CIVIL ENGINEERING FORMULAS

TABLE 10.3 Design Criteria for Symmetrical Flexural Sections for Load-Factor Design of Bridges

Maximum Flange minimum Web minimum Maximum

Type of bending strength Mu, thickness tf, thickness tu, unbraced length lb,

section inkip (mmkN) in (mm) in (mm) in (mm)

Compact* FyZ

Braced FyS

noncompact†

Unbraced ___________________________________ See AASHTO specification ________________________________

*Straight-line interpolation between compact and braced noncompact moments may be used for intermediate criteria, except that

should be maintained as well as the following: For compact sections, when both and d/twexceed 75% of the limits for these ratios, the following

interaction equation applies:

whereFyfis the yield strength of the flange, ksi (MPa); twis the web thickness, in (mm); and tfflange thickness, in (mm).

d

tw

9.35

b

tf



1064

Fyf

b/tf

twdFy/608

20,000Af

Fyd

h

150

b 2 Fy

69.6

[36002200(M 1 /Mu)]ry

Fy

d 2 Fy

608

b 2 Fy

65.0

257