July 2006
H-18-8
3.0 MODIFICATIONS TO THE REQUIREMENTS OF IBC FOR NEW CRITICAL AND
ESSENTIAL FACILITIES IN AREAS OF HIGH AND VERY HIGH SEISMICITY
3.1 Structural Irregularities (ASCE 7, Section 12.3.3)
Structures assigned to Seismic Design Categories D, E, or F, the following types
of irregularities as defined by ASCE 7 Table 12.3-1 & 2 are not allowed:
a.
Stiffness irregularity Soft Story
b.
Stiffness irregularity Extreme Soft Story
c.
Weight (mass) irregularity
d.
Vertical geometric irregularity
3.2 Seismic-force-resisting-systems (ASCE 7, Table 12.2-1)
The following structural systems are permitted for new facilities in all Seismic
Design Categories:
a. Building Frame Systems
i. Steel eccentrically braced frames (EBF) moment resisting connections at
columns away from links
ii. Special reinforced concrete shear walls (Building Frame)
iii. Special reinforced masonry shear walls (Building Frame)
iv. Special steel concentrically braced frames
v. Light frame walls with shear panels-wood structural panels/sheet steel
panels (Building Frame) for structures two stories or less
b. Moment-resisting Frame Systems
i. Special steel moment-resisting frames (SMRF), if approved
ii. Special reinforced concrete moment-resisting frames
c. Dual Systems
i. Special reinforced concrete shear walls with SMRF
ii. Special reinforced masonry shear walls with SMRF
iii. Steel EBF with SMRF
iv. Special steel concentrically braced frame with SMRF
All other structural systems are not permitted unless written approval is obtained
from VA.
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