Cast-in-situ Method of Bridge Construction:
Cast-in-situ method of construction of bridges is a flexible method in which the demands of more unusual geometrical shapes can be easily coped with. This method is commonly used for short span bridges for the cost effective construction of solid, voided or ribbed reinforced concrete slab bridges. Each bridge type is build by designing the decks to allow each span to be cast in one continuous pour. Construction is simplicitic in form consisting of a birdcage scaffold with plywood formwork.
Where cast-in-situ construction is used for longer span bridges, the falsework system required becomes more sophisticated. Semi or fully mechanical falsework will require a specialized contractor. Semi-mechanical falsework will generally consists of steel beams or trusses which are then spanned between temporary towers. Fully mechanical falsework system is where a self launching gantry with steel lined shutters is used.
The type of false work system used will also have a bearing on the rate of span construction. For semi mechanical system each span will take between 2 to 6 weeks to construct. While for fully mechanical systems a span may be placed within 1 to 2 weeks.