The Experts below are selected from a list of 804 Experts worldwide ranked by ideXlab platform
Yoko Okazaki - One of the best experts on this subject based on the ideXlab platform.
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Improvement of aerodynamic stability of suspension bridges with H-shaped simplified stiffening girder
Frontiers of Structural and Civil Engineering, 2016Co-Authors: Hiroshi Katsuchi, Hitoshi Yamada, Mayuko Nishio, Yoko OkazakiAbstract:Wind-tunnel study on the improvement of aerodynamic stability of simplified suspension-bridge girder structures was conducted with using a 1/40-scaled section model. Objective of the study is the development of an economically superior suspension bridge with 500–1,000 m center span length. The wind-tunnel test showed that an edge-girder type cross section exhibited large amplitude torsional vortex-induced vibration as well as torsional flutter at a low wind speed. Accordingly, aerodynamic countermeasures of open grating deck and triangular faring, and structural countermeasures of center stay, Diagonal Bracing and mass increase were tried to improve the aerodynamic stability. Finally, feasibility of the best combination to a full-scale bridge was examined by structural analysis.
Wojciech Siekierski - One of the best experts on this subject based on the ideXlab platform.
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An analytical method to estimate the natural bending frequency of the spans of railway through truss bridges with steel-and-concrete composite decks
Proceedings of the Institution of Mechanical Engineers Part F: Journal of Rail and Rapid Transit, 2016Co-Authors: Wojciech SiekierskiAbstract:The Eurocode 1 standard requires railway bridges to be checked against the hazard of resonance. To perform this task, the first natural bending frequency of a bridge span has to be computed. The analytical method based on the single-beam analogy is sufficiently accurate for simply supported beam-girder bridges. This paper proves the applicability of the method for through truss bridge spans with steel-and-concrete composite decks; this is despite the fact that the spans do not strictly comply with the assumptions of this method. The flexural stiffness of the bridge span is computed taking into account the joint action of the truss girders and the composite deck; the limited extent of span shear stiffness due to Diagonal Bracing is also considered. A uniform distribution of the span mass over the span length is assumed. The mass is computed based on geometrical characteristics of truss and deck members, taking into account gusset plates, stiffeners, connectors and fittings. The analytical method and finite...
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Equivalent moment of inertia of a truss bridge with steel-concrete composite deck
Structural Engineering and Mechanics, 2015Co-Authors: Wojciech SiekierskiAbstract:Flexural stiffness of bridge spans has become even more important parameter since Eurocode 1 introduced for railway bridges the serviceability limit state of resonance. For simply supported bridge spans it relies, in general, on accurate assessment of span moment of inertia that governs span flexural stiffness. The paper presents three methods of estimation of the equivalent moment of inertia for such spans: experimental, analytical and numerical. Test loading of the twin truss bridge spans and test results are presented. Recorded displacements and the method of least squares are used to find an "experimental" moment of inertia. Then it is computed according to the analytical method that accounts for joint action of truss girders and composite deck as well as limited span shear stiffness provided by Diagonal Bracing. Finally a 3D model of finite element method is created to assess the moment of inertia. Discussion of results is given. The comparative analysis proves efficiency of the analytical method.
Hiroshi Katsuchi - One of the best experts on this subject based on the ideXlab platform.
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Improvement of aerodynamic stability of suspension bridges with H-shaped simplified stiffening girder
Frontiers of Structural and Civil Engineering, 2016Co-Authors: Hiroshi Katsuchi, Hitoshi Yamada, Mayuko Nishio, Yoko OkazakiAbstract:Wind-tunnel study on the improvement of aerodynamic stability of simplified suspension-bridge girder structures was conducted with using a 1/40-scaled section model. Objective of the study is the development of an economically superior suspension bridge with 500–1,000 m center span length. The wind-tunnel test showed that an edge-girder type cross section exhibited large amplitude torsional vortex-induced vibration as well as torsional flutter at a low wind speed. Accordingly, aerodynamic countermeasures of open grating deck and triangular faring, and structural countermeasures of center stay, Diagonal Bracing and mass increase were tried to improve the aerodynamic stability. Finally, feasibility of the best combination to a full-scale bridge was examined by structural analysis.
Keyvan Ramin - One of the best experts on this subject based on the ideXlab platform.
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Finite Element Modeling and Nonlinear Analysis for Seismic Assessment of Off-Diagonal Steel Braced RC Frame
International Journal of Concrete Structures and Materials, 2015Co-Authors: Keyvan Ramin, Mitra FereidoonfarAbstract:The geometric nonlinearity of off-Diagonal Bracing system (ODBS) could be a complementary system to covering and extending the nonlinearity of reinforced concrete material. Finite element modeling is performed for flexural frame, x-braced frame and the ODBS braced frame system at the initial phase. Then the different models are investigated along various analyses. According to the experimental results of flexural and x-braced frame, the verification is done. Analytical assessments are performed in according to three dimensional finite element modeling. Nonlinear static analysis is considered to obtain performance level and seismic behaviour, and then the response modification factors calculated from each model’s pushover curve. In the next phase, the evaluation of cracks observed in the finite element models, especially for RC members of all three systems is performed. The finite element assessment is performed on engendered cracks in ODBS braced frame for various time steps. The nonlinear dynamic time history analysis accomplished in different stories models for three records of Elcentro, Naghan and Tabas earthquake accelerograms. Dynamic analysis is performed after scaling accelerogram on each type of flexural frame, x-braced frame and ODBS braced frame one by one. The base-point on RC frame is considered to investigate proportional displacement under each record. Hysteresis curves are assessed along continuing this study. The equivalent viscous damping for ODBS system is estimated in according to references. Results in each section show the ODBS system has an acceptable seismic behaviour and their conclusions have been converged when the ODBS system is utilized in reinforced concrete frame.
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Seismic Behavior of Steel Off-Diagonal Bracing System (ODBS) Utilized in Reinforced Concrete Frame
Journal of Structures, 2014Co-Authors: Keyvan RaminAbstract:The introduction of an eccentricity in this system results in a geometric nonlinearity behavior. The midpoint of the Diagonal member is connected to the corner joint using a brace member with a relatively low stiffness, thus forming a three-member Bracing system in each braced panel. An iterative method of analysis has been developed to study the nonlinear load-deflection behavior of ODBS. The results indicate that the load-deflection behavior of this system follows a nonlinear stiffness-hardening pattern with two yielding points, which reflect the tensile failure of different Bracings; the present study aims to investigate the efficiency of applying off-Diagonal steel braces to reinforced concrete frames. To achieve this, three types of 2-story, 6-story, and 15-story structures without and with X-Bracing and off-center Bracing systems were modeled using SAP2000 software, and for micromodeling ANSYS software was used to achieve finite element results for an exact comparison between various retrofitting systems. The results showed that the structures strengthened by toggle Bracing system revealed better behavior for low oscillation periods. Moreover, this type of Bracing system is quite suitable for 10-story structures but not for higher ones. Its main problem, which requires special contrivances to solve, is the existence of a soft ground floor.
Andre Filiatrault - One of the best experts on this subject based on the ideXlab platform.
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seismic response of concentrically braced steel frames made with rectangular hollow Bracing members
Journal of Structural Engineering-asce, 2003Co-Authors: Robert Tremblay, M H Archambault, Andre FiliatraultAbstract:This paper describes an experimental study on the seismic performance of concentrically braced steel frames made with cold-formed rectangular tubular Bracing members. A total of 24 quasistatic cyclic tests were performed on full size X Bracing and single Diagonal Bracing systems. Two loading sequences were considered: a symmetrical stepwise increasing deformation sequence and a displacement history obtained from nonlinear dynamic analyses of typical braced steel frames. All specimens buckled out-of the plane of the frame and the tests were interrupted when fracture of the braces occurred in the region of highest curvature. For X Bracing, the results clearly show that the effective length of the braces can be used to determine their compression strength and to characterize their hysteretic response, including energy dissipation capability. Simplified models are proposed to predict the out-of-plane deformation of the braces as a function of the ductility level. These models are then used to develop an empir...