Ch 11-12

Question 2

The difference between type I and type II construction is

Answer 2

The level of fire resistance or fire rating assigned to the structural frame, walls, floor, and roof.

Type II has little or no fire resistance for a structural members

Question 3

Allowable area and height differs between noncombustible and fire resistive construction. This is:

Answer 3

Noncombustible buildings are usually 1-3 stories and height, with a maximum of 12.

Fire resistance construction is unlimited height

Question 4

Type II construction is usually majority steel construction. The use of concrete is typically limited to:

Answer 4

Exterior walls and shaft enclosures.

Question 5

All other things equal, fire resistance is a function of mass.

Specifications of the strength of steel include:

Answer 5

Modus of elasticity is about 29 million psi
Compressive strength is equal to its tensile strength
Shear strength is about 3/4 of its tensile strength

Question 6

When triaging the heat evolving from a fire, the priority listed should be:

Answer 6

Priority 1 – heat being absorbed by the contents or structural elements. Cool or remove it.

Priority 2 – heat being evolved from contents that are burning. Wet it down.

Priority 3 – heat leaving the structure – let it go.

Question 7

Definitions and abbreviations of steel construction members:

Answer 7

Angle – “L”, L shaped
Bar – plate < 6”
Channel – “C”, U-shaped cross-section
Plate – flat steel
Purlin – beam at right angle to trusses or rafters
Tube – can be a cylinder, square, or rectangle. Usually used for a column.
Castellated beam- “CB”, 2 T’s welded together at the web
I- beam - “S”
Wide flange beam - “WF”. Could be a beam or a column

Question 8

Steel structural members may have abbreviations and a set of numbers in the blueprint. This is designated the size, and weight per foot in pounds. An example is W12x96 =

Answer 8

W 12x96 - this is a wide flange beam or column that is 12 inches deep and weighs 96 pounds per linear foot

Question 9

Specifications for steel angles, referred to the nominal depths of the two legs and the thickness. For example L 5x 3x 0.25

Answer 9

This is a an angle with a 3 inch leg, a 5 inch leg, and the legs are a quarter inch thick.

Question 10

A three dimensional truss is also known as a

Answer 10

Space frame.

Space frames provide huge clear spans in modern buildings 

Question 11

A rigid frame is similar to an arch and is used to achieve wide clear spans.
Rigid frames are sometimes tied together under the floor. Additionally, frames, columns, and rafters are:

Answer 11

The columns are narrow at the base and wider at the top
The rafters are narrow at the ridge and wider at the column.
They are originally connected
Richard frames can span up to about 100 feet. 

Question 12

In a true trussed arch, both the top and bottom cords are:

Answer 12

Both under compression. This is unique as the arch is a complete compression structure.

Question 13

Cement asbestos board is non-combustible and has been used for friable construction. This is:

Answer 13

Friable construction is used were an explosion is a possibility. It will break away readily and relieve the pressure.

Question 14

Exterior walls of steel frame buildings consist of a variety of wall types. Most likely curtain walls.
Some common materials are:

Answer 14

Cement, asbestos board
Glass fiber reinforced plastic
Aluminum
Precast prestressed concrete panels
Masonary walls – most common walls for unprotected steel frame buildings
Galvanized steel walls – asphalt asbestos protected metal AAPM
Metal panel – sandwich with thermal insulation
Light gauge steel frame wall – lightweight galvanized, steel studs

Question 15

The difference between pinned connections and plastic design is

Answer 15

With pinned connections, loads are delivered to the nearest columns.

In plastic design, connections are built to transfer loads beyond the columns. Similar to monolithic construction and concrete. These are rigid connections.
This also means that the material used may be lighter and have less mass and less fire resistance.

Question 16

Specific steel elongation rates per rise in temperature and failure temperatures are:

Answer 16

.06 - .07% in length per 100°F rise and temperature.
This translates to 9.5” per 100 feet at 1000°F
Above 1000°F steel softens depending on the load.
Structural steel fails at >1300°F

Question 17

In reference to steel trusses and beams, it is better to have a fire that:

Answer 17

A fire that is hotter, faster, and reaches failure temperature more rapidly.

Question 18

The term “ one high story” is used to designate buildings with:

Answer 18

Greater than usual height from floor to ceiling. For example, one equals five describes a building that is one story, but equal to five ordinary stories.

Question 19

In excavation bracing, it is necessary to shore up the excavation. This is usually done with:

Answer 19

Rows of soldier beams driven into the ground, tied together with horizontal walers, and held up by diagonal rakers.

The columns are allowed to be loaded twice to normal permitted load.

Tiebacks may be used as cold drawn, steel inserted into the rock and anchored with epoxy. (800°F failure).

Question 20

And protected non-combustible buildings, the word protection in codes may be confused with sprinkler protection. This actually refers to:

Answer 20

Physical protection of the steel with gypsum board, spray on fireproofing, or other factors of passive, protect protection.

Question 21

In regards to the lack of fire protection for unprotected steel, the book describes three classes of calculated risks:

Answer 21

Financial or economic - in case of fire, let it go

Engineering - this calculation is adequate

Forget it - no calculation is any better than the information used in it

Question 22

In regards to steel construction, the height of the steel above the floor level may be given an exemption. This is especially true in:

Answer 22

Atria roof over 55 feet.

Building codes may include 20 to 30 feet above the floor, not requiring protection.

Question 23

When insulation has absorb moisture, it makes it

Answer 23

Useless as insulation

Question 24

Metal deck roof consist of metal sheets, crimp together that are not gas tight. Laid onto steel bar joists. Low density fiber board insulation. Adhesive such as bituminous asphalt coating, bitumen layers, roofing felt, and hot tar.

These are known as:

Answer 24

Built up roofs.

They may also have fiberglass sheets or concrete laid on corrugated metal.

Modified bitumen roofs are similar, but use a propane torch to liquefy the adhesive.

Question 25

Increasing in popularity, a rubber roof has been used recently. This is known as.

Answer 25

EPDM, or Ethlene propylene diene monomer.

Question 26

A term for roofing that meets a testing lab standards, such as UL, for roofing resistant to the propagation of fire by flying brands

Answer 26

An approved roof

Question 27

As a result of the crimping in the metal decking, when the heat reaches 800°F, for 5 minutes, this starts the process to liquidy and vaporize the bituminous layers. This is a hazard because:

Answer 27

The heated gases cannot escape through the roofing layers, so they begin to burn downward through the joints, causing heat, thick black smoke, and fire under the roof inside the building. This is self sustaining and independent from the original fire.

Question 28

A factory mutual class 1roof, or UL classified roof is one that:

Answer 28

Will not provide self sustained combustion. A class one roof is not satisfactory if it contains any combustibles

Question 29

A fire involving a metal deck roof can only be controlled by:

Answer 29

Continuous application of water to the underside of the roof, cooling the steel and preventing tar from generating gas.

Question 30

Steel structures can be divided into four types, based on methods of protections:

Answer 30

Unprotected Dynamically protected Passively protected Passive/dynamic combination protection

Question 31

When applying water to unprotected steel in a fire, use the following recommendations:

Answer 31

Cool all the steel within reach of the hose streams Pay special attention to columns Keep the fire stream moving Use smoothbore, solid streams. Converting water to steam with a fog nozzle is not the best use of water. 

Question 32

Dynamic fire protection is generally accomplished with:

Answer 32

Various types of automatic sprinkler systems.

Question 33

Passive fire protection is provided by protecting steel in one of a couple of ways. Included.

Answer 33

Sprayed on fire protection Membrane fire protection 

Question 35

When looking at building and fire Code variances, there are no permit waivers for requirements. There are however:

Answer 35

Allowable permits for the use of alternative equivalent methods. All modifications should be fully documented and meet the intent of the code.

Question 36

The radiant energy of a fire is proportional to the fourth power of the absolute temperature. An example of a 2000°F absolute fire is:

Answer 36

A 2000°F fire of 20 minutes duration would have a radiant energy potential 16 times that 1000°F on fire of the same duration. Double the temperature and the radiant energy is to the fourth power.

Question 37

When applying water to hot steel, the water will

Answer 37

Either reverse the steel to its original dimensions, or freeze it in position.

Question 38

Steel Firecakes on older buildings should be maintained and certified every:

Answer 38

Every five years by a structural engineer. 

Question 39

In the case of a metal deck built up roof, any fire on the top of the roof is unimportant. Focus on:

Answer 39

Cooling the underside of the roof with large caliber hose streams, or ground monitors 

Question 41

Options for the building designer to deal with the characteristic of steel as its related to fire risk:

Answer 41

Ignore the problem Rely on inadequately enforced codes Take a calculated risk Fireproof or insulate the steel Protect the steel with sprinklers Protect the steel with a water cooling system Locate the steel out of the range of fire

Question 42

Concrete is a cement material produced by a chemical reaction of Portland cement (limestone) and water and aggregates. Concrete set quickly, but continues to cure indefinitely. Specifications are:

Answer 42

Concrete specifications set a date by which concrete must reach its required compressive strength. I.e. 28 day concrete.

Question 43

Heat of hydration refers to:

Answer 43

When concrete cures it generates heat of hydration. Concrete must also be protected from freezing. Low temperatures retard the curing of concrete.

Question 44

There are two basic types of concrete construction:

Answer 44

Cast in place concrete – post-tensioned concrete Precast concrete – pretensioned concrete Both include plain concrete and reinforced concrete

Question 45

Composite and combination columns use:

Answer 45

Steel and concrete combined into one unit.

Question 46

Composite construction refers to the type of construction. This is different than composite structural elements. Composite construction describes:

Answer 46

Buildings in which different loadbearing materials are used in different areas. I.e. columns made of concrete and other columns made of steel. Or lighter construction over heavier construction.

Question 47

Drop panels are

Answer 47

A thicker section of concrete floor near columns to prevent the floor from shearing off of the column

Question 48

Temperature rods are:

Answer 48

Thin rod installed near the surface of concrete at right angles to the main reinforcing rods to help the concrete resistance cracking due to temperature changes.

Question 49

A short concrete column with a large cross-section in proportion to its length is known as

Answer 49

A pier either plain concrete or reinforced concrete 

Question 50

A new replacement for steel reinforcing rods that do not corrode are:

Answer 50

Glass fiber, polymer, reinforcing rods. Twice the tensile strength of steel.

Question 51

In reference to concrete beams, the reinforcing rods are placed based on:

Answer 51

The use of the beam. A normally loaded bean with tension at the bottom would have the reinforcing rod in the bottom. I can’t live beam with tension in the top would have the reinforcing rods in the top of the beam.

Question 52

Vertical reinforcing bars in concrete beams designed to prevent cracking under stress are called

Answer 52

Stirrups

Question 53

The difference in the compressive strength of steel versus concrete

Answer 53

For any unit area, steel has 15 times the compressive strength of concrete.

Question 54

Autoclaved aerated concrete AAC, is a very lightweight concrete, about 1/4 the weight of traditional concrete. This is made by:

Answer 54

Adding aluminum powder to the concrete mix. The aluminum powder reacts with the lime, creating tiny air cells. Once the concrete has said, it is placed in an autoclave or kiln under high pressure 8 inch thick block walls have a 4- hour rating

Question 55

Concrete floors include some of the following:

Answer 55

Continuous T-beams Waffle concrete – two way structural system Left in place forms – concrete on corrugated steel Lightweight concrete topping over wood floors – 1 hour rating

Question 56

There are two methods of prestressing concrete:

Answer 56

Pre-tensioning - perform at the concrete plant and the forms Post-tensioning - performed at the job site. Tensioned after the concrete is poured and set. Major advantage of post tensioning is that floors can be thinner.

Question 57

In buildings with ordinary, loadbearing, mason walls, there’s an economic limit to the height due to the increase in thickness. The limit is generally about:

Answer 57

About 6 stories, but may be is much as 16 stories with loadbearing bricks Recent developments made it possible to build buildings 20 or more stories high with 12 inch thick walls

Question 58

One place where reinforced masonry is unsuitable is in multistory buildings with:

Answer 58

Where large clear spans of open areas are required

Question 59

Regarding lawsuits and litigation, the book is clear that blame in the finger pointing may happen. This is based on the theory that:

Answer 59

Collapses do not just happen, they are caused. Be wary of individuals wishing to hide evidence by knocking down the rest of the building.

Question 60

Definition – the temporary structure erected to support concrete work in the course of construction. It is composed of Shores, formwork, and lateral bracing.

Answer 60

Falsework. Concrete formwork can be up to 60% of the cost of the concrete structure. Formwork is just a mold for concrete, false work is all of the support structure for setting concrete. Including vertically.

Question 61

Potential issues with formwork when pouring concrete and columns or other vertical members

Answer 61

Head pressure can be up to 150 pounds per square foot for each foot of height Concrete port of 50°F will develop 1/3 more pressure than a 70°F Pressure is reduced as the concrete sets due to internal friction. Builders must avoid an overpour.

Question 62

In formwork, when concrete is poured on the ground, the planks on which the shores rest are called:

Answer 62

Mudsills.

Question 63

In post tensioning concrete, the tendons are contained in a sheath to prevent bonding. Hydraulic jacks are used to jack the cable after concrete reaches a designated fraction of its ultimate strength. For this reason,

Answer 63

The shear resistance of posttensioned slabs is poor

Question 64

Precast concrete buildings under construction are unstable until all connections are completed. Temporary bracing, such as tormentors are used. Precast walls are held together by

Answer 64

Either pinned connections with bolted or welded joints, or monolithic with wet joints.

Question 65

In lift slab construction, the ground floor slab, and subsequent floor floors are poured, and then:

Answer 65

Each floor is raised up on columns by hydraulic jacks placed to the top of the columns.

Question 66

Regarding fire potential in concrete construction, many times this is due to

Answer 66

Construction workers using scrap wood, kerosene heaters, or LPG heaters to stay warm. LPG is the most dangerous and most common heating method

Question 67

Protected steel is a term that references fireproofing. Although there’s no things truly fireproof, this actually means that:

Answer 67

The steel is insulated or weather protected.

Question 68

Steel fireproofing or protecting is classified as individual or membrane. Examples are.

Answer 68

Encasement – steel encased in concrete, terra-cotta, metal lathe and plaster, brick, or gypsum Membrane – includes intumescent coatings, and asbestos fiber historically Used for assemblies, not individual members. 

Question 69

Fire rated assemblies are listed in fire codes. These are given a rating in hours based on the assembly and all the members attached together. The important thing to remember about fire rated is.

Answer 69

No part of a listed fire resistance system can be rated or stand on its own. The value of listing materials is contingent upon field assembly being accomplished, exactly as performed in the laboratory.

Question 70

A more common encasement method for columns today is the use of

Answer 70

Gypsum board A 3- hour rated assembly in closing a steel column would use 3 layers of 5/8 inch type X gypsum board. 

Question 71

Some of the problems with sprayed on fireproofing is that

Answer 71

It must be applied at the specified thickness in density Adhesion could be a problem with bare steel Sprayed on material is easily knocked off by workers or vehicles

Question 72

One of the fire protection advantages to concrete construction is

Answer 72

It does not have inherent void spaces Suspended ceilings are the exception, that may cause concealed combustible void spaces

Question 73

Penetrations  are drilled to draw utility services up to a floor from the void below are known as

Answer 73

Poke throughs

Question 74

Exterior insulation finishing systems EIFS, give a building appearance of a sand finished concrete. Many times these are the result of.

Answer 74

Energy conservation with lightweight and cheaper materials

Question 75

Concrete trusses are not common, but huge ones can be seen at airport. Such as:

Answer 75

American Airlines at DFW airport with a 280 foot clear span

Question 76

Any failure of the bond between the two materials in reinforced composite concrete means

Answer 76

The composite has failed, no longer has the designed intended strength, and is now only dangerous dead weight

Question 78

In fire, normal strength concrete loses about 25% of its compressive strength at what temperature?

Answer 78

About 575°F. High strength, concrete loses more strength at the same temperature range

Question 79

In buildings under construction, a risk benefit analysis is important. Our mission to protect Property does not quite extend to.

Answer 79

Construction projects. The property value has not been established yet. There’s no point in risking lives of fire personnel in a concrete building under construction. It will all be torn out anyway. 

Question 80

There are two basic types of fire resistant construction

Answer 80

Reinforced concrete buildings and structural steel buildings. Both are designed to resist fire and collapse. Sometimes the best tactic is to let the fire burn itself out and protect the exposure floors