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## Autodesk Robot Structural Analysis

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Posts: 4
Registered: ‎01-09-2013

# Hydrostatic pressure resultant forces

341 Views, 9 Replies
01-10-2013 05:12 AM

If a hydosatic pressure is applied to a panel that is on an incline does it apply the resultant force that would be perpendicular to the plate or would it just apply the corresponding depth.

i.e. if the base of the panel below is 2m below the water level is the force being applied at the base; the resultant of the horizontal and vertical or just simply 20 kN/m^2?

Product Support
Posts: 2,773
Registered: ‎12-17-2010

# Re: Hydrostatic pressure resultant forces

01-10-2013 05:22 AM in reply to: OscarGaunt

The hydrostatic load is applied in the direction that is perpendicular to a surface element.

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Artur Kosakowski
Support Specialist
Product Support
Autodesk, Inc.

Member
Posts: 4
Registered: ‎01-09-2013

# Re: Hydrostatic pressure resultant forces

01-10-2013 05:41 AM in reply to: Artur.Kosakowski

thank you for the quick response but I ust need to clarify something.

I understand the pressure is applied perpendicular to the surface of the panel, but my query is whether the force that is applied would be the same force as if the panel was vertical?

i.e. the pressure applied perpendicular to the face would be different at the same depths if their faces are at different angles.

Product Support
Posts: 2,773
Registered: ‎12-17-2010

# Re: Hydrostatic pressure resultant forces

01-10-2013 05:51 AM in reply to: OscarGaunt

No, for the inclined panel there are additional vertical reactions (in addition to 'the same' horizontal one).

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

Artur Kosakowski
Support Specialist
Product Support
Autodesk, Inc.

Contributor
Posts: 14
Registered: ‎01-09-2013

# Re: Hydrostatic pressure resultant forces

01-10-2013 06:57 AM in reply to: Artur.Kosakowski

Does this mean that this additional vertical reaction needs to be entered manually? (automatic hydrostatic pressure load does not work for inclined panels?)

Thank you

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Registered: ‎12-17-2010

# Re: Hydrostatic pressure resultant forces

01-10-2013 07:11 AM in reply to: vmorkunas

No, this means that  hydrostatic pressure works as hydrostatic pressure with no need for any other 'manual' actions

Artur Kosakowski
Support Specialist
Product Support
Autodesk, Inc.

Contributor
Posts: 14
Registered: ‎01-09-2013

# Re: Hydrostatic pressure resultant forces

01-18-2013 03:42 AM in reply to: Artur.Kosakowski

Artur,

Could you have a look at this test model I made? I can't make water pressure work correctly (unless I am making a mistake somewhere in my assumptions).

All panels have the same angle and geometry:

Panel 1 has an automatic water pressure applied:

Panel 2 has two load resultants applied in vertical and horizontal directions each equal of 19.6kN/m2 (water pressure at 2m deep), panel 3 has  only one variable load which is 19.6kN/m2 (vertical water pressure only) perpendicular to the panel plane. Panel 4 has a resultant of water pressure forces in both directions:

My understanding is that the correct results are given for panels 2 and 4 as water pressure acts in both vertical and horizontal directions. And it seems that automatic water pressure tool for inlclined panels in robot only takes one component of water pressure and applies it perpendicular to the plane (results for panel 1 match panel 3) which gives us less conservative/incorrect results.

Am I missing something here ?

Thanks

Contributor
Posts: 14
Registered: ‎01-09-2013

# Re: Hydrostatic pressure resultant forces

01-18-2013 03:48 AM in reply to: vmorkunas

And how do I attach the rtd file in this forum ? it is not on the allowed list of attachment extensions. Is it putting in online every time and creating a link?

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Posts: 2,773
Registered: ‎12-17-2010

# Re: Hydrostatic pressure resultant forces

01-21-2013 03:28 AM in reply to: vmorkunas

Zip it.

Artur Kosakowski
Support Specialist
Product Support
Autodesk, Inc.

Product Support
Posts: 2,773
Registered: ‎12-17-2010

# Re: Hydrostatic pressure resultant forces

01-21-2013 04:13 AM in reply to: vmorkunas

Assuming that the direction of the gravity is vertical regardless of the panel's inclination the values of horizontal reactions should be the same. For 2 m panel of 1 m width this should be always:

Total horizontal force Fh = 0.5 * (9.81 *  2) * 2 = 16.92

The top horizontal reactions should be 1/3 * 16.92 = 6.54

The bottom horizontal reaction should be 2/3 * 16.92 = 13.08

For the 45 deg inclination the total value of the pressure in the direction perpendicular to the panel is:

Fp = 0.5 * (9.81 *  2) * 2*sqrt2 = 27.66

The top reaction in the direction perpendicular to the panel is:

1/3* 27.66 = 9.22

The bottom is 2/3*27.66 = 18.44

The vertical and horizontal components are : 9.22/sqrt2 = 6.54 and 18.44/sqrt2 = 13.08 respectively

Artur Kosakowski
Support Specialist
Product Support
Autodesk, Inc.