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APPENDIX A
SECTION A108 the general procedure or, where applicable, are permitted to be
DESIGN STRENGTHS analyzed by the special procedure of Section A111.
[BS] A108.1 Strength values.
1. Strength values for existing materials are given in SECTION A110
Table A108.1(1) and for new materials in Table GENERAL PROCEDURE
A108.1(2).
[BS] A110.1 Minimum design lateral forces. Buildings
2. The strength reduction factor, φ, shall be taken equal to shall be analyzed to resist minimum lateral forces assumed to
1.0. act nonconcurrently in the direction of each of the main axes
3. The use of materials not specified herein shall be based of the structure in accordance with the following:
on substantiating research data or engineering judg- 0.75S W
DS
ment, as approved by the code official. V = ------------------------ (Equation A1-5)
R
[BS] A108.2 Masonry shear strength. The unreinforced
masonry shear strength, v , shall be determined for each [BS] A110.2 Seismic forces on elements of structures.
mL
masonry class from one of the following equations: Parts and portions of a structure not covered in Section
A110.3 shall be analyzed and designed per the current build-
1. When testing is performed in accordance with Section
A106.2.3.1, the unreinforced masonry shear strength, ing code, using force levels defined in Section A110.1.
v , shall be determined by Equation A1-3. Exceptions:
m
P
D
0.75 0.75v ------ 1. Unreinforced masonry walls for which height-to-
thickness ratios do not exceed ratios set forth in
A
tL
n
v mL = ----------------------------------------- (Equation A1-3) Table A110.2 need not be analyzed for out-of-plane
1.5
loading. Unreinforced masonry walls that exceed the
allowable h/t ratios of Table A110.2 shall be braced
The mortar shear strength values, v , shall be deter-
tL according to Section A113.5.
mined in accordance with Section A106.2.3.5.
2. Parapets complying with Section A113.6 need not
2. When alternate testing is performed in accordance with
Section A106.2.3.2, unreinforced masonry shear, v , be analyzed for out-of-plane loading.
mL
shall be determined by Equation A1-4. 3. Where walls are to be anchored to flexible floor and
roof diaphragms, the anchorage shall be in accor-
P D dance with Section A113.1.
0.75 f + ------
A
sp
n
v mL = ----------------------------------- (Equation A1-4) [BS] A110.3 In-plane loading of URM shear walls and
1.5
frames. Vertical seismic force-resisting elements shall be
analyzed in accordance with Section A112.
[BS] A108.3 Masonry compression. Where any increase in
wall dead plus live load compression stress occurs, the maxi- [BS] A110.4 Redundancy and overstrength factors. Any
mum compression stress in unreinforced masonry, Q /A , redundancy or overstrength factors contained in the building
n
G
shall not exceed 300 pounds per square inch (2070 kPa). code may be taken as unity. The vertical component of seis-
[BS] A108.4 Masonry tension. Unreinforced masonry shall mic force (E ) may be taken as zero.
v
be assumed to have no tensile capacity.
[BS] A108.5 Wall tension anchors. The tension strength of SECTION A111
wall anchors shall be the average of the tension test values for SPECIAL PROCEDURE
anchors having the same wall thickness and framing orienta- [BS] A111.1 Limits for the application of this procedure.
tion. The special procedures of this section shall be applied only to
[BS] A108.6 Foundations. For existing foundations, new buildings having the following characteristics:
total dead loads are permitted to be increased over the exist- 1. Flexible diaphragms at all levels above the base of the
ing dead load by 25 percent. New total dead load plus live structure.
load plus seismic forces may be increased over the existing 2. Vertical elements of the seismic force-resisting system
dead load plus live load by 50 percent. Higher values may be consisting predominantly of masonry or a combination
justified only in conjunction with a geotechnical investiga- of masonry and concrete shear walls.
tion.
3. Except for single-story buildings with an open front on
one side only, not fewer than two lines of vertical ele-
SECTION A109 ments of the seismic force-resisting system parallel to
ANALYSIS AND DESIGN PROCEDURE
each axis of the building (see Section A111.8 for open-
[BS] A109.1 General. The elements of buildings hereby front buildings).
required to be analyzed are specified in Table A102.1.
[BS] A111.2 Seismic forces on elements of structures.
[BS] A109.2 Selection of procedure. Buildings with rigid dia- With the exception of the provisions in Sections A111.4
phragms shall be analyzed by the general procedure of Section through A111.7, elements of structures shall comply with
A110. Buildings with flexible diaphragms shall be analyzed by Sections A110.2 through A110.4.
88 2018 INTERNATIONAL EXISTING BUILDING CODE ®
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