https://repo.nzsee.org.nz/xmlui/handle/nzsee/2 2026-04-19T04:08:20Z https://repo.nzsee.org.nz/xmlui/handle/nzsee/2531 Challenges in post-earthquake recovery of damaged and neglected buildings in Christchurch CBD More than a decade since the 22 February 2011 earthquake devastated Christchurch CBD, partially demolished and neglected buildings remain present in the post-earthquake landscape. Christchurch City Council has made significant progress in recent years to reduce the level of neglected buildings across the central parts of the city. To encourage remediation of these buildings, the Council initiated the Barrier Sites programme to keep track of central city sites. This paper documents the current inventory of derelict properties and investigates issues that are delaying progress on these sites. We explore regulatory levers that can be used to influence action on these buildings (e.g. provisions in the Building Act and council bylaws). We also investigate how the local market drivers influence the speed of regeneration. Our review identifies gaps in the regulatory powers to act on barrier sites. Taking action involves meeting difficult definitions and tests under legislation and/or taking court proceedings. Specific legislative tools are needed to provide Councils with the powers they need to ensure action is taken on barrier sites to progress the regeneration of the city after a disaster. We also find that the delays in removing the cordon and uncertainties of the public sector anchor projects contained in the Blueprint have led to the loss of private investment and forced central city developments compete with more affordable commercial and residential offerings outside the CBD. With the passing of the 10-year anniversary of the earthquakes, this project offers a timely reminder of the mammoth struggles that the city has overcome evident in the numerous modern and resilient buildings, yet a few ‘battle sites’ slow the much-needed regeneration towards a resilient city centre. https://repo.nzsee.org.nz/xmlui/handle/nzsee/2530 Seismic effects of bracing irregularity of light timber-framed buildings Most residential buildings in New Zealand are low-rise light timber-framed (LTF) buildings, constructed according to a prescriptive standard – NZS 3604:2011 Timber-framed buildings. NZS 3604:2011 tabulates the seismic demand and also specifies the test procedure for evaluating the seismic resistance of proprietary LTF walls, which are often plasterboard walls. Designers need to ensure the provided total seismic bracing capacity is at least equal to the total seismic bracing demand, provided that bracing arrangements satisfy the specified irregularity limits. The irregularity limits of bracing arrangements in NZS3604:2011 were established based on engineering rules of thumb rather than rigorous scientific evidence. Earthquake damage observed in the 2010/11 Canterbury earthquake sequence demonstrated that simple regular LTF houses performed well while irregular houses often had significant damage that was uneconomical to repair. This suggested that the irregularity of LTF buildings was an important factor responsible for the exacerbated earthquake damage. To quantify seismic effects of permissible irregularities in NZS 3604:2011 and provide scientific evidence for elaborating irregularity limits in NZS 3604:2011, three single storey LTF buildings with varying degrees of permissible plan irregularities were designed and their seismic performance was studied by conducting three-dimensional non-linear push-over analyses. For the non-linear push-over analyses, the in-plane behaviour of LTF walls and ceiling diaphragms were modelled using the models, developed based on NZ practice, as reported in previous research. The study revealed that permissible irregular bracing arrangements in NZS 3604:2011 could amplify lateral deflections significantly, in comparison with the regular counterparts. As a result, irregular LTF buildings within the scope of NZS 3604:2011 could be susceptible to damage due to excessive deformations in earthquakes and this suggests that the irregularity limits in current NZS 3604:2011 be reviewed and tightened. https://repo.nzsee.org.nz/xmlui/handle/nzsee/2534 Review of recently constructed concrete wall-steel frame hybrid buildings Around New Zealand there has been an increasing trend of ‘hybrid’ multi-storey buildings that combine reinforced concrete walls with structural steel framing systems. This study aims to characterise and understand this type of building, focusing on buildings constructed in Auckland and Christchurch from 2014 onwards. Drawings from a total of 50 buildings were reviewed, and their structural features were documented, including building use, building height, lateral load resisting system, ductility, wall configuration, wall construction method, steel framing system and suspended floor system. Meetings with structural engineers were conducted to validate the review findings and to further understand design principles and decisions that lead to these outcomes. A typology comprising five building types with distinct lateral load-resisting systems was proposed based on the building review. Results showed regional differences between Auckland and Christchurch, owing to building use and seismic hazard in the respective cities. Auckland buildings surveyed tended to be residential buildings five storeys or higher made of precast walls connected with steel beams. Christchurch buildings, on the other hand, were primarily commercial buildings three to seven storeys high with dual frame-wall systems. Structural connections between steel frames and concrete walls were also documented, showing that bolted connections with headed stud embedment were most common. The results can be used to identify critical aspects of these mixed structural systems for further investigation and to develop archetype building designs that can be used for modelling and testing. https://repo.nzsee.org.nz/xmlui/handle/nzsee/2535 Interpretation and evaluation of NZS1170.5 2016 provisions for seismic ratcheting During seismic events, some structures have a tendency to ratchet and displace more in one direction than in the opposite direction after yielding, resulting in larger peak and residual displacements. Provisions to define the tendency for seismic ratcheting and the resulting displacement amplification are provided in the 2016 amendments of NZS1170.5. This paper presents some insight into the factors causing ratcheting, along with interpretation and evaluation of the proposed provisions. Firstly, the mechanics of seismic ratcheting due to dynamic stability, eccentric gravity loads, and unbalanced structural strengths in the back-and-forth directions are discussed. Afterwards, the new provisions were detailed and demonstrated by working through the NZS1170.5 commentary examples. The authors’ interpretation of the provisions is then presented, potential areas of confusion are identified, and wording changes to provide consistency and clarity are proposed. Finally, the displacement amplification factors provided in the 2016 amendments were evaluated using results of an independent study on single-degree-of-freedom reinforced concrete bridge columns subjected to eccentric gravity loading. It was found that the displacement amplification method proposed was reasonable, except when columns designed with a high ductility factor or which exhibit inelastic bilinear response had a significant tendency for ratcheting.