• 콘크리트학회논문집
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• 제11권5호
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• pp.33-40
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• 1999

An improved finite element modeling technique is proposed for the assessment of load carrying capacity of partially prestressed concrete girder bridges. Based on the finite element method of analysis, shell and frame elements are used to model the slab and girders of the superstructure, respectively. In the modeling of superstructure, the emphasis is placed on the use of rigid link between the middle surface of slab an mid-plane of girder. This paper also includes the comparision of three different equations that are used in the calculation of effective moment of inertia for the partially prestressed concrete girders. Numerical analysis is performed for the unstrengthened and strengthened bridges. The obtained results are compared with those of load test for a prototype bridge. A good agreement is achieved between the numerical solutions by using the proposed method load test results.

• Wind and Structures
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• 제3권4호
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• pp.291-302
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• 2000

A new finite element technique to solve the problem of wind and structure interactions is presented. Conventionally, wind analysis is performed on the Eulerian description in which the finite element mesh would not move in accordance with the wind flow. However, it is not the case in wind-structure interaction problems because nodes attached to the surface of structure should move with the displacement of structure. The arbitrary Lagrangian-Eulerian (ALE) method treats the mesh and flow independently, and allow the mesh to move. In this study, the analysis domain is divided into regions of the structure, air around the structure and the interface of two regions. To satisfy the compatibility and equilibrium conditions between separated regions and to carry out the efficient analysis, the rigid link is used. Also the equation of wind and that of structure are arranged in a single matrix equation.

• 한국소음진동공학회논문집
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• 제15권3호
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• pp.251-258
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• 2005

The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings (HDB) in an HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Reynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigen value problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.572-578
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• 2003

The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings in a HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Raynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigenvalue problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.

• Structural Engineering and Mechanics
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• 제60권2호
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• pp.251-269
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• 2016

In common structural systems, there are some limitations to provide adequate lateral stiffness, high ductility, and architectural openings simultaneously. Consequently, the concept of T-Resisting Frame (TRF) has been introduced to improve the performance of structures. In this study, Configuration of TRF is a Vertical I-shaped Plate Girder (V.P.G) which is placed in the middle of the span and connected to side columns by two Horizontal Plate Girders (H.P.Gs) at each story level. System performance is improved by utilizing rigid connections in link beams (H.P.Gs). Plastic deformation leads to tension field action in H.P.Gs and causes energy dissipation in TRF; therefore, V.P.G. High plastic deformation in web of TRF's members affects the ductility of system. Moreover, in order to prevent shear buckling in web of TRF's members and improve overall performance of the system, appropriate criteria for placement of web stiffeners are presented in this study. In addition, an experimental study is conducted by applying cyclic loading and using finite element models. As a result, hysteresis curves indicate adequate lateral stiffness, stable hysteretic behavior, and high ductility factor of 6.73.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.399-404
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• 1999

An improved finite element modeling technique is proposed for the assessment of load carrying capacity partilly prestressed concrete beam bridges. Based on the finite element method of analysis, shell and frame elements are utilized to model the slab and beams of the superstructure, respectively. In the modeling of superstructure, the emphasis is placed on the use of rigid link between the middle surface of slab and mid-plane of beam. This paper also includes the comparision of three different equations that used in the calculation of effective moment of inertia for the partially prestressed concrete beams. Numerical analysis is performed for the unstrengthened and strengthened bridges. The obtained results are compared with those of load test for a prototype bridge. Agreement with the numerical solutions by using the proposed method and load test results is generally excellent.

• Structural Engineering and Mechanics
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• 제8권1호
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• pp.85-102
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• 1999

With the advent of computer, the finite element method has become a most powerful numerical method for structural analysis. However, bridge designers are reluctant to use it in their designs because of its complex nature and its being time consuming in the preparation of the input data and analyzing the results. This paper describes the development of a computer based finite element model using the idea of eccentric beam elements for the analysis of slab-on-girder bridges. The proposed method is supported by a laboratory test using a reinforced concrete bridge model. Other bridge analytical schemes are also introduced and compared with the proposed method. The main aim of the comparison is to prove the effectiveness of the shell and eccentric beam modelling in the studies of lateral load distribution of slab-on-girder bridges. It is concluded that the proposed finite element method gives a closer to real idealization and its developed computer program, SHECAN, is also very simple to use. It is highly recommended to use it as an analytical tool for the design of slab-on-girder bridges.

• Coupled systems mechanics
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• 제11권5호
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• pp.439-458
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• 2022

Over-coating is one of the most popular engineering practices to strengthen Reinforced Concrete (RC) structures, due to the relative quickness and ease of construction. It consists of an external coat bonded to the outer surface of the structural RC element, either by the use of chemical adhesives, mechanical anchor bolts or simply mortar injection. In contrast to these constructive advantages, the numerical estimation of the bearing capacity of the strengthened reinforced concrete element is still complicated, not only for the complexity of modelling a flexible membrane or plate attached to a quasi-rigid solid, but also for the difficulties that raise of simulating any potential delamination between both materials. For these reasons, the standard engineering calculations used in the practice remain very approximated and clumsy. In this work, we propose the formulation of a new 2D solid-layer finite element capable to link a solid body with a flexible thin layer, as it were the "skin" of the body, allowing the potential delamination between both materials. In numerical terms, this "skin" element is intended to work as a transitional region between a solid body (modelled with a classical formulation of a standard quadrilateral four-nodes element) and a flexible coat layer (modelled with cubic beam element), dealing with the incompatibility of Degrees-Of-Freedom between them (two DOF for the solid and three DOF for the beam). The aim of the solid-layer element is to simplify the mesh construction of the strengthened RC element being aware of two aspects: a) to prevent the inappropriate use of very small solid elements to simulate the coat; b) to improve the numerical estimation of the real bearing capacity of the strengthened element when the coat is attached or detached from the solid body.

• Coupled systems mechanics
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• 제12권6호
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• pp.481-501
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• 2023

Over-coating is one of the most popular engineering practices to strengthen Reinforced Concrete (RC) structures, due to the relative quickness and ease of construction. It consists of an external coat bonded to the outer surface of the structural RC element, either by the use of chemical adhesives, mechanical anchor bolts or simply mortar injection. In contrast to these constructive advantages, the numerical estimation of the bearing capacity of the strengthened reinforced concrete element is still complicated, not only for the complexity of modelling a flexible membrane or plate attached to a quasi-rigid solid, but also for the difficulties that raise of simulating any potential delamination between both materials. For these reasons, the standard engineering calculations used in the practice remain very approximated and clumsy. In this work, we propose the formulation of a new 2D solid-layer finite element capable to link a solid body with a flexible thin layer, as it were the "skin" of the body, allowing the potential delamination between both materials. In numerical terms, this "skin" element is intended to work as a transitional region between a solid body (modelled with a classical formulation of a standard quadrilateral four-nodes element) and a flexible coat layer (modelled with cubic beam element), dealing with the incompatibility of Degrees-OfFreedom between them (two DOF for the solid and three DOF for the beam). The aim of the solid-layer element is to simplify the mesh construction of the strengthened RC element being aware of two aspects: a) to prevent the inappropriate use of very small solid elements to simulate the coat; b) to improve the numerical estimation of the real bearing capacity of the strengthened element when the coat is attached or detached from the solid body.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1992년도 가을 학술발표회 논문집
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• pp.133-138
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• 1992

The three dimensional analysis of Framed-Tube structures is neither easy nor efficient because of longer computational time, large memory requirement, tedious input preparation and bulky output. An efficient analysis model for framed-tube structure is proposed in this study. The proposed model can save the computational effort by using the assumption of the rigid floor diaphragm effect and matrix condensation technique. Moreover, it is develpoed by assembling two dimensional frames using the link degrees of freedom which are temporary used to satisfy the vertical displacement compatibility at the corners of a framed-tube. The accuracy and the efficiency of this analytical model is established by comparing with the results using the computer code SAPIV which is based on the three dimensional finite element model.