HomeMy WebLinkAbout01/21/1992, 1 - ADOPTION OF SEISMIC STRENGTHENING STANDARDS FOR UNREINFORCED MASONRY BUILDINGS BY CREATING A NEW APPENDIX CHAPTER IN THE BUILDING CODE.Original agenda report from meeting of 1/7/92 - EXCEPT - Pages 4,
6 and 30. MEETING OA
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ON COUNCIL AGENDA REPORT ITEM NUMBER:
FROM: Arnold Jonas, Community Development Director0
PREPARED BY: Tom Baasch, Chief Building Official
SUBJECT: Adoption of seismic strengthening standards for
unreinforced masonry buildings by creating a new
appendix chapter in the Building Code.
CAO RECOMMENDATION:
Introduce ordinance to print establishing (1) seismic
strengthening standards for buildings of unreinforced masonry
(URM) construction, and (2) administrative regulations requiring
that all URM buildings be structurally analyzed within 18 months
following January 1, 1993 and that any URM building subject to
major remodel or occupancy change be strengthened to the
established standards.
DISCUSSION:
During the Council meeting of December 3, 1991, the City Council
reviewed the staff report and proposed strengthening ordinance
for unreinforced masonry buildings. After considerable
discussion, City Council directed staff to submit a revised
ordinance and related information at the first meeting in
January. Direction included the following:
■ Refine language in the ordinance concerning the beginning
date for the 18 -month period during which each owner of a
URM building shall have the building structurally
analyzed.
■ Outline a plan to gain State recognition of the use of
Seismic zone 3 criteria in the City's strengthening
standards.
• Provide a list of the URM buildings owned by tax exempt
entities.
• Evaluate the correlation between the compliance deadline
in existing fire sprinkler retrofit requirements and the
proposed seismic strengthening ordinance.
Modifications to Proposed Ordinance
Changes to Section A2311(c) of the proposed ordinance (pages 21
and 22) clarify the deadline for completion of the structural
analysis required of each URM building owner. The language
establishes two documents that are to be issued by the Building
Official:
1. A Notice will be sent within 30 days of ordinance
adoption reminding the property owner that a "potentially
hazardous" building exists on said property. A copy of, V,.
city of San l,_,s o81Spo
COUNCIL AGENDA REPORT
Section 2311(b), which lists the owner's compliance
requirements, is to be included with the notice.
Reference to the notice in Section 2311(c)4 insures that
recordation with the County Recorder will occur soon
after passage.
2. An Order directing the owner to obtain and submit to the
City the required structural analysis is to be served no
earlier than the 30 -day period beginning January 1, 1993.
Adequate language has been added to allow the Building
Official to defer this action if proposed changes to
State codes remain unresolved or conflict with the
provisions of the City's strengthening program.
The exception to change of occupancy requirements for multi -use
buildings (page 21) has also been refined to address a conflict
with Section 502 of the Building Code. The language now
precludes the application of Section 502 in the case of URM
buildings and preserves the less restrictive approach agreed to
for multi -use buildings. Wording has also been added to quantify
the occupancy change by referencing floor area involved.
Seismic Zone 3 Criteria -
Staff continues to feel that the use of Zone 3 criteria in the
proposed strengthening ordinance is supported by the seismicity
study, recent maps published through the National Earthquake
Hazard Reduction Program, and by a growing trend among design
engineers to rely on a site specific seismic hazard analysis. At
the present time, there are no rules or regulations issued by the
State which would preclude the use of Zone 3 criteria in the
City's technical standards for URM strengthening. As a
modification to the Building Code, Zone 3 factors are supported
by adequate findings.
The concern about future State rulings on this matter remains;
future decisions may affect future strengthening projects.
However, staff feels that it is premature to achieve resolution
at this time and proposes the following action plan:
1. Forward the City's strengthening ordinance to the Seismic
Safety Commission after adoption and await their
comments.
2. Continue to monitor efforts by the State Building
Standards Commission to adopt strengthening standards
mandated by AB204.
3. If neither concurrence or resistance to the City's
ordinance is received from the State or if conflict
between City and State regulations is not obvious, staff
will request a written response from the appropriate
State agency regarding the legality of the City's
modifications to the California Building Code. �,�
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Gia; COUNCIL AGENDA REPORT
4. If determined to be prudent after conclusion of items 1-
3, encourage the support of Senator Maddy and
Assemblywoman Seastrand towards State acceptance of the
City's efforts in utilizing area specific seismic force
determination for strengthening criteria.
Information suggests that clear indications from item 2 of the
plan will not be available for at least 6 months into 1992.
Staff will persist in efforts to clarify the issue and inform the
Council accordingly.
Tax Exempt Properties
Staff reviewed data available and determined that there are 15
buildings in the unreinforced masonry building inventory that are
owned by tax - exempt entities. The list (attached) consists only
of 5 buildings owned by churches and 10 that are government
owned.
Fire Sprinkler Retrofit Program
As summarized in the previous staff report to the City Council,
the proposed strengthening ordinance is an interim measure that
may ultimately be only a small part of the City's URM mitigation
program. Adoption of State regulations pursuant to AB204 and
analysis of data collected at the conclusion of the structural
analysis period may dictate significant changes to the proposed
ordinance. There is the possibility that State regulations will
mandate a compliance deadline for URM strengthening that will be
consistent with the year 2000 deadline in the fire sprinkler
retrofit ordinance.
It is important to note that there are 200 buildings located in
the downtown fire sprinkler zone that will require fire sprinkler
retrofit. Of these, less than 45 percent are URM buildings that
would require strengthening. The Fire Chief recommends that
pending resolution of the URM strengthening deadline not impede
progress in installing fire sprinkler systems in non -URM downtown
buildings.
Staff recommends that no action concerning the fire sprinkler
retrofit deadline be taken at this time and that the action plan
on•this issue be as follows:
1. Monitor efforts by the Building Standards Commission to
satisfy AB204 during 1992 and report back to the Council
as soon clear direction is established.
2. If deadlines for the unreinforced masonry strengthening
program remain unclear at the end of 1992, postpone
further action on the fire sprinkler retrofit deadline
until conclusion of the structural analysis period
(approximately July, 1994).
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i COUNCIL AGENDA REPORT
3. During the periods outlined in items 1 and 2, existing
Building and Fire Code requirements for fire sprinkler
systems will parallel the proposed strengthening
ordinance due to similar language regarding occupancy
change and remodeling in excess of 50 percent of
replacement cost.
CONCURRENCES:
The proposed ordinance is supported by the Chamber of Commerce,
and the San Luis Obispo Property Owner's Association if the cost
of the structural analysis required by the ordinance is
considered as a credit towards future City permits to construct
strengthening improvements. The position of the BIA was not
known prior to the printing of this report; a statement regarding
their concurrence will be issued under separate cover. The Fire
Chief concurs with the recommendation concerning the fire
sprinkler retrofit deadline.
FISCAL IMPACT:
There are no immediate fiscal impacts for the City. Notice and
Order procedures and the processing of building permits for
strengthening projects can be accomplished by existing staff.
Staff will work with the Seismic Task Force in the coming months
to outline a program offering a credit towards City permits for
seismic strengthening based on the cost of the initial structural
analysis; a recommendation will be submitted to the Council far
in advance of the mandatory structural analysis period.
SUMMARY:
The staff recommended strengthening ordinance as modified by City
Council direction represents the conclusion of a process that
will establish "state of the art" technical standards for
designing structural improvements to unreinforced masonry
buildings to achieve the most cost effective reduction in
potential seismic hazard, and creates a basic element of a
mandatory program to reduce URM hazards. The primary purpose of
the ordinance is to improve life safety; the minimum
strengthening methodology will limit damage to a URM building and
adjacent buildings, but may not prevent irreparable damage.
However, the proposed ordinance is reasonable compromise at this
time that will begin to provide a safer environment for occupants
of a URM building and pedestrians passing by.
Because the proposed ordinance does not insure a significant
reduction in the URM earthquake hazard, it must be considered an
interim measure leading to in a more comprehensive mitigation
program satisfying the State mandate.
ATTACHMENTS: 1. Legislative Draft
2. Proposed Ordinance 3. List of Tax Exempt Buildings
January 10, 1992
LEGISLATIVE DRAFT
Revisions to Proposed Unreinforced Masonry Building
Strengthening Ordinance Following City Council Meeting of 12 -3 -91
ORDINANCE NO.
(1992 SERIES)
Administrative Provisions
Section A2311. (a) Definitions. For the purposes of this
Chapter, the applicable definitions in the Building Code shall
apply.
(b) Compliance Requirements.
1. The owner of each building within the scope of this
Chapter shall, upon service of an order, cause a.structural
analysis to be made of the building by an engineer or
architect licensed by the state to practice as such. Said
analysis shall include the preparation of a report detailing
the investigation, evaluation, test data, conclusions, and
recommendations to establish compliance with this Chapter.
If the building does not comply with seismic standards
established in this Chapter, the report shall specify the
work and cost necessary to structurally alter the building
to conform to such standards. The Building Official shall
establish a basic outline for the format of the report.
2. The owner of a building within the scope of this
Chapter shall comply with the requirements set forth above
by submitting the analysis report to the Building Official
for review and acceptance within 18 months of the service of
an order.
3. The owner of a building within the scope of this
Chapter shall structurally alter the building to conform to
the seismic standards of this Chapter or cause the building
tq be demolished when either of the following occurs:
A. The value of additions, alterations, and /or
repairs, cumulative from the effective date of this
Chapter, exceeds 50 percent of the replacement value of
the building established by the Building Official per
Section 304(b) of the Uniform Administrative Code.
B. The use of the building changes to a different
division of the same group of occupancy or to a
different occupancy group.
(d)
EXCEPTION:
containing more than one occupancy classification
need not comply with this Chapter if
m< €a changes in use, cumulative from the
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effective date of this Chapter, de d not exceed
50 percent of the floor area of the building.
4. This Chapter does not require alteration of existing
electrical, plumbing, mechanical, or fire safety systems.
Administration.
2. order eententso
be in
I. order 8ervies. The Building 9ffieial shall,
within
30 days of the effective- mate —of this ehapter, , I..
. :fin
eefaalleed assessment /
2. order eententso
be in
The —erde= steal
shall be served either al l
registered mail upen the-ewner as shown
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by .mot t'ie
en the last
and
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speeify that the building has been determined
by the
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Beilding a € €ielal to to within the seepe —e
and, there ere,— s ,J r ed to —meet the minimum -- --
standa2ds e€ t is chapter. The ardor shall -peel -fy the
tang _las i fiea s -_ of the building l di ng an shall
l }a.
3. Appeal. The owner of the building may appeal the
Building Official's initial determination that the building
is within the scope of this Chapter to the Board of Appeals
established by Section 204 of the Uniform Administrative
Code. Such appeal shall be filed with the Board within 60
days from the service date of the order described in Section
A2311(c)2. Appeals or requests for modifications from any
other determinations, orders or actions by the Building
Official pursuant to the Chapter shall be made in accordance
with the procedures established in Sections 107, 108 and 204
of the Uniform Administrative Code. Any appeal shall be
decided by the Board no later than 90 days after filing and
the grounds thereof shall be stated clearly and concisely.
4. Recordation. At the time that the Building Official
serves the aforementioned ender oiw , the Building
Official shall also file and record with the office of the
county recorder a certificate stating that the subject
building.is within the scope of this Chapter and is a
potentially earthquake hazardous building. The certificate
shall also state that the owner thereof has been
ordered to structurally analyze the building to determine
compliance with this Chapter.
If the building is either demolished, found not to be within
the scope of this Chapter, or is structurally capable of
resisting minimum seismic forces required by this Chapter as
a result of structural alterations or an analysis, the
Building Official shall file and record with the office of
the county recorder a form terminating the status of the
subject building as being classified within the scope of
/ -7
this Chapter.
5. Enforcement. If the owner in charge or control of the
subject building fails to comply with any order issued by
the Building Official pursuant to this Chapter within the
time limit set forth in Section A2311(b), the Building
Official shall verify that the record owner of this building
has been properly served. If the order has been served on
the record owner, then the Building Official shall order
that the entire building be vacated and that the building
remain vacated until such order has been complied with. If
compliance with such order has not been accomplished within
90 days after the date the building has been ordered vacated
or such additional time as may have been granted by the
Board of Appeals, the Building Official may order its
demolition in accordance with the provisions of section 203
of the Uniform Administrative Code.
6. Annual Report. During January of each year, the
Building Official shall submit a report to the City Council
outlining the progress to date concerning reduction of the
hazards presented by the unreinforced masonry building
inventory for the City. The report shall include:
A. The number of unreinforced masonry buildings
strengthened, demolished, or otherwise eliminated from
the inventory;
B. The number of unreinforced masonry buildings
remaining on the inventory, including the status of
orders issued pursuant to this Chapter that are not
resolved.
1 ' 40
ORDINANCE NO. (1992 Series)
AN ORDINANCE OF THE CITY OF SAN LUIS OBISPO AMENDING
TITLE 15, CHAPTER 15.04 OF THE MUNICIPAL CODE TO
ADD DIVISION III OF APPENDIX CHAPTER 23 TO THE
UNIFORM BUILDING CODE AS ADOPTED
AND TO ESTABLISH FINDINGS OF FACT TO SUPPORT
THE IMPOSITION OF REQUIREMENTS GREATER THAN REQUIREMENTS
ESTABLISHED BY THE STATE BUILDING STANDARDS CODE
WHEREAS, it is the desire and intent of the City Council of the
City of San Luis Obispo to provide citizens with the greatest
degree of life and structural safety in unreinforced masonry
buildings in the most cost effective manner by amending the 1988
editions of the Uniform Building Code and Uniform Building Code
Standards as adopted to add requirements for strengthening
buildings of unreinforced masonry construction; and
WHEREAS, the California Health and Safety Code, Chapter 4, Part
1.5, Division XIII, Section 17958, Section 17958.5 and Section
17958.7 requires the City Council, before making any modifications
or changes to the State Building Standards Code pursuant to Health
and Safety Code Section 17958.5, to make an express finding that
each such modification or changer is needed; and,
WHEREAS, the California Health and Safety Code Section 17958.5
requires that such changes must be determined to be reasonably
necessary because of local climatic, geological, or topographical
conditions; and,
WHEREAS, such findings must be made available as a public record
and a copy thereof with each such modification or change shall be
filed with the State of California Department of Housing and
Community Development; and
WHEREAS, the City Council of the City of San Luis Obispo hereby
determines that the addition of Division III of Appendix Chapter
23 to the 1988 Uniform Building Code and Standards No. 24 -40, 24-
41, and 24 -42 to the 1988 Uniform Building Code Standards due to
the findings contained herein are greater requirements than those
set forth in the California State Building Standards Code; and
WHEREAS, the City Council of the City of San Luis Obispo finds that
each of the changes or modifications to measures referred to herein
are reasonably necessary because of local climatic, geological, or
topographical conditions in the area encompassed by the boundaries
of the City of San Luis Obispo, and that the following findings
support the local necessity for the changes or modifications:
FINDING 1
That the City of San Luis Obispo contains approximately 137
buildings considered to be of unreinforced masonry construction
Ordinance No. (1991 Series)
Page 2
and defined as "potentially hazardous" during a seismic event. An
unreinforced masonry building has proven to be particularly
susceptible to damage during an earthquake. The protection of
occupants in potentially hazardous buildings and the general public
and preservation of property in the event of such occurrence
support the imposition'of structural requirements greater than
those set forth in the California State Building Standards Code and
in particular support the addition of Appendix Chapter 23- Division
III to the 1988 Uniform Building Code.
FINDING 2
That the City of San Luis Obispo is situated near three major
faults each capable of generating earthquakes with a magnitude of
7.5. These are the San Andreas to the east of the City, the
Nacimiento - Rinconada that crosses Hwy 101 north of the City then
parallels the City to the east, and the Hosgri to the West.. Other
faults of importance are the Huasna and West Huasna to the
Southeast of the City, the San Simeon to the Northwest, and the
Edna and Edna Extended faults which enter the southern areas of
the City. In as much as these faults are included as major
California earthquake faults, which are subject to becoming active
at any time, the City of San Luis Obispo is particularly vulnerable
to devastation should such an earthquake occur. The protection of
human life and the preservation-of property in the event of such
an occurrence support the imposition structural requirements not
set forth in the California State Building Standards Code and in
particular support the addition of Appendix Chapter 23- Division
III to the 1988 Uniform Building Code.
FINDING 3
That the City of San Luis Obispo is located in Seismic Zone 4 and
is subject to the provisions of Chapter 12.2, Division 1 of Title
2 of the Government Code. Government Code Section 8875 et seq.
requires that the City establish a mitigation program to reduce the
hazards associated with unreinforced masonry buildings. The
mandate by the State of California to mitigate the hazards of such
buildings supports the imposition of structural requirements
greater than those set forth in the California State Building
Standards Code, and in particular, supports the addition of.
Appendix Chapter 23- Division III to the 1988 Uniform Building Code.
FINDING 4
That adoption of the Ordinance in and of itself will not have the
potential for environmental effects. Most seismic strengthening
projects will not be visible on the exterior of the involved
structure, requiring ministerial approval of building permits for
attachment of the roof structure to walls and similar operations.
Those projects involving change of occupancy, architectural review,
or more extensive permit activity will require specific
environmental review prior to their approval.
Ordinance No. (1991 Series)
Page 3
NOW THEREFORE BE IT ORDAINED by the City Council of the City Of San
Luis Obispo that the provisions of the State Building Standards
Code are hereby modified, changed and amended, as provided for
herein, based upon the foregoing findings and the public interest
in protecting life•and preserving public safety and property, as
follows:
SECTION 1. Chapter 15.04 of Title 15 of the San Luis Obispo
Municipal Code is hereby amended by adding subsection Q to
Section 15.04.040 as follows.
SECTION 15.04.040 AMENDMENTS; UNIFORM BUILDING CODE
Q. Amend the Appendix to Chapter 23 by adding Division III
to read as follows:
Chapter 23
Division III
SEISMIC STRENGTHENING PROVISIONS FOR
UNREINFORCED MASONRY BUILDINGS
Purpose
Section A2301. The purpose of this Chapter is to promote public
safety and welfare by reducing the risk of death or injury that
may result from the effects of earthquakes on existing buildings
of unreinforced masonry wall construction.
The provisions of this Chapter are intended as minimum standards
for structural seismic resistance established primarily to reduce
the risk of life loss or injury. Compliance with these standards
will not necessarily prevent loss of life or injury or prevent
earthquake damage to rehabilitated buildings.
Scope
Section A2302. The provisions of this Chapter shall apply to all
existing buildings having at least one unreinforced masonry wall.
Except as provided herein, all other provisions of the Building
Code shall apply.
EXCEPTION: This Chapter shall not apply to detached one or
two family dwellings and detached apartment houses
containing less than 5 dwelling units and used solely for
residential purposes.
Definitions
Section A2303. For the purposes of this Chapter, the applicable
definitions in the Building Code shall also apply.
COLLAR JOINT is the vertical space between adjacent wythes and
/ %-I I
Ordinance No. 1991 Series)
Page 4
may contain mortar.
CROSSWALL is a wall that meets the requirements of Section
A2309(d)3. A crosswall is not a shear wall.
CROSSWALL SHEAR CAPACITY is the length of the crosswall• times the
allowable shear value, VcLc.
DIAPHRAGM EDGE is the intersection of the horizontal diaphragm
and a shear wall or other line of shear collection.
DIAPHRAGM SHEAR CAPACITY is the depth of the diaphragm times the
allowable shear value, vUD.
FLEXIBLE DIAPHRAGM is a diaphragm of wood construction or other
construction of similar flexibility.
NORMAL WALL is a wall perpendicular to the direction of seismic
forces.
OPEN FRONT is an exterior building wall plane on one side only
without vertical elements of the lateral force resisting system
in one or more stories.
POINTING is the partial reconstfuction of the bed joints of a URM
wall as defined in U.B.C. Standard No. 24 -42.
UNREINFORCED MASONRY (URM) WALL is a masonry wall in which the
area of reinforcing steel is less than 25 percent of the minimum
required by the Building Code for reinforced masonry.
UNREINFORCED MASONRY BEARING WALL. A URM wall which provides the
vertical support for a floor or roof for which the total
superimposed load exceeds 100 pounds per linear foot of wall.
YIELD STORY DRIFT is the lateral displacement of one level
relative to the level above or below at which yield stress is
first developed in a frame member.
Symbols and Notations
Section A2304. For the purposes of this Chapter, the applicable
symbols and notations in the Building Code shall also apply.
A = Area of unreinforced masonry pier, square inches.
Ae = Area of the bed joints above and below the test
specimen for each in -place shear test.
C = Numerical coefficient specified in Table A23 -A of this
Chapter.
D = In -plane width dimension of pier, inches, or depth of
/�;-12.
Ordinance No. (1991 Series)
Page 5
diaphragm, feet.
DCR = Demand - capacity ratio specified in Section A2309(d).
Fp = Wall anchor tension force, pounds.
FWx = Force applied to a wall at level x, pounds.
H = Least clear height of opening on either side of pier,
inches.
h/t = Height /thickness ratio of URM wall. Height h is
measured between wall anchorage levels and /or slab -on-
grade.
L = Span of diaphragm between shear walls, or span between
shear wall and open front, feet.
LC = Length of crosswall, feet.
Li = Effective span for an open front building specified in
Section A2309(d)7, feet.
Pp = Superimposed dead load at the top of the pier under
consideration, pounds
Pd = Axial dead load pressure, pounds per square inch.
PW = Weight of wall, pounds.
Va = The allowable shear in any URM pier, pounds.
Vcb = Total shear capacity of crosswalls in the direction of
analysis immediately below the diaphragm level being
investigated, EvCLC, pounds.
VC8 = Total shear capacity of crosswalls in the direction of
analysis immediately above the diaphragm level being
investigated, EvCLC, pounds.
Vr = 0.5Pp(D /H), the rocking shear of any URM wall or wall
pier, pounds.
VW = Total shear force resisted by a shear wall at the level
under consideration, pounds.
VP = Shear force assigned to a pier on the basis of its
relative shear rigidity, pounds.
VS = Shear force assigned to a spandrel on the basis of the
shear forces in the adjacent wall piers and tributary
dead plus live loads.
Vtesc = Load in pounds at incipient slipping for each in -place
/5 -13
Ordinance No. 11991 Series)
Page 6
shear test per Section A2306(c)3A.
ve = Allowable shear stress for unreinforced masonry, pounds
per square inch.
vc = Allowable shear value for a crosswall sheathed with any
of the materials given in Tables A23 -C or A23 -D, pounds
per foot-.
vt = Mortar shear strength as specified in.Section
A2306(c)3D.
vto = Mortar shear test values as specified in Section
A2306(c)3D.
vu = Allowable shear value for a diaphragm sheathed with any
of the materials given in Tables A23 -C or A23 -D, pounds
per foot.
EVuD = Sum of diaphragm shear capacities of both "ends of the
diaphragm.
EEVUD= For diaphragms coupled with crosswalls EEv,D includes
the sum of shear capacities of both ends of diaphragms
coupled at and above the level under consideration.
Wd = Total dead load tributary to a diaphragm, pounds.
EWd = Total deal load tributary to all of the diaphragms at
and above the level under consideration, pounds.
WP Wall dead load tributary to an anchor, pounds.
Ww = Total dead load of an unreinforced masonry wall above
the level under consideration or above an open front of
a building, pounds.
Wwx = Dead load of a URM wall assigned to Level x halfway
above and below the level under consideration.
Z = The Seismic Zone Factor for Seismic Zone 3 specified in
Table 23 -I of the Building Code.
General Requirements
Section A2305. (a) General. All buildings shall have a seismic
resisting system conforming with Section 2303(b) of the Building
Code, except as modified by this Chapter.
(b) Alterations and Repairs. Alterations and repairs required
to meet the provisions of this Chapter shall comply with all
other applicable requirements of the Building Code unless
specifically provided for in this Chapter.
/0-4
Ordinance No.
Page 7
(c) Requirements
information shall
Chapter:
(1991 Series)
for Plans. The following construction
be included in the plans required by this
1. Accurately dimensioned floor and roof plans showing
existing walls and the size and spacing of floor and roof
framing members and sheathing materials. The plans shall
indicate all existing and new crosswalls and their materials
of construction. The location of the crosswalls and their
openings shall be fully dimensioned or drawn to scale on the
plans.
2. Accurately dimensioned wall elevations showing
openings, piers, thicknesses, and heights, wall shear test
locations, cracks or damaged portions requiring repairs.
The general condition of the mortar joints and if and where
the joints require pointing. Where the exterior face is
veneer, the type of veneer, its thickness and its bonding
and /or ties to the structural wall masonry shall also be
reported.
3. The type of interior wall and ceiling surfaces.
4. The extent and type of existing wall anchorage to
floors and roof when utilized in the design.
5. The extent and type of parapet corrections which were
previously performed, if any.
6. Repair details, if any, of cracked or damaged
unreinforced masonry walls required to resist forces
specified in the Chapter.
7. All other plans, sections, and details necessary to
delineate required retrofit construction including those
items in Section A2310.
Material Requirements
Section A2306. (a) General. All materials permitted by this
Chapter, including their appropriate allowable design values and
those existing configurations of materials specified herein, may
be utilized to meet the requirements of this Chapter.
(b) Existing Materials. All existing materials utilized as part
of the required force resisting system shall be in sound
condition or shall be repaired or removed and replaced with new
material.
(c) Existing unreinforced Masonry.
1. General. All unreinforced masonry walls utilized to
carry vertical loads or seismic forces parallel and
/$-1,5
Ordinance No. (1991 Series)
Page 8
perpendicular to the wall plane shall be tested as specified
in this subsection. All masonry that does not meet or
exceed the minimum standards established by this Chapter
shall be removed and replaced by new materials or
alternatively shall have its structural functions replaced
by new materials and shall be anchored to supporting
elements.
2. Lay -Up of Walls. The facing and backing shall be
bonded so that not less than 10 percent of the exposed face
area is composed of solid headers extending not less than 4
inches into the backing. The clear distance between
adjacent full- length headers shall not exceed 24 inches
vertically or horizontally. Where the backing consists of
two or more wythes, the headers shall extend not less than 4
inches into the most distant wythe or the backing wythes
shall be bonded together with separate headers whose area
and spacing conform to the foregoing. Wythes of walls not
bonded as described above shall be considered as veneer.
Veneer wythes shall not be included in the effective
thickness.used in calculating the height to thickness and
the shear capacity of the wall.
EXCEPTION: Veneer wythes, anchored as specified by the
Building Code and made composite with backup masonry,
can be used for calculation of the effective thickness.
3. Mortar.
A. Tests. The quality of mortar in all masonry walls
shall be determined by performing in -place shear texts
in accordance with U.B.C. Standard No. 24 -40.
Alternative methods of testing may be approved by the
Building Official for masonry walls other than brick.
B. Location of Tests. The shear tests shall be taken
at locations representative of the mortar conditions
throughout the entire building, taking into account
variations in workmanship at different building height
levels, variations in weathering of the exterior
surfaces, and variations in the condition of the
interior water and /or by the deleterious effects of
other substances contained within the building. The
exact test location shall be determined at the building
site by the engineer in responsible charge of the
structural design work. An accurate record of all such
tests and their location in the building shall be
recorded and these results shall be submitted to the
Building Department for approval as part of the
structural analysis.
C. Number of Tests. The minimum number of tests
shall be as follows:
/,6 -1(40
Ordinance No. (1991 Series)
Page 9
(1) At each of both the first and top stories,
not less than two per wall or line of wall
elements providing a common line of resistance to
lateral forces.
(2) At each of all other stories, not less than
one per wall or line of wall elements providing a
common line of resistance to lateral forces.
(3) When grouted or chemically set tension
anchors are utilized above the roof line
additional in -plane shear tests shall be performed
above the intersection of the roof sheathing with
the wall. The test locations shall be distributed
around the perimeter of the building such that a
minimum of one test is performed in each
predominant wall direction. The minimum quality
mortar in each of the shear tests shall not be
less than 50 psi.
(4) In any case, not less than one per 1500
square feet of wall surface nor less than a total
of eight.
D. Minimum Quality Mortar.
(1) Mortar shear test values, vto, in psi shall
be obtained for each in -place shear test in
accordance with the following equation:
vto = (vtest /Ab ) -Pd .................. (A23 -1)
(2) The mortar shear strength, vt, is the value
in psi that is exceeded by 80% of all of the
mortar shear test values, vto .
(3) Unreinforced masonry with mortar shear
strength, vt, less than 30 psi shall be removed or
pointed and retested.
E. Collar Joints. The collar joints shall be
inspected at the test locations during each in -place
shear test, and estimates of the percentage of the
surfaces of adjacent wythes which are covered with
mortar shall be reported along with the results of the
in -place shear tests.
F. Pointing. All deteriorated mortar joints in
unreinforced masonry walls shall be pointed according
to U.B.C. Standard No. 24 -42. Nothing shall prevent
pointing with mortar of all the masonry wall joints
before the tests are made, except as required by
Section A2307(a). Alternative methods of pointing may
be used with prior approval of the Building Official.
/ X-�/ 7
Ordinance No. 11991 Series)
Page 10
(d) Existing wall Anchors. Existing wall floor anchors, if
found to be acceptable by testing, may be utilized in the design.
Anchors utilized as all or part of the required tension anchors
shall be tested in pullout according to U.B.C. Standard No. 24-
41. The minimum number of anchors tested shall be four per
floor, with two tests at walls with joists framing into the wall
and two tests at walls with joists parallel to the wall, but not
less than ten percent of the total number of existing tension
anchors at each level.
Quality Control
Section A2307. (a) Pointing. All preparation and mortar
pointing shall be performed with special inspection.
EXCEPTION: At the discretion of the Building Official,
incidental pointing may be performed without special
inspection.
(b) New Bolts. One- fourth of all new shear bolts and combined
tension and shear bolts in unreinforced masonry walls shall be
tested-according to U.B.C. Standard 24 -41.
EXCEPTION: Special inspection may be provided during
installation in lieu of testing.
(c) New Anchors. All installation of grouted or chemically set
tension anchors shall be performed with special inspection.
Allowable Design Values
Section A2308. (a) Allowable Values.
1. Allowable values for existing materials are given in
Table A23-C and for new materials in Table A23 -D.
2. Allowable values not specified in this Chapter shall be
as specified elsewhere in the Building Code.
(b) Masonry Shear. The allowable unreinforced masonry shear
stress, v., shall be determined from the following equation:
ve = 0.lvt + 0. 15PD/ A ....... ........................(A23 -2)
The mortar shear test value, vt, shall be determined in
accordance with Section A2306(c)3, and shall not exceed 100 psi
for the determination of v..
The one -third increase in allowable values of the Building Code
is not allowed for v..
(c) Masonry Compression. Where any increase in dead plus live
/ -l8
Ordinance No. (1991 Series)
Page 11
compression stress occurs the allowable compression stress in
unreinforced masonry shall not exceed 100 psi. The one -third
increase in allowable stress of the Building Code is allowed.
(d) Masonry Tension. Unreinforced masonry shall be assumed as
having no tensile capacity.
(e) Existing Tension Anchors. The allowable resistance values
of the existing anchors shall be 40 percent of the average of the
tension tests of existing anchors having the same wall thickness
and joist orientation. The one -third increase in allowable
stress of the Building Code is not allowed for existing tension
anchors.
(f) Foundations. For existing foundations new total loads may
be increased over existing loads by 25 percent. New total dead
load plus live load plus seismic forces may be increased over
existing dead load plus live load by 50 percent. Higher values
may be justified only in conjunction with a geotechnical
investigation.
Analysis and Design
Section A2309. (a) General. Except as modified herein, the
analysis and design relating to the structural alteration of
existing buildings shall be in accordance with the Building Code.
(b) Selection of Procedure. Buildings shall be analyzed by the
General Procedure of Section A2309(c) which is based on Chapter
23 of the Building Code, or when applicable, buildings may be
analyzed by the Special Procedure of A2309(d). Unreinforced
masonry bearing wall buildings constructed of hollow concrete or
clay tile shall be analyzed-by the general procedures unless it
can be shown by testing that all masonry units were manufactured
and installed in compliance with U.B.C. Standards No. 24 -4 or 24-
8 as applicable for bearing type units and that the capacity of
the wall in bearing and shear, based on the net area in contact
through the bed joints, is not less than that allowed for solid
bricks, in which case the special procedure may be used.
Buildings with a substantially complete steel or concrete frame
capable of supporting gravity dead and live loads and that
utilize unreinforced masonry walls as non - bearing infill between
frame members shall be analyzed by a procedure approved by the
building official. Qualified historic structures may be analyzed
per Title 24, California Administrative Code, Part 8, State
Historical Building Code.
(c) General Procedure.
1. Minimum Design Lateral Forces. Buildings shall be
analyzed to resist minimum lateral forces assumed to act
noncurrently in-the direction of each of the main axes of
the structure in accordance with the following:
/;5-19
Ordinance No. k1991 Series)
Page 12
V = 0. 33ZW ............. ........................(A23 -3)
2. Lateral Forces on Elements of Structures. Parts or
portions of structures shall be analyzed as required in
Chapter 23 of the Building Code.
EXCEPTIONS: 1. Unreinforced masonry walls for which
height -to- thickness ratios do not exceed ratios set
forth in Table A23 -B need not be analyzed for out -of-
plane loading. Unreinforced masonry walls which exceed
the allowable h/t ratios of Table A23 -B shall be braced
according to Section A2310(e).
2. Parapets complying with Section A2310(f) need not
be analyzed for out -of -plane loading.
3. Shear Walls (In -Plane Loading). Shear walls shall
comply with subsection A2309(e).
(d) Special Procedure.
1. Limits for the Application of Subsection A2309(d). The
Special Procedure of this subsection may only be applied to
buildings with the following characteristics:
A. Flexible diaphragms at all levels above the base
of the structure.
B. A maximum of 6 stories above the base of the
building.
C. The vertical elements of the lateral force
resisting system shall consist predominantly of masonry
or concrete shear walls.
D. New vertical elements of the lateral force
resisting system consisting of steel braced frames or
special moment resisting frames shall have a maximum
overall height -to- length ratio of 1 -1/2 to 1.
E. A minimum of two lines of vertical elements of the
lateral force resisting system shall be parallel to
each axes of the building except for single -story
buildings with an open front on one side only. (See
Section A2309(d)8 for open front buildings.)
2. Lateral Forces on Elements of Structures. With the
exception of the diaphragm provisions in subsection
12309(d), elements of structures shall comply with
subsection A2309(c)2.
3. Crosswalls. Crosswalls shall meet the requirements of
this subsection.
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Ordinance No. (1991 Series)
Page 13
A. Crosswall Definition. A crosswall is a wood -
framed wall sheathed with any of the materials
described in Tables A23 -C or A23 -D. Spacing of
crosswalls shall not exceed 40 feet on center measured
perpendicular to the direction of consideration, and
shall be placed in each story of the building.
Crosswalls shall extend the full story height between
diaphragms.
EXCEPTIONS: 1. Crosswalls need not be provided
at all levels in accordance with subsection
A2309(d)4B(iv).
2. Existing crosswalls need not be continuous
below a wood diaphragm at /or within four feet of
grade provided:
(i) Shear connection requirements Section
A2309(d)5 are satisfied at all edges of the
diaphragm.
(ii) Crosswalls with total shear capacity of
0.20ZEWa interconnect the diaphragm to the
foundation.
(iii) The demand /capacity ratio of the
diaphragm between the crosswalls that are
continuous to their foundations shall be
calculated as:
DCR = (0.75ZWd + Vca 1/2VuD...... (A23 -4)
and DCR shall not exceed 2.5.
B. Crosswall Shear Capacity.
measured along the span of the
the crosswall shear capacities
percent of the diaphragm shear
strongest diaphragm at or abov,
consideration.
Within any 40 feet
diaphragm, the sum of
shall be at least 30
capacity of the
the level under
C. Existing Crosswalls. Existing crosswalls shall
have a length -to- height ratio between openings of not
less than 1.5. Existing crosswall connections to
diaphragms need not be investigated as long as the
crosswall extends to the framing of the diaphragm above
and below.
D. New Crosswalls. New crosswall connections to the
diaphragm shall develop the crosswall shear capacity.
New crosswalls shall have the capacity to resist an
overturning moment equal to the crosswall shear
capacity times the story height. Crosswall overturning
moments need not be cumulative over more than two
10-2.1
ordinance No. X1991 Series)
Page 14
stories.
E. other Crosswall Systems. Other systems such as
special moment resisting frames may be used as
crosswalls provided that the yield story drift does not
exceed 1 inch in any story.
4. Wood Diaphragms.
A. Acceptable Diaphragm Span. A diaphragm is
acceptable if the point (L,DCR) on Figure A23 -1 falls
within Regions 1, 2 or 3.
B. Demand- Capacity Ratios. Demand - Capacity Ratios
shall be calculated for the diaphragm according to the
following formulas:
(i) For a diaphragm without qualifying crosswalls
at levels immediately above or below:
DCR = 0. 75ZWd /Ev,D ..................(A23 -5)
(ii) For a diaphragm in a single -story building
with qualifying crosswalls:
DCR = 0.75ZWd /(EvuD + Vcb) .......... (A23 -6)
(iii) For diaphragms in a multi -story building
with qualifying crosswalls in all levels:
DCR = 0.75ZEWd /(EEvuD + Vcb) ......... (A23 -7)
DCR shall be calculated at each level for the set
of diaphragms at and above the level under
consideration. In addition, roof diaphragm shall
also meet the requirements of Formula A23 -6.
(iv) For a roof diaphragm and the diaphragms
directly below if coupled by crosswalls:
DCR = 0.75ZEWd /EEvuD .................. (A23 -8)
C. Chords. An analysis for diaphragm flexure need
not be made and chords need not be provided.
D. Collectors. An analysis, of diaphragm collector
forces shall be made for the transfer of diaphragm edge
shears into vertical elements of the lateral force
resisting system. Collector forces may be resisted by
new or existing elements.
E. Diaphragm openings.
(i) Diaphragm forces at corners of openings shall
16-22-,.
Ordinance No. (1991 Series)
Page 15
be investigated and shall be developed into the
diaphragm by new or existing materials.
(ii) In addition to calculating demand - capacity
ratios per Section A2309(d)4B, the demand - capacity
ratio of the portion of the diaphragm adjacent to
an opening shall be calculated using the opening
dimension as the span.
(iii) Where an opening occurs in the end quarter
of the diaphragm span, v D for the demand - capacity
ratio calculation shall to based on the net depth
of the diaphragm.
5. Diaphragm Shear Transfer. Diaphragms shall be
connected to shear walls with connections capable of
developing a minimum force given by the lesser of the
following formulas:
V = 0. 50ZCpWd .......... ........................(A23 -9)
using C values of Table No.. 23 -A, or
V = VUD ..............- .......................(A23 -10)
6. Shear Walls (In -Place Loading) - Special Procedure.
A. Wall Story Force. The wall story force
distributed to a shear wall at any diaphragm level
shall be the lesser value calculated as:
(i) For buildings without crosswalls:
FwX = 0.33Z(WWX +Wd /2) ............. (A23 -11)
but need not exceed
FwX = 0.33ZWWX + VUD ................(A23 -12)
(ii) For buildings with crosswalls in all levels:
FWX = 0.25Z( Wax +Wd /2) ...............(A23 -13)
but need not exceed
FUX = 0.25Z (WWX +EWd (vuD /EEvuD+Vcb )) .. (A23 -14)
and need not exceed
FwX = 0.25ZWWX + VUD ................(A23 -15)
B. Wall Story Shear. The wall story shear shall be
the sum of the wall story forces at and above the level
of consideration.
/ O -Z3
Ordinance No. (1991 Series)
Page 16
Vwx = EFwx ........ .......................(A23 -16)
C. Shear Wall Analysis. Shear walls shall comply
with subsection A2309(e).
D. Moment Frames.
shear walls shall be
of the Building Code
specified in Section
drift ratio shall be
further limited in S,
Moment frames used in place of
designed as required in Chapter 23
except that the forces shall be as
A2309(d)6A and the interstory
limited to 0.005 except as for
2ction A2309(e)3B.
7. Buildings with Open Fronts. A building with an open
front on one side shall, have crosswalls parallel to the open
front and shall be designed by the following procedure:
A. Effective Diaphragm Span, L,, for use in Figure
A23 -1 shall be determined in accordance with the
following formula:
Li = 2[(Ww /Wd) x L + L] ..................(A23 -17)
B. Diaphragm demand - capacity ratio shall be
calculated as:
DCR = 0.75Z9Wd + Ww) /((vuD) + Vc] ........ (A23 -18)
(e) Analysis of Vertical Elements of the Lateral Force - Resisting
System. Applicable to both General Procedure and Special
Procedure Buildings.
1. Existing URM Walls.
A. Flexural Rigidity. Flexural components of
deflections may be neglected in determining the
rigidity of a URM wall.
B. Shear Walls with Openings. Wall piers shall be
analyzed according to the following procedure:
(i) For any pier,
(1) The pier shear capacity shall be
calculated as:
Ve = VeA ....................... (A23 -19)
(2) The pier rocking shear capacity shall be
calculated as:
Vr = 0. 5PDD /H ..................(A23 -20)
(ii) The wall piers at any level are acceptable
if they comply with one of the following modes of
/ t -2�f
Ordinance No. (1991 Series)
Page 17
behavior:
(1) Rocking Controlled Mode. When the pier
rocking shear capacity is less than the pier
shear capacity, i.e. Vr < V. for each pier in
a level, forces in the wall at that level,
V ,,x, shall be distributed to each pier, VP,
in proportion to PDD /H.
For the wall at that level:
Vwx < EVE ...................... (A23 -21)
(2) Shear Controlled Mode. Where the pier
shear capacity is less than the pier rocking
capacity, i.e. V. < V�, in at least one pier
in a level, forces in the wall at that level,
VW., shall be distributed to each pier, VP,
in proportion to D /H.
For at least one pier at that level:
VP < Va . .......................(A23 -22)
and
VP < Vr : .......................(A23 -23)
If VP < Va for each pier and V > Vr for one
or more piers, omit such piers from the
analysis and repeat the procedure for the
remaining piers, or strengthen and reanalyze
the wall.
(iii) Masonry Pier Tension Stress. Unreinforced
masonry wall piers need not be analyzed for
tension stress.
C. Shear Walls Without Openings. Shear walls without
openings shall be analyzed as for walls with openings
except that V. shall be calculated as follows:
V _ (0.50Pp + 0. 25Pu )D/H ................(A23 -24)
2. Plywood Sheathed Shear Walls. Plywood sheathed shear
walls may be used to resist lateral forces for buildings
with flexible diaphragms analyzed according to provisions of
Section A2309(c). Plywood sheathed shear walls may not be
used to share lateral loads with other materials along the
same line of resistance.
3. Combination of Vertical Elements
A. Lateral Force Distribution. Lateral forces shall
be distributed among the vertical resisting elements in
proportion to their relative rigidities, except that
/ $-zs
Ordinance No. (1991 Series)
Page 18
moment frames shall comply with Section A2309(e)3B.
B. Moment Resisting Frames. A moment frame shall not
be used with a URM wall in a single line of resistance
unless the wall(s) have piers that are capable of
sustaining rocking in accordance with Section
A2309(e)1B and the frames are designed to carry 100
percent of the lateral forces, and the interstory drift
ratio shall be limited to .0025.
Detailed System Design Requirements
Section A2310. (a) Wall Anchorage.
1. Anchorage Locations. All unreinforced masonry walls
shall be anchored at the roof and floor levels as required
in Section A2309(c)2. Ceilings with substantial rigidity
and abutting masonry walls shall be connected to walls with
tension bolts at a maximum anchor spacing of 6 feet.
Ceiling systems with substantial mass shall be braced at the
perimeter to diaphragms.
2. Anchor Requirements. Anchors shall be tension bolts
through the wall as specified in Table No. A23 -D, or by an
approved equivalent at a maximum anchor spacing of 6 feet.
All existing wall anchors shall be secured to the joists to
develop the required forces.
3. Minimum Wall Anchorage. Anchorage of masonry walls to
each floor or roof shall resist a minimum force determined
by:
F = ZCpWp ............. .......................(A23 -25)
or 200 pounds per linear foot, whichever is greater, acting
normal to the wall at the level of the floor or roof.
Existing floor wall anchors must meet or must be upgraded to
meet the requirements of this Chapter if utilized in the
design. Existing embedded roof anchors shall not be
utilized in the design.
4. Anchors at Corners. At the roof and all floor levels,
both shear and tension anchors shall be provided within 2
feet horizontally from the inside of the corners of the
walls.
5. Anchors with Limited Access. When access to the
exterior face of the masonry wall is prevented by proximity
of.an existing building, wall anchors conforming to Item 5b
in Table A23 -D may be used.
(b) Diaphragm shear Transfer. Shear bolt spacing shall not
exceed 6 feet.
Ordinance No. (1991 Series)
Page 19
(c) Collectors. Collector elements shall be provided which are
capable of transferring the seismic forces originating in other
portions of the building to the element providing the resistance
to those forces.
(d) Ties and Continuity. Ties and continuity shall conform to
Section 2312(h)2E of the Building Code.
(e) Wall Bracing.
1. General. Where a wall height -to- thickness ratio
exceeds the specified limits, the wall may be laterally
supported by vertical bracing members per Section A2310(e)2
or by reducing the wall height by bracing per Section
A2310(e)3.
2. Vertical Bracing Members. Vertical bracing members
shall be attached to floor and roof construction for their
design loads independently of required wall anchors.
Horizontal spacing of vertical bracing members shall not
exceed one -half the unsupported height of the wall nor 10
feet. Deflection of such bracing members at design loads
shall not exceed one -tenth of the wall thickness.
3. Wall Height Bracing. The wall height may be reduced by
bracing elements connected to the floor or roof. Horizontal
spacing of the bracing elements and wall anchors shall be as
required by design but shall not exceed 6 feet on center.
Bracing elements shall be detailed to minimize the
horizontal displacement of the wall by the vertical
displacement of the .floor or roof.
(f) Parapets. Parapets and exterior wall appendages not
conforming to this Chapter shall be removed, or stabilized or
braced to ensure that the parapets and appendages remain in their
original position.
The maximum height of an unbraced unreinforced masonry parapet
above the lower of either the level of tension anchors or roof
sheathing, shall not exceed one and one -half (1 -1/2) times the
thickness of the parapet wall. If the required parapet height
exceeds this maximum height, a bracing system designed for the
force factors specified in Table 23 -P of the Building Code for
walls shall support the top of the parapet. Parapet corrective
work must be performed in conjunction with the installation of
tension roof anchors.
The minimum height of a parapet above the wall anchor shall be 12
inches.
EXCEPTION: If a reinforced concrete beam is provided at the
top of the wall, the minimum height above the wall anchor
may be 6 inches.
/ '6 -z7
Ordinance No. (1991 Series)
Page 20
(g) veneer.
1. Unreinforced masonry walls which carry no design loads
other than their own weight may be considered as veneer if
they are.adequately anchored to new supporting elements.
2. Veneer shall be anchored with approved anchor ties,
conforming to the required design capacity specified in the
Building Code and placed at a maximum spacing of 24 inches
with a maximum supported area of 2 square feet.
EXCEPTION: Existing veneer anchor ties may be
acceptable provided the ties are in good condition and
conform to the following minimum size, maximum spacing
and material requirements.
Existing veneer anchor ties shall be corrugated galvanized
iron strips not less than 1 inch in width, 8 inches in
_length and 1/16 of an inch in thickness (1" X 8" X 1/1611) or
equal and shall be located and laid in every alternate
course in the vertical height of the wall at a spacing not
to exceed 17 inches on centers horizontally. As an
alternate, such ties may be laid in every fourth course
vertically at a spacing not to exceed 9 inches on centers
horizontally.
3. The location and condition of existing veneer anchor
ties shall be verified as follows:
A. An approved testing laboratory shall verify the
location and spacing of the ties and shall submit a
report to the Building Official for approval as a part
of the structural analysis.
B. The veneer in a selected area shall be removed to
expose a representative sample of ties (not less than
four) for inspection-by the Building Official.
(h) Truss and Beam Supports. Where trusses and beams other than
rafters or joists are supported on masonry, independent secondary
columns shall be installed to support vertical loads of roof or
floor members. The loads shall be transmitted to adequate
support.
Administrative Provisions
Section A2311. (a) Definitions. For the purposes of this
Chapter, the applicable definitions in the Building Code shall
apply.
(b) Compliance Requirements.
1. The owner of each building within the scope of this
/ ji-26
Ordinance No. (1991 Series)
Page 21
Chapter shall, upon service of an order, cause a structural
analysis to be made of the building by an engineer or
architect licensed by the state to practice as such. Said
analysis shall include the preparation of a report detailing
the investigation, evaluation, test data, conclusions, and
recommendations to establish compliance with this Chapter.
If the building does not comply with seismic standards
established in this Chapter, the report shall specify the
work and cost necessary to structurally alter the building
to conform to such standards. The Building Official shall
establish a basic outline for the format of the report.
2. The owner of a building within the scope of this
Chapter shall comply with the requirements set forth above .
by submitting the analysis report to the Building Official
for review and acceptance within 18 months of the service of
an order.
3. The owner of a building within the scope of this
Chapter shall structurally alter the building to conform to
the seismic standards of this Chapter or cause the building
to be demolished when either of the following occurs: .
A. The value of additions, alterations, and /or
repairs, cumulative from the effective date of this
Chapter, exceeds 50 percent of the replacement value of
the building established by the Building Official per
Section 304(b) of the Uniform Administrative Code.
B. The use of the building changes to a different
division of the same group of occupancy or to a
different occupancy group.
EXCEPTION: Notwithstanding the provisions of
Section 502 of the Building Code, buildings
containing more than one occupancy classification
need not comply with this Chapter if the total
floor area for changes in use, cumulative from the
effective date of this Chapter, does not exceed 50
percent of the floor area of the building.
4. This Chapter does not require alteration of existing
electrical, plumbing, mechanical, or fire safety systems.
(c) Administration,
1. Service of Notice and Order.
A. General. A notice or order issued pursuant to
this section shall be in writing and shall be served
either personally or by certified or registered mail
upon the owner as shown on the last equalized
assessment roll, and upon the person, if any, in
apparent charge or control of the building. The
Ordinance No. ,1991 Series)
Page 22
failure of any such person to receive such notice or
order shall not affect the validity of any proceedings
taken. under this Chapter or relieve any such person
from any duty or obligation imposed on him by the
provisions of this Chapter.
B. Notice. The Building Official shall, within 30
days of the effective date of this Chapter, issue a
notice as provided in this section to the owner of each
building within the scope of this Chapter.
C. Order. The Building Official shall, within 30
days following January 1, 1993, issue an order as
provided in this section to the owner of each building
within the scope of this Chapter. In the event that
changes to the California Building Code or passage of
any State law conflict with the provisions of this
Chapter, or if the validity of the use of Seismic Zone
3 criteria in this Chapter is uncertain, the Building
Official shall defer issuance of the order until said
conflict or uncertainty is satisfactorily resolved.
2. Content of Notice and Order.
A. General. The notice or order shall be accompanied
by a copy of Section A2311(b), which sets forth the
owner's responsibilities.
B. Notice. The notice shall specify that the
building has been determined by the Building Official
to be within the scope of this Chapter and, therefore,
is subject to the minimum seismic standards of this
Chapter.
C. Order. The order shall direct
and submit to the Building Official
analysis required by this Chapter.
the owner to obtain
the structural
3. Appeal. The owner of the building may appeal the
Building Official's initial determination that the building
is within the scope of this Chapter to the Board of Appeals
established by Section 204 of the Uniform Administrative
Code. Such appeal shall be filed with the Board within 60
days from the service date of the order described in Section
A2311(c)2. Appeals or requests for modifications from any
other determinations, orders or actions by the Building
Official pursuant to the Chapter shall be made in accordance
with the procedures established in Sections 107, 108 and 204
of the Uniform Administrative Code. Any appeal shall be
decided by the Board no later than 90 days after filing and
the grounds thereof shall be stated clearly and concisely.
4. Recordation. At the time that the Building official
serves the aforementioned notice, the Building Official
/ r &a
Ordinance No. (1991 Series)
Page 23
shall also file and record with the office of the county
recorder a certificate stating that the subject building is.
within the scope of-this Chapter and is a potentially
earthquake hazardous building. The certificate shall also
state that the owner thereof will be ordered to structurally
analyze the building to determine compliance with this
Chapter.
If the building is either demolished, found not to be within
the scope of this Chapter, or is structurally capable of
resisting minimum seismic forces required by this Chapter as
a result of structural alterations or an analysis, the
Building official shall file and record with the office of
the county recorder a form terminating the status of the
subject building as being classified within the scope of
this Chapter.
5. Enforcement. If the owner in charge or control of the
subject building fails to comply with any order issued by
the Building Official pursuant to this Chapter within the
time limit set forth in Section A2311(b), the Building
Official shall verify that the record owner of this building
has been properly served. If the order has been served on
the record owner, then the Building Official shall order
that the entire building bT vacated and that the building
remain vacated until such order has been complied with. If
compliance with such order has not been accomplished within
90 days after the date the building has been ordered vacated
or such additional time as may have been granted by the
Board of Appeals,. the Building Official may order its
demolition in accordance with the provisions of section 203
of the Uniform Administrative Code.
6. Annual Report. During January of each year, the
Building Official shall submit a report to the City Council
outlining the progress to date concerning reduction of the
hazards presented by the unreinforced masonry building
inventory for the City. The report shall include:
A. The number of unreinforced masonry buildings
strengthened, demolished, or otherwise eliminated from
the inventory;
B. The number of unreinforced masonry buildings
remaining on the inventory,.including the status of
orders issued pursuant to this Chapter that are not
resolved.
/ -3/
Ordinance No. 1991 Series)
Page 24
TABLE NO. A23 -A
HORIZONTAL FORCE FACTOR C
CONFIGURATION OF MATERIALS
Roofs with straight or diagonal sheathing and
roofing applied directly to the sheathing or
floors with straight tongue- and - groove sheathing
Diaphragm of double or multiple layers of boards
with edges offset or blocked plywood systems
Wall anchors
TABLE NO. A23 -B
MAXIMUM HEIGHT -TO- THICKNESS RATIO OF
UNREINFORCED MASONRY WALLS
WALL TYPES H/T RATIO
Walls of one -story buildings 20
First -story wall of multi- 20
story buildings
Walls in top story of multi- 14
story buildings
All other walls 22
TABLE NO. A23 -C
ALLOWABLE VALUES FOR EXISTING MATERIALS
C
0.6
0.83
0.8
EXISTING MATERIALS OR CON-
FIGURATIONS OF MATERIALS ALLOWABLE VALUES
1. HORIZONTAL DIAPHRAGMS
a. Roofs with straight sheathing and 100 lbs. per foot
roofing applied directly to the for seismic shear
sheathing.
b. Roofs with diagonal sheathing and 250 lbs. per foot
roofing applied directly to the for seismic shear
sheathing.
C. Floors
with straight tongue -and-
100
lbs. per foot
groove
sheathing.
for
seismic shear
d. Floors
with straight sheathing and
500
lbs. per foot
finished
wood flooring with board
for
seismic shear
edges
offset of perpendicular.
Ordinance No. (1991 Series)
Page 25
TABLE NO. A23 -C
ALLOWABLE VALUES FOR EXISTING MATERIALS
(continued)
EXISTING MATERIALS OR CON-
FIGURATIONS OF MATERIALS
ALLOWABLE VALUES
e. Floors with diagonal sheathing and 600 lbs. per foot
wood flooring. for seismic shear
2. CROSSWALLS2.4
a. Plaster on wood or metal lath 200 lbs. per foot
per' side for
seismic shear
b.
Plaster on gypsum lath
175 lbs. per foot
for seismic shear
C.
Gypsum wall board,
75 lbs. per foot
unblocked edges
for seismic shear
d.
Gypsum wall board,
125 lbs. per foot
blocked edges
for seismic shear
3.
EXISTING FOOTINGS, WOOD FRAMING,
REINFORCING STEEL, AND
STRUCTURAL STEEL
a.
Plain concrete footings
f'c = 1500 psi
unless otherwise
shown by tests
b.
Douglas fir wood
Allowable stress
same as No. 1 D.F.
C.
Reinforcing steel
ft = 18,000 lbs.
per square inch
maximum.3
d.
Structural steel
ft = 20,000 lbs.
per square inch
maximum.3
Material must be sound and in good
condition.
2 Shear values of these materials may be combined, except the
total combined value shall not exceed 300 lbs. per foot.
3 Stresses given may be increased for combinations of loads as
specified in the Building Code.
4 A one -third increase in allowable stress is not allowed.
6 -33
Ordinance No. ,1991 Series)
Page 26
TABLE NO. A23 -D
ALLOWABLE VALUES OF NEW MATERIALS USED
IN CONJUNCTION WITH EXISTING CONSTRUCTION
NEW MATERIALS OR CONFIGURATIONS ALLOWABLE VALUES4
OF MATERIALS
1. HORIZONTAL DIAPHRAGMS
Plywood sheathing applied directly 225 lbs. per foot
over straight sheathing with plywood
ends bearing on joists or rafters
and plywood edges located on center
of individual sheathing boards.
2. CROSSWALLS4
a. Plywood sheathing applied directly
over wood studs. No value shall be
given to plywood applied over
existing plaster or wood sheathing.
C.
3.
4.
5.
Drywall or plaster applied directly
over wood studs.
Drywall or plaster applied to
sheathing over existing
wood studs.
TENSION BOLTS
Value specified
in Table No. 25 -K -1
of the Building Code
for shear walls.
100 percent of values
in Table No. 47 -I of
the Building Code.
50 percent of values
in Table No. 47 -I of
the Building Code.
Bolts extending entirely through 1800 lbs. per bolt,
masonry walls with bearing plates 900 lbs. for 2 wythe
at least 30 sq. inches in area on
far side of a 3 wythe minimum wall.
2,3
SHEAR BOLTS
Bolts embedded a minimum of 8 inches
into unreinforced masonry walls.
Bolts shall be centered in 2 -1/2
inch - diameter hole with dry -pack or
non - shrink grout around
circumference of bolt. 1,3,5
COMBINED TENSION AND SHEAR BOLTS
a. Through Bolts - Combined Shear and
Tension Bolts meeting the above
requirements for tension bolts and
shear bolts. 1,2,3,5
b. Embedded Bolts - Combined Shear and
133 percent of value
specified in Table No.
24 -E of the Building
Code. Value used shall
not exceed that given
for 3/4 inch bolts.
Tension: Same as for
tension bolts.
Shear: Same as for
shear bolts.
Tension: 1200 lbs.
Ordinance No. (1991 Series)
Page 27
TABLE NO. A23 -D
ALLOWABLE VALUES OF NEW MATERIALS USED
IN CONJUNCTION WITH EXISTING CONSTRUCTION
(continued)
NEW MATERIALS OR CONFIGURATIONS
OF MATERIALS
Tension Bolts extending to exterior
face of wall with 2 -1/2 inch round
plate under the head, drilled at an
angle of 22 -1/2 degrees to the
horizontal, and installed as
specified for shear bolts.1,2,3,5
6. INFILLED WALLS
ALLOWABLE VALUES
per bolt.
Shear: Same as for
shear bolts.
Reinforced masonry infilled openings Same as values
in existing unreinforced masonry specified for
walls. Provide keys or, dowels to unreinforced
match reinforcing. masonry walls.
7. REINFORCED MASONRY
Masonry piers and walls reinforced Same as value speci-
per Chapter 24 of the Building fied in Section 2409
Code.6 of the Building Code.
8. REINFORCED CONCRETE
Concrete footings, walls and piers Same as values
reinforced as specified in Chapter specified in Chapter
26 of the Building Code and 26 of the Building
designed for tributary loads.b Code.
1 Bolts to be tested as specified in section A2307.
Z Bolts to be 1/2 -inch minimum in diameter.
3 Drilling for bolts and dowels shall be done with an electric
rotary drill. Impact tools shall not be used for drilling holes or
tightening anchors and shear bolt nuts.
4 A one -third increase in allowable stress is not allowed except
as noted.
5 Similar chemical set anchors may be used with prior approval of
the Building Official.
6 Stresses given may be increased for combinations of loads as
specified in the Building Code.
7 In addition to sheathing value.
Ordinance No. 1991 Series)
Page 28
540
--- -1 - - -� - -r - -; - -�;- ;----- ,--- r- -, - - -t
480
•-•
t ' 1 t I ' t ' t t' t 1
,
420
--- - -� - -L - s - -� -- ' - -' -- ' -- '--- 1 - -� - -=
360
Diaphragm
Span 300
,
—; -- 1 - -� -- -_ - 1--- �-- r----- i-- �-- -, - - -+
L (Feet)
240
1
- -r - -1 __`K -•J- _,___� -- 1- __L__r __J- _ -'___+
- - -L- -- r• -� - - - ' - - -1 -- ' -- L - -- i --
100
_ i_ ' _J _x.._ ' _ L- ' _.1
_, _�_
-, -�_
1- , +
720
1 1 ,• l ,/ 1 , 1 , t , 1
60
' ' ' 1 Y 1 O'
0
1 1 I 1 1
0
1 2 3 4 5 6
Demand- Capacity Ratio, DCR
PIGURE
NO. A23 -1. ACCEPTABLE DIAPHRAGM SPAN
/ $-3(o
Ordinance No. (1991 Series)
Page 29
SECTION 2. Chapter 15.04 of Title 15 of the San Luis Obispo
Municipal Code is hereby amended by adding Section 15.04.041 as
follows.
SECTION 15.04.041 AMENDMENTS; UNIFORM BUILDING CODE
STANDARDS
A. Amend the Uniform Building Code Standards by adding
Standards No. 24 -40, 24 -41, and 24 -42 to read as follows:
UNIFORM BUILDING CODE STANDARD NO. 24 -40
IN -PLACE MASONRY SHEAR TESTS
Scope
Section 24.4001. This standard covers procedures for conducting
in -place masonry shear tests.
Procedure
Section 24.4002. The bed joists of the outer wythe of the
masonry shall be tested in shear by laterally displacing a single
brick relative to the adjacent bricks in the same wythe.' The
head joint opposite the loaded end of the test brick shall be
carefully excavated and cleared. The brick adjacent to the
loaded end of the test brick shall be carefully removed by sawing
or drilling and excavating to provide space for a hydraulic ram
and steel loading blocks. Steel blocks, the size of the end of
the brick, shall be used on each end of the ram to distribute the
load to the brick. The blocks shall not contact the mortar
joints. The load shall be applied horizontally, in the plane of
the wythe, until either a crack can be seen or slip occurs. The
strength of the mortar shall be calculated by dividing the load
at the first crack or movement of the test brick by the nominal
gross area of the sum of the two bed joists.
UNIFORM BUILDING CODE STANDARD NO. 24 -41
TESTS OF ANCHORS.IN UNREINFORCED MASONRY WALLS
Scope
Section 24.4101. This standard covers procedures for conducting
tests of anchors installed in unreinforced masonry walls.
Existing Anchors
Section 24.4102. The test apparatus shall be supported on the
masonry wall at a minimum distance of the wall thickness from the
anchor tested. Existing wall anchors shall be given a preload of
300 pounds prior to establishing a datum for recording
elongation. The tension test load reported shall be recorded at
Ordinance No.
Page 30
1/8 -inch relative
surface. Results
shall include the
and joist orienta
1991 Series)
movement of the anchor and the adjacent masonry
of all tests shall be reported. The report
test results as related to the wall thickness
tion.
Combined Shear and Tension Bolts
Section 24.4103. Combined shear and tension bolts embedded in
unreinforced masonry walls shall be tested using a torque
calibrated wrench to the following minimum torques:
1/2- inch - diameter bolts -- 40 foot lbs.
5/8- inch - diameter bolts -- 50 foot lbs.
3 \4- inch - diameter bolts -- 60 foot lbs.
All nuts shall be installed over malleable iron or plate washers
when bearing on wood and heavy cut washers when bearing on steel.
UNIFORM BUILDING CODE STANDARD NO. 24 -42
POINTING OF UNREINFORCED MASONRY WALLS
Scope
Section 24.4201. This standard covers procedures for pointing of
unreinforced masonry walls.
Pointing
Section 24.4202. The old or deteriorated mortar should be cut
out, by means of a toothing chisel or nonimpact power tool, to a
uniform depth of 3/4 inch or until sound mortar is reached. Care
must be taken not to damage the brick edges. After cutting is
completed, remove all loose materials with a brush, air or water
stream.
Mortar mix shall be Type N or S proportions as called for in the
construction specifications, preferably as close to the original
mortar proportion as possible. Prehydrate pointing mortar to
reduce excessive shrinkage. To prehydration mortar, thoroughly
mix all ingredients dry, then mix again adding only enough water
to produce a damp unworkable mix which will retain its shape when
pressed into a ball. After keeping mortar in this dampened
condition for 1 to 1 -1/2 hours, add sufficient water to the
prehydrated mortar to bring it to a proper consistency that is
somewhat drier than conventional masonry mortar. To ensure good
bond, wet the mortar joints thoroughly before applying pointing
mortar. The joints should not be visibly wet with free - standing
water which must be absorbed into the wall. Pack mortar tightly
in thin layers (1/4 -inch maximum) until the joint is filled, then
0 -38
ft
Ordinance No. (1991 Series)
Page 31
tool to a smooth surface to match the original profile.
SECTION 3. If any provision of this Ordinance is for any
reason held to be invalid by a court of competent jurisdiction,
the City of San Luis Obispo hereby declares that it would have
passed each and every remaining provision irrespective of such
holding in order to accomplish the intent of this ordinance.
SECTION 4. A summary of this ordinance, approved by the City
Attorney, together with the ayes and noes shall be published at
least (5) days prior to its final passage in the Telegram Tribune,
a newspaper published and circulated in said City, and the same
shall go into effect at the expiration of thirty (30) days after
its said final passage. A copy of the full text of this ordinance
shall be on file in the Office of the City Clerk on and after the
date following introduction and passage to print and shall be
available to any interested member of the public.
SECTION 5. The City Clerk is hereby authorized and directed
to transmit a certified copy of this ordinance modifying the
Uniform Building Code and Uniform Building Code Standards to the
State of California Department of Housing and Community
Development.
INTRODUCED AND PASSED TO PRINT by the Council of the City of
San Luis Obispo at a meeting held on the day of
1992, on motion of , seconded by
, and on the following roll call vote:
AYES:
NOES:
ABSENT:
ATTEST:
CITY CLERK PAM VOGES
MAYOR RON DUNIN
Ordinance No. 1991 Series)
Page 32
APPROVED:
Ci Admi 'strative Officer
Director of Coi�mpnity Development
WW W
"Potentially Hazardous" Buildings
Located in the City of San Luis Obispo
Assumed to Have Tax Exempt Status
ADDRESS
2747 Broad
941 Chorro (Mission)
856 Higuera
2180 Johnson ( "Old Adobe ")
2180 Johnson (Hospital)
2180 Johnson ( "Sunny Acres ")
951 Marsh
696 Monterey (Museum)
747 Monterey (Murray Adobe) -
1039 Monterey
955 Morro
976 Osos (Courthouse)
682 Palm (Mission Prep)
751 Palm (Old Mission Office)
748 Pismo (Fire Station)
OWNER
Springfield Baptist Church
Catholic Church of SLO
Cal Poly - SLO
County of San Luis Obispo
County of San Luis Obispo
County of San Luis Obispo
First Presbyterian Church
City of San Luis Obispo
City of San Luis Obispo
County of San Luis Obispo
City of San Luis Obispo
County of San Luis Obispo
Catholic Church of SLO
Catholic Church of SLO
City of San Luis Obispo