It is found and declared in the event of a strong or moderate
local earthquake, loss of life or serious injury may result from damage
or collapse of unreinforced masonry buildings in the city. The purpose
of this chapter is to promote public safety by establishing a set
of structural repair standards to be used to strengthen unreinforced
masonry buildings and require owners to make their buildings conform
to those standards within a reasonable period of time. The provisions
of this chapter are minimum standards for structural seismic resistance
established primarily to reduce the risk of life loss or injury but
will not necessarily prevent loss of life or injury or prevent earthquake
damage to an existing building which complies with these standards.
This seismic hazard reduction program is consistent with California
Health and Safety Code Sections 19160 through 19168 and Government
Code Sections 8875 through 8878 et seq.
(Ord. 1419 § 1, (1990))
For purposes of this chapter the words and phrases set out in
this section shall mean as follows.
means any wall supporting a floor or roof where the total
superimposed load exceeds 100 pounds per linear foot, or any unreinforced
masonry wall supporting its own weight when over six feet in height.
means a licensed civil or structural engineer registered
by the state pursuant to the rules and regulations of Title 16. Chapter
5 of the California Administrative Code.
means the total maximum number of occupants in the building
determined by either 1) Table 33-A of the Uniform Building Code or,
2) the actual maximum number of occupants in the building as certified
by the building owner and current tenants.
means that portion of a building included between the upper
surface of any floor and the upper surface of the floor next above,
except that the topmost story shall be that portion of a building
included between the upper surface of the topmost floor and the ceiling
or roof above.
means any building containing walls constructed wholly or
partially with any of the following materials and containing less
than fifty percent of the minimum area of reinforcing steel required
by the 1985 Uniform Building Code Section 2407 (h) 4 B:
(Ord. 1419 § 1, (1990))
Applicability. All unreinforced masonry buildings identified
by the city, except those used exclusively for residential purposes
containing five or less living units.
(Ord. 1419 § 1, (1990))
The owners of unreinforced masonry buildings determined to be within the scope of this chapter will be notified in writing by the chief building inspector according to the schedule set forth in Section 18.28.050(b).
(Ord. 1419 § 1, (1990))
(a)
Building Categories. Two categories of unreinforced masonry building
are hereby established to define the minimum lateral forces to be
used in their strengthening according to formula A-1-1.
1.
High risk buildings are those which have two or more stories or maximum
occupant load of more than 100 regardless of the number of stories.
High risk buildings also include any structure with an unreinforced
masonry parapet wall where the remainder of the building does not
contain unreinforced masonry walls.
2.
Medium risk buildings are those one story buildings with a maximum
occupant load of one hundred or less.
(b)
Implementation Schedule. The owners of all buildings within the scope
of this chapter must submit plans to obtain a building permit for
the structural modifications necessary to meet the minimum requirements
of this chapter by January 1, 1995.
The owners of all buildings within the scope of this ordinance
must complete construction of those structural modifications by June
30, 1996.
Notices providing a copy of the ordinance and stating the schedule
for owner action will be sent to each building owner within 90 days
of the effective date of the ordinance codified in this chapter.
(Ord. 1419 § 1, (1990); Ord. 1423 § 1, (1990))
Extensions of the time periods set forth in Section 18.28.050(b) may be granted by the city council based upon economic hardship. A request for an extension must be received at least 90 days before the expiration of the time period affected.
(Ord. 1419 § 1, (1990); Ord. 1423 § 3, (1990))
The procedures and engineering standards establishing a minimum level of structural strengthening required for all unreinforced masonry buildings within the scope of this chapter are set forth in Section 18.28.080 of this chapter. The Uniform Code for Building Conservation Appendix Chapter One only, published in 1985 by the International Conference of Building Officials, Whittier, California, with amendments is hereby adopted as a part of this ordinance and all references in Sections 18.28.080 through 18.28.117 are to that appendix.
(Ord. 1419 § 1, (1990))
Section A102 is amended to read as follows:
Section A102. The requirements of this chapter shall apply to
all buildings containing unreinforced masonry bearing walls.
Exception: This chapter shall not apply to a detached Group R, Division 3 Occupancy nor to a detached Group R, Division 1 Occupancy containing less than five dwelling units used solely for residential purposes.
(Ord. 1419 § 1, (1990))
Section A103 is amended to read as follows:
Sec. A103. Alternate materials, designs and methods of construction
may be approved by the Chief Building Inspector in accordance with
this code.
(Ord. 1419 § 1, (1990))
Section A105 is amended to read as follows:
Sec. A105. (a) General. A historic building may comply with
the special provisions set forth in this chapter and the provisions
of the State Historical Building Code.
(b)
Archaic Materials. Allowable stresses for archaic
materials not specified in this code shall be based on substantiating
research data or engineering judgment with the approval of the Chief
Building Inspector.
(Ord. 1419 § 1, (1990))
(a)
Section A106(a) through (d), (f)1 and (g)3 are amended to read as
follows:
Sec. A106. (a) General. Every structure within the scope of
this chapter shall be analyzed and constructed to resist minimum total
lateral seismic forces assumed to act nonconcurrently in the direction
of each of the main axes of the structure in accordance with the following
equation:
V = ZIKCSW (A1-1)
The value of KCS need not exceed but shall not be less than
.100 for one story buildings with less than 100 occupants; and need
not exceed but must not be less than .133 for one story buildings
containing 100 or more occupants and buildings over one story above
grade. The value of Z and I shall equal 1.0. The value of W shall
be as defined in Chapter 23 of the 1985 Uniform Building Code.
(b)
Lateral Forces on Elements of Structures. Parts or portions of buildings
shall be analyzed and designed for lateral loads in accordance with
Chapter 23 of the 1985 Uniform Building Code but not less than the
value from the following equation:
Fp = ICpSWp (A1-2)
For the provisions of this section, the product of IS shall
equal 1.0. The value of Cp shall be in accordance with Table 23-J
of the 1985 Uniform Building Code. The value of Wp shall be as defined
in Chapter 23 of the 1985 Uniform Building Code.
Exception: Unreinforced masonry walls in buildings not required
to be designed as an essential facility may be designed in accordance
with Section A107.
(c)
Regulated Elements of Buildings. The elements of buildings required
to be analyzed by this chapter include: 1) Height-to-thickness ratio
of masonry walls; 2) Tension bolts in bending; 3) In-plane shear stress;
4) Parapets; 5) Diaphragm stresses and diaphragm chords in floors
and roof.
(d)
Anchorage and Interconnection. Anchorage and interconnection of all
parts, portions and elements of the structure shall be analyzed and
designed for lateral forces in accordance with the 1985 Uniform Building
Code and the Formula (A1-2) of this code. Masonry walls shall be anchored
to all floors and roof to resist a minimum force of 200 pounds per
linear foot acting normal to the wall at the level of the floor or
roof.
(f)
Required Analysis. 1. General. Except as modified
herein, the analysis and design relating to the structural alteration
of existing buildings within the scope of this chapter shall be in
accordance with the analysis specified in the 1985 Uniform Building
Code. In addition the compatibility of the roof diaphragm stiffness
with the out-of-plane stability of the unreinforced masonry bearing
walls of the story immediately below the roof shall be verified in
accordance with the provisions of Section A109.
Exception: Buildings with rigid concrete or steel and concrete
roof diaphragms shall use the h/t values for all other buildings in
Table A1-F.
(g)
3. Unreinforced masonry walls. In addition to the seismic forces
required by this chapter, unreinforced masonry walls shall be analyzed
as specified in the 1985 Uniform Building Code to withstand all vertical
loads as specified in the Building Code. Such walls shall meet the
minimum requirements set forth in the Building Code.
Exception: When calculating shear or diagonal tension stresses
due to seismic forces, existing masonry shear walls may be designed
to resist 1.0 times the required forces in lieu of the 1.5 factor
required by the Building Code.
No allowable tension stress will be permitted in unreinforced
masonry walls. Walls not capable of resisting the required design
forces specified in this chapter shall be strengthened or shall be
removed and replaced.
Exceptions:
1.
Unreinforced masonry walls in buildings not classified as an essential
facility may be analyzed in accordance with Section A107.
2.
Unreinforced masonry walls which carry no design loads other than
their own weight may be considered veneer if they are adequately anchored
to new supporting elements.
Substantial changes in wall thickness or stiffness shall be
considered in the analysis for out-of-plane and inplane wall stability,
and the wall shall be restrained against out-of-plane instability
by anchorage and bracing to the roof or floor diaphragm in accordance
with Section A106(d).
Exception: Variations in wall stiffness caused by nominal openings
such as windows and doors need not be considered.
(Ord. 1419 § 1, (1990))
Section A107(b), (d) and (f) are amended to read as follows:
(b)
Existing Materials. 1. Unreinforced masonry walls.
Unreinforced masonry walls analyzed in accordance with this chapter
may provide vertical support for roof and floor construction and resistance
to lateral loads.
All units of both bearing and non-bearing walls shall be laid
with full shoved mortar joints; all head, bed and wall (collar) joints
shall be solidly filled with mortar; and the bonding of adjacent wythes
of multi-wythe walls shall be as follows:
The facing and backing shall be bonded so that not less than
4 percent of the wall surface of each face is composed of headers
extending not less than four inches into the backing. The distance
between adjacent fulllength headers shall not exceed 24 inches either
vertically or horizontally. In walls where a single header does not
extend through the wall, headers from the 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 to calculate the height-to-thickness ratio and the
shear capacity of the wall.
Tension stresses due to seismic forces normal to the wall may
be neglected if the wall does not exceed the height-to-thickness ratio
set forth in Table A1-F and the in-plane shear stresses due to seismic
loads set forth in Table A1-I. If the wall height-to-thickness ratio
exceeds the specified limit, the wall may be supported by vertical
bracing members designed to satisfy the requirements of the 1985 Uniform
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 bracing members
designed in accordance with Section A106(b) of this chapter if the
deflection at design loads is not less than one-quarter nor more than
one-third of the wall thickness at the level under consideration.
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 members shall
not exceed one-half the unsupported height of the wall nor ten feet,
whichever is less.
The wall height may be measured vertically to bracing elements
other than a floor or roof. Spacing of bracing elements and wall anchors
shall not exceed six feet. Bracing elements shall be detailed to minimize
the horizontal displacement of the wall by components of vertical
displacements of the floor or roof.
|
2.
|
Veneer. Veneer shall be anchored with approved anchor ties,
conforming to the required design capacity specified in Section 3304(c)
of the 1985 Uniform Building Code, and placed at a maximum spacing
of 24 inches.
|
Exception: Existing veneer anchor ties may be acceptable
provided the ties are in good condition and conform to the minimum
size, maximum spacing and material requirements as indicated below.
The 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 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, the spacing may
be every fourth course vertically at a spacing not to exceed nine
inches on center 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 Chief Building Inspector
for approval 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 Chief Building
Inspector.
3.
Existing roof, floors, walls, footings, and wood framing. Existing
materials, including wood shear walls, may be used as a part of the
lateral load resisting system, provided that stresses in these materials
do not exceed the values shown in Table No. A1-G.
(d)
Minimum Acceptable Quality of Existing Unreinforced
Masonry Walls. 1. General Provisions. All unreinforced masonry walls
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. The vertical wall joint between wythes (collar joint)
shall be inspected at each test location after the in-place shear
tests, 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.
Nothing shall prevent the 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
shall not be used. All preparation and mortar pointing shall be done
under the continuous inspection of a special inspector.
At the conclusion of the inspection, the inspector shall submit
a written report to the person responsible for the seismic analysis
of the building setting forth the results of the work inspected. Such
report shall be submitted to the Chief Building Inspector for approval
as part of the structural analysis. All testing shall be performed
in accordance with the requirements specified in this section by an
approved agency. An accurate record of all such tests and their location
in the building shall be recorded and these results shall be submitted
to the Chief Building Inspector for approval as part of the structural
analysis.
2.
Number and location of tests. The minimum number
of tests shall be as follows. At each of both the first and top stories,
not less than two per wall line or line of wall elements providing
a common line of resistance to lateral forces. At each of all other
stories, not less than one per wall element providing a common line
of resistance to lateral forces. 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 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.
Where the higher h/t ratios allowed in footnotes 4 and 5 of
Table A1-F are to be utilized, all the in-place shear tests taken
at the top story shall be included in the 80 percent of the shear
tests used to determine the minimum mortar shear strength. The exact
test locations shall be determined at the building site by the person
responsible for the seismic analysis of the subject building.
3.
In-place shear tests. The bed joint of the outer wythe of the masonry
wall shall be tested by laterally displacing a single brick relative
to the adjacent bricks in the wythe. The head joint opposite the load
end of the test brick shall be carefully excavated and removed. 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 bricks shall be used on each end of the ram and shall
not contact the bed joints. The load shall be applied horizontally
in the plane of the wythe until either a crack can be seen or a slip
occurs. The strength of the mortar shall be calculated by dividing
the load at the time of the first crack or movement by the nominal
gross area of the sum of the two bed joints.
(f)
Determination of Allowable Stresses for Design Methods Based on Test Results. 1. Design shear values. Design seismic in-plane shear stresses shall be substantiated by tests performed as specified in Item No. 3 of Subsection (d). The minimum quality mortar in 80 percent of the tests shall not be less than the total of 30 psi when reduced to an equivalent zero axial stress.
Design stresses shall be related to test results obtained in
accordance with Table No. A1-I. Intermediate values between 5 and
10 psi may be interpolated.
(Ord. 1419 § 1, (1990))
Section A108(b) and (c) are amended to read as follows:
(b)
Construction Details. The following requirements
with appropriate construction details shall be made a part of the
approved plans:
1.
All unreinforced masonry walls shall be anchored at the roof and
ceiling levels by tension bolts through the wall as specified in Table
A1-H, or by an approved equivalent at a maximum anchor spacing of
six feet.
All unreinforced masonry walls shall be anchored at all floors
and ceiling with tension bolts through the wall or by existing rod
anchors at a maximum anchor spacing of six feet. All existing rod
anchors shall be secured to the joists to develop the required forces.
Tests conforming to this chapter will be required to verify the adequacy
of the embedded ends of existing rod anchors.
Exception: Walls need not be anchored to ceiling systems that,
because of their low mass and or relative location with respect to
the floor or roof systems, would not impose significant normal forces
on the wall and cause out-of-plane wall failure. Calculations and
drawings to verify this exception must be submitted as part of the
analysis.
At the roof and all floor levels, the anchors nearest the building
corners shall be combination shear and tension anchors located not
more than two feet horizontally from the inside corners of the walls.
When access to the exterior face of the masonry wall is prevented
by proximity of an existing building, wall anchors conforming to Items
5 (a) or (b) in Table No. A1-H may be used.
Alternative devices to be used in lieu of tension bolts for
masonry wall anchorage shall be tested as specified in Section A107(h).
2.
Diaphragm chord stresses of horizontal diaphragms shall be developed
in existing materials or by the addition of new materials.
3.
Where trusses and beams other than rafters or joists are supported
on masonry independent secondary columns shall be installed to support
vertical loads.
4.
Parts and exterior wall appendages not capable of resisting the forces
specified in this chapter shall be removed, 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 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
the Table 23-J of the 1985 Uniform Building Code shall support the
top of the parapet. Parapet corrective work must be performed in conjunction
with the installation of tension roof anchors.
The minimum height of a parapet above the wall anchor shall
be 12 inches.
Exception: If a reinforced concrete beam is provided at the
top of the wall, the minimum height above the wall anchor may be six
inches.
5.
All deteriorated mortar joints in unreinforced masonry walls shall
be pointed with Type S or N mortar. Prior to any pointing, the wall
surface must be raked and cleaned to remove loose and deteriorated
mortar. All preparation and pointing shall be done under the continuous
inspection of a special inspector. At the conclusion of the project,
the inspector shall submit a written report to the Chief Building
Inspector setting forth the portion of work inspected.
6.
Repair details for any cracked or damaged unreinforced masonry wall
required to resist forces specified in this chapter.
(c)
Existing Construction. The following existing construction information
shall be made part of the approved plans:
1.
The type and dimensions of existing walls and the size and spacing
of floor and roof members.
2.
The extent and type of existing wall anchorage to floors and roof.
3.
The extent and type of any parapet bracing or other structural reinforcement
to parts and portions of the building which were previously performed.
4.
Accurately dimensioned floor plans and masonry wall elevations showing
dimensioned opening, piers, wall thickness and heights, veneer locations
and existing anchorages.
5.
The locations of cracks or other damaged portions of unreinforced
masonry walls requiring repair.
6.
The type of interior wall surfaces and ceilings, and if reinstalling
or anchoring of existing plaster is necessary.
7.
The general condition of the mortar joints and if the joints need
repointing.
8.
The location of all in-place shear tests shall be shown on the floor
plans and building wall elevations.
(Ord. 1419 § 1, (1990))
Section A109 is added to read as follows:
Design Check for Compatibility of Roof Diaphragm Stiffness to
Unreinforced Masonry Wall Out-of-Plane Stability.
Sec. A109
(a)
General. The requirements of this section are in addition to the
other analysis requirements of this Chapter. The relative stiffness
and strength of a diaphragm governs the amount of amplification of
the seismic ground motion by the diaphragm, and therefore, a diaphragm
stiffness and strength related check of the out-of-plane stability
of unreinforced masonry walls anchored to wood diaphragms shall be
made. This section contains a procedure for evaluation of the out-of-plane
stability of unreinforced masonry walls anchored to wood diaphragms
that are coupled to shear resisting elements.
(b)
Cross Wall.
Demand Capacity Ratio (DCR).
1.
2.
Definitions. The following definitions are applicable to this section.
A wood framed wall having a height to length ratio complying
with Section 4713(d) or Table 25-I of the 1985 Uniform Building Code
and sheathed with any of the materials described in Table A1-J or
Table A1-K. The total strength of all cross walls located within any
40 feet length of diaphragm measured in the direction of the diaphragm
span shall not be less than 30 percent of the strength of the diaphragm
in the direction of consideration.
A ratio of the following:
Demand equals the lateral forces due to 33 percent of the combined
weight of the diaphragm and the tributary weight of the wall and other
elements anchored to the diaphragm.
Capacity equals the diaphragm total shear strength in the direction
under consideration as determined using the values in Tables No. A1-J
or Table A1-K.
(c)
Notations.
D = depth of diaphragm, in feet, measured perpendicular to the
diaphragm span.
h/t = height-to-thickness of an unreinforced masonry wall. The
height shall be measured between wall anchorage levels and the thickness
shall be measured through the wall cross section at the level under
consideration.
L = span of diaphragm between masonry shear walls or steel frames.
Vc = total shear capacity of cross walls in the direction of
analysis immediately below the diaphragm level being investigated
as determined by using Tables No. A1-J and A1-K.
vu = maximum shear strength in pounds per foot for a diaphragm
sheathed with any of the materials given in Tables No. A1-J or A1-K.
Wd = total dead load of the diaphragm plus the tributary weight
of the walls anchored to the diaphragm, the tributary ceiling and
partitions and weight of any other permanent building elements at
the diaphragm level under consideration.
(d)
Design Check Procedure.
1.
General. The demand capacity ratio (DCR) for the building shall be
calculated using the following equations:
DCR = 0.33 Wd / 2vu D For building without cross walls or
DCR = 0.33 Wd / 2vu D + Vc For building with cross walls
2.
Diaphragm Deflection. The calculated DCR shall be to the left of
the curve in Figure No. A1-L. Where the calculated DCR is outside
(to the right of) the curve, the diaphragm deflection limits are exceeded
and cross walls may be used to reduce the deflection.
3.
Unreinforced Masonry Wall Out-of-Plane Stability. The DCR shall be
calculated discounting any cross wall. If the DCR from this method
corresponding to the diaphragm span is to the right of the curve in
Figure No. A1-L, the region within the curve at and below the intersection
of the diaphragm span with the curve may be used to determine the
allowable h/t values per Table No. A1-F.
(Ord. 1419 § 1, (1990))
Tables No. A1-A, A1-B, A1-C, A1-D and A1-E are deleted and Tables
A1-F and A1-H are amended to read as follows:
|
TABLE NO. A1-F
ALLOWABLE VALUE OF HEIGHT-THICKNESS (h/t) RATIO OF UNREINFORCED
MASONRY WALLS WITH MINIMUM QUALITY MORTAR12
| ||
|---|---|---|
|
|
BUILDINGS WITH COMPLYING CROSS WALLS
|
ALL OTHER BUILDINGS
|
|
One Story Building Walls
|
13 — 16345
|
13
|
|
First Story of Multi-Story Buildings
|
16
|
15
|
|
Walls in the Top Story of Multi-Story Buildings
|
9 — 14345
|
9
|
|
All Other Walls
|
16
|
13
|
|
1
|
Minimum mortar quality shall be determined by laboratory testing
in accordance with this chapter.
|
|
2
|
This table is not applicable to buildings classified as essential
facilities. Such building must be analyzed in accordance with Section
A106.
|
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3
|
The minimum mortar shear strengths required in the following
footnotes 4 and 5 shall be that shear strength without the effect
of axial stress in the wall at the point of the test.
|
|
4
|
The larger height-to-thickness ratio may be used where mortar
shear tests in accordance with Section A107(d) establish a minimum
mortar shear strength of not less than 100 psi or where the tested
mortar shear strength is not less then 60 psi and a visual examination
of the vertical wythe-to-wythe wall joint (collar joint) indicates
not less than 50 percent mortar coverage.
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|
5
|
Where a visual examination of the collar joint indicates not
less than 50 percent mortar coverage and the minimum mortar shear
strength when established in accordance with Section A107(d) 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 ratio values in direct proportion to the mortar shear
strength.
|
|
TABLES NO. A1-H
ALLOWABLE VALUES OF NEW MATERIALS USED IN CONJUNCTION WITH EXISTING
CONSTRUCTION
| |
|---|---|
|
New Materials or Configuration of Materials1
|
Allowable Values
|
|
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 within the center 1/3 of individual sheathing boards.
|
Same as specified in Table 25-J of the 1985 Uniform Building
Code for blocked diaphragms.
|
|
2. Shear Walls
|
Same as values specified in Table
|
|
a. Plywood sheathing applied directly over
existing wood studs. (No value shall be given to plywood applied over
existing plaster or wood sheathing boards).
|
No. 25-K of the 1985 UBC for shear walls.
|
|
b. Dry wall or plaster applied directly over
existing wood studs.
|
75 percent of the values specified in Table No. 47-I of the
1985 UBC.
|
|
c. Dry wall or plaster applied to plywood
sheathing over wood studs.
|
One-third of the values specified in Table No. 47-I of the 1985
UBC.
|
|
3. Shear Bolts
Shear bolts and shear dowels embedded a minimum of 8 inches
into unreinforced masonry walls. Bolt centered in a 2-1/2 inch diameter
hole with drypack or non-shrink grout around the circumference of
the bolt.13
|
133 percent of the values for plain masonry specified in Table
No. 24-J of the 1985 UBC. No values larger than those given for 3/4
inch diameter bolts shall be used.
|
|
4. Tension Bolts
Tension bolts and tension dowels extending entirely through
URM walls secured with bearing plates on far side of wall with at
least 30 square inches of area.234
|
1200 pounds per bolt.
|
|
5. Combination Shear and Tension Wall Anchors
|
|
|
(a) Bolts extending to 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.123
|
600 lbs. per bolt for tension4. See
Item 3 (Shear Bolts) for shear values.
|
|
(b) Bolts or dowels extending to the exterior
face of the wall with a 2-1/2 inch round plate under the head and
drill at an angle of 22-1/2 degrees to the horizontal. Install as
specified for shear bolts.123
|
1200 lbs. per bolt or dowel for tension4. See Item 3 for shear values.
|
|
(c) Through bolt with bearing plate for tension
per Item 4. Combined with minimum 8 inch grouted section for shear
per Item 3.
|
See Item 4 (Tension Bolts) for tension values4. See Item 3 for shear values.
|
|
6. Infilled Walls
Reinforced masonry infilled openings in existing unreinforced
masonry walls with keys or dowels to match reinforcing.
|
Same as values specified for unreinforced masonry walls in this
chapter.
|
|
7. Reinforced Masonry
Masonry piers and walls reinforced as specified in Chapter 24
of the 1985 Uniform Building Code.
|
Same as values specified in Table No. 24-B of the Uniform Building
Code. 1985
|
|
8. Reinforced Concrete
Concrete footings, walls and piers reinforced as specified in
Chapter 26 and designed for tributary loads.
|
Same as values specified in Chapter 26 of the 1985 Uniform Building
Code
|
|
9. Existing Foundation Loads
Foundation loads for structures exhibiting no evidence of settlement.
|
Calculated existing foundation loads due to maximum dead load
plus live load may be increased by 25 percent and may be increased
50 percent for dead load plus seismic loads required by this chapter.
|
|
1
|
Bolts and dowels to be tested as specified in Section A107.
|
|
2
|
Bolts and dowels to be 1/2-inch diameter minimum.
|
|
3
|
Drilling for bolts and dowels shall be done with an electric
rotary drill. Impact tools shall not be used for drilling holes or
tightening anchor and shear bolt nuts.
|
|
4
|
Allowable bolt and dowel values specified are for installations
in minimum three wythe wall. For installations in two wythe walls
use 50 percent of the value specified, except that no value shall
be given to tension bolts that do not extend entirely through the
wall and are secured with bearing plates on the far side.
|
(Ord. 1419 § 1, August 20, 1990)
Table Nos. A1-J and A1-K and Figure A1-L are added to read as
follows:
|
TABLE NO. A1-J
ALLOWABLE VALUES FOR EXISTING MATERIALS TO BE USED ONLY IN THE
COMPUTATION OF THE DEMAND CAPACITY RATIO DESIGN CHECK
| |
|---|---|
|
Existing Materials or Configuration of Materials1
|
Allowable Values
|
|
1. Horizontal Diaphragms
|
|
|
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 lbs. per foot for seismic shear.
|
|
2. Cross Walls2
|
Per Side:
|
|
a. Plaster on wood or metal lath.
|
200 lbs. per foot for seismic shear.
|
|
b. Plaster on gypsum lath.
|
175 lbs. per foot for seismic shear.
|
|
c. Gypsum wall board unblocked edges.
|
75 lbs. per foot for seismic shear.
|
|
d. Gypsum wall board blocked edges.
|
125 lbs. per foot for seismic shear.
|
|
1
|
Materials must be sound and in good condition.
|
|
2
|
For cross walls, values of all materials may be combined, except
the total combined value shall not exceed 300 lbs. per foot for seismic
shear.
|
|
TABLE NO. A1-K
ALLOWABLE VALUES FOR NEW MATERIALS USED IN CONJUNCTION WITH
EXISTING CONSTRUCTION MATERIALS TO BE USED ONLY IN THE COMPUTATION
OF THE DEMAND CAPACITY RATIO DESIGN CHECK
| |
|---|---|
|
New Materials or Configuration of New and Existing Materials1
|
Allowable Values
|
|
1. Horizontal Diaphragms
|
|
|
a. Plywood sheathing applied directly over existing straight
sheathing with ends of plywood sheets bearing on rafters and edges
of plywood located on the center of individual sheathing boards.
|
225 lbs. per foot for seismic shear.
|
|
2. Cross Walls
|
|
|
a. Plywood sheathing applied directly over existing wood
studs. No value shall be given to plywood applied over existing plaster
or wood sheathing.
|
1.33 times the values specified in Table 25-K of the 1985 UBC.
|
|
b. Drywall or plaster applied directly over existing wood
studs.
|
100 percent of the values specified in Table 47-I of the 1985
UBC.
|
|
1
|
Materials must be sound and in good condition.
|
|
2
|
For cross walls values of all materials may be combined, except
the total combined shear value shall not exceed 300 lbs. per foot
for seismic shear.
|
|
FIGURE A1-L
| |
|
1.
|
Region of demand/capacity ratios where cross walls may be used
to increase H/T ratios.
|
|
2.
|
Region of demand/capacity ratios where H/T ratios of "with cross
walls" may be used whether or not they are present.
|
|
3.
|
Region of demand/capacity ratios where H/T ratios of "all other
buildings" must be used even if cross walls are present.
|
|
Demand/capacity ratio = 0.33 Wd / 2 vuD or 0.33 Wd / 2 vuD +
Vc.
| |
(Ord. 1419 § 1, August 20, 1990)
It is unlawful for the owner of a building identified as being within the scope of this ordinance to fail to submit plans and obtain a permit for correction of structural deficiencies discovered, or fail to complete the necessary structural corrections within the time period specified in Section 18.28.050(b). The city may invoke all remedies available at law, including, but not limited to, the following.
(a)
The city may revoke the building's certificate of occupancy and cause
it to be vacated until such requirements are met.
(b)
The city may seek injunctive relief on behalf of the public to enjoin
a building owner's violation of this ordinance.
(Ord. 1419 § 1, August 20, 1990)
