Bridge load testing is a common practice among bridge engineers for the assessment of bridge safety and serviceability.
Diagnostic load testing is one type of load test methods that can be used either as a means for estimating the load carrying capacity of an in-service bridge or as an acceptance test before the bridge is put into service.
Diagnostic Load Tests can be used to evaluate specific response characteristics of the bridge such as lateral load distribution and secondary stiffening effects and to validate the load rating analytical models.
Bridge diagnostic load testing usually involves installation of a variety of sensors, including:
- strain gauges,
- acceleration sensors,
- displacement sensors,
- highly sensitive rotation devices.
Sensors are normally installed on structural components.
The test is generally performed with controlled load situations.
Applied loads are typically limited to legal load levels or load levels that are known to be safe for a particular structure.
The main goal of the diagnostic load testing of bridges is to identify structural response (deformations, strains, etc.) for a given load condition.
The measured responses are compared with those that are derived from the analysis of the theoretical models, for the same loading condition.
Head to head comparison is then used as the basis for validating the theoretical model and defining how accurately the model simulates actual load paths.