30 November 1998
SEISMIC DESIGN EXAMPLE
(English I-P units only)
D1. EXAMPLE DESIGN PROBLEM. An example problem is presented here to demonstrate the
design process presented in Chapter 3 and Appendix C. Shear panels will be designed in the short
direction of the building only to illustrate the design process. In an actual building the lateral load
resisting system must be designed in both directions. This example is a barracks-type building that
will be designed for construction at Fort Lewis, located between Tacoma and Olympia, Washington.
This building is similar to a Prototype 3 Story Steel Stud Framed Barracks Building for Seismic Zones
0 21. The reader will be referred to tabular data and equations presented in Chapter 3 and
Appendix C. When needed, FEMA 302 guidance will be referenced.
The barracks building has a Seismic Use Group of I (FEMA 302, 1.3), which gives it an Occupancy
Importance Factor, I, of 1.0 (see Table C-1).
D2. GROUND MOTION DEFINITION. The maximum considered earthquake ground motions are
determined from spectral response acceleration Maps 9 and 10 (for the Pacific Northwest). The
spectral response acceleration for short periods, SS, is 1.2 g (Map 9). The spectral response
acceleration for 1 second, S1, is 0.39 g (Map 10). Table D-1 summarizes these values. These
values are determined by interpolating between the map contours for the Fort Lewis location. The
soil conditions are unknown, so a reasonable worst-case site classification of D is used. Values of
Site Coefficients, Fa and Fv, are calculated based on straight-line interpolation from the values in
Tables C-2a and C-2b, and are shown in Table D-1. Values for the maximum considered earthquake
spectral response acceleration for short periods, SMS and at 1 second, SM1 adjusted for site class
effects, are calculated using Equations C-1 and C-2, and are shown in Table D-1. Design earthquake
spectral response acceleration at short periods, SDS and 1 second period, SD1 are calculated using
Equations C-3 and C-4, and are shown in Table D-1.
Table D-1. Earthquake Ground Motion Definition
Summary for Fort Lewis.
Importance Factor, I
Short Period Spectral Response Acceleration, SS
1 Second Spectral Response Acceleration, S1
Site Coefficient, Fa
Site Coefficient, Fv
Adjusted Short Period Spectral Response Acceleration, SMS
Adjusted 1 Second Spectral Response Acceleration, SM1
Design Short Period Spectral Response Acceleration, SDS
Design Short Period Spectral Response Acceleration, SD1
Assumed Design Spectral Response Acceleration, Sa
Seismic Design Category
Response Modification Factor, R
Deflection Amplification Factor, Cd
A design response spectrum is developed from these terms, as described in Appendix C, Paragraph
C2, using Equations C-5 and C-6, and plotted in Figure D-1. For the natural period of the structure,
T, this spectrum defines values of effective acceleration. The natural period of the barracks building,
T, will almost certainly fall between T0 and TS, defined in Appendix C, Paragraph C2, so that the
U.S. Army Corps of Engineers Barracks Prototype Department of the Army, for the National Association of Architectural Metal
Manufactures (NAAMM), by Matsen Ford Design, Drawings Dated 1/3/97.