Span Load Testing

Span load testing is a method to assess the flexural capacity and overall structural integrity of bridge spans by applying controlled loads and monitoring the structure’s response, such as strains, rotations, deflections, and vibrations. 

Here’s a more detailed explanation:

• Purpose:
  • To evaluate the true load-bearing capacity and engineering reliability of structures. 
  • To assess the condition and safety of a bridge, especially when there are concerns about excessive creep deflection, material defects, structural deterioration, or unknown structural strength. 
  • To verify if the maximum deflection and percentage recovery are within permissible limits. 
• How it’s done:
  • Loads are applied in stages, often using loaded vehicles or dumpers, on a selected span or part thereof. 
  • The structure’s response (strains, rotations, deflections, and vibrations) is recorded using appropriate instrumentation. 
  • The test is conducted in accordance with contract requirements, unless otherwise specified. 
• Considerations:
  • Types of Structures: Span load tests are used for various structures like metro rail projects, flyovers, industrial slabs, balconies, and bridges. 
  • Static and Dynamic Loading: Static load tests evaluate the bridge’s response to sustained loads, while dynamic load tests assess its behavior under moving loads and various dynamic conditions. 
  • Calculations: Calculations after the test are complex and require interaction with structural experts and clients before a report is finalized. 
• Types of Load Testing:
  • Static Load Testing: Involves applying static loads to the structure to assess its static behavior. 
  • Dynamic Load Testing: Involves applying dynamic loads (e.g., vehicle loads) to the structure to assess its dynamic behavior. 
  • Skip-Loading: In the case of continuous multi-span structures, load tests may involve skip-loading (loading spans 1 and 3, for example) to create maximum moments at mid-span, or loading consecutive spans to create maximum moments at support.