Ord 1800 - Urgency Ordinance Los Gatos Restoration ProgramORDINANCE NO: 1800
URGENCY ORDINANCE OF THE TOWN OF LOS GATOS
ESTABLISHING THE LOS GATOS RESTORATION
PROGRAM FOR THE REPAIR, RESTORATION AND
RECONSTRUCTION OF STRUCTURES DAMAGED AS A
RESULT OF THE OCTOBER 17, 1989 EARTHQUAKE
WIIEREAS, conditions of extreme peril to the safety of persons and property have
arisen in the Town of Los Gatos caused by an earthquake that occurred on October 17,
1989; and
WHEREAS, it is necessary to suspend any section of the Town Code or Zoning
Ordinance that is inconsistent with the intent and purpose of this urgency ordinance; and
WHEREAS, on October 22, 1989, the Town Council of the Town of Los Gatos
adopted a Proclamation Confirming the Town Manager's Proclamation of the Existence of
a Local Emergency; and
WHEREAS, numerous structures within the Town limits have suffered damage
caused by the earthquake and the owners of these structures are desirous of repairing,
restoring or reconstructing said structure as expeditiously as possible; and
WHEREAS, on October 22, 1989, the Town Council expressed the policy of the
Town to encourage the repair, restoration and reconstruction and reconstruction of
damaged structures so that the Town may return to its appearance as existed prior to the
earthquake and directed that procedures be established to facilitate said repair, restoration
and reconstruction.
THE TOWN COUNCIL OF THE TOWN OF LOS GATOS DOES HEREBY ORDAIN:
SECTION I
Purpose and Intent
This Urgency Ordinance is intended to establish procedures and regulations for the
repair, restoration and reconstruction of the structures damaged as a result of the
earthquake that occurred on October 17, 1989 or the aftershocks that occurred subsequent
to the main earthquake (hereafter "earthquake ").
The purpose of this Urgency Ordinance is to provide for the expeditious repair,
restoration and reconstruction of structures damaged as a result of said earthquake. All
reasonable efforts shall be made to restore the facades of the damaged structures or to
replicate the facade as it existed prior to the earthquake. The facades of nondescript
structures may be modified to include design features that are compatible with other nearby
structures and which clearly contribute to the character of the streetscape.
SECTION II
Establishment of Restoration Committee
The Los Gatos Restoration Committee (hereafter 'Restoration Committee ") is
hereby established to advise the Planning Director and the Director of Building Services
in their joint decision concerning the issuance, denial, revocation or suspension of any
permit to demolish, repair, restore or reconstruct any structure damaged as a result of the
earthquake.
The members of the Restoration Committee shall be the following persons or their
designees:
1. Planning Director,
2. Director of Building Services,
3. Town Engineer,
4. Chief of the Central Fire District,
5. Chief of the Police Department,
6. Director of Parks, Forestry and Maintenance Services, and
7. Town Retained Historic Resources Consultant.
The Restoration Committee shall meet on a regular basis and make written
recommendations to the Planning Director and the Director of Building Services. The
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applicant shall be entitled to be present at the meeting of the Restoration Committee with
his or her representatives.
SECTION III
Standards for Repair. Restoration and
Reconstruction of Masonry Buildings
The Town hereby adopts by reference the Uniform Code for Building Conservation
(1985 edition) except for the deletion of Chapters 1 and 2 and with the addition of
Appendix Chapter 1 (Earthquake Hazard Reduction in Existing Unreinforced Masonry
Buildings as amended by the Town - Exhibit A). All unreinforced masonry structures
damaged as a result of the earthquake shall be repaired, reconstructed , rebuilt or restored
in accordance with the Uniform Code for Building Conservation as denominated herein
except that unreinforced chimneys shall be reconstructed in accordance with Section 4 of
this Urgency Ordinance. The owner(s) of all unreinforced masonry buildings that were not
damaged by the earthquake shall submit a structural engineering analysis as set forth in
Appendix A. The structural analysis shall be submitted on or before May 1, 1990. The
Director of Building Services may revoke occupancy of structures whose owner(s) do not
meet the deadline. The repair or restoration of other structures shall be governed by
Section 5 of this Urgency Ordinance.
SECTION IV
Reconstruction of Unreinforced Chimneys
Unreinforced chimneys damaged by the earthquake shall be reconstructed in
accordance with the seismic safety standards set forth in Chapter 37 of the currently
adopted edition of the Uniform Building Code, and be made to the satisfaction of the
Director of Building Services.
3
SECTION V
Repair. Restoration and Reconstruction of
Reinforced Masonry Structures, Woodframe
Structures and Other Types of Structures
The repair, reconstruction and reconstruction or restoration of reinforced masonry
structures, woodframe structures and other types of structures shall be made in accordance
with 75% of the current Uniform Building Code value for lateral forces to the satisfaction
of the Planning Director and the Director of Building Services.
SECTION VI
Historic Structures
Structures that are historically designated or located within a historic district shall
not require review by the Historic Preservation Committee or the Planning Commission and
shall be reviewed only by the Restoration Committee.
SECTION VII
Demolition Permits
Demolition permits for structures damaged by the earthquake shall be approved by
the Town Manager, Planning Director and the Director of Building Services only where it
has been determined by the Director of Building Services that the structure cannot feasibly
be repaired. Before any demolition permit may be issued, the structure shall be
photographed, including architectural detail, to the satisfaction of the Planning Director.
Any architectural detail uncovered during the demolition shall also be photographed to the
satisfaction of the Planning Director. The Director of Building Services may require the
preparation of a detailed structural analysis in order to assist in determining whether a
structure cannot feasibly be repaired.
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SECTION VIII
Temporary Structures
The Planning Director may approve permits for temporary structures on properties
where a structure has been damaged by the earthquake and has been determined
uninhabitable by the Director of Building Services. The permit for said temporary structure
shall be for a limited period of time as determined by the Planning Director and shall be
abated by that date unless an extension is granted by the Planning Director.
SECTION IX
Waiver of Zoning Ordinance and Town Code Requirements
The Planning Director and the Director of Building Services shall have the authority
to waive the requirements of the Town Zoning Ordinance and the Town Code to the extent
that such provisions are contrary to the intent and purpose of this Urgency Ordinance.
SECTION X
Appeals
The appeal of any decision by the Planning Director or the Director of Building
Services permitted by this Urgency Ordinance shall be appealable to the Town Council.
The appellant shall file a written notice of appeal with the Town Clerk not more than ten
(10) days from the date of the decision. The appeal shall be heard by the Town Council
within forty -five (45) days after filing of the notice of appeal. The Town Council may
continue from time to time any hearing held. The Town Clerk shall set the hearing date
for the appeal and shall give a notice of such hearing to the appellant and publish a notice
in a newspaper of general circulation ten (10) days prior to the hearing.
When hearing the appeal the Town Council shall consider the staff report, the
applicable codes, regulations and standards involved and such additional evidence or
testimony given at the hearing and may affirm, modify or reverse, in whole or part, the
action being appealed. The decision of the Town Council upon the appeal shall be
expressed by a written resolution, a copy of which shall be transmitted to the appellant, the
Planning Director and the Director of Building Services. If the decision of the Town
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Council is adverse to that of the Planning Director and the Director of Building Services,
the resolution shall contain findings used in making their decision.
SECTION XI
Waiver of Fees
All Town fees for any and all permits associated with the repair, reconstruction,
restoration or demolition of any structure damaged as a result of the earthquake are
waived.
SECTION XII
Non - Applicability
The provisions of this Urgency Ordinance shall not apply to the repair or
construction of any structure that is not to be restored to the appearance of said structure
prior to the earthquake.
SECTION XHI
Severabilitv
If any section, subsection, sentence, clause or phrase of this Urgency Ordinance is
for any reason held by a court of competent jurisdiction to be invalid or unconstitutional,
such decision shall not affect the validity of the remaining portions of this Urgency
Ordinance and each section, subsection, sentence, clause and phrase thereof, irrespective
of the fact that any one or more sections, subsections, sentences, clauses or phrases be
declared invalid or unconstitutional.
C
SECTION XIV
CEOA Exemption
This urgency ordinance and any permits approved hereunder are exempt from the
requirements of the California Environmental Quality Act (CEQA) pursuant to Public
Resources Code Section 21080 (b)(2) and (3) and Section 21172 and Section 15269 of the
CEQA Guidelines.
SECTION XV
It is necessary for the immediate preservation of the public peace, health and safety
that this ordinance take effect immediately to preserve the economic viability of the
community, and to insure that the character of the community is preserved.
SECTION XVI
This ordinance takes effect immediately upon its adoption and shall remain in effect
until and including November 6, 1990. Within fifteen (15) days after this ordinance is
adopted, the Town Clerk shall cause it to be published once in a newspaper of general
circulation published and circulated in the Town.
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This ordinance was adopted by the following vote as an urgency ordinance of the
Town of Los Gatos at a regular meeting of the Town Council on November 6, 1989.
AYES: COUNCIL MEMBERS: Thomas J. Ferrito, Robert L. Hamilton
Brent N. Ventura, Mayor Joanne Benjamin
NAYES: COUNCIL MEMBERS: NONE
ABSENT: COUNCIL MEMBERS: Eric D. Carlson
ABSTAIN: COUNCIL MEMBERS: NONE
SIGNED: /limn �l i ✓N
MAYO OF THE TOWN OF OS GATOS
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ATTEST:
/ KO A/ LEPvvL d .
CLERK OF THE TOWN OF LO GATOS
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TOWN OF LOS GATOS
APPENDIX A
GUIDE FOR
STURCTURAL INVESTIGATION AND ANALYSIS
OF UNREINFORCED MASONRY
BEARING WALL BUILDINGS
SCOTT BAKER
DIRECTOR OF BUILDING SERVICES
EXHIBIT A
APPENDIX A
FOR INVESTIGATION OF URM BEARING WALL BUILDINGS
(a) Preliminary Field Survey From existing plans or from
field investigation prepare framing plans for roof and upper floors
noting all beams, trusses, and major lintels at bearing walls.
Prepare elevations of all URM walls noting the location and size of
all openings in the walls.
(b) Items for Special Investiaation
(1) Identify and include on the plans all parts of the
vertical load carrying system that may act as ties to lateral load
resisting elements, to determine the elements that may control the
relative displacement between the building's base and roof.
(2) Identify and include on the plans all undamaged
interior crosswalls that are continuous between the ground floor and
roof noting if these are connected to the upper floor or roof by
methods other than attachment of wall and ceiling finishes.
(3) Examine and draw the relationship of the roof or
floor framing to the ceiling framing (if separate) to determine the
method if any of their interconnection.
(4) Identify and include on the plans the support system
for any URM walls that are not continuous to the base of the
building noting the materials used for this support. (ie. steel
frame).
(5) Identify and include on the plans a description of
the floor and roof sheathing and its attachment. Note any
difference in materials on a given level that could lead to
substantial variations in diaphragm stiffness. Note the size and
location of openings in diaphragms adjacent to URM walls. Identify
the roof covering system used and note if there are locations where
it is on a cricket or other superimposed deck.
A thorough investigation of the roof diaphragm is necessary to
permit the evaluation of the compatibility of its stiffness with the
out -of -plane stability of the URM walls of the story immediately
below the roof as required in section (c) of the analysis procedure
of this appendix.
Exception: Where the damage conditions of a building prevent
adequate investigation of any of the items listed
above the Director of Building Services may exempt
those upon request from the engineer performing the
investigation. Assumptions regarding structural
conditions or materials not directly observed or
taken from existing plans must be clearly noted in
the investigation report and analysis.
(c) Investiaation of Existina Anchorage of URM Walls to Upper
Floor and Roof. Indicate the location of all existing
wall anchors on the roof /floor framing plans and specify their
spacing, size and method of connection. If existing anchors are to
be utilized as connections for resisting lateral force in the
analysis these will require testing as specified in section (e)l.
(d) Investigation of Existing URM Walls Investigate the
following items if they occur in the building, and determine:
(1) The thickness of URM walls at all levels and location
of any changes in thickness. Substantial changes in wall thickness
or stiffness shall be considered in the analysis for out -of -plane
and in -plane wall stability. Variations in wall stiffness caused by
nominal openings such as windows and doors need not be considered.
(2) The materials used for lintels or arches at openings
and their bearing area and connection to supporting columns or
piers. The materials used for columns or piers supporting lintel
beams or arches.
(3) The heights of parapet, cornices and gable ends of
URM walls above the uppermost existing anchorages.
(4) The anchorage or bonding of terra cotta, cast -stone
brick veneer or similar facing materials to the backup wythes of
brickwork at cornices and other architectural appendages.
(5) The coursing of exterior wythes of masonry, the
bonding of wythes of masonry, and the materials used in each wythe.
An examination of the wall joint between wythes (collar joint) must
be made at each in -plane shear test location to estimate the
percentage of wythe to wythe mortar coverage and the estimate shall
be reported wit the results of the tests.
Wythes of walls not bonded as described below shall be
considered veneer The veneer wythe shall not be included in the
effective thickness of the wall used to calculate the height -to-
thickness ratio and the shear capacity of the wall and methods for
its adequate anchorage must be devised.
All units of URM bearing and non - bearing walls shall be laid
with full shoved mortar joints; all head, bed and 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 full length headers shall not exceed 24 inches
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.
(6) The condition of mortar joints and the location of
any existing cracks or damaged portions of wall elements.
Exception: Where the damage conditions of a building prevent
adequate investigation of any of the items listed
above the Director of Building Services may exempt
those upon request from the engineer performing the
investigation. Assumptions regarding structural
conditions or materials not directly observed or
taken from existing plans must be clearly noted in
the investigation report and analysis.
2
(e) Testing The testing of existing anchorage systems must
be made to determine an average capacity where these anchors are to
be used in the analysis of the building's current resistance to
lateral forces. The testing of existing URM walls to determine the
allowable bed -joint shear is required for all buildings.
(1) Existing Wall Anchors in URM Walls. Five percent of
the existing rod anchors shall be tested in pullout by an approved
testing laboratory. The minimum tested quantity shall be four per
floor or roof level with two tests where framing is perpendicular to
the wall and two where framing is parallel to the wall.
The test apparatus shall be supported on the masonry wall at a
minimum distance of the wall thickness from the anchor tested.
Where due to obstructions this is not possible, details of the
condition encountered and the alternate method used must be included
in the test report, with calibration adjustment for conditions where
the reaction of the test apparatus contributes to the tension value
of the anchor. The rod anchor shall be given a preload of 300
pounds prior to establishing a datum for recording elongation. The
tension load reported shall be recorded at 1/8 inch relative
movement of the anchor to the adjacent masonry wall surface.
(2) In -Place Shear Test of Brick Masonry. The bed joints
of the outer wythe of the masonry shall be tested in shear by
laterally displacing a single brick relative to the adjacent bricks
in that wythe. The opposite head joint of the brick to be tested
shall be removed and cleaned prior to testing. Steel bearing plates
of the full dimension of the brick shall be inserted at each end of
the test jack. The bearing plates shall not contact the mortar
joints. The shear stress shall be based on the gross area of both
bed joints and shall be that at which movement of the adjacent brick
is first observed.
The minimum quality mortar in 80 percent of the shear tests
shall not be less than the total of 30 psi when reduced to an
equivalent zero axial stress. If the larger height - to- thickness
ratios allowed by footnotes #5 and #6 of Table A -2 are to be
utilized in the analysis, all shear tests taken at the top story
must be included in the 80 percent of the shear tests used to
determine the minimum mortar shear strength.
The minimum quantity of tests shall be as follows: At each
story not less than two per wall line or line of wall elements
providing a common line of resistance to lateral forces, with not
less than one per 1500 square feet of wall surface and not less than
a total of eight per building. In single story buildings the wall
above the lintel beam at an open storefront need not be tested.
The exact test locations shall be determined by the engineer
responsible for the investigation and noted on the documents
submitted to the Town. The tests should be conducted at least two
brick courses above or below the bond course and be distributed
vertically to include a variety of dead load surcharge conditions.
Test locations shall be representative of the mortar conditions
throughout the entire building, taking into account variations in
workmanship, variations in weathering of exterior surfaces and
variations of interior surfaces due to deterioration caused by leaks
and condensation of water and /or by other deleterious substances
contained within the building.
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STANDARDS FOR THE ANALYSIS AND EVALUATION OF
UNREINFORCED MASONRY BEARING WALL BUILDINGS
(a) Structural Analysis Procedures
(1) The total seismic forces should be computed in
accordance with the following equation: V = ZIKCSW
WHERE: The value of RCS need not exceed .100 for one story
buildings with an occupant load of less than 100; and need not
exceed .133 for buildings over one story above grade or those one
story buildings with 100 or more occupants.
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 (UBC).
(2) Parts or portions of the building shall be analyzed
for lateral loads in accordance with Chapter 23 of the 1985 UBC but
not less that the value from the following equation: Fp = ICpSWp
WHERE: The product of IS need not exceed 1.0.
The value of Cp shall be as set forth in Table 23 -1 of
the 1985 UBC.
The value of Wp shall be as defined in the 1985 UBC.
Exception: URM walls may be analyzed as indicated in Section
(b) below.
(3) The structural elements of the building required to
be analyzed shall include the following:
Wall height -to- thickness ratio and in -plane shear forces.
Tension bolts (in bending) if used to resist lateral forces.
Parapets for out -of -plane loading.
Diaphragm stress and diaphragm chords at floors and roof.
(4) Anchorage and interconnection of all parts, portions
and elements of the structure resisting lateral forces shall be
analyzed in accordance with the 1985 UBC and the formula in
Subsection (2) above.
A complete and continuous load path from every part or portion
of the structure to the foundation shall be shown to exist for the
required lateral forces. All parts, portions and elements of the
structural systems shall be shown to be interconnected by an
adequate positive means.
(5) Except as modified herein, the lateral analysis of
the building shall be in accordance with the analysis specified in
the 1985 UBC.
Stresses in existing materials and construction utilized to
transfer seismic forces shall conform to either those permitted by
the 1985 UBC or those permitted for types of materials and
configurations specified in Table A -3 or those described in Section
(b) below. When calculating shear of diagonal tension stresses due
to seismic forces, existing masonry shear walls may be allowed to
resist 1.0 times the required forces in lieu of the 1.5 factor
required by the 1985 UBC.
1.1
(6) Masonry walls shall be anchorea to all floors and
roof to resist a minimum of 200 pounds per linear foot acting normal
to the wall at the level of the floor of roof or must be considered
inadequate. No allowable tension stress will be permitted in URM
walls. URM walls not capable of resisting the required design
forces specified in this section shall be deemed inadequate.
In addition to seismic forces, URM walls shall be analyzed as
specified in Chapter 24 of the 1985 UBC to withstand all vertical
loads.
Exception: URM Walls which carry no design loads other than
their own weight may be considered veneer if they
adequately anchored to elements which are not part
of the existing lateral force resisting system. See
section (d) 5 under Procedures for Investigation to
determine if existing walls,must be considered as
veneer.
(7) When stresses in existing lateral force resisting
elements are due to a combination of dead and live plus seismic
loads, the allowable working stress specified in the 1985 UBC may
increased by 100 percent. However, no increase will be permitted in
the stresses allowed in Section (b) below and the stresses in
members due to only seismic and dead loads shall not exceed the
values permitted in the 1985 UBC. In addition, the calculated
tensile fiber stress due to seismic forces may be reduced by the
full direct stress due to vertical dead loads.
(b) Materials of Construction Standards
(1) Unreinforced masonry walls analyzed in accordance
with this section may provide support for roof and floor
construction and resistance to lateral loads under the conditions
set forth below.
The bonding of such walls shall conform to those specified in
Section (d) 5 of the Procedures for Investigation.
Tension stresses due to seismic forces acting normal to the
wall may be neglected if the wall does not exceed the height -to
thickness ratio and the allowable in -plane shear stresses due to
seismic loads set forth in Tables A -2 and A -4 respectively.
If the wall height -to- thickness ratio exceeds the specified
limits, the wall will be considered inadequate unless braced by
vertical members designed to satisfy the requirements of the 1985
UBC. 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 that comply with the requirements of Section (a) 2
of the analysis procedure if the deflection at design loads is not
less than one - quarter nor more than one -third of the wall thickness
in the story under consideration.
Any existing or new vertical bracing used for this purpose
shall be attached to floor and roof construction independently of
existing wall anchors and the horizontal spacing of the members
shall not exceed one -half the unsupported height of the wall or ten
feet, whichever is greater.
E
(2) Minimum Acceptable Quality of Existing URM Walls. 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 Section (e) 2 of the Procedures for
Investigation. All masonry used to resist seismic forces shall be
undamaged by shear failure cracking and be of a quality not less
than the minimum standards established or shall be considered
inadequate.
Pointing of all masonry wall joints may be performed prior to
the testing if joints are raked and cleaned to remove loose and
deteriorated mortar. Mortar pointing shall be Type S or N, except
masonry cements shall not be used. All preparation and pointing
shall be done under the continuous inspection of a special inspector
whose reports shall be included in the testing report.
The design seismic in -plane shear stresses shall be related to
test results in accordance with Table A -4. Intermediate values
between 5 and 10 psi may be interpolated.
Compression stresses for unreinforced masonry having a minimum
design shear value of 3 psi shall not exceed 100 psi and design
tension values shall not be permitted.
(3) Existing Roof, Floors, and Walls. Existing undamaged
materials, including wood shear walls may be analyzed as part of the
lateral load resisting system, provided that the stresses in these
materials do not exceed the values shown in Table A -3. New plywood
shear walls designed in accordance with the 1985 UBC may be
recommended to strengthen portions of the existing seismic resisting
system.
Diaphragm chord stresses of horizontal diaphragms shall be
developed in existing materials or be considered inadequate.
(4) Minimum URM Wall Anchorage. All URM walls shall be.
anchored at both floors and roof by existing rod anchors at a
maximum spacing of six feet and be secured to the joists or rafters
to develop the required forces. At the building corners at roof and
floor levels combination shear and tension anchors shall be located
not more than two feet horizontally from the inside corners of the
wall. Testing of existing rod anchors shall be conducted according
to Section (e) 1 of the Procedures for Investigation. Walls without
anchors having the necessary locations, spacing or capacity will be
considered inadequate.
(5) Minimum vertical Support. Where trusses or beams
other than rafters or joists and beams supporting walls above open
storefronts are supported on URM piers, these piers must be
evaluated and shown to provide adequate vertical support during
seismic loading or shall be independently supported by a vertical
element other than the URM wall pier.
(6) Minimum Parapet Bracing. Parapets and exterior wall
appendages not capable of resisting the forces specified in Section
(a) shall be considered hazardous. The maximum height of an
unbraced URM wall parapet above the lower of either the level of
existing adequate tension anchors or the roof sheathing, shall not
exceed one and one -half times the thickness of the parapet wall.
(a
(c) Design Check for Compatibility of Roof Diaphragm Stiffness
to the Out -of -Plane Stability of URM Walls.
(1) General. The requirements of this section are in
addition to the other analysis requirements of Section (a). This
section contains a procedure for the evaluation of the out -of -plane
stability of unreinforced masonry walls anchored to wood diaphragms.
The relative stiffness and strength of a diaphragm governs the
amount of amplification of seismic ground motion by the diaphragm,
and therefore, a diaphragm stiffness and strength related check of
the out -of -plane stability of URM walls must be performed.
(2) Definitions. The following definitions are
applicable to this section:
CROSS WALL is a wood framed wall having,a height -to- length
ratio complying with 1985 UBC Section 4713(d) or Table 25 -I and is
sheathed with any of the materials described in Table A -1. 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 under consideration
DEMAND CAPACITY RATIO (DCR) is a ratio where:
Demand equals lateral forces due to 33 percent of the weight of the
diaphragm and the tributary weight of walls and other elements
anchored to the diaphragm.
Capacity equals the diaphragm's total shear strength in the
direction under consideration as determined using the values in
Table A -1.
D = the depth of the diaphragm, in feet, measured perpendicular
to the diaphragm span.
h/t = the height -to- thickness ratio 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
Vc = the total shear capacity of cross walls in the direction
of analysis immediately below the diaphragm level being
investigated as determined by using Table A -1.
vu = Maximum shear strength in pound per foot for a diaphragm
sheathed with any of the materials given in Table A -1.
Wd = total dead load of the diaphragm plus the tributary weight
of the walls anchored to the diaphragm, the tributary
ceiling and partitions, and the weight of any other
permanent building elements at the diaphragm level under
consideration.
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(3) Design Check Procedure. The demand - capacity ratio
(DCR) shall be calculated by the following equations:
Buildings without crosswalls
0.33 Wd
DCR = -- - - - - --
2 vu D
Buildings with crosswalls
0.33 Wd
DCR = ----- - - - - --
2 vu D + Vc
Diaphragm Deflection. The calculated DCR shall be the left of
the curve in Figure A -5. Where the calculated DCR is outside (to
the right) of the curve, the diaphragm's deflection limits are
exceeded and cross walls are needed to reduce the deflection.
URM Wall Out -of -Plane Stability. The DCR shall be calculated
discounting any existing cross walls. If this DCR value
corresponding to the diaphragm span is to the right of the curve in
Figure A -5, 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 A -2.
TABLE A -1
ALLOWABLE VALUES FOR EXISTING WALLS AND DIAPHRAGMS
ONLY FOR DETERMINATION OF THE DIAPHRAGM DEMAND / CAPACITY RATIO
1. Horizontal Diaphragms 1
a. Roofs with straight sheathing
and roofing applied directly
to the sheathing.
b. Roofs with diagonal sheathing
and roofing applied directly
to the sheathing.
2. Crosswalls 1
a. Plaster on wood or metal
lath
b. Plaster on gypsum lath
c. Gypsum wallboard unblocked
d. Gypsum wallboard edges blocked
Footnotes:
100 PLF for seismic shear
250 PLF for seismic shear
200 PLF per side for
seismic shear
175 PLF per side for
seismic shear
75 PLF per side for
seismic shear
125 PLF per side for
seismic shear
1. Materials must be undamaged and in good condition.
M
TABLE A -2
ALLOWABLE VALUE OF HEIGHT -TO- THICKNESS (H /T) RATIO
OF URM WALLS WITH MINIMUM QUALITY MORTAR 1 , ?
------------------ - - - - --
One Story Building Walls
First Story Walls of
Multi -Story Buildings
Walls in Top Story of .
Multi -Story Buildings
All Other Walls
------------------ - - - - --
Footnotes:
Buildings with All Other
Complying Crosswalls s Buildings
---------------------------------------
13 - 16 4, 5, 6 ; 13
16 i 15
I
9- 14 4, 5 6 I 9
16 i 13
--------------------------------- - - - - --
1. Minimum quality mortar shall be determined by testing described
in Section (e) 2 of the Procedures for Investigation and shall
include all top story tests in the 80 percent of tests used if
the higher ratio values permitted in footnotes 5 and 6 are used.
2. See section (c) for determination of the demand capacity ratio
values to be used in conjunction with Figure A -5 to determine if
the building can qualify as a building containing crosswalls.
3. Qualifying crosswalls are defined as interior walls of masonry
or wood frame construction with surface finish of wood lath and
plaster, 1/2 inch thick gypsum board, or solid horizontal wood
sheathing. They may not exceed 40 feet horizontal separation,
must be continuous through all stories and have a minimum length
of 1 -1/2 times the story height.
4. The minimum mortar strengths required in footnotes # 5 and 6
shall be the test shear strength reduced by the effect of axial
stress in the wall at the point of the test.
5. The larger height -to- thickness ratio may be used where mortar
shear tests establish a minimum mortar shear strength of not
less than 100 psi or where the tested mortar shear strength is
not less than 60 psi and a visual examination of the vertical
wythe- to -wythe (collar) joint indicates not less than 50 percent
mortar coverage.
6. Where a visual examination of the collar joint indicates not
less than 50 percent mortar coverage and the minimum mortar
shear strength is greater than 30 psi but not less than 60 psi,
the allowable h/t ratio may be determined by linear
interpolation between the larger and smaller values given in
direct proportion to the mortar shear strength.
G
TABLE A -3
ALLOWABLE STRESS VALUES FOR EXISTING MATERIALS
FOUND TO BE UNDAMAGED AND IN GOOD CONDITION
1. Horizontal Diaphragms
a. Roofs with straight sheathing
with the roof covering applied
directly to the sheathing.
b. Roofs with diagonal sheathing
with the roof covering applied
directly to the sheathing
100 PLF for seismic shear
400 for seismic shear
C. Floors with straight tongue
and groove sheathing
d. Floors with straight sheathing
and finished wood flooring
e. Floors with diagonal sheathing
and finished wood flooring
f. Floors or roofs with straight
sheathing and plaster applied
to the joists or rafters below
150 PLF for seismic shear
300 PLF for seismic shear
450 PLF for seismic shear
Add 50 PLF to the allowable
values for items la and lc.
2. Shear Walls
a. Wood stud walls with lath and
plaster in undamaged condition
100 PLF each side for
seismic shear
3. Plain Concrete Footings
4. Douglas Fir Wood i
5. Reinforcing Steel 1
6. Structural Steel i
Footnotes:
V c = 1500 PSI unless
otherwise shown by tests
Same as 1985 UBC values for
No. 1 Douglas Fir
V t = 18,000 PSI maximum 1
V t = 20,000 PSI maximum 1
1. Stresses may be increased for combination of loads as specified
in Section (a) 7 of the Standards for Analysis and Evaluation.
i0
TABLE A -4
ALLOWABLE SHEAR STRESS FOR TESTED URM WALLS
80 Percent of Test Results Allowable In -Plane Shear
in PSI Not Less Than: in PSI Based on Gross Area 1
-------------------------------------------------------------- - - - - --
30 + Axial Stress
40 + Axial Stress
50 + Axial Stress
100 + Axial Stress or more
-------------------- - - - - --
3.0
4.0
5.0
10.0 (maximum)
------- ------- - - - - --
Footnotes:
1. The allowable shear stress may be increased by addition of 10
percent of the axial stress due to the weight of the wall
directly above.
540
480
420
360
f-
W _
U.
= 300
2
6
d
N
Q � 240
d
Q
180
60
120
`l
O1 REGION OF DEMAND /CAPACITY
RATIOS WHERE CROSSWALLS
MAY BE USED TO INCREASE
H/T RATIOS
O2 REGION OF DEMAND /CAPACITY
RATIOS WHERE H/T RATIOS OF
"WITH CROSSWALLS" MAY BE
USED
O3 REGION OF OEMANO /CAPACITY
RATIOS WHERE H/T RATIOS OF
"ALL OTHER BUILDINGS" SHALL
BE USED
7
O
0 1 2 3 4 5 6
DEMAND - CAPACITY RATIO O.33•WD/(2y OR 0. W /(2v + sv
ACCEPTABLE SPAN FOR DIAPHRAGMS
(BASED ON DISPLACEMENT CONTROL CONCEPTS)
A -5
FIGURE 19
12
TOWN OF LOS GATOS AMENDMENTS
TO THE UNIFORM CODE FOR BUILDING CONSERVATION
APPENDIX CHAPTER 1
EARTHQUAKE HAZARD REDUCTION IN EXISTING
UNREINFORCED MASONRY BUILDINGS
Section A102 is hereby amended to read:
The requirements of this chapter shall apply to all damaged
buildings containing unreinforced masonry bearing walls and those
undamaged buildings with unreinforced masonry walls which do not
meet the requirements of this chapter for seismic resistance.
Exception: This chapter shall not apply to Group M. or Group R,
Division 3 occupancies, Group R, Division 3 occupancies with less
than five dwelling units used solely for residential purposes, nor
to any undamaged building less than 900 square feet and containing
less than five occupants.
Subsection (a) of Section A105 is hereby amended to read:
General. A historic building may comply with the special
provisions of this chapter and the provisions of the State Historic
Building Code.
The second paragraph of Subsection (a) of Section A106 is hereby
amended to read:
The value of RCS 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.
Subsection (b) of Section A106 is hereby amended to read:
(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 Co shall be in accordance with Table 23 -1
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.
Paragraph 1 of subsection (f) of Section A106 is hereby amended to
read:
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 Al -F
Paragraph 3 of subsection (g) of Section A106 is hereby amended by
adding the following paragraph after the second exception:
Substantial changes in wall thickness or stiffness shall be
considered in the analysis for out -of -plane and in -plane wall
stability, and the wall shall be restrained against out -of -plane
instability lay 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.
Subsection (b) of Section A107 is hereby amended to read:
(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 hall 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 full - length 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 Al -F and the in -plane shear stresses due to
seismic loads set forth in Table Al -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 h 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.
Paragraph 2 of Subsection (b) of Section A107 is hereby renumbered
to become paragraph 3 and a new Paragraph 2 is added to read:
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
ever 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
Director of Building Services 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 Director of Building Services.
Paragraph 1 of subsection (d) of Section A107 is hereby amended to
read:
1. General provisions. All unreinforced masonry walls utilized
to carry vertical loads and seismic forces parallel and
perpendicular to he 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 or by testing eight
3
inch diameter cores. Alternate testing methods may be approved by
the Director of Building Services upon submission of adequate
evidence to indicate its equivalence The vertical wall 'off int
between wythes collar j oint shall be inspected at each test
location after the in -place shear tests, and an estimate of the
percentage of wvthe 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
Director of Building Services 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
Director of Building Services for approval as part of the structural
analysis.
Paragraph 2 of Subsection (d) of Section A107 is hereby amended to
read:
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 elements 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 bJ
the deleterious effects of other substances contained within the
building. Where the higher h/t ratios allowed in footnotes 4 and 5
of Table Al -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.
Paragraph 1 of Subsection (b) of Section A108 is hereby amended to
read:
(b) Construction Details. The following requirements with
appropriate construction details shall be made a part of the
0
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 Al -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 embeded 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 and 6 in table no. Al -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).
Paragraph 3 of Subsection (b) of Section A108 is hereby amended to
read:
3. Where trusses and beams other than rafters or joists are
supported on masonry independent secondary columns shall be
installed to support vertical loads.
Paragraph 4 of Subsection (b) of Section A108 is hereby amended to
read:
4. Parapets 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
Paragraph 5 of Subsection (b) of Section A108 is hereby amended to
read:
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 Director of Building Services setting forth the
portion of work inspected.
Paragraph 4 of Subsection (c) of Section A108 is hereby amended to
read:
4. Accurately dimensioned floor plans and masonry wall
elevations showing dimensioned opening, piers, wall thickness and
heights, veneer locations and existing anchorages
Paragraph 6 of Subsection (c) of Section A108 is hereby amended to
read:
6. The type of interior wall surfaces and ceilings and if
reinstalling or anchoring of existing plaster is necessary.
Paragraph 8 of Subsection (c) of Section A108 is hereby added to
read:
8. The location of all in -place shear tests or core tests,
shall be shown on the floor plans and building wall elevations.
A new Section A109 is hereby added to Chapter 1.
Design Check for Compatibility of Roof Diaphragm Stiffness to
Unreinforced Masonry Wall Out -of -Plane Stability.
Sec. A108 (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) Definitions. The following definitions are applicable to
this section.
Cross Wall. 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 Al -J or Table Al -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.
6
Demand Capacity Ratio (DCR). A ratio of the following:
1. Demand equals the lateral forces due to 33 percent of the
weight of the diaphragm and the tributary weight of the walls and
other elements anchored to the diaphragm.
2. Capacity equals the diaphragm total shear strength in the
direction under consideration as determined using the values in
Tables No. Al -J or Table Al -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.
Al -J and Al -K.
vu = maximum shear strength in pounds per foot for a
diaphragm sheathed with any of the materials given in
tables No. Al -J and Al -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 / 2 vu D For building without cross walls
or
DCR = 0.33 Wd /2 vu D + Vc For building with cross walls
2. Diaphragm Deflection. The calculated DCR shall be to the
left of the curve in Figure No. Al -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. Al -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. Al -F.
Table Al -F of Chapter 1 is hereby amended to read:
TABLE NO Al -F
ALLOWABLE VALUE OF HEIGHT - THICKNESS (h /t) RATIO
OF UNREINFORCED MASONRY WALLS WITH MINIMUM
QUALITY MORTAR 1 2
--------------------------------------------------------------------
I BUILDINGS WITH ALL OTHER
I COMPLYING CROSS WALLS BUILDINGS
I -------- ----------------------------------
One Story Building Walls { 13 - 16 3 4 a I 13
First Story of
Multi -Story Buildings
Walls in the Top Story
of Multi -Story Buildings
All Other Walls
16
9` 14 3 4 e
16
15
7
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.
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 op int 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 than 60 psi and a visual
examination of the vertical wythe- to -wythe wall 'off int collar
joint) indicates not less than 50 percent mortar coverage.
° Where a visual examination of the collar 'o3 int indicates not less
than 50 percent mortar coverage and the minimum mortar shear
strenath 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 strenath.
Portions of Table No. Al -H are hereby modified to read:
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 dry -pack or
non - shrink grout around the
circumference of the bolt
[ +�
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.
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. 1 z 3
(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. 1 2 3
600 lbs. per bolt for tension
see Item 3 (Shear Bolts) for
shear values.
1200 lbs. per bolt or dowel
for tension See Item 3 for
shear values.
(c) Through bolt with bearing plate See Item 4 (Tension Bolts)
for tension per Item 4. for tension values See
Combined with minimum 8 inch Item 3 for shear values.
grouted section for shear per
Item 3.
The following footnotes are hereby added to Table No. Al -H
3 Drilling for bolts and dowels shall be done with an electric
rotary drill. Impact tools hall 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.
New Tables No. Al -J and No. Al -K are hereby added to Chapter 1
to read:
TABLE NO. Al -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 Materials 1
----------------------------------
1. Horizontal Diaphragms
a. Roofs with straight sheathing
and roofing applied directly
to the sheathing.
Allowable Values
100 lbs. per foot for
seismic shear.
b. Roofs with diagonal sheathing
and roofing applied directly
to the sheathing
2. Cross Walls 2
a. Plaster on wood or metal lath.
250 lbs. per foot for
seismic shear.
Per Side:
200 lbs per foot for
seismic shear.
u
b. Plaster on gypsum lath. 175 lbs. per foot for
seismic shear.
c. Gypsum wall board unblocked 75 lbs. per foot for
edges. seismic shear.
d. Gypsum wall board blocked 125 lbs. per foot for
edges. seismic shear.
-------------------------------------------------------------------
i 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. Al -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 Materials t
------------------------------------
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.
Allowable Values
225 lbs. per foot for
seismic shear.
2. Cross Walls 2
a. Plywood sheathing applied directly
over existing wood studs. No 1.33 times the values
value shall be given to plywood specified in Table 25 -K
applied over existing plaster or of the 1985 UBC.
wood sheathing.
b. Drywall or plaster applied 100 percent of the values
directly over existing wood studs 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.
A new Figure Al -L is hereby added to Chapter 1 to read:
H
y
s
$40
480
420
0
360
f „
W
lL
= 300
a
a
H
240
4
180
OI REGION OF DEMAND /CAPACITY
RATIOS WHERE CROSSWALLS
MAY BE USED TO INCREASE
H/T RATIOS
02 REGION OF DEMANO /CAPACITY
RATIOS WHERE H/T RATIOS OF
"WITH CROSSWALLS" MAY BE
USED
Q3 REGION OF DEMAND /CAPACITY
RATIOS WHERE H/T RATIOS OF
"ALL OTHER BUILDINGS" SHALL
BE USED
120 `
60
0
i
1
IN
0 1 2 3 4 5 6
DEMAND-CAPACITY RATIO, 0.33•WD/(2v OR 0.33 W /(2Y + LY,)
ACCEPTABLE SPAN FOR DIAPHRAGMS
(BASED ON DISPLACEMENT CONTROL CONCEPTS)
FIGURE VP
It is the policy of the Town Council to; repair damaged structures rather than
demolish.
It is the intent of the Los Gatos Building Restoration Program:.
a. To provide guidelines for the. repair or reconstruction of buildings damaged
in the earthquake of October 17 1989, or.,from the; aftershocks after that
date.
b. To create a: development process. -that will provide for the.£apid repair of
damaged buildings within adopted code- .limitations•. fl 4 ,:,
c.._ To encourage the restoration: and; reconstruction of damaged: buildings to
insure-the preservation of the exterior of buildings as they existed before
the - ,earthquake.:- (See guidelines > for, repair,, reconstruction and now
construction: below.)_-,'_ -
The Town has developed the following. .procedures,.for the repair or. reconstruction
of earthquake damaged - buildings - .- There are three categories of- permits -for such
work: repair, reconstruction as,existing earthquake, and new
construction.
I. REPAIR Repair of, structure to its- exiating, status. before., quake
A. All Town fee* waived,
B. Structural Guidelines:
1. Unreinforced masonry. structural - :repairs.. the.Unifom -KCode for
Buildin& Conservation will be the standard.
2. _ Other building types - need to satisfy current building code
requirements except lateral seismic. design may, be as. low as 75
= percent of the requirement of the current code
C. Will require building, permits. only: N¢: public- review or hearing
process.
D. Fireplace repairs: the fireplace must meet current criteria for
seismic design.
Handouts showing these requirements are available at the Planning,
Building, Engineering departments counter on the lower level of the
Town Civic Center.
F/U IM 2
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II. RECONSTRUCTION - Replacement of an existing structure, by a new structure
with the floor area, setbacks, and exterior identical to previous structure.
A. All Town fees waived.
B. Will require Restoration Committee review as well as building permits.
No public hearing process. The Restoration Committee will consist of
the following members or their designee:
■ Director of Building Services -
■ Planning Director
■ Town Engineer
■ Central Fire District Chief
■ Police Chief
■ Director of Parks, Forestry and Maintenance Services
■ Historical Restoration Consultant hired by the Town
C. The new structure must meet all current building code requirements.
All demolition requires a Town approved demolition permit prior to
commencement. Removal of any portion of a structure is a demolition.
D. Buildings not historically designated shall be rebuilt in an
architectural style consistent with the historical flavor of downtown
as identified by a Town retained professional consultant, the
Restoration Committee and approved by the Town Council. The approved
styles of architecture and choice of exterior materials will be
identified by a Town retained professional architectural consultant
after recommendation from the Historic Preservation Committee and
approved by the -Town Council.
E. Town designated historic buildings shall be rebuilt to their original
identical construction with seismic safety improvements added.
F. Interior spaces may be rearranged or reorganized as desired, under
repair or reconstruction, as long as total floor area is not increased.
G. Demolition application may require structural report. Eligibility for
the repair and reconstruction options is only possible if the
demolition, if any, was in accordance with an approved demolition
permit.
H. Off -site improvements not required.
The final decisions regarding reconstruction are determined jointly
by the Director of Building Services and the Planning Director subject
to appeal to the Town Council.
III. NEW CONSTRUCTION - Replacement of existing structure with �new structure
which is identical to the previous structure to be removed.
A. All fees must be paid.
B. Normal review- process; Development Review Committee, Planning,
Commission, Town Council, must meet all state regulation and Town codes
and ordinances and all public noticing requirements.
IV.
A. Illegal or unlawful construction or- unlawful- occupancy will not be
allowed to be reestablished.
B. The current grading moratorium has not been amended.
PL05 \2&rth.gk
October 27, 1989
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