Chapter 3 Flashcards
What is a Force?
A vector, it has a direction and a Magnitude.
MEASURED: Forces will be in the units of KIPS or POUNDS
What is a Moment?
The tendancy of a force to cause about a given point or axis.
MEASURED: Kip-Feet, Pound-In
What is a force couple?
Two equal forces of opposite magnitude act in an opposite direction and are seperated by some distance.
M + (P) (e)
P= is the eccentricity or distance. In this scenario the engineer is communicating that a moment is being induced into the system and has to be dealt with.
What is the difference between a moment and a resisting moment.
A resisting moment occurs at the support, while the moment occurs at the edge of the cantilever.
What is a Diaphragm
- Roof, Floor or other membrane or bracing system acting to transfer the lateral forces to the vertical resisting elements.
- Typically a planar horizontal or nearly horizontal element that resists shear forces in its own plane and transmits the forces to the vertical lateral load resisting elements.
- Can be Flexible or Rigid
- Shear walls are sometimes referred to as vertical diapragms
T/F, Shear walls CAN be considered a vertical diaphragm.
True.
Flexible Diaphragms
change shape when subjected to lateral loads; its tension chord bends outward and its compression chord bends inward
What is the function of a diaphragm?
To distribute loads to the vertical resisting elements in proportion to their tributary areas.
T/F, Flexible diaphragms ARE considered capable of transmitting torsion to the resisting elements?
False, they cannot transfer torsion loads.
What are some examples of a rigid diaphragms?
Structural concrete systems, concrete filled metal deck over structural steel framing, etc, are considered to be rigid diaphragms.
T/F, Rigid diaphragms ARE considered capable of transmitting torsion to the resisting elements?
True.
What are some examples of flexible diaphragms?
Wood structural panels (plywood, osb, etc.) light gauge metal deck or light gauge metal deck with insulating fill such as sonolite are considered to be flexible diaphragms.
With respect to the design of Columns, the effective length factor “K” is dependent on?
The support at each end of the column.
On a simply supported beam with a uniform load, where does the maximum bending stress occur?
At the mid-span at the extreme fibers
On a simply supported beam with a uniform load, where does the maximum shear stress occur?
The stress is greatest at the neutral axis and is equal along the length of the beam.
T/F Seismic forces ARE NOT applied through the center of mass?
False, Seismic forces “ARE” applied through the center of mass
Torsion is calculated by multiplying what two factors?
Is the difference in distance between the center of gravity and the center of rigidity multiplied by the torsional force.
T/F Torsion only occurs on a rigid diaphragm.
True
During a horizontal load, at what plane do the horizontal loads transfer into the diaphragm?
At the Ceiling/Floor Plane
http://acg.media.mit.edu/people/simong/statics/data/beamLoadingApp.html
shear and moment diagram
T/F When a shear diagram crosses 0, that is a point of maximum moment?
True
There is a simply supported beam with a uniform load, on a moment diagram what is the point called where the moment diagram crosses 0?
The inflection point.
Where does an overturning moment occur
for the whole building, the overturning moment occurs at the ground level.
For each level, the overturning moment occurs at the floor level of the story or stories.
How do you calculate the Factor of Safety?
Resistance x Demand (RM x OTM)
