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ORDINANCE NO. 1924
AN ORDINANCE OF THE CITY OF ARCADIA, CALIFORNIA
AMENDING CHAPTER 9 OF THE BUILDING CODE SETTING FORTH
REGULATIONS FOR THE REDUCTION OF EARTHQUAKE HAZARDS
IN EXISTING BUILDINGS
WHEREAS, Text Amendment 90-005 was initiated by the City for the consideration
of amending the Building Code Chapter 9 setting forth regulations for the reduction of
earthquake hazards in existing buildings to be consistent with the revised 1990 Model
Ordinance recommended by the State of California Seismic Safety Commission for the
Seismic Retrofit of Hazardous Unreinforced Masonry buildings.
WHEREAS, the City Council conducted a public hearing concerning the text
amendment on July 3, 1990, and approved the amendment.
WHEREAS, the City Council recognizes the danger posed by potentially hazardous
buildings in California and determines that it is appropriate to revise Chapter 9 of the
Arcadia Municipal Code "Earthquake Hazard Reduction in Existing Buildings" to be
consistent with the State's 1990 Model Ordinance which replaces the previously adopted
URM building regulations. Said changes will promote public safety and welfare by
reducing the risk of death or injury that may result from the effects of earthquakes on
unreinforced masonry bearing wall buildings constructed prior to October 16, 1938.
NOW, THEREFORE, THE CITY COUNCIL OF THE CITY OF ARCADIA DOES
HEREBY ORDAIN AS FOLLOWS:
Section 1. That Chapter 9 "Earthquake Hazard Reduction in Existing Buildings"
shall be revised as set forth in attached Exhibit A.
Section 2. The City Clerk shall certify to the adoption of this Ordinance and shall
cause a copy of the same to be published in the official newspaper of said City within
fifteen (IS) days after its adoption.
Passed, approved and adopted this 7th day of August 1990.
ATTEST~'
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'7?7CUtr4'K~7
Mayor of City of cadia
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f Arcadia
-1-
1924
STATE OF CALIFORNIA
COUNTY OF LOS ANGELES SS:
CITY OF ARCADIA
I, JUNE D. ALFORD, City Clerk of the city of Arcadia, hereby
certify that the foregoing Ordinance No. 1924 was passed and
adopted by the City Council of the city of Arcadia, signed by the
Mayor and attested to by the City Clerk at a regular meeting of
said Council held on the 7th day of August, 1990 and that said
Ordinance was adopted by the following vote, to wit:
AYES: Councilmembers Ciraulo, Fasching, Gilb, Harbicht and Young
NOES: None
ABSENT: None
J
adia
city
k of the
-2-
1924
ARTICLE VIII
BUILDING REGULATIONS
CHAPTER 9
EARTHQUAKE HAZARD REDUCTION IN
EXISTING BUILDINGS
Note: Code reference - 1988 Uniform Building Code (UBC)
Parenthetical section numbers are to the 1990 Revised Model
Ordinance for the Seismic Retrofit of Hazardous Unreinforced
Masonry Buildings, from the State of California Seismic Safety
Commission.
8901. GENERAL (A2341)
(a) Purpose. 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 unreinforced masonry bearing wall buildings.
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.
(b) Scope. The provisions of this Chapter shall apply to all existing buildings
having at least one unreinforced masonry bearing wall. Except as provided
herein, all other provisions of the Building Code shall apply.
EXCEPTIONS: This Chapter shall not apply to:
1. Detached one or two family dwellings and detached apartment houses
containing less than 5 dwelling units and used solely for residential purposes.
2. Essential Facilities as defined in Table 23-K of the Building Code.
3. Hazardous Facilities as defined in Table 23-K of the Building Code.
This chapter does not require alteration of existing electrical, plumbing,
mechanical or fire safety systems.
(c) Definitions. For purposes of this Chapter, the applicable definitions in the.
Uniform Building Code (UBC) shall also apply.
COLLAR JOINT is the vertical space between adjacent wythes and may
contain mortar.
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CROSSW ALL is a wall that meets the requirements of Section A8906 (d) 3. A
crosswall is not a shear wall.
CROSSW ALL SHEAR CAPACITY is the length of the crosswall times the
allowable shear value, vcLo.
DIAPHRAGM EDGE is the intersection of the horizontal diaphragm and a
shear wall.
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 wall plane without vertical elements in one or
more stories which resist the required lateral forces.
POINTING is the partial reconstruction of the bed joints of a URM wall as
defined in UBC Standard No. 24-42.
UNREINFORCED MASONRY (URM) WALL is a masonry wall in which the
area or reinforcing steel is less than 25 percent of that required by the Building
Code for reinforced masonry.
UNREINFORCED MASONRY BEARING WALL is a URM wall which
provides the vertical support for a floor or roof for which the total
superimposed load is over 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.
(d) Symbols and Notations. For the purposes of this Chapter, the applicable
symbols and definitions in the Building Code shall also apply.
A = Area of unreinforced masonry pier, square inches.
Ab = Area of the bed joints above and below the test specimen for
each in-place shear test.
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Cp = Numerical coefficient as specified in Section 2312 (g) and given
in Table 23-P of the Building Code and Table 89-A of this
Chapter.
0 = In-plane width dimension of pier, inches, or depth of
diaphragm, feet.
OCR = Demand-capacity ratio specified in Section 8906 (d).
Fwx = Force applied to a wall at level x, pounds.
H = Least clear height of opening on either side of pier, inches.
hit = Height/thickness ratio of URM wall. Height h is measured
between wall anchorage levels.
L = Span of diaphragm between shear walls, or span between shear
wall and open front, feet.
La = Length of crosswall, feet.
Lj = Effective span for an open front building specified in 8906 (d) 8,
feet.
Po = Superimposed dead load at the top of the pier under
consideration, pounds.
PD+L = Actual dead plus live load in place at the time of testing, pounds.
Pw = Weight of wall, pounds.
Va = vaA, 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,
LvcLo, pounds.
Vca = Total shear capacity of cross walls in the direction of analysis
immediately above the diaphragm level being investigated,
LvcLo, pounds.
Vr = 0.5PD(D/H), the rocking shear of any URM wall or wall pier,
pounds.
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Vwx = 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.
Vtest = Load in pounds at incipient cracking for each in-place shear test
per UBC Standard No. 23-40.
Va = Allowable shear stress for unreinforced masonry, psi.
Vc = Allowable shear value for a crosswall sheathed with any of the
materials given in Tables 89-C or 89-0, pounds per foot.
Vt = Mortar shear strength as specified in Section 2343 (c) 3E.
Vto = Mortar shear test values as specified in Section 2343 (c) 3E.
Vu = Allowable shear value for a diaphragm sheathed with any of the
materials given in Tables 89-C or 89-0, pounds per foot.
~vuD = Sum of diaphragm shear capacities of both ends of the
diaphragm.
l~vuD = For diaphragms coupled with crosswalls ~~vuD 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.
~Wd = Total dead load tributary to all of the diaphragms at and above
the level under consideration, 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.
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8902. GENERAL REQUIREMENTS (A2342)
(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) Alteration 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.
(c) Requirements for Plans. The following construction information shall be
included in the plans required by this Chapter:
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 fully dimensioned or drawn to scale on the plans.
2. Accurately dimensioned wall elevations showing openings, piers,
wall classes as defined in section 8903 (c) 3E, thickness, 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 this Chapter.
7. All other plans, sections, and details necessary to delineate required
retrofit construction including those items in Section 8907.
8903. MATERIAL REQUIREMENTS (A2343)
(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.
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(b) Existing Materials. All existing materials utilized as part of the required
force resisting system shall be in sound condition or shall be 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 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 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. The veneer wythe shall not be included
in the effective thickness used in calculating the height to thickness and the
shear capacity of the wall.
3. Mortar. A. Tests. The quality of mortar in all masonry walls shall
be determined by performing in-place shear tests in accordance with UBC
Standard No. 24-40. Alternative methods of testing may be approved by the
Building Official.
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 surfaces due to. deterioration caused by leaks and
condensation of 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 per class shall be
as follows:
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(i) 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.
(ii) At each end of all other stories, not less than one per wall or line of
wall elements providing a common line of resistance to lateral forces.
(iii) In any case, not less than one per 1,500 square feet of wall surface
nor less than a total of eight.
D. Minimum Quality Mortar. (i) Mortar shear test values, Vto, in psi
shall be obtained for each in-place shear test in accordance with the following
equation:
Vto = (Vtest - Po+O/ Ab..................................................................(43-1)
(ii) Individual unreinf.orced masonry walls with Vto consistently less
than 30 psi shall be entirely pointed prior to retesting.
(iii) The mortar shear strength, Vt, is the value in psi that is exceeded
by 80% of all of the mortar shear test values, Vto.
(iv) Unreinforced masonry 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. Unreinforced Masonry Classes. All existing unreinforced masonry
shall be categorized into one or more classes based on shear strength, quality
of construction, state of repair, deterioration, and weathering. See Section
8905 (b).
G. Pointing. All deteriorated mortar joints in unreinforced masonry
walls shall be pointed according to UBC Standard No. 24-42. Nothing shall
prevent pointing with mortar of all the masonry wall joints before the tests
are made.
8904. QUALITY CONTROL (A2344) .
(a) Pointing. All preparation and mortar pointing shall be done with special
inspection.
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Exception: At the discretion of the Building Official, incidental
pointing may be performed without special inspection.
(b) Masonry Shear Tests. In-place masonry shear tests shall comply with UBC
Standard No. 24-40.
(c) Existing Wall Anchors. Existing wall anchors utilized as all or part of the
required tension anchors shall be tested in pullout according to UBC 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.
(d) New Bolts. One-fourth of all new shear bolts and combined tension and
shear bolts in unreinforced masonry walls shall be tested according to UBC
Standard No. 24-41.
Exception: Special inspection may be provided during installation in
lieu of testing.
8905. ALLOW ABLE DESIGN VALUES (A2345)
(a) Allowable Values. 1. Allowable values for existing materials are given in
Table 89-C and for new materials in Table 89-0. The one-third increase in
allowable values is not allowed for values in these tables.
2. Allowable values not specified in this Chapter shall be as specified
elsewhere in the Building Code. Allowable values not specified in this
Chapter for dead load plus seismic load may be increased 33 percent.
Allowable values not specified in this Chapter for existing building elements
with a combination of dead load plus floor live load plus seismic load may be
increased 70 percent.
(b) Masonry Shear. The allowable unreinforced masonry shear stress, Va,
shall be determined for each masonry class from the following equation:
va = O.lvt + 0.15PD/ A................................................................... (45-1)
The mortar shear test value, Vt, shall be determined in accordance with
Section 8903, and not exceed 100 psi for the determination of Va.
The one-third increase in allowable values of the Building Code is not
allowed for Va.
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(c) Masonry Compression. Where any increase in dead plus live
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) Masonry Shear Modulus. The shear modulus (Ev) for unreinforced
masonry, for relative rigidity analysis when masonry is used to resist lateral
forces in combination with other materials, may be assumed as 10,000vt,
unless substantiated by tests.
(f) 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.
(g) Foundations. For existing foundations new total loads may be increased
over existing loads by 25% for dead load only and increased 50% for dead load
plus seismic load. Higher values may be justified only in conjunction with a
geotechnical investigation.
8906. ANALYSIS AND DESIGN (A2346)
(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 8906 (c) which is based on Chapter 23 of the Building
Code or, when applicable, buildings may be analyzed by the Special Procedure
of 8906 (d).
(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:
v = 0.33ZW........................................................................................(46-1)
2. Lateral Forces on Elements of Structures. Parts or portions of
structures shall be analyzed as required in Chapter 23 of the Building Code.
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Exceptions: i. Unreinforced masonry walls for which height to
thickness ratios do not exceed ratios set forth in Table 89-B need
not be analyzed for out-of-plane loading. Unreinforced masonry
walls which exceed the allowable hit ratios of Table 89-B shall be
braced according to Section 8907 (e).
ii. Parapets complying with Section 8907 (f) need not be analyzed
for out-of-plane loading.
3. Shear Walls (In-Plane Loading). Shear walls shall comply with
subsection 8906 (e).
(d) Special Procedure. 1. Limits for the Application of Subsection 8906 (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 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
or steel braced frames or special moment resisting frames (see
Section 2312 of the Building Code) each with a maximum
overall height-to-length ratio of 1-1/2 to 1.
D. The lateral force resisting system shall be regular as defined
in the Building Code. Except for a single story building with an
open front, a minimum of two lines of vertical lateral force-
resisting elements shall be parallel to each axis of the building.
2. Lateral Forces on Elements of Structures. With the exception of the
diaphragm provisions in subsection 8906 (d), elements of structures shall
comply with subsection 8906 (c) 2.
3. Crosswalls. Crosswalls shall meet the requirements of this
subsection.
A. Crosswall Definition. A crosswall is a wood-framed wall sheathed
with any of the materials described in Tables 89-C or 89-0. 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.
Cross walls shall extend the full story height between diaphragms.
Exception: 1. Crosswal1s need not be provided at all levels in
accordance with subsection 8906 (d) 4B (iv).
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2. Existing cross walls need not be continuous below a
wood diaphragm at/or within four feet of grade provided:
(i) Shear connections and anchorage requirements
Section 8906 (d) 7 are satisfied at all edges of the
diaphragm.
(H) Crosswalls with a total shear capacity of .07IWd
interconnect the diaphragm to the foundation.
(Hi) The demand/ capacity ratio of the diaphragm between
the crosswalls that are continuous to their foundations
shall be calculated as:
OCR = [0.33Wd+Vca]/2vuD...................................(46-2)
and OCR shall not exceed 2.5.
B. Crosswall Shear Capacity. Within any 40 feet measured along the
span of the diaphragm, the sum of the crosswaU shear capacities shall be at
least 30 percent of the diaphragm shear capacity of the strongest diaphragm at
or above the level under consideration.
C. Existing Crosswalls. Existing cross walls 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 cross wall 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 stories.
E. Other Cross wall Systems. Otfrer systems such as special moment
resisting frames may be used as cross walls provided that the yield story drift
does not exceed one inch in any story. .
4. Wood Diaphragms. A. Acceptable Diaphragm Span. A diaphragm
is acceptable if the point (L,DCR) on Figure 89-1, 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:
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(i) For a diaphragm without qualifying cross walls at levels
immediately above or below:
OCR = 0.83ZWd/LVuD...........................................(46-3)
(ii) For a diaphragm in a single-story building with qualifying
cross walls:
OCR = 0.83ZWd/(LVuD + Vcb)............................ (46-4)
(Hi) For diaphragms in a multi-story building with qualifying
cross walls in all levels:
OCR = 0.83ZLWd/(LLVuD + Vcb)...................... (46-5)
DCR shall be calculated at each level for the set of diaphragms at and above
the level under consideration.
(iv) For a roof diaphragm and the diaphragm directly below if
coupled by crosswalls:
OCR = 0.83ZLW d/LLVuD.....................................(46-6)
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 shear 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 be investigated and shall be developed into the diaphragm by new or
existing materials.
(ii) In addition to calculating demand capacity ratios per Section
8906 (d) 4B, the demand capacity ration 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 vud for the demand capacity ratio calculation shall be based
on the net depth of the diaphragm.
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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 = 1/2 ZCpWd............................................................... (46-7) or
V = vuD..................................................................................(46-8)
6. Shear Walls (In Plane 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 cross walls,
Fwx = 0.33Z(Wwx+Wd/2)..................................................(46-9)
but need not exceed
Fwx = 0.33ZWwx + vuD...................................................(46-10)
(ii) For buildings with cross walls in all levels:
Fwx = 0.25Z(Wwx+Wd/2)................................................(46-11)
but need not exceed
Fwx = 0.25Z(Wwx+LWd(vuD/LLvuD))..................... (46-12)
and need not exceed
Fwx = 0.25ZWwx+vuD..................................................... (46-13)
B. Wall Story Shear. The wall story shear shall be the sum of the wall
story forces at and above the level of consideration.
Vwx = LF'wx........................................................................(46-14)
C. Shear Wall Analysis. Shear walls shall comply with subsection
A2346 (e).
D. Moment Frames. Moment frames used in place of shear walls shall
be designed as required in Chapter 23 of the Building Code except that the
forces shall be as specified in Section 8906 (d) 6A and the inters tory drift ratio
shall be limited to 0.005.
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7. Out of Plane Forces - URM Walls. A. Allowable URM Wall Height
to Thickness Ratios. The provisions of Section 8906 (c) 2 are applicable except
the allowable hit ratios given in Table 89-B shall be determined from Figure
89-1 as follows:
(i) In Region 1, h/ t ratios for "buildings with cross walls" m<:iY be
used if qualifying cross walls are present in all stories.
(ii) In Region 2, hit ratios for "buildings with crosswalls" may be
used whether or not qualifying crosswalls are present.
(iii) In Region 3, h/ t ratios for "all other building" shall be used
whether or not qualifying cross walls are present.
B. Walls with Diaphragms in Different Regions. When diaphragms
above and below the wall under consideration have DCRs in different regions
of Figure 89-1, the lesser hit ratio shall be used.
8. Buildings with Open Fronts. A building with an open front 0 one
side shall have crosswalls parallel to the open front and shall be designed by
the following procedure:
A. Effective Diaphragm Span, Li for use in Figure No. 89-1 shall be
determined in accordance with the following formula:
Li = 2 [(Ww/Wd) . L + L]..................................................(46-15)
B. Diaphragm Demand/capacity ratio shall be calculated as:
OCR = 0.83Z (Wd+Ww)/[(vuD)+ Vel............................ (46-16)
(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 rigidity may be
neglected in determining the rigidity of an URM wall.
B. Shear Walls with Openings. Wall piers shall be analyzed according
to the following procedure:
(i) For any pier,
(I) The pier shear capacity shall be calculated as:
Va = vaDt..................................................... (46-17)
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(2) The pier rocking shear capacity shall be calculated as:
Vr = 0.5PoD/H............................................(46-18)
(ii) The wall piers at any level are acceptable if they comply with
one of the following modes of behavior:
(1) Rocking Mode. Where all piers at a level have shear
capacities capable of sustaining rocking, i.e., the pier shear
capacity is greater than or equal to the pier rocking shear
capacity for each pier, forces in the wall at that level,Vwx,
shall be distributed to each pier Vp, in proportion to
PoD/H.
For each pier at that level: Va 2: Vr....................(46-19}
and for the wall at that level: Vwx ~ 2;Vr....... (46-20)
(2) Non-rocking Mode. Where at least one pier at a level
is incapable of sustaining a rocking mode, i.e., the pier
shear capacity is less than the pier rocking shear capacity,
forces in the wall at that level, Vwx, shall be distributed to
each pier, Vp, in proportion to D/H, such that
Vwx = 2;Vp.
For at least one pier at that level: Va < Vr...... (46-21)
For each pier at that level: Vp ~ Va.................. (46-22)
and Vp ~ Vr............................................................(46-23)
If Vp > Vr in one or more piers, omit such piers from the
analysis and repeat the procedure for the remaining piers
or strengthen and reanalyze the wall.
(Hi) 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 Vr shall be calculated
as follows:
Vr = (O.50Po + 0.25Pw)D/H..............................................(46-24)
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2. Plywood Sheathed Shear Walls. Plywood sheathed shear walls may
be used to resist lateral loads for buildings with flexible diaphragms analyzed
according to provisions of Section 8906 (c). Plywood sheathed shear walls
may not be used to share lateral loads with other material along the same line
of resis tance.
3. Combinations 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 moment frames shall
comply with Section 8906 (e) 3B.
4. Moment Resisting Frames. A moment frame shall not be used with
a URM wall in a single line of resistance unless the wall has piers that are
capable of sustaining rocking in accordance with 8906 (e) IB and the frames
are designed to carry 100% of the lateral forces.
8907. DETAILED SYSTEM DESIGN REQUIREMENTS (A2347)
(a) General.
(b) Wall Anchorage. 1. Anchor locations. All unreinforced masonry walls
shall be anchored at the roof and floor levels as required in Section 8906 (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. 89-0, 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. The Building Official may require
testing to verify the adequacy of the embedded ends of existing wall anchors.
3. Minimum Wall Anchorage. Anchorage of masonry walls to each
floor or roof shall resist a minimum.force determined by Section 2312 (g) 2 of
the Building Code or 200 pounds per linear foot, whichever is greater, acting
normal to the wall at the level of the floor or roof. Existing wall anchors,
installed under previous permits, must meet or be upgraded to meet the
requirements of this Chapter.
4. Anchors at Corners. At the roof and all floor levels, both shear and
tension anchors shall be provided within two feet horizontally from the
inside of the corners of the walls.
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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 89-0 may be used.
(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.
(e) Wall Bracing. 1. General. Where a wall height-thickness ratio exceeds
the specified limits, the wall may be laterally supported by vertical bracing
members per Section 8907 (e) 2 or by reducing the wall height by bracing per
Section 8907 (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
twelve (12) inches.
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EXCEPTION: If a reinforced concrete beam is provided at the top of the
wall, the minimum height above the wall anchor may be six (6) inches.
(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 or two (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 one inch in width, eight inches in length and one-
sixteenth of an inch in thickness (1" X 8" X 1/16") 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 nine (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 the roof or floor members. The loads
shall be transmitted down to adequate support.
(i) Adjacent Buildings. 1. Where elements of adjacent buildings, do not
have a separation of 5 inches, the allowable height/thickness ratios for
"buildings with crosswalls" per Table 89-B shall not be used in the direction of
consideration.
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I
.J
2. Where buildings do not have a separation of at least 5 inches and
the diaphragm levels of the adjoining structures differ by more than one and
one-half times the wall thickness, supplemental vertical gravity load carrying
members shall be added to support the loads normally carried by the wall and
such members shall not be attached to the wall. The loads shall be
transmitted down to the foundation.
8908. ADMINISTRATIVE PROVISIONS (A2348)
(a) Definitions. For the purposes of this Chapter, the applicable definitions in
the Building Code shall also apply.
HIGH RISK BUILDING is any building, other than an essential building or
hazardous building, having an occupant load of 100 occupants or more, as
determined by Section 3302 (a) of the Uniform Building Code.
Exception: A high risk building shall not include the following:
1. Any building having exterior walls braced with masonry crosswalls
or wood frame crosswalls spaced less than 40 feet apart in each story.
Cross walls shall be full-story height with a minimum length of 1-1/2
times the story height.
2. Any building used for its intended purpose, as determined by the
building official, for less than 20 hours per week.
LOW RISK BUILDING is any building; other than an essential building or
hazardous building, having an occupant load as determined by Section 3302
(a) of the Uniform Building Code of less than 20 occupants.
MEDIUM RISK BUILDING is any building, not classified as a high-risk
building or an essential building or hazardous building, having an occupant
loads as determined by Section 3302 (a) of the Uniform Building Code of 20
occupants or more.
(b) Rating Classifications. The rating classifications identified in Table 89-E
are hereby established and each building within the scope of this Chapter
shall also be placed in one such rating classification by the Building Official.
The total occupant load of the entire building as determined by Section 3302
(a) of the Building Code shall be used to determine the rating classification.
Exception: For purposes of this Chapter, portions of buildings
constructed to act independently when resisting seismic forces may be
placed in a separate rating classifications.
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(c) Compliance Requirements. 1. The owner of each building within the
scope of this Chapter shall, upon service of an order and within the time
limits set forth in this Chapter, cause a structural analysis to be made of the
building by an engineer or architect licensed by the state to practice as such
and, if the building does not comply with earthquake standards specified in
this Chapter, the owner shall cause it to be structurally altered to conform to
such standards or shall cause the building to be demolished.
2. The owner of a building within the scope of this Chapter shall
comply with the requirements set forth above by submitting to the Building
Official for review within the stated time limits:
A. Within 270 days after the service of the order, a structural analysis,
which is subject to the approval by the Building Official, and which shall
demonstrate that the building meets the minimum requirements of this
Chapter; or
B. Within 270 days after the service of the order, the structural analysis
and plans for the structural alterations of the building to comply with this
Chapter; or
C. Within 120 days after service of the order, plans for the installation
of wall anchors in accordance with the requirements specified in Section 8907;
or
D. Within 270 days after the service of the order, plans for the
demolition of the building.
3. After plans are submitted and approved by the Building Official, the
owner shall obtain a building permit, and then commence and complete the
required construction or demolition within the time limits set forth in Table
No. 89-F. These time limits shall begin to run from the date the order is
served in accordance with Section 8908 (d) 2, except that the time limit to
commence structural alteration or demolition shall begin to run from the
date the building permit is issued.
4. Owners electing to comply with Item 2C of this subsection are also
required to comply with Items 2B or 20 of this subsection provided, however,
that the 27D-day period provided for in Item 2B or 20 and the time limits for
obtaining a building permit and to complete structural alterations or building
demolition set forth in Table No. A-23-F. shall be extended in accordance with
Table No. 89-G. Each such extended time limit shall begin to run from the
date the order is served in accordance with Section 8908 (d), except that the
time limit to commence structural alterations or demolition shall begin to
run from the date the building permit is issued.
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(d) Administration. 1. Order - Service. A. The Building Official shall, in
accordance with the priorities set forth in Table No. 89-G, issue an order as
provided in this section to the owner of each building within the scope of
this Chapter.
B. Prior to the service of an order as set forth in Table No. 89-G, a
bulletin may be issued to the owner as shown upon the last equalized
assessment roll or to the person in apparent charge or control of a building
considered by the Building Official to be within the scope of this Chapter. The
bulletin may contain information the Building Official deems appropriate.
The bulletin may be issued by mail or in person.
2. Order - Priority of Service. Priorities for the service of the order for
buildings with the scope of this Chapter shall be in accordance with the rating
classification as shown on Table No. 89-G. Within each separate rating
classification, the priority of the order shall normally be based upon the
occupant load of the building. The owners of the building housing the largest
occupant loads shall be served first. The minimum time period prior to the
service of the order as shown on Table No. 89-G shall be measured from the
effective date of this Chapter. The Building Official may, upon receipt of a
written request from the owner, order such such owner to bring his building
into compliance with this Chapter prior to the normal service date for such
building set forth in this Chapter.
3. Order - Contents. The order 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, and upon the person, if any, in apparent charge or
control of the building. The order shall specify that the building has been
determined by the Building Official to be within the scope of this chapter and,
therefore, is required to meet the minimum seismic standards of this
Chapter. The order shall specify the rating classification of the building and
shall be accompanied by a copy of Section 8908 (c) which sets forth the owner's
alternatives and time limits for compliance.
4. Appeal From Order. 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 City Council. Such appeal shall be filed with the City Clerk
within 60 days from the service date of the order described in Section 8908 (d)
3 of this Chapter. Any such appeal shall be decided by the Council no later
than 90 days after the date that the appeal is filed. Such appeal shall be made
in writing upon appropriate forms provided therefore, and the grounds
thereof shall be stated clearly and concisely. Each appeal shall be accompanied'
by a filing fee as set forth by resolution of the City Council. Appeals or
requests for modifications from any other determinations, orders or actions
by the Building Official pursuant to this Chapter, shall be made in accordance
with the normal appeal procedures established in the Building Code.
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5. Recordation. At the time that the Building Official serves the
aforementioned order, the Building Official shall file with the office of the
county recorder a certificate stating that the subject building is within the
scope of this Chapter and is a potential earthquake hazardous building. The
certificate shall also state that the owner thereof has been ordered to
structurally analyze the building and to structurally alter or demolish it
where compliance with this Chapter has not been demonstrated.
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 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.
6. Enforcement. If the owner or other person in charge or control of the
subject building fails to comply with any order issued by the Building Official
pursuant to this Chapter within any of the time limits set forth in Section
8908 (c), 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 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 by such additional time as
may have been granted by the City Council, the Building Official may order its
demolition of the building in accordance with the Abatement of Dangerous
Buildings provisions of the Building Code.
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TABLE NO. 89-A
HORIZONTALFORCEFACTORCp
CONFIGURATION OF MATERIALS
Cp
Roofs with straight or diagonal sheathing and
roofing applied directly to the sheathing, or
floors with straight tongue and groove sheathing.
0.5
Diaphragms with double or multiple layers of
boards with edges offset and blocked plywood
systems.
0.75
TABLE NO. 89-B
ALLOWABLE VALUE OF HEIGHT-THICKNESS RATIO
OF UNREINFORCED MASONRY WALLS
Wall Types
BUILDING WITH CROSSWALLS1
ALL OTHER
BUILDINGS
Walls of
One-Story Buildings
162,3
13
First-Story Wall of
Multi-Story Buildings
16
15
Walls in Top Story of
Multi-Story Buildings
142,3
9
All Other Walls
16
13
1
Applies to the Special Procedures of Section 8906 (d) only. See Section 8906 (d) 7 for other
restrictions.
2
This value of height-to-thickness ratio may be used only where mortar shear tests in
accordance with Section 8903 establish a tested mortar shear strength, Vt, of not less than
100 psi or where the tested mortar shear strength, Vt, is not less than 60 psi and a visual
examination of the collar joint indicates not less than 50% mortar coverage.
3
Where a visual examination of the collar joint indicates not less than 50% mortar coverage
and the tested mortar shear strength, Vt, when established in accordance with Sections
8903 is greater than 30 psi but less than 60 psi, the allowable height-to-thickness ratio
may be determined by linear interpolation between the larger and smaller ratios in direct
proportion to the tested mortar shear strength, Vt.
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TABLE NO. 89-C
ALLOWABLE VALUES FOR EXISTING MATERIALS
EXISTING MA TERlALS OR
CONHGURATION OF MATERIALS!
1. HORIZONTAL DIAPHRAGMS4
ALLOWABLE VALUES
a. Roofs with straight sheathing
and roofing applied directly to
the sheathing.
100 lbs. per foot for seismic
shear.
b. Roofs with diagonal sheathing
and roofing applied directly to
the sheathing.
250 Ibs. per foot for seismic
shear.
c. Floors with straight tongue-and-
groove sheathing.
100 lbs. per foot for seismic
shear.
d. Floors with straight sheathing
and finished wood flooring with
board edges offset or perpendicular.
500 lbs. per foot for seismic
shear.
e. Floors with diagonal sheathing
and finished wood flooring.
600 lbs. per foot for seismic
shear.
2. CROSSW ALLS2,4
a. Plaster on wood or metal lath
b. Plaster on gypsum lath
c. Gypsum wall board, unblocked
edges
d. Gypsum wall board, blocked
edges
3. EXISTING FOOTINGS, WOOD
FRAMING, STRUCTURAL STEEL,
AND REINFORCES STEEL
a. Plain concrete footings
b. Douglas fir wood
Per side: 200 lbs. per foot for
seismic shear.
175 Ibs. per foot for seismic shear
75 lbs. per foot for seismic shear
125 lbs. per foot for seismic shear
f c = 1500 psi unless otherwise
shown by tests.
Allowable stress same as No.1
D.F.3
c.
Reinforcing steel
f t = 18,000 Ibs. per square inch
maximum. 3
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d. Structural Steel
f t = 20,000 lbs. per square inch
maximum.3
1
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 Ibs. per foot.
3
Stresses given may be increased for combinations of loads as specified in Section 8905.
4
A one-third increase in allowable stress is not allowed.
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TABLE NO. 89-04
ALLOW ABLE VALUES OF NEW MATERIALS USED
IN CONJUNCTION WITH EXISTING CONSTRUCTION (I)
NEW MATERIALS OR
CONFlGURA nON OF MATERIALS
1. HORIZONTAL DIAPHRAGMS
Plywood sheathing applied directly over
existing straight sheathing with ends of
plywood sheets bearing on joists or rafters
and edges of plywood located on center of
individual sheathing boards.
2. CROSSWALLS
a. Plywood sheathing applied directly over
wood studs. No value shall be given to
plywood applied over existing plaster or
wood sheathing.
b. Dry wall or plaster applied directly over
wood studs.
c. Dry wall or plaster applied to
sheathing over existing wood studs.
3. TENSION BOLTS
Bolts extending entirely through unreinforced
masonry walls secured with bearing plates
on far side of a 3 wythe minimum wall at least
30 square inches of area.2;3
4. SHEAR BOLTS
Bolts embedded a minimum of 8 inches into
unreinforced masonry walls. Bolts shall be
centered in a 2 1/2 inch-diameter hole with'
dry-pack or non-shrink grout around
circumference of bo11.1;3
5. COMBINED TENSION AND SHEAR BOLTS
a. wough Bolts - Combined Shear and Tension
Bolts meeting the above requirements
tension bolts and shear bolts1,2;3
26
ALLOW ABLE V ALUES4
225 Ibs. per foot
1.33 times the value specified in
Table No. 25-K-1 of the Uniform
Building Code for shear walls.
100 percent of the values in
Table No. 47-1 of the Uniform
Building Code.
50 percent of the values
specified in Table No. 47-1 of the
Uniform Building Code.
1800 Ibs. per bolt.
900 Ibs. for 2 wythe walls
133 percent of the values for plain
masonry specified in Table No.
24-E of the Uniform Building
Code. No values larger than
those given for 3/4 inch bolts
shall be used.
Tension: Same as for tension
bolts. Shear: Same as for shear
bolts.
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b. Embedded Bolts - Combined Shear and Tension
Bolts extending to the exterior face of the wall
with a 2-1/2 inch round plate under the head
and drilled at an angle of 22-1/2 degrees to
the horiwntal. Installed as specified for
shear bolts. 1,2,3
6. INFILLED WALLS
Reinforced masonry infilled openings in
existing umeinforced masonry walls.
Provide keys or dowels to match reinforcing.
7. REINFORCED MASONRY
Masonry piers and walls reinforced per
Chapter 24 of the Uniform Building Code.
8. REINFORCED CONCRETE
Concrete footings, walls and piers reinforced
as specified in Chapter 26 of the Uniform
Building Code and designed for tributary
loads.
1
Bolts to be tested as specified in Section 8904.
2
Bolts to be 1/2 inch minimum in diameter.
3
Tension: Same as for tension
bolts. Shear: Same as for shear
bolts.
Same as values specified for
umeinforced masonry walls.
Same values as specified in
Section 2409.
Same values as specified in
Chapter 26 of the Uniform
Building Code.
Drilling for bolts and dowels shall be done with an electric rotary drill. Impact tools
shall not be used for drilling holes and tightening anchors and shear bolt nuts.
4
A one-third increase in allowable stress is not allowed.
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TABLE NO. 89-E
RATING CLASSIFICATIONS
TYPE OF BUILDING
CLASSIFICATION
Essential Building
Hazardous Building
High-Risk Building
Medium-Risk Building
Low-Risk Building
I
I
II
III
IV
TABLE NO. 89-F
TIME LIMITS FOR COMPLIANCE
REQUIRED AaION OBTAIN BUILDING COMMENCE CONST COMPLETE CONST.
BY OWNER PERMIT WITHIN WITHIN WITHIN
Structural
Alterations or
Building Demolition
1 year
180 days 1
3 years
Wall Anchor
180 days
270 days2
1 year
1 Measured from the date of the service of order.
2 Measured from date of building permit issuance.
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TABLE NO. 89-G
EXTENSIONS OF TIME AND SERVICE PRIORITIES
Rating Occupant Extension of Time Periods for
Classification Load if Wall Anchors Service of Order
are InslalIed
I N/A N/A N/A
(Highest Priority)
II 100 or more 1 year 180 days
III-A 100 or more 1 year 1 year
II1-B More than 50 but 1 year 2 years
Less than 100
III-C More than 19 but 1 year 3 years
Less than 51
IV Less than 20 1 year 4 years
(Lowest Priority)
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UNIFORM BUILDING CODE STANDARD NO. 24-40
IN-PLACE MASONRY SHEAR TESTS
See Appendix Chapter 1, Uniform Code for Building Conservation
The bed joints of the outer wythe of the masonry shall be tested in shear by laterally by
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 horiwntally, 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 joints.
UNIFORM BUILDING CODE STANDARD NO. 24-41
TESTS OF ANCHORS IN UNREINFORCED MASONRY WALL
See Appendix Chapter 1, Uniform Code for Building Conservation
Existing Anchors
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 ad l/8-inch relative movement of the anchor and the adjacent masonry surface.
Results of all tests shall be reported. The report shall include the test results as related to the
wall thickness and joist orientation.
Combined Shear and Tension Bolts
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 Ibs.
5/8-inch-diameter bolts - - 50 foot Ibs.
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.
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UNIFORM BUILDING CODE STANDARD NO. 24-42
POINTING OF UNREINFORCED MASONRY WALLS
See Appendix Chapter 1, Uniform Code for Building Conservation
POINTING
The old mortar should be cut out, by means of a toothing chisel or a special painter's grinder, to
a uniform depth of 3/4", or until sound mortar is reached. Care must be taken not to damage the
brick edges. All dust and debris must be removed from the joint by brushing, blowing air or
rinsing with water.
Mortar mix shall be Type "5" or "N" proportions as called for in the construction specifications.
The tuck-pointing mortar should be pre-hydrated to reduce excessive shrinkage. The proper
pre-hydration process is as follows:
All dry ingredients should be thoroughly mixed. Only enough clean water should be added to
the dry mix to produce a damp, workable consistency which will retain its shape when formed
into a ball. The mortar should stand in this dampened condition for one to one and one-half
hours.
The joints to be tuck-pointed should be dampened, but to ensure a good bond, the brickwork must
absorb all surface water. Water should be added to the pre-hydrated mortar to bring it to a
workable consistency (somewhat drier than conventional mortar). The mortar should be packed
tightly into the joints in thin layers 0/4" maximum). Each layer should become "thumbprint
hard" before applying the next layer. The joints should be tooled to match the original profile
after the last layer of mortar is "thumbprint hard."
RELAYING OF BRICK
Replacement bricks must match the originals with respect to size, color, and texture where
exposed. A tuck-pointing toothing chisel should be used to cut out the mortar which surrounds
the affected units. Power driven impact tools are not allowed. Once the units are removed, all
of the old mortar shall be carefully chiseled out and all dust and debris shall be swept out with
a brush.
If used brick is to be relayed, it shall be cleaned of all old mortar. The brick surfaces in the
wall shall be dampened before new units are placed, but the masonry should absorb all surface
moisture to ensure a good bond. The appropriate surfaces of the surrounding brickwork and the
replacement brick should be buttered with mortar. The replacement brick should be centered in
the opening and pressed into position. The excess mortar should be removed with a trowel.
Pointing around the replacement brick will help io ensure full head and bed joints. When the
mortar becomes "Thumbprint hard," the joints shall be tooled to match the original profile.
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C
Cp
hn
S
v
w
Wp =
z
o
f'c
Fp
ft
I
=
=
=
GLOSSARY OF SYMBOLS AND NOTATIONS
=
Numerical coefficient as specified in Section 2312 (d) of the
Uniform Building Code.
=
Numerical coefficient as specified in Section 2312 (g) of the
Uniform Building Code.
=
The dimension of the structure, in feet, in a direction parallel to
the applied forces.
=
Specified compressive strength of concrete, psi
=
Lateral forces on a part of the structure and in the direction
under consideration
=
Allowable tensile stress, psi
=
Height in feet above the base to level n
=
Occupancy Importance Factor as set forth in Table No. 23-K of
the Uniform Building Code
=
Numerical coefficient for site-structure resonance
The total lateral force or shear at the base
The total dead load as defined in Section 2302 of the Uniform
Building Code including the partition loading specified in
Section 2304 (d) of the Uniform Building Code where applicable
The weight of a portion of a structure or nonstructural
component
Numerical coefficient dependent upon the zone as determined
by Figure No.1, of Chapter 23 of the Uniform Building Code.
All areas in California are classified in Zones 3 or 4. For
locations in Zone No.3, Z = 3/4. For locations in Zone No.4,
Z=1
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