What is top down construction?
What is the sequence of construction of a basement?
When is the glory hole excavated?
What's the difference of excavation top down and bottom-up?
The “top-down” method allows excavation to continue in dense areas while allowing minimal building acquisition, traffic control or demolition during the duration of construction. As the name stated, the bottom-up method is constructed the structure from lowest level of building to the highest level of building.
What is top down in construction?
Top-down is defined by the use of the permanent internal structure as the temporary propping to the retaining wall, cast in a top-down sequence. The higher-level slabs are cast before the lower-level slabs to act as horizontal frames for wall support as the excavation progresses.
What is top down and bottom-up construction?
In the bottom-up method, the base of the structure is constructed and subsequently moves up to the surface. The top-down method sees the top slab being constructed and then construction moves downwards to the base slab.
What are the advantages of top down construction when excavating on a site with limited access?
Advantages Of Top Down Construction Early restoration of the superstructure is possible even before the completion of the building and the structures above ground can be carried out simultaneously with the structures below ground. This greatly reduces the time for construction.
What is an example of a top-down project?
Another example of top-down approaches included large-scale investment projects. For example, the Akosombo dam in Ghana built in the 1960s received investment from the World Bank and aid from the UK and USA. The dam provided electricity through a HEP plant for smelting bauxite into aluminium.
What is meant by top-down approach?
The top-down approach to management is one such strategy, in which the decision-making process occurs at the highest level and is then communicated to the rest of the team. This style can be applied at the project, team, or even the company level, and can be adjusted according to the particular group's needs.
What is the difference between bottom-up and top-down planning?
Top-down planning aims to take a company from general endeavours to specific goals, whereas bottom-up planning is a tactic that synchronizes specific targets into a general framework. However, as you will see in this article, these two opposing strategies often go hand in hand in practical applications.
Why is bottom-up approach better?
A bottom-up approach helps improve employee collaboration as everyone is involved in the decision-making process and has input into how things are done. Communication will be two-way, and employees will feel empowered to share new ideas with their managers.
Why are buildings built from the top-down?
The top-down construction method is said to provide significant savings in cost and time, as they allow the floors to be constructed at the basement level and hoisted to the top, rather than moving workers, construction material and equipment from floor to floor.
What is semi top-down construction method?
It was concluded that the access holes could be enlarged until a structural frame emerged that was simple to support but would still prop the excavation. This has been termed the Semi Top-Down Method.
How do you do deep excavation?
Deep Excavation Methods – 8 Methods Explained for Deep ExcavationOpen Excavation (Free Tilt Excavation) Method.Internally Shored Excavation Method.Island Excavation Method.Top-Down Excavation Method.Anadolu Excavation Method.Open-Close Excavation Method.Well Type Wall Method.Anchored Excavation Method.
What is up down construction?
The up-down construction method involves the construction of above-grade levels prior to (or in tandem with) the construction of below-grade levels within the same footprint.
Why would you use top-down construction?
Top/down or up/down construction methods are another method for constructing deep excavations. In this case the basement floors are constructed as the excavation progresses. The top/down method has been used for deep excavation projects where tieback installation was not feasible and soil movements had to be minimized.
Why would you build a building from the top-down?
By maximizing the structural efficiency of concrete and steel, the Top Down℠ Process system cuts total structural weight roughly in half compared to conventional construction. reduction of steel by 20% - 30%. Lower labor costs and accelerated schedules reduce special and general conditions.
What is up down construction?
The up-down construction method involves the construction of above-grade levels prior to (or in tandem with) the construction of below-grade levels within the same footprint.
What is semi top-down construction method?
It was concluded that the access holes could be enlarged until a structural frame emerged that was simple to support but would still prop the excavation. This has been termed the Semi Top-Down Method.
What Is 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.
What is the importance of early restoration of a superstructure?
This greatly reduces the time for construction.
What is top down solution?
A top-down solution requires access for the removal of soil and the supply of materials, which may be through the ground floor and substructure slabs and ventilation for the work below ground beneath permanent slabs. Consideration should also be given to safe methods of working and method for the excavation and construction of the substructure that is compatible with the available space and limited access.
What is the bottom up method of building?
In most common construction methods, buildings with underground parts are built by the bottom-up method where sub-structure and super-structure floors are constructed sequentially from the lowest level of basement to the top of the building. Though this conventional method, also called a bottom-up method, is simple in both design and construction, ...
Why are the top down slabs cast?
The higher-level slabs are cast before the lower-level slabs to act as horizontal frames for wall support as the excavation progresses. The 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.
What is the purpose of casting the floor slab of the first basement level with the opening to allow machines to be lowered?
Cast the floor slab of first basement level with the opening to allow machines to be lowered to excavate level below and for excavation material to be removed.
What attracts higher loads into the permanent structure?
The stiffer construction during the intermediate construction stages attracts higher loads into the permanent structure.
What is the top down construction method?
In top down method, first the tunnel structure is made and then the external environment of the tunnel is filled with embankment materials.
What is the purpose of protection of excavated parts from the effective factors outside the excavation and lack of effect of weather?
Protection of the excavated parts from the effective factors outside the excavation and lack of effect of weather conditions on the activities of the workshop due to its coverage and elimination of relevant hazards
What is double bit drilling?
In Double-Bit Drilling method, excavation of 2 basements is done simultaneously. At the lower level, which is on natural soil, a concrete slab is executed and then a high-level concrete slab is executed. Depending on the needs of the project, it is possible to use temporary piles to maintain the upper slab.
What is the final wall of a tunnel?
The retaining wall of the tunnel and subway, which is executed before the excavation begins, is usually a concrete diaphragm wall or secant piles. This retaining wall is ultimately the final wall of the tunnel structure.
What happens after the completion of an underground structure?
After the completion of the underground structure, the embankment operation is performed up to the level of struts and then the struts are removed and the embankment continues to the ground level.
When to remove foam from wall?
Removing the foams when the excavation depth reaches the level of the wall and ceiling joints
Which construction method is the best for Earth retention?
The top-down construction method is one of the suitable methods for Earth retention.
What is top down construction?
A simple definition of top down construction procedure is that the basement floors or substructure of the buildings are constructed in a manner that after completion of ground floor first, the basement floors are built from top to bottom floor by floor.
How deep is the deepest building in the world?
It would be interesting for you to know about top down construction; because the deepest in the world’s building is Jinping Laboratory, China mounting to 7,900 feet beneath a mountain. Almost everyone knows about the Empire State building to Burj Kalifa or likewise but only few knows the fact that race among masses is not just to go high but is to go deep as well.
How are steel stanchion columns reinforced?
After achieving the depth of one level of basement, the steel stanchion columns are reinforced by reinforcing bars and are made as permanent columns for the basement floor and similarly the diaphragm walls are also reinforced with increased thickness to become permanent part of the structure. Further Excavation.
Which approach can be used to construct substructure and superstructure?
The substructure and superstructure can be constructed in analogous approach.
Where is the underground garage in Boston?
The building stands on a parking garage that goes deep 80 feet into the ground marking as deepest excavated point of the city. The underground garage was constructed using the top down construction methodology done by Franklin, Milk, Pearl and Congress streets. The excavation for the basement was completed in 1990 and the reason for opting top down construction was that there were tall buildings up to 40 floors.
Is excavation a predecessor of foundation construction?
So in planning and scheduling excavation is meant to be predecessor of the foundation construction.
What is top down construction?
Top/down or up/down construction methods are another method for constructing deep excavations. In this case the basement floors are constructed as the excavation progresses. The top/down method has been used for deep excavation projects where tieback installation was not feasible and soil movements had to be minimized. Figures 1 through 2 show construction photographs from two top/down excavations in Boston. The general top/down construction sequence is shown in Figure 3.. The Post Office Square Garage in Boston (7-levels deep) is one of the best-instrumented and documented top/down projects in the US (Whittle, et al., Whitman et al., 1991).
What is the sequence of construction of a basement?
The sequence construction begins with retaining wall installation and then load-bearing elements that will carry the future super-structure. The basement columns (typically steel beams) are constructed before any excavation takes place and rest on the load bearing elements. These load bearing elements are typically concrete barrettes constructed under slurry (or caissons). The top few feet of a barrette with a steel beam can be seen in Figure 2. Then the top floor slab is constructed with at least on construction (glory) hole left open to allow removal of spoil material (Figs. 2, 3).
When is the glory hole excavated?
The excavation starting at the glory hole begins once the top floor has gained sufficient strength. Soil under the top basement floor is excavated around the basement columns to slightly lower than the first basement floor elevation in order to allow for the installation of the forms for the first level basement slab. Glory holes are left open within each newly formed basement floor slab and the procedure is repeated. Each floor rests on the basement columns that were constructed earlier (Fig. 2).
What Is Top-Down Construction Methods?
- When the retaining wall is cast in a top-down sequence, the inside permanent structure is used as temporary propping. For the purpose of acting as horizontal frames for wall support as the excavation moves forward, the higher-level slabs are cast before the lower-level slabs. Tall buildings with deep basements and underground constructions like par...
Top-Down Construction Sequence
- Following is the standard top-down construction sequence:
1. Put the retaining wall in place (usually a diaphragm wall). 2. Create piles. Where the piles are built, install the steel columns. 3. Start the first phase of the excavation. 4. First basement level floor slab should be cast with an opening to allow machinery to be lowered to excavate level bel…
Top Down Construction Advantages
- Not every project is a good fit for the top-down construction approach. However, the following benefits are available to projects that use this methodology: It enables foundations to be built at ground level for basement applications. First, the piling rig does not need to be demobilised and re-mobilized between the building of the basement wall and the foundation construction, which …
Top Down Construction Disadvantages
- Ever wonder why traditional bottom-up construction methods aren’t employed more frequently than top-down ones? Here is a list of some of the drawbacks of top-down constructionthat may make it a less desirable choice. There are a limited number of concrete trucks, concrete pumps, and reinforcement deliveries that can be accommodated at any given time if there are access co…
Top Down Construction Philosophy
- In construction, like most things in life, time is money. In project management terms, you may hear of items which “lie on the critical path”. The critical path of a project is the chain of events and tasks which must be completed sequentially in order to finish that project. When constructing a building, the majority of the structure is a critical path item. You can’t lay the carpet or install th…
Top Down Construction Methodology For Basements
- You may see top down construction most commonly used for basement construction. The basement construction can take up a significant portion of the overall construction time for a project. For a thorough look at the types of basement construction and piling in general, take a look at THISarticle. During the first phases of top down construction, the basement wall piles ar…
Top Down Construction For High-Rise Buildings
- Top down construction can also be adopted for elements of the building above ground level. A mixed-use high-rise tower may contain multiple usage across its height. A building might range from apartment buildings in the upper tower, split by an amenities level (swimming pool and gym), commercial offices in the podium all above a large entrance lobb...
Top Down Construction Advantages
- The top down construction method doesn’t suit every project. However the projects which benefit from using this methodology can enjoy the following advantages: 1. For a basement application, it allows the foundations to be constructed at ground level. If piles are proposed as the foundation system it provides a number of benefits for, firstly the piling rig does not require demobilisation …
Top Down Construction Disadvantages
- Ever wonder why top down construction isn’t used more widely than conventional bottom up construction techniques? here is a list of some of the disadvantages of top down construction with can lead it to not being a preferred option. 1. If there are access restrictions to the site, there are only so many concrete trucks, concrete pumps and reinforcement deliveries which can be ac…
Conclussion
- There are other examples and reasons to use top down construction on different projects. If you have had experience in using top down construction on your projects feel free to share your experiences and insights via a comment below. Did this article answer your questions about top down construction? Do you have more queries? If so, please feel free to leave a comment below.