DYWIDAG Post-Tensioning Systems Secure North-South Transport in Laos

Just in time for the beginning of the 2009 Southeast Asian Games, the most significant public event to be hosted by Laos in 2009, the new Hinheup Bridge was inaugurated. The new bridge over the Nam Lik River is the principal connection on National Road No.13, which runs North and South through the capital of Vientiane. Connecting Cambodia and China, National Road No.13 is the most important highway in Laos.

The existing 145m long and 5m wide Bailey bridge, which was opened in 1915, only allowed for traffic in one direction at a time. The old steel bridge was severely damaged by three major incidents during its life; the last was in 1981, when a giant flood wave washed away the superstructure. Since then, the old bridge had continued to deteriorate to a stage that was life-threatening to its users. Severe deflection and bouncing of the bridge deck could be seen when heavy vehicles were crossing. During the construction of the new bridge, a 2m long section at the south end of the old structure broke away when a truck heavily loaded with timber tried to cross.

A financial grant for the project was provided by the Japanese Government through the Japan International Cooperation Agency (JICA) in recognition of the importance of the transit link between the provinces and neighboring countries. The new bridge also improves infrastructure in the province and will help alleviate the region’s poverty.

In accordance with a feasibility study carried out by JICA, the bridge was built using the Incremental Launching Method (ILM) in order to meet requirements in terms of capacity and length of the bridge as well as the hydrological pattern of Nam Lik River. Utracon Overseas Pte Ltd, a foreign subsidiary of Utracon Structural Systems Pte Ltd in Singapore, was engaged as the specialist sub-contractor to carry out incremental launching, post-tensioning and other specialist work for the bridge superstructure. Utracon was backed by its commendable track record on previous JICA funded projects in Asia.

In co-operation with the general contractor, Utracon carried out construction work in accordance with the JICA’s strict guidelines in terms of environmental friendliness and social sustainability. Hinheup’s natural reserves such as the surrounding rain forest, the encircling mountains and the river with huge stacked stones were all carefully protected. The construction compound was also restricted to just a minimal area.

The new bridge is 195m long and consists of 19 concrete box girder segments in lengths of 7.65m to 11.50m that were concreted in a sequential manner. The bridge deck measures 10.54m in width and is 2.80m deep. Posttensioning of the concrete box girders was carried out using DYWIDAG Post-Tensioning Systems. Type 12x0.6" DYWIDAG Strand Post-Tensioning Tendons were used for the longitudinal tensioning of the entire bridge. Utracon supplied most of the post-tensioning equipment and performed all of the posttensioning work for the bridge. Launching was done using a 32m long steel launching nose with two 480t heavy duty hydraulic jacks. Thanks to technical expertise, advanced equipment, precise logistics arrangements, and an experienced workforce, a construction cycle of 11 days per segment was successfully achieved.