EKU Chapter 10 Building Construction Related to Fire Service Questions see the slides and answer 10 questions. Building Construction Related to the Fire Se

EKU Chapter 10 Building Construction Related to Fire Service Questions see the slides and answer 10 questions. Building Construction Related to the Fire Service. Building Construction
Related to the Fire Service
Chapter 10 — Concrete
Construction
Components of Concrete
•
•
•
•
Portland cement
Course aggregates
Fine aggregates
Water
Courtesy of McKinney (TX) Fire Department
Building Construction
10–1
Curing
• Necessary to reach proper strength
• Requires correct hydration and
temperature control
• Improper curing affects finished surface
and strength
(Continued)
Building Construction
10–2
Curing
• Hydration
– Hardening of concrete
– Heat of hydration
• Keeping concrete moist during curing
– Sprinkling
– Ponding
– Covering with plastic film
– Sealing compounds
Building Construction
10–3
Temperature Control
• Ideal – 50° to 70°F (10°C to 21°C)
• Above 100°F (37°C) will not reach
proper strength
• Heat of hydration in massive structures
can adversely affect final strength
• Maintaining appropriate temperature
• Design strength reached after 28 days
Building Construction
10–4
Admixtures
• Chemicals added to concrete mixture to
produce type for specific purpose
• Concrete types
• Color can be added for aesthetic or
safety reasons
Building Construction
10–5
Reinforced Concrete
• Concrete is strong in compression but
weaker in tension
• Ultimate compressive strength can vary
• Must be reinforced where tensile forces
occur in structure
• Steel reinforcing bars placed within
concrete before it hardens
Building Construction
10–6
Ordinary Reinforcing
• Bars placed in formwork
and wet concrete placed
around bars
• Concrete adheres to
reinforcing bars because
of deformations on the
surface of the bars
(Continued)
Building Construction
10–7
Ordinary Reinforcing
• Forces within structural
components
• Concrete tee beams
• Function of reinforcing
steel in concrete
• Lateral reinforcing
provided around vertical
bars to prevent buckling
Building Construction
10–8
Courtesy of Ed Prendergast
Prestressing Reinforcing
• Compressive force
induced in concrete
before load is
applied
• Tightening
reinforcing steel
(Continued)
Building Construction
10–9
Prestressing Reinforcing
• Requires large loads be applied to
concrete along axis of beam
• Pretensioning – Cables
tensioned before
concrete is poured
• Posttensioning – Steel
not tensioned until after
concrete has hardened
Courtesy of McKinney (TX) Fire Department
Building Construction
10–10
(Continued)
Prestressing Reinforcing
• Forces produced in prestressing process
remain locked in steel for life of
assembly
• Reinforcing steel should not be cut
during fire fighting unless necessary to
rescue trapped victims
Building Construction
10–11
Cast-in-Place Concrete
• Placed in forms at building site as wet
mass and hardens in forms
• Permits designer to cast concrete in
wide variety of shapes
• Most is proportioned at bulk plants and
mixed in truck en route to job site
• Care needed in mixing, placing, and
(Continued)
curing
Building Construction
10–12
Cast-in-Place Concrete
Courtesy of McKinney (TX) Fire Department
Building Construction
10–13
Water-to-Cement Ratio
• Most important factor in determining
ultimate strength of concrete
• Presence of excess moisture produces
spalling when exposed to freezing
conditions and heat of a fire
Building Construction
10–14
Quality Control of Concrete
• Slump test
• Compression test
Building Construction
10–15
Flat-Slab Concrete Frames
• Consists of concrete slab supported by
concrete columns
• Shear stresses develop
where slab intersects
the supporting columns
Courtesy of McKinney (TX) Fire Department
Building Construction
10–16
Slab and Beam Framing
• Concrete slab supported by concrete
beams
• One-way reinforced slab; frame may also
have beams running in two directions
• Two-way slab used where spans are
short and floor loadings are high
• Highly susceptible to fire damage; in
need of fireproofing
Building Construction
10–17
Waffle Construction
• Waffle-like pattern
on bottom of
concrete slab
• Results from
placement of
square forms over
which wet
concrete is placed
Building Construction
10–18
Concrete Plus Structural Steel
• Concrete slab supported by structural
steel beams
• If intended for Type I fire-resistive
building, steel must have some form of
fireproofing
Building Construction
10–19
Precast Concrete
• Placed in forms and
cured at location other
than construction site
• Transported to job site
and hoisted into position
• Advantages
• Disadvantage
Courtesy of McKinney (TX) Fire Department
Courtesy of McKinney (TX) Fire Department
Building Construction
10–20
Tilt-Up Construction
Courtesy of Dave Combs
Courtesy of McKinney (TX) Fire Department
Building Construction
10–21
Precast Connections
• Precast elements
– Lighter than cast-in-place
components
– May result in loss of
continuity
– Connections between
components critical aspect
of structural engineering
Courtesy of McKinney (TX) Fire Department
(Continued)
Building Construction
10–22
Precast Connections
• Slabs rest on bearing wall or columns
• When beams supported by columns, may be
supported by:
– Corbels cast into columns
– Short steel beam cast into precast column
– Precast beams secured to column by steel
angles cast into columns or posttensioned cables
• Garages
Building Construction
10–23
Identification of
Concrete Systems
• Difficult to know if frame constructed
with ordinary or posttensioned
reinforcing
• May be impossible to distinguish castin-place and precast concrete after
building completed
• Some systems appear to be in concrete
when they are not
Building Construction
10–24
Fire Resistance
• Concrete fundamentally fire resistant
• Steel used in reinforced concrete not
fire resistive
• Prestressed concrete systems
somewhat more vulnerable to failure
than ordinary reinforced concrete
(Continued)
Building Construction
10–25
Fire Resistance
• Fire-resistance ratings
• Structural lightweight concrete
• Cast-in-place fundamentally greater
structural rigidity
• Incorporation of non-fire-resistive
supports will compromise fire resistance
of concrete assemblies
Building Construction
10–26
Spalling
• Expansion of excess moisture in
concrete when heated or frozen
• Weakens concrete structurally and
exposes reinforcing steel to fire
• Extent depends on several factors
• New concrete not completely cured
subject to more severe spalling when
exposed to fire
Building Construction
10–27
Heat Sink Effect
• Concrete absorbs heat when exposed to
fire
• Retains heat and releases it slowly
• Firefighters may experience gradual
release of heat from surrounding
concrete after fire is extinguished
• Concrete not hot enough to reignite
combustibles
Building Construction
10–28
Summary
• Concrete is a noncombustible material
that is strong in compression, but weak
in tension.
• Concrete structures are built from either
cast-in-place or precast concrete, with
cast-in-place structures having greater
inherent rigidity.
(Continued)
Building Construction
10–29
Summary
• Reinforced concrete structures generally
perform well under fire conditions, but
spalling can result in failure of
reinforcing bars and the assembly.
• The specific method of reinforcing
cannot be identified visually.
• Reinforcing bars should not be cut
unless necessary for rescue.
Building Construction
10–30
Review Questions
1. What is ordinary reinforcement of
concrete?
2. How is a slump test performed?
3. What is tilt-up construction?
4. How is the choice of material for a
curtain wall determined?
5. What is the heat sink effect?
Building Construction
10–31
QUESTION 1
Name four types of specialized concrete.
QUESTION 2
Concrete is made of several different materials. What is the material that is added to the concrete that creates
the adhesive and cohesive properties that help bond to the inert properties?
QUESTION 3
Steel reinforcing bars (rebar) can be added to concrete to give it tensile strength. Name two more materials
that the book discusses that can be added to concrete to give it tensile strength.
QUESTION 4
Pretensioned and posttensioned concrete are great structural advantages in building construction, however
on the fire ground they can offer a significant hazard. Discuss one of the dangers created by either pre or
posttensioned concrete.
QUESTION 5
Normal designed strength of concrete is reached after ____ days of curing.
QUESTION 6
Concrete hardening undergoes a chemical process that uses water and cement to form a microscopic gel that
bonds all the components in the concrete. This chemical process is known as_____________________.
QUESTION 7
Concrete reaches its highest strength by keeping the temperature between 50 and 70 degrees Fahrenheit (1021 Celsius). If concrete is cured at or above ______ temperature it will not reach its proper strength.
QUESTION 8
A slump test is a standardized test that uses a cone-shaped mold and is used to test the ________ of concrete.
QUESTION 9
Concrete structural components can have fire resistive ratings between 1-4 hours. Name three variables the
book discusses that contribute to the fire resistive rating.1._________________________________ ,
2. _____________________________, 3. ___________________________
QUESTION 10
Identification of concrete systems can be difficult to identify key components in the construction. Some of
the components can often include nonbearing walls and various construction materials that are based
solely on architectural basis like glass, aluminum, and EIFS. As a firefighter what are some of the best
ways to identify the key structural components of a building using concrete structural components?

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