Chapter 5 - Seismic Analysis of Buildings Flashcards
what is two stage analysis?
when an upper portion of a building is flexible and the lower portion is rigid. you can analyze both sections as separate structures if they meet all of the exceptions
what does it mean when a building has a high R value?
the structure is very ductile and higher redundancy
what are the units for the effective seismic weight?
kips or pounds
Site class is determined based on how many feet of soil depth?
100’
when determining site class and you have different soils, which one do you pick?
always pick the softer soil (btwn Class D or E, pick E)
what should be the assumed site class if a geotechnical report is not available?
site class D
solving for period of the structure
what is not included in the height of the building?
parapets and penthouses
what does ductility mean?
a buildings ability to deform and yield without collapse
What is the response modification coefficient, R?
used to reduce the seismic force from the level of force (elastic response with no damage) to the design force that would yield the structure
what does redundancy mean?
structural system elements, after yielding, re-distribute the loads to different resisting systems
what causes the R value to increase?
overall ductility and energy dissipitation increases and degree of redundancy
what is the overstrength factor?
is used to account for the reserved capacity of a structure that allows for the resistance of larger than design seismic force
what is the deflection amplification factor?
used to determine the actual (inelastic response) displacements exhibited by the structure when subjected to the design ground motion
what should you assume for effective weight when working an office problem?
always include 10 psf partition weight. even if it isnt stated you should assume
what is a lateral force?
a horizontal force applied to a building
what is a gravity load?
a vertical force applied to a building. aka a dead load
what is ductility?
a structures capability to deform and yield without collapse
theoretically, what is the ratio of the structure response mod (R)?
ratio btwn theoretical seismic force and prescribed seismic force. elastic response base shear VERSUS design base shear
what is the largest base shear that can occur?
think formula
base shear x overstrength factor
what is another term for the maximum base shear?
the actual base shear
how should you apply SFRS in the same direction for vertical combinations?
2 rules
1. lower SFRS has a lower R = design per the respective R
2. upper SFRS has a lower R - design both SFRS for the upper system
what is important to remember in combination SFRS problems and the R value?
the R value cannot increase as you go down the height it must decrease
what is ELF?
effective seismic weight = weight of the structure which includes walls and floor loads
what other value can you use for the base shear?
the first story shear
