Page 14 - Modern Steel Construction (April 2019)

steel quiz ANSWERS Anyone is welcome to submit questions and answers for the Steel Quiz. If you are interested in
submitting one question or an entire quiz, contact AISC’s Steel Solutions Center at 866.ASK.AISC or
solutions@aisc.org.

1 False. Section A3.1 of the AISC least of the following four options This is in addition to any brace
Seismic Provisions contains shall be used: 12 in.; one-half the deformations that may result from
charging language prohibiting the least dimension of the concrete frame deformation due to gravity
use of materials not included in encasement section is taken as (22 loads. The Commentary to this
the list provided. The Commentary in./2) = 11 in.; 8 #8 longitudinal bar section provides a useful discussion
for this section explains that the diameters would be 8(1 in.) = 8 in.; on the basis of these provisions,
structural steels listed are explicitly or 24 #3 tie bar diameters would be based on testing.
3
permitted for use in seismic 24( ∕8 in.) = 9 in. Thus, the least of 6 False. K-braced frames are
applications based on their inelastic these values is 8 in. prohibited, in Chapter F of the
properties and weldability.
4 False. The Commentary for Section Seismic Provisions, in ordinary
2 c. Section E3.6a in the Seismic C1 of the Seismic Provisions concentric braced frames (OCBFs)
Provisions provides a list of explains that drift due to seismic (F1.4b), special concentric braced
demand-critical welds that must effects differ than that of wind as frames (SCBFs) (F2.4c) and BRBF
satisfy the requirements of Sections it impacts the serviceability and (F4.4b) systems. The Commentary
A3.4b and I2.3. Note that AISC stability of the structure. Story drift explains that K-bracing can have
358 or other test standards may limits improve frame stability and very poor post-elastic performance.
designate welds as demand-critical seismic performance because of the After brace buckling, the action of
that are not identified as such by resulting strength and stiffness. the brace in tension induces large
the Seismic Provisions. flexural forces on the column,
5 Section F4.2 of the Seismic possibly leading to buckling. No
3 8 in. Section D1.4b.1 of the Seismic Provisions states that the expected adequate design procedures
Provisions provides requirements deformations correspond to a addressing the high-consequence
for the maximum spacing of story drift of at least 2% the story stability issues are available.
transverse reinforcement at the top height or two times the design
and bottom of the column. The story drift, whichever is larger.

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14 | APRIL 2019