Why have changes in seismic requirements come about so suddenly?

Actually, the changes have occurred over a long period of time. In fact, the changes associated with ceiling systems—and other architectural, mechanical and electrical components—were introduced in the International Building Code in the 2000 edition. Most of those were developed in the National Earthquake Hazard Reduction Program (NEHRP) Recommended Provision of the mid-1990s. Since enforcement of building code requirements is often minimal for architectural, mechanical and electrical components, what gets done is often based on what suppliers and architects do, rather than on what building officials require. Over time the architects and suppliers as well as building officials are becoming aware of these requirements and are imposing them on projects. It's been more of an awakening than a sudden change. There really have not been any substantial changes in the code requirements for the last six years—just little tweaks here and there.

What are the requirements for ceiling systems specified by ASCE 7?

The seismic requirements for ceiling systems are a function of the seismic design category in which they are installed. First, the seismic design category at a particular site is a function of the ground motion hazard. Second, it's a function of the type of soil conditions. Third, it's a function of the type of structure—a critical structure has higher requirements. For example, the requirements for soft soil conditions will be higher than for buildings on rock. The requirements for a project near the San Andreas Fault will be different than one in South Florida.

There are basically three classes of ceiling systems permitted in ASCE 7 in structures assigned to seismic design categories D, E and F (the highest level of requirements). Ceilings in these high seismic design category structures using conventional suspended ceilings will require large holes around the sprinkler drops—much larger than required in the past—and larger ledger seats at the edges of the ceilings. If you provide sprinkler drops that are flexible—through articulating joints or use flexible hoses— then the requirements for oversized holes no longer apply. There's also an option of using integral wall-and-ceiling construction, which eliminates the need for oversized sprinkler drops and wide ledger seat angles. As a final option, one can test for large levels of motion and demonstrate that a particular system is seismically qualified.

What are the differences between ASCE 7-05 and ASCE 7-02?

The '02 version discussed the need for alternative qualifying equipment and components through testing, experience data or analysis. In the '05 version, a specific shake table testing document is specified. So now, if someone wants to shake table test the ceiling suspension for approval by a local building code official or ICC Evaluation Services, the document specifies a seismic qualification test protocol.

Is it true the IBC merely references ASCE 7 for the ceiling suspension standards?

Yes. And the 2006 IBC references ASCE 7-05 for all of its seismic requirements— not only for ceiling suspensions, but also for all architectural, mechanical, electrical components and the structural system. It used to be you would go to the code and all the seismic requirements would be retained within the code. Now the code just references ASCE 7-05, which in turn references the Ceilings and Interior Systems Construction Assn. (CISCA) requirements.

Will the day ever come when seismic ceiling requirements will be contained in one document?

No. That day will never come. The 1997 Uniform Building Code was the last document that more or less contained all the seismic requirements for ceilings. When the three codes (the UBC, the National Building Code and the Standard Building Code) decided to merge and become one code (the IBC), there was a decision to reference standards whenever possible. The goal was a more concise administrative document where technical issues could be hammered out by standards committees with expertise in their specialty areas rather than in building code hearings.

Tell us a little about the code-writing process.

The IBC selected as the basis for its seismic requirements the NEHRP Recommended Provisions. NEHRP Recommended Provisions were first developed in 1985 by the Building Seismic Safety Council (BSSC)—under Federal Emergency Management Agency (FEMA) sponsorship—and NEHRP Provisions Update Committee has updated them every three years since then. Actually, the NEHRP Provisions were based on ATC-3-06, a document developed in the mid-70s after the San Fernando earthquake and published in 1978.

The code-writing process evolved in the mid '90s, when work began on the 2000 IBC. The NEHRP Recommended Provisions had to be translated into code provisions, and then they had to become proposals submitted to the IBC Structural Committee. Finally, the IBC seismic standards were completed after several hearings, formal balloting and final voting by the wide body of building officials.

Is that it, then?

As indicated earlier, building officials want buildings to reference technical standards in the building code rather than include the requirements. They also would like standards to be developed in conformance with the American National Standards Institute (ANSI) process. The ANSI process would be desirable, since it formalizes the accountability of experts serving on committees and making the balance of decisions. Today, a lot of code standards are ANSI standards, but not all of them. The CISCA standards, for example, are not ANSI standards.

What has been learned about ceiling suspensions since the '70s?

A lot has happened. We had three major earthquakes in urban settings—the 1989 Loma Prieta Earthquake, the 1994 Northridge Earthquake and the 1995 Kobe Earthquake in Japan. Now, while we already knew that ceiling suspensions were vulnerable in earthquakes, we learned they were particularly vulnerable to interactions with sprinkler systems. Sprinkler systems damaged by interactions with ceilings systems could cause large amounts of water damage to buildings—and even shut buildings down.

Where does the state of California stand on IBC adoption?

The 2006 IBC was adopted in California on January 1, 2008. There is an adoption process that is currently underway, and some amendments developed by state agencies need to first be approved. Then, it will be formally adopted by the state. Local jurisdictions have 180 days to adopt after state approval. I think we're looking at enforcement of the 2006 IBC on projects by the end of 2007.

Will California's adoption of the IBC affect other parts of the country?

I expect more suppliers to design products to meet the latest code for architectural, mechanical and electrical components. As suppliers become aware of the code requirements and understand how to meet them, then more products will appear that will satisfy the code. And the process will accelerate in other areas of the country.

Can we expect any new provisions for ceiling suspension down the road?

There is consideration for moving the CISCA requirements into an ASTM International document. Right now, ASTM documents govern the testing of ceiling systems for vertical loads, but not seismic loads. There's a move afoot to include the seismic design from the CISCA documents, and that would be excellent. An ASTM document means it's an ANSI standard, which is what building officials want.

Of course, we will continue to work on the NEHRP Provisions. The next NEHRP Provisions will be updated in 2008, and a new ASCE 7 will appear in 2010 or 2011. But hopefully, we can get the ASCE 7-05 requirements into practice for a while so we can get feedback from engineers and architects on the current requirements before actually implementing new requirements. And if a significant earthquake occurs in the next few years, we can observe how newly installed sprinklers meeting the new requirements actually perform and, if necessary, adjust the requirements accordingly.