604 research outputs found

    Vulnerability assessment of the S. João de Loure Bridge: Vouga’s river

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    Steel bridges are particularly sensible to corrosion, which can put at risk the structural safety by affecting the joint elements. Having this in mind, the objective of this work was to evaluate the influence of the joint's stiffness in the structural response of the S. Jo√£o de Loure steel bridge. An improved model was developed for the bridge on the structural analysis software SAP2000. Maximum deflection, axial forces and corresponding stresses, and natural frequencies, were analyzed. Numerical results allow concluding about the influence of the joint's stiffness in the structural response of the bridge

    S. Jo√£o de Loure Bridge: vulnerability assessment and study of a common strengthening solution

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    This paper presents a structural vulnerability assessment of the steel bridge S. João de Loure. A structural model of the bridge was created and the influence of the joint’s stiffness on its structural response was evaluated using the structural analysis software SAP2000. Natural frequencies, axial forces and corresponding stress, and maximum mid-span deflection, were analyzed. A common strengthening solution with prestressing cables was studied intending to reduce the bridge’s mid-span deflection

    Mechanical characterization of adobe bricks in existing constructions in Aveiro Region, Portugal

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    In Portugal it is common to find earth constructions all over the country, being predominant in the centre and south. In the past, earth was massified as a construction material, used with different typologies and applications. Adobe construction is confined mainly to the central part of the country and more viewed in the west coast (gandaresa region). Aveiro, an Atlantic sea line city is an excellent example of a place with several ancient adobe constructions, some with architectural and historical relevance like some art-noveau houses. Just a few ones have been preserved with the passing years. The majority are in the threshold of ruin and structurally weak needing an urgent solution for their furtherance as buildings. Preservation and rehabilitation of those constructions was simply forgotten, carrying to the actual situation. In this context, becomes urgent, and absolutely necessary, to advance with rehabilitation and strengthening of these constructions. A great difficulty for technicians working on the rehabilitation relies on the lack of knowledge on adobe’s mechanical behaviour. In fact, in order to properly describe the structural behaviour of those constructions, there’s a need to investigate the mechanical properties of adobe. Hence, this paper presents a study which intended to characterise the behaviour of adobe brick units. Specimens were prepared from selected representative Aveiro’s constructions. The prepared specimens were tested in order to evaluate their mechanical behaviour in compression and tension. Usually, adobe blocks were made from clay soils. A basic characterization was also performed by the adobes’ granulometric analysis

    Numerical model to account for the influence of infill masonry on the RC structures behaviour

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    It is a common misconception considers that masonry infill walls in structural RC buildings can only increase the overall lateral load capacity, and, therefore, must always be considered beneficial to seismic performance. Recent earthquakes have showed numerous examples of severe damages or collapses of buildings caused by structural response modification induced by the non-structural masonry partitions. From a state-of-the-art review of the available numerical models for the representation of the infill masonry behaviour in structural response, it was proposed an upgraded model. The proposed model is inspired on the equivalent bi-diagonal compression strut model, and considers the non-linear behaviour of the infill masonry subjected to cyclic loads. The model was implemented and calibrated in a non-linear dynamic computer code, VISUALANL. In this paper, it is presented the proposed model and the results of the calibration analyses are briefly introduced and discussed

    Vibration control of single floor seismically excited structure using active mass damper

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    The purpose of this paper is to dampen the vibrations using active mass damper (AMD) flexible structure has been tested using Shake Table by linear cart. The active and passive mass properties has been discussed. An observer based state-feedback card controller was used for one floor AMD using MATLAB/SIMULINK modelling. Several laboratory experimental setup using AMD, general system description, model, parameters, and comparison of data obtained by Pakistan earthquake occurred on Oct 8, 2005 has been discussed

    Structural optimisation problem in support to building retrofitting decision

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    Various analysis methods, either linear elastic or non-linear, static or dynamic, are available for the performance analysis of existing buildings. Despite its advantages, it must be admitted that non-linear time history analysis can frequently become overly complex and impractical for general use as a first assessment. Simplified models, as the Capacity Spectrum Method, are frequently not able to accurately assess irregular structures. Considering these limitations, it is proposed and evaluated a simplified MDOF non-linear dynamic model, accounting for non-linear storey behaviour and storey damping. Based on the MDOF non-linear dynamic model, were developed optimization algorithms for the redesign of existing non-seismically designed structures. The optimization procedure searches for the optimum storey strengthening distribution (strength, stiffness or damping) in order to meet specific performance requirements, in terms of maximum inter-storey drift for a given seismic demand level. Numerical examples are presented in order to illustrate the capability of methodology

    A geometrical non-linear model for cable systems analysis

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    Cable structures are commonly studied with simplified analytical equations. The evaluation of the accuracy of these equations, in terms of equilibrium geometry configuration and stress distribution was performed for standard cables examples. A three-dimensional finite element analysis (hereafter FEA) procedure based on geometry-dependent stiffness coefficients was developed. The FEA follows a classical procedure in finite element programs, which uses an iterative algorithm, in terms of displacements. The theory is based on a total Lagrange formulation using Green-Lagrange strain. Pure Newton-Raphson procedure was employed to solve the non-linear equations. The results show that the rigid character of the catenary’s analytical equation, introduce errors when compared with the FEA

    Development of an open-source platform for calculating losses from earthquakes

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    Risk analysis has a critical role in the reduction of casualties and damages due to earthquakes. Recognition of this relation has led to a rapid rise in demand for accurate, reliable and flexible risk assessment numerical tools and software. As a response to this need, the Global Earthquake Model (GEM) started the development of an open source platform called OpenQuake, for calculating seismic hazard and risk at different scales. Along with this framework, also several other tools to support users creating their own models and visualizing their results are currently being developed, and will be made available as a Modelers Tool Kit (MTK). In this paper, a description of the architecture of OpenQuake is provided, highlighting the current data model, workflow of the calculators and the main challenges raised when running this type of calculations in a global scale. In addition, a case study is presented using the Marmara Region (Turkey) for the calculations, in which the losses for a single event are estimated, as well as probabilistic risk for a 50 years time span

    Mechanical characterization of timber in structural sizes: bending and compression tests

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    This paper presents the results obtained in a series of tests on Pinus Pinaster Ait. timber specimens, using the prEN408:2000, to estimate the local and global Young’s modulus and strength both in bending and compression parallel to the grain. The results obtained are compared with the values presented in the Portuguese Nationally Determined Parameters of Eurocode 5, for the quality classes assign by Portuguese Standard NP4305:1994 by visual grading

    Vulnerability assessment and strengthening of R.C. buildings non-seismically designed

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    The seismic vulnerability associated with existing buildings, constructed until the late 1970‚Äôs, in urban areas in most southern European countries, with moderate to high seismic risk, is of extreme importance. In that period, reinforced concrete buildings were designed and constructed without considering earthquake provisions, constituting a significant risk. Recent major earthquakes around the world have evidenced that this type of existing buildings lacking appropriate seismic resisting characteristics are very vulnerable. Their retrofit should be made in order to reduce vulnerability, and consequent risk, to currently accepted levels. Despite the evident advantages of a refined non-linear dynamic structural fibre modelling, it must be admitted that this approach can frequently become elaborated and costly. Simplified non-linear static models considering just one DOF (such the Capacity Spectrum Method) are frequently not able to assess accurately irregular structural systems. These facts sustain the development of less complicated structural models without debasing the essential features of dynamic response. It is demonstrated a recently proposed simplified methodology for nonlinear dynamic analysis of buildings based on the multi-modal spectral seismic response, and an optimisation tool for the strengthening design of existing buildings.Seismick√° zranitelnost existuj√≠c√≠ch budov postaven√Ĺch do roku 1970 v mńõstsk√Ĺch oblastech vńõtŇ°iny jihoevropsk√Ĺch zem√≠, s m√≠rn√Ĺmi aŇĺ vysok√Ĺmi seismick√Ĺmi riziky, je krajnńõ dŇĮleŇĺit√°. V t√© dobńõ se Ňĺelezobetonov√© budovy navrhovaly a stavńõly bez ohledu na zemńõtŇôesen√≠ a pŇôedstavuj√≠ tak v√Ĺznamn√© riziko. Ned√°vn√° velk√° zemńõtŇôesen√≠ po cel√©m svńõtńõ dok√°zala, Ňĺe existuj√≠c√≠ budovy tohoto typu, kter√© nemaj√≠ vhodnou odolnost proti zemńõtŇôesen√≠, jsou velmi zraniteln√©. Jejich modernizace m√° sn√≠Ňĺit jejich zranitelnost a z n√≠ plynouc√≠ riziko na dnes pŇôijatelnou √ļroveŇą. PŇôes zŇôejm√© v√Ĺhody propracovan√©ho neline√°rn√≠ho dynamick√©ho modelov√°n√≠ konstrukńćn√≠ho vl√°kna je nutno pŇôipustit, Ňĺe tato metoda mŇĮŇĺe b√Ĺt nńõkdy pracn√° a n√°kladn√°. ZjednoduŇ°en√© neline√°rn√≠ statick√© modely, kter√© berou v √ļvahu pr√°vńõ jednu DOF (jako je metoda kapacitn√≠ho spektra) nejsou ńćasto schopny pŇôesnńõ stanovit nepravideln√© konstrukńćn√≠ syst√©my. Tyto skuteńćnosti podporuj√≠ v√Ĺvoj m√©nńõ sloŇĺit√Ĺch struktur√°ln√≠ch modelŇĮ, aniŇĺ by sniŇĺovaly z√°kladn√≠ rysy dynamick√© odezvy. Demonstruje to ned√°vno navrŇĺen√° zjednoduŇ°en√° metoda neline√°rn√≠ dynamick√© anal√Ĺzy budov zaloŇĺen√° na multimod√°ln√≠ spektr√°ln√≠ seismick√© odezvńõ, a optimalizańćn√≠ n√°stroj pro navrhov√°n√≠ zes√≠len√≠ existuj√≠c√≠ch budov
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