Page 107 - Forensic Structural Engineering Handbook

2.12 DESIGN AND CONSTRUCTION PRACTICES

Chapter 16 prescribes general structural design requirements, loads, and load combina-
tions. Earthquake, wind, and snow loads are based on ASCE 7-05. Chapter 19 prescribes
the design and construction of concrete used in structures and references ACI 318-05.
Chapter 21 prescribes the materials, design, and construction of masonry and refer-
ences ACI 530-05. Chapter 22 prescribes the design, fabrication, and erection of steel
used structurally in buildings and other structures and references the 2005 AISC
Specification for Structural Steel Buildings, ASCE 7-05, and other standards. Chapter
23 prescribes the materials, design, construction, and quality of wood members and
their fastening and references the 2005 National Design Specification for Wood
Construction.

Design Codes and Specifications

The model codes adopt many of the national design standards developed by organizations
such as the American Concrete Institute (ACI),the American Institute of Steel Construction
(AISC), and the National Forest Products Association (NFPA). 22–24 The model codes also
adopt by reference many of the standards adopted by ASTM International, originally
known as the American Society for Testing and Materials (ASTM), as the recognized test
procedures to ensure construction quality. ASTM Standards in Building Codes is compila-
tion of these standards. 25
Like the model codes, many of these standards are developed and written in a form that
allows them to be adopted by reference in a general building code. For example, the intro-
duction of ACI 318-05 notes the following:
The code has no legal status unless it is adopted by government bodies having the police power
to regulate building design and construction. Where the code has not been adopted, it may serve
as a reference to good practice even though it has no legal status.
ACI Building Code Requirements for Structural Concrete. From the early 1900s until
the early 1960s, the principal method of design for reinforced concrete was working stress
design. Since publication of the 1963 edition of the ACI Code, there has been a rapid tran-
sition to ultimate strength design. The 1963 ACI Code (ACI 318-63) treated the working
stress and the ultimate strength methods on an equal basis. However, a major portion of the
working stress method was modified to reflect ultimate strength behavior. The working
stress provisions of the 1963 Code, relating to bond, shear, and diagonal tension, and com-
bined axial compression and bending, had their basis in ultimate strength.
In 1971, ACI 318-71 was based entirely on the strength approach for proportioning
reinforced-concrete members, except for a small section devoted to what was called an
alternate design method. Even in that section, the service load capacities (except for flexure)
were prescribed as various percentages of the ultimate strength capacities of other parts of
the Code. The transition to ultimate strength theories for reinforced-concrete design was
essentially complete in the 1971 ACI Code.
In ACI 318-77, the alternate design method was moved to an appendix. The appendix
location served to separate and clarify the two methods of design, with the main body of
the Code devoted exclusively to the strength design method. The alternate design method
was retained in appendix B of ACI 318-83, and moved to Appendix A of ACI 318-89, ACI
318-95, and ACI 318-99. Since an appendix location is sometimes not considered to be an
official part of a legal document (unless specifically adopted), specific reference is made in
the main body of the Code (Section 8.1.2) to make Appendix A a legal part of the Code.
The Alternate Design Method was removed from ACI 318-02, and since then the ACI
Commentary (Section R1.1) has stated that the Alternate Design Method of the 1999 Code