Load test on concrete structures is conducted to evaluate their flexural capacity.The testing is required to determine the serviceability of the structure when the presence / effect of the strength deficiency and its remedial measures are not fully known or when the required dimensions and material properties for analysis are not available.The goal of this type of testing is to compare field response of the structure under test loads with its theoretical response. Load testing on structures can be further categorized into diagnostic testing and proof testing. Diagnostic testing methods provide the measurements necessary to analyze differential loading effects (i.e., moment, shear, axial force, deflection, etc.) present in various structural members due to applied loads. Proof-load testing aims at determining the magnitude and configuration of loads that cause critical structural components to approach their elastic limit.
Methodology of load testing typically include the determination of testing objectives and load configuration, the selection and placement of instrumentation, the adoption of appropriate analysis techniques, and the evaluation and comparison of test results and analytical results. In case of bridges, the load effect on a span can be produced either by building up pre-weigh units on loading imprints as per codal provision or by any other configuration that produces the load effect. Any of the appropriate method of load distribution between the girders can be adopted in aiming at the test load and its configuration on the span.
The test load is applied in increments and the response of the structural element recorded using appropriate instruments. The type of response may be strains, rotations, deflections, and vibrations.