Material Specific Flashcards
Modes of failure expected if the LFRS of an older high rise is constructed of reinforced concrete?
a) ends of columns with insufficient shear reinf. - column breaks out of its supports
b) columns with insufficient confinement
c) shear walls with inadequate vert reinf
d) construction joints - inadequate bonding between members
e) beams with inadequate shear reinf
f) columns with excessive drift and overturning
How to achieve ductility in concrete frame?
Confinement & continuity!!
Confinement allows steel to yield before concrete and continuity allows full tensile strength of steel to be developed.
Confined Concrete
Aka ductile concrete
Aka specially reinforced concrete
Steel yields before concrete crushes.
Concrete can develop full compressive strength without yielding
Construction methods used to ensure ductile behavior of concrete
Columns spiral wrapped at closer intervals
Additional hoops at joints
Continuity with special attention to splices
Special considerations for reinf in shear walls
Hooks, ties, stirrups, and hoops detailed to prevent pull-out
Which is better to resist seismic forces in reinf concrete columns, spiral ties or horizontal hoops?
Spiral ties are more efficient and provides slightly better confinement. Not always constructible with larger columns.
What is the effectiveness of stirrups in deep concrete beams?
Not effective at center of beam span.
If a masonry wall is part of the LFRS in a structure with seismic design category D, what types of cement mortar may be used?
Type S or Type M
Do special reinforcement hoops replace regular ties in beams and columns?
No, special reinforcement hoops are IN ADDITION to regular beam stirrups and column ties.
BEAMS: special reinf expected at pints of yielding (plastic hinges).
COLUMNS: hoops required at column-girder connections
How is failure defined if the LFRS of a high rise building is constructed of steel?
“Failure” in steel is when it severely yields or fractures
SMRF that is properly design is likely to yield where?
Within the beams, a distance away from the beam/column joint.
All connections should be able to sustain a full plastic moment of connected members
Which steel frame type is most likely to have doubled playes? OCBF, SCBF, OMRF or SMRF
SMRF
Doubler plates are used to increase the shear strength of the shear panel zone of a SMRF. Crucial for when the plastic hinges forms away from the beam/col joint.
How to calculation rotation of the link in an eccentric brace frame?
Θ = l / e * α
l= horizontal length of beam to brace e = horizontal length of link α = drift of structure (in decimal) Theta = rotation (in decimal)
x100 to get percentage
