HomeMy WebLinkAboutORD NO 3302ORDINANCE NO. 3302
AN ORDINANCE OF THE CITY OF BAKERSFIELD
ADDING CHAPTER 15.40 TO THE BAKERSFIELD
MUNICIPAL CODE RELATING TO UNREINFORCED
MASONRY BUILDINGS.
BE IT ORDAINED by the Council of the City of Bakersfield
as follows:
SECTION 1.
Chapter 15.40 is hereby added to the Bakersfield Municipal
Code to read as follows:
CHAPTER 15.40
EARTHQUAKE HAZARD REDUCTION IN EXISTING
UNREINFORCED MASONRY BEARING WALL BUILDINGS
Sections:
15.40.005
15.40.010
15.40.020
15.40.030
15.40.040
15.40.050
15.40.060
15.40.070
15.40.080
15.40.090
15.40.100
15.40.110
Purpose.
Scope.
Definitions and notations.
Materials of construction.
Quality control.
Allowable design values.
Analysis and design.
Detailed systems design requirements.
Tables.
Pointing.
Acceptable span for diaphrams (Pigure A-l).
Analysis of URM wall for in-plan shear force
(Figure A-2).
15.40.005 Purpose.
The purpose of this chapter is to promote public safety,
health and welfare by reducing the risk of death or injury that may
result from the effects of earthquakes on unreinforced masonry
buildings.
The provisions of this chapter establish minimum standards
for structural seismic resistance primarily to reduce the risk of
death or injury, but cannot prevent loss of life or injury or pre-
vent earthquake damage to an existing building even though it com-
plies with these standards.
ORIGINAL
15.40.010 Scope.
The provisions of these requirements shall apply to all
buildings constructed prior to 1946 and having unreinforced masonry
bearing walls as defined herein. It is recognized that strengthen-
ing was done to many unreinforced masonry buildings following thee
1952 Kern County earthquake. The engineer or architect retained by
the building owner and the city building official shall give full
consideration to any strengthening done when analyzing the existing
condition of the building as required by this chapter. Where
strengthening was done which may not fully comply with the provi-
sions of this chapter, approval may be granted by the building
official if the building's condition complies with the intent of
this chapter.
Nothing in this chapter shall prevent the building owner,
his architect or engineer from employing accepted alternative meth-
ods to prove the minimum seismic safety of a building. In the
event an alternative method is employed by the building owner, his
architect or engineer which is not accepted by the city building
official, the building owner shall have the right to appeal that
decision to the Board of Building Appeals.
This chapter provides for strengthening standards for unre-
inforced buildings as defined in this chapter. This chapter shall
not require existing electrical, plumbing, mechanical, fire safety
systems, parking, disabled access or other existing non-conforming
uses to be altered as a result of seismic strengthening unless they
constitute a hazard to life.
Exceptions: This chapter shall not apply to detached one
or two family dwellings and detached multi-unit dwellings contain--
ing less than five (5) dwelling units and used solely for residen--
tial purposes, nor shall it apply to single story warehouse
buildings used solely for storage purposes and occupied less than
three (3) hours per day.
15.40.020 Definitions and notations.
A. Definitions. For purposes of this chapter, the defini-
tions set forth herein shall have the following meanings:
1. "Collar joint" is the vertical joint between wythes
of the multi-wythe walls.
2. "Continuous inspection" means that an inspector
has observed the work to the extent that he certifies the work has
been done according to applicable plans and specifications without
reservation.
3. "Crosswall" is a wood-framed wall sheathed with any
of the materials described in Tables A1-D and A1-E. Other systems
such as ductile moment resisting frames may be used as crosswalls
provided that the yield deflection does not exceed one inch in each
story height. A crosswall is not a shear wall.
4. "Diaphragm edge" is the intersection of the hori-
zontal diaphragm and a shear wall.
5. "Moment-resisting frame" is a planar moment-
resisting frame complying with the requirements of Section 2625 for
reinforced concrete or Section 2722 (f) for structural steel of the
Building Code.
6. "Open front" is an exterior building wall plane
without a shear wall capable of resisting the required lateral
forces.
7. "Shear wall" is a wall utilized to resist the
required seismic forces parallel to the wall (not including
crosswalls). All reinforced or unreinforced masonry or concrete
walls shall be considered shear walls. Braced frames shall be con-
sidered as shear walls. Moment-resisting frames may be designed as
crosswalls or shear walls.
8. "Unreinforced masonry bearing wall" or "URM". A
masonry wall having all of the following characteristics:
a. Provides the vertical support for a floor or
roof.
b. The total superimposed load is over 100 pounds
per linear foot.
c. The masonry wall does not have vertical
reinforcement.
9. "Yield deflection" is the deflection at which yield
stress is first developed in a frame member.
B. Notations. The applicable Code and the following sym-
bols and notations apply to the provisions of this section.
A
= Area of unreinforced masonry pier in square inches.
Cd
= Numerical coefficient for the calculation of DCR.
Cp
Numerical coefficient as specified in Section
2312(g)2 and as set forth in Table No. 23-P of the
Building Code and Table No. A1-B. of these
requirements.
ORIGINAL
Fi,
D
DCR
Fn, Fx
Fp
H
h/t
L
LC
L1
P
V
VA
VC
Vca
VR
va
vc
In-plane dimension of pier in inches, or depth of
diaphragm in feet.
Demand-Capacity Ratio.
Lateral force applied to level i, n, or x,
respectively.
Lateral forces on a part of a structure in the
direction under consideration.
Least clear height of opening on either side of
pier, in inches.
Height/thickness ratio of URM wall. Height is
measured between wall anchorage levels.
Span from shear wall to open front or span of dia-
phragm between shear walls.
Length of crosswall in feet.
Effective span of an open front building =
2[(Ww/Wd)-L + L].
Axial dead load on pier in pounds.
The total lateral force or shear at the building or
shear wall base.
Va-A, the allowable shear in pounds in any URM pier,
based on the allowable in-plane shear value.
Total shear capacity of crosswalls in the direction
of analysis immediately below the diaphragm level
being investigated.
Total shear capacity of crosswalls in the direction
of analysis immediately above the diaphragm level
being investigated.
0.5 P (D/H), the restoring shear in pounds of any
URM pier, based on the cracked pier analysis.
Allowable shear stress in pounds per square inch
for unreinforced masonry.
Maximum shear strength in pounds per foot for a
crosswall sheathed with any of the materials given
in Tables No. A1-D or A1-E.
ORIGINAL
vu
W
Wd =
~ Wd =
Wp =
Ww =
Maximum shear strength in pounds per foot for a
diaphragm sheathed with any of the materials given
in Tables No. A1-D or A1-E.
The total dead load as defined in Section 2302 of
the Building Code, including the partition loading
specified in Section 2304(d) of the Building Code
where applicable.
Total of the dead load that is tributary to a
diaphragm level.
Total of the dead load that is tributary to all of
the diaphragms.
The weight of a portion of a structure or non-
structural component.
Total dead load of an unreinforced masonry shear
wall above the level under consideration or above
an open front of a building.
Seismic zone factor as defined in Chapter 23 of the
Building Code.
15.40.030 Materials of construction.
A. General. All materials permitted by the Building Code,
including their appropriate allowable stresses and those existing
configurations of materials specified herein, may be utilized to
meet the requirements of this chapter.
B. Existing unreinforced masonry walls. Unreinforced
masonry walls analyzed in accordance with this section may provide
vertical support for roof and floor construction and resistance to
lateral loads. The facing and backing shall be bonded so that not
less than 4 percent of the exposed face area is composed of solid
headers extending not less than 4 inches into the backing. The
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
ratio and the shear capacity of the wall.
C. Minimum acceptable quality of existing unreinforced
masonry walls.
1. General provisions. All unreinforced masonry wallis
utilized to carry vertical loads and seismic forces parallel and
perpendicular to the wall plane shall be tested as specified in
this subsection. All masonry quality shall equal or exceed the
minimum standards established herein or shall be removed and
replaced by new materials. The quality of mortar in all masonry
walls shall be determined by performing in-place shear tests. All
testing shall meet approved testing method parameters (including
rate of load application) and shall be performed in accordance with
the requirements specified in this subsection by a testing agency
approved by the building official. Alternative methods of testing
may be approved by the building official. Nothing shall prevent
pointing with mortar of all the masonry wall joints before the
tests are first made. Prior to any pointing, the mortar joints
must be raked and cleaned to remove loose and deteriorated mortar.
Mortar for pointing shall be Type S or N except masonry cements
shal~ not be used. All preparation and mortar pointing shall be
done under a permit and under the continuous inspection of a spe-
cial inspector. At the conclusion of the inspection, the inspector
shall submit a written report to the licensed engineer or architect
responsible for the seismic analysis of the building, setting forth
the result of the work inspected. The vertical wall joint between
wythes (collar joint) shall be inspected at the test location, and
an estimate of the percentage of wythe to wythe mortar coverage
shall be reported along with the results of the in-place shear
tests. 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. 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 official for
approval as part of the structural analysis.
2. Number and location of tests. The minimum number
of tests shall be as follows:
a. 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.
b. At each of all other stories, not less than one
per wall or line of wall elements providing a common line of resis-
tance to lateral forces.
c. In any case, not less than one per 1500 square
feet of wall surface and a total of eight.
The shear tests shall be taken at locations repre-
sentative 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 licensed engineer or architect responsible for
the seismic analysis of the subject building.
3. In-place shear tests. The bed joints of the outer
wythe of the masonry shall be tested in shear by laterally displac-
ing a single brick relative to the adjacent bricks in that wythe.
The mortar in the opposite head joint of the brick to be tested
shall be removed and the head joint shall be cleaned prior to
testing. The brick to be tested shall be a minimum of one course
away from a header course. The minimum quality mortar in 80 per-
cent of the shear tests shall not be less than the total of 30 psi
plus the axial stress in the wall at the point of the test. The
shear stress shall be based on the gross area of both bed joints
and shall be that at which first movement of the brick or flaking
of the mortar is observed. Walls with mortar values which are con-
sistently low and do not meet the minimum quality values specified
in this subsection shall be entirely repointed.
15.40.040 Quality control.
A. Inspections: Except as modified in this section,
inspections shall comply with Section 306 of the Building Code.
B. Special inspection: Inspection specified herein shall
be performed by a special inspector in accordance with Section 306
of the Building Code.
C. Continuous inspection for pointing: Continuous inspec-
tion shall be provided during all preparation and joint pointing.
Exception: At the discretion of the building official, incidental.
pointing may be performed without special inspection.
D. Testing of Shear Bolts. One-fourth of all new shear
bolts and dowels embedded in unreinforced masonry walls shall be
tested by a special inspector using a torque calibrated wrench to
the following minimum torques:
1/2-inch-diameter bolts or dowels--40 foot lbs.
5/8-inch-diameter bolts or dowels--50 foot lbs.
3/4-inch-diameter bolts or dowels--60 foot lbs.
ORIGINAL
Exception: Special inspection may be provided during
installation in lieu of testing.
E. Determination of allowable values for existing anchors.
Five percent of the existing rod anchors utilized as all or part of
the required wall anchors shall be tested in pullout by an approw~d
testing laboratory. The minimum number 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. The test
apparatus shall be supported on the masonry wall at a minimum dis-
tance of the wall thickness from the anchor tested. The rod anchor
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 1/8-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. The allowable resistance
value of the existing anchors shall be 40 percent of the average of
those anchors tested in the same wall thickness and with the same
joist orientation. The allowable resistance shall not exceed the
values given in Table A1-E for tension bolts.
F. Determination of allowable values for wall anchorage
devices. Qualification tests for devices used for wall anchorage
shall be performed with the entire tension load carried on the
enlarged head at the exterior face of the wall. Bona on the part
of the device between the enlarged head and the interior wall face
shall be eliminated for the qualification tests. The resistance
value assigned the device shall be twenty percent of the average of
the ultimate loads.
15.40.050 Allowable design values.
A. General. Stresses in materials and existing construc-
tion utilized to resist seismic forces shall conform to those spec-
ified in the Building Code and those materials and types of
construction specified in this section:
B. Determination of allowable shear stress in existing
unreinforced masonry:
1. Design shear values. Design seismic in-plane shear
stresses shall be substantiated by tests performed as specified in
Section 15.40.030(C). The allowable shear Va, shall be 10 percent.
of a test value that is determined by the in-plane shear tests.
The test value, in psi, is that value that is exceeded by 80 per-
cent of the test values. The tested shear values are calculated by
reducing the test results, in psi, by the axial stress, in psi, in
the masonry at the point of testing. The maximum value of va is 10
psi. The allowable shear stress, Va, may be increased by addition
of 15 percent of the axial stress due to the weight of the wall
directly above. (~
2. Design compression and tension values. Compression
stresses for unreinforced masonry having a minimum design shear
value of 3 psi shall not exceed 100 psi. Design tension values for
unreinforced masonry shall not be permitted.
C. Combination of vertical and seismic forces.
1. New materials. All new materials introduced into
the structure to meet the requirements of this chapter which are
subjected to combined vertical and horizontal forces shall comply
with Chapter 23 of the Building Code.
2. Existing materials. When stresses in existing
lateral force-resisting elements are due to a combination of dead
loads plus floor live loads plus seismic loads, the allowable work-
ing stress specified in the Building Code may be increased 100
percent. However, no increase will be permitted in the allowable
values given in Section 15.40.080, Tables No. A1-D (except as
noted in footnote 4) and A1-E, and the stresses in the members due
only to seismic and dead loads shall not exceed the values permit--
ted by Section 2303(d) of the Building Code.
15.40.060 Analysis and design.
A. General. Every structure within the scope of this
chapter shall be analyzed and constructed to resist stress produced
by lateral forces as provided in this section. Stresses shall be
calculated as the effect of a force applied horizontally at each
floor or roof level above the base. The force shall be assumed to
come from any horizontal direction. However, structural concepts
other than those set forth in this section may be approved by the
building official when evidence is submitted showing that equiva-
lent ductility, strength, and energy absorption are provided. The
structure shall be analyzed by the general procedures of the
Earthquake Regulations of the Building Code or, when applicable,
may be analyzed by Section 15.40.060(I).
B. Analysis and design. Every structure within the scope
of this chapter shall be analyzed and constructed to resist minimum
lateral seismic forces assumed to act nonconcurrently in the direc-
tion of each of the main axes of the structure in accordance with
the following equation:
V = ZW
3
.................................... (Ai-1)
The total base shear shall be distributed over the
height of the structure including level n according to the follow-
ing formula.
Fx --
Wxhx
n
~ wihi
i=l
V ............................. (A2-2)
At each level designated as x1 the force Fx shall be
distributed over the area of the building in accordance with the
mass distribution on that level.
C. Lateral forces on elements of structures.
1. General. Parts or portions of structures shall be
analyzed and designed for lateral loads in accordance with this
subsection. The lateral forces shall be determined by the follow-
ing formula.
Fp = ZICpWp ....................................... (A1-3)
Exception: Unreinforced masonry walls in buildings not
required to be designed as an essential facility may be analyzed
for out-of-plane stability in accordance with Section 15.40.060(I).
D. Regulated elements of buildings. The elements of
buildings required to be analyzed by this chapter shall be as spec-
ified in Section 15.40.080, Table No. A1-A.
E. Anchorage and interconnection. Anchorage and
interconnection of all parts, portions and elements of the struc-
ture shall be analyzed and designed for lateral forces in accor-
dance with the Building Code and subsection C. of this section.
F. Analysis procedure.
1. General. Stresses in materials and existing con-
struction utilized to transfer seismic forces from the ground to
parts or portions of the structure shall conform to those permitted
by the Building Code and those materials and types of construction
specified in Section 15.40.080, Tables No. A1-D and A1-E.
2. Connections. Materials and connectors used for
interconnection of parts and portions of the structure shall
conform to the Building Code.
Anchorage of masonry walls to each floor or roof
shall resist a minimum force determined by Formula A1-3 or 200
pounds per linear foot, whichever is greater, acting normal to the
wall at the level of the floor or roof. Existing anchors,
installed under previous permits, must meet or must be upgraded to
meet the requirements of this chapter. Substantial changes in wall
thickness shall be restrained by anchorage and bracing to the floor
or roof diaphragm in accordance with Section 15.40.060(C).
G. Unreinforced masonry walls, in-plane shear.
1. General. Except as modified herein, unreinforced
masonry walls shall be analyzed as specified in Chapter 24 to with-
stand all vertical loads as specified in Chapter 23 of the Building
Code in addition to the seismic forces required by this chapter.
The 50 percent increase in the seismic force factor for shear walls
as specified in Section 2407(h)4.F. of the Building Code may be
omitted in the computation of seismic loads to existing shear
walls.
2. Allowable shear value. The allowable shear shall
be as specified in Section 15.40.050(B).
3. Allowable reduction of bending stress by vertical
load. In calculating tensile fiber stress due to seismic forces
required by this section, the maximum tensile fiber stress may be
reduced by the full direct stress due to vertical dead loads.
Exception: In lieu of calculating flexural fiber
stress in unreinforced masonry piers, the in-plane flexural
capacity of the pier may be taken as:
VR = 0.5 P (D/H) ....................................... (A1-4]~
4. In-plane loads. Shear strength of a URM pier shall
be calculated utilizing Section 15.40.110, Figure No. A-2 and the
following equations:
(i)
VA = Va'A ..................................... (A1-5]~
(ii)
VR = 0.5P-D/H ................................. (A1-6]~
When the shear strength of an unreinforced masonry
pier, analyzed in accordance with Figure A-2 requires
strengthening, said pier shall be strengthened in accordance with
this chapter.
5. Shear resisting elements constructed of new
materials. Moment resisting frames, braced frames, and reinforced{
masonry or concrete shear walls shall comply with all requirements
of the Building Code. The relative rigidity of the added shear
walls and the existing shear walls shall be considered.
H. Unreinforced masonry walls, out-of-plane forces.
Flexural stresses due to seismic forces normal to the wall need not
be analyzed if the wall does not exceed the height-to-thickness
ratio as set forth in Section 15.40.080, Table No. Ai-C for "all
other buildings".
If the wall height-thickness ratio exceeds the speci-
fied limits, the wall may be supported by vertical bracing members
designed in accordance with Chapter 23 of the Building Code. The
deflection of such bracing members at design loads shall not exceed
one-tenth of the wall thickness.
Exception: The wall may be supported by flexible
vertical bracing members designed for two-thirds of the forces
specified by Chapter 23 of the Building Code if their deflection at
design loads is not less than one-quarter nor more than one-third
of the wall thickness.
All 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 mem-
bers shall not exceed one-half the unsupported height of the wall
nor 10 feet.
The wall height may be measured vertically to bracing
elements other than a floor or roof. Spacing of the bracing ele-
ments and wall anchors shall not exceed 6 feet. Bracing elements
shall be detailed to minimize the horizontal displacement of the
wall by components of vertical displacements of the floor or roof..
I. Analysis procedure: Buildings with wood diaphragms:
1. General. Except as modified herein, the analysis
shall be in accordance with Chapter 23 of the Building Code and
Section 15.40.060(B) through (H). Buildings that have horizontal
diaphragms of wood construction conforming to the criteria of this
section may be analyzed by this section. The in-plane seismic
force in each shear wall shall be calculated in accordance with
Section 15.40.0604(I) in lieu of calculation and distribution of a
base shear as prescribed in the Building Code. For determination
of the capacity of anchorages of masonry walls out-of-plane, the
value of ZICp = 0.3 shall be used.
a. Criteria: The diaphragm sheathing shall be
boards, finish flooring, plywood or similar wood material, single
or in combination, nailed to joists or rafters. Nailing of exist--
ing wood sheathing need not be verified. Nailing of supplemental
sheathing or plywood shall be equal to that specified in the
Building Code for the specified shear values.
2. Modification of Base Shear: Buildings with hori-
zontal wood diaphragms and complying with the following limitations
shall be analyzed to resist minimum lateral forces in accordance
with the following formula:
V = ZW
4
.................................... (A1-7)
a. Limitations: The building shall have crosswalls
in each level on each axis of the building.
All crosswalls need not be continuous below a
wood diaphragm at/or near grade provided:
(1) Shear connections and anchorage require-
ments of Section 15.40.060(E) are satisfied at all edges of the
diaphragm.
(2) Crosswalls with total capacity of~.07 Wd
interconnect the diaphragm to the foundation.
(3) The demand/capacity ratio of the diaphragm
between the crosswalls that are continuous to their foundations
shall be calculated as [0.33Wd + Vca] /2VuD and shall not exceed
2.5.
b. Spacing of crosswalls shall not exceed 40'-0"
O.C. in the direction of consideration.
c. Crosswalls shall have a minimum strength of 30
percent of the diaphragm strength in the direction of
consideration. If several crosswalls exist at a spacing of less
than 40 feet O.C., the total capacity of the crosswalls in any 40
feet measured along the span of the diaphragm shall exceed 30 per--
cent of the diaphragm strength.
3. Distribution of lateral forces.
1. The total lateral force shall be distributed over
the height of the structure in accordance with Formulas A1-8 and
A1-9.
V =~Fi ................................................... (A1-8)
i=l
A portion of the total base shear V shall be
distributed over the height of the structure including level
according to the following formula:
n
Fx = Z
3
__Wx .............................................. (A1-9)
Exception: Building with crosswalls conforming to Section
15.40.060(I)(2)(C) shall use the following formula:
Z Wx ................................................ (Al-10)
4
4. Unreinforced masonry walls..
a. In-plane shear. The provisions of Section
15.40.060(G) are applicable except the ~eismic force distributed to
the shear wall at any diaphragm level shall be the lesser value
calculated as:
(i) For buildings without crosswalls:
Z Wd/2 .............................................. (Al-ll)
3
(ii) For buildings with crosswalls in all levels:
Z vu · D -~Wd/[ (2Vu'D) + Vc] ...................... (Al-12)
4
where:
Vc = the capacity of the crosswalls in the story below the
level of consideration.
(iii) Vu.D.
b. The strength of a shear wall at any level need
not exceed the value of Z/K Ww plus the sum of the diaphragms'
shear strength.
where: K = divisor of Z in equations (Ai-1 and (A1-7).
5. Unreinforced masonry walls - out-of-plane forces.
a. The provision of Section 15.40.060(H) are
applicable except that the allowable h/t ratio for buildings com-
plying with the limitations for crosswalls may be used.
6. Existing roof, floors and walls.
a. Existing materials, including wood framed dia--
phragms utilized in a described configuration, may be used as part
of the lateral load-resisting system, provided that the
demand/capacity ratio of these materials does not exceed the values
shown in Section 15.40.100, Figure No. A-1. Wood diaphragms at or
near grade shall comply with the requirements of Section
15.40.060(I). Values of diaphragm capacity, Vu, and crosswall
capacity, Vc, for existing materials are given in Section
15.40.080, Table A1-D.
b. Strengthening of existing materials. New
materials, including wood shear walls, may be utilized to
strengthen portions of the existing seismic resisting system in a
described configuration, provided that the stresses do not exceed
the values shown in Section 15.40.080, Table No. A1-E.
c. Alternate materials. Alternate materials, designs
and methods of construction may be approved by the Building Official.
d. Diaphragm displacement control. The displace-
ment of a diaphragm relative to the shear walls is acceptable if
the values of DCR and span in feet lies within the boundaries of
the curve shown in Section 15.40.100, Figure A-1.
e. Use of wood diaphragms to control displacement
of an open front. Wood framed crosswalls and diaphragms con-
structed of materials described in Section 15.40.080, Tables A1-D
and A1-E shall be analyzed by the following procedures:
Calculate L1, diaphragm span in feet, for use in Section 15.40.100,
Figure No. A-1 as:
L1 = Effective span = 2 [(Ww/Wd) · L + L] .............. (Al-13
Ww = Total dead load of URM wall above the open front.
L = Span from shear wall to open front or span of diaphragm
beyond crosswall.
Calculate demand/capacity ratio as:
0.33 (Wd + Ww)/(vu · D) ................................. (Al-14
If crosswalls are used to limit displacement at open front, calcu--
late demand/capacity ratio as:
0.33 (Wd + Ww) / [(vu D) + Vc] ...................... (Al-15
A supplemental support system in conformance to Section
15.40.070(C) shall be provided at lintels bearing on unreinforced
masonry piers at the open front.
Horizontal diaphragms shall not be considered to trans-
mit lateral forces by rotation. A minimum of one (1) shear wall
and one (1) crosswall shall be parallel to each axis of the building.
7. Shear connection of wood diaphragms. For determi-
nation of the capacity of the shear connections at the edges of
wood diaphragms, the values of ZIC~ as set forth in Section
15.40.080, Table A1-B shall be use~. However, the strength of the
shear connections need not exceed the strength of the diaphragm as
given in Section 15.40.080, Table A1-D and A1-E.
15.40.070 Detailed systems design requirements.
A. General. In addition to the seismic analysis required
elsewhere in this chapter, the licensed engineer or architect
responsible for the seismic analysis of the building shall deter-
mine and record the information required by this section on the
approved plans.
B. Wall anchorage.
1. Locations. All unreinforced masonry walls shall be
anchored at the roof, floor and ceiling levels by tension bolts
through the wall as specified in Section 15.40.080, Table No. A1-E,
or by approved equivalent at a maximum anchor spacing of 6 feet.
All existing rod 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 rod anchors. Tests when required shall conform to Section
15.40.040(E).
Exception: Walls need not be anchored to ceiling
systems, if due to their low mass and/or relative location with
respect to the floor or roof systems, the ceiling does not impose
significant normal forces on the wall.
At the roof and all floor levels, the anchors near-
est the building corners shall be combination shear and tension
anchors located not more than two feet horizontally from the inside
of the corners of the walls.
2. Access for anchorage. When access to the exterior
face of the masonry wall is prevented by proximity of an existing
building, wall anchors conforming to Item 5a and b in Section
15.40.080, Table No. A1-E may be used.
Alternative devices to
bolts for masonry wall anchorage shall
Section 15.40.040(F).
be used in lieu of tension
be tested as specified in
C. Truss and beam supports. Where trusses and beams other
than rafters or joists are supported on masonry, independent secon-
dary columns shall be installed to support vertical loads of the
roof or floor members.
D. Parapets. Parapets and exterior wall appendages not
capable of resisting the forces specified in this section shall be
removed, stabilized or braced to insure 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 No. 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 ten-
sion roof anchors.
The minimum height of a parapet above the wall anchor
shall be twelve (12) inches.
Exception:
at the top of the wall,
may be six (6) inches.
If a reinforced concrete beam is provided
the minimum height above the wall anchor
All deteriorated mortar joints in unreinforced masonry
walls shall be pointed in accordance with Section 15.40.090.
E. Existing damage. Repair details of any cracked or dam-
aged unreinforced masonry wall required to resist forces specified
in this chapter shall be provided in the approved construction
documents. Repair details to restore the original strength of
other structural elements shall also be provided.
F. Veneer. Veneer shall be anchored with approved anchor
ties, conforming to the required design horizontal force specified
in tlhe Building Code and placed at a maximum spacing of 24 inches
with a maximum supported area of four (4) square feet.
Exception: Existing veneer anchor ties may be accepted
by the building official 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 corru-
gated 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.
The existence and condition of existing veneer anchor
ties shall be verified as follows:
1. An approved testing laboratory shall verify the
location and spacing of the ties and shall submit a report to the
building as a part of the structural analysis.
2. 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.
15.40.080 Tables.
BUILDING ELEMENTS
REQUIRING ANALYSIS
1.
2.
3.
4.
5.
TABLE NO. A1-A
REGULATED ELEMENTS
Walls, h/t ratio
Walls, In-plane Shear
Wall Anchorage
Parapets
Floors and Roofs:
Connections at edge
Diaphragm Displacement Control
TABLE NO. A1-B
VALUES OF ZICp
CONFIGURATION OF MATERIALS
Roofs with straight or diagonal
sheathing and roofing applied directly
to tlhe sheathing, or floors with straight
tongue and grove sheathing.
Double or multiple layers of boards
with edges offset and blocked
plywood systems.
0.2
0.3
TABLE NO. A1-C
ALLOWABLE VALUE OF HEIGHT-THICKNESS RATIO OF UNREINFORCED
MASONRY WALLS WITH MINIMUM QUALITY MORTAR1
ALL OTHER
BUILDINGS
BUILDINGS WITH
CROSSWALLS
Walls of one-story
Buildings
13 162
First-story wall
of multi-story
buildings
15 16
Walls in top story
of multi-story
buildings
9 142
All other walls 13 16
1Minimum quality mortar shall be determined by laboratory testing
in accordance with Section 15.40.030(c).
2Values shown are for mortar shear test values of 60 psi or greater
and with filled collar joints. Filled collar joints are defined as
over 50 percent mortar coverage of the area exposed in the in-place
shear tests.
TABLE NO A1-D
VALUES FOR EXISTING MATERIALS
EXISTING MATERIALS
OR CONFIGURATIONS
OF MATERIALS1
ALLOWABLE VALUES
1. HORIZONTAL DIAPHRAGMS
a. Roofs with straight
:sheathing and roofing
,applied directly to the
sheathing. 4
190 lbs. per foot
for seismic shear
ORIGINAL
ee
Roofs with diagonal
sheathing and roofing
applied directly to the
sheathing. 4
Floors with straight
tongue-and-groove sheathing.
Floors with straight
sheathing and finished wood
flooring with board edges
offset or perpendicular.
Floors with diagonal
sheathing and finished wood
flooring.
250 lbs. per foot
for seismic shear
100 lbs. per foot
for seismic shear
500 lbs. per foot
for seismic shear
600 lbs. per foot
for seismic shear
CROSSWALLS2
a. Plaster on wood or metal
lath.
b. Plaster on gypsum lath.
c. Gypsum wall board, un-
blocked edges.
d. Gypsum wall board,
blocked edges.
Per side: 200 ~Lbs.
per foot for
seismic shear
175 lbs. per foot
for seismic shear
75 lbs. per foot
for seismic shear
125 lbs. per foot
for seismic shear
EXISTING FOOTINGS, WOOD FRAMING,
STRUCTURAL STEEL, AND REINFORCED STEEL
a. Plain concrete footings.
b. Douglas fir wood.
c. Reinforcing steel.
d. Structural steel.
f'c = 1500 psi
unless otherwise
shown by tests.
Allowable stress
same as
No. 1 D.F.3
ft = 18,000 lbs.~
per square inch
maximum.3
ft = 20,000 lbs..
per square inch
maximum.3
Material must be sound and in good condition.
Shear values of these materials may be combined, except the
total combined value shall not exceed 300 lbs. per foot.
Stresses given may be increased for combinations of loads as
specified in Section 15.40.050(C).
Shear values may be increased to 150 lbs. per linear foot for
items (a) and (c), and to 300 lbs. per linear foot for item
(b). Such increase shall be substantiated by the engineer and
approved by the building official.
TABLE NO. A1-E
ALLOWABLE VALUES OF NEW MATERIALS USED
IN CONJUNCTION WITH EXISTING CONSTRUCTION
NEW MATERIALS OR CONFIGURATION
OF MATERIALS1
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
Plywood sheathing applied
directly over existing wood
studs. No value shall be
given to plywood applied over
existing plaster or wood
sheathing.
Drywall or plaster applied
directly over existing wood
studs.
Drywall or plaster applied to
plywood sheathing over existing
woods studs.
ALLOWABLE VALUES
225 lbs. per foot
1.33 times the
values specified
in Table No. 25-K-1
of the Building Code
for shear walls.
100 percent of the
values specified
Table No. 47-I of
the Building Code.
50 percent of the
values specified in
Table No. 47-I of
the Building Code..
3. SHEAR BOLTS
Shear bolts embedded a
minimum of 8 inches into
unreinforced masonry walls.
Bolt centered in a 2-1/2-inch
diameter hole with dry-pack or
non-shrink grout around circum-
ference of bolt. 1 3
4. 'PENSION BOLTS
Tension bolts and tension dowels
extending entirely through unrein-
forced masonry walls secured with
bearing plates on far side of a
3 wythe minimum wall with at least
30 square inches of area. 2 3
Bolts extending to 1 inch from
the exterior face of the wall with
a 2 1/2-inch round plate under the
head. Install as specified for shear
bolts. Spaced not closer than 12
inches on centers.I 2 3
Bolts extending to 1 inch from
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 horizontal.
Installed as specified for shear
bolts. 1 2 3
5. INFILLED WALLS
Reinforced masonry infilled
openings in existing unrein-
forced masonry walls. Provide
keys or dowels to match rein-
forcing.
6. REINFORCED MASONRY
Masonry piers and walls rein-
forced per Section 2407(h) 4.
133 percent of the
values specified for
solid masonry in
Table No. 24-J of the
Building Code. No
values larger than
those given for 3/4
inch bolts shall be
used.
1800 lbs. per bolt,
tension. 900 lbs.
for 2 wythe walls.
600 lbs. per bolt,
tension for 3 wythe
walls.
1200 lbs. per bolts,
tension for 3 wythe
walls.
Same as values
specified for
unreinforced masonry
walls.
Same as values spec-
ified in Section 2406
of the Building Code.
7. REINFORCED CONCRETE
Concrete footings, walls and
piers reinforced as specified in
Chapter 26 of the Building Code
and designed for tributary loads.
8. EXISTING FOUNDATION LOADS
Foundation loads for structures
exhibiting no evidence of
~settlement.
Same as values spec-
ified in Chapter 26
of the Building Code.
Calculated existinq
foundation load may
be increased 25 per-
cent for dead loads,
and may be increased
50 percent for dead
load plus seismic
load required by this
chapter.
1Bolts to be tested as specified in Section 15.40.040(D).
2Bolts to be 1/2-inch minimum in diameter.
3Drilling 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.
15.40.090 Pointing and relaying of brick.
A. Pointing. The Uniform Building Code Standard No. 24-42
for the Pointing of unreinforced masonry walls is adopted.
1. 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.
2. Mortar mix shall be Type "S" 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:
a. 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.
- 23 ~
ORIGINAL
b. The joints to be tuck-pointed should be
dampened, but to ensure a good bond, the brickwork must absorb al~L
surface water. Water should be added to the pre-hydrated mortar to
bring it to a workable consistency (somewhat drier than conven-
tional mortar). The mortar should be packed tightly into the
joints in thin layers (1/4" 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."
B. 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 mor-
tar 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 sur-
face moisture to ensure a good bond. The appropriate surfaces of
the surrounding brickwork and the replacement brick should be but-
tered 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 wil~L
help to ensure full head and bed joints. When the mortar becomes
"thumbprint hard," the joints shall be tooled to match the original
profile.
ORIGINAL
15.40.100 Acceptable Span for Diaphrams (Figure A-i).
540 ....
48O
360 ......
300
240 '
!B0 ........
120 _ _ _
60___
0
0
DEMAND-CAPACITY RATIO
FIGURE A-1 ACCEPTABLE SPAN FOR DIAPHRAGMS
ORIGINAL
15.40.110 Analysis of URM wall for in-plane shear force
(Figure A-2).
COMPARE
VR AND VA
IN EACH PIER
RESTORING SHEAR IS ADEQUATE;
ROCKING OF PIER SYSFFEM IS
SAFE
Vt > ~' VR ( STRENGTHEN WALL)
IS IN PROPORTION TO
PD/H; ~IV~UAL P~S RESTORING SHEAR OF PIER
CAN ROCK SAFELY SYSTEM IF NOT ADEQUATE
VR > VA RELATIVE
RIGIDITY
IN AT LEAST ANALYSIS
ONE PIER
VR -- Restoring sheor of a pier
~VR -- Rest~ring sheor of eli piers in the w~li
VA -- Shear strength OF a pier
Vt - Total sheor force applied t~ the wall
Vx -- Shear fome assigned ~ o pier
on the baeie OF a relative sheor
rigidity anolyeie
Vx > Va
IN ANY
PIER
tVR<Vx I
1N AT LEASTI
ONE PIER
I
DISTRIBUTION OF
SHEAR FORCES IN
PIERS CANNOT
BE DETERMINED
OMIT FROM
ANALYSIS
ANY PIER
W/VR < Vx
VR > Vx
IN ALL
PIERS
SHEAR FORCE IN AN
INDIVIDUAL PIER IS
PROPORTIONAL TO D?H
SHEAR 5"]'R_FSS If OK
STRENGTHEN WAll)~
SHEAR FORCE IN AN INDIVIDUAL
PER tS PROPORTIONAL TO D/H.
PER IS OVERSTRESSED IN SHEAR
FIGURE A-2 - ANALYSIS OF URM WALL FOR IN-PLANE SHEAR FORCE
- 26 -
109005
SECTION 2.
This ordinance shall be posted in accordance with the
City Charter provisions and shall become effective thirty (30)
days from and after the date of its passage.
.......... o0o ..........
I HEREBY CERTIFY that the foregoing Ordinance was passed
and adopted by the Council of the City of Bakersfield at a regular
meeting thereof held on JUL 2 5 1990 , by the
following vote:
AYES; COUNCILMEMBERS: EDWARDS, DeMaND, SMITH, RRUNNI, PETERSON, MCDERMo'Tr, SALVABGIO
NOES; COUNCILMEMBERS:
ABSENT COUNCILMEMBERS: ,/V ~' ~ ,~
ABSTAIN: COUNCILMEMRER$'
ASSISTANT CITY CLERK and Ex Officio Clerk of the
Council of the City of Bakersfield
APPROVED JUL 2 5 1990
MAYOR of the City of Bakersfield
APPROVED as to form:
ARTI{UR J. SAALFIELD
CITY ATTORNEY of the City of Bakersfield
LCM/meg
O ORD 5
URM.1-27
7/2/90
- 27
ORI(}INAL
AFFIDAVIT OF POSTING DOCUMENTS
STATE OF CALIFORNIA)
)
County of Kern)
CAROL WILLIAMS,
That she is the
of Bakersfield;
Being duly sworn, deposes and says:
duly appointed, acting and qualified City Clerk of
and that on the 30th day of July
posted on the Bulletin Board at City Hall, a
the following: Ord±nance No.
City Council at a meeting held on the 25th
and entitled:
the City
1990 she
full, true and correct copy of
passed by the Bakersfield
day of July , 1990
NSAOPD
/s/ CAROL WILLIAMS
CITY CLERK of the City of Bakersfield
DEPUTY City Clerk