Analysis of Isolated Footing using Elastic Foundation (Springs) in Abaqus

  1.  Choose Units, i.e., MKS or FPS. For this problem, we will use N, m and seconds as units.
  2. Make Rectangular footing in Sketch in Parts. Give it thickness as we want to model it as Solid Plate. Take footing dimension as 2x2x0.5
  3. Define Material as Concrete density (23.60) (note: correct this value when you practice it to 23.60e3), Elasticity (20e6) and Poisson’s ratio (0.2).
  4. We need to partition the plate so that we get point for application of load in centre. Tools>Partition in Part Module.
  5. Assign instance in assembly and then define interaction of Elastic Foundation in interaction module. Give value of Spring as 1. Note that the purpose of taking simplified value of load, dimension and spring is to get easy to interpret value of deflection to verify calculations.
  6. Mesh the footing from mesh module.
  7. Define load application step and apply concentrated load of 4 in negative 3-direction.
  8. Create Job and run the analysis.
  9. Open Result and check maximum deflection. As applied pressure is 4/4 = 1 and resisting stiffness per area is also 1 so from F = K*x, the resulting deflection will be 1 units. Again note that such values are pre-decided to have an easy cross-check on calculations.
  10. Check plots and deflection contour. And save the database cae file.

CAE file of abaqus can be downloaded from: CAE file

RampCalc0.1 – Parametric input for ramp in FE.

This program calculate data of beam, col and slab for ramp. It creates CSV file that can be used in sap2k or any FE package. It requires gnuoctave/matlab to work. You can download it from here:

Scripts Info:

  1. spiral.m = calculate and plot ramp in octave/matlab
  2. beams.m  = calculate data of beam for ramp to be used in FE
  3. cols.m    = calculate data of columns for ramp to be used in FE
  4. slabs.m   = calculate data of triangular slab for ramp to be used in FE

Background Theory:

Circle plot requires x = r*sin(t) and y = r*cos(t) where t increments from 0 to any given radians. If we increment z from 0 to given height h with some increment, and plot with x and y of a circle,  we will get a 3D spiral curve. Two such spiral curve can be used to calculate data point for ramp. Below is the sample code. You can run this by copy and paste directly in gnu octave or matlab or  create script out of it.

Ramp plot in octave
Ramp plot in octave

By using, beams, cols and slabs script function, csv data will be created that can be formatted as per any finite element code. Here I formatted it for sap2K.

Ramp view in sap2k
Ramp view in sap2k

A spreadsheet with sample sap2k format is attached with this code. Below is video tutorial explaining usage of this code:

 

CCX on Android Devices

Today smart phones have revolutionized Engineering Computations. Computer Aided Engineering (CAE) is now more easy and accessible with help of android tablets and phones.

CalculiX CrunchiX Solver – ccx is one of the most powerful Multiphysics GNU Finite Element Solver. This post is about how to compile and run gnu ccx on android. The code tested on HTC Incredible S and Android version 2.3.3.

If you are familiar with ccx or you can execute abaqus inp files using ccx, then, this script is helpful to you. Following steps show how to compile and run ccx on android.

1. Install Prerequisite Apps in Android:

a. Required android apps:

  1. GNURoot Wheezy by Corbin Champion
  2. GNURoot by Corbin Champion
  3. Free disk space on sdcard (better to have more than 6GB) and internal memory (better to have more than 500MB).

b. Required packages on Rootfs of GNURoot (Wheezy arm os):

  1. make
  2. gfortran
  3. gcc
  4. wget
  5. sed
  6. bzip2

2. Compiling ccx:

  1. Open GNUROOT
  2. Launch rootfs as fake root
  3. Download the script by following command:

    Or you can use tar files of cxbuild4mob. Untar and use it. Do not forget to go through readme file inside tar folder. Link of tar file is:
  4. Make script executable and then run it. Estimate downloading and compilation time for ccx is about 3 hours.

3. How to use ccx on Android:

  1. Open GNURoot

    GNURoot
    Fig. 1: GNURoot
  2. Check Launch as Fake Root option then press Launch Rootfs button.

    Rootfs
    Fig 2: Rootfs with Fake Root option checked
  3. Change current directory to folder where inp file exists. Verify by ls command and then run it under ccx.

    inp file
    Fig 3: Verify inp file.
  4. Check for errors in ccx log.

    Output log
    Fig. 4: Output Log of ccx.
  5. Verify output files.
    Ouput files of ccx
    Fig. 5: Output files of ccx

     

4. References:

  1. CalculiX CrunchiX
  2. GNURoot

Highlighting Syntax in gedit for CalculiX CrunchiX inp file for Enhanced Readability

CalculiX is a free software nonlinear three-dimensional finite element program for structural applications. Following steps results in syntax highlight of inp file in gedit:

  1. Add .xml in ~/.local/share/mime/packages named ccx.xml with following content:

  2. Update mime-database as:

  3. Add ccx.lang file in /usr/share/gtksourceview-3.0/language-specs or in path resulting from following command:

    The content of ccx.lang is:

  4. Open inp file and select gedit program to open.
  5. If you dont like or face problem then revert back the inp files to plain text as:

Syntax Highlight Files can be downloaded from below link:
Download Syntax Highlight Files.

before syntax highlight
Fig.1: Before Syntax Highlight of CCX input file.
after syntax highlight
Fig.2: After Syntax Highlight of CCX input file.

 

Reference:

  1. Gedit New Language File
  2. Language Definition v2.0 Tutorial
  3. SuperUser.com
  4. CalculiX CrunchiX