Seismic Restraint for Structural Engineering

Published on February 6, 2014 by Structural Innovations in Seismic Design

One requirement generally overlooked by design professionals is the seismic restraint of non-structural components. The International Building Code and referenced design standards require the seismic restraint of non-structural components depending on the seismic design category of the structure and the type of component in question.

To understand these requirements, it’s appropriate to first understand what a non-structural component is. Non-structural components, as defined by American Society of Civil Engineers ASCE 7-05 standard, are architectural, mechanical or electrical systems that do not make up more than 25% of the overall effective seismic weight of a structure. Dropped ceilings, suspended lighting, HVAC and piping systems are all examples of non-structural components. Should these components be situated in a Seismic Design Category D or higher structure, then additional seismic restraint is required. Additional restraint may also be required in structures in Seismic Design Category C depending on the if the system contains hazardous materials, critical to the life-safety systems of a building or is located in a Occupancy Category IV structure. Any seismic restraint must be designed and detailed by a licensed structural engineer.

The structural engineer in charge of designing the restraints must specify seismically qualified connection components that meet the standards of the IBC. The structural engineer must also specify if physical testing (i.e. shake table testing) is required; physical testing of some components may be required in Seismic Design Categories C or higher if the system is to remain operable post earthquake. Fortunately, there are many seismically qualified restraints on the market today. They vary from fixed struts to strapping. Prior to selecting a restraint, it’s critical to obtain the documentation that the restraint was testing in accordance with ICC-ES AC 156.
This article is meant to give basic information regarding the use of seismic restraints for non-structural components. The topic is varied with many caveats depending on the system in question. It is important to consult your local building code for any and all requirements pertained to seismically restraining non-structural components.

Structural Innovations Engineering & Consulting, PC has licensed structural engineers on staff who can assist in performing seismic analysis on non-structural components. We can supply detailed restraint drawings along with design packages for permit approval. Please do not hesitate to call if you have questions on how to perform seismic analysis on your project.