Structures

Question 1

Modulus of Elasticity

Answer 1

Property of material itself that describes it’s stiffness relative to strain

Question 2

How does beam depth and girder dpeth generally relate to beam span? How does the width relate to the depth?

Answer 2

Beam depth is about 1/20 of the span.
Span = 60'  Depth = 3'
Girder depth is about 1/15 of the span
Width is 1/3 of its depth
Depth = 3' Width = 1'

Question 3

Bolt connections

Answer 3

High strength bolts:

1. Bearing-type holds it in shear
2. Slip critical is super tightened and operates in tension

Question 4

Shear connection

Answer 4

Resists gravity forces but transfers shear forces. Only bolted on web but not flanges. If there’s bending in the beam, the columns don’t bend (but lateral forces will cause it to sway).

Question 5

Moment connection

Answer 5

Resists gravity and shear forces. Bolted on web and flange. If there’s bending in the beam, there’s bending in the columns.
Fully restrained = more rigid, negligible rotation between connected members
Partially restrained = transfers moment with some rotation between connected members

Question 6

Braced frame

Answer 6

Uses shear connections for most and one or more bays with diagonal bracing to resist lateral forces. More cost effective than moment frame.
Eccentrically braced frame used in seismic areas (less likely to buckle)

Question 7

Shear wall

Answer 7

Resists lateral/shear forces. Need one in X, Y and Z directions.

Question 8

Total loaded width of column

Answer 8

Tributary area it is supporting x number of floors it is supporting

Question 9

Staggered truss system

Answer 9

Every other floor is a truss and spans the full width of the building. Allows column-free floor plates. MInimizes floor to floor height.

Question 10

What provides more resistance to lateral forces? Rigid core or rigid perimeter?

Answer 10

Rigid perimeter is more stiff because it acts across larger area

Question 11

Composite steel and concrete columns/beams pros and cons

Answer 11

Encase WF in concrete or fill HSS tube with concrete
Pro: reduce amount of steel used by half
Cons: Too heavy for beams

Question 12

Shear stud

Answer 12

Steel pins that attach poured concrete floor slab to top of steel beam with welded connection to resist shear forces

Question 13

Girts

Answer 13

Metal channels that run horizontally between columns (in z channel family). Metal wall panels attach to them.

Question 14

How tall can an unprotected steel structure be built?

Answer 14

5 stories

Question 15

Which steel members do not have to be fire proofed?

Answer 15

Members that only resist lateral forces like cross bracing

Question 16

What adds embodied energy to a material?

Answer 16

Higher finish
Heaver material
More petroleum used
More glue used
More heat used in production
More mining or refining
Less recycled content
US: 90% steel recycled, 30% aluminum recycled

Question 17

Which open web steel joist type spans the longest?

Answer 17

DLH - 150’
LH - 96’
K - 60’ (most common)

Question 18

List metals from most anode to most cathode that contribute to galvanic action (corrosion)

Answer 18

1. alum
2. zinc
3. steel
4. iron
5. stainless steel - active
6. tin
7. lead
8. copper
9. stainless steel - passive

The further materials are from each other, the more current that will flow between them and speed corrosion (electrolysis). Best choice is using the same metal for everything touching but also be careful with other alkalyine materials like mortar and concrete. Separate materials with a nonreactive material such a rubber, neoprene or plastic.

Question 19

K values for likelihood of column buckling

Answer 19

Different connections have different values (found in table). Multiply length of column x k to determine how it will behave under buckling. Higher value means higher likelihood of buckling.
Ex. 10’ column with k value of 0.5 will behave more like a column 5’ high.
Theoretical k value is used for steel (consistent)
Recommended k value is used for wood (has variation)

Question 20

Where are rotation fixed and translation free connections used?

Answer 20

In seismic conditions (allowed to pivot side to side)

Question 21

What controls the beam size calculation the most?

Answer 21

Bending moment

Other: shear, deflection

Question 22

Relationship between column length and…

a. shear
b. moment
c. deflection

Answer 22

a. shear: L
b. moment: L^2
c. deflection: L^3
Ex. doubling the L means: Vx2, Mx4, Dx8

Question 23

Section modulus

Answer 23

A geometric property for a given cross-section used in the design of beams. Larger section modulus means less bending stress.
Fb = M/S
Fb: bending stress
M = bending moment
S = section modulus

Question 24

Soft story problem

Answer 24

When buildings are heavier on top than bottom in seismic zones.

Question 25

Where can you notch or put a hole in a wood beam or stud for mechanical ducts or pipes? What about studs?

Answer 25

- You can notch end up to 1/4 of depth - You can notch anywhere else 1/6 of depth and width of notch has to be less than 1/3 the depth of the beam - Cannot notch in middle 1/3 of beam - A hole can be put anywhere but diameter must be 1/3 of the depth max. and the hole needs to be at least 2" from edge of joist. If there is a second hold, it needs to be at least 2" away from first. - In studs, max diameter of hole is 40% of stud depth and no closer than 5/8" from edges. Notch cannot exceed 25% of stud depth. If pipe is bigger than 40%, you can get up to 60% if you double stud up.

Question 26

Direct tension indicator

Answer 26

Washer under bolt with bumps that get flattened out as you tighten the bolt to know if you tightened it enough.

Question 27

Types of buildings moment resisting frames are appropriate for

Answer 27

Low rise and high rise up to 30 stories. Higher than 30 should use x bracing.

Question 28

``` Wood member spans: Joists Solid beams Glulam beams Heavy trusses ```

Answer 28

Joists: 20' Solid beams: 30' Glulam beams: 100' Heavy trusses: 200'

Question 29

One way vs two way slab

Answer 29

Slab will behave like a one way slab if aspect ratio is more than 2. (long length / short length > 2)

Question 30

``` Steel member spans: Decking Lightweight joists Beams Open web joists Heavy trusses Space frame Suspension ```

Answer 30

``` Decking: 20' Lightweight joists: 30' Beams: 75' Open web joists: 150' Heavy trusses: 300' Space frame: 500' Suspension: 500+' ```

Question 31

``` Concrete span ranges One way Two way Waffle slab Beams Precast slabs Precast double tees Precast single tees ```

Answer 31

``` One way: 20' Two way: 40' Waffle slab: 55' Beams: 70' Precast slabs: 45' Precast double tees: 100' Precast single tees: 150' ```

Question 32

Structural systems recommended for a library

Answer 32

Reasons: heavy live loads of stacks, long spans Steel beams and girders Sitecast concrete beams and girders Sitecast one way or two way slab

Question 33

Structural systems recommended for a concert hall

Answer 33

Reasons: fire protection, long spans ``` Steel beams and girders Steel trusses Sitecast concrete beams and girders Concrete one way or two way slabs Waffle slab ```

Question 34

Structural systems recommended for tall buildings

Answer 34

Reasons: ``` Steel beams and girders Steel single story rigid frame Sitecast concrete beams and girders Two way flat plate slab Precast beams and girders Hollow core planks ```

Question 35

When to use a column and slab system

Answer 35

No beams means columns can be located more freely Possibly more economical due to simplicity and reduction in floor depths Most are sitecast concrete systems but can also be space frame systems

Question 36

Precast concrete

Answer 36

High early strength mix (type III) and steam curing allow shapes to cure quickly for faster production. Warehoused until they have passed 28 day cylinder test. Shapes: floor planks, beams, columns, wall panels and domes Conditions better controlled than site cast concrete.

Question 37

Slip joint at head of aluminum storefront purpose

Answer 37

Accommodate deflection of the structure above

Question 38

Types of attachments for securing precast panel to floor assembly

Answer 38

2 Points of Bearing: One rigid and one tie back which allows for both vertical and lateral movement

Question 39

Allowable stress ratings for lumber are based on what?

Answer 39

The wood species

Question 40

Depths of open web joists

Answer 40

K - 30" LH - 4'-0" DLH - 6'-0"

Question 41

Depth of concrete beam relative to span

Answer 41

1/16

Question 42

Semi-rigid connection

Answer 42

Beam or end plate welded all around. Limited moment to compensate for. No tab plates or shear bolts required.

Question 43

How to calculate snow load on a ridgebeam per lf

Answer 43

Snow load x 1/2 of total beam span

Question 44

``` Which beam is the heaviest? W 27 x 178, 20’ long W 24 x 104, 40’ long W 21 x 147, 30’ long W 18 x 119, 35’ long ```

Answer 44

``` Multiply weight per ft x length for each: W 27 x 178, 20’ long = 3,560 pounds W 24 x 104, 40’ long = 4,160‬ pounds W 21 x 147, 30’ long = 4,410 pounds W 18 x 119, 35’ long = 4,165 pounds ```