1,720,974 research outputs found
Damping considerations for rocking block dynamics using the discrete element method
Full text linkIt is well established that unreinforced masonry (URM) buildings develop damage-forming collapse mechanisms during high-intensity earthquakes, with these mechanisms exhibiting large rocking displacements before collapsing. The Discrete Element Method (DEM) of analysis can realistically capture phenomena that involve large movements of elements, resulting in the technique being ideal for simulating the collapse of URM building elements. Consequently, extensive research using DEM to analyse the seismic response of URM buildings and building components has recently been published. However, the variety of reported damping approaches that have apparently led to DEM results that successfully replicate physical observations underscores the need for consistent guidance related to the assignment of damping factors. The Rayleigh damping distribution model implemented in the DEM software 3DEC was used to study the differences between mass proportional (MP) and stiffness proportional (SP) damping configurations. After reviewing phenomena that need to be damped and previous works where damping was implemented, the capabilities and drawbacks of the time-efficient MP damping configuration were studied and the results compared to simulations with SP damping. When considering numerical simulations that incorporated MP damping and led to results that were seemingly well-matched to experimental tests, it was found that the apparent robustness of decisions pertaining to the adopted input parameters was deceptive in most cases. Consequently, SP damping was recommended for all DEM rocking simulations, even though MP damping could be used with satisfactory accuracy in certain situations discussed herein. A pragmatic relationship between both damping strategies was proposed
An inventory of unreinforced load-bearing stone masonry buildings in New Zealand
Full text linkAlmost all unreinforced stone masonry (URSM) buildings in New Zealand were constructed between 1860 and 1910, typically in regions where natural stone was sourced from local quarries, fields and rivers. These buildings form an important part of the country’s architectural heritage, but the performance of URSM buildings during earthquake induced shaking can differ widely due to many aspects related to the constituent construction materials and type of masonry wall cross-section morphology. Consequently, as a step towards gaining greater knowledge of the New Zealand URSM building stock and its features, an exercise was undertaken to identify and document the country-wide URSM building inventory. The compiled building inventory database includes: (i) general building information, such as address, building owner/tenant and building use; (ii) architectural configuration, such as approximate floor area, number of storeys, connection with other buildings, plan and elevation regularity; and (iii) masonry type, such as stone and mortar types, wall texture and wall cross-section morphology. From this exercise it is estimated that there is in excess of 668 URSM buildings currently in existence throughout New Zealand. A large number of these vintage URSM buildings require detailed seismic assessment and the implementation of seismic strengthening interventions in order to conserve and enhance this component of New Zealand’s cultural and national identity. The entire stock of identified buildings is reported in the appended annex (688 total), including 20 URSM buildings that were demolished following the Canterbury earthquake sequence
Performance of unreinforced stone masonry buildings during the 2010/2011 Canterbury earthquake swarm and retrofit technique for their seismic improvement
No full textPresents a post-earthquake assessment and building damage statistics for unreinforced stone masonry buildings in the city to document the performance of the structures. Gives details on typical building characteristics and on failure modes observed. Talks about damage mechanisms in stone masonry buildings and churches and retrofit interventions
Using DEM to Investigate Boundary Conditions for Rocking URM Facades Subjected to Earthquake Motion
Full text linkFaçade overturning is a frequently observed collapse mechanism occurring in unreinforced masonry (URM) buildings during high-intensity, earthquake-induced shaking. Following complete separation from a building, the rocking motion of a URM façade and the associated impact against the return walls are the factors that continue to contribute to the façade out-of-plane capacity. Seismic vulnerability studies of URM façades have historically neglected the interaction between building earthquake response and the rocking response of the façade, whereas in the study reported herein this interaction was analyzed using the discrete element modeling (DEM) approach, resulting in a façade out-of-plane capacity reduction. The increment in the dynamic rocking capacity caused by the frictional connection between the URM façade and the building was also analyzed and is reported
Statistical seismic vulnerability of New Zealand unreinforced masonry churches
No full textDuring the 2010–2011 Canterbury earthquake sequence, extensive damage occurred to NewZealand historical and architectural heritage, and particularly to unreinforced stone and clay brick masonrychurches. Of 309 unreinforced masonry churches identified nationwide, a sample of 80 buildings belonging tothe affected region was studied and their performance analysed statistically. Structural behaviour of religiousbuildings was described in terms of mechanisms affecting the so-called macro-elements, being portions of thebuilding behaving more or less independently. Discrete local damage levels were correlated with macroseis-mic shaking intensity through Damage Probability Matrices. Multiple-linear regressions were also considered,accounting for additional modifiers increasing/reducing the vulnerability of the macro-elements. Results showthe relevance of the proposed multiple-linear regression models for the national heritage of churches and theadvisability of extending mechanism-based regressions to other countries besides New Zealan
Unreinforced stone masonry buildings in New Zealand: Inventory and material characterisation
No full textThe high seismic vulnerability of unreinforced stone masonry (URM) buildings was once again demonstrated in the recent Canterbury earthquakes (2010-2011). The shortage of knowledge about New Zealand historic URM buildings, and about techniques for their conservation, led to numerous losses, both in terms of lives and architectural heritage. Almost all URM buildings in New Zealand were constructed between 1860 and 1910, typically in regions where natural stone (in particular basalt, schist and limestone) was sourced from local quarries, fields and rivers. There are estimated to be approximately 688 URM buildings in New Zealand, with most being a potential earthquake risk. As a first step, an inventory of the URM buildings of New Zealand was compiled, listing location, construction details and architectural configuration. A further development was the inspection of representative case study buildings, where architectural characteristics and extracted material samples were obtained. Compressive tests and petrographical analyses were undertaken on natural stone specimens, while compressive strength and mineralogical composition were determined for mortar samples. The aim of the study reported herein was to acquire a thorough understanding of the mechanical and physical properties of these URM buildings in order to assess seismic vulnerability factors and potential seismic improvement solutions
New Zealand contributions to the global earthquake model’s earthquake consequences database (GEMECD)
Full text linkThe Global Earthquake Model’s (GEM) Earthquake Consequences Database (GEMECD) aims to develop, for the first time, a standardised framework for collecting and collating geocoded consequence data induced by primary and secondary seismic hazards to different types of buildings, critical facilities, infrastructure and population, and relate this data to estimated ground motion intensity via the USGS ShakeMap Atlas. New Zealand is a partner of the GEMECD consortium and to-date has contributed with 7 events to the database, of which 4 are localised in the South Pacific area (Newcastle 1989; Luzon 1990; South of Java 2006 and Samoa Islands 2009) and 3 are NZ-specific events (Edgecumbe 1987; Darfield 2010 and Christchurch 2011). This contribution to GEMECD represented a unique opportunity for collating, comparing and reviewing existing damage datasets and harmonising them into a common, openly accessible and standardised database, from where the seismic performance of New Zealand buildings can be comparatively assessed. This paper firstly provides an overview of the GEMECD database structure, including taxonomies and guidelines to collect and report on earthquake-induced consequence data. Secondly, the paper presents a summary of the studies implemented for the 7 events, with particular focus on the Darfield (2010) and Christchurch (2011) earthquakes. Finally, examples of specific outcomes and potentials for NZ from using and processing GEMECD are presented, including: 1) the rationale for adopting the GEM taxonomy in NZ and any need for introducing NZ-specific attributes; 2) a complete overview of the building typological distribution in the Christchurch CBD prior to the Canterbury earthquakes and 3) some initial correlations between the level and extent of earthquake-induced physical damage to buildings, building safety/accessibility issues and the induced human casualtie
An inventory of unreinforced masonry churches in New Zealand
No full textChurches are an important part of New Zealand's historical and architectural heritage. Various earthquakes around the world have highlighted the significant seismic vulnerability of religious buildings, with the extensive damage that occurred to stone and clay-brick unreinforced masonry churches after the 2010-2011 Canterbury earthquakes emphasising the necessity to better understand this structural type. Consequently, a country-wide inventory of unreinforced masonry churches is here identified. After a bibliographic and archival investigation, and a 10 000 km field trip, it is estimated that currently 297 unreinforced masonry churches are present throughout New Zealand, excluding 12 churches demolished in Christchurch because of heavy damage sustained during the Canterbury earthquake sequence. The compiled database includes general information about the buildings, their architectural features and structural characteristics, and any architectural and structural transformations that have occurred in the past. Statistics about the occurrence of each feature are provided and preliminary interpretations of their role on seismic vulnerability are discussed. The list of identified churches is reported in annexes, supporting their identification and providing their address
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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