FAQ on SEI Standards

This quarterly article addresses some of the questions received about structural standards developed by the Structural Engineering Institute (SEI) of the American Society of Civil Engineers (ASCE). Questions from engineers, building officials, and other design professionals are often considered to develop future editions.

These topics and more are discussed on the ASCE Peer-to-Peer Standards Exchange Forum. ASCE/SEI members can ask and answer questions in the forum. Visit https://collaborate.asce.org/standards-exchange/home to learn more and read about other topics.

Per ASCE/SEI 7-22 Table 13.1-1, Nonstructural Components Exempt from the Requirements of This Chapter, mechanical and electrical components in Seismic Design Category C that are positively attached to the structure and have a component Importance Factor, Ip, equal to 1.0 are exempt from the requirements of Chapter 13, Seismic Design Requirements for Nonstructural Components.

If that nonstructural component is analyzed for stability from overturning and found to be stable under the seismic demand required per Chapter 13 (e.g. Factor of Safety of 1.5 against overturning using ASCE load combinations) and is qualified seismically for the same loading for the structural integrity of the component itself (to prevent life-safety hazard by component failure), is there any commentary or consideration for the positive attachment not to be required based on engineering analysis?

Answer: There are no exceptions to Table 13.1-1. Positive attachment is required for mechanical and electrical components in Seismic Design Category C with an Ip of 1.0; these components are exempt from the other requirements of Chapter 13.

Note that there is no exemption for architectural components in Seismic Design Category C. Per Section 13.4, Nonstructural Component Anchorage and Attachment, non-structural components and their supports shall be bolted, welded, or otherwise positively fastened without consideration of frictional resistance produced by the effects of gravity. The only exception to this requirement is for rooftop solar panels that satisfy the provisions of Section 13.6.12, Rooftop Solar Panels.

ASCE/SEI 7-22 Section 13.2.1, Applicable Requirements for Architectural, Mechanical, and Electrical Components, Support, and Attachments, states that the component itself (not just the support and attachment) shall be analyzed or tested. However, C13.6, Mechanical and Electrical Components, implies that at the usual safety level (Ip=1.0), if failure of the mechanical or electrical component itself poses no significant hazard, only supports and attachments need to be designed, not the component itself. The Commentary also implies that engineering judgment can be used to determine whether failure of the component is a threat to life.

Can you please confirm that the intent of the standard is to allow engineering judgment (when Ip = 1.0) to determine whether a component itself needs to be analyzed or tested?

Answer: SCE/SEI 7-22 Chapter 13 code and commentary only requires the design of supports and attachments for Ip = 1.0 components, but “supports” can include parts fabricated by the equipment manufacturer, as described in 13.6.4, Component Supports, and C13.6.4. Although not in the code sections, it is established by C13.6 that the design of supports integral to the equipment is required when there is a life safety hazard, typically for overhead or wall mounted components and base mounted components of such height that they could pose a life safety hazard.

What Risk Category does ASCE 7-22 require for light poles? Would a 30-foot light pole in a parking lot qualify as Risk Category I? What about a 75-foot pole lighting a Little League field?

Answer: ASCE/SEI 7-22 limits Risk Category I to structures that represent low risk to human life in the event of failure. While a light pole is not an occupied structure, it does represent a risk to the public if it were to fail and therefore should be classified as Risk Category II.

ASCE/SEI 72-21 Design of Steel Lighting System Support Pole Structures provides more specific guidance related to lighting fixtures and appurtenances. Per Section 2.3, Classification of Structures, of ASCE/SEI 72-21, all lighting system support structures are classified as Risk Category II, because nearly all light poles have some proximity to occupied areas. As noted in the question, there certainly is a difference in the number of people that could be affected by the failure of a 30-foot parking area pole versus the failure of a 75-foot athletic field lighting pole.

The Commentary to ASCE/SEI 72-21 states that the Risk Category may be increased to Risk Category III or higher at the engineer’s discretion. The ASCE 72 Committee is currently reviewing the Risk Category provisions for possible revision in the next edition of the standard. Any feedback or input regarding Risk Category of steel lighting system supports should be directed to Wes Oliphant, Chair of ASCE 72, at woliphant@exoinc.com.

This article’s information is provided for general informational purposes only and is not intended in any fashion to be a substitute for professional consultation. Information provided does not constitute a formal interpretation of the standard. Under no circumstances does ASCE/SEI, its affiliates, officers, directors, employees, or volunteers warrant the completeness, accuracy, or relevancy of any information or advice provided herein or its usefulness for any particular purpose. ASCE/SEI, its affiliates, officers, directors, employees, and volunteers expressly disclaim any and all responsibility for any liability, loss, or damage that you may cause or incur in reliance on any information or advice provided herein.

If you have a question you want to be considered in a future issue, please send it to sei@asce.org with FAQ in the subject line. Visit asce.org/sei to learn more about ASCE/SEI Standards. ■

About the Author

Jeannette Torrents, PE, SE, F.SEI, is the Technical Director of the Structural Engineering Institute.