Box girder steel formwork

Pull-out box girder inner formwork forms the cells of precast box girders. Crown, movable side and bottom corner panels are joined by hinges, hydraulic cylinders and linkages. Once the concrete reaches the required strength, the panels fold and retract in sections and the assembly is withdrawn longitudinally before moving to the next girder position. Xinhang plans panel divisions and withdrawal paths around cell clearance, section changes, access holes and end openings, coordinating uplift restraint, positioning and efficient stripping.

Folding retraction and assembly withdrawal: Cylinders and linkages retract the side and bottom corner panels inward in sequence. Once clear of the concrete, the assembly is withdrawn longitudinally along the main beam guide rails, avoiding individual panel dismantling inside the cell and making stripping labour and time easier to manage. Grouped hydraulic actuation: Lifting, lateral and folding cylinders operate in groups. Stops and guides coordinate closing, expansion and retraction, with a defined sequence and centralised operation to reduce manual assembly errors. Uplift restraint and cell geometry control: Vertical ties, hold-downs and supports locate the inner forms against uplift and asymmetric casting loads. Web thickness, cell clearance and top slab thickness are checked within the same formwork layout.

Provide cross-sections and longitudinal drawings, cell and access-hole dimensions, prestressing and embedded-item details, casting-bed layout and placement method. Confirm panel divisions, hydraulics, withdrawal direction and traction method in the project scheme.