Section 5 Dynamic loading

5.1.1 The following formulae are to be used to determine the dynamic response of plate and plate stiffener combinations. The natural frequency of structural items can be determined from Vol 1, Pt 6, Ch 2, 4 Vibration control and the period T may then be determined as follows:

where

5.1.2 For bottom impact pressure loads and bow flare and above waterline impact pressure loads required by Vol 1, Pt 6, Ch 3, 14 Strengthening for bottom slamming and Vol 1, Pt 6, Ch 3, 15 Strengthening for wave impact loads above waterline respectively, the impact pressure is assumed to be represented by a triangular pulse load. The rise time, t₁, for these impact pressures is given in Vol 1, Pt 5, Ch 3, 4.2 Bottom impact pressure, IPbi 4.2.2 for bottom impact and Vol 1, Pt 5, Ch 3, 4.3 Bow flare and wave impact pressures, IPbf 4.3.2 for bow flare impact.

5.1.3 For flight deck landing loads, the emergency landing load can be represented by a triangular pulse load. The rise time, t₁, for these impact pressures can be estimated from the time taken to depress the tyre and oleo strut to their maximum deflection and the assumed maximum vertical landing velocity. For fixed wing aircraft, the rise time for a structural element will also depend on forward speed as the aircraft traverses the structure.

5.2.1 For a gradually applied load as shown in Figure 2.5.1 Gradually applied load the maximum dynamic load factor f _DLF can be calculated as from Table 2.5.1 Tabulated dynamic load factors. Linear interpolation may be performed to obtain f _DLF values for intermediate t ₁/T values.

5.2.2 The time to maximum response can be calculated from Table 2.5.1 Tabulated dynamic load factors with intermediate values determined by linear interpolation.

5.3.1 For an instantaneous applied load as shown in Figure 2.5.2 Instantaneous pulse load the maximum dynamic load factor f _DLF can be calculated as from Table 2.5.1 Tabulated dynamic load factors Linear interpolation may be performed to obtain f _DLF values for intermediate t ₁/T values. The t ₁ time value is given in the same section that the impulsive pressure load is specified.

5.3.2 The time to maximum response can be calculated from Table 2.5.1 Tabulated dynamic load factors with intermediate values determined by linear interpolation.

5.4.1 For a triangular pulse load as shown in Figure 2.5.3 Triangular pulse load, the maximum dynamic load factor DLF be calculated from Table 2.5.1 Tabulated dynamic load factors. Linear interpolation may be performed to obtain DLF Rules for intermediate t ₁/T values. The t ₁ time value is given in the same section that the impulsive pressure load is specified.

5.4.2 The time to maximum response can be calculated from Table 2.5.1 Tabulated dynamic load factors with intermediate values determined by linear interpolation.