Vietnamese bridge rises over River Cam in two day cycles

The end of 2004 saw the completion of in-situ concreting work on the two 101.6 m A-shaped pylons of the Binh Bridge in Haiphong. Using Doka automatic climbing formwork, the JV of Japanese contractors was able to make up for lost time and complete the pylons on schedule.

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By  Colin Foreman Published  March 5, 2005

Vietnamese bridge rises over River Cam in two day cycles|~|Doka137a-pic1.jpg|~||~|The new 25 m-high cable-stayed Binh Bridge spans the River Cam in Vietnam, linking Haiphong’s city centre to the northern districts of the city and on to the coal-mining province of Quang Ninh. At 22.5 m wide, it is being built with a steel-composite superstructure that will accommodate four lanes of traffic and two pedestrian walkways. The main span between the two pylons is 250 m long. The bridge is due to be opened to traffic in time for the celebrations on 13th May 2005, marking the 50th anniversary of the liberation of Haiphong. The short construction period left for constructing the two pylons called for a tried-and-tested formwork system — and some very efficient planning. The joint venture partners responsible for the bridge pylons, Shimizu and Sumitomo, finally opted for the Doka automatic climbing system. The equipment used here included SKE 50 automatic climbers in conjunction with Top 50 large-area formwork from Doka. As the pylon cross-section of 3 x 3.50 m has a relatively narrow (1.5 m diameter) service shaft, placing form-ties through the formwork was not a practical option. Doka therefore conceived the pylon formwork as a column formwork (for a solid cross-section), and used WU 22 steel walings to sustain the fresh-concrete pressure, rather than the WS 10 walings that come as standard with the Top 50 formwork. The formwork was diagonally tied from the outside, across the corners, using Universal angle tie bracets. Last but not least, the Doka automatic climbers made it possible to work in a two-day cycle which ensured very efficient progress on the two halves of the pylon, with no idling time: while pouring was in progress on the left leg of the pylon, the forming team could work unimpeded on the right leg, striking the formwork, raising the entire formwork system with the hydraulically actuated automatic climbers and then plumbing and aligning it. These operations were all carried out in under five hours by a group of between four and six men. On the following day, work moved over to the other leg: this time the formwork was struck from the left leg before being raised and then plumbed and aligned, while on the right leg, the next 3.62-m high typical section was poured. All the job-steps were quick and easy to learn and ran with considerable precision. In this way, the pylon rose 3.62 m every two days; one day on the left, the next day on the right. For the cylindrical inspection shafts, through which staff will climb up to the anchor-points of the steel cables inside the legs of the pylons, two specially produced steel circular formworks were used. These were located on shaft platforms and were repositioned by crane. Doka also supplied a special feature to go with the self-climbing systems for the pylon formwork — a catwalk that enabled site crew to cross safely between the two halves of the pylon. This walkway bridge was a steel framework construction that was raised by the Doka automatic climbers. Doka solved the problem of how to attach the catwalk to the automatic climbers highly efficiently, and with brilliant simplicity: the catwalk was fixed to an articulated support on one side, while on the opposite side it was non-rigidly mounted in a gondola-type construction. The bridge thus followed through on the lifting motions made by the automatic climbing formwork, and so was always automatically at the right height. Another great advantage here was that the contracting joint venture only needed one building-site hoist for each pylon. This meant some considerable savings in terms of site-related equipment and erection costs. The catwalk was able to withstand very high wind speeds and could sustain live loads of up to 1500 kg (15 kN). As the two halves of the pylon taper together towards the top, it made sense to shorten the walkway bridge every 4 - 5 concreting sections so as to adapt it to the shape of the pylon. The segmented design of the catwalk made it relatively easy to dismount individual 1.5 m- long elements that were projecting beyond the pylon. It proved possible to solve some tough formwork-technology challenges on the Binh Bridge project, thanks to the timely planning work jointly carried out by the Japanese joint venture and the Doka Formwork Experts. “It was only in this way that we were able to make up for the time that had been lost at the beginning, and to save lots of time and money into the bargain”, comments ISS JV pylon manager Siah Chee Seng, who — together with his team — supervised this project throughout the entire construction period. The Japanese joint venture was between the following firms: IHI Ishikawajima Harima Heavy Industries (responsible for steel-composite superstructure), and the Shimizu Corporation, with Sumitomo Mitsui Construction responsible for the piers and pylons.||**||

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