Chapter 12 Flashcards
What is a foundation?
foundation is the element of a structure which connects the structure to the ground, and transfers loads from the structure to the ground.
What are the jobs of the foundation?
1. Distribute the load to a large bearing area. 2. To load the bearing area with a uniform load. 3. To prevent lateral movement and support the super structure.
What are the parts of a foundation? Describe each
1. Superstructure: Habitable section of a building above grade. 2. Sub Structure: Habitable below grade section of a building. Foundation: Part of the building that transfers loads from the building to the ground.
What are dead loads?
Dead Loads are static or constant loads
applied to the structure from walls,
floors, etc..
What are live loads?
Live Loads are loads that change. This
includes movable objects, people, and
weather like rain and snow.
These two types of loads are considered
to be dynamic loads. They are often
considered live, but in some cases
require special consideration.
Wind and seismic loads
What is Bearing Capacity?
The weight that different soils or
substrata can support
Upward forces cause what?
Heaving
Downforces cause what?
Subsidence
What is Uniformly settling?
Uniform settling: building settles uniformly, but may cause disruption in services like entrances or other site features (water, sewage, or other services may be impacted).
What is differential settling?
•Differential Settling: Building settles at different rates and can cause damage to finishes, cladding and potentially the structural integrity.
What is the difference between differential and uniform settling?
Uniform settling is where the whole structure settles by the same amount; whereas, differential settling refers to stresses being placed on a structure that it was not meant to bear, and that could lead to contortion of the structure’s frame.
What is heaving vs. differential settling?
differential settling refers to stresses being placed on a structure that it was not meant to bear, and that could lead to contortion of the structure’s frame; whereas, heaving is just upward forces pushing on a structure.
How deep should foundations in our be to resist heaving?
36”-48” (3 feet - 4 feet)
What is shallow foundation?
A type of foundation that extends a relatively short distance below the ground and beat directly on the upper soil stratum.
If the total width of a building is
20’ and you decide to use a Wall Footing
at 4’ then you would be using what type of foundation?
Shallow foundation
What are two types of shallow foundations?
Foundation systems consisting of footings
Monolithic concrete foundation under the building’s entire footprint.
What is the footing?
The widened base of a column or wall is called the footing
What is the primary purpose of the footing?
to distribute the superimposed load on a large area of the soil so that the pressure on the soil is less than or equal to the soil’s strength (Bearing Capacity).
What are 4 types of footings?
Wall Footing
•Isolated Column Footing
•Combined Footing
•Cantilever (Strap) Footing
What is wall footing?
Footing runs continuously along the wall
above and transmits the load to the
ground.
What are 3 pros and cons of wall footings?
Pros Cons
1. Created below grade and 1. High concrete use and
often habitable sub structure. thus increasing cost
Thus increasing the total 2.Can be prone to heaving
square footage of the building. 3.If not properly checked
2. Easy space to run services. can become areas of
3. Can act as passive cooling. mold of infestation
What is column footing?
A shallow footing that distributes the
loads from the column to the pad below.
What is used to support individual columns on a
concrete pad?
Column footing
Column footings are made up of ?
Constructed primarily of reinforced
concrete
Column footings are connected via a ?
Columns are connected via a strap beam
What are four PROS of column footings?
PROS: •Allows structure to be raised off of ground. •Is more economical than a deep wall foundation or basement foundation. •In warmer climates the space below can provide passive cooling. •Often used in areas with a high water level.
What are three CONS of column footings?
CONS: •Space below building can be prone to moisture damage. Especially if you are using wood joists. •Space below floor has to be insulated during cold weather. •If not properly maintained can become areas of mold or infestation.
What is combined footings?
An economical column pad system when
columns are tightly spaced or pad may
extend beyond the property line.
Combined footings are made out of?
Constructed of reinforced concrete.
What are 3 PROS of combined footings?
1. very stable method of construction. 2. Best used in areas where columns are tightly packed. 3. Acts in same capacity as column footings.
What are 3 cons of combined footings?
• Most likely will require column strapping or a grade beam to build upon. •Added cost due to proximity of columns and increased pad size. •If a crawl space is used can become damp or infested.
What is strap footing?
Column pads are connected via a strap
beam when an adjacent column pad is
eccentrically loaded.
What type of footing is similar to strap footing?
Column footing
Wat is strap footing made out of ?
Constructed of reinforced concrete.
What are three PROS of Strap footing?
PROS: •Can allow for a diverse placement of columns in relationship to pad. •Allows the structure be built along a tight edge, like a property line (eccentrically loaded). •Acts in similar capacity as a column footing.
What is one Con of Strap Footing?
Due to the eccentric loading
requires an increase in
structural reinforcement, thus
increased cost
What are the three types of Monolithic concrete foundation under the building’s entire footprint?
Mat Foundation
Raft/ floating Foundation
Slab on ground Foundation
What is a Mat foundation (or Mat footing)?
A mat foundation is where all columns and walls of a building bear on one large, thick reinforced concrete slab.
These foundations are
cost effective systems to use on highly
compressed soil where low loading is
allowable. What are they?
The mat, raft, or slab foundation
What are three pros of Mat Foundation?
•Cost effective foundation system. •Versatile. •Eliminates potentially risky crawl spaces and basements.
What are three cons of Mat foundation?
Low bearing capacity. •Is susceptible to freezing and thawing heave in colder climates. •Requires highly compress soil or bearing area.
What is slab on grade foundation?
It is the most widely used monolithic foundation system because of its low cost. It functions as a foundation system and also as a ground floor of the building.
What is a raft foundation?
It is a type of mat foundation that consist of a hollow mat formed by a grid of thick reinforced concrete walls between two thick reinforced concrete slabs
This is determined by the
depth of the footing being greater than the
width of the building.
Deep foundations
deep foundations use depth to do what?
deep foundations use depth to
transfer loads to denser strata below like a
granite bedrock.
What are three types of deep foundation?
- Pile Foundation
- Pier Foundation
- Well (Caissons) Foundation
When are shallow footings usually used?
They are usually used when you want to distribute the superimposed load on a large area of the soil so that the pressure on the soil is less than or equal to the soil’s strength (Bearing Capacity).
When is a strap footing used?
Strap footing is used when you want to connect two isolated column footings
What’s is the difference between a raft and mat foundation?
A raft foundation is one that is made up of a grid of thick concrete walls between two thick concrete slabs that is forms a hollow mat; whereas, a mat foundation all columns and walls of a building bear on one large, thick reinforced concrete slab.
What are four cons in using wood piles in pile foundations?
- Pile will rot above the ground water level.
- Can be damaged during installation.
- Difficult to splice.
- Susceptible to aquatic borers.
What are four pros of using Pre cast concrete piles in pile foundations?
PROS: •Stable in squeezing ground (soft clay, silt, peat). •Are easily spliced. •Relatively inexpensive. •Can be driven at long lengths.
What are three cons of using Pre cast Concrete piles in pile foundations?
•High displacement, heave and disturbance of soil
during driving.
•Can be damaged during installation.
•Cannot be driven at pre determined sizes
What are 6 pros of using Cast in Concrete piles in pile foundations?
•Can be cut or extended to desired length.
•Relatively inexpensive.
•Pile length is flexible.
•Can enlarge base for increased bearing
capacity.
•Reinforcement not determined by driving.
•Can be install with low vibration disturbance
due to drilling vs hammering.
What are 3 cons on using cast in concrete piles in pile foundations?
•Pile can be damaged during set up if not
properly reinforced, or has is thinly cased.
•Time consuming. Due to the set up time of the
concrete you cannot use it after completion.
•Limited length due to either casing length or
auger depth.
What are 5 pros of using steel piles in pile foundations?
- Can be cut to desired length.
- Can be driven through dense strata.
- Can be spliced or bolted.
- Love drive deformation.
- Can carry very high loads.
What are three cons in using steel piles in pile foundations?
CONS:
•Piles will corrode and cannot be coated.
• Will deviate easily during driving.
•Price fluctuates with global market
What are three types of Alternate Piles?
- Micro Piles
- Helix Piles
- Rammed Aggregate Piers
What are Helix Piles?
•Helix piles are like a giant screw
that is augured into place and
finished with a pile cap.
When is it ideal to use helix piles and Helix piles are best used under what?
•Ideal for tight locations that are
not easily accessible with larger
machinery.
•Best used to under pin.
Allows for a shallower footing in a
deep foundation site. It also uses natural materials. What is this?
Rammed Aggregate Piers
Allows for a shallower footing in a
deep foundation site. It also uses natural materials. What is this?
Rammed Aggregate Piers
What it a Micro pile and when is its ideal use?
•Low impact pile that can be driven, or inserted into an augured hole. •Ideal for tight locations that are not easily accessible with larger machinery. •Excellent system for underpinning, repair, and foundation stabilization.
What it a Micro pile and when is its ideal use?
•Low impact pile that can be driven, or inserted into an augured hole. •Ideal for tight locations that are not easily accessible with larger machinery.
What pile is an excellent system for underpinning,
repair, and foundation stabilization?
Micro pile
In pier and caison foundations, a pier is dug to the bearing point and cannot be held in place by friction. True or false?
True. A pier is dug to the bearing point
and cannot be held in place by
friction.
This foundation type is common
in the construction of bridges
and often uses caissons to
accomplish this task. What type of foundation is this?
Pier and Caison foundation
What are four pros of Pier and Caison Foundations?
PROS: •Can be useful when there are large obstructions. •Can be utilized in or near water table. • When there is large lateral loads like a river. •Caissons are economical.
What are three cons of Pier and Caison Foundations?
•Time intensive due the additional excavation required. •Construction and excavation process is extremely sensitive due to increased precision. •Not good when soil can’t be disturbed.
What is a pile cap?
A pile cap is a concrete pad
that the superstructure will
be will be built upon.
Pertaining to foundation finishing, what do grade beams connect and create?
grade beam
connects columns to one another and creates a line
for walls to bear upon.
Pertaining to Foundation repair, what is underpinning?
Underpinning is best used to
support, repair, or replace an
existing foundation.
What are 5 problems that water can cause?
•Heaving • Moisture Leaching (potential mold growth) • Material Degradation •Uneven Settling •Cracking
