1. Final Project - Structural

Question 1

What is the internal resistance to an external force?

Answer 1

Stress. (Tension, Compression, Shear, Torsion, Bending, Combined Stresses)

Stress f = total force P / total area A

Question 2

What are the three basic types of stress?

Answer 2

Tension, compression, and shear

Question 3

What is tension?

Answer 3

Tension is stress in which the particles of the member tend to pull a part under load.

Question 4

What is compression?

Answer 4

Compression is stress in which the particles of the member are pushed together and the member tends to shorten.

Question 5

What is the deformation of a material caused by external forces?

Answer 5

Strain (e)

strain (e) = total strain e / original length L

Question 6

What is shear?

Answer 6

Shear is stress in which the particles of a member slide past one another.

Question 7

What is Hooke’s law?

Answer 7

As a force is applied to a material, the deformation (strain) is directly proportional to the stress, up to a certain point.

Question 8

Ultimate Strength

Answer 8

The failing point of a given material.

Question 9

Yield Point

Answer 9

On a stress-strain graph, the point at which the material begins to deform with minimal increase in load (stress).

Question 10

Elastic Limit

Answer 10

On a stress-strain graph, the point at which the material will experience deformation faster. (Prior to to this point stress and strain are directly proportional.)

Question 11

Coefficient of Expansion

Answer 11

Thermal Stress

plastic, acrylic = 0.0000450
aluminum = 0.0000128 in/in-F
bronze = 0.0000101
structural steel = 0.0000065
concrete = 0.0000055
glass = 0.0000051
marble = 0.0000045
brick = 0.0000034

Question 12

Question: What is the applied force called in the following diagram?
→ ▯ ←

A) Shear
B) Compression
C) Torsion
D) Traction

Answer 12

B) Compression

Question 13

Newton’s 3rd law

Answer 13

For every force acting on a body (building) there is an equal force of opposite magnitude.

Question 14

List & define the 3 types of forces which may impact a structural body.

Answer 14

1 - COLLINEAR = along the same line of action *sum of vectors = magnitude along same line of action

2 - CONCURRENT = vectors that intersect at one point *sum of vectors with parallelogram polygon method

3 - NON-CONCURRENT = moment or rotation forces *sum of vectors = moment arm = F X d

Question 15

Shear & moment forces are best resisted with which construction types?

Answer 15

• RIGID CONNECTIONS (Least efficient, only good for small buildings)
• SHEAR PLANES
• BRACING

Question 16

2 types of loads

Answer 16

Static & dynamic

Question 17

2 types of static loads

Answer 17

Dead & Live

Question 18

4 types of live loads

Answer 18

1 - Occupant & moveable furniture / equipment

2 - Snow

3 - Rain

4 - Impact (kinetic loads of short duration - cosidered static by Code *amplify load to compensate for its dynamic nature)

Question 19

2 Common types of dynamic loads

Answer 19

Wind & seismic

Question 20

• Name 3 criteria governing the choice and use of a construction material.
• How should these criteria be for a material to be the most advantageous?

Answer 20

1. Resistance
2. Elasticity
3. Rigidity
   - The most beneficial materials of construction provide optimal elasticity and rigidity.

Question 21

Elasticity

Answer 21

• Ability of a material to deform under stress - bending, elongation or compression - and to return to its original shape when the stress is removed.
• Any material has a yield point beyond which it breaks or permanently deforms.

Question 22

Explain: ductile material vs brittle material

Answer 22

Ductile Material: Undergoes plastic deformation before breaking.

Brittle or fragile material: weak elastic limit and, without noticeable visible deformation, breaks under a load.

• Less resistant than ductile materials, brittle materials are not very suitable for the construction of buildings.

Question 23

Rigidity

Why is it important?

Answer 23

Measurement of the compressive or tensile force that must be exerted on a material for it to reach its elastic limit.

The stiffness / rigidity of a material and the stiffness of its cross-section are very important when it comes to the relationship between span and deflection under load.

Question 24

The dimensional stability of a material determines what?

Answer 24

The degree of dimensional stability of a material subjected to variations in temperature and humidity determines how it will be shaped and joined to other materials.

Question 25

3 types of structural systems & materials typically used for each

Answer 25

1 - LINEAR - columns & beams (steel/timber/concrete beams)

2 - PLANAR - walls & slabs (light wood/steel framing/masonry/concrete walls & slabs)

3 - COMPOSITE - columns/walls & beams/slabs

Question 26

3 main types of shear strength in high rise construction

Answer 26

1 - CONVENTIONAL - shear walls/bracing & or rigid frames

2 - CORE - vertical circulation key to lateral strength

3 - TUBE - lateral bracing along perimeter

Question 27

Best construction type for tall buildings in seismic zones

Answer 27

STEEL = DUCTILE & LIGHT

NOT CONCRETE = HEAVY & BRITTLE

Question 28

2 types of dampening

Answer 28

1 - TUNED MASS DAMPER - heavy mass on rollers towards the top of a tall building

2 - BASE ISOLATION - isolate the base from the ground so building can ‘float’ - prevents resonance

Question 29

Effective structural building materials comprise of

Answer 29

• Stiffness w Elasticity
• Resist Dimensional Instability due to Humidity & Temp.

Question 30

Qualities of wood as a structural material

Answer 30

• small • renewable • flexible
• light • exposed timbed

* GOOD IN COMPRESSION & TENSION

Question 31

Qualities of concrete as a structural material

Answer 31

• Freedom of form • Naturally fire protected
• Exposed structure • Inexpensive

* GOOD IN COMPRESSION - MUST BE PAIRED WITH STEEL REINFORCING FOR TENSION

Question 32

Qualities of steel as a structural material

Answer 32

• Repetitious modular • Long spans
• Light • Stiff & elastic

Question 33

Describe the typical assembly for a concrete slab

Answer 33

TOP

1. 100min slab thickness
2. welded wire fabric reinforcement midway
   
   • controls thermal stress: shrinking /cracking
   • grid of bars needed for heavy floor loads
3. 6 mil poly
4. 50mm sand
   
   • soak up water during curing
5. 100mm min base course of gravel/crushed stone
6. stable uniformly dense soil
   
   • prevents capillary rise of groundwater

Question 34

What are the 3 main concrete joints?

Answer 34

1. Isolation (aka expansion)
   
   • allows MVMT btwn concrete slab + adj. columns walls
2. Construction (also serve as control/isolation)
   
   • allows a place for construction to stop and start again @ later time
   • keyed or doweled
3. Control
   
   • ​​creates lines of weakness so cracking from tensile stress occurs along predetermined lines

Question 35

Describe the typical spacing of control joints, and 3 common types.

Answer 35

typ. spaced 4500-6100(15’-20’) or where required:

• irregular slab shape
• openings

1. Sawn Joint
2. Premolded or metal strip inserted into concrete
3. Keyed Joint
   
   • prevent bond by applying metal or plastic joint material or applying curing agent to one side

Question 36

Modulus of Elasticity

Answer 36

A stress to strain ratio of a given material. €

Question 37

e = PL/AE

Answer 37

Total strain (deformation) of a material under a given load.

A = total area
P = total force
L = original length
e = total strain

Question 38

Moment

Answer 38

The tendency of a force to cause rotation about a point.