A Beginner's Guide to ASCE 7-05

Chapter 1 - General Information

© 2008, T. Bartlett Quimby

Section 1.4

Structure Classification

Last Revised: 11/04/2014

ASCE 7 Section 1.5 provides the criteria for the classification of structures based on the nature of occupancy and consequences of failure on the general public.  The structure classification is used to determine importance factors when computing the magnitude of loads to be considered.

The basic approach of the standard is to vary the magnitude of environmental loads in accordance to a building's classification.  If a building creates a potential hazard for a larger number of people than an other then it is designed for larger loads.  The potential hazard includes both physical harm of structural failure as well as the impact that the loss of the structure will have on its dependent or adjacent community.

As stated in the commentary "Classification... reflect(s) a progression of the anticipated seriousness of the consequence of failure from lowest hazard to human life... to highest..."

The commentary discussion does a very nice job of explaining the concepts behind the classifications. 

There are a couple of things to note:

• Number of occupants and the period of exposure to extreme events will have an impact on classification.
• A structure's status in relation to the community will effect its classification.
• The need for operation of a facility during and after an event will impact its classification.
• The impact of release of hazardous materials as the result of structural failure is a concern.
• Employees of a hazardous materials facility are considered to be more capable of dealing with release of hazardous materials than the general public so there is a distinction between these two groups of people.
• Implementation of a risk management plan may, in certain circumstances, allow for a lower building classification.
• Buildings can be classified differently for different load types in some circumstances.