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Research papers, The University of Auckland Library

Having a quick but reliable insight into the likelihood of damage to bridges immediately after an earthquake is an important concern especially in the earthquake prone countries such as New Zealand for ensuring emergency transportation network operations. A set of primary indicators necessary to perform damage likelihood assessment are ground motion parameters such as peak ground acceleration (PGA) at each bridge site. Organizations, such as GNS in New Zealand, record these parameters using distributed arrays of sensors. The challenge is that those sensors are not installed at, or close to, bridge sites and so bridge site specific data are not readily available. This study proposes a method to predict ground motion parameters for each bridge site based on remote seismic array recordings. Because of the existing abundant source of data related to two recent strong earthquakes that occurred in 2010 and 2011 and their aftershocks, the city of Christchurch is considered to develop and examine the method. Artificial neural networks have been considered for this research. Accelerations recorded by the GeoNet seismic array were considered to develop a functional relationship enabling the prediction of PGAs. http://www.nzsee.org.nz/db/2013/Posters.htm

Research papers, University of Canterbury Library

The Mw 6.2 February 22nd 2011 Christchurch earthquake (and others in the 2010-2011 Canterbury sequence) provided a unique opportunity to study the devastating effects of earthquakes first-hand and learn from them for future engineering applications. All major events in the Canterbury earthquake sequence caused widespread liquefaction throughout Christchurch’s eastern suburbs, particularly extensive and severe during the February 22nd event. Along large stretches of the Avon River banks (and to a lesser extent along the Heathcote) significant lateral spreading occurred, affecting bridges and the infrastructure they support. The first stage of this research involved conducting detailed field reconnaissance to document liquefaction and lateral spreading-induced damage to several case study bridges along the Avon River. The case study bridges cover a range of ages and construction types but all are reinforced concrete structures which have relatively short, stiff decks. These factors combined led to a characteristic deformation mechanism involving deck-pinning and abutment back-rotation with consequent damage to the abutment piles and slumping of the approaches. The second stage of the research involved using pseudo-static analysis, a simplified seismic modelling tool, to analyse two of the bridges. An advantage of pseudo-static analysis over more complicated modelling methods is that it uses conventional geotechnical data in its inputs, such as SPT blowcount and CPT cone resistance and local friction. Pseudo-static analysis can also be applied without excessive computational power or specialised knowledge, yet it has been shown to capture the basic mechanisms of pile behaviour. Single pile and whole bridge models were constructed for each bridge, and both cyclic and lateral spreading phases of loading were investigated. Parametric studies were carried out which varied the values of key parameters to identify their influence on pile response, and computed displacements and damages were compared with observations made in the field. It was shown that pseudo-static analysis was able to capture the characteristic damage mechanisms observed in the field, however the treatment of key parameters affecting pile response is of primary importance. Recommendations were made concerning the treatment of these governing parameters controlling pile response. In this way the future application of pseudo-static analysis as a tool for analysing and designing bridge pile foundations in liquefying and laterally spreading soils is enhanced.

Images, eqnz.chch.2010

Selective colour full size view from one of my previous shots. Edgeware Road, Christchurch. Damaged from the Christchurch Earthquake Twitter | Facebook |

Research papers, University of Canterbury Library

After a high-intensity seismic event, inspections of structural damages need to be carried out as soon as possible in order to optimize the emergency management, as well as improving the recovery time. In the current practice, damage inspections are performed by an experienced engineer, who physically inspect the structures. This way of doing not only requires a significant amount of time and high skilled human resources, but also raises the concern about the inspector’s safety. A promising alternative is represented using new technologies, such as drones and artificial intelligence, which can perform part of the damage classification task. In fact, drones can safely access high hazard components of the structures: for instance, bridge piers or abutments, and perform the reconnaissance by using highresolution cameras. Furthermore, images can be automatically processed by machine learning algorithms, and damages detected. In this paper, the possibility of applying such technologies for inspecting New Zealand bridges is explored. Firstly, a machine-learning model for damage detection by performing image analysis is presented. Specifically, the algorithm was trained to recognize cracks in concrete members. A sensitivity analysis was carried out to evaluate the algorithm accuracy by using database images. Depending on the confidence level desired,i.e. by allowing a manual classification where the alghortim confidence is below a specific tolerance, the accuracy was found reaching up to 84.7%. In the second part, the model is applied to detect the damage observed on the Anzac Bridge (GPS coordinates -43.500865, 172.701138) in Christchurch by performing a drone reconnaissance. Reults show that the accuracy of the damage detection was equal to 88% and 63% for cracking and spalling, respectively.

Images, UC QuakeStudies

A digitally manipulated photograph of the badly twisted Medway Street footbridge. The photographer comments, "This bridge over the Avon River in Christchurch, New Zealand has been left in place since the first major earthquake back in September 2010. Graffiti artists or taggers are still leaving their marks on it even though it is nearly twisted at 90 degrees at one point".

Images, UC QuakeStudies

The Williams Street Bridge in Kaiapoi. This part of the footpath was damaged when the concrete abutment rose during the earthquake, forcing its way through the pavement and into the open. Fencing has been placed around this section of the bridge until work can be done to make it safe to walk on.

Images, eqnz.chch.2010

One Month after the Christchurch Earthquake. The mangled remains of the pedestrian bridge over the river Avon Twitter | Facebook | My ...

Images, UC QuakeStudies

In front of the Williams Street Bridge in Kaiapoi. This part of the footpath was damaged when the concrete abutment rose during the earthquake, forcing its way through the pavement and into the open. Fencing has been placed around this section of the bridge until work can be done to make it safe to walk on.

Research papers, University of Canterbury Library

The paper presents preliminary findings from comprehensive research studies on the liquefaction-induced damage to buildings and infrastructure in Christchurch during the 2010-2011 Canterbury earthquakes. It identifies key factors and mechanisms of damage to road bridges, shallow foundations of CBD buildings and buried pipelines, and highlights the implications of the findings for the seismic analysis and design of these structures.

Images, UC QuakeStudies

A photograph looking west down Cashel Street towards the Bridge of Remembrance. Rubble from earthquake-damaged buildings is piled on the road in the distance. Wire fencing has been placed in front of a seating area to the left and around a building in the distance.

Images, UC QuakeStudies

A view down Cashel Street from the Bridge of Remembrance, showing earthquake damage to several buildings along Cashel Mall. In the background the Hotel Grand Chancellor can be seen, a Christchurch hotel that was badly damaged in the February 2011 earthquake. The collapse of a key supporting shear wall caused the building to visibly lean to one side.

Images, UC QuakeStudies

The damaged Snell Place footbridge. A crack is visible at the apex of the span. The photographer comments, "Before the Christchurch earthquakes this bridge used to be just just 9 feet at high tide above the River Avon. Now with the ends pushed together it has probably moved up another 9 feet".

Audio, Radio New Zealand

Residents of Christchurch's coastal suburbs around New Brighton are being promised they won't have to wait another decade for an urgently needed new bridge. The existing one is a critical emergency escape route but is almost 100 years old and suffered significant damage in the 2011 earthquake. And as Timothy Brown reports, plans for an upgrade are grinding slowly ahead.

Images, UC QuakeStudies

The badly twisted Medway Street footbridge. The photographer comments, "The September 4th 2010 earthquake in Christchurch was so violent that the banks of the Avon River moved towards each other. This footbridge being metal had to twist sideways to release the pressure of being pushed from both river banks. It looked like it had been wrung out like a wet towel".

Research papers, The University of Auckland Library

The region in and around Christchurch, encompassing Christchurch city and the Selwyn and Waimakariri districts, contains more than 800 road, rail, and pedestrian bridges. Most of these bridges are reinforced concrete, symmetric, and have small to moderate spans (15–25 m). The 22 February 2011 moment magnitude (Mw) 6.2 Christchurch earthquake induced high levels of localized ground shaking (Bradley and Cubrinovski 2011, page 853 of this issue; Guidotti et al. 2011, page 767 of this issue; Smyrou et al. 2011, page 882 of this issue), with damage to bridges mainly confined to the central and eastern parts of Christchurch. Liquefaction was evident over much of this part of the city, with lateral spreading affecting bridges spanning both the Avon and Heathcote rivers.

Research papers, The University of Auckland Library

Quick and reliable assessment of the condition of bridges in a transportation network after an earthquake can greatly assist immediate post-disaster response and long-term recovery. However, experience shows that available resources, such as qualified inspectors and engineers, will typically be stretched for such tasks. Structural health monitoring (SHM) systems can therefore make a real difference in this context. SHM, however, needs to be deployed in a strategic manner and integrated into the overall disaster response plans and actions to maximize its benefits. This study presents, in its first part, a framework of how this can be achieved. Since it will not be feasible, or indeed necessary, to use SHM on every bridge, it is necessary to prioritize bridges within individual networks for SHM deployment. A methodology for such prioritization based on structural and geotechnical seismic risks affecting bridges and their importance within a network is proposed in the second part. An example using the methodology application to selected bridges in the medium-sized transportation network of Wellington, New Zealand is provided. The third part of the paper is concerned with using monitoring data for quick assessment of bridge condition and damage after an earthquake. Depending on the bridge risk profile, it is envisaged that data will be obtained from either local or national seismic monitoring arrays or SHM systems installed on bridges. A method using artificial neural networks is proposed for using data from a seismic array to infer key ground motion parameters at an arbitrary bridges site. The methodology is applied to seismic data collected in Christchurch, New Zealand. Finally, how such ground motion parameters can be used in bridge damage and condition assessment is outlined. AM - Accepted manuscript

Images, UC QuakeStudies

A damaged wooden footbridge across the Avon River beside University Drive is blocked off with sheets of plywood and danger signs. The photographer comments, "The University restarts its teaching, and the techies in e-learning move out of NZi3. The bridge to the Rec Centre".

Images, UC QuakeStudies

Damage to River Road in Richmond. The road surface is badly cracked and slumped, and liquefaction silt covers part of the road. Two people in gumboots walk towards a barrier erected across the road using road cones and warning tape, and in the background the badly twisted Medway Street bridge can be seen. The photographer comments, "Longitudinal cracks indicate lateral movement as the land sagged towards the river. Near 373 River Rd, looking south-east towards Medway St. The Medway St bridge is visible in the background".

Images, UC QuakeStudies

A sewage pumping station on Avonside Drive has been lifted out of the ground by liquefaction. In the background, the damaged Snell Place footbridge over the Avon River is closed off with cordon fencing. The photographer comments, "A Sunday afternoon ride to New Brighton, then back via Aranui, Wainoni, Dallington, and Richmond. Not a cheerful experience. Dallington footbridge. The two pieces of this foot bridge have moved towards each other, so the bridge has developed quite a peak. The sewage pumping station has been heaved out of the ground by hydraulic pressure during quakes".