1. Created analysis model
Validated analysis model
Verified analysis model
But do you really understand how your structure is behaving???

2. Sensitivity Analysis

3. Sensitivity Analysis
Investigate the effects of different values for features/parameters.
Why?
Better understanding of the behaviour of system being modelled.
How much is necessary?
Depends on how certain you are of the model behaviour.

4. Reference model results
Change 1 feature/ parameter
New revised model
New results
Change a different feature/ parameter
New revised model
New results
Change a different feature/ parameter
New revised model
New results
Change variables one at a time, go back to the reference model after each change.

5. Consider the parameters most indicative of the model behaviour:
Maximum deflection?
Maximum bending moment/shear force/axial force?
Lowest natural frequency?
Compare and report results without dimensions.
Use percentage difference +/- %
%diff = (value – reference value)/reference value  100
Or ratios
For more detail see:

6. Example The Model Geometry:
The model is created in 2D, in the x-y plane.
1.5m
1.3m
1.4m
1.4m
1.4m
1.4m
1.3m
100x100x3.6 SHS – for all top and bottom chord members and vertical members.
100x100x8 EA – for tension diagonals.

7. Model 1 – pin joints
Axial load
Displacement

8. Model 2 – fixed/rigid joints
Axial load
Bending moment

9. Model 3 – no bracing
Axial load
Bending moment

10. Structural system comparison
Comparison of results
Max Displacement at node 4 (mm)
% difference
ratio
Max Bending (kNm) %
difference
Max Axial (kN) compression
Reference - Model 1
Pinned truss -
-13.67
Model 2
Fixed truss
-1.4%
1.0
-13.52
-1.1%
Model 3
Vierendeel, no bracing
933.8%
10.5
-2.294
1872.5%
-10.62
-22.3%
Structural system comparison

11. Consider truss chord depth v diagonal depth
Reference model - Model 1 Pinned truss 100x100x3.6 SHS – for all top and bottom chord members and vertical members. 100x100x8 EA – for tension diagonals.

12. Model 4 – Equal sections Axial load Displacement
100x100x3.6 SHS – for all top and bottom chord members and vertical members. 100x100x3.6 SHS – for tension diagonals.
Axial load
Displacement

13. Model 5 – section d, Chords–Ties 2:1
100x100x3.6 SHS – for all top and bottom chord members and vertical members. 50x50x3.6 SHS – for tension diagonals.
Axial load
Displacement

14. Model 6 – section d, Chords–Ties 1:2
100x100x3.6 SHS – for all top and bottom chord members and vertical members. 200x200x5 SHS – for tension diagonals.
Axial load
Displacement

15. Truss chord depth v Diagonal depth
Comparison of results
Max Displacement at node 4 (mm) %
difference
ratio x
Max Axial (kN) compression
Reference Model 1
Pinned
SHS & EA -
-13.67
Model 4
Equal sections
+2.6%
1.02 0%
Model 5
d, Chords–Ties 2:1
+27.9%
1.28
Model 6
d, Chords–Ties 1:2
-12.3%
0.88
Truss chord depth v Diagonal depth