Seismic requirements for electrical installations

Concern about earthquakes and their impact on buildings and facility operation is no longer limited to those regions of the United States, such as the West Coast, where seismic activity is common. Over the past decade, concern for those areas of the country that have always had the potential for a devastating earthquake—but rarely exhibited seismic activity—have increased.

Experience with earthquakes has shown that keeping buildings standing is necessary but not sufficient. Even if the building is structurally sound after a seismic event, it may no longer be able to function if its mechanical, electrical, plumbing and life safety (MEP) systems are damaged. This is especially true for critical facilities such as healthcare, communications and other emergency service facilities that need to be in operation after a major earthquake. Additionally, even though a building is still structurally sound following an earthquake, it may take a lot of time and money to restore the building’s MEP systems so that it can effectively function again.

As a result, building owners, code officials, insurance carriers and other stakeholders are now adopting and enforcing seismic requirements for MEP systems—in addition to structural systems—in areas where none existed before. The electrical contractor needs to be aware of seismic requirements for electrical installations because these requirements can have a significant impact on job cost and schedule.

International Building Code

The International Building Code (IBC) is published by the International Code Council Inc. (ICC), which is primarily composed of the Building Officials and Code Administrators Inc. (BOCA), the International Conference of Building Officials (ICBO) and the Southern Building Code Congress International (SBCCI). The purpose of the ICC is to provide the minimum requirements for protecting building occupants from fire and other hazards as well as to safeguard emergency personnel during emergency operations. The IBC is based on the BOCA National Building Code, ICBO’s Uniform Building Code, and SBCCI’s Standard Building Code. The 2006 edition of the IBC is widely adopted throughout the United States.

Earthquake requirements are specified in IBC Section 1613. The scope of Section 1613 includes not only structural systems but also nonstructural building components, which includes installed electrical equipment. Section 1613 requires electrical equipment that is permanently attached to the building structure—including attachments and support systems—be designed and installed in accordance with the American Society of Civil Engineers’ (ASCE) Minimum Design Loads for Buildings and Other Structures (which is ASCE 7-05). Chapter 13 of ASCE 7-05 addresses the seismic requirements for electrical equipment.

Complying with the IBC

In order to comply with the IBC, the electrical contractor must know the building’s seismic design category (SDC) and the component importance factor (Ip) for each piece of electrical equipment. The SDC is building specific and depends on its occupancy category (OC) as determined by the building’s intended use and the predicted severity of the earthquake ground motion at the site.

There are six SDCs, designated A through F, and the SDC for the electrical installation must be the same as that used to design the structure. Therefore, the SDC needs to be determined by the owner’s design team and provided to the electrical contractor.

All electrical equipment must be assigned an Ip, which is either 1.0 or 1.5 per ASCE 7-05. In general, any electrical equipment that is required to remain functional after an earthquake for life-safety purposes is assigned an Ip of 1.5 and all other equipment is assigned an Ip of 1.0.

For example, the emergency and legally required standby systems required by Articles 700 and 701 of the National Electrical Code (NEC) would probably be assigned an Ip of 1.5. The combination of the SDC and Ip will determine whether or not the electrical contractor will need to install seismic anchors, supports or restraints for particular electrical equipment in accordance with ASCE 7-05 Chapter 13. The electrical contracting firm should consider retaining a registered structural engineer to design the needed seismic anchors and supports for the electrical installation.

Equipment survivability

The electrical contractor must also be aware that Section 13.2.2(a) of ASCE 7-05 requires that electrical equipment installed in SDC C through F buildings—and required to remain operational following an earthquake—must be certified that it will remain operational based on a nationally recognized testing procedure or data from previous experience that is acceptable to the authority having jurisdiction.
One testing standard that is referenced in ASCE 7-05 and sometimes referenced directly in project specifications is ICC-ES AC 156, which is published by the ICC Evaluation Service Inc. and entitled, Acceptance Criteria for Seismic Qualification by Shake-Table Testing of Nonstructural Components and Systems.

The electrical contractor needs to be aware of equipment-survivability requirements and certifications for critical equipment because these requirements could have a significant impact on equipment cost and delivery schedule.

Seismic requirements for electrical installations are being encountered by electrical contractors in parts of the United States that previously were not considered earthquake prone even though the geological potential for earthquakes exists just like on the West Coast.

The seismic requirements for electrical installations may be explicitly called out in the contract documents, but more often they are implicitly included by reference to the IBC. Further, seismic requirements are rarely included in Division 16 of the project specifications and are typically found in Division 01, which applies to all divisions.

The electrical contractor must be aware of any seismic requirements on projects that it is bidding on, which includes how these requirements will need to be met and who will inspect and approve the installation. Since most seismic requirements for nonstructural components are performance-based, the electrical contracting firm will need to have a plan as to how to meet these requirements, which will usually involve retaining a registered structural engineer. All of this can have a significant impact on the project cost, schedule and risk that needs to be addressed in the electrical contractor’s bid.                EC

This article is the result of a research project investigating the impact of seismic requirements on electrical installations that is being sponsored by ELECTRI International Inc. The authors would like to thank the foundation for its support.

GLAVINICH is an associate professor in the Department of Civil, Environmental and Architectural Engineering at The University of Kansas. He can be reached at 785.864.3435 or tglavinich@ku.edu. ZHU is an assistant professor in the Department of Construction Management at Florida International University. He can be reached at 305.348.3517 or zhuy@fiu.edu.