The high roof and low roof structures share a common transverse moment frame at their interface.
However, in the longitudinal direction, the low roof structure is essentially isolated from the high roof
structure at this location. This is accomplished by the use of a simple gravity connection consisting of
elongated slotted holes that attach the low roof support beam to the moment frame column.
The building is considered regular both in plan and vertically.
(5) Choice of materials. Columns shall be designed using ASTM A572 Grade 50 and braces
using ASTM A24 Grade 46. All other steel components will use ASTM A36 Grade 36. All walls not
shown on the floor framing plans are intended to be nonstructural and shall be constructed so as to not
impair the response of the steel moment frames and steel braced frames.
c. Preliminary building design (following steps in Table 4-5 for Life Safety). The preliminary design
of the building follows the steps outlined in Table 4-5 for Performance Objective 1A. The design is then
updated to meet the enhanced performance objectives laid out in Table 4-6 for Performance Objective 2A.
A-1 Determine appropriate Seismic Use Group. Per Table 4-3 of the manual, the building must be
safe to occupy immediately after an earthquake and is required for post earthquake recovery. Therefore, it
is an essential structure with a Seismic Use Group of IIIE.
A-2 Determine Site Seismicity. The site seismicity for this example from the MCE maps is:
SS = 0.80g, and S1 = 0.40g.
A-3 Determine Site Characteristics. For the purpose of this problem, a very dense soil and soft rock
condition was assumed corresponding with a site classification of ` lass C'per Table 3-1 of the TI manual.
A-4 Determine Site Coefficients, Fa and Fv. From Tables 3-2a and 3-2b for the given site seismicity
and soil characteristics, the site response coefficients were interpolated as follows:
Fa = 1.08
Fv = 1.40
SMS = Fa(SS) = 1.08(0.80) = 0.86
SM1 = Fv(S1) = 1.40(0.40) = 0.56
SDS = (2/3)SMS = (2/3)0.86 = 0.57
SD1 = (2/3)SM1 = (2/3)0.56 = 0.37
The approximate period of the structure (based on T = 0.1N, where N = number of stories) is:
Tapprox = 0.1N = 0.1(2) = .2 < .5
(EQ. 188.8.131.52-2 FEMA 302)
Since Tapprox = .2 < .5, and because the structure is less then 5 stories is height; equations 3-5 and 3-6 of the
TI 809-04 manual must be checked in the short period range:
SDS ≤ 1.5Fa
SD1 ≤ 0.6Fv
SDS = 0.57 < 1.5(1.08) = 1.62 = 1.5Fa
SD1 = 0.37 < 0.6(1.40) = 0.84 = 0.6Fv
Use SDS = 0.57, & SD1 = 0.37