The Experts below are selected from a list of 11316 Experts worldwide ranked by ideXlab platform
Joao Negrao - One of the best experts on this subject based on the ideXlab platform.
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optimization of extradosed concrete bridges subjected to Seismic Action
Computers & Structures, 2021Co-Authors: Alberto M B Martins, Luis Simoes, Joao NegraoAbstract:Abstract An optimization algorithm is proposed to assist in the design of extradosed concrete bridges under static and Seismic loading. This procedure is composed of structural analysis, sensitivity analysis and optimization modules. The finite element method is used for the three-dimensional analysis considering static loading (dead load and road traffic live load), geometrical nonlinearities, time-dependent effects and Seismic Action by using a modal response spectrum analysis. The design is formulated as a multi-objective optimization problem with objectives of minimum cost, deflections and stresses including service and strength criteria. The solution of the minimax problem is obtained by minimizing a convex scalar function obtained through an entropy-based approach. The design variables are the extradosed cables and tendons forces, the extradosed cables and tendons cross-sectional areas, the deck, towers and piers sizes. The analytical discrete direct method is used to find the structural response to changes in the design variables. A convex optimization strategy with multiple starting points finds minimum cost solutions with an adequate stiffness and mass distribution that satisfy the design criteria under both, static loading and Seismic Action. Numerical examples concerning the optimization of a real-sized extradosed concrete bridge illustrate the features and capabilities of the proposed method.
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optimization of concrete cable stayed bridges under Seismic Action
Computers & Structures, 2019Co-Authors: Alberto M B Martins, Luis Simoes, Joao NegraoAbstract:Abstract A computational tool is presented for the optimum design of concrete cable-stayed bridges under Seismic Action. The finite element method is used for the three-dimensional analysis of the structure under dead and live loads, time-dependent effects and geometrical nonlinearities are considered. The dynamic analysis is solved by the modal/spectral approach. The design problem is posed as a multi-criteria optimization. The design variables are the cable forces and the cross-sectional dimensions of cables, deck and towers. Design objectives of minimum cost, deflections, natural frequencies and stresses considering both, serviceability and ultimate limit states are considered. Given that a gradient-based algorithm is applied for the optimization the discrete direct method is used for sensitivity analysis. An entropy-based algorithm finds economically and structurally efficient solutions by rearranging the stiffness and mass distribution to enhance the structural response. Numerical examples illustrate the features of the proposed computational tool.
Claudio Modena - One of the best experts on this subject based on the ideXlab platform.
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limit analysis of transverse Seismic capacity of multi span masonry arch bridges
Bulletin of Earthquake Engineering, 2015Co-Authors: Paolo Zampieri, Giovanni Tecchio, Francesca Da Porto, Claudio ModenaAbstract:Thousands of road and railway masonry arch bridges are still in service in the Italian and European transportation network, and many of them are located in highly Seismic areas. In this work, a kinematic analysis procedure is developed to assess the transverse Seismic capacity of multi-span masonry bridges with slender piers, as they may be vulnerable to transverse Seismic Action. The procedure can calculate the limit horizontal load multiplier of overall collapse mechanisms involving transverse deformation of deck and piers. The procedure is then adopted in a parametric study describing the typical ranges of the main parameters influencing bridge transverse capacity. Parametric analysis yielded a set of iso-acceleration envelope curves which supply the resistant Seismic acceleration of a bridge as a function of simple geometric parameters. The resulting graphs can thus be used for preliminary Seismic assessments.
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an integrated procedure for management of bridge networks in Seismic areas
Bulletin of Earthquake Engineering, 2013Co-Authors: Federico Carturan, Carlo Pellegrino, Riccardo Rossi, Massimiliano Gastaldi, Claudio ModenaAbstract:In this work an integrated procedure for the evaluation of the Seismic vulnerability of bridges included in the transportation network and a rational resource allocation for retrofitting with the aim of minimizing the consequences of an earthquake is shown at a network level. Both normal service and post-earthquake emergency conditions are considered as possible scenarios. The final result consists in global delay in the network versus Seismic Action occurring time. An iterative procedure finally defines the priority for optimal budget allocation for retrofitting. The procedure has been tested on a wide bridge network located in the North-eastern part of Italy.
Peter J Stafford - One of the best experts on this subject based on the ideXlab platform.
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structural behaviour and design criteria of under deck cable stayed bridges subjected to Seismic Action
Earthquake Engineering & Structural Dynamics, 2013Co-Authors: Alfredo Camara, Ana M Ruizteran, Peter J StaffordAbstract:SUMMARY: Under-deck cable-stayed bridges are very effective structural systems for which the strong contribution of the stay cables under live loading allows for the design of very slender decks for persistent and transient loading scenarios. Their behaviour when subjected to Seismic excitation is investigated herein and a set of design criteria are presented that relate to the type and arrangement of bearings, the number and configuration of struts, and the transverse distribution of stay cables. The nonlinear behaviour of these bridges when subject to both near-field and far-field accelerograms has been thoroughly investigated through the use of incremental dynamic analyses. An intensity measure that reflects the pertinent contributions to response when several vibration modes are activated was proposed and is shown to be effective for the analysis of this structural type. The under-deck cable-stay system contributes in a very positive manner to reducing the response when the bridges are subject to very strong Seismic excitation. For such scenarios, the reduction in the stiffness of the deck because of crack formation, when prestressed concrete decks are used, mobilises the cable system and enhances the overall performance of the system. Sets of natural accelerograms that are compliant with the prescriptions of Eurocode 8 were also applied to propose a set of design criteria for this bridge type in areas prone to earthquakes. Particular attention is given to outlining the optimal strategies for the deployment of bearings.
Panagiotis E Mergos - One of the best experts on this subject based on the ideXlab platform.
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optimum Seismic design of reinforced concrete frames according to eurocode 8 and fib model code 2010
Earthquake Engineering & Structural Dynamics, 2017Co-Authors: Panagiotis E MergosAbstract:Traditional Seismic design, like the one adopted in Eurocode 8 (EC8), is force-based and examining a single level of Seismic Action. In order to provide improved control of structural damage for different levels of Seismic Action, the new fib Model Code 2010 (MC2010) includes a fully fledged displacement-based and performance-based Seismic design methodology. However, the level of complexity and computational effort of the MC2010 methodology is significantly increased. Hence, the use of automated optimization techniques for obtaining cost-effective design solutions becomes appealing if not necessary. This study employs genetic algorithms to derive and compare optimum Seismic design solutions of reinforced concrete frames according to EC8 and MC2010. This is important because MC2010 is meant to serve as a basis for future Seismic design codes. It is found that MC2010 drives to more cost-effective solutions than EC8 for regions of low Seismicity and better or similar costs for regions of moderate Seismicity. For high-Seismicity regions, MC2010 may yield similar or increased structural costs. This depends strongly on the provisions adopted for selecting the set of ground motions. In all cases, MC2010 provides enhanced control of structural damage.
Fabio Biondini - One of the best experts on this subject based on the ideXlab platform.
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Diaphragm effectiveness of precast concrete structures with cladding panels under Seismic Action
Bulletin of Earthquake Engineering, 2019Co-Authors: Bruno Dal Lago, Silvia Bianchi, Fabio BiondiniAbstract:The Seismic performance of precast frame structures strongly depends on the mechanical devices connecting both structural and non-structural elements. Following recent post-earthquake field observations of unintended Seismic interAction of the cladding panels with the frame structure, the Seismic design of the cladded system is currently being critically examined by the scientific community. Design solutions involving a controlled cladding–structure interAction have been proposed to address this problem. However, the frame–panel interAction may draw high stresses into the roof diaphragm, as a consequence of the stiffening of the external frames only. This paper presents a parametric study based on linear and non-linear dynamic analyses investigating different levels of interAction among frames, panels, and diaphragm system. The results show how the deck and cladding connections influence the Seismic behaviour of the structure. Innovative fastening systems aimed at enhancing the Seismic performance of the structure are proposed based on the use of dissipative connection devices inserted into both cladding and deck components.
