This "Code Simple" addresses the very important subject of errata. As desirable as it would be for a publication to be produced without errors, that typically proves to be an elusive goal. In fact, errata to errata have been known to become necessary.
Oftentimes, engineers only find out about errata from word of mouth. However, the publishing organizations for codes and standards conveniently post errata on their websites; see Table 1 below. A few items in the ASCE 7-05 seismic provisions errata that are especially noteworthy are clarified here.
Table 12.2-1 Design Coefficients and Factors for Seismic Force-Resisting Systems — Within this table, a correction to Ωo and to several footnotes are important.
For B.11., Composite Steel and Concrete Eccentrically Braced Frames, Ωo is 2 1/2, not 2.
For C.3., Intermediate Steel Moment Frames, remove footnote i for SDC D. For G.2., Intermediate Steel Moment Frames, remove footnote i for SDC E and remove footnote h for SDC F.
For G.3., Ordinary Steel Moment Frames, add footnote h for SDC D, remove footnote i for SDC E, and remove footnote h for SDC F.
Section 12.8.2 Period Determination — Within this section, "from Eq. 12.8-7" should be corrected in the second sentence.
The fundamental period, T, shall not exceed the product of the coefficient for upper limit on calculated period (Cu) from Table 12.8-1 and the approximate fundamental period, Ta, determined
from Eq.12.8-7 in accordance with Section 188.8.131.52.
Section 184.108.40.206 Simplified Design Procedure, Item 8 — This section is missing an equation and some variable descriptions. Note that there are differences between the equations below and what is shown in the ASCE 7-05 Errata dated Jan. 6, 2006.
8. For buildings with a diaphragm that is not flexible, the distance between the center of rigidity and the center of mass parallel to each major axis shall not exceed 15 percent of the greatest width of the diaphragm parallel to that axis. In addition, the following two equations shall be satisfied
for each major axis direction:
where, k1i is the lateral load stiffness of wall "i" or braced frame "i" parallel to major axis 1;
k2j is the lateral load stiffness of wall "j" or braced frame "j" parallel to major axis 2;
d1i is the distance from the wall "i" or braced frame "i" to the center of rigidity, perpendicular to major axis 1;
d2j is the distance from the wall "j" or braced frame "j" to the center of rigidity, perpendicular to major axis 2;
e1 is the distance perpendicular to major axis 1 between the center of rigidity and the center of mass; b1 is the width of the diaphragm perpendicular to major axis 1;
e2 is the distance perpendicular to major axis 2 between the center of rigidity and the center of mass;
b2 is the width of the diaphragm perpendicular to major axis 2;
m is the number of walls and braced frames resisting lateral force in direction 1;
n is the number of walls and braced frames resisting lateral force in direction 2.
Eq 12.14-2 A and B need not be checked where a structure fulfills all of the following limitations:
1. The arrangement of walls or braced frames is symmetric about each major axis direction,
2. The distance between the two most separated lines of walls or braced frames is at least 90 percent of the dimension of the structure perpendicular to that axis direction, and
3. The stiffness along each of the lines considered for item 2 above is at least 33 percent of the total stiffness in that axis direction.
Section 13.1.4 Exemptions 4 and 5 — Several important clarifications occur in this section.
4. Mechanical and electrical components in Seismic Design Categories D, E,
and or F where the component importance factor, Ip, is equal to 1.0 and either both of the following conditions apply:
a. flexible connections between the components and associated ductwork, piping, and conduit are provided,
b. components are mounted at 4 ft (1.22 m) or less above a floor level and weigh 400 lb (1780 N) or less.
5. Mechanical and electrical components in Seismic Design Categories D, E, and F where the component importance factor, Ip, is equal to 1.0 and both of the following conditions apply
a. flexible connections between the components and associated ductwork, piping, and conduit are provided, and
b. the components weigh 20 lb (89N) or less or, for distribution systems, weighing 5 lb/ft (73 N/m) or less.
This is by no means a complete list of the corrections to the ASCE 7-05 seismic provisions. The purpose of printing these few items is to point out how significant these corrections can be and the importance of staying up-to-date with the errata through visiting the codes and standards organizations’ websites periodically.
TABLE 1: Websites to find errata for commonly used codes
2006 International Building Code (www.iccsafe.org)
ASCE 7-05 Minimum Design Loads for Buildings and Other Structures (www.seinstitute.org)
ACI 318-05 Building Code Requirements for Structural Concrete (www.concrete.org) AISC 360-05 Specification for Structural Steel Buildings (www.aisc.org)
AISC 341-05 Seismic Provisions for Structural Steel Buildings (www.aisc.org)
S.K. Ghosh Associates, Inc., is a structural, seismic, and code consulting firm located in Palatine, Ill., and Laguna Niguel, 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 email@example.com and firstname.lastname@example.org, respectively.