Foundations A foundation supports the weight of the building The foundation may be called the substructure The part of the building above the ground is called the superstructure Without a substructure the superstructure would sink into the ground Foundations are usually made of steel reinfor ID: 529859
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6. BuildingsSlide2
Foundations
A foundation supports the weight of the building. The foundation may be called the substructure.
The part of the building above the ground is called the superstructure. Without a substructure, the superstructure would sink into the ground. Foundations are usually made of steel reinforced concrete.Slide3
There are three types of foundations: raft, box, and pile.
The raft or floating is a slab of concrete on the surface of the ground. Houses and factories may be built using a raft foundation.Slide4
A box foundation is built into the ground and is usually made of concrete. The hollow space may be used for a basement. Most houses and tall buildings are built with this type of foundation.Slide5
Buildings require a pile foundation when built in soft soil. In a pile foundation, steel tubes are driven into the ground and filled with concrete.Slide6
Roofs
The appearance of a building is often
dictated by its roof. There are three types
of roofs: flat, sloped, and domed.
Roofs are heavy and the walls must be built strong enough to support them. Wind, rain,, and snow also place loads on the roof which must be supported by the walls.Slide7
Flat roofs are useful because they do not push sideways on the walls. However, they are less attractive and do not shed the rain and snow. Slide8
Sloped or domed roofs pose additional problems because they push out on the walls. Historically, the solution to this problem was to resist the outward thrust with thick, battered, or buttressed walls.Slide9
The walls of the Gothic Cathedrals had to be very thick to hold up the huge domed roofs.Slide10
Modern construction methods tie the lower ends of the sloping roof together instead of making the walls thicker.
Two sloped members with a tie across the bottom was the earliest type of truss. The tie is only subject to tension and could be made from a rope, a cable, or a wood brace.Slide11
The truss pushes down like a horizontal beam and not outward like a sloped roof.Slide12
Once a series of trusses are placed to form a roof they must be braced to prevent them from falling over. In a house, the roof itself can act as the cross bracing for the trusses.Slide13
When trusses are needed to span large areas, such as a hockey rink or aircraft hanger, a space grid is used. Trusses of equal strength and span are used in both directions.Slide14
The engineer has many designs of trusses to choose from when fabricating the roof of a building.Slide15
Walls
Walls support the roof and keep the occupants sheltered from the weather. There are two common ways of constructing the walls for buildings: bearing and framed.
Framed WallsSlide16
Load bearing walls transfer roof loads to the foundation and may be of the bearing or the framed type.
Non load bearing walls keep the weather out or serve as room dividers. Some buildings use concrete, stone, or brick walls to support the weight of the roof.
The bearing wall superstructure is used in factories and schools. Until recently, this was the common method of building.Slide17
Framed superstructures are built with a wood, steel, or concrete frame. A skin is applied to the frame to form the walls.Slide18
Skyscrapers are often built with a steel frame. Houses are built with a 2 x 4 or 2 x 6 wood frame. The outside walls do not support anything but their own weight.
The load bearing walls are subject to very high levels of stress. The load increases in the lower part of the wall as the weight of the stories above push down on the ones below.
One way of dealing with stress in a structure is to spread the stress over a larger area.Slide19
Battered walls are wider at the bottom than at the top. This spreads the weight of force over a greater area.
Battering also leads to greater stability because the bulk of the weight is at the bottom, making the wall difficult to push over.Slide20
Buttressing is common in tall buildings with high open roofs (such as churches and cathedrals). This prevents the outward thrust of the roof from pushing the wall over.Slide21
As the buildings become bigger and taller the buttresses became so large that they blocked most of the light from the windows. Holes were designed in the buttress to make a flying buttress.Slide22
Castle walls and dams are battered, but modern walls of brick or concrete are capable of taking the increased stress in the lower parts of the wall without battering.
Modern walls are built with footings under the walls to spread the load over the soil.Slide23
Tall Buildings
It would seem that the tall narrow buildings used today would require very thick walls at the base.
However, this would conflict with the need for large openings on the ground floors for retail or office space. Therefore, other systems must be employed.
TALL BUILDINGS WOULD REQUIRE VERY THICK LOADBEARING WALLSSlide24
The
continuous walls can be replaced by four posts and two beams. The posts must be very strong and have a very firm foundation.
This is the post and beam system. The columns or posts take up less space than the continuous load bearing walls
.Slide25
Post and beam construction systems predominate in the design of modern skyscrapers. One of the problems with the post and beam system shown above is that the columns must be larger at the bottom than at the top.
The cost of construction is high because every floor has columns and windows of different sizes.
Also, the amount of unobstructed space on the lower floors is reduced as well.Slide26
The
problem of different sized columns can be solved by placing additional columns inside the floor area.
Using major columns at the center or periphery and suspending the floors from cables eliminates this problem.
These buildings use tension as well as compression to hold the loads
.
Place columns in the floor area
Place columns around the peripherySlide27
There are so many variations in the methods that can be used to build high rise buildings that no two buildings look alike
.Slide28
Arches and Domes
Arches do not cover much space and are not stable in a lateral direction. Arches can be placed together to form what is called a barrel vault.
A barrel vault can be modified a number of ways to form many interesting shapes.
By joining four barrel vaults and removing the excess, a groin vault is created. It touches at four points and is joined with ties to prevent outward thrust.Slide29
An arch rotated around a vertical axis will form a dome. A dome, too, is a very stable structure.
Like all arches, the dome has a tendency to push outwards at its feet. This can be prevented by adding either buttresses or a tension hoop placed around its circumference.
There are many variations
of the arch in architecture.Slide30
You have completed the Buildings tour. You can go over the information again and study it some more or if you feel you know the information well enough you can go and get the Buildings Quiz from Mr. Leidl.
Last card on the Buildings tour.