Key factors addressed are:

• Electrical raceway (e.g. conduit, bus, cable trays).
• Suspended electrical equipment (e.g., transformers).
• Light fixtures.
• Electrical boxes (e.g., terminal boxes and pullboxes).

This design manual is part of a two-volume set produced by International Seismic Application Technology (ISAT), which is a global provider of engineering services, consulting services, and restraint system components for nonstructural seismic bracing. The two volume series provides guidelines for the design and installation of engineered seismic restraint systems for suspended utilities.

ISAT installation details and engineered bracing tables are suitable for use under the following codes and standards:

• 2006 International Building Code.
• ASCE 7-05, Minimum Design Loads For Building and Other Structures.
• FEMA 450-03, NEHRP Recommended Provisions for Seismic Regulations for New Buildings and Other Structures.
• FEMA 412, FEMA 413, FEMA 414, Installing Seismic Restraints for Non-Structural Components.
• TI-809-04 Seismic Design For Buildings, US Army Corp of Engineers Department of Defense, Unified Facilities Criteria 3-310-04 (6/07), Seismic Design for Buildings.
• NFPA 5000, Building Construction and Safety Code.
• American Concrete Institute (ACI) 318-02, Appendix D.

Seismic Force Formulas

The ISAT Applications and Design Manual provides seismic restraint requirements engineered for use within a broad range of horizontal accelerations. Information required at the beginning of the process includes project type, location, seismic force variables (below), and the seismic design specifications or performance criteria. Once these parameters have been determined and certain basic calculations have been performed, ISAT’s Engineered Bracing Tables and Detail Drawings are used to define the seismic bracing requirements for the suspended utilities.

ASCE 7-05, Section 13.1. requires design of the seismic restraints for nonstructural components. The resultant construction documents are to be prepared by a registered design professional.

Seismic Design Force for the component, Fp, is calculated per ASCE 7-05 Equations 13.3-1 thru 13.3-3. In order to perform these calculations it is first necessary that the project specific SDS value, defined below, be provided by the Engineer of Record or the Project Architect. The SDS value should commonly be identified on the structural plans or within the construction documents.

Variables used to determine the Seismic Design Force include:

• Spectral Response Acceleration at Short Periods, SDS.
• Component Amplification Factor, ap.
• Component Response Modification Factor, Rp.
• Component Importance Factor, Ip.
• Component Operating Weight, Wp.
• Height in Structure, Point of Component Attachment, z.
• Average Roof Height With Respect To Base, h.

The ISAT Project Worksheet at the back of the Manual will help you efficiently gather the required information for accurate calculations. The ISAT Manual also provides you with contact numbers to obtain project worksheets for use with other codes.

ISAT Engineered Bracing Tables

The cumulative result of applying the seismic demand formulas is the need to provide engineered seismic restraint systems covering a substantial range of possible horizontal accelerations. For simplicity, the worst case horizontal acceleration can be calculated at the underside of the roof deck and then used for all floors of the structure. However, to achieve economy of installation, the horizontal acceleration for each floor can be computed separately and used in conjunction with the ISAT bracing tables.

In response to this need ISAT has generated concise tables of the minimum restraint requirements for a broad array of component accelerations applied to commonly used suspended utilities.

Quality Assurance Provisions and Special Inspection

Per Sections 1705 and Section 1707 of the 2003 IBC quality assurance and special inspection is required of certain mechanical, electrical and plumbing systems within facilities assigned to Seismic Design Categories C, D, E or F.  The registered design professional in responsible charge may utilize ISAT documentation as the basis for submitting a Code required “special inspection plan” for these items.

Along with the need for special inspection of specific components as referenced above, contractor’s are required by Codes to submit “a written statement of responsibility” prior to installation of the system or components.

A definition of what systems and components require special inspection is provided within the Manual under the Application Notes section specific to each trade.

Blast Protection and Operational Resiliency

Seismic bracing can also be used to enhance the resiliency of utility systems within critical facilities where it has been deemed necessary to mitigate against the potential of a bomb blast.  ISAT's bracing system can be applied on projects where blast loads are defined.

Author: International Seismic Application Technology
Format: Looseleaf with custom binder
Copyright: 2007

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