Evaluate structural fatigue using Arcade in the Enterprise portal and ArcGIS Online

Summary

Structural fatigue is the progressive weakening of a material or structure due to repeated stress cycles, eventually leading to cracks or failure even if the applied loads remain below the material's ultimate strength. Evaluating structural fatigue helps predict when infrastructure, such as bridges and buildings, require maintenance or reinforcement, preventing failures, and ensuring long-term durability.

This article provides the workflow to evaluate structural fatigue using Arcade in the ArcGIS Enterprise portal and ArcGIS Online. In this example, bridges made from different materials experience accumulated stress from frequent heavy vehicle crossings, eventually leading to structural fatigue and the need for maintenance.

Procedure

1. Log in to the ArcGIS Enterprise portal or ArcGIS Online and click Content > My Content.
2. Click the hosted feature layer to open the item page.
3. Add a new string field. Refer to Portal for ArcGIS: Add a field or ArcGIS Online: Add a field for instructions. In this example, a new field, 'Estimated_Lifespan', is added to the attribute table with three existing fields named 'Vehicle_Weight', 'Crossing_Frequency', and 'Bridge_Material'.
4. Open the Arcade window. Refer to Portal for ArcGIS: Calculate values for a field from the item page or ArcGIS Online: Calculate values for a field from the item page for instructions.
5. In the Expression box, specify the following Arcade expression:
   1. Define the material's relative fatigue resistance value.

var fatigueLimits = {
    'Steel': 100000,
    'Concrete': 50000,
    'Composite': 75000
};

2. Retrieve the data from the fields.

var vehicleWeight = $feature["Vehicle_Weight"];  // Weight in tons
var crossingFrequency = $feature["Crossing_Frequency"];  // Crossings per day
var materialType = $feature["Bridge_Material"];

3. Get the material fatigue resistance.

var fatigueLimit = DefaultValue(fatigueLimits[materialType], fatigueLimits['Concrete']);

4. Define a calibration factor to align with the expected results.

var calibrationFactor = 1000;

5. Calculate the total annual load from the vehicles.

var totalLoadPerYear = vehicleWeight * crossingFrequency * 365;

6. Compute the fatigue damage.

var annualFatigueDamage = totalLoadPerYear / (fatigueLimit * calibrationFactor);

7. Estimate the years until fatigue failure.

var fatigueYears = IIF(annualFatigueDamage > 0, Round(1 / annualFatigueDamage, 1), ">100");

8. Ensure that the minimum practical lifespan is displayed correctly.

fatigueYears = IIF(fatigueYears < 1, "<1", fatigueYears);

9. Return the estimated lifespan before maintenance is required.

"Estimated Bridge Fatigue Lifespan: " + fatigueYears + " years"

The code block below shows the example of the full working script:

var fatigueLimits = {
    'Steel': 100000,
    'Concrete': 50000,
    'Composite': 75000
};

var vehicleWeight = $feature["Vehicle_Weight"];  // Weight in tons
var crossingFrequency = $feature["Crossing_Frequency"];  // Crossings per day
var materialType = $feature["Bridge_Material"];

var fatigueLimit = DefaultValue(fatigueLimits[materialType], fatigueLimits['Concrete']);

var calibrationFactor = 1000;

var totalLoadPerYear = vehicleWeight * crossingFrequency * 365;

var annualFatigueDamage = totalLoadPerYear / (fatigueLimit * calibrationFactor);

var fatigueYears = IIF(annualFatigueDamage > 0, Round(1 / annualFatigueDamage, 1), ">100");

fatigueYears = IIF(fatigueYears < 1, "<1", fatigueYears);

"Estimated Bridge Fatigue Lifespan: " + fatigueYears + " years"

6. Click OK.

The image below shows the evaluated structural fatigue of the different bridges according to its material.