PIEDMONT PIEDMONT PIEDMONT PIEDMONT PIEDMONT HIGH SC HIGH SC HIGH SC HIGH SC HIGH SC HOOL HOOL HOOL HOOL HOOL PIEDMONT UNIFIED SC PIEDMONT UNIFIED SC PIEDMONT UNIFIED SC PIEDMONT UNIFIED SC PIEDMONT UNIFIED SC HOOL DIS HOOL DIS HOOL DIS HOOL DIS HOOL DIS TRICT TRICT TRICT TRICT TRICT Seismic S Seismic S Seismic S Seismic S Seismic S tr tr tr tr tr engt engt engt engt engt hening Pr hening Pr hening Pr hening Pr hening Pr og og og og og r r r am / Measur am / Measur am / Measur am / Measur am / Measur e E Bond Pr e E Bond Pr e E Bond Pr e E Bond Pr e E Bond Pr og og og og og r r r am am am am am INVES INVES INVES INVES INVES TIG TIG TIG TIG TIG A A A TION AND AN TION AND AN TION AND AN TION AND AN TION AND AN AL AL AL AL AL Y Y Y SIS, SIS, SIS, SIS, SIS, AND C AND C AND C AND C AND C ON ON ON ON ON CEPT DESIGN CEPT DESIGN CEPT DESIGN CEPT DESIGN CEPT DESIGN FIN FIN FIN FIN FIN AL REPOR AL REPOR AL REPOR AL REPOR AL REPOR T T T f f f or Thr or Thr or Thr or Thr or Thr ee Pr ee Pr ee Pr ee Pr ee Pr ior ior ior ior ior ity Buildings ity Buildings ity Buildings ity Buildings ity Buildings March 6, 2008 R. P. Gallagher Associates, Inc. Structural Engineering
Transcript
PIEDMONTPIEDMONTPIEDMONTPIEDMONTPIEDMONT HIGH SC HIGH SC HIGH SC HIGH SC HIGH SCHOOLHOOLHOOLHOOLHOOL
Seismic SSeismic SSeismic SSeismic SSeismic Strtrtrtrtrengtengtengtengtengthening Prhening Prhening Prhening Prhening Progogogogogrrrrram / Measuram / Measuram / Measuram / Measuram / Measure E Bond Pre E Bond Pre E Bond Pre E Bond Pre E Bond Progogogogogrrrrramamamamam
INVESINVESINVESINVESINVESTIGTIGTIGTIGTIGAAAAATION AND ANTION AND ANTION AND ANTION AND ANTION AND ANALALALALALYYYYYSIS,SIS,SIS,SIS,SIS,
uad Building, built in the 1930’s, has had four additions,
resulting in five distinct structures. The original building was rectangular,
with the long axis oriented north-south. In the late 30’s or early 40’s, the
first addition created more classroom
s and formed the L configuration of
the building. In the mid 70’s, a third structure w
as built. At this tim
e, thelibrary w
as relocated from B
uilding B to this new
facility. In the mid 90’s,
the final two structures, the library expansion and the m
ezzanine spacew
as constructed.B
uilding B.
The Student Center B
uilding, built in the late 1930’s, is the originallocation of the library before it’s relocation to B
uilding A. The vacated
space was converted to a Student Lounge. A
lthough no drawings w
ereavailable, a com
mercial kitchen w
as added prior to 1997, when a proposed
remodel of the kitchen area w
as proposed, but never implem
ented. Thecurrent Student C
enter is a cafeteria, with pre-prepared food and snacks.
The kitchen is used for food warm
ing only.B
uilding C.
The Allen H
arvey Auditorium
Building, built in the m
id 1970’s., is aperform
ing arts auditorium w
ith stage, projection booth, and lobby area.B
elow the stage area are perform
er’s dressing rooms and toilet facilities.
The original workshop area has been converted to the A
dult Education
Office and the rem
ainder of the space is used for shipping, receiving, andstorage. N
o DS
A-approved draw
ings are available that show this
converted use.B
uilding D.
The Science/Language B
uilding, built in the mid 1970’s, is a non-priority
building and will be analyzed for non-structural seism
ic hazards,accessibility and life-safety during the next phase of the project (conceptdesign).
Building E
.The S
cience Building, built in m
id 1970’s, is a non-priority building andw
ill be analyzed for non-structural seismic hazards, accessibility and life-
safety during the next phase of the project (concept design).B
uilding F.The G
ymnasium
Building, built in the m
id-1970’s, is a non-priority buildingand w
ill be analyzed for non-structural seismic hazards, accessibility and
life-safety during the next phase of the project (concept design).B
uilding G.
The Adm
inistration / Art / M
illiennium H
igh Building, built in 1960’s, is a
non-priority building and will be analyzed for non-structural seism
ichazards, accessibility and life-safety during the next phase of the project(concept design).
2
2. AD
A / A
CC
ESIBILITY
Covered Thoroughfare betw
eenB
ldg. A & D
Ram
p to Plaza betw
een Bldg. A &
EP
laza surrounded by Bldgs. A
, B, &
C
Ram
p to Library Entry
in Bldg. A
Sloped w
alk (and fire lane) fromaccessible on-street parking
Ram
p next to Building C
Exisitng accessible parking
Existing accessible parking
Main entry point on to cam
pus
2.A
DA /A
CC
ESSIBILITY.
Background:
School facilities in C
alifornia are required by federal and state law to provide equal access for
students, teachers, staff and visitors. At the Federal level the em
powering legislation is the A
mericans
with D
isabilities Act or A
DA
. Under that law
AD
AA
G regulations w
ere written to describe the accessibility
requirements for the entire country. The A
DA
AG
regulations are enforced by civil action. At the State
level accessibility is governed by the California B
uilding Code. In the case of public school buildings the
California B
uilding Code is enforced by the D
ivision of the State Architect or D
SA
.The State of C
alifornia is in the process of getting the California B
uilding Code certified by the
Departm
ent of Justice as meeting A
DA
AG
. Until that occurs architects m
ust comply w
ith both theA
DA
AG
and the California B
uilding Code.
murakam
i/Nelson has used both docum
ents in evaluatingthe priority buildings at H
avens.The C
alifornia Building C
ode requires whenever m
ore than $120,000 (adjusted for inflationeach year) w
orth of work other than for m
aintenance or replacement of finishes is done in any three
year period for an existing building, that access compliance w
ork be included as part of that project.S
ection 1134B of the C
alifornia Building C
ode requires that alteration work w
ithin an existing buildingcom
ply with the current C
ode and that additional access work, as stipulated in the C
ode, be donebeyond the area of the alteration.
Because seism
ic upgrade projects often affect areas throughout a school the State Attorney
General has issued an interpretation (D
SA D
ocument 96-01) that access w
ork triggered by a seismic
strengthening project need only provide an accessible primary entrance, sanitary facilities, signs,
telephone (if provided), drinking fountain and an accessible path of travel to those facilities, but not aaccessible path of travel to the area of all the alterations as S
ection 1134B.2 of the B
uilding Code
requires. Use of this interpretation by D
SA on the P
iedmont S
eismic project rem
ains to be resolved.In any event the voluntary seism
ic strengthening work the D
istrict is planning will trigger substantial
compliance w
ith the access requirements of S
ection 1134. Furthermore, if State m
odernization fundsare used for the projects, then all the requirem
ents of Section 1134 w
ould be triggered.
Summ
ary & A
nalysis
This report has made use of the ATI report, w
ith field verification of existing conditions.P
iedmont H
igh School has had num
erous changes implem
ented over its 86 year history. With
the major new
construction that occurred in the mid 1970’s, the accessibility of the site and w
ithin thebuildings w
ere greatly enhanced, though accessibility issue do exist and the site and building are notfully com
pliant with current code and A
DA requirem
ents. See A
ppendix A for code review sum
mary.
Site:P
iedmont H
igh School is bound by the C
ity park to its east and south sides, the Piedm
ont Middle
School to its w
est, and the primary access to the school site, M
agnolia Avenue to its north. There aretw
o on-street parking stalls designated as accessible at the northwest corner of the school and tw
oparking stalls on-site near the G
ymnasium
. The two on-street parking spaces are not ideal, due to the
steepest of the sidewalk and street. The tw
o on-site parking space are remote and not near the prim
aryentries to the site. M
agnolia Avenue is the main drop-off and loading zone for the m
ajority of thestudents. N
o accessible drop-off/loading zone has been provided for the physically impaired student.
There are two accessible entry points onto the school cam
pus. The school utilizes a series of ramps to
provide accessibility to most of the buildings on the cam
pus. Access to the B
uilding F, the Gym
nasiumrequires the use of an elevator along the path of travel. A
ccess to the Building B
, the Student Center
primary entrance is not available and requires the physically im
paired to go around to the rear of thebuilding to enter. A
dditionally, the path of travel to the rear of the building involves walkw
ays thatexceed 5%
grade. Therefore those walkw
ays are technically ramps and m
ust comply w
ith ramp standards
or be reconfigured to be less than a 5% slope, if this route is to be utilized as an accessible path of
travel.M
any of the exterior stairs are not compliant, lacking handrails on one side or interm
ediaterailings, lacking proper extensions, and/or lacking proper contrasting striping on the stair treads. Theram
ps are lacking guide rail edge protection. The diameter of m
ost of the handrailing is non-compliant.
There is very little directional or informational signage throughout the site. A
ccessibility signageis non-existent and w
ill need to be provided.
3
Building B
- Needs accessible ram
p atprim
ary entrance to Cafeteria
Building B
- Stair railing not compliant
Building B
- Kitchen not accessible for
employees
Building B
- Cafeteria service counters &
queue line railing are not accessible
Building B
- Counselor’s O
ffice hallw
ay - doors need lever handles andhall cleared of obtructions.
Building B
- Need accessible
ramp to C
ounselor’s Offices
Building A - Thresholds at south side
exit doors too high
Building A - Lockers projects into the
required clear space at classroom entry
Building A - Stair striping
at many treads are w
oren
Building A - E
ntry doors at second floor are toonarrow
.
Buildings:
Building
A - Quad B
uilding/Library
The Quad B
uilding/Library was renovated in the m
id 90’s. As a part of that renovation, a m
ajorityof the accessibility deficiencies w
ere mitigated. In review
ing the current facility, there are still some
accessibility issues that may need to be addressed as follow
s:1)
The Library, one classroom, special education room
s, and former counseling offices
located on the first floor require persons in wheelchairs to exit the building, travel over 600
feet exposed to weather, to gain access to the second floor of the building. A
mbulatory
users of the building can use the stairs within the building. D
SA w
ill require that the existingelevator be upgraded to provide com
pliant vertical access for persons in wheelchairs.
Although there is an existing elevator, it does not m
eet correct size, layout, and signalingrequirem
ents.2)
The two pairs of entry doors on the north side of the Q
uad building are not a compliant
width and w
ill need to be replaced.3)
Thresholds at the south side exit doors exceed heights required to meet accessibility.
4)E
xisting hall lockers are projecting into the required 18-inch clear space required foraccessibility at entry doors to the classroom
s.5)
The building lacks proper signage.6)
Assistive listening device m
ay be required in the Library conference rooms.
Building B
– Student Center
The Student Center has tw
o occupancies. The main building serves as a cafeteria. The annex
building is counseling offices. Based on current functions, the building has num
erous accessibilitydeficiencies as follow
s:1)
Prim
ary building entrance to both to the cafeteria and the counseling offices is notcom
pliant. The cafeteria’s accessible entry is in the rear of the building which is not acceptable.
A ramp to the prim
ary entry is required. Entry to the counseling offices requires traversing
a walkw
ay that is greater than 1:20 and requires a ramp.
2)D
oors lack lever handles and will be required by D
SA
.3)
The building lacks proper signage.4)
Entry stairs to the C
afeteria require additional handrails due to the width of the stair.
Also, the striping of the treads required for the visually-im
paired is worn and needs to be
renewed.
5)In the C
afeteria, service counters are not accessible. The queue line railing spacing istoo narrow
and no turning width is provided.
6)The kitchen is not accessible for its em
ployees.7)
The building lacks accessible toilet facilities and the path of travel to a toilet in the nearestbuilding exceeds the 200 ft that is som
etimes granted on a case by case basis. D
SA w
illrequire toilet facilities.
8)The em
ployees toilet is in the basement and not accessible.
4
Building C
- Drinking fountains should be H
i-Low type; Fire E
xtin-guisher C
albinets are mounted too high; the Telephone B
ooth is notaccessible.
Building C
- Staff sink not accessible
Building C
- Transac-tion counter notcom
pliant
Building C
- No toilets are com
pliant and lack space to comply w
ithout expanding room size.
Building C
- Wheelchair seating needs to be
through, not just at the rear.
Building C
- No w
heelchair accessto the O
rchestra Pit.
Building C
- Stair railing not compliant;
no stair striping
Building C
- Dressing R
oomentry not com
pliant
Building C
– Auditorium
The Auditorium
is a 500 seat venue and is used extensively. It has a number of accessibility
issues that will need to be addressed. The lack of dispersed seating for the physically disabled w
ill bethe m
ost challenging of these issues that will need to be resolved. C
urrently, there are two accessible
seating available in the rear of the auditorium. B
ased on the seat count, DS
A w
ill require accessibleseating be provided at the front, m
iddle and rear of the auditorium. This w
ill result in the loss of some
seating and a required path of travel to be developed to the accessible seating. Due to the steep rake
of the seating and the location of the aisles, an exterior path of travel and chair lifts system m
ay need tobe considered. H
owever, D
SA w
ill need to be convinced that such a solution is reasonable and providesequal access.
Additional access issues are as follow
s:1)
The men and w
omen’s toilet are not accessible. A w
heelchair accessible stall needs to beinstalled to m
eet current requirements. This change w
ould result in the lost of an existing water
closet, if only the existing space was utilized. H
owever, C
hapter 29 of the California B
uildingC
ode requires that for the size of this facility, a minim
um of four w
ater closets are required in them
en’s room, and eight w
ater closets are required in the wom
en’s room. In the M
en’s restroom,
50% of the w
ater closets may be replaced by urinals. A
lthough there is another set of restrooms
on the lower floor, those restroom
s are not available to the occupants of the auditorium and
therefore may not be considered in the count by the review
ing agency. It is probable that theboundaries of the current restroom
s will need to be expanded significantly.
2)Stairs throughout the interior are non-com
pliant. Som
e stairs are lacking handrails on one sideor interm
ediate railings, some lacking proper extensions, and m
ost lacking proper contrastingstriping on the stair treads.
3)The tw
o drinking fountains in the lobby area are no longer compliant. C
urrent requirements call
for a hi / low fountain. In addition, since the fountain project m
ore than 4-inches from the w
all,guardrailing is required on each side of the fountains. A
n additional drinking fountain is locatedat the stage near the dressing room
. This fountain, if operational, would need to com
ply with the
same requirem
ents.4)
The pay telephone booth in the lobby is non-compliant. A
n accessible enclosure and guardrailing are required.
5)The auditorium
does not have an assistive listening system (A
LS) installed. A perm
anent ALS
is required with enough receivers to accom
modate 4%
of the seating capacity. ALS
signagew
ith need to be posted. Accom
modations w
ill be needed to house the equipment and charging
station.6)
Fire extinguisher cabinets are mounted too high through the building and w
ill need to be lowered.
7)Light sw
itches are mounted too high. Lighting revision w
ill trigger the requirement to low
ersw
itches in the areas of changes.8)
On the low
er floor, the two toilet room
s serve the dressing rooms, the A
dult Education O
ffices,and S
hipping and Receiving. These toilet room
s are not accessible and will need to be m
adeaccessible since the upper toilet room
s are unavailable when the auditorium
is not open. Thetoilet room
s will need to be expanded or converted to unisex toilet room
s if the occupant loadallow
s it.9)
The lower floor dressing room
s are not accessible. The hallway and the doorw
ay are too narrow,
without required door clearances. The counter sink is not com
pliant, lacking required clearanceand protection.
10)A
ccess to the Orchestra P
it requires traversing stairs, whether from
the auditorium side or from
the lower floor. If the O
rchestra Pit is used, access w
ill need to be provided.
5
6
7
8
9
10
11
12
13
14
15
3. FIRE / LIFE SA
FETY
Building A - E
ntry Doors at S
econd Floor
Building A - Stair 244
Building A - C
orridor
3. FIRE/LIFE-SA
FETY
A.
Background:
As w
ith accessibility, fire and life-safety is governed by the California B
uilding Code and is
enforced by the Division of the State A
rchitect (DS
A). U
nlike the accessibility regulations the fire andlife-safety regulations are spread throughout the C
ode; however, m
ost of the pertinent regulations arein C
hapters 5 and 10. There is no overarching life safety regulation like AD
AA
G for fire and life safety.
Life Safety is not an area w
here the School D
istrict, the design professional or DS
A w
ould comprom
ise;how
ever, there will be areas of negotiation about w
hat is acceptable given the fact that the existingbuildings m
ay be constructed differently from w
hat would be built today under current codes. N
onetheless,a prim
ary objective of the project, in addition to seismic safety and accessibility w
ill be to increase fireand life-safety at the schools.
B.
Summ
ary & A
nalysis
The three priority buildings at Piedm
ont High S
chool were also analyzed for fire/life safety
code compliance. These findings are sum
marized in A
ppendix B: C
ode Analysis, as w
ell as on thedraw
ings in this section. This report identifies deficiencies. The next phase of the project will offer
conceptual solutions to these deficiencies.O
f critical importance are construction type and allow
able floor areas; individual andcum
ulative occupancies and occupant loads, which determ
ine required exiting and area separations.
The SiteThere are three drivew
ays that come off of M
agnolia Avenue that provide access for the FireD
epartment. N
one are designated as fire lanes. We w
ill be meeting w
ith the Piedm
ont Fire Departm
entto review
the school for fire department access, as w
ell as any other concerns of the Fire Departm
ent.
Building
A - Quad B
uilding
The renovations of the Quad B
uilding in the mid 90’s m
itigated a number of fire and life safety
deficiencies. The corridors were brought up to the required one hour fire rating. The entire building
has fire sprinklers. How
ever, there remain a num
ber of fire and life safety issues that will need to be
addressed.S
ection 305.9 of the 2001 California B
uilding Code requires that all educational facilities
known as E
-occupancy, have a State Fire Marshal approved and listed fire alarm
system. A
lthoughthe Q
uad Building has a fire alarm
system w
ith manual pull station, it does not m
eet the current coderequirem
ents. The new w
ork will trigger the need to replace the existing system
.S
ection 1007.3.12 of the 2001 California B
uilding Code requires that all educational facilities
known as E
-occupancy have floor level exit signs with illum
ination at all corridors. The new w
ork will
trigger the need to add these exit signs. In addition, tactile exit signage is required at locationsidentified in S
ec. 1003.2.8.6.1.The tw
o pairs of exit doors on the north wall of the second floor do not m
eet minim
umrequired exit door w
idth of 3’-0". As m
entioned above, the door width w
as also an accessibilitydeficiency, too.
The Counseling O
ffices on the First Floor require a State Fire Marshal approved and listed
fire alarm system
or the hallway w
ill need to be a one-hour fire rated corridor. Since the Q
uadB
uilding will need a new
fire alarm system
due to its occupancy group, this issue should be a non-issue.
Stairwell N
o.244 does not meet the required stair w
idth per Sec. 1007.3.6. The shortfall in
width is 4-inches and the stairs are existing. D
SA m
ay allow this condition to rem
ain, especially sincethe building w
ill have fire sprinklers and new fire alarm
system.
16
Building B
- Cafeteria looking east
Building B
- Kitchen looking south
Building B
- Entry at C
onselors’ Offices
Building B
- Cafeteria looking w
est
Building C
- Shipping &
Receiving
Building C
- Adult
School E
ntrance
Building C
- Auditorium
seating
Building C
- View
of Stage
Building C
- Lobby
Building B
– Student Center B
uilding
Section 305.9 of the 2001 C
alifornia Building C
ode requires that all educational facilities (E-
occupancies), have a State Fire Marshal approved and listed fire alarm
system. A
lthough theStudent C
enter Building is an A
-3, assembly occupancy, it serves an educational com
munity and w
illbe subject to the requirem
ent of an E-occupancy based on S
ec 305.9.3. In addition, the annexbuilding houses counselor offices, an E
-occupancy. The existing fire alarm system
with m
anual pullstation, does not m
eet the current code requirements. The new
work w
ill trigger the need to replacethe existing system
.The C
ounseling Offices in the annex requires a State Fire M
arshal approved and listed firealarm
system or the hallw
ay will need to be a one-hour fire rated corridor. S
ince the Student Center
Building w
ill need a new fire alarm
system due to its occupancy group, this issue should be a non-
issue.O
ther deficiencies that will need to be address are the need for tactile exit signs and the
posting of room capacity.
Building C
– Auditorium
Building
Section 305.9 of the 2001 C
alifornia Building C
ode requires that all educational facilities (E-
occupancies), have a State Fire Marshal approved and listed fire alarm
system. A
lthough theA
uditorium B
uilding is an A-2, assem
bly occupancy, it serves an educational comm
unity and will be
subject to the requirement of an E
-occupancy based on Sec 305.9.3. The existing fire alarm
systemw
ith manual pull station, does not m
eet the current code requirements. The new
work w
ill trigger theneed to replace the existing system
.In the original construction draw
ings, the lower level w
as designated as accessory functionsof the auditorium
(i.e. dressing rooms, toilets, w
orkshop, workshop office, storage and holding area).
In our site review of the facility, w
e noted the lower level w
orkshop areas have been converted to anA
dult Education O
ffice and Shipping and R
eceiving Office and storage space. The change in
occupancy of these spaces to B-occupancy should have been done w
ith DS
A approved constructiondraw
ings. We have no draw
ings stamped by D
SA for these changes.
At this phase of the w
ork, we have no m
echanical or electrical consultants to assess thosesystem
s. How
ever, based on our observations, it appears that the Auditorium
Building does not have
emergency lighting as required by current code.
The Auditorium
Building is partially fire sprinklered. W
e will need to assess the adequacy of
the system, the adequacy of the coverage, and w
hether agencies having jurisdiction will require any
modifications or changes. In addition, the ceiling of the Stage area has tw
o smoke hatches. A
nassessm
ent of the adequacy of this system w
ill be needed. We noted that a m
ezzanine has beenadded in Storage R
oom 113. The new
mezzanine blocks adequate sprinkler coverage to the floor
area below the m
ezzanine. Extension of the sprinkler system
will be required, pending D
SA’s
decision of allowing the m
ezzanine to remain, since it appears it w
as done without D
SA
approvals.
17
18
19
20
21
22
23
24
25
26
27
4. STRU
CTU
RA
L TIER 2 R
EPOR
T
Seismic E
valuation of Three B
uildings at Piedm
ont High School, Piedm
ont Piedm
ont Unified School D
istrict
Prepared for m
urakami/N
elson Architects, Inc.
Oakland, C
A
Decem
ber 19, 2007
Prepared by R
. P. Gallagher A
ssociates, Inc. Structural E
ngineers O
akland,
i
Executive Summ
ary
Three buildings at P
iedmont H
igh School (Q
uad building, Student C
enter, and Alan
Harvey Theater) w
ere evaluated for life safety risk in a major earthquake. The evaluation
criteria used was A
SC
E S
tandard 31 “Seism
ic Evaluation of Existing B
uildings,” published in 2003 by the A
merican S
ociety of Civil E
ngineers. This document is the generally recognized
criteria for assessing the life safety risk of existing buildings.
R
esults of the evaluation indicate that the three buildings do not meet the life safety
criteria of ASC
E 31. The principal seism
ic deficiencies of each structure are summ
arized below:
Quad building – This building is com
prised of five separate structures. The original Quad
building and its addition, two of the five structures and both believed to be constructed in
the 1930’s, have very weak roof and attic diaphragm
s, and both do not meet A
SC
E 31 life
safety standards. Both are significant life safety risks. The library and library m
ezzanine m
eet AS
CE
31 criteria. The library addition does not because some of its steel
connections do not fully incorporate new steel design standards, but the risk to occupants
is not believed to be great.
Student C
enter – The Student C
enter does not meet A
SC
E 31 criteria. It has an overstressed
high roof diaphragm, and the connections of the roof to the w
alls are not sufficiently strong. It can be significantly dam
aged in an earthquake but is not believed to be a collapse hazard.
Alan H
arvey Theater – The Theater generally meets A
SC
E 31 life safety criteria, except that
some of the connections of the roof fram
ing to the large concrete columns are
overstressed. These and several other roof connections need to be strengthened. This structure is unlikely to collapse in a m
ajor earthquake.
The three buildings w
ere also surveyed for nonstructural hazards. The sprinkler piping in the original Q
uad building wings is not seism
ically braced and may fail in an earthquake.
Other concerns include broken roof tile that can becom
e a falling hazard and unanchored gas lines on roof of the Q
uad building. In general, tall bookcases and storage cabinets through out the three buildings are anchored, w
ith a few exceptions.
It is recom
mended that the buildings be seism
ically strengthened to correct the deficiencies found. The criteria of FE
MA
356 “Prestandard and C
omm
entary for the R
ehabilitation of Buildings” published by the Federal E
mergency M
anagement A
gency can be used. This is the generally recognized criteria for strengthening existing buildings.
If the tw
o older wings of the Q
uad building are to continued to be used prior to seismic
strengthening, the heavy roof tile should be removed and replaced w
ith a light-weight tem
porary roof as an interim
safety measure.
B
ased on structural considerations alone, we believe it is econom
ically feasible to strengthen the buildings and at the sam
e time preserve their basic functional and architectural
character. How
ever, the overall feasibility of this project remains to be evaluated during the
next, conceptual phase of the work.
28
ii
CO
NTEN
TS
Page
Executive S
umm
ary
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1. Introduction…
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2. E
valuation Criteria…
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3. Q
uad Building…
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4. S
tudent Center…
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5. A
lan Harvey Theater…
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6. N
onstructural Hazard S
urvey……
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7. S
umm
ary and Recom
mendations…
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8. R
eferences……
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1
1. Introduction
This report summ
arizes the seismic evaluation of three buildings at P
iedmont H
igh S
chool in Piedm
ont. The school is located at 800 Magnolia A
venue. The three buildings studied are the Q
uad building, the Student C
enter building, and the Alan H
arvey Theater. The purpose of the study w
as to assess the vulnerability of the buildings for life-safety risk in a major
earthquake.
C
onstruction of two of the buildings and part of the third (Q
uad building) was done under
the jurisdiction of the California D
ivision of State A
rchitect (DS
A) and occurred after passage of
the landmark 1933 Field A
ct by the California legislature. The dates of the construction of the
two original “w
ings” of the Quad building are unknow
n but are believed to be the 1930’s. Both
of these structures may have been review
ed by DS
A.
The Field Act required that the buildings be designed for seism
ic forces. Since
enactment of the A
ct, and particularly since the 1971 San Fernando, C
A earthquake, the state-
of-the art seismic design has im
proved substantially with contributions from
new research,
better materials, im
proved training of structural engineers, and knowledge gained from
investigations of earthquake dam
aged buildings. It is now recognized that m
any older buildings, even post Field A
ct California school buildings, are seism
ically vulnerable.
The evaluations sum
marized in this report represent an assessm
ent of the three buildings using the latest seism
ic evaluation methodology. The study consisted of a detailed
structural evaluation of each building. This included preparation of structural calculations and evaluation of the structural system
to withstand the im
posed seismic forces w
ithout collapse or creation of a serious life safety risk.
The evaluation presented also includes a survey of nonstructural hazards. The purpose
of this was to identity potential falling and other hazards that m
ay be triggered by a major
earthquake.
The report is organized as follow
s. The criteria used in the evaluation is described in S
ection 2. A description of each building and the results of the evaluation are presented in
Sections 3, 4, and 5, respectively, for the Q
uad building, the Student C
enter building, and the A
lan Harvey Theater. N
onstructural hazard are discussed in Section 6. S
ection 7 provides a sum
mary and recom
mendations.
29
2
2. Evaluation C
riteria
Building Structural System
s
The buildings w
ere evaluated using the criteria of AS
CE
Standard 31-03 “S
eismic
Evaluation of E
xisting Buildings” (R
ef. 1). This is the state-of-the-art criteria used for the seismic
evaluation of existing buildings. It is used to establish whether there is a significant life-safety
risk.
E
ach building was given a Tier 2 evaluation for the Life S
afety performance level using
the Linear Static P
rocedure (LSP
). This required a detailed seismic analysis of the building’s
structural system. In this approach, the ground shaking hazard at the site is first determ
ined, and then the building is evaluated for its ability to w
ithstand these motions w
ithout unacceptable behavior. The Tier 2 evaluation w
as recomm
ended in an earlier Tier 1 study performed for
Piedm
ont US
D by Janiele M
affei, Structural E
ngineer (Ref. 2).
Nonstructural C
omponents
N
onstructural elements and equipm
ent were also investigated. These w
ere evaluated in a site survey using the Tier 1 criteria of A
SC
E 31, supplem
ented by additional guidance developed by D
SA
and other state agencies (Ref. 3).
Earthquake Ground M
otions
E
arthquake ground motions for the site w
ere obtained from the seism
ic ground shaking m
aps found on the CD
-RO
M S
eismic D
esign Param
eters (Ref. 4). These ground shaking m
aps w
ere developed by the U.S
. Geological S
urvey under the National E
arthquake Hazards
Reduction P
rogram (N
EH
RP
). Ground m
otions at the site were determ
ined for the Maxim
um
Considered E
arthquake (MC
E). This represents an earthquake w
ith only 2-percent chance of being exceeded in 50 years (i.e., an earthquake w
ith a 2,500 year return period). At this
location, the MC
E has a peak ground acceleration of 0.77g; how
ever, only 2/3 of this level of m
otion (0.51g) is required to be used in the evaluations done under AS
CE
31. Site class D
(default class) w
as used.
The school is located approxim
ately 1 mile w
est of the Hayw
ard fault. This is a large fault and believed capable of a m
agnitude 7.0 or larger earthquake. This would produce very
strong shaking at the site.
Dem
and-Capacity R
atios
Results of the evaluation of each building are presented as dem
and to capacity ratios (D
/C). These are provided for the m
ain structural elements (i.e., structural m
embers and
connections) that make up the seism
ic force-resisting system of each building. A
D/C
ratio of 1.0 or less indicates that the elem
ent satisfies the AS
CE
31 criteria. Dem
and is the combined
earthquake and dead load force applied to a structural element, and capacity is the elem
ent’s usable strength. D
/C ratios greater than about 1.1 to 1.2 indicate a deficient elem
ent that may
need to be strengthened or replaced. Elem
ents with D
/C ratios of 2.0 or greater are considered
seriously overstressed. Generally, such large D
/C ratios indicate a serious deficiency unless
there are other structural elements present that can take up the slack w
hen the element w
ith the high D
/C ratio fails or is no longer effective.
3
3. Q
uad Building
3.1 Overview
of the Building
The Quad building (also know
n as Building A
) is composed of five separate structures
(see Figure 1). The original building (Figure 2), for which there are no draw
ings, was believed
built in the 1930’s. An addition to this building (Figure 3) w
as built a short time afterw
ards.
In the m
id-1970’s, the library was built. This is a separate structure located betw
een the w
ings of the original Quad buildings. This is the third of the five structures.
In the m
id-1990’s, the library addition (Figure 4) was constructed. This consisted of a
two-story building w
est of the library and a new m
ezzanine located in the library adjacent the east w
ing of the original building. These are the fourth and fifth of the five structures that com
prise the Quad building.
S
umm
arized below are descriptions of the five structures, a sum
mary of the results of
the evaluation of each, and a discussion of the results. The original Quad building is discussed
in Section 3.2. The Q
uad building addition is discussed in Section 3.3. The library is discussed
in Section 3.4, the library addition in S
ection 3.5, and the library mezzanine in S
ection 3.6.
3.2 Original Q
uad Building
Description. The original Q
uad building is essentially a concrete structure with a w
ood roof. It has 10 inch thick concrete w
alls and a floor system consisting of a 3 inch concrete slab integral
with 12 inch deep joists. The roof has conventional w
ood frame construction w
ith Spanish tile on
the mansards around the perim
eter and built-up roofing with gravel on the center portion. The
building is a partial two story structure about 42’ w
ide by 82’ long. The east side is one story, and the w
est side is two stories. Interior partitions and ceilings are plaster on w
ood studs or fram
ing. Foundations appear to be concrete strip footings.
The second floor ceiling has unusual construction. S
everal 18 inch deep I-beams span
transversely across the building. These support the ceiling joists. There are also two row
s of 10 inch deep I-beam
s spanning between the 18 inch beam
s. These support the two bearing
walls that support the m
iddle portion of the roof. Just above the joists are horizontal steel angles that laterally brace the I-beam
s at roughly their third points. These do not extend all the w
ay across the building (i.e., from Line 2 to Line 3), and consequently form
an incomplete
horizontal diaphragm system
.
E
xcept at one location in the roof, lateral forces in both directions are resisted by the concrete w
alls acting as shear walls. There is a straight sheathed, w
ood framed w
all on Line A
.5 between the roof and the attic level at the south end of the roof diaphragm
that serves as a w
eak shear wall. The roof diaphragm
consists of straight 1x6 wood sheathing (Figure 6). A
t the attic level, horizontal steel angle x-bracing, located just above the plane of the second floor ceiling, braces this level (Figure 7).
The building w
as inspected by structural engineers from our office on N
ovember 20,
2006 and again on February 22, 2007. No obvious structural distress or settlem
ent was noted.
In fact, the concrete walls of the building appear to be in excellent condition for their age.
30
4
As-built Inform
ation. Measured draw
ings were prepared by M
urakami/N
elson showing floor and
roof plans and wall elevations (R
ef. 5). Structural as-built inform
ation such as roof framing
mem
bers sizes and spacings, configuration of the horizontal steel bracing, and size and spacing of the concrete cross ties in the attic w
as obtained by our firm. This is sum
marized on the
structural “as-built” drawings (R
ef. 6).
D
uring the 2006 Decem
ber school break, a testing laboratory conducted exploration of the original Q
uad building and its addition. The purpose of this work w
as to obtain structural inform
ation for the Tier 2 evaluations. Information obtained included such things as the
thickness of concrete walls and floors, reinforcem
ent size and spacing, and details on the connection of the w
ood frame roof to the concrete w
all. This work is sum
marized in the
exploration report (Ref. 7).
Results of Evaluation. The original Q
uad building was found to have som
e very significant structural deficiencies and does not m
eet the Tier 2 life safety criteria. The principal problems
are the weak roof and attic diaphragm
s and the lack of an adequate transverse shear wall to
support the south end of the roof diaphragm.
The roof diaphragm
spans from Line A
.5 to Line F, a distance of 82 feet. There is an expansion joint in the roof along Line A
.5. Consequently, the only support for the south end of
the diaphragm (at Line A
.5) is the very weak straight sheathed shear w
all. Even considering
this very questionable wall as being effective, the D
/C ratio for shear in the transverse direction
for the roof diaphragm is 4.60. In the longitudinal direction it is 2.70. Figure 6 show
s diaphragm
D/C
ratios. In addition, the sill anchor bolts anchoring the roof to the tops of the concrete walls
are also significantly over-stressed with a D
/C of 1.37.
A
t the attic level, the diaphragm consists of horizontal steel angle x-bracing connected to
the transverse 18 inch deep I-beams (Figure 7). This is overstressed under transverse seism
ic forces w
ith a D/C
ratio of 3.42 in tension (controlled by bolt shear in the bolted connections at each m
ember end). In the longitudinal direction, because the horizontal x-bracing does not
extend from Lines 2 to 3 (and also from
Line 3 to 3.5), there essentially is no structural diaphragm
. The attic level diaphragm is im
portant because it transmits the out-of-plane seism
ic forces to the in-plane shear w
alls.
The second floor diaphragm
essentially meets criteria w
ith D/C
ratios in shear of 1.05 for the transverse direction and 0.18 for the longitudinal direction.
The w
ood “shear wall” in the attic on Line A
.5 is greatly overloaded with a D
/C ratio in
shear of at least 4.60, assuming the w
all is complete, w
hich it is not because of boards removed
for an access way and a duct. D
/C ratios for in-plane shears in the transverse and longitudinal
concrete shear walls are 1.18 and 0.32, respectively. The largest D
/C ratios for in-plane
bending in the wall-piers are 0.53 and 0.21 for the transverse and longitudinal shear w
alls, respectively.
U
nder out-of-plane forces, typical D/C
ratios are 0.28 at piers having 2-#6 boundary bars and 1.16 at the 10” thick w
alls that are reinforced with # 4 bars at 24” o.c. on each face.
Discussion of R
esults. The deficiencies found in both the roof and attic level diaphragms are
very serious. AS
CE
31 arbitrarily limits the spans of straight sheathed diaphragm
s (also known
5
as transverse sheathing) to 24 feet. The longitudinal span (for transverse forces) is 82 feet. The horizontal x-braced diaphragm
at the attic level is also greatly overstressed in the transverse direction w
ith a D/C
3.42. In the longitudinal direction, the attic diaphragm is
incomplete.
The straight sheathed shear w
all on Line A.5, w
hich appears to be a nonstructural wall,
is obviously very weak, and this leaves the south end of the diaphragm
essentially without
adequate support for transverse (E/W
) seismic forces.
To fix the problem
s, both the roof and attic level diaphragms need to be greatly,
strengthened. The roof could be sheathed with plyw
ood (plywood overlaid on the existing
straight sheathing) and the attic diaphragm can be strengthened by adding a new
horizontal steel bracing system
in both directions. To reduce roof, attic and floor diaphragm spans, a new
concrete shear w
all at Line B can be installed.
3.3 Addition to O
riginal Quad B
uilding
Description. The A
ddition has construction very similar to the original Q
uad building. It is a two
story structure about 34’ wide by 141’ long. There is a basem
ent mechanical room
at the west
end. No draw
ings are available for the addition. Information w
as obtained that indicates that this structure w
as designated Addition N
o. 1 and had DS
A A
pplication No. 1441. The tw
o structures (original Q
uad building and the addition) form an L-shape. There is a 5 inch
expansion joint between the structures. This occurs on Lines A
.5 and 3.5. There is also an expansion joist betw
een the addition and the library.
W
hen the addition was built, the roof of the tw
o structures was separated by an
expansion joint approximately on Lines A
.5. Lateral forces on the roof are resisted by a roof diaphragm
with 1x6 straight sheathing spanning the length of the addition. There is a w
ood fram
ed, straight sheathed wall that form
s a very weak “shear w
all” at roughly midspan of the
diaphragm. This w
as not considered in our analysis.
A
t the attic level there is a horizontal steel angle x-braced diaphragm that spans from
Line 2.5 to Line 9 (Figure 5). In addition, there are 19” deep x 14” w
ide concrete beams that
connect the tops of the three longitudinal shear walls on Lines A
, A.5 and B
.
B
elow the attic level, lateral forces in both directions are resisted by 10 inch thick
concrete walls acting as shear w
alls. These are relatively lightly reinforced. Interior walls are
plaster on wood stud. C
eilings are plaster on 1x boards spanning between the ceiling or floor
joists. The second floor consists of a 3 inch concrete slab on 12 inch deep joists spaced at 24” o.c. Foundations are believed to be strip footings under the concrete w
alls.
As-built Inform
ation. As-built inform
ation for addition was obtained at the sam
e time as for the
original building. See the discussion above the under the original Q
uad building.
Results of Evaluation. The Q
uad Addition does not m
eet the Tier 2 life safety criteria and has som
e very significant deficiencies. The principal problems are the sam
e as for the original building. The roof and attic diaphragm
s are very weak, and there is a lack of interior transverse
shear walls to reduce diaphragm
span and load.
The roof diaphragm
has D/C
ratios for shear of 13.20 in the transverse direction and 3.97 in the longitudinal direction (Figure 6). W
ith a longitudinal span of 141’, the diaphragm
31
6
greatly exceeds the arbitrary 24’ limit of A
SC
E 31 for diaphragm
s with straight sheathing. The
aspect ratio of 4 to 1 also exceeds the 2 to 1 limit to A
SC
E 31.
A
t the attic level, the horizontal steel X-bracing has a D/C
of 11.1 in tension under transverse seism
ic forces (Figure 7). This indicates that there is essentially no effective diaphragm
at the attic level. This is a major deficiency.
The second floor diaphragm
, which spans 102’ betw
een the shear walls on Lines 2.5
and 8, has a D/C
of 1.52 in shear. This occurs in the 3 inch thick concrete slab.
M
aximum
in-plane shears in the transverse and longitudinal shear walls have D
/C ratios
of 1.66 and 0.75, respectively. The largest D/C
ratios for in-plane bending in the wall-piers for
the transverse and longitudinal shear walls are 0.29 and 1.15, respectively.
U
nder out-of-plane forces, typical D/C
ratios are 0.25 at piers having 2 # 6 boundary bars and 1.16 at the 10” thick w
alls that are reinforced with # 4 bars at 24” o.c. on each face.
Discussion of R
esults. The results of the evaluation indicate a serious problem caused by the
weak roof and attic diaphragm
s. With the lack of a functioning diaphragm
at the attic level, the only m
echanisms to resist the roof from
moving transversely (N
/S) in an earthquake are the
three longitudinal concrete walls on Lines A
, A.5 and B
in weak axis bending and the three
transverse wood stud and plaster partitions located betw
een the shear walls on Lines 2.5 and 8.
Unfortunately, these transverse w
alls lack sufficient strength to act as effective shear walls.
S
imilar to the original building, the roof and attic diaphragm
s will need to be greatly
strengthened. This can be done by adding plywood sheathing over the existing straight
sheathing on the roof, installing new horizontal steel bracing at the attic level, and building a
new transverse concrete shear w
all at Line 5 (by replacing an existing plaster and wood stud
partition).
3.4 Library
Description. The library is a single story high-bay structure about 72’ by 67’ in plan (R
ef. 8). C
onstruction consists of six 3’-0” square reinforced concrete columns supporting a w
ood frame
roof. Roof fram
ing consists of large glulam beam
s supporting 3x8 purlins overlain with 3/4 inch
plywood sheathing.
The six large concrete colum
ns are cantilevered from their grade beam
s, and these com
prise the lateral force-resisting elements of the structure. The colum
ns have ductile detailing w
ith closely spaced column ties, and this is a very good seism
ic feature. The large grade beam
s that serve as foundations are also designed to resist the mom
ents imposed on
them by the cantilevered colum
ns. The roof sheathing serves as a horizontal diaphragm. The
library is separated from the tw
o original wings by 2-inch w
ide expansion joints, and the library addition w
ith a 4-inch joint.
Results of Evaluation. The library structure m
eets the life safety requirements of A
SC
E 31. In
general, the principal structural elements are w
ell with the A
SC
E 31 lim
its.
M
aximum
D/C
ratios for the roof diaphragm in shear are 0.60 and 0.33 for the N
/S and
E/W
directions, respectively. The large 3 foot square concrete columns on Line 4 have D
/C
7
ratios of 0.32 in bending and 0.11 in shear. The two colum
ns in Line E have D
/C ratios of 0.26
in bending and 0.09 in shear. Foundation grade beams are w
ell within allow
ables.
C
onnections between the roof and the large colum
ns are more highly stressed but w
ithin allow
able limits. The connection on Lines 4 and E
have D/C
ratios of 1.00 and 0.74, respectively.
Discussion of R
esults. The library meets the A
SC
E 31 life safety criteria, and seism
ic strengthening is not required. It should be noted that due to the flexibility of the cantilevered colum
ns, pounding between the library and the tw
o original wings of the Q
uad building may
occur during strong ground motion. This w
as not evaluated in the Tier 2 studies.
3.5 Library Addition
Description. The library addition consists of a tw
o-story steel frame structure about 40’ by 70’ in
plan (Ref. 9) built in the m
id-1990’s. The second floor consists of light-weight concrete fill on 18
gage metal deck. The roof consists of 18 gage m
etal deck supported by steel beams. E
xterior w
alls are metal stud and stucco. Interior w
alls are gypsum board on m
etal stud. Foundations consist of a system
of grade beams and short drilled piers. There is a 4 inch w
ide expansion joint betw
een the library addition and the library, and between the library addition and the Q
uad building.
Lateral forces in the N
/S direction are resisted by steel m
oment fram
es along Lines 7 and 9. The beam
-column connections at the second floor level are strengthened by flange
cover plates and doubler plates. Lateral forces in the E/W
direction are resisted by chevron braced fram
es along Lines C.1, D
, and F. The braced frames along Lines C
.1 and F extend to the roof level. The braced fram
e along Line D extends only to the second floor level.
Benchm
ark Building S
tatus. AS
CE
31 states that buildings meeting the building code provisions
for new construction after certain dates can be considered to m
eet life safety requirements. The
specific edition (date) of the building code provisions varies depending on the type of construction. A
SC
E 31 requires that buildings be review
ed to verify that they were designed,
detailed, and constructed in conformance w
ith the applicable benchmark code provisions.
For steel braced frame construction, the benchm
ark code for new construction is the 1988 U
BC
. S
ince the library addition was required to m
eet the provisions of the 1995 CB
C, the braced
frame system
qualifies as a “benchmark building”.
For steel mom
ent frame construction, the A
SC
E 31 benchm
ark code for new construction is the
1994 UB
C as m
odified by emergency provisions for steel m
oment fram
es issued in Septem
ber 1994. The latter required tests of the beam
-column connections. A
t the time that the building
was designed, D
SA
required conformance w
ith IR 27-8 in place of such tests. There is no
evidence of connection tests in the DS
A files w
e reviewed.
Results of Evaluation. The braced fram
e along Line C.1 w
as spot checked for conformance
with the 1988 U
BC
. This review included a check of the colum
n and diagonal mem
ber sizes and certain key connections. These review
s indicated that the braced frames w
ere designed to m
eet the 1988 UB
C requirem
ents.
The m
oment fram
es were evaluated using the Tier 2 requirem
ents of AS
CE
31. D/C
ratios for drift are 0.56 and 0.64 at the second floor and roof, respectively. D
/C ratios for various
32
8
connections at the second floor were calculated. In general, these are low
. For example,
maxim
um D
/C ratios for the beam
column-connections at Lines 7/C
and 7/D are 0.42 and 0.40,
respectively. Panel zone shear at these sam
e connections is 0.17 and 0.11, respectively. C
onsequently, we believe the m
oment fram
es were conservatively designed. A
review of the
design drawings and the D
SA
files during construction indicates several specific locations of concern as follow
s:
(1) There are several locations in the m
oment fram
es where significant changes in flange
cross section occur at or directly next to the beam plastic hinge locations.
(2) The shear connections betw
een the sloping upper roof and the main roof diaphragm
are not show
n on the drawings.
(3) The construction files indicate significant blockouts in the foundation grade beam
s at key locations, including directly below
the anchorage of one braced frame. It is not
clear if the brace frame is anchored to the top of the grade beam
or the top of the floor slab.
Discussion of R
esults. While the library addition essentially m
eets AS
CE
31 life safety criteria and does not appear to pose any significant risk, there are aspects of its construction that should be verified. A
Tier 3 evaluation of the specific areas of concern listed above, and of the beam
column connection of the m
ovement fram
es should be done.
3.6 Library Mezzanine
Description.
The mezzanine is a one-story braced steel fram
e structure approximately 20’ by
70’ in plan (Ref. 9). It w
as built at the same tim
e as the library addition (mid-1990’s). The top of
the mezzanine is at the sam
e level as the second floor of the Quad building. S
pace on the m
ezzanine floor is occupied by the teacher’s lounge and resources rooms. Interior w
alls are gypsum
board and metal stud. The floor consists of 18 gage m
etal deck with light-w
eight concrete fill. Foundations consist of short drilled piers. There is a 4 inch expansion joint betw
een the mezzanine and the Q
uad building. The structure appears to be designed under the provisions of the C
BC
that correspond to the 1991 UB
C.
Lateral forces in both directions are resisted by the steel chevron bracing. Transverse
bracing consists of three bays of 4x4 steel tube braces, and longitudinal bracing consists of two
bays of 5x5 steel tube braces.
Results of Evaluation. The structural system
of the mezzanine w
as reviewed and accepted by
DS
A in June 1996. S
pot checks of certain connections indicated that the braced frames w
ere designed in accordance w
ith the 1988 UB
C. N
o specific areas of concern were found.
Discussion of R
esults. The library mezzanine m
eets the life safety criteria of AS
CE
31, and seism
ic strengthening is not required.
9
Figure 1 – Roof plan show
ing the five structures that make up the Q
uad building. The m
ezzanine is located within the library.
33
10
Figure 2 – One-story east side of the Q
uad building. Note the heavy S
panish tile roof.
Figure 3 – Two-story south side of the Q
uad building.
11
Figure 4 – The west entrance to the Q
uad building is the Library Addition.
Figure 5 – View
of Quad building attic show
ing some of the horizontal steel bracing used in the
attic level diaphragms.
34
12
Figure 6 – Roof plan of the Q
uad building showing dem
and to capacity ratios (D/C
) for the roof diaphragm
s.
13
Figure 7 – Attic plan of Q
uad building showing dem
and to capacity ratios (D/C
) for attic diaphragm
tension bracing.
35
14
4. Student C
enter
Description
The Student C
enter (Building B
) was built in the late 1930’s. O
riginally, it was the school
library. Later it was converted to its present use. The m
ain, high roof portion of the building is one story and 43’ x 86’ in plan. There is a m
ezzanine across the east end of the high roof portion. The area below
the mezzanine has been enclosed to create a snack bar. There is a
basement area located below
the first floor across the east end of the building. There is a low
enclosed storage area across the west end of the high roof area. O
n the west side of the
building is the low roof one-story area that houses the S
pecial Education O
ffice. This is 28’ x 39’ in plan and is structurally connected to the high roof portion of the structure.
C
onstruction consists of 8 and 10 inch thick reinforced concrete walls w
ith wood fram
e roofs. The roof of the high-bay portion is supported by five heavy tim
ber trusses with 8x8 cased
purlins spanning between trusses. There are 4 x6 subpurlins at 2’- 0” o.c. resting on the 8x8
purlins. The roof trusses are supported on concrete pilasters which are part of the north and
south walls of the high roof area. The roof of the S
pecial Education Office consists of 2 x10
rafters at 16” o.c. Both high and low
roofs are sheathed with 1x6 diagonal sheathing.
The upper level w
indows on Line 1 (north side of the building) have been infilled. There
is no information on the nature of this infill. It w
as assumed that the infill consisted of w
ood fram
ing with exterior stucco and interior gypsum
board, however this needs to be verified.
Lateral forces in both directions are resisted by the concrete w
alls acting as shear walls.
The pilasters on Lines 3 and 5 (see Figure 10) of the north and south walls of the high roof area
are rigidly connected to large grade beams located below
the main floor. This creates tw
o lateral force-resisting fram
es that help to resist seismic forces in the north-south direction. The
heavy grade beams and the provision of extra reinforcing in these pilasters indicates that such
support was intended by the original designer.
Foundations consist of reinforced concrete strip footings located all around the building.
At the tw
o transverse frames, the grade beam
s are relatively large.
A
site visit and inspection of the construction was m
ade by two structural engineers from
our office on N
ovember 20, 2006. In general, the building w
as found to be in good structural condition. N
o signs of settlement or structural deterioration w
ere noted.
B
oth the original architectural and structural drawings for the building (R
ef. 10) were
available, and these were used in the evaluation.
Figures 8 and 9 show
views of the building, and Figure 10 show
s the floor plan. Figure 10 is also used to show
demand to capacity ratios (D
/C) for in-plane shear forces in the principal
shear walls.
15
Results of the Evaluation
The building does not m
eet the life safety requirements of A
SC
E 31. A
number of
structural deficiencies were found, and these are discussed below
.
U
nder transverse (N/S
) seismic forces, the high roof diaphragm
has D/C
ratios in shear of 1.34 to 1.60 depending on analysis assum
ptions. For what m
ay be the most realistic
assumption, w
e considered plastic hinges to form at the base of the pilasters of the tw
o transverse fram
es (on Lines 3 and 5). This reduced the amount of shear carried by diaphragm
, and gave the low
er value (1.34). The sill bolts connecting the wood roof to the top of the
concrete walls are also overstressed in shear w
ith D/C
ratios of 3.03 to 3.61 under transverse forces, and 1.48 under longitudinal forces.
The low
roof diaphragm over the S
pecial Education O
ffice has a maxim
um D
/C ratio of
0.80 in shear. The sill bolts along the north wall of this office are deficient w
ith a D/C
of 1.80. The sill bolts along the other perim
eter walls of the S
pecial Education O
ffice are not shown on
the original drawings. It is likely that these bolts are also deficient.
The draw
ings indicate that the roof and ceiling joists of the low roof are set into pockets
in the north and south perimeter w
alls. In the past, this type of construction has lead to decay dam
age to the joist ends. The joists should be examined for the possibility of such dam
age.
The D
/C ratios for shear w
alls are indicated on Figure 10. The shear walls are adequate
for in-plane shear forces. D/C
ratios for bending in the wall piers under in-plane seism
ic forces vary from
1.39 to 1.06.
O
ut-of-plane seismic forces on the concrete w
alls cause problems in several places.
The concrete reinforcing in the east and west w
alls of the high roof area (Lines 1 and 7 ) are significantly overstressed w
ith D.C
ratios of 2.59 and 2.89, respectively. Anchor bolts for the
main roof trusses are over stressed in shear w
ith D/C
ratios of 1.31 to 1.33. Anchorage of the
8x8 purlins to the high roof end walls is overstressed w
ith D/C
ratios of 1.16 to 1.46.
In the low
roof portion, straps anchoring the 2 x10 rafters to the concrete walls at every
third rafter are overstressed in tension with D
/C ratios of 2.16 to 2.65 under N
/S forces. U
nder E
/W forces, the anchorage detail used utilizes cross-grain bending in the w
ood ledgers. This is an extrem
ely weak connection w
ith essentially no strength. Therefore, these walls are
considered to have virtually no anchorage to the low roof diaphragm
.
Discussion of R
esults
The principal problems are the overstressed roof diaphragm
and the inadequate anchorage of the concrete w
alls to both the high and low roofs.
The overstressed high roof diaphragm
can be fixed by adding plywood sheathing over
the existing 1 x 6 diagonal sheathing. Improvem
ent of the wall-roof connections w
ill require installation of new
, stronger anchors or reinforcement of the existing connections. An
alternative procedure for the high roof area would be to add horizontal steel bracing in the plane
of the bottom chords of the roof trusses. S
uch bracing could prevent overstress in the high roof diaphragm
and strengthen the wall-roof anchorage at the sam
e time.
36
16
Figure 8 – View
of the Student C
enter building. The high roof portion was originally the school
library. The low roof portion on the right houses the S
pecial Education O
ffices.
Figure 9 – Rear (south side) of the S
tudent Center. The original w
indows on the north side
have been infilled (see Figure 8).
17
Figure 10 – Floor plan of the Student C
enter. Dem
and to capacity ratios (D/C
) for the principal shear w
alls are also indicated.
37
18
5. A
lan Harvey Theater
Description
The Alan H
arvey Theater (Building C
) was built in the m
id-1970’s. It is largely a one-story high roof structure w
ith lobby, projection room, and a large auditorium
/theatre area that cover m
ost of the building’s footprint. There is a partial basement at its w
est (stage) end. The low
er portion houses the Piedm
ont Adult S
chool, and the stage and backstage area is directly above. O
verall building dimensions are 81’ x 135’ in plan.
C
onstruction is complex w
ith a wood fram
e roof supported on large glulam beam
s, that in turn are supported on 3’- 0” square reinforced concrete colum
ns at the middle of the building
and wood fram
e bearing walls at the ends. The roof is sheathed w
ith 3/4-inch plywood w
hich is heavily nailed in som
e locations.
Lateral forces in both directions are resisted by the plyw
ood sheathed roof diaphragm
connected to the wood shear w
alls and the concrete columns that are cantilevered from
large foundation grade beam
s. In the transverse (N/S
) direction, there are large plywood shear w
alls on Lines 1 and 5 and cantilevered concrete colum
ns on Lines 2 and 3. Longitudinal (E/W
) seism
ic forces are resisted by the cantilevered concrete columns on Lines A
and B. It should be
noted that some of the theater’s large concrete colum
ns support large gravity forces, but these are not a part of the lateral force-resisting system
.
A
rchitectural and structural drawings for the original construction (R
ef. 11) were
available and were used in our evaluations. The original building construction quality is
excellent. The theaterdoes not appear to have had any significant modifications or additions to
the original construction.
The trellis on the north and south sides of the auditorium
, which is connected to the
theater structure, was investigated as part of the Tier 2 evaluation. This is supported by
cantilever pipe columns em
bedded in the ground. The portion of the trellis not supported by the pipe colum
ns bears on and is secured to the 4x16 timber beam
s projecting from the roof. W
e did not investigate the portion of the trellis east of the auditorium
as this is a separate structure.
O
n Novem
ber 20, 2006, two structural engineers from
our office toured the building and exam
ined the construction. In general, the structure appears to be in good condition. No signs
of any structural deterioration or settlement w
ere noted. How
ever, there is some visible w
ood rot on the equipm
ent screen on the roof and on some m
embers of the w
ood trellis around the theater.
Figures 11 and 12 show
views of the building, and Figure 13 provides a floor plan.
Dem
and to capacity ratios (D/C
) for the concrete piers and shear walls are also given on Figure
13.
Results of the Evaluation
The theater does not meet the A
SC
E 31 life safety criteria, but the deficiencies found are
not major, although som
e strengthening should be done. The principal concerns are the connection of the roof to the tops of the concrete colum
ns. This and other results are discussed below
.
19
The three roof diaphragm
s span between Lines 1 and 2, 2 and 3, and 3 and 5.
Diaphragm
s shears are within lim
its with D
/C ratios of 0.79, 0.82 and 0.30, respectively. C
hord D
/C ratios are 0.70 for transverse seism
ic forces, and 1.19 to 2.83 for longitudinal forces, the latter because the details or locations of the chord splices are not specifically show
n on the draw
ings. The bolted collector connections that interconnect the three glulam beam
s on Line 2 are overstressed w
ith D/C
ratios of 1.74.
Transverse (N
/S) seism
ic forces are carried by plywood shear w
alls and the large cantilevered concrete colum
ns. The plywood shear w
alls on Lines 1 and 5 have D/C
ratios of 0.91 and 0.67, respectively. The cantilever concrete colum
n and grade beam system
on Line 2 has m
aximum
D/C
’s of 0.39 in shear and 0.57 in bending. The columns on Line 3 have
maxim
um D
/C’s of 0.18 in shear and 0.23 in bending. G
rade beams are w
ithin allowables.
Longitudinal (E
/W) forces are resisted by the cantilevered colum
n and grade beam
systems on Lines A
and B. M
aximum
D/C
ratios for the columns are 0.30 in shear and 0.38 in
bending. Grade beam
s are within allow
ables.
The trellis on the north and south sides of the auditorium
cantilever from the structure on
4x16 timber beam
s. A sm
all portion of the trellis is supported by pipe columns, encased in
stucco enclosures, that are embedded in the ground. The cantilevered pipe colum
ns supporting the trellis and the connections of the trellis to the theater roof m
eet AS
CE
31 criteria.
Discussion of R
esults
Fortunately, the large concrete columns and grade beam
s that provide the primary
lateral force resistance of the theater have adequate reinforcing and ductile detailing. These conform
to the AS
CE
31 criteria and require no strengthening. Som
e of the roof connections including those that secure the roof to the tops of the colum
ns and the collector connections on Line 2 w
ill require strengthening to meet life safety perform
ance levels.
38
20
Figure 11 – South S
ide of the Alan H
arvey Theater.
Figure 12 – Southw
est corner of Alan H
arvey Theater. Wall on left is a stucco w
all and not a plyw
ood sheathed shear wall.
21
Figure 13 – Floor plan of the Alan H
arvey Theater. Dem
and to capacity ratios (D/C
) for the shear w
alls and concrete columns are also indicated.
39
22
6. N
onstructural Hazard Survey
Survey Methodology
This section describes the survey conducted for nonstructural hazards and presents the results. The purpose of the survey w
as to identify potential falling and other hazards.
N
onstructural components consist of things that are brought into a building after it has
been constructed (e.g. , furnishings, bookshelves, and building contents) as well as item
s that w
ere installed when the building w
as built (e.g. , mechanical and electrical equipm
ent and fixtures, ceilings, and partitions). These can becom
e hazards when they break, fall, slide or
overturn. When this happens they can cause injury, block exits, and create secondary hazards
such as chemical spills, gas leaks and postearthquake fires.
A
nonstructural hazard survey of the three buildings was done using A
SC
E 31 Tier 1
procedures. The Basic, Interm
ediate and Supplem
ent Nonstructural C
omponent C
hecklists w
ere used. The survey involved a room-by-room
inspection of each building by a structural engineer experienced in seism
ic design. The survey was conducted on D
ecember 18, 19 and
20, 2006.
Tables 1, 2, and 3 sum
marize results for the Q
uad building, Student Center, and A
lan H
arvey Theater, respectively. The tables identify the items exam
ined, the estimated
vulnerability of the item, and observations about each. The survey w
as entirely visual, and no draw
ings were review
ed or calculations prepared. The levels of vulnerability used are defined as follow
s: Vulnerability
Characteristics
High (H
) N
oncompliant under A
SC
E 31 Tier 1
procedures. Possesses little or no seism
ic resistance; item
may break, fall, slide or
overturn during strong shaking. High
probability of damage under strong shaking.
May cause injury to persons in vicinity.
Moderate (M
) P
ossesses some seism
ic resistance, but not as m
uch as an item rated low
.
Low (L)
Com
pliant under AS
CE
31 Tier 1 procedures. P
ossesses good seismic resistance, should
resist moderate shaking w
ithout damage. Low
probability of dam
age under strong shaking.U
nlikely to cause injury to persons in vicinity.
Building C
ontents on Tables and Shelves
In addition to the survey results given in Tables 1, 2 and 3, it should be noted that in
virtually all areas of the school there are unrestrained contents. These include such things as stored m
aterials and books on shelves, and computer m
onitors on desks. While these are a
threat to fall to the floor and may result in econom
ic loss, they are generally not considered
23
serious life-safety-hazards. Exceptions include the unsecured com
puters and monitors stored
on the tops of shelves in the library storage room.
Bookcases and Storage C
abinets
There are a number of bookcases and storage cabinets located throughout the school.
The great majority of these are secured to w
alls and are unlikely to overturn, although contents m
ay fall out. A few
cabinets and bookcases are free-standing and unanchored. Those over 4 feet tall w
ith height to depth ratios of 3.0 or greater are considered a hazard to overturn (Refs. 1
and 3).
File Cabinets
There are a number of file cabinets located throughout the three buildings. V
irtually all of these are four draw
er cabinets with locks on the draw
ers. There are a few cabinets w
ithout draw
er locks, and these are a definite hazard to overturn when the draw
ers shift outward.
These were rated as high risk (H
) because of the overturning hazard.
M
any file cabinets are situated where they are a low
risk of injury to persons in the vicinity or are “w
edged in” or otherwise placed such that it is very unlikely that they w
ill overturn. The A
SC
E 31 Tier 1 S
upplemented N
onstructural Checklist requires that “file cabinets arrange
in groups shall be attached to one another.” This requirement, how
ever, is for the Imm
ediate O
ccupancy (I/O) perform
ance level. None of the file cabinets w
e observed were connected
together.
Emergency G
as Shutoff
The buildings have gas lines that supply gas to heaters, oven/ranges, and boilers. We
were unable to observe m
ost lines because they are concealed. Although tw
o of the buildings (Q
uad building and Alan H
arvey Theater) have fire sprinklers, it would be desirable to install (if
not already done) an earthquake-activated gas shutoff valve at the PG
&E
meter. This w
ould autom
atically shutoff the flow of gas and could prevent a postearthquake fire.
40
24
Table 1 – Nonstructural Survey R
esults for the Q
uad Building (B
uilding A)
ItemV
ulnerabilityC
omm
ents
Roof
1. C
arrier HV
AC
unit AC
-1 L
Largest unit on roof. Anchored,
flexible gas line.
2. Intercity A
/C units C
U-5 and C
U-6
L Tw
o of these both anchored.
3. C
arrier HV
AC
unit AC
-4 L
Medium
sized unit. Anchored,
flexible gas line.
4. C
arrier HV
AC
unit AC
-2 L
Anchored, flexible gas line.
5. Intercity A
/C units C
U-7 and C
U-8
L S
mall units, anchored.
6. C
arrier HV
AC
unit AC
-3 L
Anchored, flexible gas line.
7. N
atural gas line H
Line is not anchored to roof and therefore does not m
eet the A
SD
E 31 Tier 1 criteria. It does
have a flexible connection over the expansion joint betw
een the library building and original Q
uad building.
8. R
oof tile L-H
Individual tiles on sloped portion of roof are w
ired to nails in 1 x 6 sheathing and considered low
risk (L). S
ome cap tiles are
broken and loose, and these are potentially falling hazards and rated high risk (H
).
25
ItemV
ulnerabilityC
omm
ents
Attic (of original 1930’s buildings)
1.
Sprinkler piping
H
Lines range from 1” to about 3” in
diameter. Long straight run in
Addition N
o. 1 has Victaulic
couplings and is not braced. In general, sprinkler piping lacks seism
ic braces.
2. D
ucts/fans U
nknown
Various sm
all ducts connecting to roof H
VA
C units w
ith possible fans/blow
ers inside. Difficult to
assess, but these do not seen to be a significant hazard.
Classroom
39
1. Fluorescent light fixtures
L C
eiling-mounted
2.
TV
L-M
Wall-m
ounted, appears to be engineered, TV
on swivel.
3.
File cabinets L-M
Tw
o 4 drawer units, not
restrained but not big hazard.
Classroom
38
1. Fluorescent light fixtures
L C
eiling-mounted
2. TV
L-M
W
all-mounted, appears to be
engineered, TV on sw
ivel.
3. File cabinets
L-M
Three 4 drawer units
4.
Bookcase
M-H
A
nchored to wall on only one
side. Needs better anchoraged.
R
ooms betw
een Room
s 36 and 37
1. Fluorescent light fixtures
L C
eiling-mounted
2.
Prefab steel shelving
H
Unrestrained unit 87” H
x 18”D.
H/D
= 4.8
3. A
PC
UP
S
H
Unrestrained sm
all unit on top of steel storage cabinet
41
26
ItemV
ulnerabilityC
omm
ents
4.
Steel storage cabinet
L-M
Unrestrained unit 72” H
x 36” W x
24” D. H
/D = 3.0
5.
Storage shelf
M-H
U
nrestrained L-shaped unit.
6. B
ookcase H
U
nrestrained unit 72” H x 78” W
x 11” D
. H/D
= 6.5
Classroom
37
1. Fluorescent light fixtures
L C
eiling-mounted
2.
TV
L-M
Wall-m
ounted, appears to be engineered, TV
on swivel.
3.
Bookcase
L 6’ high unit secured to w
all.
4. B
ookcase H
U
nrestrained unit 60” H x 36” W
x 11” D
. H/D
= 5.5
Classroom
36
1. Fluorescent light fixtures
L C
eiling-mounted
2.
TV
L-M
Wall-m
ounted unit, appears to be engineered, TV
on swivel.
3.
File cabinets L-M
Tw
o 4 drawer units
C
lassroom 35
1.
Fluorescent light fixtures L
Ceiling-m
ounted
2. TV
L
Wall-m
ounted unit, appears to be engineered, TV
on swivel.
C
lassroom 34
1.
Fluorescent light fixtures L
Ceiling-m
ounted
2.
TV
L W
all-mounted unit, appears to be
engineered, TV on sw
ivel.
3. B
ookcase H
U
nrestrained unit 64” H x 32” W
x 10½
” D. H
/D=6.1
27
ItemV
ulnerabilityC
omm
ents
4.
File cabinet L-M
4 draw
er unit.
Classroom
33
1. Fluorescent light fixtures
L C
eiling-mounted
2.
TV
L-M
Wall-m
ounted, appears to be engineered, TV
on swivel.
3.
TV (m
obile) M
-H
TV on m
obile stand is unrestrained and can fall off.
4.
File cabinet H
S
ingle 4 drawer file cabinet
without locks on draw
ers, can easily tip over.
5.
Bookcase
L W
all-mounted
C
orridor at Upper Level
1.
Fluorescent light fixtures L
Ceiling-m
ounted
2. Lockers
L M
any of these apparently secured to w
alls.
3. W
indows at stair landing
Unknow
n Three panes high, m
ay be ordinary glass.
4.
Window
s in corridor L
Wire glass
Custodian C
loset (Upper Level)
1. Fluorescent light fixtures
L C
able-hung
2. E
lectrical panels L
Secured to w
all.
3.
Transformer
L S
ecured to unistrut frame that is
secured to wall.
4.
Supply shelving
M-H
U
nrestrained tall unit
5. W
ater heater L
Short gas unit, strapped to w
all.
42
28
ItemV
ulnerabilityC
omm
ents
Faculty Lounge ( Upper Level)
1. Fluorescent light fixtures
L C
able-hung
2. O
ven range M
U
nrestrained electric unit.
3. R
efrigerator M
U
nrestrained.
Xerox Room
1. Fluorescent light fixtures
L C
able-hung
2. Xerox m
achines L-M
Tw
o large units. Both are
unrestrained, but unlikely to overturn.
Classroom
32
1. Fluorescent light fixtures
L C
able-hung
2. M
etal storage cabinet H
U
nrestrained 66” D x 24” W
x 18” D
unit. H/D
=3.7.
3. M
obile TV stand and TV
H
U
nrestrained
4. H
eater L
Located in closet, well anchored.
Classroom
31
1. Fluorescent light fixtures
L C
able-hung
2. B
ookcase H
U
nrestrained unit 84”H x 48” W
x 9” D
. Fastener pulled out of wall.
H/D
= 9.3
3. M
etal storage cabinet M
-H
Unrestrained unit 72” H
x 36” W x
18” D. H
/D = 4.0.
4.
File cabinet H
W
ood 4 drawer file cabinet
without draw
er locks.
5. File cabinet
L-M
4 drawer legal size cabinet w
ith draw
er locks.
6. H
eater L
Located in closet and well
anchored.
29
ItemV
ulnerabilityC
omm
ents
Classroom
30B
1. Fluorescent light fixtures
L C
able-hung
2. B
ookcase H
U
nanchored unit 72” H x 42” W
x 9” D
. H/D
= 8.0
3. S
torage cabinet L
Secured to w
all, 7’ high.
4. B
ookshelf (wall m
ounted) L
Two of these, both secured to
wall
5.
File cabinet L
4 drawer unit w
ith locks.
Classroom
30A
1.
Fluorescent light fixtures L
Cable-hung
2.
Bookcase
L Tw
o wall-m
ounted units.
3. File cabinets
L-M
Two 4 draw
er units with locks.
C
orridor at Lower Level
1.
Fluorescent light fixtures L
Ceiling-m
ounted
2. Lockers
L S
ecured to walls
3. M
ain entryL
Overhead glass is tem
pered.
Classroom
30
1. Fluorescent light fixtures
L C
able-hung
2. TV
L-M
W
all-mounted, also has tw
o restraining cables.
3.
Bookcase
H
Unrestrained unit 60” H
x 38” W x
12” D. H
/D= 5.0
4.
Bookcase
H
Unrestrained unit 61” H
x 27½”
W x 12½
” D. H
/D= 4.9
43
30
ItemV
ulnerabilityC
omm
ents
Library
1. Fluorescent light fixtures
L Three row
s of these, cable hung.
2. Free standing bookcases
L-M
Nine units anchored to floor. 91”
H x 22½
” D.
3.
Bookcases against w
all L
Secured to w
all
4. B
uilt-in bookcases L
5. S
mall fluorescent light fixtures
L C
able hung fixtures. These are located in sm
all rooms off m
ain library reading room
.
Book Storage R
oom (located off
Library)
1. Fluorescent light fixtures
L M
ounted to under-side of concrete floor joists.
2.
Bookcases (w
ood) L-M
S
even rows of these. M
any heavy things stored on top, and these are falling hazards.
3.
Bookshelves (m
etal) L
Secured to back w
all of room.
4.
Water heater
H
Sm
all electric unit situated on platform
mounted to w
all. Unit is
unrestrained and can fall off platform
.
5. M
agazine shelves L
7’ high wood bookcases secured
to wall.
C
ounseling Office
1.
Fluorescent light fixtures L
Cable-hung
2.
Bookcases (w
ood) H
Tw
o of these, both not fastened to w
all. 72” H x 36” W
x 12”D.
H/D
= 6.0
3. File cabinets
L Three 4 draw
er units that are “w
edged in” and considered low
risk.
31
ItemV
ulnerabilityC
omm
ents
C
ollege and Career C
enter
1. Fluorescent light fixtures
L C
able-hung.
2. B
ookshelves L
Several of these, varying in size,
secured to walls
3. S
torage cabinets L
Built-in units
B
asement M
echanical Room
1.
Am
erican Standard boiler
Unknow
n Large gas unit that has a rigid gas line. C
ould not see anchorage. A
nchorage must be
verified or installed.
2. M
etal shelving M
-H
Unrestrained prefab X-braced
units.
3. P
ump
L A
nchored
4. S
prinkler piping L-M
Located at bottom
of stairs, braced.
Elevator
1. E
levator U
nknown
Believed to be a hydraulic unit.
Runs betw
een library (lower
level) and second floor (upper level).
44
32
Table 2 - Nonstructural Survey R
esults for the Student C
enter (Building B
)
ItemV
ulnerabilityC
omm
ents
Cafeteria
1.
Fluorescent light fixtures M
-H
Four rows of large fixtures.
These are hung from ceiling
on metal tubes. It appears
that tubes have rigid connections at top, w
ires restrain longitudinal m
ovements but not transverse.
Very suspect.
2. V
ending machines
M
Unrestrained units 80” H
x 36” W
x 26” D and 72” H
x 36” W x
30” D. H
/D = 3.1 and 2.4
3. W
indows over exit doors
M
Window
s appear to be ordinary glass. W
ire glass used in doors.
B
alcony
1. Fluorescent lights fixtures
L-M
Three are ceiling hung with
cable, one has stems w
ith ball and socket top connections.
2.
Storage cabinet
M
Very large w
ood unit on large platform
appears unrestrained.
Kitchen A
rea
1. Fluorescent light fixtures
L C
eiling-mounted
2.
Oven
H
Tall unrestrained unit 75” H x
38” W x 33” D
with flexible gas
line.
3. O
ven/range H
U
nrestrained unit with flexible
gas line.
4. H
obart refrigerator M
U
nrestrained unit 83” H x 55”
W x 32” D
. H/D
= 2.6
5. True refrigerator
M
Unrestrained unit 83” H
x 27” W
x 29” D. H
/D = 3.1
33
ItemV
ulnerabilityC
omm
ents
B
asement
1.
Fluorescent light fixtures M
Tw
o of these, rod hung inexpensive fixtures.
2.
Water heater
H
Unrestrained electric unit.
3.
Sturtevant fan
M-H
Large fan/blow
er on angle iron fram
e that is not anchored to floor.
4.
Ducts
L-M
Difficult to assess
5.
Storage shelf
H
Unrestrained 89” H
x 106” W x
11½” D
unit against wall. H
/D
= 7.7
Storage Area (W
est End)
1. Fluorescent light fixtures
L C
eiling-mounted
2.
Northland refrigerator
L-M
Unanchored unit 72” H
x 35” W
x 27” D. H
/D = 2.7
3.
Delfield refrigerator
L-M
Three of these, all unrestrained and on rollers 80” H
x 50” W x 32”D
. H/D
=2.5
4. S
torage shelves L
Built-in units
5.
Light metal shelving
M
Unanchored
C
hair Storage Room
(West End)
1. Fluorescent light fixtures
L S
ingle large fixture supported by unistrut.
2. S
torage shelves L
Built-in units along w
alls.
Special Education Office (W
est End)
1. Fluorescent light fixtures
L C
eiling-mounted
2.
Bookshelf (R
oom 1)
H
Unrestrained unit 72” H
x 25” W
x 11” D. H
/D = 6.5
45
34
ItemV
ulnerabilityC
omm
ents
3.
File cabinets L-M
A
number of 4 draw
er files. N
ot restrained. Most have
drawer locks.
35
Table 3 - Nonstructural Survey R
esults for the A
lan Harvey Theater (B
uilding C)
ItemV
ulnerabilityC
omm
ents
Roof
1. H
VA
C unit
M
Very large m
echanical unit m
ounted on six vibration isolation devices (V
ID). E
ach VID
is secured to curb (not visible) w
ith tw
o lag screws or bolts. O
ne VID
has no bolts to connect it to curb.
2.
Gas line
H
Gas line to H
VA
C unit is rigidly
connected. Needs flexible
connection.
3. D
ucts H
A
number of large ducts on roof.
These have variety of sizes (e.g., 60x26, 56x20, 38x15 and 42x8). Individual legs supporting ducts are not fastened at all to w
ood sleepers but life safety risk is m
inor.
4. R
oof tile L
Tile on equipment screen is w
ired to nails.
5. Flood light
L Large flood light, secured to trellis.
6.
Light fixtures L
Twelve sm
all fixtures secured to trellis.
Theater
1. S
tage lights L
These seem w
ell secured to glulam
beams.
2. C
eiling lights L
Sm
all incandescent lights fastened to ceilings.
3.
Speakers (sides of stage)
L Tw
o of these, both mounted to
wall w
ill steel brackets.
46
36
ItemV
ulnerabilityC
omm
ents
4.
Speakers (over stage)
L Three of these, all restrained w
ith cables
Lobby
1. C
eiling lights L
Ceiling-m
ounted incandescent.
2. E
ntry/exits L
Overhead glass is tem
pered.
Projector Room
1. Lights
L C
eiling-mounted incandescent.
Stage
1. Lights
Unknow
n Typical stage lights m
ounted on pipes, not rated.
2. C
urtains U
nknown
Typical hanging curtains of various sizes.
M
echanical/Electrical Room
1.
Blow
er and duct L
Secured
2.
Transformer
L A
nchored
Piedmont A
dult School (Low
er Level)
1. Fluorescent light fixtures
L C
eiling-mounted.
2.
Light steel shelving L-H
Located in supply room
s. Most
of the shelves are secured to w
alls and rated (L), but shelving on east w
all is unsecured and rated (H
).
3. W
ood bookshelf H
U
nrestrained unit 84” H x 32” W
x 11” D
. H/D
=7.6
4. R
efrigerator M
U
nrestrained
37
ItemV
ulnerabilityC
omm
ents
5.
Metal storage cabinets
M
A num
ber of these. All are
unrestrained. Units are 78” H
x 36” W
x 24” D, and 72” H
x 36” W
x 18” D. H
/D=3.3 and 4.0
6.
File cabinets L-M
A
number of 4 draw
er files with
drawer locks.
47
38
7. Sum
mary and R
ecomm
endations Sum
mary
A
n AS
CE
31 Tier 2 seismic evaluation of three buildings at P
iedmont H
igh School w
as perform
ed for the Life Safety perform
ance level. The buildings are the Quad building (B
uilding A),
the Student C
enter (Building B
), and the Alan H
arvey Theater (Building C
). A nonstructural seism
ic hazard survey w
as also conducted. Results are sum
marized below
.
Quad building: The building consists of five separate structures. These are isolated from
each other by expansion joints and w
ere evaluated as individual structures. Results for each are
summ
arized below.
Original Q
uad building – This building does not meet the A
SC
E 31 life safety criteria. The roof
and attic diaphragms are greatly overstressed, and the structure m
aybe a risk to occupants in a m
ajor earthquake.
Quad building addition – The addition has construction sim
ilar to the original Quad building.
The roof and attic diaphragms are greatly overstressed, and the structure does not m
eet A
SC
E 31 life safety criteria by a significant m
argin. Occupants m
aybe at risk in a major
earthquake.
Library – The library meets the A
SC
E 31 life safety criteria.
Library Addition – The library addition does not m
eet the AS
CE
31 criteria. A few
items,
including the connections of beams and colum
ns do not fully conform to the post-
Northridge earthquake steel design standards that are included in A
SC
E 31. The risk to
occupants, however, is not believed to be great.
Library Mezzanine – The m
ezzanine meets A
SC
E 31 life safety criteria.
Student C
enter: The Student C
enter does not meet A
SC
E 31 life safety criteria. The high roof
diaphragm is m
oderately overstressed, and the walls are not adequately connected to the roof.
The building is not believed to be a collapse hazard, but it can suffer structural damage and
needs to be strengthened.
Alan H
arvey Theater : The Alan H
arvey Theater generally meets the life safety criteria of A
SC
E
31, except that some of the connections on the roof, including the connection of the roof to the
large concrete columns, are m
oderately overstressed. These should be strengthened. This building is unlikely to collapse in an earthquake.
Nonstructural S
urvey : Som
e nonstructural hazards were found. These include loose and
broken roof tile on the Quad building, unanchored gas line on the roof of the Q
uad building, unbraced sprinkler piping also in the Q
uad building, and some unrestrained gas appliances
such as ovens and ranges. It should be noted, however, that m
any nonstructural elements are
anchored. For example, the vast m
ajority of tall bookcases and storage cabinets located throughout the school are secured against overturning. There are, how
ever, a number of
building contents that are unsecured, and these can topple to the floor. The life safety risk associated w
ith most, but not all of these, is believed to be sm
all.
39
Recom
mendations
To mitigate the seism
ic deficiencies found, we recom
mend that the follow
ing be done:
(1) The original Q
uad building and its addition have very significant seismic deficiencies, and
these two structures should have a high priority for seism
ic strengthening. If the two older
wings are to rem
ain in use prior to seismic strengthening, w
e recomm
end that the heavy S
panish tile be removed and replaced w
ith a light-weight tem
porary roof mem
brane.
(2) The buildings should be strengthened to the Life S
afety performance level of FE
MA
356 “P
restandard and Com
mentary for the S
eismic R
ehabilitation of Buildings” (R
ef. 12). This is the accepted standard for the seism
ic rehabilitation of existing buildings and has been accepted by D
SA
in the past. The document represents the next step in an evaluation
and rehabilitation process that starts with an A
SC
E 31 evaluation. If A
SC
E S
tandard 41-06 (R
ef. 13) becomes finalized in tim
e for the upgrade work, this and the 2006 changes
proposed to Title 24 (effective in 2008) for seismic strengthening of existing buildings
should be used as the upgrade criteria. AS
CE
41 is an updated version of FEM
A 356.
(3) A
dditional exploration and testing of the Quad building w
ill be required for conceptual design studies. In particular, w
all reinforcement and w
all pier boundary reinforcement
needs to be established throughout. Exploration of som
e aspects the Student C
enter will
also be required. For example, the construction of the infill w
alls on the north side of the building is not show
n on the drawings and needs to be determ
ined.
(4) The nonstructural hazards identified in Tables 1 through 3 should be given a Tier 2 evaluation and/or abated, particularly those item
s designated as having a high (H)
vulnerability that can cause injury to persons in the vicinity.
Finally, it should be noted that the above recom
mendations w
ill need to be considered in light of A
DA
and fire and life safety considerations. These were not studied or considered in the
work sum
marized in this report. This evaluation is being conducted by the architect for the
project.
B
ased on structural considerations alone, we believe it is econom
ically feasible to strengthen the deficient buildings and at the sam
e time preserve their basic functional and
architectural character.
48
40
8. R
eferences
1. A
SC
E/S
EI S
tandard 31-03, “Seism
ic Evaluation of E
xisting Buildings,” S
tructural E
ngineering Institute, American S
ociety of Civil E
ngineers, 2003.
2. “P
iedmont H
igh School and H
avens Elem
entary School S
eismic E
valuations,” prepared by Janiele M
affei, Structural E
ngineer, Piedm
ont, August 1, 2004.
3. “G
uide and Checklist for N
onstructural Earthquake H
azards in California S
chool,” a P
roject of the California G
overnor’s Office of E
mergency S
ervices, Division of S
tate A
rchitect, Seismic S
afety Com
mission, and D
epartment of E
ducation, January 2003.
4. “S
eismic D
esign Param
eters,” prepared by U.S
. Geological S
urvey, Federal Em
ergency M
anagement A
gency, and Building Seism
ic Safety C
ouncil, Version 3.10, February 2001
(CD
-RO
M).
5. M
easured drawings of Q
uad building, prepared by Murakam
i/Nelson A
rchitects, O
akland, 2007.
6. “A
s-built Structural draw
ings for Original Q
uad Buildings,” prepared by R
. P. G
allagher A
ssociates, Inc., Structural E
ngineers, Oakland, M
arch 2007.
7. “M
aterial Testing, Quad B
uilding at Piedm
ont High S
chool, Magnolia A
venue, Piedm
ont, C
A,” report prepared by A
pplied Materials &
Engineering, Inc., O
akland, January 2, 2007.
8. A
rchitectural and structural drawings for Library &
Quad B
uilding prepared by Reid &
Tarics A
ssociates, Architects and E
ngineers, San Francisco, 1975, D
SA
Application N
o. 38432.
9. A
rchitectural and structural drawings for Library/E
nglish Building 30 (Library A
ddition), prepared by D
avid Wade B
yrens Architecture, O
akland, and GK
O M
essinger &
Associates S
tructural Engineers, O
akland,1995, DS
A N
o. Application 64149.
10. Architectural and structural draw
ings (A1-A
10, S1-S
4) for Library Building for P
iedmont
High S
chool (now S
tudent Center), prepared by W
m. H
. & H
arold H. W
eeks, Architects,
San Francisco, 1938, D
SA
Application N
o. 2319.
11. Architectural and structural draw
ings for the Auditorium
, prepared by Reid &
Tarics A
ssociates, Architects and E
ngineers, San Francisco, 1975, D
SA
Application N
o. 38432.
12. FEM
A 356 “P
restandard and Com
mentary for the S
eismic R
ehabilitation of Buildings,”
Federal Em
ergency Managem
ent Agency, N
ovember 2000.
13. AS
CE
/SE
I Standard 41-06, “S
eismic R
ehabilitation of Existing B
uildings”, prepublication edition, S
tructural Engineering Institute, A
merican S
ociety of Civil E
ngineers, 2006.
49
5. SO
ILS ENG
INEER
’S DESIG
N
RESPO
NSE
SPECTR
A R
EPOR
T
Mem
orandum
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'07_12941.000_Final Seismic H
azard Mem
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TO:
John Nelson
murakam
i/Nelson
DA
TE:M
ay 10, 2007
FRO
M:
John Egan PR
OJEC
T NO
.: 12941.000
CC
:PR
OJEC
T NA
ME:
Piedmont Schools
Seismic Evaluation
SUB
JECT:
Earthquake Design R
esponse Spectra and Geohazards A
ssessment
SUM
MA
RY
Earthquake ground shaking hazard at Piedmont U
nified School District (PU
SD) school sites w
as assessed for possible future earthquakes on active faults in the San Francisco B
ay region. The H
ayward fault, situated approxim
ately 1¾ to 2¾
km [1 to 1¾
miles] east-northeast of the PU
SD
school sites dominates the earthquake ground shaking hazard; at this proxim
ity to the fault, differences in the ground m
otion hazard amongst the school sites are not significant. D
esign-level response spectra w
ere developed in general accordance with the structural design criteria
being implem
ented by the PUSD
for this project. For the design basis earthquake ground shaking level (designated as B
SE-1), the response spectrum is characterized by a peak horizontal ground
acceleration (PGA
) of 0.67g. In comparison, w
e note that ground shaking recorded at the Piedm
ont Middle School during the M
W 6.9 1989 Loma Prieta earthquake w
as characterized by peak horizontal ground accelerations alm
ost an order of magnitude low
er than that of the BSE-1
level (i.e., PGA
s of 0.07g to 0.08g).
In addition to earthquake ground shaking hazard, geologic hazards involving ground failure, including the potential for surface fault rupture, soil liquefaction, and slope instability, w
ere assessed during this study for the PU
SD school sites. This assessm
ent is based on our interpretation of conditions at the school sites from
published maps and data relevant to the sites,
including information on topography, geology, seism
icity, and faults, and unpublished geotechnical investigation reports prepared by others, as w
ell as our ground reconnaissance of the sites conducted during the present study. B
ased on the available information and
observations, we are of the opinion that hazard to the PU
SD schools due to surface fault rupture,
soil liquefaction, and site instability is very low to negligible.
INT
RO
DU
CT
ION
This mem
orandum presents recom
mendations for design-level response spectra for utilization in
seismic safety and retrofit evaluations of Piedm
ont Unified School D
istrict (PUSD
) school buildings being conducted by the m
urakami/N
elson team for future earthquakes in the
John Nelson
murakam
i/Nelson
May10, 2007
Page 2
San Francisco Bay region. W
e also have assessed the potential for experiencing effects at the school sites associated w
ere interpreted based on available geologic and geotechnical inform
ation for the sites and vicinity, as well as ground reconnaissance of the sites conducted
during our study. We review
ed published maps and data relevant to the sites, including
information on topography, geology, seism
icity, and faults, and unpublished geotechnical investigation reports by others provided by PU
SD through m
urakami/N
elson; these latter reports included logs of exploratory borings drilled at som
e of the sites. Reports of ground shaking
effects in the Piedmont vicinity from
historical earthquakes in the region were also review
ed.
GE
NE
RA
L A
PPRO
AC
H
We have developed design-level response spectra, designated as B
SE-2 and BSE-1, to be in
general accordance with the structural design criteria being im
plemented by the School D
istrict for this project; those criteria w
ere provided to us by fax on January 18, 2007. In developing these spectra, w
e have considered results from both probabilistic ground m
otion analysis (com
monly referred to as a probabilistic seism
ic hazard assessment or PSH
A) and determ
inistic ground m
otion analysis. These analyses analytically combine inform
ation on the locations and geom
etries of the school sites relative to potential seismic sources (i.e., faults) in the
San Francisco Bay region, the m
aximum
earthquake magnitude capabilities interpreted for those
seismic sources, spatial and tem
poral characteristics of earthquake occurrence on the sources, and source-to-site ground m
otion attenuation (based on published empirical relationships)
appropriate to the tectonic environment and interpreted subsurface conditions at the sites, as w
ell as uncertainties associated w
ith each of these components.
RE
GIO
NA
L FA
UL
TS
The San Francisco Bay region is considered one of the m
ore seismically active regions of the
world, based on its record of historical earthquakes and its position astride the N
orth A
merican-Pacific plate boundary (i.e., the San A
ndreas fault zone and other active faults). The m
ajor faults that comprise the 80-km
[50-mile] -w
ide plate boundary include, from w
est to east, the Seal C
ove-San Gregorio, San A
ndreas, Hayw
ard-Rodgers C
reek, and Calaveras faults
(see Figure 1). Each of these faults is a potential source of earthquakes that could produce significant ground shaking at the PU
SD school sites. O
ther Holocene faults that m
ay be sources for earthquakes capable of producing ground shaking at the sites include the C
oncord-Green
Valley, C
layton-Marsh C
reek-Greenville, and W
est Napa faults, as w
ell as the Mount D
iablo Thrust.
The Hayw
ard fault, situated approximately 1¾
to 2¾ km
[1 to 1¾ m
iles] to the east-northeast (see Figure 2), dom
inates earthquake ground motion hazard for the PU
SD school sites. The
San Andreas fault, situated approxim
ately 27 km [17 m
iles] to the west-southw
est of the site, also contributes significantly to seism
ic hazard at the sites because of its larger earthquake
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magnitude capability and longer duration ground shaking associated w
ith those larger magnitude
events.
HIST
OR
ICA
L SE
ISMIC
ITY
During the past 200 years, num
erous small-m
agnitude and at least fifteen moderate- to large-
magnitude (i.e., M
6+) earthquakes have occurred in the San Francisco Bay region
(Toppozada and Parke, 1982a, 1982b; Ellsworth, 1990; W
orking Group on N
orthern California
Earthquake Potential [WG
NC
EP], 1996; Working G
roup on California Earthquake Probabilities
[WG
CEP], 1999, 2003). G
round shaking experienced in Piedmont from
most of the historic
earthquakes in the region has been of generally imperceptible or quite sm
all amplitude and
produced effects observed in the Piedmont vicinity that m
ay be categorized as I through V on the
Modified M
ercalli Intensity (MM
I) scale. There have been, however, m
ore than a dozen events in the region that have produced ground shaking strong enough in Piedm
ont to produce MM
I effects greater than V
(MM
I VI corresponds to the low
est intensity level with w
hich some
damage (slight) is associated, although fragile contents m
ay be broken at MM
I V).
The first significant earthquake reported to have affected the region had a magnitude of
approximately 7.5 (estim
ated from felt intensities), occurring on the Peninsula segm
ent of the San A
ndreas fault in 1838 (Toppozada and Borchardt, 1998). A
series of smaller earthquakes
between 1850 and 1865 dam
aged various sections of the Bay A
rea, with the 1865 shock centered
near the Santa Cruz M
ountains being the most dam
aging (Townley and A
llen, 1939).
In 1868, the Hayw
ard fault produced an earthquake having an estimated m
agnitude of 6.9. A
lthough the effects of this earthquake were poorly docum
ented, surface rupture apparently extended from
near Montclair (W
GC
EP, 2003) southward to the W
arm Springs area of Frem
ont. Significant dam
age, including liquefaction and settlement in low
-lying areas, apparently occurred along the surface rupture betw
een Oakland and Frem
ont (Lawson, 1908).
During the M
W 7.91 1906 San Francisco earthquake, the San A
ndreas fault ruptured from
Shelter Cove near C
ape Mendocino southw
ard to near San Juan Bautista. M
aximum
lateral displacem
ents of 15 to 20 feet [4.6 to 6.1 m] occurred north of the G
olden Gate at O
lema in
Marin C
ounty (Lawson, 1908). Landslides, liquefaction, and ground settlem
ent occurred throughout the B
ay Area and in the vicinity of the surface rupture as result of this earthquake.
Earthquakes in the region during the past 50 years include the 1957 Daly C
ity earthquake on the San A
ndreas fault (ML 5.3); the tw
o Santa Rosa earthquakes of 1969 on the H
ealdsburg-Rodgers
Creek fault (M
L 5.6 and 5.7); the Coyote Lake and M
organ Hill earthquakes of 1979 and 1984 on
the Calaveras fault (M
L 5.9 and 6.1, respectively); the 1980 Livermore earthquake on the
Greenville fault (M
L 5.8); the 1989 MW 6.9 Lom
a Prieta earthquake in the southern Santa Cruz
Mountains; the 1999 M
L 5.0 earthquake near Bolinas; and the 2000 M
L 5.2 Yountville
earthquake.
1 MW – M
oment m
agnitude; ML – Local or R
ichter magnitude.
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The October 1989 Lom
a Prieta earthquake, that ruptured on or near the San Andreas fault zone
approximately 75 km
[47 mi] south of Piedm
ont, caused significant damage in areas of fill and
soft soils, such as in the Marina D
istrict of San Francisco and at the Port of Oakland; little
damage occurred to structures founded on rock or stiff alluvium
in Oakland or San Francisco.
We note that ground shaking w
as recorded at the Piedmont M
iddle School during the earthquake. That recorded ground shaking w
as characterized by peak horizontal ground accelerations (PG
A) of 0.07g to 0.08g (Shakal and others, 1989). M
odified Mercalli Intensity
(MM
I) effects of VII w
ere reported for Piedmont for this event.
Based on the estim
ates of MM
I reported for the Piedmont vicinity, significantly stronger ground
shaking than was experienced in 1989 w
as quite likely experienced by the school sites during at least the tw
o historic Bay region events m
entioned above. The MW
6.9 Hayw
ard earthquake in O
ctober 1868 produced MM
I VIII effects in the Piedm
ont area; to the south, MM
I IX+ effects
were experienced in near-fault areas of San Leandro (Toppozada and others, 1981; 1982a). The
great MW
7.9 San Francisco earthquake in April 1906 also produced M
MI V
III effects in the Piedm
ont area (Toppozada and Parke, 1982b). Both of these events likely also produced
substantially longer ground shaking durations than was experienced during the Lom
a Prieta earthquake.
The Working G
roup on California Earthquake Probabilities (W
GC
EP, 2003) concluded that there is a 62 percent probability that a m
ajor (MW 6.7 or larger) earthquake w
ill occur in the greater B
ay region during the 30-year time period betw
een 2003 and 2032. The report also concludes that there is an 80 percent probability that a large (M
W 6.0 to 6.7) earthquake will
occur during the same period. The im
plications of this study are that there is a high likelihood that ground m
otions stronger than those recorded during the 1989 Loma Prieta earthquake w
ill occur at the PU
SD school sites during the next 25 to 30 years.
SITE
CO
ND
ITIO
NS
Geologic m
aps (i.e., Radbruch, 1969; D
ibblee, 2005), our site reconnaissance, and available logs of borings drilled by others at the school sites (H
arza, 1994; 1995a,b,c,d; 1997a,b) indicate that subsurface conditions at the school sites typically consist of a thin veneer of fill or Pleistocene-age soil deposits overlying Franciscan form
ation sandstone and/or shale rock at relatively shallow
depths (see Figure 2). Given these conditions, it is our opinion that ground m
otion attenuation relationships developed for rock site conditions are appropriate to characterize the potential ground shaking at the school sites. For this study, w
e have utilized the published em
pirical attenuation relationships developed by Abraham
son and Silva (1997), Boore and
others (1997), Cam
pbell (1997), Sadigh and others (1997), and Idriss (1995). These attenuation relationships describe the variation of peak ground acceleration and response spectral accelerations at specific structural periods of vibration and dam
ping ratios with earthquake
magnitude and distance and w
ere developed on the basis of statistical analyses of ground m
otions recorded during earthquakes at many locations in C
alifornia, as well as in other parts of
the western U
nited States and foreign countries having similar tectonic environm
ents.
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EA
RT
HQ
UA
KE
GR
OU
ND
SHA
KIN
G
As m
entioned previously, we have considered results from
both probabilistic ground motion
analyses (PSHA
) and deterministic ground m
otion analyses (DSH
A) in developing design-level
response spectra for this project.
School Sites’ Hazard C
omparisons. B
ased on our evaluations and experience with other sites
near the Hayw
ard fault and in the general vicinity, as well as elsew
here in the Bay region, w
e expect that differences in the ground m
otion hazard amongst the school sites are not significant.
We therefore are of the opinion that a single, com
mon set of design-level response spectra
(BSE-2 and B
SE-1) is appropriate to all of the sites for conducting seismic safety and retrofit
evaluations of the school buildings.
PSHA
results presented by the California G
eological Survey (CG
S) (Cao and others, 2003) for
each of the schools’ site coordinates, corresponding to a 10% probability of exceedance in
50 years (475-year return period) and firm rock site conditions, are sum
marized in Table 1.
TA
BL
E 1
SUM
MA
RY
OF C
GS H
AZA
RD
RE
SUL
TS FO
R T
HE
PUSD
SCH
OO
L SIT
ES
School
Closest D
istance to H
ayward
Fault (km)
Ground M
otion Hazard for P
E =10% in 50 Y
ears and Firm
Rock Site C
onditions (5%
-damped)
PGA
(g)S
a (g) @ T
=0.2s S
a (g) @ T=1s
Havens
1.7 0.779
1.811 0.686
High School
1.8 0.779
1.809 0.685
Middle School
1.9 0.777
1.807 0.684
Wildw
ood 2.2
0.774 1.800
0.681 B
each2.7
0.7721.794
0.679
We note that these results dem
onstrate the very small difference in estim
ated ground shaking hazard (less than 1%
) amongst the sites.
Determ
inistic estimates of possible horizontal peak ground accelerations and response spectral
accelerations at the PUSD
school sites were developed assum
ing the occurrence of possible m
aximum
magnitude earthquakes rupturing through the closest point on the H
ayward fault zone
from the sites. The W
GC
EP (2003) defines three segments for the H
ayward-R
odgers Creek fault
zone: the south Hayw
ard, north Hayw
ard, and Rodgers C
reek. The boundary between the south
and north Hayw
ard segments has been taken by the W
GC
EP (2003) to lie at Montclair, or
approximately the closest point on the H
ayward fault from
the PUSD
school sites; the Rodgers
Creek fault segm
ent lies north of San Pablo Bay. The W
GC
EP (2003) has characterized five possible rupture scenarios ruptures involving either the south H
ayward or north H
ayward
segments, individually or in com
bination, each associated with a likelihood of that rupture
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scenario occurring and probabilistic distributions for characteristic maxim
um earthquake
magnitudes for that scenario. These scenario likelihoods and m
agnitude distributions were
incorporated in conducting the deterministic ground m
otion analyses to estimate the ground
shaking characteristics representative of the possible range of maxim
um earthquake capability of
the Hayw
ard fault near Piedmont; this possible range of m
aximum
earthquake capability is illustrated on Figure 3.
FIGU
RE
3
Hayward Fault M
aximum
Earthquake
0
0.1
0.2
0.3
0.4
0.5
6.66.7
6.86.9
7.07.1
7.27.3
7.4
Magnitude, M
w
Probability
Discrete
The ground motion attenuation relationships m
entioned previously were used in these
deterministic analyses. The results of determ
inistic analyses indicate a median response spectrum
characterized by m
edian peak horizontal ground accelerations of 0.67g; this ground motion level
corresponds to the BSE-1 design-level in the structural design criteria being im
plemented by the
PUSD
for this project. To obtain the MC
E or BSE-2 design-level ground shaking response
spectrum in accordance w
ith these structural design criteria, the median determ
inistic response spectrum
was m
ultiplied by a factor 1.5.
RE
CO
MM
EN
DE
D D
ESIG
N-L
EV
EL
RE
SPON
SE SPE
CT
RA
B
ased on the considerations mentioned previously and results from
probabilistic and determ
inistic ground motion analyses for the sites, w
e recomm
end the response spectra presented in Table 2 and Figure 4 below
to represent the design levels BSE-2 and B
SE-1 for use in seismic
safety and retrofit evaluations being conducted for the PUSD
schools.
Near-Field E
ffects Considerations. A
lthough the sites are situated in relatively-close proximity
to the Hayw
ard fault zone, we understand, based on discussions w
ith the design/evaluation team,
that the school buildings are relative short-period structures (i.e., T 1 sec.); so, w
e anticipate that potential near-field rupture directivity and fault norm
al/parallel effects that can be significant to longer period horizontal-com
ponent ground motions w
ill be small or insignificant at the
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periods of the buildings. We have not, therefore, included explicit evaluation of these effects in
our analyses.
Vertical R
esponse Spectra Considerations.
As m
entioned previously, the Piedmont school
sites are is situated in close proximity to the H
ayward fault, w
hich dominates ground m
otion hazard at the sites. N
ear-field strong motion recordings obtained from
earthquakes that have occurred over the past three decades have exhibited vertical m
otions equal to or exceeding the horizontal m
otions (e.g., Egan and others, 1994; Abraham
son and Silva, 1997; Cam
pbell and B
ozorgnia, 2003). Of relevance to the Piedm
ont school sites, examination by these and other
authors of available ground motion data from
moderate to large (M
W 6.5) C
alifornia earthquakes indicates: (1) w
ithin about 15 km of fault ruptures, peak ground accelerations and
higher frequency (T < 0.2 sec) response spectral ordinates for the vertical component
approximately equal or exceed those of the horizontal com
ponents; and (2) there appears to be little distance dependence for longer period m
otions (T > 0.3 sec), with average vertical to
horizontal ratios for spectral ordinates of about one-half or less for all distance ranges examined.
TA
BL
E 2
RE
CO
MM
EN
DE
D D
ESIG
N-L
EV
EL
BSE
-2 AN
D B
SE-1 H
OR
IZON
TA
L-C
OM
PON
EN
T
RE
SPON
SE SPE
CT
RA
FOR
TH
E PU
SD SC
HO
OL
SITE
S.
Period, T
(sec)
Response Spectral
Acceleration, S
a (g) 5%
-damped
Response Spectral
Acceleration, S
a (g) 10%
-damped
BSE
-2 B
SE-1
BSE
-2 B
SE-1
PGA
1.005
0.670 1.005
0.670 0.03
1.005 0.670
1.005 0.670
0.1 2.071
1.381 1.657
1.105 0.2
2.404 1.603
1.803 1.202
0.3 2.281
1.521 1.711
1.141 0.4
2.035 1.357
1.526 1.017
0.5 1.747
1.165 1.310
0.873 0.75
1.192 0.794
0.905 0.603
10.913
0.609 0.699
0.466 1.5
0.565 0.376
0.443 0.296
20.390
0.260 0.312
0.208 3
0.218 0.145
0.181 0.121
40.139
0.093 0.120
0.080
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FIGU
RE
4
Piedmont Schools - R
ecomm
ended Design
Spectra (5%-dam
ped)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
01
23
4
Period, T (sec)
Response Spectral Acceleration, Sa (g)
BS
E-2
BS
E-1
Piedmont Schools - R
ecomm
ended Design
Spectra (10%-dam
ped)
0.0
0.5
1.0
1.5
2.0
2.5
3.0
01
23
4
Period, T (sec)
Response Spectral Acceleration, Sa (g)
BS
E-2
BS
E-1
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OT
HE
R C
OM
PAR
AT
IVE
RE
SPON
SE SPE
CT
RA
For com
parison purposes, we have also evaluated response spectral ordinates associated w
ith a num
ber of probabilistic hazard levels and several deterministic events of significance to ground
shaking at the sites. These include:
Probabilistic hazard levels of 2%, 10%
, and 20% in 50 years.
Characteristic m
aximum
magnitude earthquakes assigned to the H
ayward fault. The
2002 Working G
roup on California Earthquake Probabilities (U
nited States Geological
Survey [USG
S], 2003) selected Montclair as the segm
entation point between the northern
and southern segments of the H
ayward fault; M
ontclair lies essentially at the closest location of the fault to the school sites. Therefore, characteristic m
aximum
magnitude
earthquakes assigned by the CG
S/USG
S to the northern Hayw
ard fault segment (M
W6.5), to the southern H
ayward fault segm
ent (MW 6.7), and to the H
ayward fault as a
whole (M
W 6.9) may be considered as rupturing the fault at the closest distance of the
fault to the school sites. We note that the O
ctober 21, 1868, earthquake that ruptured the southern portions of the H
ayward fault is interpreted to have been a M
W 6.9 event; there is som
e uncertainty as to extent of surface rupture for this event, but trenching evidence suggests it extended at least as far north as M
ontclair.
Characteristic m
aximum
magnitude earthquake assigned to the San A
ndreas fault based on the fault rupture that occurred in 1906 (M
W 7.9).
Response spectral ordinates for these various hazard levels and characteristic and/or historic
events are summ
arized in Table 3 and Figure 5 below.
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TA
BL
E 3
CO
MPA
RA
TIV
E H
OR
IZON
TA
L-C
OM
PON
EN
T R
ESPO
NSE
SPEC
TR
A E
STIM
AT
ED
FO
R SE
LE
CT
ED
HA
ZA
RD
LE
VE
LS A
ND
CH
AR
AC
TE
RIST
IC A
ND
/OR
HIST
OR
IC
EA
RT
HQ
UA
KE
S AFFE
CT
ING
TH
E PIE
DM
ON
T SC
HO
OL
SITE
S.
Period, T
(sec)R
esponse Spectral Acceleration, S
a (g) 5%
-damped
Probability of Exceedance (P
E )in 50 years
Hayw
ard Fault
San A
ndreas Fault
2%
10%
20%
Northern
MW 6.5
Southern M
W 6.7
Historic
(1868) MW
6.9
Historic
(1906) MW
7.9 PG
A
1.34 0.84
0.61 0.58
0.61 0.63
0.25 0.03
1.34 0.84
0.61 0.58
0.61 0.63
0.25 0.1
2.73 1.65
1.15 1.08
1.14 1.17
0.42 0.2
3.36 1.96
1.37 1.27
1.37 1.43
0.58 0.3
2.99 1.76
1.24 1.11
1.23 1.31
0.57 0.5
2.26 1.31
0.93 0.78
0.90 0.98
0.46 1
1.29 0.74
0.52 0.38
0.46 0.51
0.27 1.5
--
-0.22
0.28 0.32
0.18 2
0.58 0.34
0.24 0.15
0.19 0.21
0.13 3
0.33 0.19
0.14 0.08
0.10 0.12
0.08 4
0.21 0.12
0.09 0.05
0.07 0.08
0.05
FIGU
RE
5
Piedmont Schools - O
ther Spectra (5%-dam
ped)
0.00.51.01.52.02.53.03.5
01
23
4
Period, T (sec)
Response Spectral Acceleration, Sa (g)
2%/50yr
10%/50yr
20%/50yr
N. Hayward M
6.5
S. Hayward M
6.7
Hayward (1868) M
6.9
San Andreas (1906) M
7.9
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GE
OL
OG
IC H
AZA
RD
S G
eologic hazards considered during this study for the PUSD
school sites include the potential for surface fault rupture, soil liquefaction, and slope instability.
Surface Fault Rupture. There have been no active or potentially active faults identified in the
imm
ediate vicinity of the PUSD
school sites according to the California G
eological Survey and the site is not located w
ithin a State of California Special Fault Studies Zone. The nearest active
fault is the Hayw
ard fault, situated no closer than approximately 1¾
km [1 m
ile] to any of the school sites (see Figure 2). A
dditionally, reconnaissance observations of the sites and surrounding areas do not indicate the presence of geologic conditions, geom
orphic features or lineam
ents suggestive of active or inactive faulting crossing the sites. Based on this inform
ation, w
e are of the opinion that surface fault rupture hazard to the PUSD
school sites is negligible.
Liquefaction. Liquefaction is a soil behavior phenom
enon in which a soil loses a substantial
amount of strength due to high excess pore-w
ater pressure generated by strong earthquake ground shaking. R
ecently deposited (geologically) and relatively unconsolidated soils and artificial fills located below
the ground water surface are considered susceptible to liquefaction
(Youd and Perkins, 1978). Typically, susceptible soils include relatively clean, loose, uniform
ly graded silt and sand deposits (N
ational Research C
ouncil, 1985).
As discussed previously in this report, the geologic and geotechnical data gathered during this
study indicate that the surficial soils, if present, are Pleistocene-age deposits. These soils are considered to have very low
susceptibility to earthquake-induced liquefaction. We note that no
evidence of liquefaction and/or related effects was reported for the PU
SD school sites or vicinity
for the 1868 Hayw
ard earthquake or the great 1906 San Francisco earthquake (Lawson, 1908;
Youd and H
oose, 1978), nor for the 1989 Loma Prieta earthquake (Tinsley and others, 1998).
We are of the opinion, therefore, that the hazard due to potential soil liquefaction to the PU
SD
school sites is negligible.
Site Stability. Lateral spreading, which is the lateral displacem
ent of surficial soils, is usually associated w
ith the liquefaction of underlying soils. With the potential liquefaction hazard at the
site judged to be negligible, we expect that the potential for lateral spreading to occur and affect
the school buildings to be of similar hazard level. The soil deposits and rock m
aterials underlying the school sites are considered to be quite com
petent and not susceptible to significant strength changes that w
ould affect site stability. No ground cracking, hum
mocky topography, displaced
flatwork, slope creep affecting tree grow
th, or other significant evidence of ground deformation
or site instability was observed at the school sites or in slopes adjacent to the school sites during
our ground reconnaissance. We do note that at B
each Elementary School, the retaining w
all along the Linda A
venue (west) side of the playground and the retaining w
all along How
ard A
venue at the top of the slope on the west side of the school are cracked and som
e portions of the w
alls have rotated outward about the base of the w
all. It is our opinion that this localized wall
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distress represent long-term w
all maintenance and repair/replacem
ent issues, rather than being indicative of global site instability. In addition, there are no m
apped landslides (Nilsen, 1975)
nor reports of ground failure at the sites or in their imm
ediate vicinities during historical earthquakes (Y
oud and Hoose, 1978), and M
iles and Keefer (2001) m
ap the relative seismic
landslide hazard for the Havens, W
ildwood, M
iddle School, and High School sites as negligible
to low, w
ith the Beach site as m
oderate. We are of the opinion that hazard to the PU
SD schools
due to site instability is very low.
RE
FER
EN
CE
S
Abraham
son, N.A
., and Silva, W.J., 1997, Em
pirical response spectral attenuation relations for shallow
crustal earthquakes: Seismological R
esearch Letters, v.68, no.1, pp.94-127.
Boore, D
.M., Joyner, W
.B., and Fum
al, T.E., 1997, Equations for estimating horizontal response
spectra and peak acceleration from w
estern North A
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California D
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Cam
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vertical components of peak ground acceleration, peak ground velocity, and pseudo-absolute
acceleration response spectra: Seismological R
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Cam
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., and Bozorgnia, 2003, U
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Cao, T., B
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Job No.: 0629 - P
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D S
eismic
School / Site
AbbreviationBuilding Designation
Building Name
Seismic Tier 1Revised Seismic Tier 1
Letter From Forell & Elsesser on Seismic Performance*
