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    Collapsed-RC Building Failure Mechanisms with a Forensic Engineering Approach
    (Asce-Amer Soc Civil Engineers, 2020) Etemadi, Ali; Balkaya, Can
    A reinforced concrete building in Konya, Turkey, collapsed suddenly on February 2, 2004, and 92 residents died. This case study was performed to determine the alternate load paths and failure mechanism of the building. The essence of a forensic engineering investigation of a construction failure is to determine the failure mechanisms by using the procedural causes and contributing factors. The building behavior under the sudden loss of ground-story columns and various scenarios of column removal was assessed. The site works and stepwise nonlinear analysis were applied to get the failure mechanism of the collapsed building. The lessons learned from this case study forensic investigation are discussed, and the construction and project errors beneath the collapse are identified. Torsion is not a desired first mode of dynamic behavior. The progressive collapse of the RC building was the torsional mode. In building due to architectural needs, i.e., lack of the beam in exterior frames, discontinuities in the three-dimensional (3D) structural framing and very low bonds existed in the RC beams, resulting in an improper redistribution of the forces. (c) 2020 American Society of Civil Engineers.
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    Direct displacement based design of RDC frame-shear wall structures
    (İstanbul Gelişim Üniversitesi Yayınları / Istanbul Gelisim University Press, 2021) Balkaya, Can; Etemadi, Ali; Genç, Öznur
    - A large part of Turkey's urban region is located in the seismic prone zone and in terms of population, the majority of densely populated cities are located close to near-fault regions. It is very important to determine the behaviors of structures again
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    Fatigue Assessment of Welded Connections in I-Girder Composite High-Speed Railway Bridges
    (Asce-Amer Soc Civil Engineers, 2021) Etemadi, Ali; Saglik, Huseyin
    The determination of the dynamic performance of a high-speed (HS) railway bridge is an ever-increasingly topical matter in public transportation networks owing to the broad establishment of ongoing HS railway transportation networks and the implementation of conventional networks for superior operational vehicle velocities. This paper examines the fatigue performance of a welded gusset plate connection of a composite steel I-girder railway bridge under trains moving within a certain range of velocities. The global three-dimensional finite element models (FEMs) are applied to examine the dynamic response of the I-girder composite steel-concrete railway bridge. The natural frequencies of the numerical model of bridge are verified using ambient vibration test results. A local three-dimensional FEM is generated in accordance with critical welded gusset plate connection using the ABAQUS platform. The local submodel is generated congruent with displacement field interpolation. The fatigue performance of a welded joint zone considering critical stress accumulation regions is determined by the hot-spot stress method under resonance conditions due to train passage with varying velocities. Stress cycles are extracted by taking real traffic spectra into account. Fatigue damage is calculated by using Palmgren-Miner's rule and the rain-flow counting method. The outcomes demonstrate that the bridge is not vulnerable to the forthcoming fatigue failure mode.
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    Nonlinear Integrated Design of Lattice Domes with Supporting Substructures
    (İstanbul Gelişim Üniversitesi Yayınları / Istanbul Gelisim University Press, 2017-08-26) Etemadi, Ali; Balkaya, Can
    This paper investigates the response interaction between reinforced concrete substructure and steel raised lattice roofing. The viewpoint of dynamic stability and nonlinear seismic behavior are considered as both geometrical and material nonlinearity. In particularly, dynamic stability performance of single layer Diamatic domes located on peripheral reinforced concrete columns is investigated under vertical loads and seismic excitation. Different supporting structures with rigidity and reinforcement detailing of the circular peripheral columns are considered in the integrated design. The vibration modes for the lattice dome with and without substructure effects are studied. Results show that high capacity substructure or fixed supporting assumption may lead to unsafe stability performance as well as uneconomical designs. The integrated design of composite system, RC supporting substructure and upper lattice roof could be provided superior dynamic stability performance when compared to the design without supporting substructure.
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    Shaping Effects on Long Span Bridge Deck Aerodynamics
    (İstanbul Gelişim Üniversitesi / Istanbul Gelisim University, 2023) Etemadi, Ali
    An aerodynamic circumstance of wind pressure surrounding the long-span bridge allocates many theoretical and experimental research to this topic. Determination of the materials and optimal cross-sectional shape of bridge decks that affected a dynamic behavior of long span bridge deck is still included in current research issues and works to be continued in this path. These include the Lack of sufficient awareness of wind forces, stemming from complex nature, and the unpredictability of the wind nature. In this study, in addition to recognizing the aerodynamic behavior of the flutter, the acting pressure forces on the bridge deck are investigated. The geometrical shape of decks, wind velocity, and flutter conditions are adopted as design variables that affected the dynamic forces exerted on bridge decks. A common type of geometric sections of the long-span bridge deck and effective aerodynamic phenomena are examined. The hollow box steel suspended deck and double cells box girder linked via upper flanges and cells linked via the top and bottom flanges are adopted for Computational Fluid Dynamic (CFD) approach. Thus, aerodynamic instability and turbulent torsional flutter flows, as well as a trail of shedding vortices around the bridge decks, are investigated. By changing some geometrical parameters of commonly used bridge sections, the optimal cross-section in terms of turbulence created above and below the deck section is examined and an optimal cross-sectional shape variable is proposed. The shape variable and section dimensions adopted for CFD-Simulations are similar to the dimensions and materials used in previous laboratory specimens of wind tunnels to be able to interpret the results and possibly verify them with the result of the current study.
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    Static Response of Functionally Graded Porous Circular Plates via Finite Element Method
    (Springer Heidelberg, 2024) Doori, Silda Ghazi Mohammed; Noori, Ahmad Reshad; Etemadi, Ali
    The main purpose of this paper is to investigate the axisymmetric bending response of functionally graded porous (FGP) circular plates. The material properties are changed continuously in the thickness direction of the plate. Three distinct porosity distributions uniform, symmetric and monolithic are employed. The effect of porosity on the axisymmetric bending analysis of circular plates is examined parametrically. In this study, clamped and roller supports which commonly serve to achieve ideal boundary conditions in numerous engineering applications are used. The finite element method is employed for numerical analysis. The principal of the potential energy is used to obtain the governing equations. To generate the model of the FGP circular plates, an eight-node quadratic quadrilateral element with two degrees of freedom on each node is utilized. The results of this study are confirmed by the existing published literature. A good agreement between the results of the presented model and the previous literature has been observed. The results of the present study show that plate deflection increases with the increase of the porosity coefficient and the ratio of radius to thickness of circular plates. By increasing the porosity coefficient, the displacement values of the plates made of uniform porosity distribution is effected more than those of other porosity distributions.