Derivation of fragility curves for traditional timber-framed masonry buildings using nonlinear static analysis

Recent earthquakes and two experimental campaigns on timber-framed masonry walls have shown that timber-framed masonry buildings possess a good displacement capacity and hence can withstand severe earthquakes without collapse. In the present paper, timber-framed masonry panels with diagonal braces are studied. Using a simplified model based on non-linear (NL) lumped plasticity strut elements, NL analyses are carried out of typical traditional buildings in Lefkas (Greece) with diagonally braced timber-framed masonry walls in their lateral load resisting system. Furthermore, an investigation is carried out regarding the foundation of the buildings. The key feature of the Lefkas buildings is their dual structural system. The primary system consists of a stone masonry ground floor and all upper floors are made of timber-framed masonry walls. Timber posts in the ground floor, a few centimetres apart from the stone masonry, constitute the secondary structural system which is connected to the upper floors. This latter system is activated once the ground floor stone masonry piers fail. Two different structural models are developed to simulate each system. Pushover curves are derived from the NL analyses of the buildings and are then converted into capacity curves assuming the fundamental mode dominates. On these curves four damage states (slight damage, moderate damage, heavy damage and collapse) are defined on the basis of criteria related to the actual response of the building. The first three damage states are defined on the capacity curve of the primary system, whilst the ultimate damage state is related to the response of the secondary system. Then, fragility curves in terms of spectral displacement are generated, adopting a log-normal statistical distribution of the probability of damage

Fragility curves and loss estimation for traditional timber-framed masonry buildings in Lefkas, Greece

The 2003 earthquake in the Greek island of Lefkas, has revived the interest for the local anti-seismic technique based on the use of timber-framed masonry, whose adequate performance during the earthquake revealed the merits of this rather sophisticated, albeit traditional, construction. A key feature of the Lefkas structures is their dual structural system. The secondary system is activated once the ground storey stone masonry piers of the primary system (which includes timber-framed masonry in all storeys) fail. In this regard, two different structural models are presented herein to simulate the response of each system. A macro-model based on nonlinear (NL) strut elements and point plastic hinges is intended to model the timber-framed masonry. NL analyses are carried out for one, two and three storey buildings, which represent the most common cases in Lefkas. Furthermore, an investigation is carried out regarding the foundation of the buildings resting on soft alluvial deposits. Pushover curves are derived from the NL analyses of the buildings and are then converted to capacity curves using the characteristics of the predominant mode. On these curves four damage states (slight damage, moderate damage, heavy damage, and collapse) are defined on the basis of criteria related to the actual response of the building. Then, fragility curves in terms of spectral displacement are generated, adopting a log-normal statistical distribution. These curves are converted into PGA values using a selected response spectrum. Utilising these fragility curves a seismic loss scenario for the 2003 Lefkas earthquake is developed for the timber-framed masonry stock of Lefkas city

The Weyl tensor two-point function in de Sitter spacetime

We present an expression for the Weyl-Weyl two-point function in de Sitter spacetime, based on a recently calculated covariant graviton two-point function with one gauge parameter. We find that the Weyl-Weyl two-point function falls off with distance like r^{-4}, where r is spacelike coordinate separation between the two points.Comment: 9 pages, no figure

Towards efficient on-board deployment of DNNs on intelligent autonomous systems

With their unprecedented performance in major AI tasks, deep neural networks (DNNs) have emerged as a primary building block in modern autonomous systems. Intelligent systems such as drones, mobile robots and driverless cars largely base their perception, planning and application-specific tasks on DNN models. Nevertheless, due to the nature of these applications, such systems require on-board local processing in order to retain their autonomy and meet latency and throughput constraints. In this respect, the large computational and memory demands of DNN workloads pose a significant barrier on their deployment on the resource-and power-constrained compute platforms that are available on-board. This paper presents an overview of recent methods and hardware architectures that address the system-level challenges of modern DNN-enabled autonomous systems at both the algorithmic and hardware design level. Spanning from latency-driven approximate computing techniques to high-throughput mixed-precision cascaded classifiers, the presented set of works paves the way for the on-board deployment of sophisticated DNN models on robots and autonomous systems

A throughput-latency co-optimised cascade of convolutional neural network classifiers

Convolutional Neural Networks constitute a promi-nent AI model for classification tasks, serving a broad span ofdiverse application domains. To enable their efficient deploymentin real-world tasks, the inherent redundancy of CNNs is fre-quently exploited to eliminate unnecessary computational costs.Driven by the fact that not all inputs require the same amount ofcomputation to drive a confident prediction, multi-precision cas-cade classifiers have been recently introduced. FPGAs comprise apromising platform for the deployment of such input-dependentcomputation models, due to their enhanced customisation ca-pabilities. Current literature, however, is limited to throughput-optimised cascade implementations, employing large batching atthe expense of a substantial latency aggravation prohibiting theirdeployment on real-time scenarios. In this work, we introduce anovel methodology for throughput-latency co-optimised cascadedCNN classification, deployed on a custom FPGA architecturetailored to the target application and deployment platform,with respect to a set of user-specified requirements on accuracyand performance. Our experiments indicate that the proposedapproach achieves comparable throughput gains with relatedstate-of-the-art works, under substantially reduced overhead inlatency, enabling its deployment on latency-sensitive applications

Time-dependent prediction degradation assessment of neural-networks-based TEC forecasting models

An estimation of the difference in TEC prediction accuracy achieved when the prediction varies from 1 h to 7 days in advance is described using classical neural networks. Hourly-daily Faraday-rotation derived TEC measurements from Florence are used. It is shown that the prediction accuracy for the examined dataset, though degrading when time span increases, is always high. In fact, when a relative prediction error margin of +/-10% is considered, the population percentage included therein is almost always well above the 55%. It is found that the results are highly dependent on season and the dataset wealth, whereas they highly depend on the f(0)F2 - TEC variability difference and on hysteresis-like effect between these two ionospheric characteristics.info:eu-repo/semantics/publishedVersio

Simple and complex modelling of timber-framed masonry walls in Pombalino buildings

Timber-framed masonry has been developed as an effective lateral-load resisting system in regions of high seismicity such as Southern Europe. A salient feature of the ‘last generation’ of timber-framed (TF) buildings is the presence of diagonal members that may consist of two diagonal braces. The present study focusses on alternative modelling procedures, ranging from simple to rather complex, for this interesting type of traditional structure. All models are applied to study the behaviour of full-scale specimens of diagonally-braced TF panels. The complex model is based on plasticity with contact surfaces for the connection between timber diagonals and masonry infills. A parametric analysis using this model shows that masonry infills affect only slightly the lateral force carried by this TF panel configuration. Furthermore, two simple modelling techniques are put forward for application in the analysis of large, realistic structures incorporating TF walls. The first one is directly connected to the complex modelling and is based on substructuring. A nine-step procedure is developed and is found to properly reproduce the response of the test specimens. The second simple model is a phenomenological one, developed on the basis of observed behaviour during tests and is a complete hysteretic model; however, for comparison purposes, all models are evaluated here with respect to the prediction of the envelope (pushover) curve for the walls tested under lateral loads

The need for an online collection of traditional african food habits

Amongst the difficulties facing the indigenous people of Africa today is the deleterious shift from traditional food habits to the processed and packaged food products of western-owned corporations. This nutrition transition has been implicated in the rise of non-communicable diseases (NCDs) throughout Africa. The purpose of the present investigation was to determine whether there is a current need to document traditional African food habits via an online collection in an attempt to stimulate further research in this area and potentially improve the health status of indigenous Africans threatened by the nutrition transition. A systematic  search was performed to assess possible gaps in online collections focused on traditional African food habits. A questionnaire was administered to opinion leaders in the nutritional sciences at the 18th International Congress of Nutrition (ICN) in Durban, South Africa, September 2005, to determine the level of awareness of the importance of traditional African food habits within the context of the nutrition transition, and to determine the support among this cohort for an online collection of traditional African food habits. Our systematic review resulted in nine collections being identified. None of these collections were specifically  designed to raise  awareness of traditional African food habits however. Findings from the survey revealed that 86% of our cohort agreed that Africa is currently undergoing a  nutrition transition. Nearly 80% believed that knowledge of traditional African food habits is being lost. Indigenous African interviewees noted reduced consumption of sorghum and millet and an increased   consumption of wheat and rice within their region of origin. Approximately 82% believed that there was currently a gap in online collections focused on presenting information on traditional African food habits. Ninety-two percent of the cohort indicated their preparedness to make use of a novel, online collection of data on traditional African food habits. The findings revealed a critical need to collate and present data on traditional African food habits via a novel, online collection that could be used to stimulate education and research of food habits and their health implications, to provide a well-rounded forum in which such information is presented and shared.Key words: Africa, traditional foods, wild species, dietary practices, information networks and database

Seismic retrofitting and health monitoring of school buildings of Cyprus

The vulnerability of existing buildings to seismic forces and their retrofitting is an international problem. The majority of structures in seismic-prone areas worldwide are structures that have been designed either without the consideration of seismic forces, or with previous codes of practice specifying lower levels of seismic forces. In Cyprus, after the three earthquakes that occurred in 1995, 1996, and 1999, the Cyprus State, acting in a pioneering way internationally, has decided the seismic retrofitting of all school buildings, taking into account the sensitivity of the society towards these structures, which house the future generation of the society. In this paper the overall assessment methodology is presented, along with details of the over 10 year ongoing retrofitting program of the school buildings of Cyprus, with emphasis on the description of the program and the development of a wireless monitoring system. In addition, mathematical models of selected school buildings are presented and comparison is made with in-situ measurement