Overview The SystemMilcaModel is the central class in milcapy that represents your entire structural model. It acts as a container that collects and manages all structural components including materials, sections, nodes, elements, load patterns, and analysis results.
Creating a Model
Import milcapy
from milcapy import SystemMilcaModel
Initialize the model
model = SystemMilcaModel()
Add components
Add materials, sections, nodes, elements, and loads to build your structural model.
Model Components The SystemMilcaModel organizes structural data into the following collections:
Materials Dictionary of material definitions with elastic properties
Sections Cross-sectional properties linked to materials
Nodes Geometric points in 2D space
Elements Structural members connecting nodes
Load Patterns Collections of applied loads and boundary conditions
Results Analysis outputs for each load pattern
Complete Example from milcapy import SystemMilcaModel # Create a new structural model model = SystemMilcaModel() # Add a material (concrete) material = model.add_material( name = "C25" , modulus_elasticity = 25e9 , # Pa poisson_ratio = 0.2 , specific_weight = 24000 # N/m³ ) # Add a rectangular section section = model.add_rectangular_section( name = "SEC-30x50" , material_name = "C25" , base = 0.30 , # m height = 0.50 # m ) # Add nodes node1 = model.add_node( id = 1 , x = 0.0 , y = 0.0 ) node2 = model.add_node( id = 2 , x = 4.0 , y = 0.0 ) node3 = model.add_node( id = 3 , x = 4.0 , y = 3.0 ) # Add a frame member (beam) member = model.add_member( id = 1 , node_i_id = 1 , node_j_id = 2 , section_name = "SEC-30x50" , beam_theory = "TIMOSHENKO" ) # Add boundary conditions model.add_restraint( node_id = 1 , ux = True , uy = True , rz = True ) # Fixed support model.add_restraint( node_id = 2 , ux = False , uy = True , rz = False ) # Roller support # Create a load pattern load_pattern = model.add_load_pattern( name = "DL" , self_weight_multiplier = 1.0 ) # Add loads model.add_point_load( node_id = 3 , load_pattern_name = "DL" , fx = 0.0 , fy =- 10000.0 , # 10 kN downward mz = 0.0 )
Model Data Structure The model stores components in dictionaries for efficient access:
# Access materials by name material = model.materials[ "C25" ] # Access sections by name section = model.sections[ "SEC-30x50" ] # Access nodes by ID node = model.nodes[ 1 ] # Access members by ID member = model.members[ 1 ] # Access load patterns by name load_pattern = model.load_patterns[ "DL" ]
Element Type Collections milcapy supports multiple element types, each stored in its own collection:
Collection Element Type Description model.membersFrame/Beam elements 3 DOF per node (ux, uy, rz) model.trussesTruss elements 2 DOF per node (ux, uy) model.cstsTriangle membrane Constant Strain Triangle model.membrane_q3dofQuad membrane (3 DOF) Q6, Q6IMod with drilling DOF model.membrane_q2dofQuad membrane (2 DOF) Q4, Q6I, Q8 elements
All element collections use integer IDs as keys, making it easy to reference specific elements: model.members[1], model.trusses[2], etc.
Analysis and Visualization The model provides properties for analysis and visualization:
# Analysis manager model.analysis = AnalysisManager(model) # Plotter for visualization model.plotter = Plotter(model) # Post-processing options model.postprocessing_options.factor = 10 # Deformation scale factor model.postprocessing_options.n = 17 # Number of divisions # Plotter options model.plotter_options.show_node_labels = True model.plotter_options.show_member_labels = True
Global Matrices After analysis, the model stores the global system matrices:
# Global stiffness matrix (assembled from all elements) K = model.global_stiffness_matrix # Load vectors for each load pattern F = model.global_load_vector[ "DL" ] # Load vector for "DL" pattern
Best Practices Naming Convention : Use descriptive names for materials, sections, and load patterns. For example: "C25" for concrete grade, "SEC-30x50" for section dimensions, "DL" for dead load.
Unique Identifiers : All nodes and elements must have unique integer IDs. Attempting to add a node or element with an existing ID will raise a ValueError.
Material Before Section : Always add materials to the model before creating sections that reference them.
Nodes Before Elements : Ensure all nodes are added to the model before creating elements that connect them.
Next Steps
Materials & Sections Learn about defining material properties and cross-sections
Nodes & Elements Understand how to create the structural geometry
Load Patterns Add loads and define load cases
Boundary Conditions Apply supports and restraints
