Top-down construction method as the name implies, is a construction method, which builds the permanent structure members of the basement along with the excavation from the top to the bottom. Top-down method is mainly used for two types of urban structures, tall buildings with deep basements and underground structures such as car parks, underpasses and subway stations. top down construction technique top down construction definition top down building construction top down construction method definition up down construction top down bridge construction technique bottom up construction method top down bridge construction environmental engineering project topics final year project topics environmental topics for projects environmental engineering research topics engineering final year project ideas environmental engineering projects final year computer engineering projects final year project for electrical engineering top down construction method definition top down construction video top down building construction top down bridge construction top down construction technique top down construction top down design definition top down management definition

1. TOP DOWN CONSTRUCTION
PRESENTED BY
AGLAIA

2. TOP DOWN CONSTRUCTION
• Top down construction is the reverse method of bottom-up construction in
which the permanent structure is built from top to bottom of the basement
along with deep excavations.
• In this method, the basement floors are constructed as the excavation
progresses. basement concrete slabs act as lateral bracing for the perimeter
wall system.
• Ground level and subsequent basement slabs are poured, accessing holes
left to allow excavation beneath.
• As each subsequent subgrade level is completed, the floors act as lateral
bracing for the perimeter wall system.

3. • Perimeter wall which is generally referred to as Diaphragm wall (or D wall) is
a single, safe solution for all the constructional problems encountered
in underground construction.
• D walls provide effective earth retention and good control over ground water
movement.
• It’s capable of carrying the superstructure loads, providing early utilization
of the superstructure even before the completion of substructure of that
building.
• The top down method is used for deep excavation projects where tieback
installation is not feasible and soil movements need to be minimized, metro
station construction, tunnel construction, underground construction etc.

7. CONSTRUCTION PROCEDURE:
1. Construct the perimeter wall, Constructpiles. Place the steel columns
or stanchions where the piles are constructed.
2. Cast the floor slab of first basement level.
3. Proceed to the first stage of excavation.
4. Start construction of the superstructure.
5. Cast the floor slab of the second basement level Proceed to the second
stage of excavation.
6. Repeat the same procedure till the desired depth is reached.
7. Construct the foundation slab and ground beams, etc. Complete the basement
8. Keep constructing the superstructure till it gets finished.

8. ADVANTAGES
• Early restoration of the superstructure is possible even before the
completion of the building and the structures aboveground can be carried
out simultaneously with the structures below ground. This greatly reduces
the time for construction.
• Concrete diaphragm walls are more cost-effective when they can
simultaneously function as a groundwater cut-off and temporary soil
retention system during the excavation phase of the project, and then as
permanent underground walls with load-carrying capabilities for the finished
structure.
• Easier and economical construction of roof since it can be cast on prepared
grade rather than using bottom forms.

9. • The structural slab act as an internal bracing for the support of
excavation, thus reducing the number of tiebacks required.
• The virtually vibration-free operation minimizes the potential for
ground movement and its resulting detrimental settlement.
• It requires less width for construction area. Reduced
environmental pollution associated with pre-construction
earthworks.
• Eliminates the need to underpin adjacent structures

10. DISADVANTAGES
• Inability to install external waterproofing outside the walls.
• Potential water leakage at the joints.
• More complicated connections for the roofs, floor, and base slabs.
• Access to the excavation is limited and limited space for the
construction of base slab.
• Complex design involved.

11. Thank you
Lintels
For more…. Mail to aglaiaconnect2018@gmail.com