• Wind and Structures
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• v.5 no.5
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• pp.407-422
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• 2002

Passive control of the flutter condition of suspension bridges using a combined vertical and torsional tuned mass damper (TMD) system is presented. The proposed TMD system has two degrees of freedom, which are tuned close to the frequencies corresponding to vertical and torsional symmetric modes of the bridge which get coupled during flutter. The bridge-TMD system is analyzed for finding critical wind speed for flutter using a finite element approach. Thomas Suspension Bridge is analyzed as an illustrative example. The effectiveness of the TMD system in increasing the critical flutter speed of the bridge is investigated through a parametric study. The results of the parametric study led to the optimization of some important parameters such as mass ratio, TMD damping ratio, tuning frequency, and number of TMD systems which provide maximum critical flutter wind speed of the suspension bridge.

• Structural Engineering and Mechanics
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• v.8 no.2
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• pp.119-136
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• 1999

The failure load of a continuous prestressed concrete beam depends partially on the amount of redistribution of moment that occurs prior to failure. Results from a parametric study, carried out using a nonlinear finite element computer program, are presented to demonstrate the influences of various factors on redistribution of moment in two-span, continuous bonded prestressed concrete beams. Trends in the data from the numerical studies are compared with those from a theoretical expression for percentage of redistribution, and it is shown that the redistribution of moment occurring in a continuous prestressed concrete beam is a function of number of parameters.

• Steel and Composite Structures
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• v.33 no.2
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• pp.181-194
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• 2019

This paper presents an efficient approach to generate a new empirical formula to predict the axial compression capacity (ACC) of circular concrete-filled tube (CCFT) columns using the artificial neural network (ANN). A total of 258 test results extracted from the literature were used to develop the ANN models. The ANN model having the highest correlation coefficient (R) and the lowest mean square error (MSE) was determined as the best model. Stability analysis, sensitivity analysis, and a parametric study were carried out to estimate the stability of the ANN model and to investigate the main contributing factors on the ACC of CCFT columns. Stability analysis revealed that the ANN model was more stable than several existing formulae. Whereas, the sensitivity analysis and parametric study showed that the outer diameter of the steel tube was the most sensitive parameter. Additionally, using the validated ANN model, a new empirical formula was derived for predicting the ACC of CCFT columns. Obviously, a higher accuracy of the proposed empirical formula was achieved compared to the existing formulae.

• Ocean Systems Engineering
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• v.12 no.1
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• pp.1-22
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• 2022

The majority of tubular joints commonly found in offshore jacket structures are multi-planar. Investigating the effect of loaded out-of-plane braces on the values of the stress concentration factor (SCF) in offshore tubular joints has been the objective of numerous research works. However, due to the diversity of joint types and loading conditions, a number of quite important cases still exist that have not been studied thoroughly. Among them are internally ring-stiffened two-planar TT-joints subjected to axial loading. In the present research, data extracted from the stress analysis of 243 finite element (FE) models, verified against available numerical and experimental data, was used to study the effects of geometrical parameters on the chord-side SCFs in two-planar tubular TT-joints reinforced with internal ring stiffeners subjected to two types of axial loading. Parametric FE study was followed by a set of nonlinear regression analyses to develop six new SCF parametric equations for the fatigue analysis and design of axially-loaded two-planar TT-joints reinforced with internal ring stiffeners.

• Communications for Statistical Applications and Methods
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• v.31 no.3
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• pp.323-336
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• 2024

The accurate forecasting of insurance claims is a critical component for insurers' risk management decisions. Hierarchical Bayesian parametric (BP) models can be used for health insurance claims forecasting, but they are unsatisfactory to describe the claims distribution. Therefore, Bayesian nonparametric (BNP) models can be a more suitable alternative to deal with the complex characteristics of the health insurance claims distribution, including heavy tails, skewness, and multimodality. In this study, we apply both a BP model and a BNP model to predict group health claims using simulated and real-world data for a private life insurer in Indonesia. The findings show that the BNP model outperforms the BP model in terms of claims prediction accuracy. Furthermore, our analysis highlights the flexibility and robustness of BNP models in handling diverse data structures in health insurance claims.

• Wind and Structures
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• v.38 no.4
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• pp.325-339
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• 2024

The longitudinal force resulting from tornado loads on transmission line is considered a crucial factor contributing to the failure of transmission line structures during tornado events. Accurate estimation of this longitudinal force poses a challenge for structural designers. Therefore, the objective of this paper is to provide a set of charts that can be easily used to estimate the peak longitudinal forces transferred from the conductors to a tower. The critical wind field and corresponding configuration considered in this paper are previously studied and determined. The charts should account for all the conductor parameters that can affect the value of the longitudinal force. In order to achieve that, a parametric study is first conducted to assess the variation of the longitudinal forces with different conductor parameters, based on the critical tornado configuration. Results of this parametric study are used to develop the charts that can be used to calculate longitudinal forces by adopting a multi-variable line regression. The forces calculated from charts are validated by finite element analysis. An example for the usage of the charts is provided at the end of this paper.

• Journal of Korean Society of Steel Construction
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• v.15 no.3
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• pp.231-239
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• 2003

Many box girder bridges have been constructed during the past several decades due to their large bending and torsional rigidities as well as aesthetic considerations. However, box girders have shortcoming in that the cross section distorts under an eccentric loading and warps out of the section plane. Therefore, in order to reduce distortional stresses such as distortional warping and transverse bending normal stresses, diaphragms were generally installed in the box girders. Shapes of the diaphragms in steel-box-girder bridges constructed up to date were solid-plate, frame, and truss types. The objectives of this study using parametric study were to evaluate the appropriate stiffness ratio of intermediate diaphragms and then to propose the effective spacing and numbers of intermediate diaphragms based on the evaluated stiffness ratio. Target bridges for this study were straight continuous span bridges with a single-cell steel box section. The parameters for the parametric study were the shape of box section, the span numbers, the equivalent span length, the stiffness of intermediate diaphragms, and the spacing of intermediate diaphragms. From the results of the parametric study, the effective spacing and numbers as well as the stiffness ratio of the intermediate diaphragms will be presented.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.161.1-161.1
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• 2005

• Structural Engineering and Mechanics
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• v.36 no.2
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• pp.243-246
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• 2010

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.06a
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• pp.1083-1084
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• 2009