Dynamic body-load

Background

Represent a body/volume force that is applied on an Element object. This force is represented by a varying magnitude and direction that is applied on the element. The Load object created in this manner is transformed in the element level using its volume into nodal forces and then assembled directly to the global force vector. The dynamic body load direction needs to coincide with the global coordinate system.

REFERENCE:

• Bathe K. Jurgen, "Finite Element Procedures", Chapter 4: pages 161-166, Table 4.3, Prentice-Hall, 1996.

Pre-Analysis

The python Pre-Analysis in the 01-Pre_Process/Method/Attach.py file provides with an interface to create a DYNAMIC BODY LOAD. For example, to create a Dynamic body-load using json format, use:

• addLoad(tag, name, attributes):

  • tag : The identifier of this load, i.e., tag > -1
  • name : The Seismo-VLAB load class name, in this case 'ElementLoad'.
  • attributes : Specific properties for the created load, for example
    • 'fun' : The function identifier
    • 'list' : The identifier of the elements where this load acts upon
    • 'type' : The type of element load, in this case 'Body'.

  Example

  A DYNAMIC BODY LOAD can be defined using the python interface as follows:
  SVL.addLoad(tag=1, name='ElementLoad', attributes={'fun': 1, 'type': 'Body', 'list': [1,2,3,4,5]})

The information required to define the magnitude and direction of this Load is provided in the attributes['fun'] identifier. Thus, to create a DYNAMIC FUNCTION using the json format, use:

• addFunction(tag, name, attributes):

  • tag : The identifier of this function, i.e., tag > -1
  • name : The Seismo-VLAB function class name, in this case 'TimeSeries'.
  • attributes : The dynamic function information
    • 'dir' : The direction of the acting function
    • 'file' : The file where the load is going to be loaded. The file location is with respect to the main python script being executed

  The file format specified at attributes['file']='ricker.in' must have the structure shown in the figure:

  

  Example

  A DYNAMIC FUNCTION can be defined using the python interface as follows:
  SVL.addFunction(tag=1, name='TimeSeries', attributes={'file': 'ricker.in', 'dir': [25000.0, 0.0, 0.0]})
  

Application
Please refer to the D21-DY_Damped_Rectangular_BodyLoad_Elastic_Frame2.py file located at 03-Validations/01-Debugging/ to see an example on how a DYNAMIC BODY LOAD and its DYNAMIC FUNCTION are defined.

On the contrary, the 01-Pre_Process/Method/Remove.py file provides with an interface to depopulate the Entities dictionary. For example, to remove an already define Load, use:

• delLoad(tag):
  • tag : The identifier of the load to be removed, i.e., tag > -1

Now, to remove a already defined function, use:

• delFunction(tag):
  • tag : The identifier of the function to be removed, i.e., tag > -1

Run-Analysis

The C++ Run-Analysis in the 02-Run_Process/05-Loads/Load.cpp file provides the class implementation. A STATIC BODY LOAD is defined inside the "Loads" json field indicating its "Tag" as follows,

• {
      "Loads": {
          "Tag": {
              "name" : "ELEMENTLOAD",
              "attributes": {
                  "name": "TIMESERIES",
                  "type": "BODY",
                  "file": str,
                  "dir": [ ],
                  "list": [ ]
              }
          }
      }
  }
  

  Variable	Description
  Tag	Unique load object identifier.
  file	Represents the full path where the file is located.
  dir	Vector containing the direction of the force.
  list	List of Element identifiers that share this load.

  
  

  Attention

  Body forces are applied to the specified elements only if the material has density.

  The file provided at file for dynamic analysis contains the number of time steps, and then a vector with the varying intensities in time. The time step of such intensities is assumed to coincide with the time step of the simulation.

  Example

  A 2D DYNAMIC BODY LOAD acting on x-direction whose magnitude in time are ../Exterior.txt file and applied on elements 1,3,5, and 7:
  { "Loads": { "1": { "name" : "ELEMENTLOAD", "attributes": { "name": "TIMESERIES", "type": "BODY", "file": "/full/path/to/folder/Exterior.txt", "dir": [1.000, 0.000], "list": [1,3,5,7] } } } }