I am a mechanical engineer (1983) and post graduate in engineering mechanics (IIT Madras 1994); fields of interest pressure vessels, piping, FEM, stress analysis, ASME etc;

The thickness formula for flat head (ASME Sec VIII Div1 or Div2) uses only allowable stresses in membrane; It is understood that the shape factor (1.5 or so for bending) is absorbed in the constant. I could not derive the same from Timoshenko circular plate theory.
Where shall I look for derivation? can any one give me the derivation

SRINIVASAN
NEW MEMBER

_________________
R.SRINIVASAN
Sr. VICE PRESIDENT
Head, Design and Engineering
PED,ISGEC,
YAMUNANAGAR
HARYANA -135001
INDIA

The derivation depends on the boundary conditions at the edges. You may find it in some books for pressure vessel design.

Best Regards,

A. Zaki

Why derive the formula?
Just use it, there is no discussion why.

DK

Agreed that derivation is not required for a practicing engineer.

To understand the background of code to have in depth understanding, derivation helps.

In the present case the value of C includes section factor for bending (1.5 for rectangular section). The range of constant C should lie between simply supported and clamped (fixed) boundary conditions.

If we derive the constants for two boundary conditions using Theory of Plates (Timoshenko or any book), the range do not match with the code range.

Thanking You and With Regards

_________________
R.SRINIVASAN
Sr. VICE PRESIDENT
Head, Design and Engineering
PED,ISGEC,
YAMUNANAGAR
HARYANA -135001
INDIA

Let me propose another way for thinking about this issue that I think It sound applicable.

If you had a flat head required to be designed then there are several stepped options you could think and go through as follows:-

1- If the loads and shape configuration for this head could be represented by those adopted by the Code then use Code formulas.

2- If the loads and/or configuration are slightly different to those of the Code, and according to your judgment, that would produce extra stresses than those considered in the Code. Then you could adopt any appropriate method for calculation and judgment of these extra stresses. This of course will be in addition to satisfying Code requirements as mentioned above.

3- If these loads and/or Configuration are totally different to those of the Code. Then the Code requirements are not mandatory for this case and you could adopt any appropriate method for the design of this head.

Best Regards,

A. Zaki