A continuous beam is a good first model in Midas Civil. It is the basic idea behind continuous bridge girders, and you can check the software results by hand. This tutorial walks through the whole workflow.
Example data (for practice only):
- Spans: 2 × 10 m (total length 20 m)
- Section: Rectangular, 400 mm wide × 800 mm deep
- Material: M30 concrete
- Supports: Pinned at the left end, rollers at the middle and right end
- Loads: Self-weight plus an additional 25 kN/m uniformly distributed load
Step 1: Start a new project and set units
Open Midas Civil, go to File > New Project, and save the file. Set the units to kN and m in the unit system box at the bottom of the screen.
Step 2: Define the material
Go to Properties > Material Properties, add a new material, and choose Concrete. Select the Indian standard from the design code list and pick grade M30 from the database. The modulus of elasticity should come out near 27,000 MPa. If your version gives a very different value, check that the code and grade are correct.
Step 3: Define the section
Go to Properties > Section Properties and add a new section. Use the Value tab, choose the rectangular shape, and enter H = 0.8 m and B = 0.4 m.
Step 4: Create the nodes and elements
- Create a node at (0, 0, 0) using Node/Element > Create Nodes.
- Select the node and extrude it into elements using Node/Element > Extrude Elements. Extrude a beam element 20 times at 1 m in the x-direction.
Using 1 m elements gives enough points for smooth diagrams. Check that you now have 21 nodes and 20 elements.
Step 5: Apply boundary conditions
Go to Boundary > Supports.
- Node 1 (x = 0): restrain Dx, Dy, Dz, and Rx (pinned in the plane)
- Node 11 (x = 10 m): restrain Dy, Dz, and Rx (roller)
- Node 21 (x = 20 m): restrain Dy, Dz, and Rx (roller)
Because this is a plane problem, also restrain the out-of-plane movement (Dz) and the rotation about the beam axis (Rx) at all supports, or use the model type setting for plane analysis. Check this against your Midas Civil version.
Step 6: Define load cases and apply loads
- Go to Load > Static Loads > Static Load Cases and create two cases: Self Weight (type: Dead Load) and UDL (type: Dead or Live Load as you prefer).
- Apply self-weight with Load > Self Weight, using Z = -1 for the gravity direction.
- Apply the 25 kN/m load using Load > Element Beam Loads. Select all elements, choose the UDL load case, set the direction to global Z, and enter -25 kN/m.
Step 7: Create a load combination
Go to Results > Load Combinations and create a combination. For serviceability checks, use factors of 1.0 on each case. For strength design, use the factors required by your design code and project.
Step 8: Run the analysis
Click Analysis > Perform Analysis. Look in the message window for errors or warnings before opening the results.
Step 9: Check the results
Use Results > Reactions and Results > Forces > Beam Diagrams for reactions, bending moment, and shear force. Use Results > Deformations for the deflected shape.
Step 10: Verify with a hand calculation
Never trust a model without a quick check. The total UDL is 8 + 25 = 33 kN/m (self-weight = 0.4 × 0.8 × 25 = 8 kN/m). For two equal spans with a uniform load, the standard results are:
| Quantity | Formula | Value |
|---|---|---|
| Middle support reaction | 1.25 × w × L | 412.5 kN |
| End support reaction | 0.375 × w × L | 123.75 kN |
| Hogging moment at middle support | w × L² / 8 | 412.5 kN·m |
| Maximum sagging moment (at 0.375L from end) | 9 × w × L² / 128 | about 232 kN·m |
If Midas Civil gives results within a small difference of these values, your model is set up correctly. A significant difference usually means a problem with the supports, the units, or the load direction.
Common mistakes to avoid
- Wrong units, which affects every result.
- Applying loads in the wrong direction. Gravity acts in negative global Z in Midas Civil by default.
- Applying self-weight twice, or forgetting it.
- Leaving the model unstable because of too few supports.
- Not checking the message window before reading results.
What next?
Once this model works, try adding a moving load (traffic lanes and vehicle loads), temperature loads, or a prestress tendon. I’ll cover these in later posts.
Do you use Midas Civil for bridge or building projects? Tell me in the comments which topic you want next.
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