Design of a Built-Up Steel Blast Door -cont.

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(10) Determine the load-mass factor, KLM, and compute the
effective unit mass, me.
(11) Compute the natural period of vibration, TN.
(12) Determine the door response using the values of B/ru
and T/TN with Figure 6-7 of NAVFAC P-397 to determine
the values of Xm/XE and [theta].  Compare the design
criteria of Step 1.  If these requirements are not
satisfied, select another thickness and repeat Steps 2
to 13.
(13) Design supporting flexural element considering composite
action with the plate.
(14) Calculate elastic and plastic section moduli of the
combined section.
(15) Follow the design procedure for a flexural element as
described in the design examples of Section 4.
Calculation:
Given:
(1) Pressure-time loading as shown in Figure 76a.
(2) Design criteria:
Maximum ductility ratio, [mu]max = 5
Maximum end rotation, [theta]max = 2deg.,
whichever governs.
(3) Structural configuration as shown in Figure 76b.
Note:
This type of door configuration is suitable for
low pressure range applications (5 to 15 psi).
(4) Steel used:
ASTM A36
Yield strength, Fy = 36 ksi
Dynamic increase factor, c = 1.1
Hence, the dynamic yield strength:
Fdy = 1.1 x 36
= 39.6 ksi
and the dynamic yield stress in shear:
Fdv = 0.55Fdy
= 0.55 x 39.6
= 21.78 ksi
2.08-281