Seismic Bracing For Non-Structural ComponentsNov 16 2016 · 0 comments · NISHKIAN DEAN, Seismic, Technical notes ·0
By Dave Beh
Structural engineers design the primary structure to withstand seismic forces, as a minimum, as outlined by the design code. However, during an earthquake people can be injured and costly damage can result by falling non-structural components such as; kitchen hoods, bookcases or mechanical/electrical equipment. The code also requires seismic anchorage for certain non-structural components but these can sometimes get overlooked by designers/owners/plans examiners that simply don’t yet have the information or are unaware of the requirements.
The cost of repair and disruption due to earthquake damage to nonstructural elements often exceeds the structural repair costs and as a result represent potentially substantial financial losses. ATC reports, “Nonstructural damage may account for more than 50% of total damage in future domestic earthquakes.” ASCE 41 provides a helpful checklist for evaluating the non-structural components in existing buildings. Proper mitigation and repair can save money avoiding costly repairs and prevent injury or death for both new and existing buildings.
The building code requires seismic anchorage for suspended items weighing more than 60 lbs. and for floor mounted items with a center of gravity higher than 4 feet or weighing more than 400 lbs. Distributed systems such as piping, ductwork and suspended ceilings also require seismic anchorage. Damage occurs to the non-structural components of a building subjected to earthquake ground motion either from the inertial accelerations imposed or due to the deformations of the building itself.
Support for these systems does not generally impart large seismic loads to the structure and component weights are often considered in the base design of the structure. For components added as part of a remodel, major structural changes are not generally required to support the lateral forces imposed by the non-structural components.
Electrical and mechanical systems necessary for the proper function of essential facilities like hospitals and fire stations are required to be designed to withstand greater forces than elements such as cabinets in the same building. There are also stringent design requirements for piping and tanks carrying hazardous materials and chemicals.
Non-structural components can sometimes get overlooked during the design phase as not all of the fixtures and components are known at the time of the design. But retrofit measures can be undertaken. If there are questions about the support of the non-structural components that are already installed or components being installed in a new build, contact our office.
Dave Beh is a Project Engineer with Nishkian Dean a structural engineering consulting firm in Portland, Oregon.
- International Building Code 2012, International Code Council, May 2011
- Earthquake Hazard Mitigation for Nonstructural Elements, Field Manual, FEMA 74-FM / September 2005
- ASCE 41-13 Seismic Evaluation and Retrofit of Existing Buildings, ASCE, 2014
 Nonstructural components of buildings are categorized as architectural elements (such as interior partition walls, non-load-bearing exterior curtain walls, windows, and suspended ceilings); as mechanical, electrical, and plumbing (MEP) components (such as HVAC units, ducts, conduits, and pipes); or as furniture, fixtures, and equipment (FF&E) and other building contents.
 Earthquake Hazard Mitigation for Nonstructural Elements, Field Manual, FEMA 74-FM / September 2005, pg. 8