105 results for Ingham, Jason, Journal article

  • Performance of posttensioned seismic retrofit of two stone masonry buildings during the Canterbury earthquakes

    Bailey, Sara; Dizhur, Dmytro; Trowsdale, J; Griffith, M; Ingham, Jason (2015-08)

    Journal article
    The University of Auckland Library

    Seismic retrofitting of unreinforced masonry buildings using posttensioning has been the topic of many recent experimental research projects. However, the performance of such retrofit designs in actual design level earthquakes has previously been poorly documented. In 1984 two stone masonry buildings within The Arts Centre of Christchurch received posttensioned seismic retrofits, which were subsequently subjected to design level seismic loads during the 2010/2011 Canterbury earthquake sequence. These 26 year old retrofits were part of a global scheme to strengthen and secure the historic building complex and were subject to considerable budgetary constraints. Given the limited resources available at the time of construction and the current degraded state of the steel posttension tendons, the posttensioned retrofits performed well in preventing major damage to the overall structure of the two buildings in the Canterbury earthquakes. When compared to other similar unretrofitted structures within The Arts Centre, it is demonstrated that the posttensioning significantly improved the in-plane and out-of-plane wall strength and the ability to limit residual wall displacements. The history of The Arts Centre buildings and the details of the Canterbury earthquakes is discussed, followed by examination of the performance of the posttension retrofits and the suitability of this technique for future retrofitting of other historic unreinforced masonry buildings.

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  • Earthquake-Damaged Unreinforced Masonry Building Tested In-Situ

    Dizhur, Dmytro; Derakhshan, H; Lumantarna, R; Ingham, Jason (2010-09)

    Journal article
    The University of Auckland Library

    In December 2007 a magnitude 6.8 earthquake had an epicentre located approximately 50 km from the city of Gisborne, New Zealand. This earthquake caused damage to a number of buildings in Gisborne, and in particular, to numerous unreinforced masonry buildings. One such building was damaged to the extent that significant post-earthquake repairs were necessary, and partial removal of two of the building’s gable ended walls was required. This reconstruction provided an opportunity for a team of researchers from the University of Auckland to conduct field tests on the building, allowing comparison with companion testing that had previously been undertaken in a laboratory setting. This field testing involved the extraction of clay brick and mortar samples, in-situ bed joint shear tests, diagonal shear tests on samples extracted from the gabled walls, an in-situ in-plane shear test and out-of-plane testing of a gable ended wall both in the as-built condition and after the installation of a near-surface mounted (NSM) carbon fibre reinforced polymer (CFRP) retrofit solution. Testing confirmed that the boundary conditions in real buildings can significantly affect experimental response, with vertical restraint resulting in a large increase in out-of-plane load capacity, and also confirmed that the near-surface mounted FRP solution is an excellent low invasive option for seismic strengthening of unreinforced masonry walls. Details of the history of the building, and the methods used to undertake the field testing are reported, and experimental results are presented.

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  • Finite element analysis of the PreWEC self-centering concrete wall system

    Henry, Richard; Sritharan, S; Ingham, Jason (2016-05-15)

    Journal article
    The University of Auckland Library

    A self-centering concrete wall system has been developed that consists of a Precast Wall with End Columns (PreWEC). A finite element model was developed to investigate the cyclic lateral-load response of the PreWEC system that included allowance for uplift at the wall-to-foundation interface, inclusion of the energy dissipating O-connectors, and inelastic behaviour of the confined concrete in the toe of the wall. The model showed good correlation with the results of a large-scale experimental test of the PreWEC system for both the global and local responses, closely matched the experimental lateral force–displacement response, unbonded tendon stress, neutral axis depth, concrete compressive strains, and connector deformation. Additional analyses were conducted to investigate modifications to the PreWEC design. These modified designs highlighted the influence of the inelastic behaviour of the wall toe and showed that in the PreWEC system the axial load on the wall panel is independent of the number of energy dissipating connectors. Lastly, analyses were conducted to investigate wall-to-floor interaction with the PreWEC system. It was shown that a rigid wall-to-floor connection would result in some damage to the floor diaphragms and an overstrength that should be considered when designing the wall for shear. Alternatively, connectors could be used with the PreWEC system to isolate the floor from the uplift of the wall and eliminate damage to the floor diaphragm.

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  • Structural Dynamic Response of an Unreinforced Masonry House using Non-Destructive Forced Vibration

    Karim, ARA; Sa'don, NM; Ingham, Jason (2016-01-02)

    Journal article
    The University of Auckland Library

    The results of non-destructive forced vibration tests on a small-scale unreinforced masonry house with a flexible timber diaphragm are presented. The primary purpose of this study was to investigate the dynamic responses between the as-built and retrofitted structures. This includes assessment of diaphragm response, wall-diaphragm connection details, in-plane wall response, out-of-plane wall response, and the response of wall corners. The test protocols were designed to investigate two types of retrofit techniques consisting of a plywood-retrofit on the diaphragm, and a connection-retrofit between the wall and diaphragm. From the results, one can see that the natural frequency and mode shapes of the first translational mode were affected. The force transfer mechanism of the as-built structure was significantly improved after applying both retrofits whereas each technique shows distinctive enhancements on the structure overall response.

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  • Panel connection details in existing New Zealand precast concrete buildings

    Seifi, Pouya; Henry, Richard; Ingham, Jason (2016-06)

    Journal article
    The University of Auckland Library

    Following the 2010/2011 Canterbury earthquakes the seismic design of buildings with precast concrete panels has received significant attention. Although this form of construction generally performed adequately in Christchurch, there were a considerable number of precast concrete panel connection failures. This observation prompted a review of more than 4700 panel details from 108 buildings to establish representative details used in both existing and new multi-storey and low rise industrial precast concrete buildings in three major New Zealand cities of Auckland, Wellington and Christchurch. Details were collected from precast manufacturers and city councils and were categorised according to type. The detailing and quantity of each reviewed connection type in the sampled data is reported, and advantages and potential deficiencies of each connection type are discussed. The results of this survey provide a better understanding of the relative prevalence of common detailing used in precast concrete panels and guidance for the design of future experimental studies.

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  • Construction Details and Observed Earthquake Performance of Unreinforced Clay Brick Masonry Cavity-walls

    Giaretton, M; Dizhur, Dmytro; da Porto, F; Ingham, Jason (2016-05)

    Journal article
    The University of Auckland Library

    Unreinforced masonry (URM) cavity-wall construction is a form of masonry where two leaves of clay brick masonry are separated by a continuous air cavity and are interconnected using some form of tie system. A brief historical introduction is followed by details of a survey undertaken to determine the prevalence of URM cavity-wall buildings in New Zealand. Following the 2010/2011 Canterbury earthquakes it was observed that URM cavity-walls generally suffered irreparable damage due to a lack of effective wall restraint and deficient cavity-tie connections, combined with weak mortar strength. It was found that the original cavity-ties were typically corroded due to moisture ingress, resulting in decreased lateral loadbearing capacity of the cavity-walls. Using photographic data pertaining to Christchurch URM buildings that were obtained during post-earthquake reconnaissance, 252 cavity-walls were identified and utilised to study typical construction details and seismic performance. The majority (72%, 182) of the observed damage to URM cavity-wall construction was a result of out-of-plane type wall failures. Three types of out-of-plane wall failure were recognised: (1) overturning response, (2) one-way bending, and (3) two-way bending. In-plane damage was less widely observed (28%) and commonly included diagonal shear cracking through mortar bed joints or bricks. The collected data was used to develop an overview of the most commonly-encountered construction details and to identify typical deficiencies in earthquake response that can be addressed via the selection and implementation of appropriate mitigation interventions.

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  • Residual strength assessment and destructive testing of decommissioned concrete bridge beams with corroded pretensioned reinforcement

    Rogers, Rhys; Wotherspoon, Liam; Scott, A; Ingham, Jason (2012)

    Journal article
    The University of Auckland Library

    Destructive tests were performed on 19 decommissioned pretensioned concrete bridge beams that had corroded pretensioned reinforcement. The beams were obtained from the 1969 Tiwai Point Bridge in Southland, New Zealand, which experienced chloride-induced corrosion caused by sea spray that resulted in the superstructure’s being decommissioned and removed in 2009. Destructive flexural testing results were compared with thorough nondestructive condition assessments and with post-test breakouts of reinforcement. The beams tested ranged from good-condition beams to those with severe corrosion in 4 of the 21 prestressed strands. The most severely corroded beam sustained 69% of the load of an equivalent good-condition beam. A proposed methodology for the assessment of the residual strength of beams with corroded pretensioned reinforcement was shown to provide an effective means of estimating the number of corroded strands that should be disregarded in the calculation of the residual strength.

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  • Predicting Seismic Retrofit Construction Cost for Buildings with Framed Structures Using Multi-Linear Regression Analysis

    Jafarzadeh, Reza; Wilkinson, Suzanne; Gonzalez, Vicente; Ingham, Jason; Amiri, G (2013-06-07)

    Journal article
    The University of Auckland Library

    Attempts to predict construction cost represent a problem of continual concern and interest to both practitioners and researchers. Such an attempt is presented here for the specific challenge of cost prediction when undertaking seismic retrofitting of existing structures. Using multilinear regression analysis, 14 independent variables were analyzed to develop parametric models for predicting the retrofit net construction cost (RNCC). Half of these variables have never previously been studied in the literature. The required data for this study were collected from 158 earthquake-prone public schools in Iran, each having a framed structure. The backward elimination (BE) regression technique was used to identify any variables that made a statistically significant contribution to the RNCC. The suitability of the BE technique for this identification was examined and demonstrated using a number of model-selection criteria. Rather surprisingly, building age and compliance with the earliest practiced seismic design code were found to be insignificant predictors of the RNCC. As reflected by the BE technique, the significant predictors were building total plan area, number of stories, structural type, seismicity, soil type, weight, and plan irregularity. The causal analysis performed between the RNCC and these variables showed that the first two variables have the greatest influence on the determination of the RNCC. The primary contribution to the construction industry is the introduction of a simple double-log cost-area model for predicting seismic retrofit construction cost. The introduced model enables engineering consultants, managers, and policy makers to simply predict this cost at the early planning and budgeting stage of seismic retrofit projects.

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  • Simplified indexes for the seismic assessment of masonry buildings: International database and validation

    Lourenço, PB; Oliveira, DV; Leite, JC; Ingham, Jason; Modena, C; da Porto, F (2013-12)

    Journal article
    The University of Auckland Library

    Heritage masonry buildings are particularly vulnerable to earthquakes because they are deteriorated and damaged, they were built with materials with low resistance, they are heavy and the connections between the various structural components are often insufficient. The present work details a simplified method of seismic assessment of large span masonry structures that was applied to a database of 44 monuments in Italy, Portugal and Spain, providing lower bound formulas for different simplified geometrical indexes. Subsequently, the proposed thresholds are validated with data from the 2010-2011 Canterbury earthquakes, which includes 48 stone and clay brick masonry churches. Finally, fragility curves that can be used to estimate the damage as a function of the peak ground acceleration (PGA) are also provided.

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  • Design Expression for the In-plane Shear Strength of Reinforced Concrete Masonry

    Voon, Kok; Ingham, Jason (2007)

    Journal article
    The University of Auckland Library

    Aspects relating to codification of the in-plane shear strength of concrete masonry walls when subjected to seismic loading are presented in this paper. Particular emphasis is placed on a model that is capable of representing the interaction between flexural ductility and masonry shear strength to account for the reduction in shear strength as ductility level increases. The simple method proposed here allows the strength enhancement provided by axial compression load to be separated from the masonry component of shear strength and is considered to result from strut action. In addition, minor modifications are made to facilitate adoption of the method in the updated version of the New Zealand masonry design standard, NZS 4230:2004. Prediction of shear strength from NZS 4230:2004 and alternative methods are compared with results from a wide range of masonry walls tests failing in shear. It was established that the shear equation in the former version of the New Zealand masonry standard (NZS 4230:1990) was overly conservative in its prediction of masonry shear strength. The current National Earthquake Hazards Reduction Program (NEHRP) shear expression was found to be commendable, but it does not address masonry shear strength within plastic hinge regions, therefore limiting its use when designing masonry structures in seismic regions. Finally, the new shear equation implemented in NZS 4230:2004 was found to provide significantly improved shear strength prediction with respect to its predecessor, with accuracy close to that resulted from NEHRP.

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  • Experimental in-plane strength investigation of reinforced concrete masonry walls with openings

    Voon, Kok; Ingham, Jason (2008)

    Journal article
    The University of Auckland Library

    This paper presents test results of eight partially grout-filled perforated concrete masonry walls that were subjected to cyclic lateral loading. Test results obtained from this research indicated that the size of openings and the length of trimming reinforcement significantly affected the lateral strength of perforated masonry walls. It was shown that the current New Zealand nonspecific masonry design standard NZS 4229 unsafely overpredicts the strength capacity of concrete masonry walls with small openings, and an amendment is proposed to rectify this matter. It was also shown that NZS 4229 is increasingly conservative as the height of openings increased. Diagonal cracking patterns that formed during testing were observed to align well with the load paths by which lateral shear force was assumed to be transferred to the foundation when using strut-and-tie analysis. This observation supports the use of the strut-and-tie technique as a viable tool to evaluate the flexural strength of walls of this type.

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  • Effects of interface material on the performance of free rocking blocks

    ElGawady, MA; Ma, Tsun Ming Quincy; Butterworth, John; Ingham, Jason (2010)

    Journal article
    The University of Auckland Library

    This paper presents the results of an experimental investigation on the rocking behavior of rigid blocks. Two types of test specimens have been tested, namely M and C types. Nine blocks of the M type and two blocks of the C type with different aspect ratios were tested with varying initial rotational amplitudes and with different materials at the contact interface, namely concrete, timber, steel, and rubber. The results showed that the interface material has significant influence on the free rocking performance of the blocks. Blocks tested on rubber had the fastest energy dissipation followed by concrete and timber bases, respectively. Analysis of the test results has shown that the energy dissipation in the case of tests on a rubber base is a continuous mechanism whereas in the case of tests on rigid bases, i.e. timber and concrete, energy dissipation is a discrete function. Finally, the rocking characteristics of the blocks were calculated using piecewise equations of motion and numerical analysis. It was possible to predict the correct free rocking amplitude response when a reliable value for the coefficient of restitution was used.

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  • Performance of unreinforced stone masonry buildings during the 2010/2011 Canterbury earthquake swarm and retrofit techniques for their seismic improvement

    Senaldi, I; Magenes, G; Ingham, Jason (2011-09)

    Journal article
    The University of Auckland Library

    The sequence of earthquakes that has greatly affected Christchurch and Canterbury since September 2010 has again demonstrated the need for seismic retrofit of heritage unreinforced masonry buildings. Commencing in April 2011, the damage to unreinforced stone masonry buildings in Christchurch was assessed and recorded with the primary objective being to document the seismic performance of these structures, recognising that they constitute an important component of New Zealand’s heritage architecture. A damage statistics database was compiled by combining the results of safety evaluation placarding and post-earthquake inspections, and it was determined that the damage observed was consistent with observations previously made on the seismic performance of stone masonry structures in large earthquakes. Details are also given on typical building characteristics and on failure modes observed. Suggestions on appropriate seismic retrofit and remediation techniques are presented, in relation also to strengthening interventions that are typical for similar unreinforced stone masonry structures in Europe.

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  • Experimental in-plane shear strength investigation of reinforced concrete masonry walls

    Voon, Kok; Ingham, Jason (2006)

    Journal article
    The University of Auckland Library

    This paper presents test results of ten single-story reinforced concrete masonry shear walls. Test results are summarized and compared with design formulae specified by the New Zealand masonry design standard NZS 4230:1990 and by the National Earthquake Hazards Reduction Program. It was determined that the test walls exhibited shear strength significantly exceeding the NZS 4230:1990 maximum permissible shear stress, confirming that NZS 4230:1990 was overly conservative in accounting for masonry shear strength. It was also confirmed from the test results that masonry shear strength increases with the magnitude of applied axial compressive stress and the amount of shear reinforcement, but that the shear strength decreases inversely in relation to an increase in wall aspect ratio. In addition, it was shown that the postcracking performance of shear dominated walls was substantially improved when uniformly distributing the shear reinforcement up the height of the walls.

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  • Concept and finite-element modeling of new steel shear connectors for self-centering wall systems

    Henry, Richard; Aaleti, S; Sritharan, S; Ingham, Jason (2010-02)

    Journal article
    The University of Auckland Library

    Self-centering precast concrete walls have been found to provide excellent seismic resistance. Such systems typically exhibit low energy dissipation, requiring supplementary dissipating components to improve their seismic performance. Mild steel shear connectors can provide an economical energy dissipating element. The design and analysis of steel shear connectors for a new precast wall system has been undertaken. A series of finite-element analyses were conducted to investigate the behavior of different types of connectors. Emerged from these analyses is a oval-shaped connector (O-connector) that provided satisfactory force-displacement behavior and appeared well suited for the new wall system in high seismic regions. An extensive experimental test program was then conducted to verify the performance of the chosen O-connector, which confirmed the expected response with sufficient energy dissipation. The experimental data demonstrated good correlation with the finite-element model developed, providing satisfactory confidence in the finite-element technique used for the development of the different connectors.

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  • Defining concrete compressive strain in unbonded post-tensioned walls

    Henry, Richard; Brooke, NJ; Sritharan, S; Ingham, Jason (2012)

    Journal article
    The University of Auckland Library

    The nominal flexural strength of a concrete member is determined when the strain at the extreme compression fiber reaches 0.003, which implies an accurate measurement or calculation of the concrete strains in the member’s critical region. The challenges associated with defining this strain using experimental and analytical means were demonstrated for precast concrete walls with unbonded post-tensioning. A series of laboratory tests was conducted to verify the critical compressive strains in post-tensioned (PT) precast concrete walls, which had no special confinement reinforcement in the wall toe. Test results confirmed the expected behavior of the wall panels and indicated that the onset of visible crushing in the wall toe may not occur until compressive strains develop that are significantly greater than 0.003. Despite employing several techniques, however, including displacement gauges, strain gauges, and photogrammetry, obtaining reliable and accurate experimental concrete strain measurements in the toe region of the wall proved challenging. To improve the understanding of the strain quantification at the nominal limit state, finite element analyses were conducted and the analysis results were compared with the experimental data. While some of the measured and analytically estimated strains provided comparable results in the critical wall toe region, a large spread in measured strains was observed and the average from several measurement devices was required for an accurate estimation of the nominal limit state. Overall, the three-dimensional (3-D) finite element model enabled an accurate and reliable estimation of the average concrete compressive strain. Based on this research, a strain of 0.005 is recommended for defining the nominal flexural strength of PT concrete walls.

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  • Retrofit techniques for seismic improvement of URM buildings

    Goodwin, C; Tonks, G; Ingham, Jason (2011)

    Journal article
    The University of Auckland Library

    As highlighted by the 2010 Darfield earthquake, many older buildings, particularly those constructed from unreinforced masonry (URM), now require seismic improvement in order to withstand earthquake forces. There are many approaches and techniques to seismic improvement, the most common of which are outlined below and analysed in terms of the impact of each on the heritage and architectural value of the building. This review is intended as a continuation of an earlier article (Goodwin et al. 2009) which gave background information to furnish designers with information prior to considering seismic retrofit. This information included a simple process for determining the basic heritage value of a building and some guidelines for good building conservation practice. A heritage building is more than simply a collection of building materials. As buildings age, they become more permanent parts of local culture. They become associated with notable people; with the memories of the public; and places where important historic events occurred. They become unique, as buildings are simply no longer made the same way, and time provides them with characteristics that could never be designed into a new building1. Old buildings can become ‘heritage’, where they become important to the public rather than just to the owner and occupants; a recent example of this is the birdcage hotel in Figure 1. There is no line on one side of which lies ‘heritage’, and on the other ‘not heritage’; all old buildings will have some heritage value. The difficulty is in determining the degree of heritage value, and what is important and what is less important about a building.

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  • Detecting Flushing of Thin-Sprayed Seal Pavements Using Pavement Management Data

    Kodippily, Sachi; Henning, Theunis; Ingham, Jason (2012-05)

    Journal article
    The University of Auckland Library

    Flushing is a pavement surface defect which affects the structural integrity of thin sprayed seal (chip seal) surfacings. Analysis was carried out on pavement performance data to determine the combination of factors that provide the best indication of flushing occurrence on in‐service pavements. Data were sourced from the Long‐Term Pavement Performance programme in New Zealand (NZ‐LTPP) as well as from field testing. The LTPP data were analysed in four categories; pavement composition characteristics, traffic‐related factors, climatic factors and effects of other pavement defects. Factor and correlation analyses were used to determine and investigate the factors that showed significant relationships to flushing. Surface thickness, surface age, surfacing type and rutting were found to have statistically significant correlations to flushing. Field testing provided data relating to the soil moisture environment under the pavement. The dry density and water content of soil were identified as having significant correlations to flushing. Regression analysis of the combination of these factors yielded a robust model to identify flushing.

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  • Innovative seismic design of a post-tensioned concrete masonry house

    Wight, Gavin; Ingham, Jason; Wilton, AR (2007)

    Journal article
    The University of Auckland Library

    Post-tensioned concrete masonry walls provide improved seismic performance, but have had limited application in seismic regions because of a lack of research pertaining to their in-plane response. Following focused research over recent years, a consortium of product suppliers has collaborated with the University of Auckland to construct New Zealand’s first post-tensioned concrete masonry house. A feature of this innovative design was that all incorporated products were commercially available, with no proprietary products being specifically developed for the prestressed masonry system used. Consequently, it is hoped that this house will be a showcase, and provide exposure for the technology in New Zealand and elsewhere. This paper provides a brief review of previous post-tensioned concrete masonry research applications, then discusses post-tensioning details and their application to house design and construction.

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  • Structural testing of enhanced post-tensioned concrete masonry walls

    Laursen, Peter; Ingham, Jason (2004)

    Journal article
    The University of Auckland Library

    The in-plane response of post-tensioned concrete masonry walls with unbonded tendons, incorporating strengthened masonry and enhanced energy dissipation, is examined by means of structural testing. An introduction to the testing program is followed b

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