Top-down construction method Vinhomes Metropolis (TCE0007)

TOP-DOWN CONSTRUCTION METHOD

Top-Down, for High Rise buildings with more than 3 basement floors. Construction in parallel for superstructure and basement. Use of King posts (steel columns) embedded on top of RC piles, in order to temporarily support the superstructure and basement. Construction of basement, from top to bottom, after completion of ground slab

TOP DOWN METHOD FOR CONSTRUCTION

1. Construction of Piles and Diaphragm Wall
2. Installation of King posts (Steel Columns), embedded on top of piles. Those members provide support (temporarily) for a limited number of floors of superstructure, during the construction/completion of basement slabs/columns.

Note: The strength of the King Post is neglected, in the calculation of capacity of RC column, at the permanent condition.

3. Construction of Ground floor Slab, supported on the King Post. Sufficient slab openings and ramps must be provided, in order to ensure logistics/excavation material removal, reinforcement transport/installation to lower floors, casting concrete.

Continue with Construction of Superstructure Floors

4. Start Excavation for Basement, Construct Slab B1, then continue to B2..
5. Complete excavation
6. Complete Foundation slab, Mass Concrete casting
7. Casting Permanent RC columns/Core Walls and inject Grout on top

TOP DOWN METHOD FOR CONSTRUCTION

Assumptions:

• The king posts have the capacity to carry limited number of floors of the superstructure .
• Lateral stability of king posts in ensured through Basement Slab, Connected to the Diaphragm Walls. Monitor of deformations at all stages of construction.

Benefits:

• Speed construction, allowing the superstructure being built as soon as the piling/king post is completed.
• Allowing the Construction for the cases where open excavation can not be executed (if neighboring structures exist) or deep excavations are required. This will require anchoring to Diaphragm Wall or heavy type steel bracing
• Economic and easier design for Diaphragm Wall, in top down the free cantilever part is limited by the basement floor slabs, which act as horizontal diaphragms.

Disadvantages:

• Construction difficulties during excavation of the basement, excavators must not damage or hit the King Post, slow removal of soil material and transport/installation of reinforcement bars
• Safety of workers, sufficient ventilation must be provided/lighting
• Increased Cost