Page 498 - Design of Reinforced Masonry Structures

7.60 CHAPTER SEVEN

A. Buildings with irregular configuration

Other complex
T-shaped plan L-shaped plan U-shaped plan Cruciform plan shapes

Outwardly uniform
Unusually Unusually appearance but
Setbacks Multiple towers Split levels high story low story nonuniform mass
distribution, or converse
B. Buildings with abrupt changes in lateral resistance

“Soft” lower Large opening Interruption Interruption Opening in
levels in shear walls of columns of beams diaphragms
C. Buildings with abrupt changes in lateral stiffness

Shear walls in some Interruption of vertical- Abrupt changes Drastic changes
stories, moment-resisting resisting elements in size of members in mass/stiffness
frames in others ratio
D. Unusual or novel structural features

Cable-supported Shells Staggered Buildings
structures trusses on hillsides

FIGURE 7.25 Varieties of vertical irregularities [7.15].

4. Out-of-plane offsets irregularity
5. Nonparallel systems irregularity
Each of these irregularities carries certain design requirements as listed Table 12.3-1
of ASCE 7-05 Standard, specified by various sections in that table. Those sections refer to
seismic design categories of structures (categories A through F) as specified in Section 11.6
of ASCE 7-05 Standard. The seismic design category of a structure is determined based on
its occupancy category listed in Table 1-1 of the Standard, as well as on the design spectral