6.4 MECHANICAL, ELECTRICAL, AND PLUMBING COMPONENTS …€¦ · 6.4 MECHANICAL, ELECTRICAL, AND...

Available at: http://www.fema.gov/plan/prevent/earthquake/fema74/ Last Modified: January 2011

FEMA E-74 6: Seismic Protection of Nonstructural Components Page 6-346

6.4 MECHANICAL, ELECTRICAL, AND PLUMBING COMPONENTS

6.4.7 ELECTRICAL AND COMMUNICATIONS EQUIPMENT

6.4.7.2 EMERGENCY GENERATORS

Emergency generators are essential for postearthquake operations for many types of facilities. These range from small residential size generators to large systems required to maintain hospital or other essential operations. Emergency generators are often mounted on vibration isolators.

TYPICAL CAUSES OF DAMAGE

Emergency generators may slide, tilt, or overturn. Internal elements may be damaged by inertial forces.

Unanchored or poorly reinforced housekeeping pads may fail, resulting in excessive movement of the supported equipment.

Vibration isolators can fail causing excessive generator movement. Failure of the emergency power generating system may be caused by the failure of any

of the component parts including generator, fuel tank, fuel line, batteries and battery racks.

SEISMIC MITIGATION CONSIDERATIONS

Working around electrical equipment can be extremely hazardous. Read the Electrical Danger Warning and Guidelines in Section 6.6.8 of this document before proceeding with any work.

Many equipment items can be supplied with a structural steel base, shop welded brackets, or predrilled holes for base anchorage. For any new equipment, request items that can be supplied with seismic anchorage details.

For equipment mounted on a free-standing concrete pad, make sure pad is large enough to resist seismic overturning of generator.

Check the anchorage for all the component parts of the emergency power generation system; failure of any one of them could compromise the postearthquake performance of the system. Provide flexible connections for the fuel line, exhaust ducting and any other connected utility.

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See Section 6.4.1.1 for additional base anchorage details. Refer to FEMA 413 Installing Seismic Restraints for Electrical Equipment (2004) for general information on seismic anchorage of electrical equipment.

Mitigation Examples

Figure 6.4.7.2-1 Emergency generator is anchored to a concrete inertia base. The inertia base is mounted on spring isolators and restrained by steel angle snubbers on all sides (Photo courtesy of Maryann Phipps, Estructure).




Figure 6.4.7.2-2 Emergency generator with skid mount on housekeeping pad; shear lugs added following the 2001 Peru Earthquake (Photo courtesy of Eduardo Fierro, BFP Engineers).




Mitigation Details

Figure 6.4.7.2-3 Emergency generator (ER).






6.4.7.3 TRANSFORMERS

Transformers may be dry-type or liquid filled; mounted on a floor, wall or roof; and installed with or without vibration isolation.


Transformers may slide, tilt, overturn, or fall. Vibration isolation hardware may be damaged.

Internal elements may be damaged by inertial forces. Damaged electrical equipment may be cause electrical hazards and fire hazards.

Transformer damage may result in power outages and business interruption.

Damage Examples

Figure 6.4.7.3-1 Rail mounted transformer slipped off rails at power plant in Port-au-Prince in the 2010 magnitude-7 Haiti Earthquake; only one of six identical transformers was damaged (Photo courtesy of Eduardo Fierro, BFP Engineers).



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This type of equipment can be supplied with a structural steel base, shop welded brackets, or predrilled holes for base anchorage. For any new equipment, request items that can be supplied with seismic anchorage details.

See Section 6.4.1.1 for additional base anchorage details. Refer to FEMA 413 Installing Seismic Restraints for Electrical Equipment (2004) for additional mounting configurations such as wall- and roof-mounting, or vibration isolation as well as general information on the seismic anchorage of electrical equipment.




Mitigation Details

Figure 6.4.7.3-2 Transformer (ER).






6.4.7.4 BATTERIES AND BATTERY RACKS

This category covers batteries and battery racks, often used as part of the emergency generation system. These may be mounted on a concrete floor, raised floor, wall or roof.


The racks may slide or overturn and batteries may slip or fall from the rack. Failure of the batteries may compromise the emergency power generation system or other functions that rely on backup battery power.

Damage Examples

Figure 6.4.7.4-1 Earthquake Damage in the 1971 magnitude-6.6 San Fernando Earthquake (Photo courtesy of John F. Meehan).





Seismic resistant battery racks are available from a number of vendors; these may be directly bolted to the floor or wall. Check the internet for available products.

For existing battery racks, check that the batteries are secured to the rack and that the rack is properly braced and anchored.

Mitigation Examples

Figure 6.4.7.4-2 Anchored battery racks (Photo courtesy of Eduardo Fierro, BFP Engineers).




Figure 6.4.7.4-3 Batteries anchored with equipment skid (Photo courtesy of Eduardo Fierro, BFP Engineers).

Figure 6.4.7.4-4 Battery rack that performed well in the 2010 magnitude-8.8 Chile Earthquake (Photo courtesy of Rodrigo Retamales, Rubén Boroschek & Associates).




Mitigation Details

Figure 6.4.7.4-5 Batteries and rack (ER).






6.4.7.5 PHOTOVOLTAIC (PV) POWER SYSTEMS

This category covers photovoltaic (PV) power systems and solar car charging stations, commonly mounted on roofs or on separate freestanding racks.


As the installation of these fixtures on U.S. rooftops is relatively new, there are few documented examples of earthquake damage to date. This is in part due to the fact that since panels tend to be very light, the most severe design loading for roof-mounted photovoltaic panels is typically wind. Nevertheless, if these have not been properly designed to meet seismic loading, the panels may become dislodged and fall from the racks or fall off of pitched roofs or piping may be damaged, resulting in leakage. Wiring may also become dislodged and disable the systems.


Solar power is a rapidly changing field; these products and systems are evolving. Where existing photovoltaic systems may weigh between 2.5 to 3.0 pounds per square foot and consist of glass covered modules that are roof mounted on aluminum or galvanized steel track, newer products include lighter panels without glass, solar roof tiles that interlock with standard S-shaped clay or concrete roofing tiles, or peel and stick panels which weigh under 2 pounds per square foot that may be applied directly to the roof surface. Several of these newer systems are integrated with the roofing materials and may not require special seismic consideration as long as the additional weight is accounted for. Ballasted photovoltaic systems are also available that do not require anchorage or penetration of the roofing membrane. Check the internet for proprietary systems.

Photovoltaic panels supported on framing systems are typically flush mounted or tilt mounted. These systems typically have anodized aluminum or galvanized steel track channels mounted to brackets or standoffs which are mounted to roof framing or structural supports. The panels or modules are then screwed directly to the track,




typically four per panel. For installation on a wood framed roof, the system layout works best when the track is mounted perpendicular to the rafters; blocking may be required between the rafters where the track is mounted parallel to the rafters. Care must be taken to see that the roof penetrations are well sealed so the photovoltaic power system does not cause roof leaks. Friction fittings should not be used to resist seismic loading; positive connections should be provided between all the component parts.

Photovoltaic power systems may be installed on top of carports for charging electric cars. Before mounting an expensive solar system on top, it must be ensured that the carport or patio structures have been designed for seismic loading.

The State of California has published DSA IR 16-8 Solar Photovoltaic and Thermal Systems Acceptance Requirements (California Department of General Services, 2010a) to address requirements for California schools. This document describes solar systems supported on framing systems and foundations, ballast panel systems, and adhered panel systems.

Installation guidelines are available on the internet for proprietary flush mount kits and tilt up kits. For example, UniRac, Inc. has installation manuals for two proprietary systems called SolarMount and Clicksys (see http://unirac.com/mounting-solutions). These installation manuals have wind and snow load tables with wind loading from 90 mph to 170 mph. Although there is no explicit mention of seismic provisions, the detailing will be adequate if designed sufficiently for wind. A review of the tabulated wind design loads shows these systems are engineered for 10 psf to over 100 psf uplift; thus a well engineered wind design for a photovoltaic system typically weighing less than 3 psf should not require additional seismic detailing. Another company, Professional Solar Products (http://www.prosolar.com/prosolar-new/pages/installation-guides-subpage2.htm) has hardware with installation guides for tilt up kits designed for 30 psf or 100 mph winds.

Like any components exposed to the weather, components and connectors for photovoltaic systems should be corrosion resistant materials such as stainless steel or anodized aluminum. Where roof penetrations are required, these should have appropriate flashing and caulking to prevent leakage.


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Mitigation Examples

Figure 6.4.7.5-1 60,000 photovoltaic cells are incorporated into the glass canopy surrounding the Academy of Science, San Francisco, California (Photos courtesy of Cynthia Perry, BFP Engineers). The photovoltaic system provides 10% of the electricity needed for the facility. Panels must be securely attached to resist wind loads but also because these cantilevered members may be subject to vertical as well as horizontal seismic forces.




Figure 6.4.7.5-2 Ground mounted photovoltaic system that also provides shade to injured animals at the Marine Mammal Center in Sausalito, California (Photo courtesy of Cynthia Perry, BFP Engineers). Each solar panel is screwed to the strut at four locations; two rows of struts are bolted to 6 steel tubes which are anchored at the base with four bolts apiece.




Figure 6.4.7.5-3 Residential photovoltaic system in Berkeley, California mounted over the transition between two different roof slopes (Photos courtesy of Heber Santos). Short standoff used on tar and gravel flat portion (upper left); aluminum flashing and mounting bracket used on sloped portion with composition tile roofing (upper right). The profile of one type of proprietary mounting track is seen at lower left.




Figure 6.4.7.5-4 Flush mount photovoltaic system on barrel shaped roof of gymnasium at Head-Royce School, Oakland, California (Photo courtesy of Cynthia Perry, BFP Engineers).




Mitigation Details

Figure 6.4.7.5-5 Typical details for flush-mounted photovoltaic power modules (ER).




Figure 6.4.7.5-6 Typical tilt up details for anchored photovoltaic power modules (ER).





6.4.7 ELETRICAL AND COMMUNICATIONS EQUIPMENT

6.4.7.6 COMMUNICATIONS ANTENNAE

This category covers communications antennae, often referred to as satellite dishes, which may be mounted in a variety of ways. Circular antennae used for residential or small commercial applications are typically supported by a single mast that may be mounted on a wall, roof, chimney, eaves, balcony, or freestanding at the ground. Non-penetrating roof mounts that typically rely on ballast are also available.


While TV antennae have been mounted on roofs for many decades, the appearance of circular antennae on U.S. rooftops is relatively new, and to date, earthquake damage has not been documented. This is in part due to the fact that since antennae tend to be very light, the most severe design loading for circular antennae is typically wind. Nevertheless, if antennae have not been mounted to meet seismic loading, they could become dislodged and either the dish or the mast or both could fall.

Damage to the antennae could disable critical communications systems or television access that may be needed following an earthquake.




Damage Examples

Figure 6.4.7.6-1 Most antenna are designed for wind and able to resist seismic loading. In spite of the collapse of the first story of this residential building complex, the roof-mounted antennae appear intact in the 2010 magnitude-8.8 Chile Earthquake (Photo courtesy of Eduardo Fierro, BFP Engineers).




Figure 6.4.7.6-2 Antennae retrieved from roof of adjacent collapsed wing of the Hôpital Saint-François de Sales in the 2010 magnitude-7 Haiti Earthquake (not known if antenna suffered earthquake damage; photo courtesy of Ayhan Irfanoglu, Purdue University). Hospital communications depend on the functionality of antennae such as this.




Figure 6.4.7.6-3 Damage or movement of ballasted antennae was not observed on this rooftop in the 2010 magnitude-6.5 Eureka Earthquake (Photo courtesy of Maryann Phipps, Estructure).

Figure 6.4.7.6-4 The antenna with guy wires remained upright atop a collapsed building in the 2010 Haiti Earthquake (Photo courtesy of Eduardo Fierro, BFP Engineers). Even though some of the guy wires went slack, the antenna did not fall into the street.





The Federal Communications Commission (FCC) issues regulations for Over-the-Air Reception Devices to preempt restrictions on the size, mast height, or location of direct-to-home satellite dishes. For instance, Title 47 (Section 1.200) of Code of Federal Regulations which codifies the FCC regulations covers dishes less than 1 meter in diameter with a mast height less than 12 feet above the roofline. In addition, tenant or homeowner association agreements may have restrictions on the size or placement of antennae; check for local code or association requirements.

The antenna mast may be mounted in a variety of ways, for example to wood or metal stud walls, concrete or solid masonry walls (cells filled with concrete), hollow masonry block walls, freestanding poles, or to roof rafters or a concrete roof slab. Schematic details for installing the mast mounting bracket to a stud or concrete walls are shown in Figure 6.4.7.6-5.

Some mounting kits available on the internet provide hardware for strapping the antenna to a residential chimney. As unreinforced masonry chimneys are highly prone to earthquake damage as described in Section 6.3.7.1, antenna should not be mounted to unreinforced masonry chimneys. If the chimney is adequately reinforced, chimney mount details may be used for lightweight antennae.

Hardware and kits for non-penetrating ballasted mounts are also available for purchase. These kits often use standard sized concrete blocks for ballast. Use of multiple concrete blocks for ballast may be heavy enough to trigger the requirement for the equipment to have engineered anchorage. While these ballasted systems can reasonably be used in areas of low seismicity, they could potentially slide and damage roofing or wiring in areas of high seismicity.

Large or tall antennae need to be properly engineered for both wind and seismic loading. Tower antennae may be anchored with guy wires, or mounted to a specially designed frame. Positive attachments from the antenna to the supporting structure should be provided and one should check with the manufacturer to see if the antenna itself has been designed or tested for seismic loading since seismic forces at the roof elevation are typically much higher than at ground level.

Communications equipment used for essential facilities may need to be shake table tested and certified. Shake tables operated by the Pacific Earthquake Engineering Research Center (PEER) at UC Berkeley, MCEER at SUNY Buffalo, and others both perform testing of telecommunications network equipment in accordance with NEBS




Requirements: Physical Protection (NEBS, 2006), protocol to certify that the internal parts and electronic components can withstand seismic shaking.

As with any items mounted with exterior exposure, components and connectors should be corrosion resistant and roof or wall penetrations should receive flashing and sealant as appropriate.

Mitigation Examples

Figure 6.4.7.6-5 Antenna mast mounted to concrete wall surface at top floor of building (Photo courtesy of (Photo courtesy of Maryann Phipps, Estructure). Note that two wall brackets are used to resist moments produced by wind or seismic forces. This antenna is larger than most standard residential versions.




Figure 6.4.7.6-6 Antenna mast mounted to wood stud wall using blocking to clear eves (Photo courtesy of Cynthia Perry, BFP Engineers).




Mitigation Details

Figure 6.4.7.6-7 Details for wall-mounted communications antenna (ER).




Figure 6.4.7.6-8 Details for roof/slab mounted communications antenna (ER).





6.4.8 ELECTRICAL AND COMMUNICATIONS DISTRIBUTION EQUIPMENT

6.4.8.1 ELECTRICAL RACEWAYS, CONDUIT, AND CABLE TRAYS

This category covers electrical raceways, conduit, cable trays, and bus ducts. These items may be suspended from above or be floor-, chase-, wall- or roof-mounted.


Items may swing and impact structural or other nonstructural elements; they may fall and create electrical hazards.

Vulnerable locations include seismic separations; wall, floor, or roof penetrations; and attachments to rigidly mounted equipment.

Damage Examples

Figure 6.4.8.1-1 Unbraced suspended piping and conduit (Photo courtesy of Wiss, Janney, Elstner Associates).






Two trapeze anchorage details are shown. See Section 6.4.3.1 for additional pipe anchorage details; the same type of bracing is typically used for electrical distribution lines. Refer to FEMA 413 Installing Seismic Restraints for Electrical Equipment (2004) for general information on seismic anchorage of electrical equipment and to FEMA 414 Installing Seismic Restraints for Duct and Pipe (2004) for many different anchorage configurations for raceways, conduit and cable trays.

Several engineered seismic bracing systems are available and can be customized for most applications. This is particularly useful for large scale projects or essential applications.

Mitigation Examples

Figure 6.4.8.1-2 Rigid strut bracing provides restraint against earthquake forces perpendicular to the piping. Similar bracing is required in the direction parallel to the conduit (Photo courtesy of Maryann Phipps, Estructure).




Figure 6.4.8.1-3 Rigid strut bracing for trapeze supporting electrical conduit; conduit attached to trapeze with conduit clamp that provides lateral and longitudinal restraint (Photo courtesy of Maryann Phipps, Estructure).




Figure 6.4.8.1-4 Lateral and longitudinal rigid strut bracing for trapeze supporting electrical raceways (Photo courtesy of Maryann Phipps, Estructure).

Mitigation Details

Figure 6.4.8.1-5 Cable tray on braced trapeze (ER).





6.4.8 ELECTRICAL AND COMMUNICATIONS DISTRIBUTION EQUIPMENT

6.4.8.2 ELECTRICAL DISTRIBUTION PANELS

This category includes electrical distribution panels, either recessed or surface-mounted. Wall-mounted electrical panels have generally performed well in past earthquakes, in part due to their weight (typically less than 200 pounds), the ductility of the sheet metal cabinets, and the strength of the interconnected conduit which can serve as unintended bracing.


Panels may become dislodged and fall. Damage to distribution panels and the attached lines may create electrical hazards and

fire hazards.




Damage Examples

Figure 6.4.8.2-1 Dislodged panel board due to failure of hollow concrete block partition wall in the 1964 magnitude-9.2 Anchorage, Alaska earthquake (Photo courtesy of PEER Steinbrugge Collection, No. S2144).



This type of equipment can be supplied with shop welded brackets or predrilled holes for wall anchorage. For any new equipment, request items that can be supplied with seismic anchorage details.

See Section 6.4.7.1 for additional details. The wall mount detail shown is for a concrete wall; refer to FEMA 413 Installing Seismic Restraints for Electrical Equipment (2004) for additional information about anchoring to masonry or drywall and for general information on seismic anchorage of electrical equipment.




Mitigation Examples

Figure 6.4.8.2-2 Wall anchorage for electrical panel; standard strut anchored to wall studs and panel anchored to strut (Photo courtesy of Maryann Phipps, Estructure).




Mitigation Details

Figure 6.4.8.2-3 Free-standing electrical distribution panel (ER).





6.4.9 LIGHT FIXTURES

6.4.9.1 RECESSED LIGHT FIXTURES

This category covers recessed light fixtures that are part of a suspended ceiling grid. These may be lay-in fixtures in a suspended acoustic tile ceiling or recessed fixtures in other types of suspended ceilings such as gypsum board, plaster, or metal panels. Overhead light fixtures in a finished ceiling have often been damaged in past earthquakes; the fixtures may become dislodged from the ceiling or ceiling grid and fall unless they are tied to the grid and have independent support to the structure above.


Recessed fixtures supported by a suspended ceiling without independent safety wires to the structure above can become dislodged and fall. Fixtures with proper safety wires may fall from the grid and dangle from the safety wire but will not threaten occupants.

Unless secured to a properly braced ceiling grid, relative movement between the light fixture and the ceiling may damage the ceiling finishes, ceiling grid, wiring, or the light fixture. Heavy fixtures that are hung independently but not laterally braced may swing independent of the ceiling and damage the ceiling system.

Unsecured lenses and bulbs may fall independent of the fixture and cause damage below.

Most observed damage to recessed light fixtures in the U.S. has involved fixtures in suspended acoustic tile ceilings which do not have much inherent in-plane stiffness; damage to fixtures in gypsum board ceilings has been less common.




Damage Examples

Figure 6.4.9.1-1 Numerous fluorescent fixtures dangling from electrical conduit; installed without safety wires in unbraced suspended acoustical ceiling and damaged in the 2010 magnitude-7 Haiti Earthquake. Loose bulbs, lenses, ceiling panels, diffusers and ducts also on the floor (Photo courtesy of Ayhan Irfanoglu, Purdue University).




Figure 6.4.9.1-2 Overhead lights with four vertical hangers to the structure. Unbraced acoustic ceiling system was damaged beyond repair in the 2001 magnitude-8.4 Peru Earthquake but none of the diffusers or lights fell because they had independent supports. Ceiling was demolished prior to photo (Photo courtesy of Eduardo Fierro, BFP Engineers).




Figure 6.4.9.1-3 Light fixture without adequate independent support dangling along one edge from ceiling grid, damaged in the 1994 magnitude-6.7 Northridge Earthquake (Photo courtesy of Degenkolb Engineers).




Figure 6.4.9.1-4 Light fixture without independent support dangling from conduit as a result of the 1994 Northridge Earthquake (Photo courtesy of Degenkolb Engineers).





Requirements for recessed lighting fixtures may vary depending on requirements for the type of ceiling in which they are located. Recessed light fixtures may be found in any type of ceiling system. Requirements for suspended acoustic ceilings and suspended gypsum board ceilings are discussed below.

For requirements for recessed fixtures in suspended acoustic tile ceilings, ASCE 7-10, , Minimum Design Loads for Buildings and other Structures (ASCE, 2010), references ASTM E580, Standard Practice for Installation of Ceiling Suspension Systems for Acoustical Tile and Lay-in Panels in Areas Subject to Earthquake Ground Motions (ASTM, 2010); Section 4.4 covers conditions for ceilings weighing less than 2.5 psf in Seismic Design Category C and Section 5.3 covers ceilings weighing more than 2.5 psf in Seismic Design Category C and ceilings in Seismic Design Categories D, E and F. Per ASTM E580 Section 5.3 light fixture require the following:

o lights must be positively attached to the ceiling grid with a minimum of two attachment devices capable of resisting 100% of the fixture weight in any direction. This is not required if the light has independent vertical and lateral support.

o where the load carrying capacity of the cross runners is less than 16 lb/ft, supplementary hanger wires may be required for the ceiling grid. See discussion regarding the requirement for supplementary framing and supplementary hanger wires for the suspended ceiling grid under Section 6.3.4.1. Note also that intermediate duty or heavy duty grid is required for ceilings carrying light fixtures.

o For fixtures weighing less than 10 lb, provide one #12 safety wire connected from the fixture housing to the structure above; wire may be slack.

o For fixtures weighing from 10 lb to 56 lb, provide two #12 safety wires at diagonally opposite corners connected from the fixture housing (not the detachable end plates) to the structure above; wires may be slack.

o For fixtures weighing more than 56 lb, these must be supported directly from the structure above by approved hangers. If the ceiling bracing can provide lateral restraint for such fixtures, they should be positively attached to the ceiling grid as noted above but supported with not less than four taut #12 wires. This requirement is also often taken to apply to large 4’x4’ fixtures. Refer to Section 6.4.9.4 for heavy fixtures requiring independent vertical and lateral support.




For acoustic tile ceilings, California schools require safety wires or independent vertical support for each light fixture, positive attachment from the light fixtures to the ceiling grid, and bracing for the ceiling grid that is adequate to resist the lateral loading from the ceiling, lights, and diffusers. DSA IR 25-5 Metal Suspension Systems for Lay-in Panel Ceilings (California Department of General Services, 2009c) provides details for lights in suspended acoustic ceiling grids. The requirements in DSA IR 25-5 differ slightly from ASTM E580: California schools require two safety wires on all fixtures under 56 pounds; require all 4 ft x 4 ft fixtures have a slack #12 safety wire at each corner, even if the fixture weight is less than 56 lb; and for fixtures weighing more than 56 lb, require they be independently supported by not less than four taut #12 wires, and that these wires be capable of supporting four times the weight of the fixture.

Per ASCE 7-10, certain types of suspended ceilings with screw-attached gypsum board built at one level do not require special seismic details; these ceilings also do not require safety wires for light fixtures (see Section 6.3.4.3 for a discussion of exempt ceilings). The weight of recessed light fixtures in suspended gypsum board ceilings must be supported by main runners, supplementary framing supported by the main runners, or directly by the structure above. Neither the ceiling finish material nor the cross furring should be used to support light fixtures. The fixture should be positively attached with screws or other approved connectors to the ceiling grid. Requirements for California schools are in DSA IR 25-3 Drywall Ceiling Suspension Conventional Construction-One Layer (California Department of General Services, 2005b). For suspended gypsum ceilings built at multiple levels, or other types of heavy ceilings, seismic detailing and safety wires for lighting may be required; check applicable code provisions.

International Code Council Evaluation Service has published AC184, Acceptance Criteria for Attachment Devices for Recessed Lighting Fixtures (Luminaries) in Suspended Ceiling Systems (ICC-ES, 2006), with information on attachments of light fixtures to suspended ceiling grids. The website located at http://www.agi-seismic.com/code/ac184.html# provides footage of lighting fixture failures where the lights are attached only with tie wires. A discussion of issues related to the code design provisions and the requirement for positive attachments is also provided. In some instances, where approved seismic fixture clamps (SFC) are used to anchor the lighting to a properly braced ceiling grid, the independent tie wires are not required.

For existing construction where the ceiling grid is not adequately braced or not strong enough to provide lateral restraint for the lighting, splay wire bracing at each corner of the fixture can be used to provide horizontal restraint. Such bracing would also help


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prevent swinging lights from damaging the surrounding ceiling. At a minimum, such fixtures should be retrofit with independent safety wires to prevent them from falling.

Lenses and bulbs may require independent restraints to keep them from falling from the fixture.

For fire rated ceiling assemblies, only fixtures and attachments with an approved fire rating may be used. Check with the manufacturer for approved systems. Some fixtures may require lead shielding or a fire-rated enclosure; check local code provisions.

Do not attach lights to ducts, piping, or other nonstructural items in the ceiling plenum.

Mitigation Examples

Figure 6.4.9.1-5 Example of light fixture with only one safety wire attached; the Salt Lake City

schools require four wires for a fixture of this size and weight and also require tighter turns on the wire (Photo courtesy of Salt Lake City School District). Investigations in ceiling plenums often reveal missing wires.




Mitigation Details

Figure 6.4.9.1-6 Schematic plan of recessed lights in suspended acoustic ceiling (PR).




Figure 6.4.9.1-7 Recessed light fixture in suspended ceiling (fixture weight < 10 pounds) (PR).

Figure 6.4.9.1-8 Recessed light fixture in suspended ceiling (fixture weight 10 to 56 pounds)

(PR).






6.4.9.2 SURFACE-MOUNTED LIGHTING

This category covers surface-mounted light fixtures that are overhead in a finished ceiling. The term surface-mounted refers to a range of conditions; in some cases the fixture and housing are entirely below the ceiling surface, in other cases part of the housing is recessed above the bottom of the ceiling. Overhead fixtures may also be surface-mounted on a wall. Damage to overhead lighting has occurred frequently in past earthquakes; the fixtures become dislodged from the ceiling or ceiling grid and fall unless they are tied to the grid or have independent support to the structure above.


Surface lighting that is not equipped with independent safety wires may fall to the floor. Lighting with proper safety wires may fall from the ceiling and dangle from the safety wires but will not pose a safety risk to occupants.

Unless secured to a properly braced ceiling grid, relative movement between the light fixture and the ceiling may damage the ceiling finishes, ceiling grid, wiring, or the light fixture.

Unsecured lenses and bulbs may become dislodged and fall to the floor even where the fixture is restrained. This may occur with both ceiling and wall mounted surface lighting.

Most observed damage to light fixtures in the U.S. has involved fixtures in suspended acoustic tile ceilings which do not have much inherent in-plane stiffness; damage to fixtures mounted in or on gypsum board ceilings has been less common.




Damage Examples

Figure 6.4.9.2-1 Numerous failures of ceilings and lights were observed at the Concepción airport in the 2010 magnitude-8.8 Chile Earthquake. Photo shows surface-mounted fixture on wall that remained in place but the lens fell and the bulbs were dislodged (Photo courtesy of Rodrigo Retamales, Rubén Boroschek & Associates).




Figure 6.4.9.2-2 Overhead surface-mounted fixture anchored to underside of concrete slab damaged in the 2010 Chile Earthquake. Back of fixture housing remained anchored to the concrete slab above and the bulbs remained in place but the lens and sides of housing fell indicating that internal connections in the fixture were inadequate (Photos courtesy of Rodrigo Retamales, Rubén Boroschek & Associates).





As referenced in Section 13.5.6 of ASCE 7-10, Minimum Design Loads for Buildings and other Structures (ASCE, 2010), ASTM E580, Standard Practice for Installation of Ceiling Suspension Systems for Acoustical Tile and Lay-in Panels in Areas Subject to Earthquake Ground Motions (ASTM, 2010), requires that surface-mounted fixtures in a suspended acoustic ceiling shall be attached to the ceiling suspension system with positive clamping devices that completely surround the supporting members. Safety wires are required between the clamping device and the adjacent ceiling hanger or to the structure above. The weight of the fixture shall not exceed the design carrying capacity of the supporting members. One, two, or four safety wires are required from the fixture housing to the structure above. These requirements for safety wires are the same as for recessed fixtures and are as follows:

o For fixtures weighing 10 pounds or less, provide one slack safety wire o For fixtures weighing between 10-56 pounds, provide two slack safety wires at

diagonally opposite corners o For fixtures weighing more than 56 pounds, provide independent support to the

structure above. For many fixtures, this can be satisfied with 4 taut wires. Heavy or specialty fixtures, such as operating room lights in a hospital, may require engineered support and bracing details such as those shown in Section 6.4.9.4.

For suspended acoustic ceilings, ASTM E580 has other requirements related to the grid itself. Intermediate or heavy duty ceiling grid is required where lights will be supported and supplementary ceiling framing and supplementary hanger wires may be required adjacent to fixtures. Lateral restraint for lighting is assumed to be provided by the ceiling grid so the design of the grid must account for the overall weight of all the attached lighting and mechanical registers. See Section 6.3.4 for additional information regarding ceilings.

Per ASCE 7-10, certain types of suspended ceilings with screw-attached gypsum board built at one level do not require special seismic details; these ceilings also do not require safety wires for light fixtures (see Section 6.3.4.3). The weight of surface-mounted fixtures must be supported by main runners, supplementary framing supported by the main runners, or directly by the structure above. Neither the ceiling finish material nor the cross furring should be used to support light fixtures. The fixture should be positively attached with screws or other approved connectors to the ceiling grid. Requirements for California schools are in DSA IR 25-3 Drywall Ceiling Suspension Conventional Construction-One Layer (California Department of General




Services, 2005b) and read “Surface-mounted fixtures shall be attached to a main runner with a positive clamping device made of material with a minimum of 14 gage. Rotational spring clamps do not comply.” For suspended gypsum ceilings built at multiple levels, or other types of heavy ceilings, seismic detailing and safety wires may be required; check applicable code provisions.

International Code Council Evaluation Service has published Acceptance Criteria AC184 (ICC-ES, 2006) with information on attachments of light fixtures to suspended ceiling grids. The website located at http://www.agi-seismic.com/code/ac184.html provides footage of lighting fixture failures where the lights are attached only with tie wires. A discussion of issues related to the code design provisions and the requirement for positive attachments is also provided. In some instances, where approved seismic fixture clamps are used to anchor the lighting to a properly braced ceiling grid, independent tie wires are not required. Check for pre-approved details for such devices in the applicable jurisdiction.

For surface-mounted fixtures in existing buildings where the ceiling grid is unbraced, such fixtures should be retrofit with safety wires at a minimum to prevent them from falling. Providing independent lateral bracing for the fixture may reduce the potential for the light to damage an existing unbraced ceiling.

For fire rated ceiling assemblies, only fixtures and attachments with an approved fire rating may be used. Check with the manufacturer for approved systems. Some fixtures may require lead shielding or a fire-rated enclosure; check local code provisions.

Do not attach lights to ducts, piping, or other nonstructural items in the ceiling plenum.


http://www.agi-seismic.com/code/ac184.html�



Mitigation Examples

Figure 6.4.9.2-3 Independent vertical support for surface-mounted light fixture in suspended gypsum board ceiling located in California hospital. Eye hook and slack wire from fixture is tied to concrete slab above. The rigid bracing in the photos is attached to the ceiling grid, not the light fixture (Photos courtesy of Maryann Phipps, Estructure).




Mitigation Details

Note: Surface-mounted fixtures shall be attached to ceiling suspension systems with screws or positive clamping devices. Safety wires (1, 2 or 4) are required in suspended acoustic lay-in tile ceilings depending on the size and weight of the fixture; safety wires may be required in other ceiling types as well. Weight of fixture shall not exceed design carrying capacity of the supporting members; supplementary framing and additional hanger wires may be required. Gypsum board ceiling shown in details; although some gypsum ceilings may be exempt from the seismic detailing requirements and may not require the safety wires shown.

Figure 6.4.9.2-4 Surface-mounted fixture below suspended ceiling grid (PR).






6.4.9.3 PENDANT LIGHT FIXTURES

This section covers pendant light fixtures, chandeliers, ceiling fans, and other similar suspended items.


Suspended items can swing and impact building elements or adjacent equipment, resulting in damage to the fixture or damage to the surrounding items. Lenses, bulbs, or decorations may come loose and fall and endanger occupants.

If the item is not sufficiently well supported, or if the item is connected only to ceiling framing which is damaged in an earthquake, the entire fixture may become dislodged and fall. Where a string of fixtures are attached end to end, the failure of one fixture can overload the supports for the adjacent fixtures leading to progressive collapse.




Damage Examples

Figure 6.4.9.3-1 Failure of a strip of pendant light fixtures at Dawson Elementary School library as a result of the 1983 magnitude-6.4 Coalinga Earthquake. Note that in this case the support stems failed at the ceiling connection and the stem came down with the lights (Gary McGavin, NGDC, 2009).




Figure 6.4.9.3-2 Failure of pendant light fixtures at Northridge Junior High School as a result of the 1994 Northridge Earthquake. In this example, the support stem failed at the fixture connection and the stem is still attached at the ceiling (Photo courtesy of Gary L. McGavin).




Figure 6.4.9.3-3 Failure of pendant light fixture in the 2010 magnitude-7 Haiti Earthquake; stem of fixture broke and conduit pulled loose (Photos courtesy of Eduardo Fierro, BFP Engineers).





All light fixtures should have positive attachments to the structure to prevent falling hazards. Per ASTM E580, Standard Practice for Installation of Ceiling Suspension Systems for Acoustical Tile and Lay-in Panels in Areas Subject to Earthquake Ground Motions (ASTM, 2010), pendant fixtures in suspended ceilings must be supported directly from the structure above by no less than #9 gauge wire or an approved alternate support. The ceiling suspension system shall not provide any direct support and rigid conduit is not permitted for the attachment of fixtures.

For California schools, DSA IR 25-5, Metal Suspension System for Lay-in Panel Ceilings (California Department of General Services, 2009c), requires the following: “Support pendant mounted light fixtures directly from the structure above with hanger wires or cables passing through each pendant hanger and capable of supporting two (2) times the weight of the fixture. A bracing assembly, (see Section 6.3.4.1), is required where the pendant hanger penetrates the ceiling. Special details are required to attach the pendant hanger to the bracing assembly to transmit horizontal force. If the pendant mounted light fixture is directly and independently braced below the ceiling, i.e. aircraft cables to walls, then brace assembly is not required above the ceiling.” See DSA IR 16-9, Pendant Mounted Light Fixtures (California Department of General Services, 2009a), for additional requirements for pendant mounted fixtures.

For older installations, provide a safety chain or cable for the fixture and provide restraints for lenses and bulbs that can readily fall from the fixture.

If the fixture can impact other items and cause failure of an essential component, or if impact can create a falling hazard, then seismic restraints that limit the range of motion of the fixture should be installed.




Mitigation Details

Figure 6.4.9.3-4 Pendant light fixture (NE).






6.4.9.4 HEAVY LIGHT FIXTURES

This category covers heavy or special purpose overhead light fixtures that require engineered support details. This includes fixtures such as hospital operating room lights which also have movable arms. Damage to overhead lighting has occurred frequently in past earthquakes; special purpose lighting has additional issues in that the fixture may have internal joints and movable parts which may not have not been designed for seismic loading.


Heavy or special purpose lighting can fail at the attachment to the structure above if not adequately designed and the fixture could fall and injure occupants. Overhead braces may buckle and the fixture will be misaligned or fail to function as intended.

Fixtures with multiple parts or movable arms may fail at the connections or arm joints; bulbs or lenses may fall.

Bracing for the light fixture and surrounding ceiling should be coordinated to allow for relative movement. If the ceiling surround has not been designed with appropriate clearance around the fixture, the ceiling may be damaged at the interface with the light.




Damage Examples

Figure 6.4.9.4-1 Operating room lights undamaged although hospital evacuated due to collapse of adjacent wing in the 2010 magnitude-7 Haiti Earthquake. Fixture anchored to underside of concrete slab (Photo courtesy of Ayhan Irfanoglu, Purdue University).


Per ASTM E580, Standard Practice for Installation of Ceiling Suspension Systems for Acoustical Tile and Lay-in Panels in Areas Subject to Earthquake Ground Motions (ASTM, 2010), where the weight of a fixture in a suspended acoustic ceiling is greater than 56 pounds, the fixture must be supported directly from the structure above by approved hangers. Where the fixture is over 56 pounds but light enough so that the lateral restraint for the fixture can be provided by the lateral bracing for the ceiling grid, these fixtures must also be positively attached to the ceiling grid with a minimum of two attachment devices capable of resisting 100% of the fixture weight in any direction. This condition is covered in Sections 6.4.9.1 and 6.4.9.2.

Lights covered here are those heavier than can be safely supported by the suspended ceiling grid and require independent engineered supports for both vertical and lateral




loads. In addition, special purpose lighting with movable parts may require more fixity than provided by the ceiling grid and require independent support and bracing to maintain position and satisfy operational tolerances.

Note that fixed lighting provides an obstruction for a suspended ceiling system. For suspended acoustic ceilings in Seismic Design Category D, E & F, ASTM E580 requires that the ceiling surrounding such a fixture must be detailed as if it were a perimeter closure that must allow the required clearances by use of suitable closure details; this typically would require a minimum ¾” clearance around the fixture.

When purchasing heavy light fixtures that have multiple part or movable arms, check with the manufacturer for seismically qualified fixtures. Certified fixtures are required for hospitals or essential facilities that must remain functional following an earthquake per Section 13.2.2.1 of ASCE 7-10, Minimum Design Loads for Buildings and Other Structures (ASCE, 2010).




Mitigation Examples

Figure 6.4.9.4-2 Engineered support and bracing are required for heavy operating room lights. The arms, joints, lenses and bulbs must be capable of resisting seismic forces. Hospital fixtures require certification. Photo also shows surface mounted fluorescent fixtures in a suspended gypsum board ceiling; each of these requires independent safety wires to the structure above; see Section 6.4.9.2 (Photo courtesy of Maryann Phipps, Estructure).




Figure 6.4.9.4-3 Engineered support and bracing for operating room lights located in California hospital. Steel plate has predrilled holes to receive fixture attachments (Photo courtesy of Maryann Phipps, Estructure).




Mitigation Details

Figure 6.4.9.4-4 Details for supporting heavy light fixture directly from structure (ER).




Figure 6.4.9.4-5 Details for supporting heavy light fixture directly from structure (ER).





6.4.10 ELEVATORS AND ESCALATORS

6.4.10.1 HYDRAULIC ELEVATORS

Hydraulic elevators consist of relatively simple mechanical systems but failure of any of the component parts could disable the functionality of the entire system. These elevators are typically limited in height since they require a cylinder beneath the elevator equal to the height of the elevator cab’s vertical travel.


The primary components of the hydraulic elevator system are the elevator cab, cab guides, doors and door mechanism, piston, cylinder, fluid reservoir, hydraulic fluid, rotary pump, valve, solenoid switch, and electrical control panel. The system may be tied to a seismic switch or a smoke detector which would facilitate safe shutdown in the event of an earthquake or fire. Any of these components could be damaged if not properly restrained. Other possible failures are: misalignment of cab guides or cylinder, deformed door frames impeding the operation of doors, failure of door rails, leakage of hydraulic fluid, damaged pump.

According to survey responses collected by the Division of Occupational Safety and Health Elevator, Tramway, and Ride unit, following the 1994 Northridge Earthquake 897 hydraulic elevators suffered damage such as leaks in underground feed lines, separated pipes, and failed gaskets and fittings. In addition, numerous guide rails were bent and several cars came out of rails. Tie downs on several oil tanks failed and hold-down bolts sheared and pulled out.

In addition to property damage, passengers may become trapped in the cab following an earthquake and may need to await extraction by qualified elevator technicians.


All components of the hydraulic system need to be restrained, anchored or detailed to accommodate movement to prevent damage in an earthquake. The system must be designed to accommodate the anticipated inter-story drift over the height of the elevator travel and the depth of the cylinder below. Components such as cab guides,




door frames, and cylinder supports must all be detailed to accommodate lateral deformations. All mechanical and electrical equipment, sensors, piping, tanks, valves, and guides need to be properly anchored or restrained.

All elevators should be inspected by qualified elevator technicians following an earthquake. Elevators should have a seismic switch or safety features that allow for safe shutdown in an earthquake.

Elevator safety is governed by the prescriptive requirements in ASME A17.1/CSA B44, Safety Code for Elevators and Escalators (ASME, 2007a) a document that is continually evolving to reflect new elevator technologies. In addition, ASME A17.7/B44.7, Performance Based Code for Elevator Safety (ASME, 2007b), is the next step in the evolution of elevator safety codes in the United States and Canada. Local or state jurisdictions may have other elevator requirements.

The internet provides information regarding hydraulic elevators. A few websites are linked below:

o The website http:science.howstuffworks.com/elevator1.htm describes the workings of hydraulic elevators and provides links to other resources

o Jobsite safety in the elevator industry is discussed on http://safety.elevator-world.com/disaster.htm

o The websites of the Elevator and Escalator Safety Foundation, http://eesf.org/, and major elevator suppliers such as The Otis Elevator Company and Schindler Elevators provide additional resources.

o The National Elevator Industry, Inc. has other resources including a discussion of the performance based code for elevator safety (http://www.pbc-elevators.com/).


http://science.howstuffworks.com/elevator1.htm�

http://safety.elevator-world.com/disaster.htm�


http://eesf.org/�

http://www.pbc-elevators.com/�




Mitigation Details

Figure 6.4.10.1-1 Schematic view of hydraulic elevator (ER).






6.4.10.2 TRACTION ELEVATORS

Traction elevators have made high rise construction possible. These systems are continually evolving to achieve faster speeds, smoother and quieter operations. Currently there are geared traction elevators, gearless traction elevators, and “machine-roomless” elevators that use flat belts instead of steel cable. Traction elevators are complex mechanical systems that have many moving parts and electronic components and failure of any of the components could disable the functionality of the entire system. Maintaining limited functionality of some elevators following an earthquake is critical for continued operations of essential facilities or the evacuation of hospital patients.


The primary components of the traction elevator system are the elevator cab, counterweight, cab guide rails, counterweight guide rails, guide rail support brackets, electric motor, electrical control panel, ropes, sheaves, safety braking mechanisms, door mechanisms, and a shock absorber at the bottom of the shaft. The system may be tied to a seismic switch or a smoke detector which would facilitate safe shutdown in the event of an earthquake or fire. Any of these components could be damaged if not properly restrained. Other possible failures are: misalignment of cab guides, deformed door frames impeding the operation of the doors, failure of door rails, misalignment of the cab or counterweight, and damage to the mechanical or electrical equipment. Failures of counterweights can result in falling hazards if the subweights can come loose of the counterweight assembly.

According to survey responses collected by the Division of Occupational Safety and Health Elevator, Tramway, and Ride unit, following the 1994 Northridge earthquake, the following issues were observed:

o Water damage-sprinkler pipes pulled apart flooding machine rooms and pits causing water on top of cars, damage to door operators and door detectors, and soaking car processors and car station. Several oil buffers had to be rebuilt.




o Falling debris in hoistways, falling plaster, loose concrete blocks, broken glass resulted in damaged door interlocks and misalignment of hatch switches and bent fascias.

o Building settlements bent elevator guide rails; structural damage, loose and bent divider beams shifted guide rails and bending support brackets.

o 3,528 cabled elevators were removed from service by a seismic protective device. 710 devices did not operate as intended. Some devices were located in the elevator pits which were flooded.

o 968 electric cabled elevators sustained earthquake damage. o 2 minor injuries were reported, one of which was sustained by a fireman trying

to open hoistway doors. o 39 elevators required rescue. o 57 instances were reported where "unauthorized persons" reset earthquake

devices. Fortunately, only 5 elevators sustained additional damages. o 688 counterweights came out of guide rails. 8-1b rails were inadequate even

with additional intermediate guide rail bracket retrofit. Several counterweight frames were twisted and bent with a few dislodged subweights. Some counterweight roller guide shoe mountings disintegrated.

Following the 2010 Chile Earthquake, it was reported that 50%-80% of hospital elevators were damaged. In a number of locations, patients had to be carried down many flights of stairs, often cluttered with fallen debris, in order to evacuate them to safety. The most common damage was due to unrestrained movement of the counterweights, resulting in damage to the guide rails. Movement of unrestrained mechanical equipment was another problem. One security camera at a military hospital in Santiago, Chile captured a sequence through the open door of an empty elevator cab where the counterweights derailed and then the subweights came crashing down on top of the cab. (Source: Bill Holmes, March 2010).

In addition to property damage, passengers may become trapped in the cab following an earthquake and may need to await extraction by qualified elevator technicians.




Damage Examples

Figure 6.4.10.2-1 Damage to traction elevator in Chillán in the 2010 magnitude-8.8 Chile Earthquake (Photo courtesy of Gilberto Mosqueda, SUNY Buffalo). The unanchored sheaves and motor above the 6th floor slid nearly off the housekeeping pad. The counterweight guide rails are bent due to impact with the counterweights. The guide rail support brackets have horizontal slots, but the bolt went through a welded tab (photo at lower right) and pulled out of the wall.




Figure 6.4.10.2-2 Derailed car roller assembly of the guide rail at the Santiago airport in the 2010 Chile Earthquake (Photo courtesy of Gilberto Mosqueda, SUNY Buffalo). The three rollers are supposed to travel along three sides of the stem of the T-shaped steel guide rail.




Figure 6.4.10.2-3 Glazing failures caused additional hazards at Santiago airport elevator in the 2010 Chile Earthquake (Photo courtesy of Antonio Iruretagoyena, Rubén Borsochek & Associates).




Figure 6.4.10.2-4 Unrestrained movement of the counterweights damaged the counterweight assembly and bent the counterweight guide rails; over half the subweights dropped onto the top of the cab and damaged the cab framing in the 2010 Chile Earthquake (Photo courtesy of Rodrigo Retamales, Rubén Borsochek & Associates).




Figure 6.4.10.2-5 Anchor bolt failure of the elevator generator set due to inadequate edge distance for the bolts at the Los Angeles Regional Public Hospital in the 2010 Chile Earthquake (Photo courtesy of Bill Holmes, Rutherford & Chekene).


All of the components of the traction system need to be restrained, anchored, or detailed to resist lateral forces in all directions and accommodate seismic movement. The system must be designed to accommodate the anticipated inter-story drift over the height of the elevator travel. Guide rails and door frames must all be detailed to accommodate lateral deformations. All of the mechanical and electrical equipment, sensors, and guides need to be properly anchored or restrained.

All elevators should be inspected by qualified elevator technicians following an earthquake. Elevators should have a seismic switch or safety features that allow for safe shutdown in an earthquake.

Elevator safety is governed by the prescriptive requirements in ASME A17.1/CSA B44 Safety Code for Elevators and Escalators (2007a), a document that is continually evolving




reflect new elevator technologies. In addition, ASME A17.7/CSA B44.7, Performance Based Code for Elevator Safety (ASME, 2007b), is the next step in the evolution of elevator safety codes in the United States and Canada. Local or state jurisdictions may have other elevator requirements.

As an example of state jurisdictions, the California Office of Statewide Health Planning and Development (OSHPD) provides special requirements for elevators in California hospitals, such as Title 24, Section 3007. These include requirements for a seismic switch connected to the essential electrical system, a visible or audible alarm, the ability to function at a “go slow” speed of not more than 150 feet per minute until the elevator can be inspected, and an additional sensor that will disable the elevator if the governor tail sheave is dislodged. For these systems, the seismic anchorage, guards and switches all need to be inspected annually.

The internet provides a resource of information regarding elevators. A few websites are linked below:

o The website http:science.howstuffworks.com/elevator1.htm describes the workings of a traction elevator and provides links to other resources

o Jobsite safety in the elevator industry is discussed on http://safety.elevator-world.com/disaster.htm

o The websites of the Elevator and Escalator Safety Foundation, http://eesf.org/, and major elevator suppliers such as The Otis Elevator Company and Schindler Elevators provide additional resources.

o The National Elevator Industry, Inc. has other resources including a discussion of the performance based code for elevator safety (http://www.pbc-elevators.com/).


http://science.howstuffworks.com/elevator1.htm�



http://eesf.org/�





Mitigation Examples

Figure 6.4.10.2-6 Small “machine-roomless” traction elevator with flat belts at the Academy of Sciences, San Francisco, California (Photos courtesy of Eduardo Fierro, BFP Engineers). Clockwise: Overview of elevator at roof; view of guide rails and sheaves; top of cab showing belts; view down shaft at belts, counterweight, guide rails and guide rail brackets.




Mitigation Details

Figure 6.4.10.2-7 Schematic view of geared traction elevator system (ER).






6.4.10.3 ESCALATORS

Escalators typically span between two floors, and although most escalators run in a straight line, spiral escalators are found in some locations. The failure of any of the component parts of the escalator or escalator equipment could disable the functionality of the system.

TYPICAL CAUSES OF DAMAGE The primary components of an escalator system are the steps, chain, inner rail, chain

guide, drive gear, handrail, handrail drive, electric motor, and electrical control panel. These components are often supported by a truss that spans between the floors. Any of these components could be damaged if not properly detailed or restrained; failure of any of the component parts could disable the system.

Escalators, like stairs, may form a strut or brace between adjacent floors unless they are detailed so the system will accommodate inter-story drift. Damage could occur to the skirt, landing plate or other components not detailed to accommodate either an extension or shortening of the distance between the two landings.

According to survey responses collected by the Division of Occupational Safety and Health Elevator, Tramway, and Ride unit, 65 escalators were damaged in the 1994 Northridge earthquake. It was reported that escalators came off upper supports, and several truss support angles had their bolts sheared off where one truss actually dropped. Glass came out of its supports and shattered, handrails collapsed. In addition, numerous deckboards, skirts and newels were damaged.




Damage Examples

Figure 6.4.10.3-1 Extensive nonstructural damage resulted in the closure of Concepción airport in the 2010 magnitude-8.8 Chile Earthquake; both the stair and escalator were cordoned off to limit access to the upper level although there was no visible damage to the escalator (Photo courtesy of Rodrigo Retamales, Rubén Boroschek & Associates).





Each of the components of an escalator system need to be detailed to accommodate movement, or restrained and anchored to prevent damage in an earthquake. The system must be designed to accommodate the anticipated inter-story drift between the two connected floors. Where a truss is used to span between the two floors, the bearing seats should allow movement at one or both ends. Components such as the rail supports, handrails, landing plates, and skirts must be detailed to accommodate lateral deformations. All of the mechanical and electrical equipment needs to be properly anchored or restrained.

Escalators have traditionally been designed to run continuously, whether they are in use or not. Some more energy efficient escalators operate on an intermittent basis and are triggered by the presence of passengers but otherwise are in a standby idle mode.

All escalators should be inspected by qualified personnel following an earthquake. Unlike elevators, escalators typically function as a usable stair when they are not operating and could be used to facilitate evacuation following an earthquake.

Elevator and escalator safety is governed by the prescriptive requirements in ASME A17.1, Safety Code for Elevators and Escalators (ASME, 2007a), a document that is continually evolving to reflect new elevator and escalator technologies. Local or state jurisdictions may have other elevator and escalator requirements.

The internet provides information regarding escalators. Websites such as http://science.howstuffworks.com/transport/engines-equipment/escalator.htm describe the workings of escalators and provide links to other resources

Some escalator models are offered with a seismic option; check for appropriate equipment before purchasing a new escalator.


http://science.howstuffworks.com/transport/engines-equipment/escalator.htm�



Mitigation Details

Figure 6.4.10.3-2 Schematic view of escalator (ER).





6.4.11 CONVEYORS

6.4.11.1 CONVEYORS

Material handling conveyors come in all shapes and sizes from the conveyor belt at the grocery store checkout line, the clothing conveyor at the dry cleaner’s, assembly line conveyors in clean rooms, airport baggage handling conveyors, to large industrial conveyors. They are used for many purposes, such as shipping, packaging, assembling, and manufacturing. The conveyors may be horizontal, inclined, hinged, straight, curved, spiral, screw, fixed or on wheels. Tall, inclined, or overhead systems may be a falling hazard; systems critical to facility operations may be important for post-earthquake functionality.

TYPICAL CAUSES OF DAMAGE Unanchored conveyors may slide and impact other items, tall or inclined conveyors may

overturn, overhead conveyors or components may become dislodged and fall. Conveyors not designed for seismic forces may have damage to the component parts and connectors. Unrestrained conveyor motors and related equipment may be damaged and fall.

Properly anchored conveyors may remain in place but the contents may fall. For tall or overhead conveyors, this could be a falling hazard resulting in injury and damage to materials or merchandise.

The conveyor may shift and exceed the alignment tolerances and not be functional until repaired or realigned.




Damage Examples

Figure 6.4.11.1-1 Misalignment between rice storage hopper and conveyor following the 2010 magnitude-8.8 Chile Earthquake (Photo courtesy of Rodrigo Retamales, Rubén Boroschek & Associates). Where various system components interface with a conveyor, the seismic restraints for the various parts should be coordinated to maintain alignment following an earthquake.




Figure 6.4.11.1-2 Damage to industrial conveyor used to feed grain silos in the 2010 Chile Earthquake (Photo courtesy of Eduardo Fierro, BFP Engineers).




Figure 6.4.11.1-3 Damage to industrial coal conveyor on jetty in southern Peru in the 2001 magnitude-8.4 Peru Earthquake (Photos courtesy of Eduardo Fierro, BFP Engineers). Conveyor was well anchored along entire length but detailing at the seismic joint between the jetty and platform did not allow sufficient movement, resulting in misalignment at end of conveyor and damage to the supports as shown at lower left. Approximately 10% of the rollers fell; these were held in place with friction fittings and did not have positive connections.





Conveyor systems and the associated motors, control systems, and control panels should be restrained or anchored to prevent earthquake damage. If life safety is the primary concern, tall or overhead components should be restrained to reduce falling hazards. If the conveyor is critical to continued operations, or the conveyed materials hazardous or particularly valuable, the system should be engineered to assure continued operations and the safety of the materials. In this case, the anchorage or restraints for interconnecting parts should be coordinated to maintain alignment tolerances following an earthquake.

There are various conveyor mechanisms including belt driven, chain driven, gravity rollers, chain driven rollers, and flex link conveyors. Conveyors may be supplied with leveling feet which may not be sufficiently robust unless they have been designed for seismic loading. Floor to floor conveyors must be detailed the same as for stairs or escalators and be able to accommodate the anticipated inter-story drift. Where long conveyors are variously suspended, wall-mounted, or floor-mounted, the layout of the supports and restraints should consider the relative motion of the various attachment points. Special detailing is required where conveyors cross building separations or seismic joints.

Some conveyors come supplied with predrilled base plates at each leg; these should be anchored to the floor slab. Existing conveyor platforms could be strengthened with transverse or longitudinal bracing if they have not been designed for seismic loading; clip angles could be used to anchor the legs to the floor. Check with the manufacturer prior to modifying existing equipment as equipment warranties may be affected.

Where conveyed materials are hazardous or valuable, it may be prudent to devise guiderails or side restraints of some type to prevent the materials from falling off the conveyor in the event of an earthquake. Such restraints would have to be designed so that they do not to interfere with normal operations.




Mitigation Details

Figure 6.4.11.1-4 Anchorage details for small material handling conveyor (ER).




6.5 FURNITURE, FIXTURES, EQUIPMENT AND CONTENTS

6.5.1 STORAGE RACKS

6.5.1.1 LIGHT DUTY SHELVING

This category includes light duty shelving units and sheet metal storage cabinets. These items are typically tall and narrow and may be heavily loaded.


Shelving units may slide or overturn and the contents may become dislodged or fall. Where there are rows of freestanding or poorly anchored shelves, the failure of a few may result in progressive collapse of many. Broken bottles, spilled chemicals, mixed or damaged inventory are often the result of the failure of storage or display units.

Mobile storage carts may roll, overturn, or impact other items. Stored contents may become dislodged or fall.

Damage to contents or inventory that has fallen from shelving can be costly to repair or replace and may result in substantial business interruption.




Damage Examples

Figure 6.5.1.1-1 Collapse of row of unanchored freestanding shelving units containing spare parts at an electric power plant in Port-au-Prince in the 2010 magnitude-7 Haiti Earthquake (Photo courtesy of Eduardo Fierro, BFP Engineers).




Figure 6.5.1.1-2 Unanchored storage shelving slid nine inches without falling but contents scattered in the 2001 magnitude-8.4 Peru earthquake; unit lifted to original position prior to photo (Photo courtesy of Eduardo Fierro, BFP Engineers).


Permanent floor-supported shelving or storage cabinets over 6 ft tall must be designed as architectural components per ASCE 7-10, Minimum Design Loads for Buildings (ASCE, 2010). Bracing and anchorage for these units should be designed considering the weight of the unit and weight of shelved contents.

For sheet metal cabinets or shelving, anchor units to floor, tie back-to-back units together, strap rows of units together across the top, or anchor units to an adjacent wall. Light duty steel storage racks may additionally require cross bracing.

See Section 6.5.6.1 for recommendations regarding edge restraints and arrangement of shelf-mounted items. Do not locate cabinets or racks adjacent to doors or exits if their failure would block the exit.




Any connections to stud walls must engage the structural studs. Stud walls and partitions may not have adequate lateral capacity to support many shelving units; engineering may be required. Where items are anchored to heavy partitions, the bracing or anchorage of these partitions to the structure above must also be checked for adequacy considering the seismic loads imposed by all anchored items.

The details shown are intended for light duty units; heavy duty units with large loads may require engineering. See FEMA 460, Seismic Considerations for Steel Storage Racks Located in Areas Accessible to the Public (2005), for additional information on the performance of industrial storage racks. Some racks are available with enhanced seismic performance; check other resources, such as the internet for additional options.

Mitigation Examples

Figure 6.5.1.1-3 Mobile carts restrained at base with clip angles anchored to the floor and removable eyebolts attached from each cart to the angles (Photo courtesy of Maryann Phipps, Estructure).




Figure 6.5.1.1-4 Alternate restraint at base of mobile shelving unit (Photo courtesy of Maryann Phipps, Estructure).

Figure 6.5.1.1-5 Fixed base shelving units anchored with optional seismic base plate offered by manufacturer (Photo courtesy of Maryann Phipps, Estructure).




Figure 6.5.1.1-6 Mobile cart restrained at base with removable angles and eyebolts. Back-to-back units are interconnected (Photo courtesy of Maryann Phipps, Estructure).




Figure 6.5.1.1-7 Fixed base shelving units anchored directly to concrete slab through base plate (Photo courtesy of Maryann Phipps, Estructure).




Figure 6.5.1.1-8 Mobile shelving unit restrained by connection to strut fastened to full height metal studs (Photo courtesy of Maryann Phipps, Estructure).




Mitigation Details

Figure 6.5.1.1-9 Light duty shelving (NE, ER).


6.4 MECHANICAL, ELECTRICAL, AND PLUMBING COMPONENTS …€¦ · 6.4 MECHANICAL, ELECTRICAL, AND...

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