A photograph of Professor Derrick Moot inspecting a dug-out soil pit on a farm near River Road in Lincoln. There is a thick layer of saturated sand between the topsoil and the subsoil where the grass roots end.
A photograph of Professor Derrick Moot inspecting a dug-out soil pit on a farm near River Road in Lincoln. There is a thick layer of saturated sand between the topsoil and the subsoil where the grass roots end.
Cracking around the lamp post at the north end of Cranmer Square. In the background, crowds of people are standing around the square, where they evacuated to after the 22 February 2011 earthquake.
The Earthquake Recovery Minister, Gerry Brownlee, has made plain his frustration with the performance of the Christchurch City Council, calling the mayor, Bob Parker, a clown and saying that he's at the end of his tether.
A photograph of a balance weight on the side of the lower end of the main tube from the Townsend Telescope. The weight and tube were damaged during the 22 February 2011 earthquake.
A photograph of a balance weight on the side of the lower end of the main tube from the Townsend Telescope. The weight and tube were damaged during the 22 February 2011 earthquake.
A photograph of a fenced-off property at the end of Mitcham Place, Bexley. The house has been covered in temporary cladding and there are signs on the fence outlining hazards and dangers.
A photograph of the slow motion assembly on the lower end of the main tube from the Townsend Telescope. The tube was crushed and bent during the 22 February 2011 earthquake.
A view across the Worcester Street Bridge towards Cathedral Square. The Christ Church Cathedral can be seen at the end of the street with a metal brace applied to its front.
A view of the intersection of Hereford Street and Cambridge Terrace. The end gable of the Library Chambers has crumbled, and the area has been cordoned off with fencing and cones. In the background is the Christchurch City Council's Civic Offices.
A view across Cambridge Terrace to the former Canterbury Public Library. Masonry from the building's corners and end gable has fallen onto the footpath below. Wire fencing has been placed around the building as a cordon.
A crane sits beside the damaged Cranmer Courts building. The stone cladding of a gable end of the building has collapsed, exposing the wooden framework beneath. The photographer comments, "A bike ride around the CBD. Cranmer Courts, Montreal St".
As another year comes to an end, we present you with a selection of our favourite sites, discoveries and archaeology moments from 2014. It’s been a good year. We did a lot of digging…. …and recording. We found some cool … Continue reading →
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.
A residential property in Bexley with an overgrown garden. A spray-painted message on the wall of the house reads, "Thanks 4 the memories, 1997-2012, kia kaha". The photographer comments, "Today I took a drive around the residential area between Bexley and New Brighton. It was a stark reminder to be thankful for the situation we're in and perhaps not complain too much that our garden wall hasn't yet been rebuilt ... Saddest of all are the messages that have been scrawled on walls and garage doors by departing locals. At one end of the scale, thanking the family home for the memories, and at the other end of the scale cursing the looters which have made a bad situation that much more unbearable".
A photograph of contractor Tony Fisher of Fisher Agricultural Ltd. inspecting a dug-out soil pit on a farm near River Road in Lincoln. There is a thick layer of saturated sand between the topsoil and the subsoil where the grass roots end.
A photograph captioned by BeckerFraserPhotos, "Demolition of the Brannigans building. The container is being placed against the end of the building being demolished to protect the building below from falling debris".
Emergency Management personnel outside the Christchurch Art Gallery. The Art Gallery was used as the headquarters for Civil Defence after the 22 February 2011 earthquake. In the background, the east end of the Arts Centre can be seen.
A view across Cambridge Terrace to the former Canterbury Public Library. Masonry from the building's corners and end gable has fallen onto the footpath and the base of the building has been cordoned off with wire fencing.
A video of a press conference with GNS Scientist Kelvin Berryman. Berryman explains the recent aftershocks which have hit Christchurch. The end of the video shows the press conference being interrupted by an aftershock.
A photograph of an abandoned section at the end of Mitcham Place in Bexley, next to Sopley Lane. A pile of household rubbish and broken furniture has been left on the footpath in front of the property.
View down Victoria Street with the Casino on the right having some construction working being done, and the deconsruction of the Crowne Plaza Hotel at the end of the street. Flags in Canterbury colours, red and black can be seen on the street lights.
A view across Hereford Street to the former Canterbury Public Library. Masonry from the building's corners and end gable has fallen onto the footpath and wire fencing has been placed around the building as a cordon.
Damage to St John the Baptist Church in Latimer Square. Behind steel bracing, the gable end of the building has partly collapsed. The photographer comments, "The bracing did help hold the church up".
Parts of the facade of the Anglican Community of the Sacred Name building on Barbadoes Street ended on the street during the magnitude 7.1 earthquake in Christchurch on Saturday 4-9-2010.
Parts of the facade of the Anglican Community of the Sacred Name building on Barbadoes Street ended on the street during the magnitude 7.1 earthquake in Christchurch on Saturday 4-9-2010.
An aerial photograph of the Horseshoe Lake residential area. The photograph has been captioned by BeckerFraserPhotos, "Kingsford Street on the left and the end of Tasman Place on the right, Horseshoe Lake".
A photograph of lines drawn on the arm of Crack'd for Christchurch's armchair artwork.Crack'd for Christchurch comments, "The debate over opus goes on and we settle for flowing lines in the end."
Members of the public watching Lyttelton band, Runaround Sue, perform at Gap Filler's "Film in the Gap!" project in Beckenham. In the foreground is one end of a fence made of old metal bed heads and decorated with fairy lights.
Photograph captioned by Fairfax, "Maarten Schaap with his campervan which he and his family live in after their house was damaged in the quake, he lives at the end of the fault line where all the aftershocks are located".