The Construction Specifier
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solutions for the construction industry | september 2012 Specifying Seismic Ceiling Safety Ensuring security for suspended systems by Tony Ingratta Photo © Steve Wanke Photography. Photo courtesy Chicago Metalic Corp. Increasingly, building design and implementation teams assume responsibilities associated with earthquake hazard mitigation efforts and rebuilding plans. Now, more owners, planners, designers, contractors, specifiers, manufacturers, and property managers must collaborate in achieving safety goals to protect occupants in the event of an earthquake.

Figure 1 SDC Meaning A Very small seismic vulnerability B Low to moderate seismic vulnerability C Moderate seismic vulnerability D High seismic vulnerability E and F Very high seismic vulnerability and near a major fault, with very poor and liquefiable soil Structural engineers ultimately have responsibility for building elements and systems, such as beams and columns that carry the structure’s loads, both vertically and laterally. However, these components only represent a quarter of a typical commercial building’s inventory. The remaining three-quarters are the non-structural...

Figure 3a Description of changes from 2009 IBC to 2012 IBC Reference Section General ASCE 7-10 13.5.6(2) Ceilings constructed of gypsum board, screw- or nail-attached to suspension members on one level, and connected to walls or soffits are exempt from the lateral-force bracing requirements. Please note: lath and plaster ceilings no longer have a general exemption. Soffits were added. SDC C ASTM E580 4.1.2 There is 27-kg (60-lb) strength required for expansion devices. Alternate test method for five-degree misalignment–may use 25.4-mm (1-in.) eccentricity on a 610-mm (2-ft) long section...

Approved seismic perimeter clips meeting International Code Council (ICC) criteria can exceed the minimum code requirement, saving costs and installation time associated with conventional methods. Cost-effective solutions to seismic requirements are grid suspension systems constructed to allow direct upward access to mechanical systems. Stab-in cross-tees cantilever during installation and will not fall out, making for easier installation and protecting against lateral pullout. Images courtesy Chicago Metallic Corp. helps increase safety and may decrease possible long-term liability costs....

Figure 3b Description of changes from 2009 IBC to 2012 IBC SDCs D, E, and F ASCE 7-10 13.5.6.2.2 Seismic perimeter clips used in lieu of 51-mm (2-in.) wide angle/channel must be qualified using approved test criteria. Further, area aspect ratio for seismic separation joints, from the long to short dimension, should be 4:1 maximum. ASCE 7-10 13.4.5 Power-actuated fasteners allowed for suspended ceilings are: • concrete–41 kg (90 lb) maximum allowed service load; and • steel–113.4 kg (250 lb) maximum allowed service load. ASTM E580 5.2.9.1 Seismic separation joint ± 19-mm (3/4-in.) axial...

Seismic Areas and Activities The Earth’s surface is made up of slowly moving tectonic plates. Friction causes the adjoining plates to stick at their edges, creating fault lines. When the stress on the fault lines overcomes the friction, a sudden ‘slip’ between the two plates occurs, causing an earthquake that releases energy in waves through the Earth’s crust. There have been many large earthquakes in the United States in the last decade that have caused great concern.* In the Western United States, estimates indicate a 62 percent probability of at least one magnitude 6.7 or greater quake...

The extended integral tab on some seismic separation tees allows them to push toward and pull away from the designated seismic joint main tee and maintain a strong connection. The push rivets enable the joint to withstand a pullout force in excess of 81.65 kg (180 lb). The internal friction in the joint also provides a measure of damping. An accepted method for creating a seismic separation joint involves capping each of the main runners on the ends, with a wall channel, for the length of the separation joint. A wall angle is then attached atop one channel to cover the gap and prevent the...

Following the 1994 Northridge earthquake where 11 hospitals were damaged, California passed a law requiring hospitals built before 1973 to be retrofitted to higher seismic standards established by the Office of Statewide Health Planning and Development (OSHPD). An approved alternative construction method relies on a seismic perimeter clip. These attach to a wall molding and the main or cross-tees that support ceiling tiles. For seismic design category (SDC) C, use of an approved seismic perimeter clip may eliminate the need for spacer bars. Image courtesy Chicago Metalic Corp. Photo © Steve...

This 24-mm (0.95-in.) seismic suspension system is installed with 152.4-mm (6-in.) trim for a smooth finished look throughout the ceiling of the Williams-Brice Stadium Players Lounge in South Carolina. Photo courtesy Chicago Metallic Corp. » Not only did the California Mission-styled hospital renovate and upgrade its existing facility, but also doubled in size to serve the healthcare needs for its growing community. For example, the emergency room previously designed to accommodate approximately 25,000 patients per year, now has the capacity to serve 80,000 people anually. Photo © Steve...