HomeMy WebLinkAboutCC Resolution 8171 (Unreinforced Masonry Building Program)RESOLUTION NO. 8171
A RESOLUTION OF THE CITY COUNCIL OF THE
CITY OF SAN RAFAEL ESTABLISHING ANALYSIS
AND DESIGN REQUIREMENTS FOR USE WITH THE
CITY'S UNREINFORCED MASONRY BUILDING
MITIGATION PROGRAM
WHEREAS, the San Rafael General Plan 2000 has a seismic
safety element which calls for the City to implement measures to
encourage the rehabilitation or elimination of structures susceptible
to collapse or failure in an earthquake (Seismic Safety Policy 5-12);
and
WHEREAS, State law (SB 547) requires that the City Council
adopt a mitigation program pertaining to existing unreinforced masonry
buildings, and
WHEREAS, the City Council has adopted a mitigation program
pertaining to existing unreinforced masonry buildings, and
WHEREAS, that program requires the City Council to adopt
a resolution establishing analysis and design requirements for
implementation of the City's program, and
WHEREAS, the attached Exhibit "A" provides analysis and
design requirements for unreinforced masonry buildings.
NOW, THEREFORE, BE IT RESOLVED BY THE City Council of
the City of San Rafael, that in view of the foregoing findings, the
attached Exhibit "A", establishing requirements for the analysis
and design of repairs to unreinforced masonry buildings, is hereby
approved.
I, JEANNE M. LEONCINI, Clerk of the City of San Rafael,
California, hereby certify that the foregoing resolution was duly
and regularly introduced and adopted at a regular meeting of the
Council of said City held on the 7th day of May, 1990, by the following
vote, to wit:
AYES: COUNCILMEMBERS: Boro, Breiner, Thayer & Mayor Mulryan
NOES: COUNCILMEMBERS: None
ABSENT: COUNCILMEMBERS: Shippey
JEA M. LEONCINI; City Clerk
E X H I B I T "A"
UNREINFORCED MASONRY BUILDING MITIGATION
PROGRAM ANALYSIS AND DESIGN REQUIREMENTS
SECTION I GENERAL REQUIREMENTS
a) General. Every structure within the scope of Chapter 12.40
of the Municipal Code shall have a seismic resisting system conform-
ing with Section 2303(b) of the Building Code, except as modified by
these requirements.
b) Alterations and Repairs. Alterations and repairs required
to meet the provisions of these requirements shall comply with all
other applicable requirements of the Building Code unless specifi-
cally provided for in these requirements.
c) Requirements for Plans. The following construction informa-
tion shall be included in the plans required by this Chapter:
1. Accurately dimensioned floor and roof plans showing
existing walls and the size and spacing of floor and roof framing
members and sheathing materials. The plans shall indicate all
existing and new crosswalls and their materials of construction.
The location of the crosswalls and their openings shall be fully
dimensioned or drawn to scale on the plans.
2. Accurately dimensioned wall elevations showing openings
piers, thicknesses, and heights, wall shear test locations, cracks
or damaged portions requiring repairs. The general condition of the
mortar joints and if and where the joints require pointing. Where the
exterior face is veneer, the type of veneer, its thickness and its
bonding and/or ties to the structural wall masonry shall also be re-
ported.
3. The type of interior wall and ceiling surfaces.
4. The extent and type of existing wall anchorage to
floors and roof when utilized in the design.
5. The extent and type of parapet corrections which were
previously performed, if any.
6. Repair details, if any, of cracked or damaged unrein-
forced masonry walls required to resist forces specified in this
Chapter.
7. All other plans, sections, and details necessary to
delineate required retrofit construction including those items in
Section IV.
1.
SECTION II ALLOWABLE DESIGN VALUES
a) Allowable Values. 1. Allowable values for existing materials
are given in Table C and for new materials in Table D. The one-third
increase in allowable values is not allowed for values in these tables.
2. Allowable values not specified in this Chapter shall
be as specified elsewhere in the Building Code. Allowable values
not specified in this Chapter for dead load plus seismic load may
be increased 33 percent. Allowable values not specified in this
Chapter for existing building elements with a combination of
dead load plus floor live load plus seismic load may be increased
70 percent.
3. Minimum Acceptable Quality of Existing Unreinforced
Masonry Walls. All unreinforced masonry walls utilized to carry
vertical loads and seismic forces parallel and perpendicular to the
wall plane shall be investigated by the licensed engineer or architect
analyzing the building to determine their structural capacity.
The engineer or architect shall require on site testing of existing
materials where he feels such testing is necessary to analyze the
building. Such testing may consist of in-place shear tests, core
tests, shear bolt testing, or other test methods approved by the
City.
2.
SECTION III ANALYSIS AND DESIGN
(a) General. Except as modified herein, the analysis and design
relating to the structural alteration of existing buildings shall
be in accordance with the Building Code.
(b) Selection of Procedure. Buildings shall be analyzed by
the General Procedure of Section III (c) which is based on
Chapter 23 of the Building Code or, when applicable, buildings may
be analyzed by the Special Procedure of subsection III (d).
(c) General Procedure.
1. Minimum Design Lateral Forces. Buildings shall be
analyzed to resist minimum lateral forces assumed to act
noncurrently in the direction of each of the main axes of the
structure in accordance with the following:
V = 0.33ZW..................................(46-1)
2. Lateral Forces on Elements of Structures. Parts or
portions of structures shall be analyzed as required in Chapter 23
of the Building Code.
Exceptions: i. Unreinforced masonry walls for which
height to thickness ratios do not exceed ratios set
forth in Table B need not be analyzed for out -of -
plane loading. Unreinforced masonry walls which exceed
the allowable h/t ratios of Table B shall be braced
according to Section IV (e).
ii. Parapets complying with Section IV (f) need not be
analyzed for out -of -plane loading.
3. Shear Walls (In -Plane Loading). Shear walls shall
comply with subsection III (e).
(d) Special Procedure. 1. Limits for the Application of
Subsection III (d) The Special Procedure of this subsection
may only be applied to buildings with the following
characteristics:
A. Flexible diaphragms at all levels above the base of
structure.
B. A maximum of 6 stories above the base of the
building.
3.
C. The vertical elements of the lateral force
resisting system shall consist predominantly of masonry
or concrete shear walls or steel braced frames or
special moment resisting frames (see Section 2312 of
the Building Code) each with a maximum overall height -
to -length ratio of 1-1/2 to 1.
D. The lateral force resisting system shall be regular
as defined in the Building Code. Except for a single
story building with an open front, a minimum of two
lines of vertical lateral force -resisting elements
shall be parallel to each axis of the building.
2. Lateral Forces on Elements of Structures. With the
exception of the diaphragm provisions in subsection III (d),
elements of structures shall comply with subsection III (c)2.
3. Crosswalls. Crosswalls shall meet the requirements of
this subsection.
A. Crosswall Definition. A crosswall is a wood -framed
wall sheathed with any of the materials described in Tables
or D. _ Spacing of crosswalls shall not exceed 40 feet on
center measured perpendicular to the direction of consideration,
and shall be placed in each story of the building. Crosswalls
shall extend the full story height between diaphragms.
Exception: 1. Crosswalls need not be provided at all
levels in accordance with subsection
III (d) 4B (iv) .
2. Existing crosswalls need not be continuous below
a wood diaphragm at/or within four feet of grade
provided:
(i) Shear connections and anchorage requirements
Section III (d)7 are satisfied at all edges of
the diaphragm.
(ii) Crosswalls with total shear capacity of
.071:Wd interconnect the diaphragm to the
foundation.
(iii) The demand/capacity ratio of the diaphragm
between the crosswalls that are continuous to their
foundations shall be calculated as:
DCR = [0.33Wd + Vca)/2vuD....... (46-2)
and DCR shall not exceed 2.5.
4.
B. Crosswall Shear Capacity. Within any 40 feet measured
along the span of the diaphragm, the sum of the crosswall shear
capacities shall be at least 30 percent of the diaphragm shear
capacity of the strongest diaphragm at or above the level under
consideration.
C. Existing Crosswalls. Existing crosswalls shall have a
length to height ratio between openings of not less than 1.5.
Existing crosswall connections to diaphragms need not be
investigated as long as the crosswall extends to the framing of
the diaphragm above and below.
D. New Crosswalls. New crosswall connections to the
diaphragm shall develop the crosswall shear capacity. New
Crosswalls shall have the capacity to resist an overturning moment
equal to the crosswall shear capacity times the story height.
Crosswall overturning moments need not be cumulative over more
than two stories.
E. Other Crosswall Systems. Other systems such as
special moment resisting frames may be used as crosswalls provided
that the yield story drift does not exceed one inch in any story.
4. Wood Diaphragms. A. Acceptable Diaphragm Span. A
diaphragm is acceptable if the point (L,DCR) on Figure 1,
falls within Regions 1, 2, or 3.
B. Demand -Capacity Ratios. Demand -Capacity Ratios shall
be calculated for the diaphragm according to the following
formulas:
(i) For a diaphragm without qualifying crosswalls at
levels immediately above or below:
DCR = O.83ZWd/7_vuD............. ............(46-3)
(ii) For a diaphragm in a single -story building with
qualifying crosswalls:
DCR = 0.83ZWd/(7,vuD + Vcb) ...................(46-4)
(iii) For diaphragms in a multi -story building with
qualifying crosswalls in all levels:
DCR = 0.83ZY-Wd/(7-ZvuD+Vcb)...................(46-5)
DCR shall be calculated at each level for the set of diaphragms at
and above the level under consideration.
5.
(iv) For a roof diaphragm and the diaphragm directly
below if coupled by crosswalls:
DCR = 0.83Z7,Wd/JJvuD...........................(46-6)
C. Chords. An analysis for diaphragm flexure need not
be made and chords need not be provided.
D. Collectors. An analysis shall of diaphragm
collector forces shall be made for the transfer of diaphragm
edge shears into vertical elements of the lateral force
resisting system. Collector forces may be resisted by new or
existing elements.
E. Diaphragm Openings. (i) Diaphragm forces at
corners of openings shall be investigated and shall be
developed into the diaphragm by new or existing materials.
(ii) In addition to calculating demand capacity
ratios per Section III (d)4B, the demand capacity ratio of
the portion of the diaphragm adjacent to an opening shall be
calculated using the opening dimension as the span.
(iii) Where an opening occurs in the end quarter of
the diaphragm span vud for the demand capacity.ratio
calculation shall be based on the net depth of the diaphragm.
5. Diaphragm Shear Transfer. Diaphragms shall be
connected to shear walls with connections capable of
developing a minimum force given by the lesser of the
following formulas:
V = 1/2ZCpWd.....................................(46-7)
or
V= vuD........................................(46-8)
6. Shear Walls (In Plane Loading) - Special Procedure.
A. Wall Story Force. The wall story force distributed to
a shear wall at any diaphragm level shall be the lesser value
calculated as:
(i) For buildings without crosswalls,
6.
Fwx = 0.33Z(V A+Wd/2).................. ............... (46-9)
but need not exceed
Fwx= 0.33ZWwx + vuD................................(46-10)
(ii) For buildings with crosswalls in all levels:
Fwx = 0.25Z(Wwx+Sold/2).................................(46-11)
but need not exceed
Fwx = 0.25Z(Wwx + IWd (vuD/7-jvuD) ) ....................(46-12)
and need not exceed
Fwx = 0.25ZWwx + vuD..................................(46-13)
B. Wall Story Shear. The wall story shear shall be the
sum of the wall story forces at and above the level of
consideration.
Vwx= 'FFwx............................................(46-14)
C. Shear Wall Analysis. Shear walls shall comply with
subsection III (e).
D. Moment Frames. Moment frames used in place of shear
walls shall be designed as required in Chapter 23 of the Building
Code except that the forces shall be as specified in Section
III (d)6A and the interstory drift ratio shall be limited to
0.005.
7. Out of Plane Forces - URM Walls. A. Allowable URM
Wall Height to Thickness Ratios. The provisions of Section
III (c)2 are applicable except the allowable h/t ratios given in
Table B . shall be determined from Figure 1_ as follows:
(i) In Region 1, h/t ratios for "buildings with
crosswalls" may be used if qualifying crosswalls are present in
all stories.
(ii) In Region 2, h/t ratios for "buildings with
crosswalls" may be used whether or not qualifying crosswalls are
present.
(iii) In Region 3, h/t ratios for "all other buildings"
shall be used whether or not qualifying crosswalls are present.
7.
B. Walls -with Diaphragms in Different Regions. When
diaphragms above and below the wall under consideration have DCRs
in different regions of Figure 1 the lesser h/t ratio shall
be used.
8. Buildings with Open Fronts. A building with an open
front on one side shall have crosswalls parallel to the open front
and shall be designed by the following procedure:
A. Effective Diaphragm Span, Li, .for use in Figure No. 1
shall be determined in accordance with the following formula:
Li = 2[(WW/Wd)•L + L) .............................(46-15)
B. Diaphragm Demand/capacity ratio shall be calculated as:
DCR = 0.83Z (Wd + Ww) / [ (vu D) + VC] ............... (46-16)
(e). Analysis of Vertical Elements of the Lateral Force -
Resisting System. Applicable to both General Procedure and
Special Procedure Buildings.
1. Existing URM Walls. A. Flexural Rigidity. Flexural
rigidity may be neglected in determining the rigidity of an URM
wall.
B. Shear Walls with Openings. Wall piers shall be
analyzed according to the following procedure:
(i) For any pier,
(1) The pier shear capacity shall be
calculated as:
Va = vaDt......................... ...(46-17)
(2) The pier rocking shear capacity shall be
calculated as:
Vr = 0.5PDD/H...........................(46-18)
(ii) The wall piers at any level are acceptable
if they comply with one of the following modes of
behavior:
(1) Rocking Mode. Where all piers at a level
have shear capacities capable of sustaining
rocking, i.e., the pier shear capacity is
greater than or equal to the pier rocking
shear capacity for each pier, forces in in
the wall at that level, Vwx, shall be
S.
distributed to each pier, Vp, in proportion
to PDD/H.
For each pier at that level: Va >_ Vr........ (46-19)
and for the wall at that level:
Vwx <_7-Vr.......... (46-20)
(2) Non -rocking Mode. Where at least one pier at
a level is incapable of sustaining a rocking
mode, i.e., the pier shear capacity is less than
the pier rocking shear capacity, forces in the
wall at that level, Vwx, shall be distributed to
each pier,Vp, in proportion to D/H, such that
Vwx = 7VP.
For at least one pier at that level:
Va < Vr............ (46-21)
For each pier at that level:
Vp <_ Va........... (46-22)
and
Vp <_ Vr........... (46-23)
If Vp >Vr in one or more piers, omit
such piers from the analysis and repeat the
procedure for the remaining piers or
strengthen and reanalyze the wall.
(iii) Masonry Pier Tension Stress. Unreinforced
masonry wall piers need not be analyzed for tension
stress.
C. Shear Walls Without Openings. Shear walls without
openings shall be analyzed as for walls with openings except that
Vr shall be calculated as follows:
Vr = (0.50PD + 0.25Pw)D/H ....................(46-24)
2. Plywood sheathed shear walls. Plywood sheathed shear
walls may be used to resist lateral loads for buildings with
flexible diaphragms analyzed according to provisions of Section
III (c). Plywood sheathed shear walls may not be used to share
lateral loads with other materials along the same line of
resistance.
3. Combinations of Vertical Elements. A. Lateral Force
Distribution. Lateral forces shall be distributed among the
9.
vertical resisting elements in proportion to their relative
rigidities, except that moment frames shall comply with Section
A2346(e)3B.
B. Moment Resisting Frames. A moment frame shall not be
used with a URM wall in a single line of resistance unless the
wall has piers that are capable of sustaining rocking in
accordance with III (e)1B and the frames are designed to carry
100% of the lateral forces.
10.
DETAILED SYSTEM DESIGN REQUIREMENTS
SECTION IV
( a ) General.
(b) Wall Anchorage. 1. Anchor Locations. All unreinforced
masonry walls shall be anchored at the roof and floor levels as
required in Section III (c)2. Ceilings with substantial rigidity
and abutting masonry walls shall be connected to walls with
tension bolts at a maximum anchor spacing of 6 feet. Ceiling
systems with substantial mass shall be braced at the.perimeter to
diaphragms.
2. Anchor Requirements. Anchors shall be tension bolts
through the wall as specified in Table No. D- or by an
approved equivalent at a maximum anchor spacing of 6 feet. All
existing wall anchors shall be secured to the joists to develop
the required forces. The Building Official may require testing to
verify the adequacy of the embedded ends of existing wall anchors.
3. Minimum Wall Anchorage. Anchorage of masonry walls to
each floor or roof shall resist a minimum force determined by
Section 2312(g)2 of the Building Code or 200 pounds per linear
foot, whichever is greater, acting normal to the wall at the level
of the floor or roof. Existing wall anchors, installed under
previous permits, must meet or must be upgraded to meet the
requirements of this Chapter.
4. Anchors at Corners. At the roof and all floor levels,
both shear and tension anchors shall be provided within two feet
horizontally from the inside of the corners of the walls.
5. Anchors with Limited Access. When access to the
exterior face of the masonry wall is prevented by proximity of an
existing building, wall anchors conforming to Item 5b in Table D
may be used.
(c) Collectors. Collector elements shall be provided which are
capable of transferring the seismic forces originating in other
portions of the building to the element providing the resistance
to those forces.
(d) Ties and Continuity. Ties and continuity shall conform to
Section 2312(h)2E.
(e) Wall Bracing. 1. General. Where a wall height -thickness
ratio exceeds the specified limits, the wall may be laterally
supported by vertical bracing members per Section IV (e)2 or by
reducing the wall height by bracing per Section IV (e)3.
2. Vertical Bracing Members. Vertical bracing members shall
be attached to floor and roof construction for their design loads
- .._ 1]..
independently of required wall anchors. Horizontal spacing of
vertical bracing members shall not exceed one-half the unsupported
height of the wall nor 10 feet. Deflection of such bracing members
at design loads shall not exceed one-tenth of the wall thickness.
3. Wall Height Bracing. The wall height may be reduced' by
bracing elements connected to the floor or roof. Horizontal
spacing of the bracing elements and wall anchors shall be as
required by design but shall not exceed 6 feet on center. Bracing
elements shall be detailed to minimize the horizontal displacement
of the wall by the vertical displacement of the floor or roof.
(f) Parapets. Parapets and exterior wall appendages not
conforming to this Chapter shall be removed, or stabilized or
braced to ensure that the parapets and appendages remain in their
original position.
The maximum height of an unbraced unreinforced masonry parapet
above the lower of either the level of tension anchors or roof
sheathing, shall not exceed one and one-half (1-1/2) times the
thickness of the parapet wall. If the required parapet height
exceeds this maximum height, a bracing system designed for the
force factors specified in Table 23-P of the Building Code for
walls shall support the top of the parapet. Parapet corrective
work must be performed in conjunction with the installation of
tension roof anchors.
The minimum height of a parapet above the wall anchor shall be
twelve (12) inches.
EXCEPTION: If a reinforced concrete beam is provided at the
top of the wall, the minimum height above the wall anchor may
be six (6) inches.
(g) Veneer. 1. Unreinforced masonry walls which carry no design
loads other than their own weight may be considered as veneer if
they are adequately anchored to new supporting elements.
2. Veneer shall be anchored with approved anchor ties,
conforming to the required design capacity specified in
the Building Code and placed at a maximum spacing of 24 inches
with a maximum supported area of two (2) square feet.
EXCEPTION: Existing veneer anchor ties may be acceptable
provided the ties are in good condition and conform to the
following minimum size, maximum spacing and material
requirements.
Existing veneer anchor ties shall
iron strips not less than one inch
in length and one -sixteenth of an
8" X 1/16") or equal and shall be
be corrugated galvanized
in width, eight inches
inch in thickness (1" X
located and laid in
�:... _ .
12.
every alternate course in the vertical height of the wall
at a spacing not to exceed 17 inches on centers
horizontally. As an alternate, such ties may be laid in
every fourth course vertically at a spacing not to exceed
nine (9) inches on centers horizontally.
3. The location and condition of existing veneer anchor ties
shall be verified as follows:
A. An approved testing laboratory shall verify the
location and spacing of the ties and shall submit a report
to the Building Official for approval as a
part of the structural analysis.
B. The veneer in a selected area shall be removed to
expose a representative sample of ties (not less than four)
for inspection by the Building Official.
(h) Truss and Beam Supports. Where trusses and beams other
than rafters or joists are supported on masonry, independent
secondary columns shall be installed to support vertical loads of
the roof or floor members. The loads shall be transmitted down to
adequate support.
(i) Adjacent Buildings. 1. Where elements of adjacent
buildings, do not have a separation of 5 inches, the allowable
height/thickness ratios for "buildings with crosswalls" per Table
B shall not be used in the direction of consideration.
2. Where buildings do not have a separation of at least 5 inches
and the diaphragm levels of the adjoining structures differ by
more than one and one-half time the wall thickness, supplemental
vertical gravity load carrying members shall be added to support
the loads normally carried by the wall and such members shall not
be attached to the wall. The loads shall be transmitted down to
the foundation.
13.
TABLE
HORIZONTAL
CONFIGURATION OF MATERIALS
NO. A
FORCE FACTOR C
CP
Roofs with straight or diagonal 0.5
sheathing and roofing applied
directly to the sheathing, or
floors with straight tongue and
groove sheathing.
Diaphragms with double or
multiple layers of boards 0.75
with edges offset and blocked
plywood systems.
14.
TABLE NO. $_
ALLOWABLE VALUE OF HEIGHT -THICKNESS RATIO OF
UNREINFORCED MASONRY WALLS
Seismic Zone 3 Seismic Zone 4 Seismic Zone 4
Wall Types Buildings Buildings with All Other
Crosswallsl Buildinas
Walls of one-story 16
buildings
First -story wall 18
of multi -story
building
Walls in top story 14
of multi -story
buildings
All other walls 16
162,3 13
16 15
1423 9
16 13
lApplies to the Special Procedures of Section III (d) only. See
Section III (d)7 for other restrictions.
2This value of height -to -thickness ratio may be used only where
mortar shear tests establish a
tested mortar shear strength, vt, of not less than 100 psi or
where the tested mortar shear strength, vt, is not less than 60
psi and a visual examination of the collar joint indicates not
less than 50% mortar coverage.
3Where a visual examination of the collar joint indicates not less
than 50% mortar coverage and the tested mortar shear strength,
vt, is greater
than 30 psi but less than 60 psi, the allowable -height -to -
thickness ratio may be determined by linear interpolation between
the larger and smaller ratios in direct proportion to the tested
mortar shear strength, vt.
15.
TABLE NO. C. -
ALLOWABLE
ALLOWABLE VALUES FOR EXISTING MATERIALS
EXISTING MATERIALS OR CON-
FIGURATIONS OF MATERIALS) ALLOWABLE VALUES
1. HORIZONTAL DIAPHRAMS4
a. Roofs with straight 100 lbs. per foot
sheathing and roofing for seismic shear
applied directly to the
sheathing.
b. Roofs with diagonal 250 lbs. per foot
sheathing and roofing for seismic shear
applied directly to
the sheathing.
c. Floors with straight 100 lbs. per foot
tongue -and -groove for seismic shear
sheathing.
d. Floors with straight 500 lbs. per foot
sheathing and finished for seismic shear
wood flooring with
board edges offset or
perpendicular.
e. Floors with diagonal 600 lbs. per foot
sheathing and finished for seismic shear
wood flooring.
2. CROSSWALLS2,4
a. Plaster on wood or metal
Per
side: 200 lbs.
lath
per
foot for
seismic shear
b. Plaster on gypsum lath
175
lbs. per foot
for
seismic shear
C. Gypsum wall board,
75
lbs. per foot
unblocked edges
for
seismic shear
d. Gypsum wall board,
125
lbs. per foot
blocked edges
for
seismic shear
16.
TABLE NO.0 .
ALLOWABLE VALUES FOR EXISTING MATERIALS (Cont.)
EXISTING MATERIALS OR CON-
FIGURATIONS OF MATERIALS1 ALLOWABLE VALUES4
3. EXISTING FOOTINGS, WOOD
FRAMING, STRUCTURAL STEEL,
-AND REINFORCED STEEL
a. Plain concrete footings
b. Douglas fir wood.
C. Reinforcing steel.
d. Structural Steel.
f'c = 1500 psi unless
otherwise shown by
tests
Allowable stress same
as No. 1 D.F.3
ft = 18,000 lbs. per
square inch maximum.3
ft =20,000 lbs. per
square inch maximum.3
1Material must be sound and in good condition.
2Shear values of these materials may be combined, except the total
combined value shall not exceed 300 lbs. per foot.
3Stresses given may be increased for combinations of loads as
specified in Section 71"'
4A one-third increase in allowable stress is not allowed.
17.
N
w
4
540-----1---�--r---�-------t------r--� --�
480
420 _-- L• -1---1-- --1-- '_--L--1---+_-�
' � 1 -1 1 � 1 � 1 - �-- ' 1•
360
T - - - ' -----�
-; -�- 1
300--T•--•�--�-----,-------+--------,---1
� ,♦ 1 1 � 1 � 1 , I , 1
---r--1 �-1--J-
-t---L--r-- L-
--r---+---t---t.
t , ♦ t , 1 1 � 1 , 1 , 1
240 ---+•--1--♦ --'-----'-----1---+-----�---'
� , 1 ♦, 1 1 t 1 , 1 , 1
180---L--'----�--L ' -�--' --1-- '---'---'
- - -� - - r- - - 1 - -
1 ,O'
120 - - -'- - 1 -' - 1 - ' 1 - t - t -
---T--+--n---+---,-� ---r-- ----+---,---1.
1(D2'
60 _--t--1---1--,---j-----r--1----J---1---1
-----1---+---'---:-- L ----1--� -1---1
O
0 1
FIGURE N0. 1
2 3 4 5 6
Demand -Capacity Ratio, DCR
- ACCEPTABLE DIAPHRAGM SPAN
1.
TABLE NO. D4
ALLOWABLE VALUES OF NEW MATERIALS USED
IN CONJUNCTION WITH EXISTING CONSTRUCTION
NEW MATERIALS OR CONFIGURATIONS
OF MATERIALS ALLOWABLE VALUES4
HORIZONTAL DIAPHAGMS
Plywood sheathing applied
directly over existing
straight sheathing with
ends of plywood sheets
bearing on joists or
rafters and edges of
plywood located on center
of individual sheathing
boards.
CROSSWALLS
a. Plywood sheathing applied
directly over wood studs.
No value shall be given to
plywood applied over existing
plaster or wood sheathing.
b. Drywall or plaster applied
directly over wood studs.
c. Drywall or plaster applied
to sheathing over existing
wood studs.
225 lbs. per foot
1.33 times the value
specified in Table
No. 25-K-1 Uniform
Building Code for
shear walls.
100 percent of the
values in Table No.
47-I of the Uniform
Building Code.
50 percent of the
values plywood
specified in Table
No. 47-I of the
Uniform Building
Code.
19.
TABLE No. D4
ALLOWABLE VALUES OF NEW MATERIALS USED
IN CONJUNCTION WITH EXISTING CONSTRUCTION
(continued)
NEW MATERIALS OR CONFIGURATIONS
OF MATERIALS ALLOWABLE VALUES4
4. TENSION BOLTS
Bolts extending entirely 1800 lbs. per bolt.
through unreinforced
masonry walls secured 900 lbs. for 2 wythe
with bearing plates on far side walls.
of a 3 wythe minimum wall with at
least 30 square inches of area .2► 3
5. SHEAR BOLTS
Bolts embedded a
133 percent of the
minimum of 8 inches into
values for plain
unreinforced masonry walls.
masonry specified for
Bolts shall be centered in
solid masonry in
2-1/2 inch -diameter hole with
Tables No. 24-E of
the dry -pack or non -shrink grout
Uniform Building
around circumference of bolt.1,3
Code. No values
larger than those
given for 3/4 inch
bolts shall be used.
6. COMBINED TENSION AND SHEAR BOLTS
a. Through Bolts - Combined Shear and Tension
Bolts meeting the above requirements Tension: Same as for
for tension bolts and shear bolts1,2,3 tension bolts
Shear: Same as for
shear bolts
b. Embedded Bolts - Combined Shear and Ten_ion
Bolts extending to the exterior
face of the wall with a 2 1/2
inch round plate under the head
and drilled at an angle of
22-1/2 degrees -to the horizontal.
Installed as specified for shear
bolts. 1, 2,3
Tension: Same as for
tension bolts
Shear: Same as for
shear bolts
N
7.
TABLE NO. D4
ALLOWABLE VALUES OF NEW MATERIALS USED
IN CONJUNCTION WITH EXISTING CONSTRUCTION
(continued)
NEW MATERIALS OR CONFIGURATION
OF MATERIALS ALLOWABLE VALUES4
INFILLED WALLS
Reinforced masonry infilled
openings in existing unrein-
forced masonry walls. Provide
keys or dowels to match rein-
forcing.
8. REINFORCED MASONRY
Masonry piers and walls rein-
forced per Chapter 24.
9. REINFORCED CONCRETE
Concrete footings, walls and
piers reinforced as specified
in Chapter 26 of the Uniform
Building Code and designed for
tributary loads.
1Bolts to be tested
2Bolts to be 1/2 -inch minimum in diameter.
Same as values
specified for unrein-
forced masonry walls.
Same as values
specified in Section
2409.
Same as values
specified in
Chapter 26 of the
Uniform Chapter
Building Code.
3Drilling for bolts and dowels shall be done with an electric
rotary drill. Impact tools shall not be used for drilling holes
or tightening anchors and shear bolt nuts.
4A one-third increase in allowable stress is not allowed.
21.
DEFINITI%- 3, SYMBOLS, & NOTATIONS
DEFINITIONS: For the purposes of these ipegulations
applicable definitions in the Building Code shall also apply.
COLLAR JOINT is the vertical space between adjacent wythes and may
contain mortar.
CROSSWALL is a wall that meets the requirements of Section
A2346(d)3. A crosswall is not a shear wall.
CROSSWALL SHEAR CAPACITY is the length of the crosswall times the
allowable shear value, vcLo.
DIAPHRAGM EDGE is the intersection of the horizontal diaphragm and
a shear wall.
DIAPHRAGM SHEAR CAPACITY is the depth of the diaphragm times the
allowable shear value, vuD.
FLEXIBLE DIAPHRAGM is a diaphragm of wood construction or
other construction of similar flexibility.
NORMAL WALL is a wall perpendicular to the direction of seismic
forces.
OPEN FRONT is an exterior wall plane without vertical
elements in one or more stories which resist the required
lateral forces.
POINTING is the partial reconstruction of the bed
joints of a URM wall as defined in UBC Standard No. 24-42.
UNREINFORCED MASONRY (URM) WALL is a masonry wall in which the
area of reinforcing steel is less than 25 percent of that
required by the Building Code for reinforced masonry.
UNREINFORCED MASONRY BEARING WALL. A URM wall which provides the
vertical support for a floor or roof for which the total
superimposed load is over 100 pounds per linear foot of
wall.
YIELD STORY DRIFT is the lateral displacement of one level
relative to the level above or below at which yield
stress is first developed in a frame member.
Symbols and Notations. For the purposes of these regulations
the applicable symbols and definitions in the Building Code shall
also apply.
A = Area of unreinforced masonry pier, square inches.
22.
Ab = Area of the bed joints above and below the test
specimen for each in-place shear test.
C Numerical coefficient as specified in Section
2312(g) and given in Table 23-P of the Building
Code and Table A•_- of this Chapter..
D = In -plane width dimension of pier, inches, or depth
of diaphragm, feet.
DCR - Demand -capacity ratio specified in Section III (d),
Fwx = Force applied to a wall at level x, pounds.
H = Least clear height of opening on either side of
pier, inches.
h/t = Height/thickness ratio of URM wall. Height h is
measured between wall anchorage levels.
L = Span of diaphragm between shear walls, or
span between shear wall and open front, feet.
Lo = Length of crosswall, feet.
Li = Effective span for an open front building
specified in Section III (d)8, feet.
PD = Superimposed dead load at the top of the pier under
consideration, pounds.
PD+L = Actual dead plus live load in place at the time of
testing, pounds.
PW = Weight of wall, pounds.
Va = vaA, the allowable shear in any URM pier, pounds.
Vcb = Total shear capacity of crosswalls in the direction
of analysis immediately below the diaphragm level
being investigated, JvcLo, pounds.
Vca = Total shear capacity of crosswalls in the direction
of analysis immediately above the diaphragm level
being investigated, EvcLo, pounds.
Vr = 0.5PD(D/H), the rocking shear of any URM wall or
wall pier, pounds.
Vwx = Total shear force resisted by a shear wall at the
23.
level under consideration, pounds.
Vp Shear force assigned to a pier on the basis of
its relative shear rigidity, pounds.
Vs = Shear force assigned to a spandrel on the
basis of the shear forces in the adjacent wall
piers and tributary dead plus live loads.
Vtest Load in pounds at incipient cracking for each in-
place shear test per UBC Standard 23-40.
va = Allowable shear stress for unreinforced masonry,psi.
vc = Allowable shear value for a crosswall sheathed with
any of the materials given in Tables C or
DS pounds per foot.
vt = Mortar shear strength
vto = Mortar shear test values
vu = Allowable shear value for a diaphragm sheathed with
any of the materials given in Tables C or
D, pounds per foot.
IvuD = Sum of diaphragm shear capacities of both ends
of the diaphragm.
17-vuD = For diaphragms coupled with crosswalls 7-7-vuD
includes the sum of shear capacities of both ends of
diaphragms coupled at and above the
level under consideration.
Wd = Total dead load tributary to a diaphragm, pounds.
IWd = Total dead load tributary to all of the diaphragms
at and above the level under consideration,
pounds.
Ww = Total dead load of an unreinforced masonry
wall above the level under consideration or
above an open front of a building, pounds.
Wwx = Dead load of a URM wall assigned to Level x
halfway above and below the level under
consideration.
24.