Save natural resources
To preserve our planet it is vital to save natural resources during construction and life-time of a project.
Optimise design with reusable equipment
Contributions to sustainable construction and to more environmentally-friendly execution of work have been part of the VSL Technical centres’ objectives for a long time. The main scope of engineering works covers – among other aspects – the design and detailing of major erection equipment such as launching gantries, lifting frames, and form travellers. VSL’s Technical centres assist other parts of VSL around the world in saving thousands of tonnes of steel in new fabrication of erection equipment through optimized design and, in particular, the reuse of existing equipment.
- A single gantry has erected about 2,700 segments on four projects. It proved to be a sound investment for VSL Malaysia to take back the Second Link gantry used on the Mekong River crossing after two years duty on the Pakse Bridge in Laos. The gantry was immediately reused for the Bayan Baru Viaduct, followed by the Subang Kelana Link Project in Kuala Lumpur. Reuse of the erection gantry saved an estimated 1,100t in new steel fabrication for the last three projects.
- The VSL underslung type-II gantry that was first commissioned for the construction of the West Rail Project in Hong Kong in 1999, where eight gantries were used to erect 8,050 segments. By early 2009, this family of gantries has been deployed to eight other projects around the world, including three other viaducts in Hong Kong, two in Australia, one in China, one in Thailand and one in South Africa, successfully erecting about 18,000 segments overall. Estimated savings in new steel fabrication for erection gantries have been in excess of 5,140t.
- Two overhead gantries were commissioned for the Deep Bay. Link Project in Hong Kong in 2004 for the erection of precast segmental viaducts weighing up to 910t per span. Following on from this project, the twin gantries were assigned to two different parts of the world, with one erecting bridge decks span-by-span on the Suvarnabhumi Airport Rail Link in. Thailand, while the other was adapted to execute free cantilever construction of the Alpurt Waiwera and Newmarket Viaducts in New Zealand. More than 4,500 segments have been erected by the two gantries. The savings in new steel fabrication of erection gantries for the last three projects amounts to about 2,000t.
Other savings in new steel fabrication in precast segmental construction projects are obtained by reusing lifting frames, as seen on the Lai Chi Kok Viaduct when the lifting frames from the Shenzen Western Corridor and the West Tsing Yi Viaducts projects were reused.
VSL’s Technical centre in Singapore has also developed reusable erection equipment for methods other than precast segmental construction:
- The development of the VSL modular form traveller for free cantilever bridge in-situ construction allows relatively simple and straightforward recycling for similar bridge geometries. The VSL modular form traveller can be adapted to complex geometry and other constraints, as for the construction of decks for cable-stayed bridges such as the Bai Chay Bridge in Vietnam.
- Lifting frames for steel segment erection of cable-stayed bridges can be reused, as in the case of the Industrial Ring Road Bridge followed by the Southern Outer Bangkok Ring Road, both in Thailand.
- Adaptation was carried out of a precast I-beam erection gantry for the Nan River, Pamok, Ramindra Bridge and the Thalingchan Bridges, in Thailand. One gantry was also sent to the Cebu Viaduct and subsequently the C-5 Ortigas Bridge in the Philippines.
- Reuse has also been possible for miscellaneous temporary steelworks, such as the launching nose for the Kemana Bridge in Malaysia, an incrementally launched bridge and pier cross-head support beams for Deep Bay Link in Hong Kong.
Increased structural stability of buildings
Using VSL R-dampers combined with post-tensioned floors makes the whole structure -from the foundations to the top -lighter than traditional methods, while providing a more ductile and resilient structure for the control of vibrations. With its optimised design, the VSL R-damper works effectively in dissipating energy in structures subject to vibrations arising from any external source, such as pedestrians walking on a floor, cars on a bridge, wind or earthquake. The damper dissipates part of the energy input while the structure itself only has to cater for the balance of the total forces generated by the vibrations. Damper stiffness and location need to be well matched to the structure displacements for optimum performance and efficiency.
Installing the dampers allows the engineers to design the structure for lesser effects, resulting in reduced element sizes in the lateral load-resisting members and the most effective use of the materials required for construction. Use of post-tensioned floors provides a further reduction in the total weight of the superstructure, and consequently in the base shear and over-turning moment. This means that the foundations are reduced as well. The VSL R-dampers require only limited maintenance due to their simplicity and very high durability. All these benefits lead to significant cost savings and, more importantly, the dampers contribute to safer structures at lower overall cost.