If

FIGURE 13.52 Responses of girders in parallel arrangement [41].

1. For vortex-excited vibration

Uv0 = 1.33fyB torsional mode (13.15)

where fh and fy are natural frequencies (Hz) of heaving and torsional motion, respectively, and B is the projected width of girder in unit of meter.

2. For galloping

3. For flutter

13.4.2 Estimation of Amplitude

The equations for the estimation of maximum amplitude in vortex-excited vibration are given in The Wind-Resistant Design Handbook in Japan. 1. Heaving vibration h = (Eh ■ Eh ■ B)/(mr • dh) (13.18)

where h = heaving mode amplitude (m) Eh = 0.065bds(B/D)-1 Eh = 1 - 15bt(B/D)1/2Iu2 > 0, mr = m/(pB2) D = effective height of girder bds = 2 or 1 (2 for vertical web, 1 for others), correction factor for girder form

TABLE 13.1 Strouhal Number of Various Cross-Sections of Structural Members [5]

Profile dimensions, in mm

Value of

Wind

Profile dimensions, in mm

Value of se t-2.0

0 0

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