Exam 2 Flashcards
Space frame
three-dimensional trussed system spanning in two directions where members are in tension or compression only.
What are the two most widely used polyhedral modules (shapes) for building space frames?
half-octahedron and tetrahedron
What do space frames consist of?
identical repetitive module, with parallel upper and lower layers (which correspond to the chords of trusses)
How is labor cost for space frames affected by changes in module size?
Labor costs increase as module sizes decrease and decrease as module sizes increase
What does a half octahedron look like?
An equilateral pyramid with a SQUARE base
What does a tetrahedron look like?
A pyramid with a TRIANGULAR base
What are the possible support types for space frame systems?
- Column (point) supports
- Inverted pyramid
- Crosshead beams
Tensegrity
a stable three-dimensional space frame assembly of cables and struts where the cables are continuous but the struts are discontinuous and do not touch one another.
What does the term stayed apply to? (vertical hanger topic)
Tension hangers are not always vertical but often are inclined for either pragmatic or conceptual design reasons.
What was the worst structural disaster in the United States?
The Hyatt Regency, Kansas City, Missouri
Beam Definition
Linear structural member with loading applied perpendicular to its long axis: such a load is a bending load
Bending
The tendency of a member to bow as a result of loads applied perpendicular to its longest axis
What does bending cause?
One face of the member to stretch (tension) and the opposite face to shorten (compression)
What is the most common example of a structural member bending?
A beam
What stresses are also present when tension and compression stresses are occurring in parallel? (Beam)
shearing stresses
Difference between a tie and a hanger?
Hanger deals with gravity vs. a tie just locks elements to resist forces
In what form did beams originate?
Horizontal stone resting on two vertical columns
Bending stress
Combination of compressive and tensile
stresses developed at a cross section of the beam
Where are compressive and tensile stresses located on a simple span beam?
compressive in the top portion of the beam and tensile stresses are in the bottom portion of the beam.
How is beam efficiency increased?
by making the section deep with most of the material at the extremities – farther from the neutral axis – where the maximum bending stresses occur
Why is beam depth important to consider?
for reducing bending stresses and limiting vertical deflection
What do wooden beams support?
structural planking or decking.
What do steel beams support?
steel decking or precast concrete planks.
Horizontal spans may be traversed by…?
nearly homogeneous slabs of reinforced
concrete or hierarchical layers of steel or
wood girders, beams, and joists
supporting a plane of structural sheathing
or decking.