D1.L.4.1.4 Bending Stress
Allowable bending stress for tension and compression for a structural member, as given in NF-3322.1(d) is:
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Along Major Axis:
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For Compact Sections, tension and compression on extreme fibres of compact hot rolled or built-up members symmetrical about and loaded in the plane of their minor axes and meeting the requirements of Subsection NF shall result in a maximum bending stress:
Fb = 0.66×Fy
If meeting the requirements of this member of:
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Width-thickness ratio of unstiffened projecting elements of the compression flange shall not exceed 65/√Fy .
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Width-thickness ratio of stiffened elements of the compression flange shall not exceed 190/√Fy .
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The depth-thickness ratio of the web shall not exceed
d/t = (640/√Fy)[1 - 3.74(fa/Fy)] when fa/Fy ≤ 0.16
d/t = 257/√Fy when fa/Fy > 0.16
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The laterally unsupported length of the compression flange of members other than box-shaped members shall not exceed the value of 76bf/√Fy nor 20,000/(d/Af)Fy .
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For noncompact and slender elements, NF-3322.1(d)(5) and NF-3322.1(d)(3) are followed respectively.
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For box-type flexural members, maximum bending stress is:
Fb = 0.60×Fy
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Along Minor Axis:
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For doubly symmetrical members (I shaped) meeting the requirements of NF-3322.1(d)(1)(a) and (b), maximum tensile and compressive bending stress shall not exceed:
Fb = 0.75×Fy
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For doubly symmetrical members (I shaped) meeting the requirements of NF-3322.1(d)(1)(a), except where bf/2tf exceeds 65/√Fy but is less than 95/√Fy , maximum tensile and compressive bending stress shall not exceed:
Fb = Fy[1.075 - 0.005(bf/2tf)√Fy]
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