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This chapter presents principles and justification of diagnostic load tests of bridges as normally performed. Normally, diagnostic tests serve to verify and adjust the predictions of an analytical model. However, as presented in the chapter, the results of a diagnostic load test in a bridge can also serve other objectives. Several examples of application are presented with the main objective not only to show how the tests are carried out, but chiefly to introduce which are the main issues to take into account to obtain accurate and reliable results that can be used in the assessment of the actual capacity of the bridge. In the case of static tests, conclusions regarding the measurement stabilization time are presented. For dynamic tests in railway bridges, the extrapolation to lower and higher speeds is also discussed., Postprint (published version)

The load testing method has considerable possibilities in bridges with the objective of their safety assessment. One type of load tests is proof load. Proof load testing is a full-scale and non-destructive examination of load-carrying capacity. Proof-load testing has been applied to various types of structure in many parts of the world. Originally, it provided a way to check the design assumptions and quality of construction. Later, it became an effective approach to assessing load-carrying capacity of existing structures. The aim of the proof load test is to discover hidden mechanisms of response that can not appear under “normal” levels of load, but that develop at higher ratios of load and may increase the bridge load capacity. For this reason, in such test, the load introduced in the bridge is relatively high and due to the risks of damaging the structure, this type of tests is restricted to bridges that have failed to pass the most advanced theoretical assessment or when such theoretical assessment is not possible due to the lack of bridge documentation. The objective of this test is to directly obtain the maximum allowable load in the bridge with a required safety level. Acoustic emission has been identified as a useful technique in the follow up of the loading process in proof load tests in order to stop the load increase before any damage can be inflicted to the bridge. In the paper the results of field-test of Barcza bridge, a three span concrete bridge made of pre-stressed pre-casted beams, are presented. Thanks to the AE signals it was possible to evaluate the cracking limits without introducing any significant damage to the girders., Peer Reviewed, Postprint (published version)