HomeMy WebLinkAboutORD NO 3552Ordinance No. 3 5 $ 2
AN ORDINANCE AMENDING CHAPTER 15.40 OF 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 of the Bakersfield Municipal Code is hereby
amended to read as follows:
Chapter 15.40
EARTHQUAKE HAZARD REDUCTION IN EXISTING
UNREINFORCED MASONRY HEARING WALL BUILDINGS
Sections:
15.40.010
15.40.020
15.40.030
15.40.040
15.40.050
15.40.060
15.40.070
15.40.080
Purpose.
Scope.
Definitions.
Material requirements.
Quality control.
Allowable design values.
Detailed systems design requirements.
Tables and standards.
15.40.010 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 prevent earthquake damage to an existing building even though it
complies with these standards.
ORI(~INAL
15.40.020 Scope.
The provisions of these requirements shall apply to all
buildings having unreinforced masonry bearing walls as defined
herein. It is recognized that strengthening was done to many
unreinforced masonry buildings following the 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 provisions of this
Chapter, approval may be granted by the City 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
methods 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.
15.40.030 Definitions.
For the purpose of this Chapter, certain terms are
defined as follows:
(a) "CROSS WALLS:" are interior walls of masonry or wood
stud construction. In order to be considered as a cross wall
within the intent of this Chapter, cross walls shall be not more
than 40 feet apart in each story, and shall be full story height
between diaphragms. Existing cross walls shall be a minimum length
of one and one-half times the story height. Existing wood frame
cross walls shall be sheathed with one of the following: wood lath
and plaster, 1/2 inch thick gypsum wallboard two sides, or solid
one inch nominal thickness straight or diagonal wood board
sheathing. New cross walls shall have a rational shear path to the
ground, and shall be constructed of materials that are assigned
allowable shear values in Chapter 25 or Chapter 47 of the Uniform
Building Code, and shall have a total shear capacity equivalent to
that of a wall 1 1/2 times the story height that is sheathed with
a material that has an allowable shear value of 150 pounds per
foot.
(b) "UNREINFORCED MASONRY BEARING WALL:" A masonry wall
having all of the following characteristics:
1. Provide the vertical support for a floor or roof.
o
The total superimposed load is over 100 pounds per linear
foot.
ORIGINAL
The area of reinforcing steel is less than 25 percent of
the minimum steel ratios required by the Building Code
for reinforced masonry.
(c) "ARCHITECT OR ENGINEER:" California licensed
Architect or California licensed Civil or Structural Engineer in
responsible charge of the structural design work for the project.
15.40.040 Material requirements.
(a) Existing Materials. All existing materials utilized as
part of the lateral force resisting system shall be in sound
condition or shall be removed and replaced with new materials.
(b) Existing Unreinforced Masonry:
1. General. Unreinforced masonry walls shall be tested
as specified in this subsection. Masonry that does not meet or
exceed the minimum standards established by this Chapter shall be
removed and replaced by new materials and anchored to supporting
elements; design of anchorage shall comply with requirements for
anchorage of masonry veneer of Section 15.40.070(g).
2. Lay-Up of Walls. The facing and backing shall be
bonded so that not less than 4 percent of the wall surface of each
face 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 either vertically or
horizontally. In walls in which a single header does not extend
through the wall, headers from opposite sides shall overlap at
least four inches, or headers from opposite sides shall be covered
with another header course overlapping the header below at least
four inches. 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 of the wall unless it is bonded and anchored to the backing
in a manner acceptable to the City Building Official.
3. Mortar A. Tests. The quality of mortar in
unreinforced masonry walls shall be determined by performing in-
place shear tests in accordance with Uniform Building Code Standard
(24-7). Alternate methods of testing to establish compliance with
the minimum requirement of Section 15.40.040 (b) 3. D. (IV) may be
approved by the City Building Official.
B. Location of Tests. Shear tests shall be taken at
locations representative of the mortar conditions throughout the
entire building. The exact test location shall be determined at
the building site by the Architect or Engineer. An accurate record
of such tests and their location in the building shall be recorded
and these results shall be submitted to the City Building Official
for approval as part of the structural analysis.
3
C. Number of Tests. The minimum number of tests per
wall or line of wall elements providing a common line of resistance
to lateral forces shall be as follows: Two (2) tests per wall with
a minimum total number of 8 tests or one test per 1,500 square feet
of wall area, whichever results in the greater number of tests.
D. Minimum Quality Mortar. (I) Mortar shear test
values, Vto. shall be obtained for each in-place shear test in
accordance with the following equation:
Vto = (Vte~t
WHERE:
Vto
PD,L) /~ .................. (7--1)
Mortar shear test value, in
psi.
Shear stress at incipient
cracking for each in-place test
per Standard No. 24.7.
Actual dead plus live load in
place at the time of testing,
in pounds.
Area of the wall supporting PD+L
at each in-place shear test.
(II) Individual unreinforced masonry wall with vto less
than 30 psi shall be pointed prior to retesting.
(III) The mortar shear strength, vt is the value in psi
representing a minimum of 80% of all of the mortar shear test
values, Vto.
(IV) Unreinforced masonry with mortar shear strength, v¢
less than 30 psi shall be removed or pointed and retested.
E. Pointing. All deteriorated mortar joints in
unreinforced masonry walls shall be pointed according to Standard
No. 24-9. Nothing shall prevent pointing with mortar of all
masonry wall joints before the tests are made.
15.40.050 Oualit¥ control.
(a) Pointing. Special inspection shall be provided
during preparation and mortar pointing.
Exception: Pointing may be performed without special
inspection where approved by the Architect or Engineer.
4
ORIGIHAL ~
(b) Existing Floor or Roof Level Wall Anchors.
1. Floor level tension anchors embedded in brick. If
existing rod anchors embedded in brick are to be utilized as all or
part of the required wall anchorage system at the floor level, not
less than 5 percent of such existing rod anchors shall be tested by
an approved testing laboratory or under the supervision of the
Architect or Engineer. 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 5 percent of the total number of existing tension
anchors at each level. The test apparatus shall be supported on
the masonry wall at a minimum distance of the wall thickness from
the anchor tested. The rod anchor shall be given a preload of 300
lbs. prior to establishing a datum for recording elongation. The
tension test load reported shall be recorded at one-eighth 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. Ends of existing anchors shall be secured into the
wood framing by a positive mechanical attachment.
2. Floor or roof level anchors embedded in concrete.
Existing rod anchors at floor or roof levels that are embedded in
existing concrete or gunite applied to the opposite side of the
wall need not be tested provided such embedment is verified by
observation and report by an approved testing agency or the
Architect or Engineer for at least one anchor, and all anchors
observed, in each wall at each level for which such the anchors are
to be utilized as all or part of the required wall anchorage
system. Other evidence of such embedment may be approved by the
City Building Official.
(c) Testing of Bolts. One-fourth of new embedded bolts
in unreinforced masonry walls shall be tested by a testing
laboratory or Architect or Engineer using the procedure of U.B.C.
Standard No. 24-8.
Exception:
Special inspection in accordance with the
Building Code or continuous observation by the
Architect or Engineer may be provided during
installation in lieu of testing.
(d) Required Reports. The Architect or Engineer or
testing agency shall submit a signed report to the City Building
Official for each test, observation or inspection required by
Section 15.40.050 and 15.40.070(g). The report shall state the
test, observation, or inspection performed, the date, the results
of each individual test, observation or inspection, (including
those that fail to satisfy the intent of this Ordinance) and
5
ORIGINAL
whether to the best of the knowledge of the preparer of the report,
the results indicate compliance with this Ordinance.
15.40.060 Allowable desiqn values.
(a) Tension Anchors. Allowable values for tension anchors
are given in Table No. 1-B. A one-third increase is not allowed
for values listed in this table.
(b) Other Materials. Allowable values not specified in
this chapter shall be as specified elsewhere in the 1991 Uniform
Building Code.
15.40.070 Detailed systems design requirements.
(a) Lateral Force on Elements of Structures and
Nonstructural Components. Parts or portions of structures,
nonstructural components and their anchorage to the main structural
system shall be designed for lateral forces in accordance with the
following formula:
F = C W ................... (10-1)
P P P
Wp shall be as defined in Section 2332. The value of Cp
need not exceed the values set forth in Table No. 1C.
(b) Height to Thickness Limitations. Unreinforced masonry
wall height to thickness ratios shall not exceed the ratios set
forth in Table No. 1D. If a wall height to thickness ratio exceeds
the specified limits, the wall shall be laterally supported by
bracing members complying with Subsection (c)l or with Subsection
(c)2. Bracing systems shall be designed in accordance with Section
15.40.070(a). The wall thickness may include the thickness of
plaster, stucco or concrete that is determined by the Architect or
Engineer to be bonded to the full height of the wall between wall
anchors.
(c) Bracing Methods. 1. Vertical Bracing Members.
Vertical bracing members shall be attached to floor and roof
construction for their design loads independent 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.
2. Wall Bracing. The wall height may be measured to
bracing elements other than a floor or roof. Horizontal
spacing of the bracing elements and wall anchors shall
not exceed 6 feet on center nor 6 times the wall
thickness, whichever is less. Bracing elements shall be
6
ORIGINAl.
detailed to minimize the horizontal displacement of the
wall by the vertical displacement of the floor or roof.
(d) Wall Anchorage.
1. Anchor Locations. Unreinforced masonry walls shall be
anchored at the roof and floor levels in order to resist the forces
specified in this section.
2. Tension Anchor Requirements. Tension anchors shall
have a maximum spacing of 6 feet or 6 times the wall thickness,
whichever is less, and shall comply with the requirements set forth
in Table No. 1-B. Tension anchors used to resist required forces
may be assumed to develop the allowable values listed in Table No.
1-B. Tension anchors shall be secured to the rafters or joists to
transfer the required forces into the roof or floor sheathing.
3. New Tension Anchors. New Tension Anchors installed to
meet the requirements of this section shall be Combination Tension
and Shear Bolts, and shall be secured to the roof or flo0r framing
to develop tension and shear forces into the diaphragm.
4. Minimum Wall Anchorage Forces. New or existing
Tension Anchors shall anchor masonry walls to each floor or roof
with a capacity to resist a minimum tension force determined by
Formula (10-1) or 200 pounds per linear foot whichever is greater,
acting normal to the wall at the level of the floor or roof. In
addition, new Combination Tension and Shear Bolts shall be
connected to the framing to resist a shear force of 200 pounds per
foot acting parallel to the wall at the level of the floor or roof.
Exception: Where the roof or floor sheathing consists
only of 1 inch nominal thickness single board
sheathing, new Combination Tension and Shear
Bolts may be connected to the framing to
resist a shear force of 100 pounds per foot
acting parallel to the wall.
The City Building Official may approve an analysis by the Architect
or Engineer that demonstrates that the required shear capacity is
less than required by this section.
5. Anchors at Corners. New Combination Tension and Shear
Bolts at the roof and floor levels, if required by this Section,
shall be provided within two feet horizontally from the inside of
the corners of the walls."
(e) Parapets. Parapets and exterior wall appendages not
capable of resisting the forces specified in this section shall be
removed, stabilized or braced to ensure that the parapets and
appendages remain in their original position.
7
ORIGINAL
The maximum height of an unbraced unreinforced masonry
parapet above the level of tension anchors 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 determined by formula (10-1) shall be
installed to support the parapet. Parapet corrective work shall 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.
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.
(f). Mortar Joints. All deteriorated mortar joints in
unreinforced masonry walls shall be pointed with Type S or N
mortar. Masonry cements shall not be used. Prior to any pointing,
the wall surface must be raked and cleaned to remove loose and
deteriorated mortar. All preparation for pointing shall be
inspected by the Architect or Engineer or their representative.
(g). Masonry Veneer.
1. Veneer shall be anchored to the structure of the
building with approved anchor ties conforming to the required
design capacity specified in the Building Code and placed at a
maximum spacing of 24 inches with a maximum supported area of 2
square feet.
EXCETPION: I. Existing masonry veneer anchor ties may
be acceptable provided the ties are in sound condition and conform
to the following minimum size, maximum spacing and material
requirements:
Existing masonry veneer anchor ties shall be corrugated
galvanized iron strips not less than 1 inch in width, 8 inches in
length and 1/16 inch in thickness 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 center horizontally. As an
alternate, such ties may be laid in every fourth course vertically
at a spacing not to exceed 9 inches on center horizontally.
II. Masonry veneer, no portion of which 6 feet
is above grade need not be anchored.
2. The location and condition of existing veneer anchor
ties shall be verified as follows:
ORIGINAL
The Architect or Engineer shall determine the
location and spacing of the ties.
The veneer shall be removed from not less than four
locations designated by the Architect or Engineer
for the Architect or Engineer's evaluation.
The Architect or Engineer shall report to the City
Building Official the veneer anchor tie locations
and spacings, their evaluation of the condition and
effectiveness of the veneer anchor ties, and their
recommendations whether or not the existing veneer
anchor ties need to be supplemented with new veneer
anchor ties.
3. Unreinforced masonry walls which carry no loads other
than their own weight may be considered as veneer if they are
adequately anchored to new supporting elements.
Nos. i-A,
15.40.080 Tables and Standards.
For Time Limits and Technical Specifications see Table
l-B, l-C, and l-D; Standard Nos. 24-7 and 24-9.
TABLE NO. 1-A
TIME LIMITS FOR PROCEEDINGS
FOLLOWING DECEMBER 31, 1998 DEADLINE
Required Action
By Owner
Obtain Building
Permit Within
Commence
Construction
Within
Complete
Construction
Within
Anchorage
Installation
Buildings to
be Demolished
1 Year (1) 180 Days (2)
1 Year (1) 180 Days (2)
1 Year (2)
1 Year (2)
(1) Measured from the date of the order.
(2) Measured from the date of building permit issuance.
(3) These time limits shall not apply to a change of occupancy
involving a Group A Occupancy having an occupant load of 100 or
more.
ORIGINAL
TABLE NO. 1-B
ALLOWABLE VALUES FOR TENSION ANCHORS
TyDe of Installation
EXISTING TENSION ANCHORS:
Anchors at floor level embedded in brick
(to be tested per Section 15.40.050(b)
Allowable Values (1)
Allowable shall be 40%
of the average of the
tests for anchors having
same wall thickness and
joist orientation.
Anchors at floor or roof
levels embedded in existing concrete
or gunite on the opposite side of the
wall. (2)
TENSION BOLTS:
Bolts extending entirely through
unreinforced masonry walls secured
with bearing plates on far side of
a 3 wythe minimum wall with a
bearing plate having an area of at
least 30 square inches. (2) (3)
1800 lb. per anchor.
1800 lbs. per bolt.
900 lbs. for 2 wythe walls.
COMBINATION TENSION AND SHEAR BOLTS:
Combination tension and shear bolts
are tension bolts centered in a
2-1/2 inch diameter by 8 inch minimum
depth hole with dry-pack or nonshrink
grout around the circumference of bolt.
EMBEDDED BOLTS
Bolts extending to the exterior 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. Bolts shall be centered
in 2-1/2 inch diameter holes with
dry-pack or non-shrink grout around
circumference of bolts. Bolts shall
be tested per Section 15.40.050(c).
Same as for tension bolts.
1200 pounds.
10
ORIGINAL
(1) A one-third increase in allowable stresses is not allowed for the
tabulated values. The allowable capacity shall not be greater than
the capacity of the connection to the floor or roof framing.
(2)
(3)
Bolts to be 1/2 inch minimum in diameter.
Drilling for bolts and dowels shall be done with an electric rotary
drill. Impact tools shall not be used for drilling holes or
tightening anchors and shear bolt nuts.
TABLE NO. 1-C
HORIZONTAL FORCE FACTOR "Cp" FOR PARTS OR PORTIONS OF
BUILDINGS OR OTHER STRUCTURES
Part or Portion
of Buildings
Exterior bearing and nonbearing
walls; interior bearing walls
and partitions; interior non-
bearing walls and partitions
over 10 feet in height.
Direction Value
of Force C
Normal-to-flat 0.3
surface
of
Cantilever parapet and other
cantilever walls, except
retaining walls.
Normal-to-flat 1.00
surface
Exterior and interior ornamen-
tations and appendages.
Any direction
1.00
Prefabricated structural
elements, other than walls,
with force applied at center
of gravity of assembly.
Any horizontal 0.30
direction
Connections for exterior panels
or elements.
Any direction
2.00
11
ORIGINAL
TABLE NO. 1-D
ALLOWABLE VALUE OF HEIGHT-THICKNESS RATIO OF UNREINFORCED
MASONRY WALLS WITH MINIMUM QUALITY MORTAR
Buildings with Crosswalls
As Defined by Section
15.40.030
All Other
Buildings
Walls of one-story
buildings
First-story walls
of two-story
buildings
Walls in top story of
Multi-story buildings
16 13
16 15
14 9
All other walls 16 13
'12
ORIGINAL
SECTION 2.
This ordinance shall be posted in accordance with provisions of
the Bakersfield Municipal Code 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 AUG 1 1 .t~__~_% , by the following
vote:
AYES: COUNCILMEMBERS McDERMOTT, EDWARDS, DeMOND, SIdlTN, BR[,,%INI, ROWLES, ~kLVAGOJO
NOES: COUNCILMEMBERS ~.)O f'J ~:.
ABSTAIN: COUNCILMEMBERS fOc~ f,~ ~,
ABSENT: COUNCILMEMBERS ~/~K~ ~
CITY CLERK and Ex Officio Clerk of the
Council of the City of Bakersfield
APPROVED AUG I
APPROVED as to form:
LAWRENCE M. LUNARDINI
CITY ATTORNEY of the City of Bakersfield
LCM/kg
7-12-93
13
ORIGINAL
AFFIDAVIT OF POSTING DOCUMENTS
STATE OF CALIFORNIA)
) SS.
County of Kern )
CAROL WILLIAMS, being duly sworn, deposes and says:
That she is the duly appointed, acting and qualified City Clerk of
the City of Bakersfield; and that on the 13th day of August, 1993
she posted on the Bulletin Board at City Hall, a full, true and
correct copy of the following: Ordinance No. 3552, passed by the
Bakersfield City Council at a meeting held on the 11th day of
August, 1993, and entitled:
AN ORDINANCE AMENDING CHAPTER 15.40 OF THE BAKERSFIELD
MUNICIPAL CODE RELATING TO UNREINFORCED BUILDINGS.
By:
/s/ CAROL WILLIAMS
City Clerk of the City of Bakersfield
DEPUTY C~y C~rk