1,721,012 research outputs found
Seismic analysis and risk mitigation of existing constructions
Get PDFFollowing a thorough and lengthy procedure, we would like to thank all contributors for their highest calibre papers,
which comprise the Special Issue on “Seismic analysis and risk mitigation of existing constructions” of the Open
Construction and Building Technology Journal.
The topic of the Special Issue encompasses a large number of issues spanning the design of special interventions for
the reduction of the effects of earthquakes on civil structures and infrastructures, to the structural identification and
assessment issues.
The field of seismic engineering is continuously looking for new strategies and methods, which empower the
designers and make them able to obtain more accurate response predictions. Researchers are involved in this process
and are called to successfully encounter new challenges emerging from the increasing need for the assessment of
existing constructions, especially when assuming strategic roles.
As is also reflected by the papers presented in the Special Issue, the continuous advances of the research in this field
moves across two basic directions. On the one hand, there is the direction of the robustness and the reliability of the
recent nonlinear seismic assessment methods (static, dynamic, incremental dynamic). Several approaches can be
followed to predict the response of structures to strong ground motions; however the results coming from each of them
are in some cases conflicting and not always amenable to easy interpretation.
On the other hand, the reliability of structural models still remains a major task of structural engineering and of
seismic engineering in particular. Mathematical models have to reproduce the physics of structures and its evolution
during complex damaging processes. Global and local models tend to reflect this by minimizing the loss of information.
In the Special Issue, we are proud to present state-of-the-art research findings described in detail in 9 papers
authored by 27 researchers of different universities in Italy, California (USA), Greece and United Kingdom. The papers
deal with the seismic analysis and risk mitigation aiming to address different purposes by proposing numerical,
analytical approaches and experimental tests
Modeling of infilled framed structures
No full text© Springer Science+Business Media Dordrecht 2013. This chapter presents an assessment of the behavior of infilled framed structures. The feasibility of possible immediate implementation of some recent developments both in analysis and design of infilled frames for practical design is investigated. It is now widely recognized that masonry infill panels, used in reinforced concrete (R/C) frame structures, significantly enhance both the stiffness and the strength of the surrounding frame. However, their contribution is often not taken into account because of the lack of knowledge of the composite behavior of the surrounding frame and the infill panel. Currently, Seismic Design Guidelines contain provisions for the calculation of the stiffness of solid infilled frames mainly by modeling infill walls as “diagonal struts.” However, such provisions are not provided for infilled frames with openings. The present study, based on available finite element results, proposes analytical equation for obtaining the reduction factor, which is the ratio of the effective width of a diagonal strut representing a wall with an opening over that of the solid RC infilled frame. The validity of the proposed equations is demonstrated by comparing our results, against work done by various researchers
A macro-modelling approach for the analysis of infilled frame structures considering the effects of openings and vertical loads
No full textDuring the last decades, several macro-models have been proposed for the modelling of the infill panels' contribution to the lateral strength of frames. Despite all this effort, a robust model, which takes into account the influence of the vertical load, is not yet available. Furthermore, the influence of the very common case of infill walls with openings, such as windows and doors, has been neglected in all the code provisions that have been published so far. In this paper, an updated macro-model, based on the equivalent pin-jointed diagonal compressive strut, is presented. The proposed macro-model is able to represent the stiffening effect of the infill panel with openings by taking into account both the size of the opening and the vertical load acting on the frame. Detailed and in-depth parametrical investigation, based on finite element analysis, shows that the proposed mathematical macro-model can be used as a reliable and useful tool for the determination of the equivalent compressive strut width since it accounts for a large number of parameters, which are not generally accounted for by the already available models in the literature
Modeling of surface roughness in electro-discharge machining using artificial neural networks
No full textElectro-Discharge machining (EDM) is a thermal process comprising a complex metal removal mechanism. This method works by forming of a plasma channel between the tool and the workpiece electrodes leading to the melting and evaporation of the material to be removed. EDM is considered especially suitable for machining complex contours with high accuracy, as well as for materials that are not amenable to conventional removal methods. However, several phenomena can arise and adversely affect the surface integrity of EDMed workpieces. These have to be taken into account and studied in order to optimize the process. Recently, artificial neural networks (ANN) have emerged as a novel modeling technique that can provide reliable results and readily, be integrated into several technological areas. In this paper, we use an ANN, namely, the multi-layer perceptron and the back propagation network (BPNN) to predict the mean surface roughness of electro-discharge machined surfaces. The comparison of the derived results with experimental findings demonstrates the promising potential of using back propagation neural networks (BPNNs) for getting a reliable and robust approximation of the Surface Roughness of Electro-discharge Machined Components
Krill herd algorithm-based neural network in structural seismic reliability evaluation
No full textIn this research work, the relative displacement of the stories has been determined by means of a feedforward Artificial Neural Network (ANN) model, which employs one of the novel methods for the optimization of the artificial neural network weights, namely the krill herd algorithm. For the purpose of this work, the area, elasticity, and load parameters were the input parameters and the relative displacement of the stories was the output parameter. To assess the precision of the feedforward (FF) model optimized using the Krill Herd Optimization (FF-KH) algorithm, comparison of results has been performed relative to the results obtained by the linear regression model, the Genetic Algorithm (GA), and the back propagation neural network model. The comparison of results has been carried out in the training and test phases. It has been revealed that the artificial neural network optimized with the krill herd algorithm supersedes the afore-mentioned models in potential, flexibility, and precision
Influence of column shear failure on pushover based assessment of masonry infilled reinforced concrete framed structures: A case study
No full textStructural frames, constructed either of steel or reinforced concrete (RC), are often infilled with masonry panels. However, during the analysis of the structural frames, it has become common practice to disregard the existence of infills because of the complexity in modeling. This omission should not be allowed because the two contributions (of infills and of frames) complement each other in providing a so different structural system. The use of different modeling assumptions significantly affects the capacity as well as the inelastic demand and safety assessment. In specific, the adoption of equivalent diagonal pin-jointed struts leaves open the problem of the evaluation of the additional shear on columns and consequently of the choice of a proper eccentricity for the diagonal struts. In this context, this paper presents the results of a real case study. The seismic performance of the RC structure of a school is evaluated by using concentric equivalent struts for modeling infills and the level of the additional shear on the columns is fixed as a rate of the axial force on them in agreement to a strong correlation obtained after a numerical experimentation. Hence, the applicability of the correlation mentioned before is shown and the form in which the results can be provided is presented. The characteristics of the new approach, first time applied to a real case, are highlighted by a comparison between the performance obtainable with different modeling detail levels of the infills. Through the paper, it is proved that the simplified evaluation of the additional shear demand produced by infills just for the base columns is sufficient to warn that a simplified model disregarding infills or based on the use of concentric struts for the infills may considerably overestimate the structural capacity. Further, by the study of a real case, the paper provides an overview of the models developed by the authors to obtain the capacity of reinforced concrete framed structure for the practical applications
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Numerical Modeling of Historic Masonry Structures
No full textThe majority of historical and heritage structures around the world consist of unreinforced masonry walls. A masonry structure is composed of masonry units, such as brick or marble blocks, with or without a joint filling material, such as mortar. A masonry with a joint material is usually made of two different materials (i.e. masonry units and mortar), representing a non-homogeneous and anisotropic structural component. In other words, masonry is a discontinuous structural component whose deformations and failure mechanism are governed by its blocky behavior. Some ancient masonry structures, such as ancient columns and colonnades, are constructed without any form of joint material between the individual blocks. Therefore, the isotropic elastic continuum-based models are not suitable for the simulation of the real nonlinear behavior of masonry walls under applied load
Definition of seismic vulnerability maps for civil protection systems: The case of lampedusa Island
Get PDFThe opportunity to locate and quantify the major criticalities associated to natural catastrophic events on a territory allows to plan adequate strategies and interventions by civil protection bodies involved in local and international emergencies. Seismic risk depends, most of all, on the vulnerability of buildings belonging to the urban areas. For this reason, the definition, by a deep analysis of the territory, of instruments identifying and locating vulnerability, largely favours the activities of institutions appointed to safeguard the safety of citizens. This paper proposes a procedure for the definition of vulnerability maps in terms of vulnerability indexes and critical peak ground accelerations for mid-small urban centres belonging to Mediterranean areas. The procedure, tested on the city centre of the Island of Lampedusa, is based on a preliminary historical investigation of the urban area and of the main formal and technological features of buildings involved. Moreover, the vulnerability of the constructions is evaluated by fast assessment methods (filling of evaluation forms). The vulnerability model, allowing the definition of the fragility curves, is calibrated on the basis of the results of an identification process of prototype buildings, selected to be adequately representative. Their characterizations have been provided using the results of an experimental dynamic investigation to develop high representative numerical model. Critical PGA values have been determined by pushover analyses. The results presented provided an unambiguous representation of the major criticalities with respect to seismic vulnerability and risk, of the city centre of the island, being a suitable tool for planning and handling of emergencies
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