• Steel and Composite Structures
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• v.20 no.6
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• pp.1193-1203
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• 2016

This paper focuses on the analytical behavior of modular circular concrete-filled tubular (CFT) column with enhanced bracing details. To design a full-scale bridge pier of multiple circular concrete-filled tubes, numerical analysis was used to evaluate structural performance according to load directivity. In previous research (Ma et al. 2012, Shim et al. 2014), low cycle fatigue failure at bracing joints was observed, so enhanced bracing details to prevent premature failure are proposed in this analysis. The main purpose of this research is to investigate seismic performance for the diagonal direction load without premature failure at the joints when the structure reaches the ultimate load. The ABAQUS finite-element software is used to evaluate experimental performance. A quasi-static loading condition on a modular bridge pier is introduced to investigate structural performance. The results obtained from the analysis are evaluated by comparing with load-displacement responses from experiments. The concrete-filled tubes with enhanced bracing details showed higher energy dissipation capacity and proper performance without connection failure for a diagonal load.

• Earthquakes and Structures
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• v.9 no.3
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• pp.603-623
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• 2015

The scale and nature of the recent earthquakes in the world and the related earthquake disaster index coerce the concerned community to become anxious about it. Therefore, it is crucial that seismic lateral load effect will be appropriately considered in structural design. Application of seismic isolation system stands as a consistent alternative against this hazard. The objective of the study is to evaluate the structural and economic feasibility of reinforced concrete (RC) buildings with base isolation located in medium risk seismic region. Linear and nonlinear dynamic analyses as well as linear static analysis under site-specific bi-directional seismic excitation have been carried out for both fixed based (FB) and base isolated (BI) buildings in the present study. The superstructure and base of buildings are modeled in a 3D finite element model by consistent mass approach having six degrees of freedom at each node. The floor slabs are simulated as rigid diaphragms. Lead rubber bearing (LRB) and High damping rubber bearing (HDRB) are used as isolation device. Change of structural behaviors and savings in construction costing are evaluated. The study shows that for low to medium rise buildings, isolators can reduce muscular amount of base shears, base moments and floor accelerations for building at soft to medium stiff soil. Allowable higher horizontal displacement induces structural flexibility. Though incorporating isolator increases the outlay, overall structural cost may be reduced. The application of base isolation system confirms a potential to be used as a viable solution in economic building design.

• The KSFM Journal of Fluid Machinery
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• v.15 no.6
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• pp.11-17
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• 2012

The one way fluid structure interaction analysis on advanced propeller blade for next generation turboprop aircraft. HS1 airfoil series are selected as a advanced propeller blade airfoil. Adkins method is used for aerodynamic design and performance analysis with respect to the design point. Adkins method is based on the vortex-blade element theory which design the propeller to satisfy the condition for minimum energy loss. propeller geometry is generated by varying chord length and pitch angle at design point. Blade sweep is designed based on the design mach number and target propulsion efficiency. The aerodynamic characteristics of the designed Advanced propeller were verified by CFD(Computational Fluid Dynamic) and showed the enhanced performance than the conventional propeller. The skin-foam sandwich structural type is adopted for blade. The high stiffness, strength carbon/epoxy composite material is used for the skin and PMI(Polymethacrylimide) is used for the foam. Aerodynamic load is calculated by computational fluid dynamics. Linear static stress analysis is performed by finite element analysis code MSC.NASTRAN in order to investigate the structural safety. The result of structural analysis showed that the design has sufficient structural safety. It was concluded that structural safety assessment should incorporate the off-design points.

• Structural Engineering and Mechanics
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• v.46 no.2
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• pp.213-229
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• 2013

Although performance based assessment procedures are mainly developed for reinforced concrete and steel buildings, URM (Unreinforced Masonry) buildings occupy significant portion of buildings in earthquake prone areas of the world as well as in IRAN. Variability of material properties, non-engineered nature of the construction and difficulties in structural analysis of masonry walls make analysis of URM buildings challenging. Despite sophisticated finite element models satisfy the modeling requirements, extensive experimental data for definition of material behavior and high computational resources are needed. Recently, nonlinear equivalent frame models which are developed assigning lumped plastic hinges to isotropic and homogenous equivalent frame elements are used for nonlinear modeling of URM buildings. The equivalent frame models are not novel for the analysis of masonry structures, but the actual potentialities have not yet been completely studied, particularly for non-linear applications. In the present paper an effective tool for the non-linear static analysis of 2D masonry walls is presented. The work presented in this study is about performance assessment of unreinforced brick masonry buildings through nonlinear equivalent frame modeling technique. Reliability of the proposed models is tested with a reversed cyclic experiment conducted on a full scale, two-story URM building at the University of Pavia. The pushover curves were found to provide good agreement with the experimental backbone curves. Furthermore, the results of analysis show that EFM (Equivalent Frame Model) with Dolce RO (rigid offset zone) and shell element have good agreement with finite element software and experimental results.

• Architectural research
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• v.9 no.1
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• pp.39-45
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• 2007

The static behavior of continuous system is described by the elastic curve method or is approximately analyzed by a finite element method to be modeled as a discrete system. If a continuous system is constrained by linear constraints which restrict its static behavior, its behavior can be approximately described by the finite element method. It is not easy to describe the constrained behavior by continuous coordinate system. Starting from the generalized inverse method provided by Eun, Lee and Chung, this study is to expand the equation to the continuous systems, to perform the structural analysis of the beam under a uniform loading with interior spring supports, and to investigate the validity of the proposed method through applications.

• Structural Engineering and Mechanics
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• v.64 no.6
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• pp.751-763
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• 2017

This article deals with the buckling behaviour of multilayered magneto-electro-elastic (MEE) plate subjected to uniaxial and biaxial compressive (in-plane) loads. The constitutive equations of MEE material are used to derive a finite element (FE) formulation involving the coupling between electric, magnetic and elastic fields. The displacement field corresponding to first order shear deformation theory (FSDT) has been employed. The in-plane stress distribution within the MEE plate existing due to the enacted force is considered to be equivalent to the applied in-plane compressive load in the pre-buckling range. The same stress distribution is used to derive the potential energy functional. The non-dimensional critical buckling load is accomplished from the solution of allied linear eigenvalue problem. Influence of stacking sequence, span to thickness ratio, aspect ratio, load factor and boundary condition on critical buckling load and their corresponding mode shape is investigated. In addition, static deflection of MEE plate under the sinusoidal and the uniformly distributed load has been studied for different stacking sequences and boundary conditions.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.694-699
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• 2007

The spacer grid set is a part of a nuclear fuel assembly. The set has a spring and the spring supports the fuel rods safely. Although material nonlinearity is involved in the deformation of the spring,nonlinearity has not been considered in design of the spring. Recently a nonlinear response structural optimization method has been developed using equivalent loads. It is called nonlinear response optimization equivalent loads (NROEL). In NROEL, the external loads are teansformed to the equivalent loads (EL) for linear static analysis and linear response optimization is carried out based on the EL in a cyclic manner until the convergence criteria are satisfied. EL is the load set which generates the same response no EL. The objective function is defined by minimizing the maximum stress in the spring while is limited and the support force of the spring is larger than a certain value. The results are verified by nonlinear. ABAQUS is used for nonlinear response analysis and GENESIS is employed for linear response optimization.

• Structural Engineering and Mechanics
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• v.35 no.1
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• pp.67-82
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• 2010

The beam string structure (BSS) has been widely applied in large span roof structures, while no analytical solutions of BSS were derived for it in the existing literature. In the first part of this paper, calculation formulas of displacement and internal forces were obtained by the Ritz-method for the most commonly used arc-shaped BSS under the vertical uniformly distributed load and the prestressing force. Then, the failure mode of BSS was proposed based on the static equilibrium. On condition the structural stability was reliable, BSS under the uniformly distributed load would fail by tensile strength failure of the string, and the beam remained in the elastic or semi-plastic range. On this basis, the limit load of BSS was given in virtue of the elastic solutions. In order to verify the linear elastic and limit state solutions proposed in this paper, three BSS modal were tested and the corresponding elastoplastic large deformation analysis was performed by the ANSYS program. The proposed failure mode of BSS was proved to be correct, and the analytical results for the linear elastic and limit state were in good agreement with the experimental and FEM results.

• Structural Engineering and Mechanics
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• v.31 no.1
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• pp.75-91
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• 2009

It is known that retaining walls were severely damaged as well in the most recent earthquakes having occurred in the countries in the active seismic belts of the world. This damage can be ascribed to the calculation methods used for the designs of retaining walls in the event of their constructions and employment having been accurately carried out. Generally simplified pseudo-static methods are used in the analysis of retaining walls with analytical methods and soil-structure interaction are not considered. In view of these circumstances, in this article by taking soil interaction into consideration, linear and nonlinear behaviours of retaining walls are analyzed with the assistance of LUSAS which is one of the structural analysis programs. This investigations are carried out per LUSAS which employs the finite element method as to the Erzincan (1992) Earthquake North-South component and the obtained findings are compared with the ones obtained from the method suggested in Eurocode-8, which is still effective today, and Mononobe-Okabe method. Not only do the obtained results indicate the distribution and magnitude of soil pressures are depend on the filling soil but on the foundation soil as well and nonlinear effects should be considered in designs of these walls.

• Smart Structures and Systems
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• v.24 no.4
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• pp.507-524
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• 2019

A Bayesian dynamic linear model (BDLM) is presented for a data-driven analysis for response prediction and load effect separation of a revolving auditorium structure, where the main loads are self-weight and dead loads, temperature load, and audience load. Analyses are carried out based on the long-term monitoring data for static strains on several key members of the structure. Three improvements are introduced to the ordinary regression BDLM, which are a classificatory regression term to address the temporary audience load effect, improved inference for the variance of observation noise to be updated continuously, and component discount factors for effective load effect separation. The effects of those improvements are evaluated regarding the root mean square errors, standard deviations, and 95% confidence intervals of the predictions. Bayes factors are used for evaluating the probability distributions of the predictions, which are essential to structural condition assessments, such as outlier identification and reliability analysis. The performance of the present BDLM has been successfully verified based on the simulated data and the real data obtained from the structural health monitoring system installed on the revolving structure.