Page 109 - ICC IEBC 2018

APPENDIX A

[BS] A111.6 Shear walls (In-plane loading). SECTION A112
[BS] A111.6.1 Wall story force. The wall story force dis- ANALYSIS AND DESIGN
tributed to a shear wall at any diaphragm level shall be the [BS] A112.1 General. The following requirements are appli-
lesser value calculated as: cable to both the general procedure and the special procedure
for analyzing vertical elements of the lateral force-resisting
F wx = 0.8S D1 ( W wx + W /2) d (Equation A1-13) system.
but need not exceed [BS] A112.2 In-plane shear of unreinforced masonry
walls.
F wx = 0.8S D1 W wx + v D (Equation A1-14)
u
[BS] A112.2.1 Flexural rigidity. Flexural components of
[BS] A111.6.2 Wall story shear. The wall story shear deflection need not be considered in determining the rigid-
shall be the sum of the wall story forces at and above the ity of an unreinforced masonry wall.
level of consideration. [BS] A112.2.2 Shear walls with openings. Wall piers
V wx = ΣF wx (Equation A1-15) shall be analyzed according to the following procedure,
which is diagrammed in Figure A112.2.2.
[BS] A111.6.3 Shear wall analysis. Shear walls shall 1. For any pier,
comply with Section A112.
1.1. The pier shear capacity shall be calculated
[BS] A111.6.4 New seismic force-resisting elements. as:
New seismic force-resisting elements such as moment
frames, braced frames or shear walls shall be designed as v = v A n (Equation A1-18)
a
m
required by the building code, except that the seismic where:
forces shall be as specified in Section A111.6.1, and the A = area of net mortared or grouted section
story drift ratio shall be limited to 0.015, except as further n of a wall or wall pier.
limited by Section A112.4.2 for moment frames.
1.2. The pier rocking shear capacity shall be cal-
[BS] A111.7 Out-of-plane forces—unreinforced masonry culated as:
walls.
V = 0.9P D/H (Equation A1-19)
[BS] A111.7.1 Allowable unreinforced masonry wall r D
height-to-thickness ratios. The provisions of Section 2. The wall piers at any level are acceptable if they
A110.2 are applicable, except the allowable height-to- comply with one of the following modes of behav-
thickness ratios given in Table A110.2 shall be determined ior:
from Figure A111.4.1 as follows:
2.1. Rocking controlled mode. Where the pier
1. In Region 1, height-to-thickness ratios for buildings rocking shear capacity is less than the pier
with crosswalls may be used if qualifying crosswalls shear capacity, in other words, V < v , for
a
r
are present in all stories. each pier in a level, forces in the wall at that
2. In Region 2, height-to-thickness ratios for buildings level, V , shall be distributed to each pier in
wx
with crosswalls may be used whether or not qualify- proportion to P D/H.
D
ing crosswalls are present. For the wall at that level:
3. In Region 3, height-to-thickness ratios for “all other 0.7V < ΣV (Equation A1-20)
buildings” shall be used whether or not qualifying wx r
crosswalls are present. 2.2. Shear controlled mode. Where the pier shear
capacity is less than the pier rocking capac-
[BS] A111.7.2 Walls with diaphragms in different ity, in other words, v < V in one or more
regions. Where diaphragms above and below the wall pier(s) in a level, forces in the wall at the
r
a
under consideration have demand-capacity ratios in differ- level, V , shall be distributed to each pier in
ent regions of Figure A11.4.1, the lesser height-to-thick- proportion to D/H.
wx
ness ratio shall be used.
For each pier at that level:
[BS] A111.8 Open-front design procedure. A single-story
building with an open front on one side and crosswalls parallel V < v a (Equation A1-21)
p
to the open front may be designed by the following procedure:
and
1. Effective diaphragm span, L , for use in Figure
i V < V (Equation A1-22)
A111.4.1 shall be determined in accordance with the p r
following formula: If V < v for each pier and V > V for one
p
r
a
p
or more piers, such piers shall be omitted
L = 2[(W /W )L + L] (Equation A1-16)
d
w
i
from the analysis, and the procedure shall be
2. Diaphragm demand-capacity ratio shall be calculated repeated for the remaining piers, unless the
as: wall is strengthened and reanalyzed.
DCR = 2.1S (W + W )/[(v D) + V ] 3. Masonry pier tension stress. Unreinforced masonry
d
w
u
D1
cb
(Equation A1-17) wall piers need not be analyzed for tension stress.
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