PDD 01 Flashcards
What are four material
characteristics that should be
considered when selecting
exterior finishes for a
building?
Making sure the material is appropriately
used.
Material can withstand the elements (sun,
wind, rain, etc.)
How often does the material require
maintenance.
How well does the material perform for its
intended use and longevity.
How should the performance
of materials be considered
during the design phase?
Materials should be tested to assure they
will perform as expected and designed.
The life span of the material should be
evaluated to make sure it will withstand
normal wear and tear.
How does building orientation
effect natural daylighting?
Windows facing north will not get any
direct sunlight, whereas windows facing
south will receive a fair amount of sunlight
year round.
Describe the treatments for a
North-facing window vs. an
East-facing window.
North-facing windows: will not get any
direct light but will provide an even glow
from reflected light all day. In hot places
they have almost no heat gain. In cold
climates, a north window will be cold and
grey.
East-facing windows: will receive sunlight
in the morning and are opportunities to
start warming up the building at the
beginning of the day.
Describe the treatments for a
South-facing window vs. a
West-facing window.
South-facing windows: receive sunlight nearly
all day. In hot climates, use overhangs above
the windows to block the summer sun from
coming in. A 2 foot overhang will shade the
summer sun but allow the winter sun to come
in.
West-facing windows: receive hot afternoon
sun until sunset. The western sun is much
lower in the sky, so overhangs will not prevent
the heat from entering the building. Using
louvers will help control the amount of sun that
enters the building.
What is a free body diagram?
To analyze forces on and within
structures, we borrow a graphic technique
from physics called a free body diagram,
or FBD. An FBD is a representation of a
body and all forces and moments acting
on it. It does not include internal forces.
What structural connection
can resist either x or y forces,
but not moment?
Pinned connections
This type of structural
connection only resists forces
in the y direction.
Roller connections
Within any structural member
in bending, _____ is quantified
as the maximum translation
measured perpendicular to its
central axis.
deflection, In a beam, deflection is the
vertical distance that the beam sags at
midspan.
It’s usually expressed as a fraction of the
span. Often noted as the Greek letter delta
(Δ).
The formula for deflection of a
beam with a uniformly
distributed load is:
Δ = 5 wl4 / 384 EI
The fibers within a beam
develop an internal moment to
resist the moment caused by
deflection. This resisting
moment is called:
bending moment
The centroid of an area is
conceptually defined as:
The center of gravity of a mass
For simple geometric shapes, like circles
and rectangles, determining the centroid is
easy and simply corresponds to the
geometrical center. For many common
asymmetrical shapes, the centroid is
calculated.
A factor relating the shape of
a structural section and the
distribution of its material
relative to a chosen axis is
called:
A section’s moment of inertia, usually
denoted “I”.
The units of moment of inertia are, in4 or
inches to the fourth power.
The ratio of a sections Moment
of Inertia and the distance
between the neutral surface and
the outermost edge of the
section, “c” is referred to as:
The section modulus
The formula for Section Modulus is:
S = I / c
The two reasons that column
buckling occurs are:
If an applied load is eccentric, or doesn’t
occur exactly at a column’s centroid, it will
impart some degree of moment, causing
bending.
No material is truly uniform in its internal
composition. Any very slight variation of
the material will tend to allow buckling in a
column.
Finding this value quantifies a
cross section’s ability to resist
buckling under an axial
compressive load by relating
its moment of inertia and area.
Radius of gyration The radius of gyration
is a convenient parameter, providing a
measure of the resistance of a crosssection
to lateral buckling.
A load imposed on a
structural member at some
point other than the centroid
of the section is called:
Eccentric Load
Bending stress is a function
of the section modulus and
the:
bending moment
Define slenderness ratio:
The ratio of a wall or columns
unsupported height/length to its thickness
and measures its ability to resist buckling
when a compressive load is applied.
Vertical steel reinforcing
within reinforced concrete
columns essentially are very
slender ______ when
compressive stress is applied.
columns
A special kind of made up
beam that uses members
efficiently by placing them in
pure compression or tension,
when loaded properly, to carry
loads over a span is called a:
truss
The two methods for manually
analyzing trusses are:
the method of joints and the method of
sections
In this type of truss analysis, a
cut is made passing through
no more than three members,
and the three equations of
equilibrium are applied:
method of sections
Forces acting toward a joint
indicate a truss member is in:
tension
LIQUEFACTION
Liquefaction is a process by which water-saturated
sediment temporarily loses strength and acts as a
fluid.
For liquefaction to be possible, there has to be space
between particles that water can occupy.
Liquefaction can have dramatic and devastating
impacts during an earthquake.
Sites that are prone to liquefaction are said to be
liquefiable or to have liquefiable soils.
Sands, muds, and silts are the soils most vulnerable
to liquefaction. These often occur naturally or as
landfill in coastal areas.
SEISMIC WAVES
Seismic waves are oscillations at the molecular level within
the soil.
In an earthquake, sudden relative displacement of very large
masses and energy release results in waves of particle
displacement rushing through the surrounding rock and soil.
Seismic waves project outward from the hypocenter, but
have different velocities and characteristics.
The hypocenter generally occurs at a depth measured in
miles, or kilometers, below the surface.
There are many types of seismic waves. The three of
concern to us are:
P waves or Primary Waves
(also called Pressure Waves)
S waves or Secondary Waves
(also called Shear Waves)
Surface Waves
P WAVES
One of the seismic waves produced in
soils by earthquakes
• Have the highest velocity and will arrive
at distant locations first
• therefore, they also called Primary waves
• Cause compression in soil, in the
direction of travel, in an alternating pushpull
fashion
• also called Pressure waves
• can travel through liquid
S WAVES
•one of the seismic waves produced in soils by
earthquakes
•have the second highest velocity and will arrive
at distant locations just after the P waves
•therefore, they also called Secondary waves
•cause shear in the soil particles, causing
motion perpendicular to direction of wave travel
•therefore they also called Shear waves
•the shearing forces they transmit cause
damaging sideways and vertical accelerations
at the surface
•cannot travel through liquid
SURFACE WAVES
• one of the seismic waves produced in soils by
earthquakes
• have the lowest velocity and will arrive at distant
locations after the P waves and after the S waves
• vertical displacements in the earth’s surface
• tend to last longer and have larger amplitudes;
can be very destructive
• restricted to near the earth’s surface.
• analogous to waves in the ocean that do not
disturb the water at depth.
• as depth increases, ground displacements
decrease.
(FEMA 454 Ch. 2)
STABILIZING MOMENT
A building’s self-weight creates a moment in the opposite
direction of it’s overturning moment.
This is it’s stabilizing moment.
The building code establishes factors of safety between
stabilizing moment and overturning moment. When overturning
moment results from earthquake loads, the basic loading
combinations in IBC 1605.3.1 (taken from ASCE 7-05 chapter 2)
govern how resisting moment is compared to overturning
moment.
Using LRFD, load and resistance factor design:
compare 0.9D and 1.0E
(90% of dead load * moment arm) and (100% earthquake load *
moment arm)
Using ASD, allowable stress design:
compare 0.6D and 0.7E
(60% of dead load * moment arm) and (70% earthquake load *
moment arm)
BASE SHEAR
STORY SHEAR is defined by ASCE 7 as “The
summation of design lateral seismic forces at levels
above the story under consideration.”
Therefore BASE SHEAR is the sum of all STORY
SHEARS at the base.
This is commonly referred to as SEISMIC BASE
SHEAR.
The diaphragms at each story must transfer the force
received at that level, plus those from the levels
above.
The shear forces proceed downward in this additive
fashion until they reach the base.
BASE SHEAR is “Total design lateral force or shear
at the base.” (IBC 2009)
What is SDC?
Seismic Design Category. The IBC and
ASCE 7-05 have requirements for
geotechnical investigations relating to
seismic forces likely to be experienced at
a site.
All sites are assigned a Seismic Design
Category which the authority having
jurisdiction will use in evaluating a project.
What is “fundamental
period”?
Fundamental period is a measure of the time an
object takes to travel out and back once, when a
force has acted on it.
It is defined in FEMA 454 by the often used
analogy of a child on a swing. When we push a
child on a swing, if we want it to go higher, we
push just as the child starts travelling away from
us.
The fundamental period of a building is the time,
in seconds, that a building takes to sway out and
back again in an earthquake.
In an earthquake, all structures tend to sway back
and forth at their fundamental period.
What is a “fault”?
A fault is a plane within rock that forms in
response to stress. Most commonly, though
not always, the stress is induced by movement
of tectonic plates.
A fault can be a vertical plane, a horizontal
plane, or any orientation in between
Stress resulting from movements of masses of
crust accumulates along faults.
When the capacity of the rock is reached,
slippage occurs and energy is released in the
form of an earthquake.
An earthquake’s depth and its
relative location to a building
is often directly related to its
____?
Destructive power.
An earthquake’s depth (vertical distance)
and its relative location to a building
(horizontal distance) is often directly to its
destructive affects.
Earthquakes have complex, immediate,
and often violent effects on the rock and
soil around them, in the form of seismic
waves.
THEORY OF PLATE
TECTONICS
The theory of plate tectonics holds that the
earth’s crust is made up of masses that
essentially float on molten rock below.
These cooled, solidified chunks of crust ride
around on the molten material below,
somewhat freely.
The exact cause of the movement is debated,
but the movements have been observed.
All plate boundaries, where different plates
meet, have earthquake faults.
However, not all faults occur at plate
boundaries.
CRUSTAL CONVEYOR BELT
It’s the loop of creating crust at mid-ocean ridges and
destroying it at subduction zones.
It includes fault systems that are great distances from
each other at either end of the loop.
No material is “created” or “destroyed”, this is a
shorthand used to describe a change of state from liquid
to solid and back again.
Crust is created at mid-ocean ridges, travels over very
long periods of time to subduction zones, and is pushed
down and “destroyed” or converted back to magma.
It was theorized to exist because the mass of the earth
remains unchanged, yet crust was known to be
destroyed.
The discovery of the system of mid-ocean ridges and
divergent faults confirmed the theory.
The amplitude of any wave is
proportional to _____ .
The energy the wave transmits.
True of any wave, including seismic
waves.
Higher amplitude seismic waves means
more energy, more acceleration, more
force on a building.
A low ratio of width to height
has what advantage for a
building?
It minimizes tendency the to overturn
when acted on by lateral loads, including
seismic loads.
Coefficient of friction
The coefficient of friction describes the ability
to resist sliding, such as a footing transferring
lateral loads to the ground. The higher the
coefficient, the greater that soil’s capacity to
resist sliding.
To get the capacity for resisting sliding in a
footing, multiply the coefficient of friction * the
dead load (the vertical load) on the footing.
For certain soil classes, the IBC gives a lateral
sliding resistance value to be multiplied by the
contact area, instead of using a coefficient of
friction.
A pendulum clock is an
example of _____ .
Resonance. The pendulum swings back
and forth propelled by its own weight. A
mechanism imparts a very small force to
overcome friction, keeping the pendulum
going at a constant rate. If the timing isn’t
exactly right, the pendulum would
eventually stop.
The magnitudes of seismic
forces a building will
experience are determined by:
• The building’s weight
• The maximum ground acceleration
These dictate the magnitude of the forces.
Once the forces act on the building, it’s
overall configuration determine how those
forces will be transferred to the ground.
Fundamental periods of
buildings relate primarily to
height. True or false?
True. An approximate rule-of-thumb is to
divide the number of stories by 10 to
estimate the fundamental period in
seconds. Any particular building’s
fundamental period can also be influenced
by its structural system and detailing,
especially those of the lateral force
resisting elements.
Response Spectrum
Represents a building’s range of responses to
ground motion of different frequency.
May be called a Site Response Spectrum when
referring to a specific site.
A graph that plots the maximum response values of
acceleration, velocity, and displacement against
period and frequency
(FEMA 454 Ch. 4)
A Site Response Spectrum enables us to see how
buildings of different fundamental periods will
behave on the same site. It also helps us avoid
resonant loading of a building.
One benefit of creating a
Response Spectrum is:
The response spectrum tells us the
resonant frequencies at which a building
will undergo peak accelerations.
The building design can be adjusted, or
tuned, so the building period does not
coincide with the site period of maximum
response.
What is SFRS?
Seismic Force-Resisting System
The vertical elements of a building that take seismic load
from the diaphragms and transfer it to the ground.
From ASCE 7-05 Chapter 11 Definitions”
“SEISMIC FORCE-RESISTING SYSTEM: That part of the
structural system that has been considered in the design to
provide the required resistance to the seismic forces
prescribed herein.”
In the building code, horizontal elements such as
diaphragms are not included in the SFRS, nor does the code
use that acronym.
However, diaphragms are considered as integrally related
with the vertical SFRS elements. They are designed in
conjunction.
Name three basic alternative
types of vertical SFRS and
their essential characteristics.
Shear walls
• receive lateral forces from diaphragms and transmit them to the
ground.
• resists lateral force by developing shear in their planar surfaces
Braced frames
• receive lateral forces from diaphragms and transmit them to the
ground.
• generally less resistance than shear walls, and more ductility
• ductility can be adjusted with detailing of the joints
Moment-resisting frames
• frame without diagonal bracing
• resist lateral forces primarily by bending in beams and columns
• require strong column-beam joints to take moment
( some items summarized from FEMA 454 sec. 5.2.1 )
Regardless of group, any
vertical SFRS must continue
from roof to base without
interruption to perform the
best. True or false?
True.
• Decreasing the horizontal dimension of
the SFRS from one story to another
decreases its capacity.
• Eliminating the SFRS from one story to
another breaks the load path.
• Openings in shear walls reduce capacity,
and create stress concentrations.
DUCTILITY
Ductility describes a material’s or system’s
ability to undergo deformation without
breaking, and while still carrying load.
A metal spoon can be bent back and forth
several times before it breaks.
However a plastic spoon breaks almost
instantly, with a sudden snap.
This illustrates metal’s ductility, and
plastic’s brittleness.
(FEMA 454 Chapter 4.9)
Steel and ductility
Steel’s capability of withstanding load past
the yield point on the stress-strain curve
makes it a very ductile material.
Steel is often combined with other
materials to add ductility, such as in
reinforced concrete.
Steel is often used in Seismic Force
Resisting Systems in ways intended to
add ductility.
Ductility in lateral force
resisting systems (or the
SFRS)
• absorbs energy (often desirable)
A building whose lateral force resisting
elements are more ductile will have to
resist smaller seismic forces than its less
ductile counterpart.
Are shear walls generally
considered ductile or nonductile?
Non-ductile
Shear walls resist lateral forces by
developing shear in their planar surfaces.
Shear walls are generally the most rigid,
therefore the least ductile, of the three
SFRS groups.
Are moment-resisting frames
considered generally ductile
or non- ductile?
Ductile
Moment-resisting frames are, generally,
the most ductile of the three SFRS groups.
They are generally the least rigid, therefore
the most ductile.
The San Andreas Fault is what
type of fault?
A transform fault or strike-slip
The movements are primarily horizontal.
The Pacific Plate and the North American Plate are
moving about northwest and southeast,
respectively. The average annual movement
relative to each other is about a couple inches.
Due to friction, the plates get “stuck” against each
other at this boundary zone.
Periodically, enough stress builds up for sudden
slippage to occur. This slippage is an earthquake.
A building’s configuration:
is a large factor in its ability, or inability, to
survive an earthquake.
Stress concentration
“Stress concentration occurs when large
forces are concentrated at one or a few
elements of the building, such as a particular
set of beams, columns, or walls.”
( FEMA 454 sec. 5.3.1 )
Reentrant corners (in plan) and offsets (such as
at a setback roof) are examples of building
form likely to cause stress concentrations.
Both can be “irregularities.”
Idealized “regular” building
configuration:
Identical resistance on both
axes (of a plan)
Identical resistance on both axes of a plan:
“Eliminates eccentricity between the
centers of mass and resistance and
provides balanced resistance in all
directions, thus minimizing torsion. “
( FEMA 454 sec. 5.2.3 )
Idealized “regular” building
configuration:
Continuous load path
(vertically and horizontally)
Continuous load path:
This “regular” building configuration is
worth considering, because:
• interruptions in load path always
produce stress concentrations
• a continuous load path minimizes stress
concentrations
( see FEMA 454 ch. 5 )
Idealized “regular” building
configuration:
Symmetrical plan shape
Symmetrical plan shape:
This “regular” building configuration is
worth considering, because it:
• minimizes stress concentrations
• minimizes torsion
( see FEMA 454 ch. 5 )
“Idealized ““regular”” building
configuration:
Arrangement of vertical SFRS
elements
Symmetrical and parallel arrangement of
vertical SFRS
• SFRS (in plan) arranged in two directions
• SFRS (in plan) in parallel on opposite
sides
• minimizes torsion and stress
concentrations
( see FEMA 454 ch. 5 )
Idealized “regular” building
configuration:
Uniform strength and stiffness
at perimeter
Uniform strength and stiffness at
perimeter
• reduces the likelihood of torsion.
( see FEMA 454 ch. 5 )
Idealized “regular” building
configuration:
Equal floor heights
This is one aspect of a “regular” building
configuration.
• equalizes column and wall stiffness
• minimizes stress concentrations
( see FEMA 454 ch. 5 )
Idealized “regular” building
configuration:
Uniform sections and
elevations
This is one aspect of a “regular” building
configuration.
• eliminates offsets, minimizing stress
concentrations
( see FEMA 454 ch. 5 )
Idealized “regular” building
configuration:
Low ratio of width to height
This is one aspect of a “regular” building
configuration.
• minimizes tendency toward overturning
Define base shear.
Total design lateral force or shear at the
base.
The term that describes the
ability of a structural system
or element to dissipate energy
beyond its elastic limit is:
ductility
ELFP
Equivalent Lateral Force Procedure
This procedure in ASCE 7-05, which is
incorporated by the IBC 2009, establishes
how to calculate Seismic Base Shear.
Equivalent Lateral Force
Procedure:
Seismic Base Shear:
V = CsW
the formula for seismic base shear is:
V = CsW
V = seismic base shear
It is the sum total of all story shears. In effect, it gives us the
total seismic (lateral) force a building must resist.
The formula is about establishing a reasonable percentage of
the actual force to which we will design.
Cs = seismic response coefficient
It collects factors related to:
• occupancy (Importance)
• soils at the site
• ground acceleration
W = effective seismic weight (of the building)
Equivalent Lateral Force
Procedure:
Seismic Response
Coefficient:
Cs
The Seismic Response Coefficient, CS, is used in calculating seismic
base shear.
CS = seismic response coefficient
It collects factors related to:
• occupancy (Importance)
• soils at the site
• ground acceleration
Cs = SDS / ( R / I )
where:
SDS = 2/3 SMS
and:
SMS = FaSs
If you find yourself working with
Cs, it’s more useful to rewrite it
as:
2/3 (FaSs) / (R / I )
because you can then more easily
plug in or find Fa, Ss , R and I.
Equivalent Lateral Force Procedure:
Design earthquake spectral response
acceleration parameter at short period:
SDS
SDS is used in calculating seismic base shear.
“Design earthquake spectral response acceleration
parameter at short period” This is a fancy way of saying
“acceleration.” In this case, it is ground acceleration.
The formula for SDS is:
SDS = 2/3 SMS , where: SMS = FaSs
The formula is about establishing a reasonable percentage of
the actual force to which we will design.
Why is the 2/3 there? It’s arbitrary, and knocks a third off the
acceleration to be used in calculating seismic base shear.
Fa is the Site Coefficient; it reduces or increases the
acceleration depending on Site Class (soil characteristics)
Ss is ground acceleration from maps or the USGS web site,
or: “Mapped spectral response acceleration at short periods”
Equivalent Lateral Force
Procedure:
Response Modification Coefficient:
R
The Response Modification Coefficient, R, is used in
calculating seismic base shear.
It’s given in tables in ASCE 7, which is referenced by
the IBC. Greater ductility translates to a higher R
value. For example, shear walls have low R values
and moment-resisting frames have high R values.
Other systems generally fall in between. That is a
simplified summary, but it’s all we need to know.
•greater R = lesser seismic base shear
• lesser R = greater seismic base shear
In a basic sense, what must
be considered when
designing the structural
system of a building?
The vast range of physical loads also shape the
elements of the structure: animated and
inanimate objects, as well as resistance to
anticipated and unanticipated loads. Materials,
equipment and other dead loads, and varying
loads - such as snow, ponding of water on the
roof, wind and earthquake - must be calculated
and elements properly sized for. International
and building codes direct structural choices as
well. If conflicting information appears in
building codes, the most stringent one prevails.
Equivalent Lateral Force
Procedure:
Site coefficients and adjusted MCE
spectral response and acceleration
parameters:
SMS
SMS is used in calculating seismic base shear.
“Site coefficients and adjusted MCE spectral response and
acceleration parameters” This is a fancy way of saying
“acceleration.” In this case, it is ground acceleration.
Essentially, it’s acceleration, taken from maps or the
USGS web site, modified by a factor that considers
the soils at the site.
SMS = FaSs
Fa is the Site Coefficient; it reduces or increases the
acceleration depending on Site Class (soil characteristics)
Ss is ground acceleration from maps or the USGS web site,
Equivalent Lateral Force
Procedure:
Site Coefficient:
Fa
Fa , Site Coefficient is used in calculating
seismic base shear.
Fa is the Site Coefficient; it reduces or
increases the acceleration depending on
Site Class (soil characteristics)
Equivalent Lateral Force
Procedure:
Mapped spectral response
acceleration at short periods:
SS
SS is used in calculating seismic base shear.
“Mapped spectral response acceleration at short
periods”
This is a fancy way of saying ground acceleration that
we get from maps (or the USGS web site.)
SS forms the basis of the “A” or acceleration
remember, when determining seismic base shear, it
really all boils down to Newton’s Second Law of Motion:
F=mA
Force = mass * Acceleration
Name some of the general
types of luminaries.
Surfaced mounted, recessed, suspended,
freestanding, wall mounted and accessory
lighting.
Per the IBC, if site soil
conditions are not known in
sufficient detail, what is the
best site class category that
can be used?
Site Class D: Stiff soil profile
What is fluid mechanics in
relation to wind design?
The branch of physics that studies
physical properties and behaviors of
fluids, which teaches us about wind
behavior.
