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rodsika
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Would anyone happen to know or have any links where these relationships were illustrated? I'd like to have an idea how deep are the foundations for say a 4-storey building versus a 6-storey building. Are they proportional?
scutterbob said:That is a very open ended question. In a general sense, yes a slightly taller building will require a slightly stronger foundation. But there are many considerations. Are you using shallow (bearing on soil) or deep foundations (piles/drill shafts)? Depending on where you are on earth, wind or earthquakes impart most of your lateral loading, which cause overturning moments and depending on how heavy (dead load) you structure is, it might either have selfweight to resist that, or require a foundation heavy enough, or for deep foundations piles with uplift capacity.
Also, just to be clear, I guess you are talking about an office of residental building when mentioning stories, realize some very large buildings are single story.
http://en.wikipedia.org/wiki/Vehicle_Assembly_Building
If, you are not concerned about any lateral loading causing overturning and it is a simple question of vertical loads. Then, for a shallow foundation, the depth probably would not vary, the size of the footing would. So you might be told the soil can support 1 tsf (ton per square foot), if your column load is 100 tons, then you'd need 100 sf. There are load factors, and reduction factors that would be applied as well depending on design codes that apply. If you are on a deep foundation, then in its case of how many piles and how deep, both of which will be site specific, and would determined by geotechnical investigation, typically through boring logs. A miniumum depth would be established, and normally capacity in piles increases with depth sometimes very quickly, 100 ton vs 120 ton might be a 50 ft pile vs 55 ft. There is no generalization however, this is entirely site specific, it might be 20 ft someplace and 250 ft somewhere else, soils vary.
http://en.wikipedia.org/wiki/Foundation_(engineering )
scutterbob said:σσNo, 2 to 6 storeys would probably not have to use piles again it absolutely depends on the local soils and other possible hazards. In coastal areas where scour is possible, then yes they almost certainly would have to be on piles and that still might not carry them through a hurricane. In areas with shallow bedrock from a bearing perspective no, but rock anchors or shear keys might be necessary.
Column sizes for small loads are often more geometry of rebar, and common form size driven then capacity. Even in larger loads, in an effort to reuse forms, the same size column may be used for many, many floors, and only the reinforcement is changed with load. In reality upper floors columns are much under utilized, but the savings in forms, and easy of construction make it worth the extra concrete used. Bottom line, optiming for most efficent use of material is often not least expensive.
Now, if you are only interested in the theoretical concept of column size to span ratio, and again depends on what constraints you hold yourself to. Simple span? interior or exterior column?
Storeys refer to the number of floors or levels in a building, while foundation depths correspond to the depth at which a building's foundation is placed.
Storeys and foundation depths are important considerations in construction as they determine the overall height and stability of a building. The number of storeys affects the design, materials, and construction method of a building, while the foundation depth needs to be sufficient to support the weight of the structure.
The number of storeys in a building is usually determined by the intended use of the building, local building codes, and structural limitations. Foundation depths, on the other hand, are determined by factors such as soil conditions, building type, and local regulations.
Some common factors that can influence the storeys and foundation depths of a building include the type of soil and its bearing capacity, the weight of the building, the local climate and weather conditions, and the intended use of the building.
In most cases, storeys and foundation depths cannot be easily changed after construction as they are integral parts of the building's design. If changes need to be made, it may require significant structural modifications and can be costly. It is important to carefully consider and plan storeys and foundation depths during the initial construction phase.