Static initialization

Samyog

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Dec 6, 2019, 1:27:43 PM12/6/19

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Hello everyone,

I have a 2D SSI model with I-soil and linear elastic structure. The soil has periodic boundary on vertical faces and non-reflecting at base. Seismic force input is applied to the base in horizontal direction. The first 2 seconds in the velocity input has a value of 0. Inertia is disabled in the first time step (0.005s).

When I look at the output before 2 seconds, the displacements are nearly constant. But, the accelerations don't go to zero (near the interface). I have attached four images. They represent the state at time 0.05s. How can I fix this problem?

Thank you,

Samyog

d0x.png

d0y.png

x05.png

y05.png

William M. Hoffman

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Dec 9, 2019, 9:34:06 AM12/9/19

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Samyog, can you send the input file and mesh etc?

-Will

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Samyog

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Dec 9, 2019, 10:10:06 AM12/9/19

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Hello Will,

It is attached.

Thank you

Samyog

On Monday, December 9, 2019 at 9:34:06 AM UTC-5, William M. Hoffman wrote:

Samyog, can you send the input file and mesh etc?

-Will

From: <mastodo...@googlegroups.com> on behalf of Samyog <samy...@gmail.com>
Date: Friday, December 6, 2019 at 11:29 AM
To: mastodon-users <mastodo...@googlegroups.com>
Subject: [EXTERNAL] [mastodon-users] Static initialization

Hello everyone,

I have a 2D SSI model with I-soil and linear elastic structure. The soil has periodic boundary on vertical faces and non-reflecting at base. Seismic force input is applied to the base in horizontal direction. The first 2 seconds in the velocity input has a value of 0. Inertia is disabled in the first time step (0.005s).

When I look at the output before 2 seconds, the displacements are nearly constant. But, the accelerations don't go to zero (near the interface). I have attached four images. They represent the state at time 0.05s. How can I fix this problem?

Thank you,

Samyog

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https://github.com/idaholab/mastodon
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input30.csv

Layer1.csv

Layer2.csv

Layer3.csv

Layer4.csv

Layer5.csv

Layer6.csv

NMRH02_E0_Quad4_x4_12.5Hz.e

SiteNMRH02_E0_Quad4_x4_12.5Hz.i

Samyog

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Jan 15, 2020, 3:56:54 PM1/15/20

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Hello everyone,

I am attaching an input file with I-soil subjected to gravity loading only. Finite acceleration is observed in horizontal directions. Is this spurious?

Thank you

Samyog

backbone29.csv

gravity_test_100x100x100_ramped.i

rampedgravity.csv

Chandrakanth Bolisetti

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Jan 27, 2020, 10:48:10 PM1/27/20

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Hi Samyog,

Just letting you know that I am still trying to look into this. Been quite busy so it’s taking a while.

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Chandu

From: mastodon-users <mastodo...@googlegroups.com> on behalf of Samyog <samy...@gmail.com>

Date: Wednesday, January 15, 2020 at 1:58 PM
To: mastodon-users <mastodo...@googlegroups.com>

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KT Kim

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Feb 7, 2020, 12:41:13 PM2/7/20

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Hi Samyog,

In order to stabilize soil response under gravity loading, the following two options are recommended among others:

1. Use a "Control block" to disable inertial kernels during the time duration of your gravity phase.

2. Apply a gravitational acceleration using a slowly ramping-up function.

To reduce a stabilization time, it is better to use the two options at the same time.

Please make sure that an input of "end_time" in a Control block should be set at some time steps after gravity loading is done.

In your case, I set the end_time to to be at 0.27 sec. (your ramping-up gravity load is full at 0.25 sec.)

See the attached fig1 and fig 2.

The above recommendation is only for a gravity analysis with a fixed boundary condition at your model base.

For an earthquake simulation (apply an acceleration input to the soil base), the base condition needs to be released and acceleration input is prescribed (e.g, zero acceleration during the gravity phase)

In this case without a fixed boundary condition at the soil base even at the beginning of the gravity loading phase, using only the control block option is good enough (without ramping-up gravity loading).

Please use a proper time range of the control block (from "start_time" to "end_time") to re-activate inertial kernels before a dynamic phase.

e.g., "end_time" should be set prior to the start time step of your dynamic input.

BTW, as I ran your input file, I could not see the finite acceleration in a horizontal direction. Can you share your input file showing this response?

- KT

fig1.png

fig2.png

KT Kim

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Feb 7, 2020, 1:22:10 PM2/7/20

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Samyog,

Regarding the dynamic simulation that I mentioned in the previous post, please see the attached input files and resulting response at the top of soil.

Best,

KT

samyog_mod.i

fig3.png

sineWave01.txt

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