Specifying Seismic. Ensuring security for suspended systems. Increasingly, building design and implementation teams assume

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1 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.

2 Figure 1 SDC A B C D E and F Meaning Very small seismic vulnerability Low to moderate seismic vulnerability Moderate seismic vulnerability High seismic vulnerability 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 components such as suspended ceilings where responsibilities are assigned to multiple team members. Even minor earthquakes in well-designed buildings can cause substantial damage. Ceilings are important non-structural components vulnerable to earthquake damage. During a seismic event, damage can occur at the perimeter when the vibration period of acoustical ceilings is significantly different than the building structure and other nonstructural components such as non-load-bearing partition walls. This can compromise structural integrity at the perimeter, increasing ceiling motion and potentially leading to total failure of the acoustical ceiling. Ceilings with heavy lighting fixtures may be susceptible to damage around the fixture, causing light fixtures to fall into the occupied space. The consequences include loss of operation, blocked egress, and life-safety hazards. Suspended ceilings Suspended, acoustical, lay-in panel ceilings have been the preferred method for concealing HVAC, power, and signal distribution equipment in commercial buildings since the 1950s. The interconnected ceiling systems typically consist of a metal grid comprising cross-tees and main runners. The latter are suspended by hanger wires from the structure above, and wall channels or angles support the perimeter. Panels are used in concealed plenum designs to hide the visible structure and other equipment. In open plenums, panels are not used. Figure IBC ASCE 7-05 CISCA Seismic Zones 0 2 & IBC ASCE 7-10 Snap-up systems and similar lay-in panels, hide the suspension grid, HVAC, and other equipment. They also provide very tight joints, and can offer a high degree of security. The strength of snap-up systems makes them reliable for challenging interior designs and exterior applications. Ceiling manufacturers are continually developing cost-effective products to accommodate local and national building codes, performance requirements, and facility operations. Wherever a ceiling is specified, it is essential to review: life-safety performance (including fire and seismic requirements); acoustic performance (including noise reduction coefficients [NRCs]); wind-load performance (including positive and negative wind loads); humidity resistance; sustainability considerations (which include recycled content composition, volatile organic compounds [VOCs] in finishes, and end-of-life recycling); durability and longevity (including corrosion resistance); and accessibility and low maintenance. For frequently accessed plenum areas, suspension ceilings with snap-up torsion spring panels allow maintenance staff access without completely taking out the panel. The connection s strength to the suspension system enables torsion spring panels to be effective in areas concerned with seismic activity.

3 Figure 3a Description of changes from 2009 IBC to 2012 IBC Reference Section ASCE (2) General 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 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 (primarily for main runner coupling tests). For the ceiling system connection/splice test, three replicate samples must group within 10 percent of the mean. If not, three additional tests must be run, dropping high and low values. The average of the remaining four test results must group within 10 percent of the mean; if not, the lowest value of the six tests becomes the controlling value. Perimeter wall angles and channels are considered aesthetic closures unless specifically designed as part of the structural system. Surface-mounted light fixtures: must be attached to ceiling grid system with positive clamping devices; and safety wires are required. Light fixtures weighing greater than 25.4 kg (56 lb) must be directly supported from the structure above by approved hangers. Please note: approved hangers were added. Pendant-hung light fixtures must be supported from the structure above with 9-gauge wire or approved support. Rigid conduit is not allowed for the attachment of light fixtures. Flexible sprinkler hose fittings and other mechanical services (e.g. ceiling-mounted air terminals) weighing less than or equal to 9.07 kg (20 lb) must be positively attached to the main runners or cross-tees. Flexible sprinkler hose fittings and other mechanical services (e.g. ceiling-mounted air terminals) weighing more than 9.07 kg, but less than or equal to 25.4 kg, must have two 12-gauge safety wires in addition to being positively attached to the main runners or cross-tees. Flexible sprinkler hose fittings and other mechanical services (e.g. ceiling-mounted air terminals) weighing more than 25.4 kg must be directly supported from the structure above. Seismic codes U.S. cities and counties rely on seismic design provisions in codes to ensure structures can resist earthquakes and maintain life safety. Historically, America s first line of defense has been the construction of buildings that can withstand severe shaking without eventual collapse. The earliest seismic design provisions in the United States were introduced in the first edition of Uniform Building Code (UBC) in By the 1950s, some California municipalities had adopted additional seismic-restraint design and material specifications, and in the 1970s, the National Science Foundation (NSF) funded a report evaluating existing earthquake-resistant design provisions. Drawing on this report, in 1985 the Federal Emergency Management Agency (FEMA) released the National Earthquake Hazards Reduction Program (NEHRP) Recommended Provisions for the Development of Seismic Regulations for New Buildings. Since 2000, the International Code Council (ICC) has developed and published the International Building Code (IBC), a model building code. All 50 states, and the U.S. Virgin Islands, use IBC at a local or statewide level. Following the code

4 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. Previously, building teams could examine a map and determine their seismic requirements based on geography. Today, seismic design coefficients are not generalized by geography; they can vary between projects in the same city based on specific location. According to IBC, every construction project must meet a seismic design category (SDC). These determine specific product performance and installation methods required by code to withstand certain seismic activity levels. A professional engineer or a registered architect must specify the SDC on the project drawings. IBC outlines six SDCs A through F, ranging from the least to the most stringent (Figure 1, page 99). For each construction project, a SDC is established by considering three variables: 1. Occupancy segmented into three different groups: Group III (essential facilities such as hospitals, fire departments, and police departments that must function both during and after a seismic event); Group II (buildings constituting a substantial potential for public hazard, such as power plants and those housing more than 300 people); and Group I (all other buildings). 2. Site soil properties soil type in a specific geographic area, classified from hard rock to soft soil and special soil conditions. 3. Location anticipated ground motion for a geographic area, based on earthquake groundmotion maps. The equation for SDC can be expressed schematically as: Occupancy + Site soil properties + Location = Seismic Design Category (SDC) Installation standards for suspended ceilings in seismic categories are based on: IBC; American Society for Civil Engineers/Structural Engineering Institute (ASCE/SEI) 7-10, Minimum Design Loads for Buildings and Other Structures; Ceilings and Interior Systems Construction Association (CISCA) seismic documents; and, Standard Practice for Installation of Ceiling Suspension Systems for Acoustical Tile and Lay-in Panels in Areas Subject to Earthquake Ground Motions. The 2012 IBC, soon to be adopted nationwide, is based on ASCE/SEI Differences between IBC 2009 and 2012 also reflect differences between ASCE/SEI 7-05 and The former details the requirements for industry standard construction in Section , and identifies categories for construction of suspended ceilings weighing less than 0.19 kpa (4 psf). For example, design category C is described in Section referencing CISCA s Guidelines for Seismic Restraint for Direct-hung Suspended

5 Figure 3b Description of changes from 2009 IBC to 2012 IBC SDCs D, E, and F ASCE ASCE 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. Power-actuated fasteners allowed for suspended ceilings are: concrete 41 kg (90 lb) maximum allowed service load; and steel kg (250 lb) maximum allowed service load. Seismic separation joint ± 19-mm ( 3 /4-in.) axial movement specified. Sprinkler heads: lateral deflection < 6.35 mm 50.8 mm (0.25 in. 2-in.) oversize ring not required; and flexible sprinkler fitting with 25.4 mm (1 in.) of movement 50.8-mm (2-in.) oversize ring not required.* * The measurements referenced within refer to the movement of the pipe (whether it be rigid or flexible) within the ceiling tile for the sprinkler heads. If the diameter of the hole, when the pipe is inserted within, is beyond the recommended spacing then a 50.8-mm (2-in.) ring is required. Therefore, if the lateral deflection of the pipe is less than 6.35 mm, then a 50.8-mm oversized ring is not required. However, if the movement is greater than 6.35 mm, a 50.8-mm oversized ring must hold the pipe in place. The same applies to the flexible sprinkler at 25.4 mm. Lateral bracing wire connections must be at least kg. For ceiling system connection/splice testing, three replicate samples must group within 10 percent of mean. If not, three additional tests must be run with the high and low values dropped. The average of the remaining four test results must group within 10 percent of the mean if not, the lowest value of the six tests becomes the controlling value. Direct hung concealed systems: 1524 mm (60 in.) maximum spacing for stabilizer bars or cross-tees and must be within 610 mm (24 in.) of walls. Vertical hanger wires: three tight wraps over 76.2 mm (3 in.); and connections to structure must support minimum 41 kg (90 lb) allowable load. Surface-mounted light fixtures must be attached to ceiling grid system with positive clamping devices. Also, safety wires are required. Rigid conduit should not be used for attachment of light fixtures. Partitions attached to ceilings and all partitions greater than 1.83 m (6 ft) in height must be laterally braced to the building structure. Consequential damage: potential interaction between architectural components (e.g. ceilings) shall be considered to prevent failure of essential systems/components. When referenced in drawings, becomes part of the drawing requirements unless otherwise specified. Ceiling Assemblies for Seismic Zones 0 2. Design categories D, E, and F are described in Section , and reference CISCA s Guidelines for Seismic Restraint for Direct Hung Suspended Ceiling Assemblies for Seismic Zones 3 4. For SDCs A and B, ceiling installation should conform to basic minimums established in ASTM C636, Standard Practice for Installation of Metal Ceiling Suspension Systems for Acoustical Tile and Lay-in Panels. The updated ASCE/SEI replaces the two

6 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 in the San Francisco Bay region before San Francisco is situated near the meeting point of the North American and Pacific plates, which slide past each other horizontally. The San Andreas Fault, which forms the active boundary between these two plates, runs north and south through California and produces earthquakes in the Bay area. The 1989 Loma Prieta Earthquake in San Francisco, with a magnitude of 7.1, had an epicenter located more than 80.5 km (50 mi) from San Francisco and Oakland. It rocked the California coast from Monterey to San Francisco with a strong motion duration of more than 15 seconds. During the Loma Prieta seismic event, at least 65 people were killed and the financial loss was estimated to be between $6 and $10 billion. The damage showed some of the suspended ceilings cross-tees, main runners, air diffusers, and panels had collapsed. This led to an awareness of the vulnerability of these units and resulted in new code regulations. cs * The U.S. Geological Survey (USGS) shares real-time, global seismic monitoring data online at Seismic separation joint-tees can provide movement along the separation joint during a seismic event. They are designed to move linearly and dissipate energy along the tee, eliminating need for a conventional separation joint. Tees have one stakedon stab-in end tab and an opposing elongated integral end. Compared to standard recommended installations, seismic separation joint-tees include faster installation. One can just insert the tees and install push rivets to create the expansion joint. There is no going back to cut main or cross-tees or to add channels, angles, or clips. existing CISCA documents with one ASTM standard. Figure 2 summarizes the relationship. Figure 3 (pages 100 and 102) illustrate the notable changes in IBC between the 2009 and 2012 editions. It is important to note code enforcement is performed at the local level. Where IBC is adopted as the model code, all reference documents are then applicable. The authority having jurisdiction (AHJ), or onsite inspector, is responsible for the interpretation and enforcement of the building code. For example, the 2010 California Building Code (CBC), Section , requires metal ceiling panels to be positively attached to the ceiling suspension runners. AHJs often use third-party evaluation reports as the basis for approving products. Building codes, and performance evaluations based on testing, can be used to understand ceiling behavior during seismic activity. Evaluation reports are provided to ensure building products meet code requirements. ICC-Evaluation Service (ICC-ES) generates reports for suspension systems and most of the major ceiling suspension manufacturers have reports available for their products. Seismic separation Suspended ceiling installations exceeding 762 m 2 (2500 sf) in SDCs D, E, and F must have separation joints. An accepted method for creating a seismic separation joint involves capping 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 plenum from being visible. At this point, the suspension system is stabilized with

7 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 kg (180 lb). The internal friction in the joint also provides a measure of damping. additional hanger wires. In addition to increased material costs and time on the job, this multi-step process risks incurring delays while the construction method is inspected and approved. However, alternate constructions are permitted that have been tested and identified as performing as well as, or better than, the code requirements. Current tests have been based on ICC-ES Acceptance Criteria (AC) 156, Acceptance Criteria for Seismic Certification by Shake-table Testing of Nonstructural Components, using a comparative test method. When conducting seismic comparison tests, the code-required installation is tested alongside the proposed installation. The seismic separation joint-tee is an alternative that has been tested and evaluated by an independent, internationally renowned structural and earthquake engineering group at the University at Buffalo the State University of New York (SUNY) and evaluated by Miyamoto International, Inc. an independent, internationally renowned structural and earthquake engineering firm. Designed to provide movement along the separation joint during a seismic event, the seismic separation joint-tees move linearly and dissipate energy along the tee, eliminating the need for a conventional separation joint. Compared to standard recommended installations, other benefits of the seismic separation joint-tee include faster installation with a one-step process. Once the tees are inserted and push rivets are installed to create the expansion joint. As a result, there is no need to cut main or cross-tees, or to add channels, angles, or clips. Seismic perimeter treatment During a seismic event, structural integrity may 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 plenum from being visible. The suspension system is stabilized with additional hanger wires. In addition to increased material costs and time on the job, this multi-step conventional process risks incurring delays while the construction method is inspected and approved. The elongated ends of two seismic separation tees are installed on both sides of the main tee designated as the seismic joint. also be compromised at the ceiling s perimeter. Under certain vibration conditions experienced in an earthquake, ceiling motion can increase and lead to near total failure of the acoustical ceiling. The code-prescribed method for seismic ceiling perimeter treatment requires a 51-mm (2-in.) wall angle, suspended with perimeter support wire, within 203 mm (8 in.) of the wall. Further, the perimeter components must be tied together to prevent spreading. When the suspension members spread apart the perimeter, the ceiling panels may then become dislodged from the suspension system. Consequently, they may fall out. Typically, this means spacer bars are installed between tees to stabilize the ceiling. 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 SDC C, the use of an approved seismic perimeter clip may eliminate the need for spacer bars. For SDCs D, E, and F, use of an approved seismic perimeter clip may replace the 51-mm wall angle with a 24-mm (0.95-in.) wall angle, and eliminate the need for spacer bars. Approved seismic perimeter clips also save on

8 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). Photo Steve Wanke Photography. Photo courtesy Chicago Metalic Corp. 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. Opened in May 2012, the $218-million, four-story Marian Regional Medical Center (Santa Maria, California) now spans more than 18,580 m 2 (200,000 sf). Meeting OSHPD criteria, seismic perimeter clips were installed throughout the 191-bed hospital facility. Photo Steve Wanke Photography. Photo courtesy Chicago Metalic Corp. For SDCs D, E, and F, the use of an approved seismic perimeter clip may replace the 51-mm (2-in.) wall angle with a 24-mm (0.95-in.) wall angle, and eliminate the need for conventional spacer bars. Image courtesy Chicago Metalic Corp. costs associated with 51-mm wall angles and conventional spacer bars. Contractors also report perimeter clips are easier and faster to install than stabilizer bars. Once installed, architects appreciate the ceiling s clean, sleek appearance and maintenance staff like the easy access to perimeter panels. Most importantly, owners and occupants can feel protected knowing the approved perimeter clips meet the International Code Council s seismic criteria and, in many cases, also exceed the performance of the minimum code requirement. Conclusion Though suspended ceilings are considered nonstructural, prescribed methods are mentioned in IBC, and recommendations for seismic protection exist. To minimize loss of life and mitigate damages during an earthquake, the AHJ should be involved early. The Authority Having Jurisdiction must work closely with the building s design team. This helps the project achieve compliance with local codes, performance requirements, and overall seismic safety and performance goals. cs

9 This 24-mm (0.95-in.) seismic suspension system is installed with 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.» Additional Information Author Tony Ingratta serves as an engineer for Chicago Metallic Corp. He draws from more than 20 years of experience in product compliance, testing, and evaluating suspended ceiling systems. Ingratta earned his bachelor of science in mechanical technology from Bradley University in Peoria, Illinois. He is a member of ASTM International committees E06 on performance of buildings, E33 on building and environmental acoustics, and C11 on gypsum and related building materials and systems. Ingratta also is a member of the Ceilings and Interior Systems Construction Association (CISCA) Seismic Committee. He can be contacted at ingrattat@chicagometallic.com. Abstract Components of metal suspended ceiling systems, both structural and non-structural, in U.S. seismic areas have 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 Wanke Photography. Photo courtesy Chicago Metallic Corp. changed over the years. This includes the history of requirements, both building code and engineering standard-wise, along with changing guidelines for intersections, hanger and splay wire, lateral bracing, perimeters, lighting fixtures, and partitions. MasterFormat No Ceilings UniFormat No. C1070 Suspended Ceiling Construction C2050 Ceiling Finishes Key Words Division 09 Earthquake Metal ceilings Safety Seismic Contents of The Construction Specifier are copyrighted and are reproduced by Foster Printing Service with consent of Kenilworth Media Inc. The publisher and The Construction Specifications Institute shall not be liable for any of the views expressed by the authors, nor shall these opinions necessarily reflect those of the publisher and The Construction Specifications Institute. ROCKFON, LLC 4849 SOUTH AUSTIN AVE., CHICAGO, IL / USA and Canada: