toric background and general knowledge than those most of the Ming-zhe timber arch bridges, which for opinions B and C in Sections 2(2) and 2(3), which have three members in the first system and five will be discussed in the following sections. members in the second system as shown in the sev- Consequently, the authors suggest that this opin- enth row of Table 1. However, the field survey by ion, that is, that the Bianhe rainbow bridge is the the authors18) reveals that there are only six bridges original bridge, could be the prevailing statement, with the double three members in service and they unless new and further research results prove other- were all built after 1800 (Qing Dynasty wise. (1644-1911)), while there are 128 Min-zhe timber arch bridges in service and about half of them were (2) On opinion B: The Min-zhe timber arch built before 1800. Therefore, we maintain that the bridge is the original origin of these double three-member timber arch As for opinion B, which asserts that the Min-zhe bridges should be later than Min-zhe timber arch timber arch bridge is the original, some doubts are bridges, and this type of bridge is a simplified

60 structure of the general Min-zhe timber arch bridge. for the science and technology development fund, Even though the development shown in Table 1 is and to the education department of Fujian Province in correct, the authors think that the table cannot sup- China for providing the necessary funds for this re- port the opinion since the relationship between the search work. Bianhe rainbow bridge and Min-zhe timber arch bridge is still unclear. REFERENCES 1) Yang, Y., Nakamura, S., Chen, B. and Nishikawa, T.: Tra- (3) On opinion C: The two branches of timber ditional construction technology of China timber arch bridges, Journal of Structural Engineering, Vol. 58A, pp. arch bridges developed independently 777-784, 2012. The third opinion is a compromise between the 2) Tang, H.: Chinese Ancient Bridges, Beijing: Cultural Relics other two opinions. It is possible for ancient bridges Press. Beijing, China, 1957 (in Chinese). to evolve similarly but independently in various 3) Yang, Y., Chen, B. and Gao, J.: Timber Arch Bridges in China, Proceedings of the Fifth International Conference continents of the world. However, it is quite difficult on Arch Bridge, Madeira, Portugal, pp. 171-178, 2007. to imagine that the two types of the Chinese timber 4) Mao, Y.: History of Technique of Archaian Bridges in arch bridge have evolved independently with so China, Beijing Press. Beijing, China, 1986 (in Chinese). unique but similar structures, in two regions close to 5) Tang, H.: Chinese Ancient Bridges (the second edition), each other in a nation. Cultural Relics Press. Beijing, China, 1987 (in Chinese). 6) Tang, H.: History of Science Technology in China, Bridge Volume. Science Press. Beijing, China, 2000 (in Chinese). 7) Tang, H.: China Timber Arch Bridges, Beijing: Cultural 5. CONCLUSIONS Relics Press. Beijing, China, 2010 (in Chinese). 8) Tang, H.: Chinese Ancient Bridges (the third edition), China Building Industry Press, Beijing: China, 2011 (in Chinese). The timber arch bridge is one of the important 9) The Culture and Publication Board of city edit.: structural forms in the Chinese history of ancient Archaeological investigation on rainbow-beam type timber bridge construction. It is the essence of architecture covered house bridge in Ningde city of Fujian province, in China and part of the precious cultural heritage Science Press, Beijing, China, July, 2007 (in Chinese). handed down from the ancient people. However, 10) Liu, J. and Shen, W.: Lounge Bridges in Taishun. Shanghai People’s Fine Arts Press, Shanghai, China, 2005 (in Chi- insufficient historical records and frequent repairs nese). and rebuilding make archeological investigations 11) Chen, Y.: Analysis on the structure and origination of difficult. The historical development of the bridge is Min-zhe timber arch bridge, Southeast Culture, Vol. 9, No. not clear and is still being argued. 173, pp. 66-71, 2003 (in Chinese). In this paper, the Bianhe rainbow bridge and the 12) Cao, C.: Structure and origin of Min-zhe timber arch bridge, Proceedings of the Third China International Symposium Min-zhe timber arch bridge were compared in terms on the Roofed Bridges of Wooden Arch Structure in of bridge service function and structural details as Pingnan County, Pingnan, China, pp. 88-96, 2009 (in well as their behaviors with the aim to discuss the Chinese). origin of the Chinese timber arch bridges. The anal- 13) Bi, S. and Zhao, C.: Research on typology of Min-zhe timber arch bridge, Proceedings of the Third China Inter- ysis results show that the Min-zhe timber arch bridge national Symposium on the Roofed Bridges of Wooden Arch has better traffic performance than the Bianhe rain- Structure in Pingnan County, Pingnan, China, pp. 80-87, bow bridge. The covering house of the Min-zhe 2009 (in Chinese). timber arch bridge can additionally serve as a public 14) Fang, Y.: Research on the Min-zhe rainbow bridge, Archi- space where passengers and villagers can relax. The tecture of Fujian, Vol. 46, pp. 7-10, 1995. 15) Ceraldi, C. and Ermolli, E. R.: Timber Arch Bridges: a spandrel structures, X-bracings, as well as the in- Design by Leonardo, Proceedings of Arch Bridges serted wood blocks among the logs in the Min-zhe IV—Advances in Assessment Structural Design and Con- timber arch bridge take part in carrying loads and struction, Barcelona, Spain, pp. 69-78, 2004. enhancing the integrity and stability of the arch 16) Yang, Y., Chen, B. and Liu, J.: Demonstration research of structure. The covering house adds a dead load to the arch structure for Min-zhe timber arch bridge, Proceedings of the fourth China International Symposium on the Roofed structure to improve the structure’s resisting capacity Bridges of Wooden Arch Structure in Qingyuan County, to the uplift load. Qingyuan, China, pp. 71-76, 2011 (in Chinese). Therefore, based on a reasonable consideration of 17) Liu, J.: Research on Structural Behavior of timber arch technological development, the authors take the bridges in Fujian and Zhejiang, Master's degree thesis, Fuzhou University, China, 2011 (in Chinese). more reasonable conclusion that the Min-zhe timber 18) Yang, Y., Nakamura, S., Chen, B. and Nishikawa, T.: A arch bridge developed from the Bianhe rainbow survey on existing China timber arch bridges, Journal of bridge. In other words, we support opinion A unless Civil Structure and Material, Vol. 28, pp. 61-68, 2012. new and further research results can prove otherwise. (Received December 7, 2012) ACKNOWLEDGMENT: The authors would like to express their sincere gratitude to Fuzhou University

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