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The University of Aberdeen has conducted research into ground anchorage systems since the early 1980's. During this time, the non-destructive GRANIT system (GRound ANchorage Integrity Testing) has been developed for anchorages in rock. The system is based on observing the dynamic response from anchorages to which an impulse of a known intensity has been applied. This technique has been proven to be a reliable system to assess the integrity of rock anchorages, which is then used as a base to study the integrity of soil anchorages. This research aims to implement a non-destructive testing system at small scale size and full scale stress levels by means of centrifuge modelling at the University of Dundee. Accordingly, centrifuge modelling was undertaken to monitor and assess the dynamic response of soil anchorages installed in dry sand reinforcing a retaining wall in 3x3 anchorage array sets, subject to different post tension levels within different bonding ratios and different inclinations. In order to perform non-destructive testing, an In-flight Robotic Manipulator, previously developed, was used to apply a post tension load followed by an impact load to the anchorage head to obtain the dynamic response of the system. Anchor frequency response signatures were then evaluated in order to validate the consistency of results obtained. The practical importance of this research is that non-destructive testing may be usable to assess the soil anchors integrity to define the relationship between both anchor load and geometrical characteristics with frequency response accomplished using centrifuge modelling. This research presents a further development of the physical model in which additional instrumentation is included in order to obtain load/deflection information of the anchor head, which has been proven crucial for monitoring load on rock anchorage. Additionally, load distributions along scaled model soil anchors are measured and found to reduce gradually within the fixed length, similarly as it was reported for the fixed length of rock anchorages. Furthermore, a lumped parameter model for a single soil anchorage was adapted to investigate the dynamic response under the same physical and geometrical characteristics studied during centrifuge modelling. Mode shapes helped to understand the origin of some of the frequency modes present in the frequency response of the centrifuge results. The results from the numerical and centrifuge models were compared and good agreement was observed. Soil anchorage does not show as much frequency shift as was observed for rock anchorages under different post tension load, suggesting that the bonding strength of the fixed length with the surrounding ground plays an important role on the dynamic response of the system. The accomplishment of the assessment of soil anchorage can not be exclusively judged on its ability to diagnose controlled changes under centrifuge and numerical modelling. Therefore a preliminary phase to assess a soil anchorage under field conditions was carried out deploying the GRANIT system. This research showed that the GRANIT non-destructive testing technique has potential for use in soils, but that the results are not as well defined as in rock, necessitating more careful characterization of each anchorage signature response.

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This thesis presents a finite element (FE) modelling approach investigating the effects of corroded shear reinforcement on the capacity and behaviour of shear critical reinforced concrete (RC) beams. Shear reinforcement was modelled using a “locally smeared” approach, wherein the shear reinforcement is smeared within a series of plane-stress concrete elements at the specific stirrup location. This was done with the objective of incorporating both the reduction in cross-sectional area due to corrosion and the corresponding expansion of corrosion products build up. Corrosion damage was incorporated through equivalent straining induced by the corrosion build up on the affected surrounding concrete where the concrete cover was treated as a thick-wall cylinder subjected to internal pressure. Strains were introduced in the FE model using fictitious smeared horizontal pre-stressing steel, with a compressive pre-straining level related to the degree of corrosion penetration of the reinforcement. The FE modelling approach was first validated against published test data of shear critical RC beams with and without stirrup corrosion. The proposed modelling approach successfully reproduces the load deformation response as well as the failure mode and cracking patterns of the published experimental tests. Upon validation of the FE model, the work was extended to a parametric analysis of important shear design variables, such as the shear span-to-depth ratio, beam width and stirrup spacing The FE analyses were carried out for three increasing levels of corrosion (low, moderate and high) applied to affected stirrups within the critical section of the beams and based on steel mass loss (10%, 30% and 50%, respectively). In general, the results show a reduction in load carrying capacity accompanied by a softening of the load-deformation curves with each increasing level of corrosion. In most of the cases, a reduction in deflection associated to peak loads was also observed for moderate and high levels of corrosion. The impact of the various parameters was studied with respect to strength and deformation, as well as crack angle and mid-height horizontal strain. This was done in an effort to compare FE values to those provided by the CSA A23.3 design equations. The CSA A23.3 shear design equations were compared against FE analysis data in terms of residual shear strength estimation and individual component contributions to shear resistance (i.e., concrete and steel). The comparisons revealed an over conservative estimation for both strength and concrete contributions and an overestimation of the steel contribution. This divergence was attributed to a transition in shear behaviour within the critical section. Based on the progression of the concrete compressive struts with increasing corrosion and predicted crack angle, it was found that stresses in affected sections are redistributed towards adjacent undamaged material. The shear resistance mechanism generally transitioned from typical beam behaviour towards an arching-dominated one. Finally, based on important findings from the literature and the work conducted within this research, important considerations for assessment practice are suggested.

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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004. / Includes bibliographical references. Also available in electronic version. Access restricted to campus users.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2002. / Includes bibliographical references (leaves 131-136). Also available in electronic version. Access restricted to campus users.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed June 1, 2009) Includes bibliographical references (p. 117-124).