Abstract

Comparison is made between several calculation codes for brackets with webs and support plate.

• WRC 107 with solid rectangular attachments
• EN13445 clause 16.10 vertical vessels on bracket supports
• AD2000 S3/4 Vertical vessels with brackets (Behälter mit Tragpratzen)

WRC 107 and EN13445 clause 16.10 only focus the bracket calculation on the stresses in the shell. AD2000 S3/4 focuses the bracket calculation not only on the stresses in the shell, but also on the webs and support plate.

Introduction

A general bracket with vertical webs, horizontal support plate and reinforcement plate is shown below.

Bracket with webs

Calculation codes

The calculation codes for a bracket have similar scope and limitations in the calculation, but each code also has it's own scope and limitations.

Similar scope and limitations

• Design of vertical vessels with supporting brackets located on cylindrical shells.
• The total vessel weight is equally distributed over the brackets.
• Bracket is connected to the shell with or without reinforcement plate.
• Internal or external design pressure.
• Overturning moment in the longitudinal cross-section through the bracket center-line.

WRC scope limitations and results

• Horizontal load perpendicular to the shell.
• Shear load in circumferential direction.
• Shear load in longitudinal direction.
• Overturning moment in circumferential cross-section
• Torsional moment on the bracket around the radius of the shell.
• The bracket on the shell is regarded as a solid and massive attachment with negligible deformation.
• The attachment can be a "small" solid containing the bracket without reinforcement plate.
• The attachment can be a "large" solid containing the bracket with reinforcement plate.
• Only the stresses in the shell are checked.

WRC distinguishes for the stress calculation two edges:

1. at the edge of the solid attachment
2. at the edge of the reinforcement plate

 Stresses at edge of solid attachment with or without reinforcement plate.

Stresses at edge of reinforcement plate

For details on the WRC bracket calculation see Local stresses in cylindrical shells due to external loadings.

EN13445 scope limitations and results

• Also design of vertical vessels with supporting brackets located on conical shells.
• 0 ≤ cone angle ≤ 75 °
• Horizontal load perpendicular to the shell.
• The bracket on the shell can have 4 types of geometry: A, B, C, and D.
• At least 1 web must be used. The web thickness is not taken into account.
• Only the stresses in the shell are checked.

EN13445 distinguishes for the stress calculation the affected shell area.

For details on the EN13445 bracket calculation see 16.10 Vertical vessels on bracket supports.

AD2000 scope limitations and results

• Loads and stresses in horizontal, circumferential and torsional direction are ignored.
• At least 2 webs must be used. The web thickness is taken into account.
• The stresses in the shell, the support plate, the webs, the bolts and the foundation concrete are checked.

AD2000 distinguishes for the stress calculation two edges:

1. Stresses at the (outer) edge of the webs
2. Stresses at the edge of the reinforcement plate

For details on the AD2000 bracket calculation see S3/4 Vertical vessels with brackets (Behälter mit Tragpratzen).

Conclusions

General

For all code calculations, a reinforcement plate decreases the stresses in the shell. The plate must have a width and height that is in proportion with the bracket and the shell.

WRC

The WRC calculation code can be used for a bracket calculation. All various loads can be taken into account, but WRC only calculates the stresses in the shell and not the stresses in the webs or support plate.

EN13445

The EN13445 bracket calculation only calculates the stresses in the shell and not the stresses in the webs or the support plate. Only the web spacing and bracket/plate height are taken into account to calculate the maximum allowable bracket load. When the web spacing is smaller than half the bracket height, the maximum allowable bracket load will decrease for type A, B, and C. When there is no web spacing with only one web, the maximum allowable bracket load gets decreased by half.

The bracket width is only relevant for type D in the calculation of the maximum allowable bracket load. The reinforcement plate width is not directly relevant in the calculation, but must be in proportion with the plate height.

Different allowable stresses for non-similar materials are taken into account.

AD2000

The AD2000 bracket calculation does calculate the stresses in the webs and the support plate. The number of webs and the web thickness determine the maximum buckling stress and compression force of the web. The bracket width and the support plate thickness determine the maximum bending stress in the support plate.

The reinforcement plate width and height are directly relevant in the calculation. The plate width must be in proportion with the plate height.

Different allowable stresses for non-similar materials are taken into account.

WRC Bracket

Geometry

Dimensions and loads bracket

Stresses

Solid attachment with or without reinforcement plate

EN13445 Bracket

Geometry

Dimensions and loads bracket type A

Dimensions and loads bracket type B

Dimensions and loads bracket type C

Dimensions and loads bracket type D

AD2000 Bracket

Geometry

Dimensions and loads bracket

By: Alex Meels