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b.
Design of a BuiltUp Steel Blast Door
Problem:
Design a builtup steel blast door subjected to a
pressuretime loading.
Given:
(1) Pressuretime load.
(2) Design criteria, [mu]max and [theta]max for a
reusable or nonreusable structure (Section 4, paragraph
1.b.(2)).
(3) Structural configuration of the door including geometry
and support conditions.
(4) Properties of steel used:
Minimum yield strength, Fy, for door components.
Dynamic increase factor, c.
Solution:
(1) Select the thickness of the plate.
(2) Calculate the elastic section modulus, S, and the
plastic section modulus, Z, of the plate.
(3) Calculate the design plastic moment, Mp, of the plate.
(4) Compute the ultimate dynamic shear, Vp.
(5) Calculate maximum support shear, V, using a dynamic load
factor of 1.0 and determine V/Vp.
If V/Vp is less than 0.67, use the plastic design
moment as computed in Step 4.
If V/Vp is greater than 0.67, use Equation (97) to
calculate the effective Mp.
(6) Calculate the ultimate unit resistance of the section
(Table 55 of NAVFAC P397), using the equivalent plastic
moment as obtained in Step 3 and a dynamic load factor of
1.0.
(7) Determine the moment of inertia of the plate section.
(8) Compute the equivalent elastic unit stiffness, KE, of
the plate section.
(9) Calculate the equivalent elastic deflection, XE, of the
plate as given by XE = ru/KE.
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