Structural Steel

Maximum Width-to-Thickness Ratios

The AISI Specification gives certain maximum width-to-thickness ratios that must be adhered to. For flange elements, such as in flexural members or columns, the maximum flat widthto- thickness ratio, w/t, disregarding any intermediate stiffeners, is as follows:
Stiffened compression element having one longitudinal edge connected to a web or flange element, the other stiffened by
(a) a simple lip, 60
(b) other stiffener with IS < Ia, 90
(c) other stiffener with IS => Ia, 90
Stiffened compression element with both longitudinal edges connected to other stiffened elements, 500
Unstiffened compression element, 60
In the above, IS is the moment of inertia of the stiffener about its centroidal axis, parallel to the element to be stiffened, and Ia is the moment of inertia of a stiffener adequate for the element to behave as a stiffened element. Note that, although greater ratios are permitted, stiffened compression elements with w/ t > 250, and unstiffened compression elements with w/t > 30 are likely to develop noticeable deformations at full design strength, but ability to develop required strength will be unaffected.
For web elements of flexural members, the maximum web depth-to-thickness ratio, h/t, disregarding any intermediate stiffeners, is as follows:
Unreinforced webs, 200 Webs with qualified transverse stiffeners that include (a) bearing stiffeners only, 260
(b) bearing and intermediate stiffeners, 300

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  1. Please help me I don’t know how to calculate the width thickness ratio limits of a plate which is bearing the loads as a beam.