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Video 5 Course Guide: Columns & Beam Frames

This guide covers the transition from single-beam analysis to a full structural frame system using connected members. By tracing load paths before solving, we evaluate how gravity and lateral wind loads travel through a portal frame to fully fixed ground supports.

1. Frame Geometry & Load Paths​

Portal Frame Geometry:
The structure consists of two 4-meter vertical columns supporting a single 6-meter horizontal beam spanning across their tops.

Support Conditions:
Both column base nodes are fully fixed, locking all 6 degrees of freedom.

Gravity Load Path:
The self-weight of the top beam transfers to the supporting column joints below it, where forces travel down through the columns and discharge into the fixed base supports.

Wind (Lateral) Load Path:
Applied as a horizontal point load pushing from left to right at a top beam node. The lateral force creates moment and shear forces that transfer down the columns into the ground foundations.

Analysis Scope:
This initial frame analysis focuses on understanding force paths and load transfer across interconnected elements rather than code-checking column capacity.

2. Defining Script Geometry & Supports​

1. Point Coordinates & Lines​

Set up boundary points and connect them with line segments to construct the portal frame skeleton:

  • 2 vertical columns
  • 1 horizontal span
  • Sliders control the total frame height and span width

2. Cross-Section & Material​

Assign standard structural steel properties, such as S235 steel, and an I-section profile to the frame elements.

3. Element Conversion​

Feed the lines and cross-section parameters into the LineToBeam component to convert the geometric lines into Karamba structural members.

4. Fixed Supports​

Connect Support components to both column base nodes. Check all 6 degrees of freedom to establish fully fixed base conditions.

3. Applying Gravity and Wind Loads​

Gravity Load — Self-Weight​

Create the gravity load using a Loads component with its type set to Gravity. This automatically applies the self-weight of the structural elements downward.

Lateral Wind Load​

Construct the lateral load by generating a horizontal direction vector using Unit X.

Scale the force magnitude using Multiplication components, then feed the resulting vector into a Point Load component assigned to the top beam joint.

The resulting force pushes the frame horizontally from left to right.

4. Model Assembly & Sanity Checks​

Before reviewing structural results, inspect the assembled model output to confirm proper element connectivity.

Node Verification​

Pass the assembled model nodes into a List Length component.

The model should contain exactly:

4 structural joints

  • 2 base nodes
  • 2 top frame joints

Element Verification​

Pass the beam element list into another List Length component.

The model should contain exactly:

3 beam elements

  • 2 columns
  • 1 top beam

Passing both checks verifies that the frame geometry and connectivity are configured correctly before solving.

5. Analyzing Results & Unit Verification​

Visualizing Displacement & Moments​

Pass the solved model from Analyze into ModelView and BeamView.

Enable Moment My in BeamView to render the bending moment diagram across all frame members.

As the lateral wind load increases, the frame begins to sway from left to right, visibly deforming the columns and beam.

Sample Utilization​

Under combined loading, the capacity ratios vary across the frame members:

Frame MemberApprox. Utilization
Left Column47%
Top Beam25%
Right Column52%

The right column experiences the highest utilization in this example, while the top beam experiences the lowest.

Unit Settings Pitfall & Fix​

Unit Mismatch​

If Karamba units are set to Imperial, using an additional metric-to-imperial conversion component can incorrectly scale the applied load magnitudes.

This can result in unrealistically large displacement values.

Resolution​

Bypass the unnecessary conversion component by wiring the numeric sliders directly into the load input.

Always verify the Karamba/Grasshopper unit settings before interpreting structural results to ensure that loads, dimensions, and displacement values represent realistic structural behavior.

Component Reference

ComponentRole in Workflow
Loads (Gravity)Automatically calculates and applies downward self-weight across all frame members.
Unit X + MultiplicationConstructs the scaled horizontal force vector from left to right for the lateral wind load.
LineToBeamConverts Rhino/Grasshopper lines into Karamba beam elements with assigned steel profiles.
List LengthPerforms structural checks to verify the node count (4) and beam count (3).
BeamView (My)Visualizes bending moment diagrams and utilization color maps across the portal frame.
Beam DisplacementsOutputs numerical translation and rotation values for checking lateral drift and joint deflections.