ExAC - Section 3 - Final Project Questions with
Correct Answers
What is: Design wind pressure? Correct Answer-Design wind pressure:
Minimum design value for the equivalent static pressure on the exterior
surfaces resulting from critical wind velocity (equal to a reference wind
wind pressure measured at 33', 10m). The # is modified by a bunch of
coefficients to account for: exposure conditions, building height, wind
gusts, geometry/orientation.
Why are horizontal forces more critical than vertical ones in seismic
design? Correct Answer-Because structures usually have considerable
reserve for dealing with additional vertical loads.
Define Base Shear. Correct Answer-Base shear:
Minimum design value for the total lateral seismic force (assumed to act
in any horizontal direction)
Define the following: Collinear Forces, Concurrent Forces,
Nonconcurrent Forces. Correct Answer-Collinear Forces:
Occur along straight line. Vector sum= sum of magnitude of forces
acting along same line of action.
Concurrent Forces:
Lines of action intersecting at common point. Vector sum=equivalent to,
and produces same effect on rigid body as the application of the vectors
of the several forces.
,Nonconcurrent Forces:
Lines of action that do not intersect at common point. Vector
sum=single force that would cause the same translation and rotation of a
body as the set of original forces.
What is a moment (structural forces)? Correct Answer-Moment:
The tendency of a force to produce rotation of a body about a point or
line
What is a Couple (structural forces)? Correct Answer-Couple:
Force system of 2 equal parallel forces acting in opposite directions
tending to produce rotation but not translation
What are beams designed to do? Correct Answer-Designed to carry and
transfer transverse loads across to supporting elements.
Define Deflection Correct Answer-Deflection:
perp distance a spanning member deviates from true course under
transverse loading
What is the difference between a simple beam and a Fixed-End Beam?
Correct Answer-Simple Beam:
Rests on supports at both ends - no moment resistance (ends free to
rotate)
,Fixed-end beam:
Both ends fixed against translation and rotation (reduced max deflection,
transferred bending stresses, increased rigidity)
Distinguish between the following three frame types:
-Fixed Frame
-Hinged Frame
-Three Hinged Frame Correct Answer-Fixed Frame
rigid frame connected to its supports with fixed joints (more resistant to
deflection than hinged from but also more sensitive to settlements and
thermal expansion/contraction)
Hinged Frame -
Rigid frame connected to its joints with pinned connections (pinned
connections prevent high bending stresses by allowing rotation)
Three-hinged Frame - structural assembly of 2 rigid sections connected
to each other and to its supports with pin joints (more sensitive to
deflection than fixed or hinged, 3-hinged system is least affected by
support settlements and thermal stresses - can also be analyzed as a
statically determinate structure
Name 1 kind of beam for each wood, steel, and concrete, that can span
>60' (18m). Correct Answer-Wood:
Laminated Beams (Timber)
, Trusses (Timber)
Steel:
OWSJ
Concrete:
Precast Tees
List three basic mechanisms for resisting lateral loads. Correct Answer-
Rigid Frame
steel or reinforced concrete with rigid joints
Shear Wall
wood/concrete/masonry - resist changes of shape and transfer cert loads
to ground foundation
Braced Frame - timber or steel
Knee brace
K-brace
Cross-brace
What is the least effective way to achieve lateral stability? Correct
Answer-Rigid frame (only appropriate in low-mid rise buildings)
Correct Answers
What is: Design wind pressure? Correct Answer-Design wind pressure:
Minimum design value for the equivalent static pressure on the exterior
surfaces resulting from critical wind velocity (equal to a reference wind
wind pressure measured at 33', 10m). The # is modified by a bunch of
coefficients to account for: exposure conditions, building height, wind
gusts, geometry/orientation.
Why are horizontal forces more critical than vertical ones in seismic
design? Correct Answer-Because structures usually have considerable
reserve for dealing with additional vertical loads.
Define Base Shear. Correct Answer-Base shear:
Minimum design value for the total lateral seismic force (assumed to act
in any horizontal direction)
Define the following: Collinear Forces, Concurrent Forces,
Nonconcurrent Forces. Correct Answer-Collinear Forces:
Occur along straight line. Vector sum= sum of magnitude of forces
acting along same line of action.
Concurrent Forces:
Lines of action intersecting at common point. Vector sum=equivalent to,
and produces same effect on rigid body as the application of the vectors
of the several forces.
,Nonconcurrent Forces:
Lines of action that do not intersect at common point. Vector
sum=single force that would cause the same translation and rotation of a
body as the set of original forces.
What is a moment (structural forces)? Correct Answer-Moment:
The tendency of a force to produce rotation of a body about a point or
line
What is a Couple (structural forces)? Correct Answer-Couple:
Force system of 2 equal parallel forces acting in opposite directions
tending to produce rotation but not translation
What are beams designed to do? Correct Answer-Designed to carry and
transfer transverse loads across to supporting elements.
Define Deflection Correct Answer-Deflection:
perp distance a spanning member deviates from true course under
transverse loading
What is the difference between a simple beam and a Fixed-End Beam?
Correct Answer-Simple Beam:
Rests on supports at both ends - no moment resistance (ends free to
rotate)
,Fixed-end beam:
Both ends fixed against translation and rotation (reduced max deflection,
transferred bending stresses, increased rigidity)
Distinguish between the following three frame types:
-Fixed Frame
-Hinged Frame
-Three Hinged Frame Correct Answer-Fixed Frame
rigid frame connected to its supports with fixed joints (more resistant to
deflection than hinged from but also more sensitive to settlements and
thermal expansion/contraction)
Hinged Frame -
Rigid frame connected to its joints with pinned connections (pinned
connections prevent high bending stresses by allowing rotation)
Three-hinged Frame - structural assembly of 2 rigid sections connected
to each other and to its supports with pin joints (more sensitive to
deflection than fixed or hinged, 3-hinged system is least affected by
support settlements and thermal stresses - can also be analyzed as a
statically determinate structure
Name 1 kind of beam for each wood, steel, and concrete, that can span
>60' (18m). Correct Answer-Wood:
Laminated Beams (Timber)
, Trusses (Timber)
Steel:
OWSJ
Concrete:
Precast Tees
List three basic mechanisms for resisting lateral loads. Correct Answer-
Rigid Frame
steel or reinforced concrete with rigid joints
Shear Wall
wood/concrete/masonry - resist changes of shape and transfer cert loads
to ground foundation
Braced Frame - timber or steel
Knee brace
K-brace
Cross-brace
What is the least effective way to achieve lateral stability? Correct
Answer-Rigid frame (only appropriate in low-mid rise buildings)
