(1) Purpose.

The purpose of this example problem is to illustrate the design of suspended

ceiling bracing using Chapter 10 of this manual, and Chapter 6 of FEMA 302 (Components). Suspended

ceiling systems without adequate lateral bracing have collapsed in a number of earthquakes causing injury

to building occupants and disruption of safe egress and building function.

(2) Scope.

The problem follows the steps in Tables 4.5 and 4.6 to analyze the ceiling

bracing and anchors. Typical ceiling bracing details found in Figure 10-4 are inadequate for immediate

occupancy in high seismic zones.

The ceiling used in this example problem is suspended from a roof framing system consisting of steel joists

and metal decking. The ceiling and equipment laterally supported by the ceiling, such as light fixtures and

HVAC registers, are required to function after an earthquake.

A.1 *Determine appropriate Seismic Use Group*

Due to the requirement that the ceiling and associated equipment must be functional after an earthquake,

the ceiling and attachments are given a performance level of immediate occupancy (IO). The Seismic Use

Group and other performance parameters are determined from Table 4-4, as follows;

Performance Level:

IO

(per problem statement)

Seismic Use Group:

IIIE

(Table 4-4)

Ground Motion:

3/4 MCE (B)

(Table 4-4)

Performance Objective:

3B

(Table 4-4)

A.2 *Determine site seismicity.*

The following value is assumed for this example:

SS = 1.50g

(MCE Maps)

A.3 *Determine site characteristics.*

Soil type D is assumed for this problem

Soil type: D

(Table 3-1)

A.4 *Determine site coefficients.*

Fa = 1.0

(Table 3-2a)

A.5 *Determine adjusted MCE spectral response accelerations.*

SMS = FaSS = 1.0(1.50)g = 1.50g

(EQ. 3-1)

A.6 *Determine design spectral response accelerations.*

SDS = 3/4 SMS = 3/4(1.50) = 1.125g

(EQ. 3-3)

I1-1

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