module1c SCT01c3&4r SM FEMA NATIONAL US&R RESPONSE SYSTEM STRUCTURAL COLLAPSE TECHNICIAN
FEMA NATIONAL US&R RESPONSE SYSTEM
STRUCTURAL COLLAPSE TECHNICIAN 02-00
MODULE 1C STRUCTURAL ENGINEERING SYSTEMS
PART 3 - HAZARD IDENTIFICATION & BUILDING MONITORING
OBJECTIVES
TERMINAL OBJECTIVES
The objectives of this unit are to familiarize the student with the • The Student shall understand the most
common signs of distress exhibited by
most common signs of distress exhibited by damaged structures. damaged structures.
We have previously discussed Material Behavior and Collapse • The Student shall understand to the most
Patterns, and will now apply this knowledge to the Disaster Site. common Hazards found in damaged
structures, and methods that have been used
to used to Mitigate them
n We will first discuss how Concrete and Masonry crack, and how
these cracks can be “READ” to predict future performance of
these structures.
ENABLING OBJECTIVES
n We will then identify the most common Hazardous Conditions
Understand the importance of the various
that will occur in the four types of buildings that we have •
types of Cracks in Concrete and Masonry
previously identified. Structures.
• Understand the common Hazardous
Conditions that occur in Light Frame, Heavy
n Finally we will discuss the various tools and methods that are Wall, Heavy Floor and Precast Buildings
• Discuss the common methods and
currently available to Monitor Buildings equipment used to Mitigate Structure
Hazards
CRACKS IN REINFORCED CONCRETE & MASONRY
A favorite statement in building design and construction is; "If its
not cracked, its not concrete," since cracks must form in concrete We need to apply our
for the reinforcing steel to be stressed in tension. Most normal con- knowledge regarding
crete develops cracks that are narrow (hairline) as a result of Material Behavior & Collapse
shrinkage, temperature change, and predictable structural Patterns to Disaster Site
behavior.
SHRINKAGE CRACKS
n Usually occur in slabs, beams, walls, and even in columns Cracks in Reinforced Concrete &
within 60 days of the pour, after the concrete is allowed to dry Reinforced Masonry
out. • shrinkage cracks
• temperature cracks
• tension cracks
n Diagonal cracks will originate from most re-entrant corners in
• diagonal tension cracks in beams
slabs and walls i.e. window, door, and floor openings. • diagonal tension cracks in walls
If it’s not Cracked it’s not Concrete
n Straight cracks (more or less) occur often at five to twenty feet
on center in long wall and/or floor surfaces, depending on the
amount of reinforcing steel, numbers of pour joints, and curing
conditions.
n The reinforcing steel within the structure is intended to hold the
structure together as it shrinks, and keep these cracks small.
SM 1c, 3&4 1
1
,module1c SCT01c3&4r SM FEMA NATIONAL US&R RESPONSE SYSTEM STRUCTURAL COLLAPSE TECHNICIAN
FEMA NATIONAL US&R RESPONSE SYSTEM
STRUCTURAL COLLAPSE TECHNICIAN 02-00
MODULE 1C STRUCTURAL ENGINEERING SYSTEMS
PART 3 - HAZARD IDENTIFICATION & BUILDING MONITORING
TEMPERATURE CRACKS
Shrinkage & Temperature
Cracks
n Occur in roughly the same pattern as shrinkage cracks, and are • Occur in slabs, walls, beams, & columns.
difficult to differentiate from them. • Diagonal cracks originate at re-entrant
corners in slabs & walls (openings)
• Transverse (more or less straight) cracks
n When the temperature of a concrete structure is decreased, it occur at 5 to 20 ft apart in long slabs &
walls
must shorten (shrink) and, therefore, it cracks, and the • Nominal rebar normally keep cracks small
reinforcing steel attempts to hold it together.
n Reinforced concrete structures will, obviously, have more
observable temperature/ shrinkage cracking when subjected to
the winter cold.
TENSION CRACKS
n These most often occur in concrete slabs and beams when
bending caused, tension forces stretch the reinforcing steel
n Cracks must form in the concrete in order to transfer the force to
the steel, but the cracks normally are quite numerous, small and
undetectable (except to the trained eye).
n They form, perpendicular to the long axis of the member, and
as long as they remain hairlike, the structure is behaving
normally.
DIAGONAL TENSION CRACKS
n Occur in high shear stress zones of beams and girders in a
typical pattern (HAZ-DTEN) under normal vertical load
conditions.
n In shearwalls, large diagonal tension cracks will form when the
walls are heavily loaded by severe earthquake shaking
(HAZ-DTEN).
n Earthquakes will normally cause a diagonal crack in each
direction (Cross Cracking) in the highly stressed areas of
shearwalls (i.e., between window openings, over stacked door
openings) since the shear force reverses causing diagonal
tension cracking in each direction.
SM 1c, 3&4 2
2
,module1c SCT01c3&4r SM FEMA NATIONAL US&R RESPONSE SYSTEM STRUCTURAL COLLAPSE TECHNICIAN
FEMA NATIONAL US&R RESPONSE SYSTEM
STRUCTURAL COLLAPSE TECHNICIAN 02-00
MODULE 1C STRUCTURAL ENGINEERING SYSTEMS
PART 3 - HAZARD IDENTIFICATION & BUILDING MONITORING
DIAGONAL TENSION CRACKS (continued)
SM 1c, 3&4 3
3
, module1c SCT01c3&4r SM FEMA NATIONAL US&R RESPONSE SYSTEM STRUCTURAL COLLAPSE TECHNICIAN
FEMA NATIONAL US&R RESPONSE SYSTEM
STRUCTURAL COLLAPSE TECHNICIAN 02-00
MODULE 1C STRUCTURAL ENGINEERING SYSTEMS
PART 3 - HAZARD IDENTIFICATION & BUILDING MONITORING
CRACKS IN REINFORCED CONCRETE WALLS
n The stability of concrete box-buildings will probably depend on
the post-cracked strength of the shear walls. Even with
unsightly diagonal cracking, a shearwall may still have signifi-
cant strength (HAZ-CK).
n The clamping action of the gravity loads, as well as the vertical
rebar will tend to hold the irregular surface of the cracks
together, preventing the opposing surface from sliding. In
addition the rebar that cross the crack can also act as dowels.
n Both these resistive actions are lessened when there is enough
shaking, or continued reshaking due to aftershocks that the
crack widens, concrete chunks fall out, and the rebar can be
seen in an offset curved condition. In this later degraded
condition a shearwall has become unreliable and must be
evaluated accordingly.
CRACKS IN URM WALLS & UR CONCRETE WALLS
n Shrinkage, temperature, and diagonal tension/shearwall cracks
also occur in URM and UR concrete walls. In these walls,
however, cracking indicates a significantly degraded structure.
n Diagonal tension cracks form in these walls between openings,
as they do in reinforced concrete walls due to earthquake
shaking. In addition cracks are often created at wall corners,
with the bottom of the crack at the corner and the top extending
up to the roof. This is caused by the action of the disconnected
roof diaphragm pushing against the corner, attempting to push it
out. URM diagonal cracks tend to follow a stair step pattern
(HAZ-CK). That is, the crack follows the weaker mortar, rather
than going through the bricks. This results in cracked surfaces
that are smoother than those in reinforced concrete.
n Masonry walls with significant diagonal tension cracks must be
considered to be capable of a sudden, brittle failure. There is
some clamping force on the horizontal steps of the cracks due
to the gravity force, but no vertical bars to add clamping or
dowel action. The greater smoothness of the joints also
reduces the friction that could be developed by the clamping of
the vertical force.
n Unreinforced Concrete Walls also perform poorly during
quakes. They tend to break apart in pieces, defined by
whatever crack pattern existed prior and/or by the original pour
joints.
SM 1c, 3&4 4
4
FEMA NATIONAL US&R RESPONSE SYSTEM
STRUCTURAL COLLAPSE TECHNICIAN 02-00
MODULE 1C STRUCTURAL ENGINEERING SYSTEMS
PART 3 - HAZARD IDENTIFICATION & BUILDING MONITORING
OBJECTIVES
TERMINAL OBJECTIVES
The objectives of this unit are to familiarize the student with the • The Student shall understand the most
common signs of distress exhibited by
most common signs of distress exhibited by damaged structures. damaged structures.
We have previously discussed Material Behavior and Collapse • The Student shall understand to the most
Patterns, and will now apply this knowledge to the Disaster Site. common Hazards found in damaged
structures, and methods that have been used
to used to Mitigate them
n We will first discuss how Concrete and Masonry crack, and how
these cracks can be “READ” to predict future performance of
these structures.
ENABLING OBJECTIVES
n We will then identify the most common Hazardous Conditions
Understand the importance of the various
that will occur in the four types of buildings that we have •
types of Cracks in Concrete and Masonry
previously identified. Structures.
• Understand the common Hazardous
Conditions that occur in Light Frame, Heavy
n Finally we will discuss the various tools and methods that are Wall, Heavy Floor and Precast Buildings
• Discuss the common methods and
currently available to Monitor Buildings equipment used to Mitigate Structure
Hazards
CRACKS IN REINFORCED CONCRETE & MASONRY
A favorite statement in building design and construction is; "If its
not cracked, its not concrete," since cracks must form in concrete We need to apply our
for the reinforcing steel to be stressed in tension. Most normal con- knowledge regarding
crete develops cracks that are narrow (hairline) as a result of Material Behavior & Collapse
shrinkage, temperature change, and predictable structural Patterns to Disaster Site
behavior.
SHRINKAGE CRACKS
n Usually occur in slabs, beams, walls, and even in columns Cracks in Reinforced Concrete &
within 60 days of the pour, after the concrete is allowed to dry Reinforced Masonry
out. • shrinkage cracks
• temperature cracks
• tension cracks
n Diagonal cracks will originate from most re-entrant corners in
• diagonal tension cracks in beams
slabs and walls i.e. window, door, and floor openings. • diagonal tension cracks in walls
If it’s not Cracked it’s not Concrete
n Straight cracks (more or less) occur often at five to twenty feet
on center in long wall and/or floor surfaces, depending on the
amount of reinforcing steel, numbers of pour joints, and curing
conditions.
n The reinforcing steel within the structure is intended to hold the
structure together as it shrinks, and keep these cracks small.
SM 1c, 3&4 1
1
,module1c SCT01c3&4r SM FEMA NATIONAL US&R RESPONSE SYSTEM STRUCTURAL COLLAPSE TECHNICIAN
FEMA NATIONAL US&R RESPONSE SYSTEM
STRUCTURAL COLLAPSE TECHNICIAN 02-00
MODULE 1C STRUCTURAL ENGINEERING SYSTEMS
PART 3 - HAZARD IDENTIFICATION & BUILDING MONITORING
TEMPERATURE CRACKS
Shrinkage & Temperature
Cracks
n Occur in roughly the same pattern as shrinkage cracks, and are • Occur in slabs, walls, beams, & columns.
difficult to differentiate from them. • Diagonal cracks originate at re-entrant
corners in slabs & walls (openings)
• Transverse (more or less straight) cracks
n When the temperature of a concrete structure is decreased, it occur at 5 to 20 ft apart in long slabs &
walls
must shorten (shrink) and, therefore, it cracks, and the • Nominal rebar normally keep cracks small
reinforcing steel attempts to hold it together.
n Reinforced concrete structures will, obviously, have more
observable temperature/ shrinkage cracking when subjected to
the winter cold.
TENSION CRACKS
n These most often occur in concrete slabs and beams when
bending caused, tension forces stretch the reinforcing steel
n Cracks must form in the concrete in order to transfer the force to
the steel, but the cracks normally are quite numerous, small and
undetectable (except to the trained eye).
n They form, perpendicular to the long axis of the member, and
as long as they remain hairlike, the structure is behaving
normally.
DIAGONAL TENSION CRACKS
n Occur in high shear stress zones of beams and girders in a
typical pattern (HAZ-DTEN) under normal vertical load
conditions.
n In shearwalls, large diagonal tension cracks will form when the
walls are heavily loaded by severe earthquake shaking
(HAZ-DTEN).
n Earthquakes will normally cause a diagonal crack in each
direction (Cross Cracking) in the highly stressed areas of
shearwalls (i.e., between window openings, over stacked door
openings) since the shear force reverses causing diagonal
tension cracking in each direction.
SM 1c, 3&4 2
2
,module1c SCT01c3&4r SM FEMA NATIONAL US&R RESPONSE SYSTEM STRUCTURAL COLLAPSE TECHNICIAN
FEMA NATIONAL US&R RESPONSE SYSTEM
STRUCTURAL COLLAPSE TECHNICIAN 02-00
MODULE 1C STRUCTURAL ENGINEERING SYSTEMS
PART 3 - HAZARD IDENTIFICATION & BUILDING MONITORING
DIAGONAL TENSION CRACKS (continued)
SM 1c, 3&4 3
3
, module1c SCT01c3&4r SM FEMA NATIONAL US&R RESPONSE SYSTEM STRUCTURAL COLLAPSE TECHNICIAN
FEMA NATIONAL US&R RESPONSE SYSTEM
STRUCTURAL COLLAPSE TECHNICIAN 02-00
MODULE 1C STRUCTURAL ENGINEERING SYSTEMS
PART 3 - HAZARD IDENTIFICATION & BUILDING MONITORING
CRACKS IN REINFORCED CONCRETE WALLS
n The stability of concrete box-buildings will probably depend on
the post-cracked strength of the shear walls. Even with
unsightly diagonal cracking, a shearwall may still have signifi-
cant strength (HAZ-CK).
n The clamping action of the gravity loads, as well as the vertical
rebar will tend to hold the irregular surface of the cracks
together, preventing the opposing surface from sliding. In
addition the rebar that cross the crack can also act as dowels.
n Both these resistive actions are lessened when there is enough
shaking, or continued reshaking due to aftershocks that the
crack widens, concrete chunks fall out, and the rebar can be
seen in an offset curved condition. In this later degraded
condition a shearwall has become unreliable and must be
evaluated accordingly.
CRACKS IN URM WALLS & UR CONCRETE WALLS
n Shrinkage, temperature, and diagonal tension/shearwall cracks
also occur in URM and UR concrete walls. In these walls,
however, cracking indicates a significantly degraded structure.
n Diagonal tension cracks form in these walls between openings,
as they do in reinforced concrete walls due to earthquake
shaking. In addition cracks are often created at wall corners,
with the bottom of the crack at the corner and the top extending
up to the roof. This is caused by the action of the disconnected
roof diaphragm pushing against the corner, attempting to push it
out. URM diagonal cracks tend to follow a stair step pattern
(HAZ-CK). That is, the crack follows the weaker mortar, rather
than going through the bricks. This results in cracked surfaces
that are smoother than those in reinforced concrete.
n Masonry walls with significant diagonal tension cracks must be
considered to be capable of a sudden, brittle failure. There is
some clamping force on the horizontal steps of the cracks due
to the gravity force, but no vertical bars to add clamping or
dowel action. The greater smoothness of the joints also
reduces the friction that could be developed by the clamping of
the vertical force.
n Unreinforced Concrete Walls also perform poorly during
quakes. They tend to break apart in pieces, defined by
whatever crack pattern existed prior and/or by the original pour
joints.
SM 1c, 3&4 4
4
