Model Structure

The default parser accepts a three-part structure. They are:

1. Model Properties Setup

2. Analysis Properties Setup

3. Post-processing

The previous cantilever beam example is used here to explain the structure. The model is shown as follows.

node 1 0 0
node 2 1.34 0
material Elastic1D 1 132
element EB21 1 1 2 7.213 6.825 1
step static 1
fix 1 P 1
cload 1 0 23 2 2
cload 2 0 17 1 2
analyze
peek node 2
exit

Model Properties Setup

Anything before the first step command is treated as the setup of model properties. This part may include the definitions of nodes, elements, material models, loads, recorders, boundary conditions, etc. In this part, the order of commands does not affect the establishment of the model. So that the following reshuffled command flow creates the same model as the original one does, although, the EB21 element is created before the creation of its connected nodes.

element EB21 1 1 2 7.213 6.825 1
node 2 1.34 0
material Elastic1D 1 132
node 1 0 0

When the program parses those commands, the corresponding objects are only created and stored, but not initialized ( viz., no other information is required during the creation of a particular object). So the order does not affect anything in this part.

Analysis Properties Setup

The command block between the first step command the analyze command (or the precheck command) is the setup of analysis properties. A similar analysis flow which resembles the one of ABAQUS is used, that is, multiple steps can be defined in sequence in this part.

In this example, within step 1, a fixed boundary condition is applied to node 1, two concentrated loads are applied to node 2 along two directions. For the purpose of illustration, those two loads can be defined in two different steps as follows.

fix 1 P 1
step static 1
cload 1 0 23 2 2
step static 2
cload 2 0 17 1 2
analyze

Now the horizontal load is created in step 2 that follows step 1. It shall be noted the BC is created before the first step. By default, there is a step 0 with no step time, so the BC can be defined in either step 0 or step 1. Similar to ABAQUS, the sequence of multiple steps will affect analysis results.

Post-processing

The code block between the analyze command and the exit command belongs to post-processing. This part is less concerning and most commands have instant response.