Precast segmental design and construction in China - ABECE

1 Tailor Made Concrete Structures Walraven & Stoelhorst (eds) 2008 Taylor & Francis Group, London, ISBN 978-0-415-47535-8 Precast segmental design and construction in ChinaDong, Xu, Huichi Li & Chao LiuDept. of bridge Engineering, Tongji University, Shanghai, ChinaABSTRACT: In 2001, Liuhe River bridge in Shanghai was the first span-by-span Precast segmental bridgeconstructed by a launching gantry in China . In 2003, Humin Viaduct in Shanghai was the first project usingshort line segment casting for urban elevated viaducts. The biggest PC beam bridge using balanced cantileverprecast segmental construction in China is Jiujiang bridge in Guangdong province, which has two 160 m mainspans and was completed in 1996.

2 In July 2001, the first 4-span cable-stayed bridge in China , Yiling Bridgein Hubei province, using Precast segmental PC box girder construction , was completed. Although China hasthese successful references, the Precast segmental construction , originated from the contractor system, was notwell followed in time by design codes. Lack of specified design codes in China usually causes owners and evendesigners hesitate to use this construction method. Longitudinal mild reinforcing bars do not continue throughthe joints. The new concept of making closed horizontal shear reinforcement, with the addition of normallyarranged vertical stirrups, to carry the horizontal and vertical components of the diagonal tensile stress wasproposed in the reinforcement design of Precast segments for the approach bridges of the Sutong INSTRUCTIONSP recast segmental construction for prestressed con-crete bridges has been widely used in the method has many advantages, such as quality-guaranteed standard Precast segments, fast speedconstruction time and the least site work.

3 Lots of pre-stressed concrete bridges in the world were built byprecast segmental construction method in recent 20years[1].Although more and more Precast segmental bridgeshave been successfully built in China , this reason is that the precise control of the dimensionsof the bridge makes the construction much more com-plicated. Another reason is that the Precast segmentalconstruction method, originated from the contractorsystem, is not well followed in time by design construction method even well influences thestructural design including the profiles of internal andexternal prestressing tendons, the detail dimensions ofsegments and the arrangements of segments and devi-ators, etc. Due to these reasons, lack of the regardingspecified design codes usually causes owners and evendesigners to hesitate to use this construction RECENT construction REFERENCESIN segmental span by span Liuhe bridge in ShanghaiThe new Liuhe bridge in Shanghai consisted of3 42 m single spans.

4 The bridge had dual carriage-ways, each of which included 3 lanes of traffic. Theupward bridge was m in width, while the down-ward bridge was m. In order to be familiarwith the design method of segmental constructionwith external prestressing, the Precast segmental con-struction was adopted. The upward and downwardbridges consisted of two parallel single-cell box gird-ers, respectively. Each box girder was longitudinallydivided into 13 segments. The weight of a single spanwas 515 tons, and the weight of a m standard seg-ment was 40 bridge segments were precastedwith long-line method. A launching gantry was usedto carry and install all the segments into a bridge was the first span-by-span Precast seg-mental bridge constructed by a launching gantry inChina, as shown in Figure 1.

5 Mixed tendons were usedfor the longitudinal prestressing in the bridge . Most795 Figure 1. New Liuhe River bridge , installation of 2. New Liuhe River bridge , external the prestressing tendons were internal bonded ten-dons, while four 19T15 external unbonded tendonswere used in each span, occupying 24% of the wholeprestressing in a single span, as shown in Figure was completed in Oct. Elevated Viaduct in ShanghaiHumin Elevated Viaduct in Shanghai was the secondbridge using span-by-span Precast segmental con-struction using launching gantry in China , as shown inFigure 3. The total length of the viaduct was kmand the average span was 30 35 m. The 30 m spanswere made of 11 Precast segmental box girders, whilethe 35 m spans were made of 13 ones.

6 The girder seg-ments were 25 m in width, m in height, 2 m, mand 3 m in length. The weight of the Precast segmentsat pier tops was up to 130 tons and the standard seg-ments were about 110 tons. The segments were shortline precasted. Figure 4 shows the external tendons anddeviators in this half of the km viaduct was designedto adopt this method, most of the spans were builtby the traditional monolithic scaffolding constructionbecause of the restricted construction period. OnlyFigure 3. Humin Viaduct, installation of Precast 4. Humin Viaduct, external tendons and 5. Second Jiujiang sections were left to use Precast segmental con-struction, one in the main viaduct and another in aramp.

7 Each section included ten spans. The wholeviaduct, which has an appealing arc bottom shape, wascompleted in the end of 6. Approach bridges in deep 7. Precast segments storage segmental balanced Jiujiang BridgeAt present, the biggest bridge using Precast segmen-tal balanced cantilever construction in China wasthe Second Jiujiang bridge , completed in 1996 andlocated in Guangdong Province, as shown in Figure main bridge had 6 spans (50 m+100 m+2 160 m+100 m+50 m), including the two biggest160 ,themax-imum cantilever length reached to m, leaving a3 m cast-in-situ closure. The width of the deck seg-ments was m. All the prestressing system wasinternally water approach bridges of theSutong cable-stayed bridgeSutong bridge , with a total length of 8146 m over theYangtze River including a 1088 m cable stayed mainspan, was completed on June 28, 2007 and will opento traffic at the end of April this year.

8 The approachFigure 8. Launching gantry to assemble the 9. Installation of the deviator were wholly prestressed concrete continuousbeams including about 25 spans of 75 meters in deepwater (Fig. 6). Short line segment precasting and bal-anced cantilever construction were adopted (Fig. 7).Launching gantry was used to assemble the cantileversegments, as shown in Figure 8. The bridge is thelargest bridge project using Precast segmental can-tilever construction , launching gantry assembling andshort line precasting in segments, including the anchorage seg-ments and deviator segments (Fig. 9) were carefullydesigned and precasted. In order to keep the weightof all segments within 150 tons, the anchorage crossbeam, which occupies half of the weight of the piersegment, is casted in-situ.

9 Each span consists of six25T15 external tendons. A new external prestressingsystem was adopted in this bridge . The adopted exter-nal prestressing system was developed by the jointR&D center supported by OVM (Liuzhou) MachineryCo. Ltd. and Tongji University, as shown in Figure has two features. The first is the deviator device,which can comb the individual monostrands and guide797 Figure 10. External prestressing 11. External prestressing 12. Detail of the deviator of the one by one in deferent vertical and lateral cur-vatures (Figs 12 13). The second feature is that thestraight part of the tendon profile does not need tobe grouted (Fig. 14). It significantly reduces the selfweight of the tendons and facilitates the inspection andmonitoring of the strands during service time (Fig.)

10 15). segmental cable-stayed bridge over the Hanjiang RiverYunyang bridge , completed in 1993 and located inHubei Province, was a cable-stayed bridge withdouble bridge was the first long span earthanchored prestressed concrete cable stayed bridges inFigure 13. Profile of the deviator after 14. Connection of the deviator and the straight 15. Easy inspection of the , with 3 spans (86 m+414 m+86 m). The con-crete girder was box-section with three cells, usingthree-dimension prestress technology. The length ofthe segments were m and m and the maximumweight of the Precast segments was around 100 tons.(Fig. 16) bridge over the Yangtze RiverYiling bridge , crossingYangtze River inYichang Cityin Sichuan Province, was a 4-span cable-stayed bridge798 Figure 16.