Robustness and accuracy of model-free structural health monitoring

Research papers, University of Canterbury Library

Rapid, accurate structural health monitoring (SHM) assesses damage to optimise decision-making. Many SHM methods are designed to track nonlinear stiffness changes as damage. However, highly nonlinear pinched hysteretic systems are problematic in SHM. Model-based SHM often fails as any mismatch between model and measured response dynamics leads to significant error. Thus, modelfree methods of hysteresis loop tracking methods have emerged. This study compares the robustness and accuracy in the presence of significant measurement noise of the proven hysteresis loop analysis (HLA) SHM method with 3 emerging model-free methods and 2 further novel adaptations of these methods using a highly nonlinear, 6-story numerical structure to provide a known ground-truth. Mean absolute errors in identifying a known nonlinear stiffness trajectory assessed at four points over two successive ground motion inputs from September 2010 and February 2011 in Christchurch range from 1.71-10.52%. However, the variability is far wider with maximum errors ranging from 3.90-49.72%, where the second largest maximum absolute error was still 19.74%. The lowest mean and maximum absolute errors were for the HLA method. The next best method had mean absolute error of 2.92% and a maximum of 10.51%. These results show the clear superiority of the HLA method over all current emerging model-free methods designed to manage the highly nonlinear pinching responses common in reinforced concrete structures. These results, combined with high robustness and accuracy in scaled and fullscale experimental studies, provide further validation for using HLA for practical implementation.

“It’s about the most needy children”: A Foucauldian analysis of school soc…

Research papers, University of Canterbury Library

INTRODUCTION: After the 2011 Canterbury earthquake, the provision of school social work was extended into a larger number of schools in the greater Christchurch region to support discussions of their practice priorities and responses in post-earthquake schools. FINDINGS: Two main interpretations of need are reflected in the school social workers’ accounts of their work with children and families. Firstly, hardship-focused need, which represented children as adversely influenced by their home circumstances; the interventions were primarily with parents. These families were mainly from schools in low socioeconomic areas. Secondly, anxiety-based need, a newer practice response, which emphasised children who were considered particularly susceptible to the impacts of the disaster event. This article considers how these practitioners conceptualised and responded to the needs of the children and their families in this context. METHOD: A qualitative study examining recovery policy and school social work practice following the earthquakes including 12 semi-structured interviews with school social workers. This article provides a Foucauldian analysis of the social worker participants’ perspectives on emotional and psychological issues for children, particularly those from middle-class families; the main interventions were direct therapeutic work with children themselves. Embedded within these practice accounts are moments in which the social workers contested the predominant, individualising conceptualisations of need to enable more open-ended, negotiable, interconnected relationships in post-earthquake schools. IMPLICATIONS: In the aftermath of disasters, school social workers can reflect on their preferred practice responses and institutional influences in schools to offer children and families opportunities to reject the prevalent norms of risk and vulnerability.