CEMP-E
TI 809-26
1 March 2000
guidance from FEMA and AISC documents.
b. Applicability. Improved materials and details should be used for building structures classified as
Seismic Categories D, E and F. These applications include all buildings located in areas with 1 second
spectral response accelerations (SD1) of 0.20g or higher, or short period response accelerations (SDS) of
0.50g, and buildings of Seismic Use Group III in areas with SD1 of 0.133g or higher, or SDS of 0.33g or
higher. Seismic Use Group III structures are essential facilities that are required for post-earthquake
recovery and those containing substantial quantities of hazardous substances, including but not limited
to: fire, rescue and police stations; hospitals; designated medical facilities providing emergency medical
treatment; emergency operations centers; emergency shelters; emergency vehicle garages; designated
communications towers; air traffic control towers; and water treatment facilities needed to provide water
pressure for fire suppression. See TI 809-04, Table 4-1 for Seismic Use Groups, and Section 4.2 for
Seismic Design Categories.
c. Materials Concerns and Specifications. Special compositional, materials toughness and other
mechanical property requirements may be necessary for the steel and filer metal used in seismic
applications:
(1) The AISC Seismic Provisions, Section 6.3, require steel in the Seismic Force Resisting System
to have a minimum toughness of 27J at 21oC (20 ft.-lbf at 70oF), applicable to ASTM Group 4 and 5
shapes, Group 3 shapes with flanges 38 mm (1-1/2 in.) or thicker, and to plates in built-up members 38
mm (1-1/2 in.) or thicker.
(2) Studies indicate that a large percentage of domestically produced structural steel sections
lighter or thinner than those mentioned in the previous paragraph will have a CVN toughness of at least
27J at 21oC (20 ft.-lbf at 70oF), and therefore it does not appear that CVN testing need be conducted to
verify the toughness of all members. It is recommended that manufacturer's accumulated data be used
to verify that the steel routinely produced by that mill meets the indicated toughness levels. Specification
of steel toughness levels, or the specification of A709 steels, is currently considered unnecessary for
building-type applications.
(3) It is also recommended that structural steel shapes used in high seismic applications be
specified as either ASTM A992 or A572, grade 50 manufactured to AISC Technical Bulletin #3. These
specifications have provisions for a maximum ratio of Fy to Fu of 0.85, and a more controlled chemistry
for weldability and properties.
(4) The AISC Seismic Provisions, section 7.3b, require filler metals in the Seismic Force Resisting
System to have a minimum toughness of 27J at -29oC (20 ft.-lbf at -20oF). Additional requirements for
toughness at service temperature, tested using welding procedures representative of the range of
production WPSs, are also recommended in the latest FEMA Guidelines.
(5) There are concerns for the performance of rolled steel sections in the vicinity of the K-line, at
the intersection of the web and the radius between web and flange. Studies have identified a reduced
toughness in this region caused by cold-working during rotary straightening at the steel mill. Reduced
toughness in these region may increase the risk of crack initiation from welding in the area, particularly
stiffeners (continuity plates) and doubler plates. AISC Technical Advisory No. 1 should be followed,
pending further study.
(6) Current studies indicate that through-thickness toughness properties or applied stress on the
column face is not a limiting factor, and need not be specified or checked.
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