Construction Systems

The BBR Network offered an extensive experience in construction systems, such as Heavy Lifting, Launching, Balanced Cantilever, Advanced Shoring and other temporary works construction methods and techniques.

The balanced cantilever method is often appropriate and cost-effective for the construction of long spans where bridge height, topography, or geotechnical conditions render the use of conventional falsework uneconomical.

Cost-savings are achieved partly due to the construction method and partly due to the structural system. Previously cast portions of the superstructure can immediately be used to support the construction of new segments, making possible the use of short, economical formwork travellers. Formwork is adjustable and can be reused many times. The regular repetition of identical tasks for the construction of each of the segments substantially reduces the ratio of labour costs to material costs. The use of short segments makes possible an economical prestressing layout that closely matches the moment diagram. In classical cantilever construction, cantilevers are built out symmetrically from pier tables in segments ranging between 3 and 5m in length. The construction sequence for a given segment consists of the following steps:

• Prestress the previously cast segment
• Advance formwork travellers to their new position
• Anchor travellers to the newly prestressed girder end and adjust formwork
• Place reinforcing steel, couple new tendon ducts with empty ducts in the completed portion and pull prestressing steel into ducts
• Cast the new segment

The economical range of span length for cast in situ cantilever construction begins at roughly 70m and extends to beyond 250m. For long spans, the ratio of falsework and formwork cost to total superstructure cost ranges between 25% and 35%, independent of bridge height and topography. This represents a considerable saving over conventionally cast in situ brides for which ratios of 40% are typical.

In simple terms, "heavy lifting" is a hydraulic lifting technique especially developed for extremely heavy loads. Load handling systems often result in considerable savings of time and costs compared to conventinal techniques. This modern and efficient system can largely substitute traditional lifting, lowering or shifting of heavy elements.

The BBR Network offers complete systems for heavy lifting which have been used on many diverse projects around the world. Load handling systems require full consideration at an early design stage for strucural detailing, constuction planning an selection of the rights equipment.

Within the BBR Network, there is extensive experience in the field of load handling and a complete range of services from the planning, engineering, equipment supply and execution of any heavy lifting project can be provided - early involvement of our specialists results in a handling scheme that optimises the porject's economy, efficiency and schedule.

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