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The Assessment of deteriorated concrete structures using extended digital image correlation (EDIC)

Student thesis: Doctoral Thesis

Concrete structures in marine environments frequently experience long-term deterioration due to environmental exposure. This exposure results in surface damage with the subsequent spalling of concrete, which has a significant effect on the long-term durability of the structure. The reinforced concrete jetty investigated in this study suffered similar problems. The concrete jetty is located on the South East England coast. The jetty consists of a deck that is part precast and part in-situ cast, which is supported by steel, concrete and a sheet pile wall. Five decades after its construction, erosion by sea water is the most serious problem facing the jetty structure and has resulted in significant deterioration and surface damage.

This project was established to evaluate the damage level of the jetty using an extended non-destructive measurement approach with an FEA simulation. The basic non-destructive measurement technique used in this investigation is a digital image correlation (DIC) optical system. The current DIC technique is limited to detecting macro cracks; thus, this investigation aims to develop an Extended Digital Image Correlation (EDIC) method to extend the capability of the current DIC from measuring the strain field to detecting multiscale cracks and predicting micro crack propagation. There is an industrial necessity to enhance the damage assessment level based on micro-crack detection. The EDIC study was performed empirically and demonstrated an important role in detecting damaged zones and multiscale cracks, including micro- and macro-cracks of the concrete surface. The EDIC can be used for further studies on detailed damage mechanisms in concrete and other engineering materials, such as timber or masonry structures.

The assessment provide information on the current structural degradation, load bearing capacity and safety margin of the damaged jetty. To simulate the ageing jetty numerically, a material model of the ageing concrete was created in terms of the tested core samples obtained from the jetty structure, and the model was implemented in an UMAT subroutine in ABAQUS for FEA simulation. The mechanical properties of the ageing jetty obtained from the experimental tests proved to be suitable, with a compressive and tensile strength of approximately 67 MPa and 4.2 MPa, respectively, and the elastic modulus was 38728 MPa.

Using the DIC in situ assessment and FEA simulation, the damage evaluation was
completed. The results indicated a considerable decrease in the structural stiffness of the damaged jetty of approximately 40%. The load bearing capacity of the damaged jetty reported was approximately 240 tonnes. Despite the significant damage, the safety margin under the current practical loading condition (162 tonnes) is still high, i.e., approximately 1.48. However, due to the severe condition of the damaged jetty located in an aggressive marine environment and the loading impacts, it is highly recommended that the cracks and corrosion be immediately stopped and controlled. Furthermore, for safety reasons, any additional loads in conjunction with the current practical load (162 tonnes) should be avoided.
Original languageEnglish
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Award dateSep 2015
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