BUSI401 CHAPTER 2 Flashcards Preview

BUSI401 > BUSI401 CHAPTER 2 > Flashcards

Flashcards in BUSI401 CHAPTER 2 Deck (81)
Loading flashcards...
1

There are two main substructure categories. The first is a retaining structure that primarily resists lateral or sideways loading. Retaining walls and sheet piling are common examples of retaining structures. The second is a bearing or foundation structure that primarily resists vertical loading. Piles and pad footings are common examples of bearing structures. These two types of substructures can also be combined — an example would be a foundation wall in the basement of a house; it carries the weight of the house into the soil below and prevents the ground adjacent to the wall from collapsing inward into the basement.

There are two main substructure categories. The first is a retaining structure that primarily resists lateral or sideways loading. Retaining walls and sheet piling are common examples of retaining structures. The second is a bearing or foundation structure that primarily resists vertical loading. Piles and pad footings are common examples of bearing structures. These two types of substructures can also be combined — an example would be a foundation wall in the basement of a house; it carries the weight of the house into the soil below and prevents the ground adjacent to the wall from collapsing inward into the basement.

2

This chapter focuses on building foundation systems — generally referred to as building ________. In providing support for the building's structure, the substructure is crucial to a building's ____________ 

This chapter focuses on building foundation systems — generally referred to as building substructures. In providing support for the building's structure, the substructure is crucial to a building's integrity and stability.

3

The primary purpose of building substructures:

To ___________, and to _____________.

 

The loads include the weight of the building and its contents (________), plus the forces from occupants, wind, snow, earthquakes, temperature effects, and the weight of the soil adjacent to below-ground walls (___________).

The primary purpose of building substructures:

 

To transfer loads from the building to the ground, and to spread these loads evenly to prevent settlement or lateral movement of the building relative to the underlying soils. The loads include the weight of the building and its contents (dead loads), plus the forces from occupants, wind, snow, earthquakes, temperature effects, and the weight of the soil adjacent to below-ground walls (live loads).

4

The building substructure must be designed to withstand the following effects:

 

 

The building substructure must be designed to withstand the following effects:

 

Compression or downward pressure

 

Tension or upward pressure

 

Lateral or sideways pressure

 

Torsion or twisting pressure

5

How can building substructures  be subject to upward pressure?

Light structures can be prone to wind suction pressures that will pull the building out of the ground.

 

Soil that is saturated with water will result in buoyancy pressures where the portion of the structure that is below grade displaces the fluid (like a ball held under water will want to rise to the surface).

 

Also, wind or earthquake forces will push sideways on the building — for tall, narrow buildings, one side of the building may lift up if not anchored into the ground properly.

6

This force exerts upward pressure

Tension

7

There are two main substructure categories. The first is a ___________ structure that primarily resists lateral or sideways loading. ___________ and ________ are common examples of retaining structures. The second is a _______ or ________ that primarily resists vertical loading. ____ and ______ are common examples of bearing structures.

There are two main substructure categories. The first is a retaining structure that primarily resists lateral or sideways loading. Retaining walls and sheet piling are common examples of retaining structures. The second is a bearing or foundation structure that primarily resists vertical loading. Piles and pad footings are common examples of bearing structures.

8

This is sideways pressure

Lateral pressure

9

Lateral forces can occur as a result of _ _ _  _ _ 

Lateral forces can occur as a result of soil subsidence, hydraulic pressure, or seismic forces caused by earthquakes.

10

______or downward pressure, also referred to as ______. The main compressive force is the weight of the building, furnishing and fixtures, and its occupants — together these are known as __________.

Compression or downward pressure, also referred to as bearing pressure. The main compressive force is the weight of the building, furnishing and fixtures, and its occupants — together these are known as gravity load effects.

11

This force is twisting pressure exerted on the building.

Torsion

12

Torsion may occur through seismic events or high wind acting on the building. Torsion usually occurs on asymmetrically shaped buildings. If the building is much taller on one side than on the other, there is greater mass resulting in higher seismic forces and a greater wind area resulting in higher wind forces on that side of the building. The soil must resist the imbalanced forces to prevent the building from rotating.

Torsion may occur through seismic events or high wind acting on the building. Torsion usually occurs on asymmetrically shaped buildings. If the building is much taller on one side than on the other, there is greater mass resulting in higher seismic forces and a greater wind area resulting in higher wind forces on that side of the building. The soil must resist the imbalanced forces to prevent the building from rotating.

13

At any given time, there may be a combination of these forces acting simultaneously on the substructure. The National Building Code of Canada defines specific ___________ to properly account for these effects.

At any given time, there may be a combination of these forces acting simultaneously on the substructure. The National Building Code of Canada defines specific "load combinations" to properly account for these effects.

14

The design of a build­ing's substructure requires harmony between _ _ _ _ _ _

The design of a build­ing's substructure requires harmony between architectural science, soil mechanics, and civil engineering.

15

Inadequately designed high-rise building foundations can lead to dramatic results. In areas with unstable clay or sandy soils with high moisture content, __________ can lead to foundation settlement and ultimately to deformation and failure of superstructure elements. The most famous example of this is the Leaning Tower of Pisa in Italy.

Inadequately designed high-rise building foundations can lead to dramatic results. In areas with unstable clay or sandy soils with high moisture content, soil subsidence can lead to foundation settlement and ultimately to deformation and failure of superstructure elements. The most famous example of this is the Leaning Tower of Pisa in Italy.

16

In the structural design of a building, soil is treated similar to other construction materials like concrete or steel. Geotechnical engineers determine strength and stiffness properties of soils using standardized test methods. Soils are classified according to various characteristics such as density, moisture content, and silt content as a primary guide to determine the load carrying capacity. The effect of water on soils is significant and must be considered in foundation design. 

In the structural design of a building, soil is treated similar to other construction materials like concrete or steel. Geotechnical engineers determine strength and stiffness properties of soils using standardized test methods. Soils are classified according to various characteristics such as density, moisture content, and silt content as a primary guide to determine the load carrying capacity. The effect of water on soils is significant and must be considered in foundation design. 

17

Soil capacity is defined in two primary ways:

Soil capacity is defined in two primary ways:

1. Serviceability - This condition is defined in the building code and is related to occupant comfort rather than public safety. A substructure must be designed such that total settlement and differential settle¬ment are kept below a minimum level (typically 25 mm).

2. Ultimate strength - This condition relates to safety of the occupants. In this case, if the soil were to become overloaded to the point of failure, the building would be placed at risk of collapse or overturning.

18

To illustrate this difference, consider the soil as a marshmallow. If you place a light object on a marshmallow it will simply settle into it by a small amount. This is the serviceability condition. If you place a very heavy object on the marshmallow, it will sink very deep into it, it may pierce through the skin and it will likely tip over. This is the ultimate strength condition.

To illustrate this difference, consider the soil as a marshmallow. If you place a light object on a marshmallow it will simply settle into it by a small amount. This is the serviceability condition. If you place a very heavy object on the marshmallow, it will sink very deep into it, it may pierce through the skin and it will likely tip over. This is the ultimate strength condition.

19

If a structure is placed on top of the soil such that it increases the pressure on the supporting soil, the soil will deform. When a load is imposed on soil there are several microscopic interactions that take place:

Contact pressure between granules

Friction between granules

Compaction

Consolidation

20

When the soil is loaded, the water is pushed out of the void spaces. This causes the soil to settle through the process of _________.

When the soil is loaded, the water is pushed out of the void spaces. This causes the soil to settle through the process of consolidation.

21

_________ of soil causes an increase in density by pushing the granules closer together and decreasing void space.

Compaction of soil causes an increase in density by pushing the granules closer together and decreasing void space.

22

If you pour a jar of marbles on the ground, they will spread out and not form a pile, because their surfaces are smooth with little friction between them. In contrast, jagged rocks will form a pile and the more jagged the rocks, the steeper the sides of the pile can be. This property of the soil is referred to as the _________

If you pour a jar of marbles on the ground, they will spread out and not form a pile, because their surfaces are smooth with little friction between them. In contrast, jagged rocks will form a pile and the more jagged the rocks, the steeper the sides of the pile can be. This property of the soil is referred to as the "friction angle".

23

Other causes of soil deformation include  _ _ _ _ _ _ _. 

Other causes of soil deformation include frost movements and shrinkage. These deformations are the result of climatic changes.

24

Extending the foun­dation below the zone of frost penetration will prevent frost effects; this is the primary reason that _ _ _ _ _ _ _

Extending the foun­dation below the zone of frost penetration will prevent frost effects; this is the primary reason that houses in Canada have basements

25

______ is a strain produced in a material when one surface of a material is deformed laterally in one direction and the other in the opposite direction. Materials exhibit varying degrees of resistance in response to this lateral movement.

Shear is a strain produced in a material when one surface of a material is deformed laterally in one direction and the other in the opposite direction. Materials exhibit varying degrees of resistance in response to this lateral movement.

26

________ is a strain produced in a material when one surface of a material is deformed laterally in one direction and the other in the opposite direction. Materials exhibit varying degrees of resistance in response to this lateral movement. This resistance is called ________and is based on the molecular structure of the material. For example, rubber has very low shear strength and will deform readily, while steel is a material which has very high shear strength and is able to withstand great shear forces with negligible lateral movement.

Shear is a strain produced in a material when one surface of a material is deformed laterally in one direction and the other in the opposite direction. Materials exhibit varying degrees of resistance in response to this lateral movement. This resistance is called shear strength and is based on the molecular structure of the material. For example, rubber has very low shear strength and will deform readily, while steel is a material which has very high shear strength and is able to withstand great shear forces with negligible lateral movement.

27

Materials exhibit varying degrees of resistance in response to this lateral movement. This resistance is called __________ and is based on the molecular structure of the material.

 

For example, rubber has very low shear strength and will deform readily, while steel is a material which has very high shear strength and is able to withstand great shear forces with negligible lateral movement.

Materials exhibit varying degrees of resistance in response to this lateral movement. This resistance is called shear strength and is based on the molecular structure of the material.

 

For example, rubber has very low shear strength and will deform readily, while steel is a material which has very high shear strength and is able to withstand great shear forces with negligible lateral movement.

28

The shear strength of a soil is dependent on _____ and _____.

 

The _____ of a soil is primarily dependent on the water content and is a measure of soil's strength due to its particles adhering to one another.

 

The ______ component of shear strength is the measure of the ease with which individual soil particles can be forced to slide past each other.

The shear strength of a soil is dependent on cohesion and friction.

 

The cohesion of a soil is primarily dependent on the water content and is a measure of soil's strength due to its particles adhering to one another.

 

The friction component of shear strength is the measure of the ease with which individual soil particles can be forced to slide past each other.

29

The cohesion of a soil is primarily dependent on the ________ and is a measure of soil's strength due to its particles adhering to one another.

The cohesion of a soil is primarily dependent on the water content and is a measure of soil's strength due to its particles adhering to one another.

30

Soils with smooth particles have a very low friction angle whereas soils with rough particles have a high friction angle. It is for this reason that ________ is synonymous with ________.

Soils with smooth particles have a very low friction angle whereas soils with rough particles have a high friction angle. It is for this reason that friction angle is synonymous with shear angle.