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Research papers, University of Canterbury Library

Climate change and population growth will increase vulnerability to natural and human-made disasters or pandemics. Longitudinal research studies may be adversely impacted by a lack of access to study resources, inability to travel around the urban environment, reluctance of sample members to attend appointments, sample members moving residence and potentially also the destruction of research facilities. One of the key advantages of longitudinal research is the ability to assess associations between exposures and outcomes by limiting the influence of sample selection bias. However, ensuring the validity and reliability of findings in longitudinal research requires the recruitment and retention of respondents who are willing and able to be repeatedly assessed over an extended period of time. This study examined recruitment and retention strategies of 11 longitudinal cohort studies operating during the Christchurch, New Zealand earthquake sequence which began in September 2010, including staff perceptions of the major impediments to study operations during/after the earthquakes and respondents’ barriers to participation. Successful strategies to assist recruitment and retention after a natural disaster are discussed. With the current COVID-19 pandemic, longitudinal studies are potentially encountering some of the issues highlighted in this paper including: closure of facilities, restricted movement of research staff and sample members, and reluctance of sample members to attend appointments. It is possible that suggestions in this paper may be implemented so that longitudinal studies can protect the operation of their research programmes.<br /><br />Key messages<br /><ul><li>Recruitment and retention of longitudinal study participants is challenging following a natural disaster.</li><br /><li>The long-lasting, global effects of the Covid 19 pandemic will increase this problem.</li><br /><li>Longitudinal study researchers should develop protocols to support retention before a disaster occurs.</li><br /><li>Researchers need to be pragmatic and flexible in the design and implementation of their studies.</li></ul>

Research papers, University of Canterbury Library

A buckling-restrained braced frame (BRBF) is a structural bracing system that provides lateral strength and stiffness to buildings and bridges. They were first developed in Japan in the 1970s (Watanabe et al. 1973, Kimura et al. 1976) and gained rapid acceptance in the United States after the Northridge earthquake in 1994 (Bruneau et al. 2011). However, it was not until the Canterbury earthquakes of 2010/2011, that the New Zealand construction market saw a significant uptake in the use of buckling-restrained braces (BRBs) in commercial buildings (MacRae et al. 2015). In New Zealand there is not yet any documented guidance or specific instructions in regulatory standards for the design of BRBFs. This makes it difficult for engineers to anticipate all the possible stability and strength issues within a BRBF system and actively mitigate them in each design. To help ensure BRBF designs perform as intended, a peer review with physical testing are needed to gain building compliance in New Zealand. Physical testing should check the manufacturing and design of each BRB (prequalification testing), and the global strength and stability of each BRB its frame (subassemblage testing). However, the financial pressures inherent in commercial projects has led to prequalification testing (BRB only testing) being favoured without adequate design specific subassemblage testing. This means peer reviewers have to rely on BRB suppliers for assurances. This low regulation environment allows for a variety of BRBF designs to be constructed without being tested or well understood. The concern is that there may be designs that pose risk and that issues are being overlooked in design and review. To improve the safety and design of BRBFs in New Zealand, this dissertation studies the behaviour of BRBs and how they interact with other frame components. Presented is the experimental test process and results of five commercially available BRB designs (Chapter 2). It discusses the manufacturing process, testing conditions and limitations of observable information. It also emphasises that even though subassemblage testing is impractical, uniaxial testing of the BRB only is not enough, as this does not check global strength or stability. As an alternative to physical testing, this research uses computer simulation to model BRB behaviour. To overcome the traditional challenges of detailed BRB modelling, a strategy to simulate the performance of generic BRB designs was developed (Chapter 3). The development of nonlinear material and contact models are important aspects of this strategy. The Chaboche method is employed using a minimum of six backstress curves to characterize the combined isotropic and kinematic hardening exhibited by the steel core. A simplified approach, adequate for modelling the contact interaction between the restrainer and the core was found. Models also capture important frictional dissipation as well as lateral motion and bending associated with high order constrained buckling of the core. The experimental data from Chapter 2 was used to validate this strategy. As BRBs resist high compressive loading, global stability of the BRB and gusseted connection zone need to be considered. A separate study was conducted that investigated the yielding and buckling strength of gusset plates (Chapter 4). The stress distribution through a gusset plate is complex and difficult to predict because the cross-sectional area of gusset plate is not uniform, and each gusset plate design is unique in shape and size. This has motivated design methods that approximate yielding of gusset plates. Finite element modelling was used to study the development of yielding, buckling and plastic collapse behaviour of a brace end bolted to a series of corner gusset plates. In total 184 variations of gusset plate geometries were modelled in Abaqus®. The FEA modelling applied monotonic uniaxial load with an imperfection. Upon comparing results to current gusset plate design methods, it was found that the Whitmore width method for calculating the yield load of a gusset is generally un-conservative. To improve accuracy and safety in the design of gusset plates, modifications to current design methods for calculating the yield area and compressive strength for gusset plates is proposed. Bolted connections are a popular and common connection type used in BRBF design. Global out-of-plane stability tends to govern the design for this connection type with numerous studies highlighting the risk of instability initiated by inelasticity in the gussets, neck of the BRB end and/or restrainer ends. Subassemblage testing is the traditional method for evaluating global stability. However, physical testing of every BRBF variation is cost prohibitive. As such, Japan has developed an analytical approach to evaluate out-of-plane stability of BRBFs and incorporated this in their design codes. This analytical approach evaluates the different BRB components under possible collapse mechanisms by focusing on moment transfer between the restrainer and end of the BRB. The approach have led to strict criteria for BRBF design in Japan. Structural building design codes in New Zealand, Europe and the United States do not yet provide analytical methods to assess BRB and connection stability, with prototype/subassemblage testing still required as the primary means of accreditation. Therefore it is of interest to investigate the capability of this method to evaluate stability of BRBs designs and gusset plate designs used in New Zealand (including unstiffened gusset connection zones). Chapter 5 demonstrates the capability of FEA to study to the performance of a subassemblage test under cyclic loading – resembling that of a diagonal ground storey BRBF with bolted connections. A series of detailed models were developed using the strategy presented in Chapter 3. The geometric features of BRB 6.5a (Chapter 2) were used as a basis for the BRBs modelled. To capture the different failure mechanisms identified in Takeuchi et al. (2017), models varied the length that the cruciform (non-yielding) section inserts into the restrainer. Results indicate that gusset plates designed according to New Zealand’s Steel Structures Standard (NZS 3404) limit BRBF performance. Increasing the thickness of the gusset plates according to modifications discussed in Chapter 4, improved the overall performance for all variants (except when Lin/ Bcruc = 0.5). The effect of bi-directional loading was not found to notably affect out-of-plane stability. Results were compared against predictions made by the analytical method used in Japan (Takeuchi method). This method was found to be generally conservative is predicting out-of-plane stability of each BRBF model. Recommendations to improve the accuracy of Takeuchi’s method are also provided. The outcomes from this thesis should be helpful for BRB manufacturers, researchers, and in the development of further design guidance of BRBFs.

Research papers, Victoria University of Wellington

PurposeThe purpose of this research is to highlight the role of not-for-profit (NFP) organisations in enhancing disaster preparedness. The authors set out to understand their perspectives and practices in regard to disaster preparedness activities to support people who live precarious lives, especially those who live as single parents who are the least prepared for disasters.Design/methodology/approachThe research draws on in-depth, semi-structured interviews with 12 staff members, either in a group setting or individually, from seven NFP organisations, who were located in Ōtautahi (Christchurch) and Kaiapoi in Aotearoa New Zealand. These participants were interviewed eight years after the 2011 Christchurch earthquake.FindingsFour key narrative tropes or elements were drawn from across the interviews and were used to structure the research results. These included: “essential” support services for people living precarious lives; assisting people to be prepared; potential to support preparedness with the right materials and relationships; resourcing to supply emergency goods.Originality/valueThis research contributes to disaster risk reduction practices by advocating for ongoing resourcing of NFP groups due to their ability to build a sense of community and trust while working with precarious communities, such as single parents.