Building Design and Construction Handbook - Merritt - Ventech!

STRUCTURAL THEORY 5.183
0.3S DSI pW p � F p � 1.6S DSI pW p
where F p � Seismic design force centered at the component’s center of gravity and
distributed relative to component’s mass distribution
S DS � Design spectral response acceleration at short period
� p � Component amplification factor that varies from 1.00 to 2.50 (select
appropriate value from Tables 5.19 and 5.20)
I p � Component importance factor that is 1.5 for life safety component and
1.0 for all other components
W p � Component operating weight
R p � Component response modification factor that varies from 1.0 to 5.0
(select appropriate value from Tables 5.19 and 5.20)
z � Height in structure at point of attachment of component. For items at
or below the base, z shall be taken as 0.
h � Average roof height of structure relative to the base elevation.
The force F p shall be applied independently longitudinally and laterally in combination
with service loads associated with the component. Component earthquake
effects shall be determined for combined horizontal and vertical load effects as Q E
in E. The redundancy based reliability coefficient, p, is permitted to be taken as
equal to 1.
(J. M. Biggs, ‘‘Introduction to Structural Dynamics,’’ and R. Clough and J. Penzien,
‘‘Dynamics of Structures,’’ McGraw-Hill Publishing Company, New York; E.
Rosenblueth, ‘‘Design of Earthquake-Resistant Structures,’’ Halsted/Wiley, Somerset,
N.J.; N. M. Newmark and E. Rosenblueth, ‘‘Fundamentals of Earthquake
Engineering,’’ Prentice-Hall, Englewood Cliffs, N.J.; S. Okamoto, ‘‘Introduction to
Earthquake Engineering,’’ John Wiley & Sons, Inc., New York, International Building
Code 2000)
5.20 FLOOR VIBRATIONS
Excessive vibration can be characterized as too large for sensitive equipment or too
large for occupant comfort. Determining these permissible levels is an entire research
area in itself; however, some of the more widely accepted levels are discussed
in following paragraphs. These levels are expressed by researchers in terms
of either acceleration, velocity, or displacement amplitudes and are often frequencydependent.
There is no consensus as to the most relevant measure for describing
acceptable levels.
Comfort of the occupants is a function of human perception. This perception is
affected by factors including the task or activity of the perceiver, the remoteness
of the source, and the movement of other objects in the surroundings. A person is
distracted by acceleration levels as small as 0.5% g. Multiple-use occupancies must
therefore be carefully considered.
Webster and Vaicitis describe a facility that has both dining and dancing in a
large open area. The floor was noted to have a first natural frequency of 2.4 Hz,
which is in resonance with the beat of many popular dance song. This resonance
response produced maximum acceleration and displacement levels of 7% g and
0.13 in, respectively. Such levels actually caused sloshing waves in drinks and
noticeable bouncing of the chandeliers. The occupants found these levels to be quite
objectionable.