Top Down Construction

Let’s pause on the Contract Management & FIDIC for a while and “get our hands in dirt”; talk about Top Down Construction Method. The time I have worked in Moscow, I had chance to see/work on a project within top down construction method on site. As per my observations Russian construction industry is well aware of this methodology and it is also known as Hi-Tech Method.

Why Top Down Construction

• If you have a project in crowded cities such as Istanbul, Moscow, New Mexico, New York, etc. most probably you will have problems about insufficient land, existing nearby buildings-structures and utilities
• And lets add more; your building has a deep basement or you are trying to build an underpass or subway station.
• If you are working at the planning part of the project it is obvious that one of the toughest critical paths will be excavation with a traditional bottom up construction project, besides the excavation related critical path would have effect on all over the project schedule.
• If tieback installation or ground anchors are not feasible and soil movements have to be minimized.

if your project have issues like one or more of the topics below you can start to think about the top down construction method.

What Is Top Down Construction & Advantages

• As the name implies, a construction methodology, which builds the permanent structure members of the basement along with the excavation from the top to the bottom
• The sequence of slab construction will be from the highest basement slab to the lowest basement slab.
• You can descend and ascend the structure concurrently so valuable construction time will be saved.
• A methodology that you can gain 70% time on your project.
• You will have advantage on the excavation related critical path.

Method of Work / Construction Method / Sequence / Procedure

The typical-basic construction methodology of top down construction is as follows;

• Preliminary Excavation.
• Construction of Guide Wall.
• Construction of the Diaphragm Wall / Retaining Wall.
• Construction of  piles. ; Placing the steel columns or stanchions where the piles are constructed
• Proceed with the first stage of excavation.
• Casting the floor slab of upper basement.
• Beginning the construction of the superstructure.
• Proceed with the second stage of excavation; Casting the floor slab of the second basement level.
• Repeating the same procedure till the desired depth is reached.
• Constructing the foundation slab and ground beams, etc.
• Compilation of the basement.

A sample video for better understanding;

[youtube=http://www.youtube.com/watch?v=iz5n_k8HF48&w=450]

PDF Documentation

• skyline steel Inc. , Top Down Construction Method Brochure; 

http://www.skylinesteel.com/assets/Bulletins/TopDownHybrid_TB.pdf

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• Yurkevich Engineering Inc.,  Top Down Construction Method Brochure

http://www.yurkevich.ru/pdf_publications/hi-tech.pdf

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