The importance of defined terms in codes and standards cannot be over-emphasized. Quite often, words are defined differently than you would expect based on their ordinary dictionary meaning.
Chapter 2 of the 2006 International Building Code (IBC), which includes more than 600 defined terms, provides a comprehensive list of every word or phrase defined in the IBC. If a word or phrase is not defined in Chapter 2, then Section 201.4 states the following: “Where terms are not defined through the methods authorized by this section, such terms shall have ordinarily accepted meanings such as the context implies.” If a word is defined in a particular subsequent chapter, the Chapter 2 definition simply makes reference to that chapter for the definition. Some definitions included in 2006 IBC Chapter 2 that may be of interest to structural engineers are as follows:
Approved: Acceptable to the code official or authority having jurisdiction. (Note: This term is used more than 800 times in the 2006 IBC.)
Light-frame construction: A type of construction whose vertical and horizontal structural elements are primarily formed by a system of repetitive wood or light gage steel framing members.
Registered design professional: An individual who is registered or licensed to practice their respective design profession as defined by the statutory requirements of the professional registration laws of the state or jurisdiction in which the project is to be constructed.
Townhouse: A single-family dwelling unit constructed in a group of three or more attached units in which each unit extends from the foundation to roof and with open space on at least two sides.
Wall, Load-bearing: Any wall meeting either of the following classifications: 1) Any metal or wood stud wall that supports more than 100 plf of vertical load in addition to its own weight; or 2) Any masonry or concrete wall that supports more than 200 plf of vertical load in addition to its own weight..
Wall, Nonload-bearing: Any wall that is not a load-bearing wall.
When it comes to ASCE 7-05, there is not one location with a comprehensive list of every defined term as is the case with 2006 IBC Chapter 2. Instead, each chapter may or may not include a list of defined terms. The following sections include defined terms: 1.2, 3.1.1, 4.1, 5.2, 6.2, 10.2, 11.2, 17.1.2, and 18.1.2.
Probably the most frequently referred to definitions are those in ASCE 7-05 Chapters 6 (Wind Loads) and 11 (Seismic Design Criteria). The list below highlights a few terms defined in Chapters 6 and 11 that often go unnoticed.
ASCE 7-05 Chapter 6:
Building and other structures, Flexible: Slender buildings and other structures that have a fundamental natural frequency less than 1 Hz.
Building and other structures, Regular-shaped: A building or other structure having no unusual geometrical irregularity in spatial form.
Building and other structures, Rigid: A building or other structure whose fundamental frequency is greater than or equal to 1 Hz.
ASCE 7-05 Chapter 11:
Designated seismic systems: The seismic force-resisting system and those architectural, electrical, and mechanical systems or their components that require design in accordance with Chapter 13 and for which the component importance factor, Ip, is greater than 1.0.
Flexible component (found under “c” for “component, flexible”): Component, including its attachments, having a fundamental period greater than 0.06s.
Rigid component (found under “c” for “component, rigid”): Component, including its attachments, having a fundamental period less than or equal to 0.06s.
Only a very small sampling of the many useful definitions found in the 2006 IBC and ASCE 7-05 is provided above. There are many more definitions that are of importance and significance to the structural designer. Knowledge of them is critical, as they can often provide the key to the solution of difficult-to-comply code situations.
S.K. Ghosh Associates Inc., is a structural seismic, and code consulting firm located in Palatine, Ill., and Aliso Viejo, Calif. President S.K. Ghosh, Ph.D., and Susan Dowty, S.E., are active in the development and interpretation of national structural code provisions. They can be contacted at firstname.lastname@example.org and email@example.com, respectively, or at www.skghoshassociates.com