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Application of acoustic emission measurement as stop criteria in proof loading

BackgroundThe safety of the large amount of the existing infrastructures is of great importance to the society, which requires the development of an accurate assessment tool. For the concrete slab bridges, because of the uncertainties of the aging of the materials, conventional assessment approaches cannot provide an accurate evaluation. for those bridges, proof loading is considered as a interesting option. With proof loading, a predefined load is applied on the target structure to generate certain inner force at the critical section, while the response of the structure is monitored. As a critical aspect in proof loading, the structure has to be prevented from unwanted damage by defining a set of stop criteria based on the measure-ments. This is especially important for shear failure.

Acoustic emission (AE) is considered as an attractive alternative to the conven-tional measurements, which are mostly focused on the deformation on the surface of the structure. Acoustic

Emission refers to the generation of transient elastic waves produced by a sudden redistribution of stress in a material. In the case of concrete, it is mostly related to the opening of cracks and shear displacement within a crack. Although shear failure is in general a brittle failure process, the development of the critical shear crack usually starts from the increase of the shear displace-ment of the already existing flexural cracks and the formation of secondary cracks along the tensile reinforcement. These processes could be monitored through AE measurement.

Research methodologyThis research is focused in general two aspects. First of all, the shear failure process has to be studied thoroughly with the help of both experimental data and non-linear finite element analysis in order to determine the potential warning mechanisms. That will be translated into the target AE parameter during proof loading. Secondly, the AE signals measured from experiments has to be studied to obtain the transfer function of

AE signal properties in concrete. The output will be a recommendation of AE sensor arrangement for proof loading.

Onsite test at Ruytenschildt bridge in Friesland

AE measurement during a proof loading

SupervisorsDr.ir. Y. YangDr.ir. P.L. PahlavanProf.dr.ir. D.A. Hordijk

Additional informationDr.ir. Y. Yangyuguang.yang@tudelft.nl

MSC graduation work