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SEMI S2-0703a E © SEMI 1991, 2004 62 R5-2 Derivation of Section 19, Seismic Load Guidelines R5-2.1 The horizont al loadings of 9 4% and 63%, fou nd in Sections 19.2.1 a nd 19.2.2, were based on foll owing assumptions for…

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Yes No Comments:
3. Are there any threaded connections, flange joints, or special fittings?
Yes No Comments:
4. If answer to Question 4 is “Yes,” are these connections, joints, or special fittings in high stress locations?
Yes No Comments:
5. Are there short or rigid spans that cannot accommodate the relative displacement of the supports (e.g.,
piping spanning between two structural systems)? Is hazardous gas piping provided with a “pigtail” (i.e., spiral) or
bent 3 times (z, y, and z direction) to absorb 3-dimensional displacements?
Yes No Comments:
6. Are there large, unsupported masses (e.g., valves) attached to components?
Yes No Comments:
7. Are there any welded attachments to thin wall components?
Yes No Comments:
8. Could any sensitive equipment (e.g., control valves) be affected ?
Yes No Comments:
C. Seismic Interactions
1. Are there any points where seismically induced interaction with other elements, structures, systems, or
components could damage the components (e.g., impact, falling objects, etc.)?
Yes No Comments:
2. Could there be displacements from inertial effects?
Yes No Comments:
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R5-2 Derivation of Section 19, Seismic Load Guidelines
R5-2.1 The horizontal loadings of 94% and 63%, found in Sections 19.2.1 and 19.2.2, were based on following
assumptions for factors in formula 32-2 in Section 1632.2 of the 1997 Uniform Building Code (UBC):
a
p
= 1.0 (i.e., treat the equipment as a rigid structure)
C
a
= 0.44(1.2) (i.e., seismic zone 4, soil profile type S
D
, and site 5 km from a seismic source type A)
I
p
= 1.0 and 1.5 for non-HPM and HPM equipment, respectively
h
x
/h
r
= 0.5 (i.e., equipment attached at point halfway between grade elevation and roof elevation)
R
p
= 1.5 (i.e., shallow anchor bolts).
Starting with equation 32-2, letting I
p
= 1.5, and substituting the above values:
F
p (ultimate)
= [(1.0 * 0.44(1.2) * 1.5)/ 1.5] [ 1 + 3(0.5)] W
p
= [0.44(1.2)] [ 1 + 1.5] W
p
= [0.528] [ 2.5] W
p
= [1.32] W
p
NOTE R5-2: This number is now adjusted from ultimate strength loading to yield strength loading by dividing by 1.4:
F
p (yield)
= F
p (ultimate)
/ 1.4
= [1.32] / 1.4 W
p
= [0.94] W
p
And for I
p
= 1.0,
F
p
(yield)
= [.94] [ 1.0/1.5] W
p
= [.63] W
p
Notes re selection of a
p
value of 1.0:
Table 16-O of 1997 UBC, line 3.C., was interpreted to read: “Any flexible equipment...”
in structural terms, the structure of typical semiconductor equipment is considered “rigid.”
R5-2.2 Assumptions Used for Above Derivation
R5-2.2.1 Because typical semiconductor equipment is considered rigid, a frequency response analysis was not
considered to be necessary.
R5-2.2.2 Seismic waves typically have vertical as well as horizontal components associated with them; however,
these components typically arrive out of phase (i.e., they do not reach maximum values simultaneously). The
vertical component serves to, in effect, reduce the amount of equipment mass that is available to resist overturning
or toppling. The task force chose to take this into account by limiting the calculated weight available to resist
overturning to 85% of the weight of the equipment. An alternate method, not chosen by the task force, could have
been to simultaneously apply a vertical (Z) force.
R5-3 Source for Examples of Seismic Anchorage Details
R5-3.1 Detailed illustrations of examples of seismic anchorage details were developed by Working Group #9 of the
Japan 300 mm (“J300”) effort, and were printed in their Report No. 9 in the 2nd Lecture, ICs Factory Design for
300 mm Wafer Line Standardizing Study, December, 1996.
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L1
L2
A
h
A
A
R
L3
A B
VIEW A – A
F
p(x)
CG
F
p(y)
Figure R5-1
Design Example