The Recent Improvement of High-Speed Railway Bridges in China

Transcription

1 The Recent Improvement of High-Speed Railway Bridges in China Gonglian DAI Professor, Central South University, Changsha, China Gonglian DAI, born 1964, received his engineering PhD degree from Central South University in 1997 and joined department of bridge engineering from Now, he is the dean of department of bridge engineering in Central South University. The design theory and load-capacity for bridge structures is the focus of his research. Nan HU Graduate Student, Central South University, Changsha, China Nan Hu, born 1985, received his bachelor degree of engineering degree from Hunan University in He is now working at department of bridge engineering of Central South University as a graduate student. Wenshuo LIU Ph.D Student Central South University Changsha, Hunan, China [email protected] Wenshuo Liu, born in 1985, received her bachelor degree of engineering from Central South University in She is now studying at the department of bridge engineering of Central South University as a Ph.D student. Summary Based on the study of Wuhan-Guangzhou passenger Line and Beijing-Shanghai Passenger line, in this paper, the technical feature and new improvement of high-speed railway (HSR) bridges in China has been introduced from following aspects: First, two major design code (Temporary Provision for Passenger Railway Line of Km/h and Km/h) has been compared, under the current HSR bridge design specifications on the issue of main contents and technical indexes. Second, based on real projects, the technical characteristic of standard span prestressed concrete girder bridge for high-speed railway has been summarized, including layout of span, section types. Meanwhile, both ballast and non-ballast bridge has been studied on technical feature and material consumption. Third, this paper summarized substructures and foundation, and discussed the standardization of continuous beam bridge and construction diversity. Finally, the technical feature of several four-lane large bridges in high-speed railway lines has been introduced, including Tianxingzhou Bridge in Wuhan, Dashengguan Bridge in Nanjing, etc. In spite of this improvement, there are still numerous problems and challenge during designing of high-speed railway bridge. By reviewing and further research, a better solution will be found and applied in future projects. Keywords: high-speed railway; simply supported beam bridge; substructure; continuous beam, large span high-speed railway bridges; standardized design. 1. The development of high-speed railway in China Fig. 1: the operated mileages of HSR in the Fig. 2: the ratio of bridges mileage among all world(by the end of 2009) the mileage at a number of lines in China Qin-Shen Passenger Line, from Qinhuangdao to Shenyang, 200km/h, is the first two-line electrified

2 express railway, which designed and constructed by China. This line built and put into operation in 2003, was a symbol for the beginning of high-speed railway (HSR) in China. Beijing-Tianjin line with km, put into operation in August 2008, is first inter-city HSR with speed above 300 km/h and first HSR passenger line. Wuhan-Guangzhou HSR passenger line, opened at December 26, 2009, with length of 968 km, operating speed of 350 km and the maximum speed of 380 km, is currently the longest mileage, highest technical standards, fastest passenger line in China. Moreover, its 394 km/h in trial run was a milestone for HSR construction in China. After development of last decade, the HSR in China has already had longest mileages in the world, as shown in figure 1. Because of superior on speed, comfort and its continuous operating density, the requirements of civil structures for HSR are extremely strict. Compared only 20% proportion of bridges among total mileages in traditional railway, HSR bridges covered the majority length of passenger line project. At present, bridges covered nearly 50% of the total mileages in Chinese HSR lines. For instance, Beijing-Tianjin inter-city HSR reached up to 88%. The ratio of bridges mileage among all the mileage at a number of lines in China is shown in Figure 2. Therefore, in plain and dense population areas, bridges with medium or small span are usually adopted. China has fully learned technology and experience in the world, and gradually formed a system of standardized bridge design and construction. This paper will review the new development of HSR in China in recent years, including improvement of design codes, the standardized design, fabrication and erection, the standardization of substructure and the development of large-span multi-line bridges in China. 2. Current code for HSR line and bridge From 1990s, China has carried out the research on HSR technology on the basis of experience from other counties. By summing up practice in Qin-Shen passenger line, Chinese railway technology is gradually formed as follows: speed for combined passenger and freight railway is 200 km/h; HSR speed divided in two grades: 200~250 km/h and 300~350 km/h. Based on "Temporary Regulations on Beijing-Shanghai high-speed railway design" and experience in recent years," Temporary Provision for Passenger and Freight Railway Line of 200km/h", "Temporary Provision for Passenger Railway Line of Km/h " (TP ) and " Temporary Provision for Passenger Railway Line of km/h" (TP ) has been drawn up. The first one focused on traditional railway, the latter two on modes of Chinese HSR passenger-freight and passenger dedicated line, the technical indexes are shown in Table 1. The high demand on smooth of HSR is controlled by two temporary codes, while the structural design is still carried out as traditional railway bridge. As can be seen from a series of limits below, displacement control in HSR bridge design is to ensure the stability of the train and comfort of passenger. As for increased speed, the requirements of stiffness on structures are also increased (TP has a higher requirements). Table 1: the major contents and difference in TP and TP Ser Item 200~250km/h 300~350km/h Description for contents 1 design life 100 years 2 minimum plane circular curve radius 2200(4000) 4500(7000) 200(250); 300(350) km/h 3 minimum vertical curve radius 15000(20000) The same as above 4 line space 4.4(4.6) 4.8(5.0) The same as above 5 design live load model ZK Live Load (0.8UIC) 6 vertical rotatory angle of beam end 2 ( 1 ) With-ballast(non-ballast) 7 horizontal rotatory angle of beam 1 8 transverse deformation of beam L/ torsion of beam (rail vertical relative ZK static live load (static 1.5mm 1.5mm(1.2) displacement) actual operating trains) 10 deck vertical acceleration 0.35g(0.5g) f 20Hz, ballast (non-ballast) 11 vertical free vibration frequency of simply supported beam 80/L(L 20m) 120/L( 40m) 12 difference of abutment post-construction 50mm 30mm(20mm) ballast (non-ballast)

3 settlement 13 uneven settlement of adjacent abutment 20mm 15mm(5mm) ballast (non-ballast) 14 creeping after track laying 20mm(10mm) ballast (non-ballast) 2.1 Live Load Mode for HSR bridge design Live load mode is one of the most important factors for HSR bridge design. At present, different countries use different modes, for example, UIC mode in Europe vs N-P mode in Japen. The chose on mode not only control the bridge deformation but the security and economic index. Considering UIC and N-P mode and special feature in of CRH train, ZK live load has been chosen in China, about 0.8 times value of UIC mode, as shown in figure 3: Fig 3: ZK standard live load and special live load 2.2 Deformation Control To meet a high demand on smooth, deformation on girder need to be strictly restricted, as shown in Table 2. Beam vertical rotatory angle should not be greater than the following limits: ballast trackθ =2.0x10-3rad,θ1+θ2=4x10-3 rad; Non-ballast track:θ=1.0x10-3 rad,θ 1 +θ 2 =2x10-3 rad. Table 2: Beam vertical rotatory angle limits Span L<24m 24m<L<80m L>80m Single-span L/1300 L/1000 L/1000 Multi-span L/1800 L/1500 L/1000 Figure 4: rotatory angle at beam end and beam deformation In order to ensure train safety, China has referred the standards in Germany. Therefore, TP set the limits of bridge torsional deformation: For a 3m-long rail, relative vertical deformation of two rails of one line should not be greater than 1.5mm under the ZK live load, and not be greater than 1.2mm under the action of actual trains. Although TP controlled horizontal and vertical displacement at the top of pier, there are not specific limits but refer to the limits in traditional railway. In TP , the interaction between beam and track has been taken into account. For example, simply supported bridge with main span of 24m, the min longitudinal stiffness of pier should be larger than 300kN/cm (abutment larger than kn/cm), or flexible adjuster for track should be set. 3. Standard simply supported bridge 3.1 The standardization of bridge span layout and design parameters Among Wuhan-Guangzhou HSR line and Beijing-Shanghai HSR line, the longest bridge had a length of 164km. 32m simply supported beam is frequently used as standard span and 24m or 40m simply beam mainly as adjusted span. At present, HSR in China generally adopted two-lanes and bridge is divided into pre-tensioned and post-tensioned beam, using the same beam section to simplify the framework. Considering specific circumstances, erection method can be in precast or

4 cast-in-place way. The precast post-tensioned simply supported beam is the most commonly used in HSR. Take the Wuhan-Guangzhou line as example, the rate simply supported beam reached about 95%, the two lanes 32m-span simply supported beam is the dominant type and 24m-span as the adjusted span. The major design parameters of several standard simple bridge are shown in table 4. Table 4: major design parameter of several most frequently used standard simple bridge Bridge Type Len gth Spa n Beam depth Wid th at top Width at bottom Beari ng spacin g vertical stiffness strand (straight/c urve) (t) steel( nonbarrier/ withbarrier)(t) 1 250km/h, precast, 24m / / / / / line spacing 4.6m 32m / / / / / km/h,in-place, 24m / / / Line spacing 4.6m 32m / / / km/h, precast, 24m / line spacing 5.0m 32m / km/h, in-place, 24m / line spacing 5.0m 32m / * 2.8/3.0 and 5.74/ 5.68 is at the middle span/ on the pier) Such bridge type had two advantages over others: the first is that box-section has larger stiffness and superb performance; the second is the erected beam can be used as the transport means, which can speed up erection of precast girder. For different sites, the different types of standard simply supported beams have been compiled into general drawings, such as ballast track and unballasted track, single lane girder or double lanes girder. 3.2 The optimization of the deck layout Figure 9: the layout in unballasted deck (before optimization in the left, after in the right) The HSR bridge deck layout not only considered enough security avoidance space, but the layout of the signal and communication facilities, because bridge width is an important economic indicators. In HSR in China, ballast track box girder has been adopted for 250km/h with line spacing of 4.6m, while unballasted track box girder has been adopted for 350km/h with line spacing of 5.0m. Referring the experience of Qin-Shen HSR, both bridge width in Wuhan-Guangzhou line and Beijing-Tianjin line is 13.4m, shown in figure 9 (at left). In order to reduce the weight, we further optimized deck layout in 2008, so that 250km/h unballasted track bridge is 11.6m, and the ballast track bridge deck is 12.2m. Also, 350km unballasted track bridge deck width changed from 13.4m to 12m, and the ballast track from 13.4m to 12.6m. Both Beijing-Shanghai line and Shijiazhuang- Wuhan line had selected this optimized section, saving numerous budge. For the erection between two tunnels, part of cantilever plate in the standard beam would be poured later as transportation of the beam is restricted by the limited space. Those left parts of cantilever plate would be poured

5 when box girder erected at the right place. The structure type of the bridge deck track also conducted a series of research and testing, gradually forming CRTS series plate unballasted track and double block unballasted track for the construction in China. 3.3 The standardized construction method for frequently-used bridge Due to 95% standard span in HSR line, the precast and span by span erection is very suitable for bridge construction in facing of short schedule. About 20km spacing, there is a plant for fabrication of girder. When the foundation is under construction, the beams was fabricating in the factory. The standardization process is good for quality and speed. 900t capacity machine and vehicle is used for transportation and erection of 32m girder. For the low span, cast-in-place method would be selected through moveable frame. The standardized method assures the speed of HSR construction. 4. The standardization and the diverse construction of the continuous beam Apart from simply supported beam as standard span, the continuous beam in HSR gradually were standardized: in the small span, same beam depth was adopted with main span of 2 24m, 3 24m, 2 32m, 3 32m, 2 40m; in medium span, variable cross-section has been adopted with the series main span of 40m, 56m, 64m, 72m, 80m, 100m, shown in table 5. For the bridge which main span is longer than 100m, is needed to be design distinctively. As a common bridge type across barriers, construction technology of continuous beam is very mature and standardized, while construction method leads to diverse way, such as cast-in-place, cantilever, launching, swing method, etc. Castin-place and cantilever are major construction method for HSR continuous beam bridge with low and medium span in China. Although cast-in-place method is easy, it requires a great number falseworks. When span is longer, the bridge should be divided into many segments. Cantilever method is not limited by terrain, but structural system would be transformed in many times. Type 250km/h, cast-inplace, ballast 350km/h, cast-inplace, nonballast 350 km/h segments cantilever nonballast Table 5: major design parameter of several most frequently used continuous beam bridge Length Span Beam depth Width at top Width at bottom Bearing spacing vertical stiffness Concrete volume (m 3 ) Strand (straight/curv e) (t) steel( nonbarrier/ withbarrier)(t) / / / /5.0 1/ / /4.35 1/ / /4.15 1/ / / / /5.0 1/ / / /5.0 1/ / / /5.0 1/ / / /5.9 1/ / / /5.9 1/ / / /5.9 1/ / / /5.8 1/ / / /5.7 1/ * 2.8/3.0 and 5.74/ 5.68 is at the middle span/ on the pier) With the construction of a large number of HSR passenger line, precast segmental bridge has been gradually popularized. This method first appeared in 1960s in Europe, which was developed from pre-fabricated cantilever method. First, the entire bridge span was divided into appropriate sections.

6 Then, segments were made in the factory near construction sites and transported by vehicles, and be installed in place by equipments, then strands will be tensioned. Though this method has been widely used in Europe and United States, China is still under the initial stage because of unskilled workers and backward equipments. Anyway, this method speed up construction speeds of HSR and ensure quality as well as configuration of the bridge. Meanwhile, due to its short conservation time, late loading time and less prestress loss, it suitable for large-span continuous beam in HSR. 5. Pier and infrastructure standardization 5.1 Pier standardization To speed up construction of HSR, bridge substructure should be also standardized. As for pier, five major types has been selected for superstructure: round plate piers, twin rectangular column piers, single round column piers, twin round column piers and round hollow pier. During the selection of the piers for Beijing-Shanghai line, a detailed analysis was carried out in order to coordinate box girder and harmonize the landscape. Finally, streamlined round soild pier, round hollow piers, rectangular hollow piers and twin-column piers were used. Round hollow piers and rectangular hollow piers used in Wuhan-Guangzhou line is shown in Figure 10, 11. It simplifies the appearance for the pier with no cap, and can through the rational control the proportion of the stiffness of the piers to substructure to control the economy of the substructure. Fig. 10: Round hollow piers 5.2 Based standards Apart from rock ground, the pile foundation often used for bridges in HSR with diameter of 1.0m, 1.25m or 1.5m. In general, simple beam using the bored piles of 8φ1.25m, and the continuous beams 8φ1.5m. There are two layout kinds of pier foundation: determinant and plum-type. Under normal geological conditions, for the piers condition of bridges below 20m, we can accord 8φ1.0m, 9φ1.0m, 11φ1.0m or 6φ1.25m, 8φ1.25m, 9φ1.25m to arrange the piers. For general low-level, in the economy, the small-diameter bored piles are better than the large-diameter ones. There for, we should maximize the use of small-diameter bored piles from the perspective of scattered by the force, but if the pile length exceeds 50m, we should use bored piles of larger diameter. 6. Large-span multi-line bridges Fig. 11: rectangular hollow piers Table 6: major design parameter of several large span HSR bridge in China Items Tianxingzho Dashengguan Xihuahuai Tingsi River Liangjiawan Chencun u Bridge Bridge Bridge Bridge Bridge Bridge type Cable-stayed Continuous Basket handle Continuou Steel truss arch Tied-arch bridge rigid frame bridge s beam speed 200km/h 300km/h 250km/h 350km/h 350km/h 350km/h main span/m deck width/m / /17.0

7 Live load 2-HSR line 2- I railway 6- highway 2-HSR line 2- I railway 2-light rail 2-HSR line 2-HSR line 2-HSR line 2-HSR line * 13.4/8.5 and 23.4 /17.0 is at deck top/ at deck bottom); 2- in the live load mean the number of lines. In order to meet the clearance restrictions or avoid difficult construction condition, a series of bridge with special span has been designed, including continuous rigid frame, variable cross-section continuous beam, arch, cable-stayed bridge, as shown in Table 6. Tianxingzhou Bridge in Wuhan-Guangzhou line and Dashengguan Bridge in Beijing-Shanghai line are the representations of large-span multi-line bridges. Tianxingzhou Bridge, mixture for highway and railway, is cable-stayed bridge with 1092m total length, steel truss girder, double pylons and three cable planes of fan shape, bridge design speed 200km/h. The arrangement of main bridge is m. The 756m steel truss girder is a composite structure combined high way deck and main steel truss, shown in Fig 19, for six lanes highway on the upper and four line railways on the lower. The inverted Y-shaped has been chosen in reinforced concrete main tower with a total height of 190m. Dashengguan Bridge with two navigable access adopted six-span continuous steel truss arch bridge, with main span of m. Three trusses as load-bearing structure had six railway lanes above, with total width 41m. The double continuous steel arch trus in the middle of main span had the height of 84.2m, with span ratio about 1/4 and the height of vaulted truss is 12m. The traffic volume in China is so high that large span bridge should supported multi-line load with three main trusses. In addition, there are a large number of different types of bridges, including the basket handle arch, tied arch, steel truss arch. In Wuhan-Guangzhou line, for example, the large-span continuous beam, continuous rigid frame, basket handle tied arch. Moreover, these kinds of bridges types also tend to standardized, such as basket handle arch with main span of 112m and tied arch of 140m have also been used in other lines. In this way, the speed of HSR construction in the future will much faster than ever before. 7. Summary and discussion By the summarization, we can see that there are three mainly improvements in HSR bridge of China: (1) Development on codes of HSR bridge design: Through the study of experience at domestic and international workplace, a series of temporary regulations has been gradually complied, as a catalyst in today's HSR bridge design of China. Next step, these temporary regulations will be gradually refined and improved in order to establish a set of requirements for HSR bridge design in China and other counties. (2) Standardization of design and construction. It can be seen that the standardized design and manufacturing, including the superstructure and substructure, can substantially increase the construction speed than HSR project in other counties. It lay laying a solid basis for achieving the goals for the plan of passenger line and inter-city express in Plan of Middle and Long-Term Railway Network and the "Eleventh Five-Year Plan". (3) Completion of multi-line large span bridge. Several large-span bridges for HSR passage line across the Yangtze River, Yellow River has been designed and constructed, including Tianxingzhou Bridge at Wuhan, Dashengguan Bridge at Nanjing, Zhengzhou Yellow River Bridge, Jinan Yellow River Bridge, etc. After the comparison of technical and economic, these several bridges mentioned above had steel truss structure which can provide superior stiffness. In order to meet the demands of span, heavy load and high-speed train, the design and construction of these bridges also adopted a number of new materials, detailed structural system, technology and equipment. Today, the technological improvement of design and construction in HSR bridge of China provided a valuable experience for reconcile the balance between economic issue, rapid construction and quality control for future construction. The achievements of construction in China s HSR in recent years were rooted from comprehensive study on advanced technology from other counties, such as

8 Germany, France and Japan, etc. However, since the completed mileages of China s HSR have ranked at the first place in the world, the problems encountered in the design and construction has also become the new challenge among HSR development. Therefore, the design and construction of HSR bridge in China cannot solely rely on foreign technology and experience, but improve and optimize on the basis of further learning. Therefore, by the experience in, we also need to realize the new challenges in design and construction of HSR in the future. References [1] ZHENG J. China s High-speed Railway Bridges. Beijing: Higher Education Press, [2] The Ministry of Railway of P.R. China. Temporary Provision for Passenger Railway Line of Km/h. Beijing: China Railway Publishing House, (in Chinese) [3] The Ministry of Railway of P.R. China. Temporary Provision for Passenger Railway Line of Km/h. Beijing: China Railway Publishing House, (in Chinese) [4] SUN S. L. Bridge Engineering of Beijing-Shanghai High Speed Railway. The Proceedings of 2008 China International High-Speed railway bridge technology collection. Beijing: China Railway Publishing House, [5] The Ministry of Railway of P.R. China. Code for design on reinforced and prestressed concrete structure of Railway Bridge and culvert (TB ). Beijing: China Railway Publishing House, (in Chinese) [6] NIU B. Overview of China s High-speed Railway Bridges. The 18th Conference Proceedings of the Bridge (first volumes). Beijing: People's Communications Press, [7] XU K. L., ZENG X. L. Technical Summary of Overall Design Engineering for Wuhan- Guangzhou Passenger Line Station, Technological collection for the construction of the Wuhan-Guangzhou passenger line. Southwest Jiaotong University Press, (in Chinese) [8] JING K., XU Y. Technical Summary of bridge design of Wuhan-Shaoguan belonged to Wuhan-Guangzhou Passenger Line, Technological collection for the construction of the Wuhan-Guangzhou passenger line. Southwest Jiaotong University Press, (in Chinese) [9] Nan HU. Gonglian DAI, The Introduction of High-Speed Railway Bridges in Wuhan Guangzhou Passenger Line, IABSE Symposium 2009 Bangkok, Volume96, p62.