• Title, Summary, Keyword: non-linear analysis

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Ride Sensitivity Analysis of a Train Model with Non-linear Suspension Elements (비선형 현가요소를 가진 철도차량의 승차감 민감도 해석)

  • Tak, Tae-oh;Kim, Myung-hun
    • Journal of Industrial Technology
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    • v.18
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    • pp.233-240
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    • 1998
  • In this study, ride sensitivity analysis of train with non-linear suspension elements is performed. Non-linear characteristics of springs and dampers for primary and secondary suspensions of a train is parameterized. Equation of motion of the train model is derived, and using the direct differentiation method, sensitivity equations are obtained. For a nominal ride quality performance index, sensitivity analysis with respect to various design parameters regarding non-linear suspension parameters is carried out.

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Duality in non-linear programming for limit analysis of not resisting tension bodies

  • Baratta, A.;Corbi, O.
    • Structural Engineering and Mechanics
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    • v.26 no.1
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    • pp.15-30
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    • 2007
  • In the paper, one focuses on the problem of duality in non-linear programming, applied to the solution of no-tension problems by means of Limit Analysis (LA) theorems for Not Resisting Tension (NRT) models. In details, one demonstrates that, starting from the application of the duality theory to the non-linear program defined by the static theorem approach for a discrete NRT model, this procedure results in the definition of a dual problem that has a significant physical meaning: the formulation of the kinematic theorem.

A study on response analysis of submerged floating tunnel with linear and nonlinear cables

  • Yarramsetty, Poorna Chandra Rao;Domala, Vamshikrishna;Poluraju, P.;Sharma, R.
    • Ocean Systems Engineering
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    • v.9 no.3
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    • pp.219-240
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    • 2019
  • This paper presents the comparison between SFT response with linear and nonlinear cables. The dynamic response analysis of submerged floating tunnel (SFT) is presented computationally with linear and nonlinear tension legs cables. The analysis is performed computationally for two wave directions one at 90 degrees (perpendicular) to tunnel and other at 45 degrees to the tunnel. The tension legs or cables are assumed as linear and non- linear and the analysis is also performed by assuming one tension leg or cable is failed. The Response Amplitude Operators (RAO's) are computed for first order waves, second order waves for both failure and non-failure case of cables. For first order waves- the SFT response is higher for sway and heave degree of freedom with nonlinear cables as compared with linear cables. For second order waves the SFT response in sway degree of freedom is bit higher response with linear cables as compared with nonlinear cables and the SFT in heave degree of freedom has higher response at low time periods with nonlinear cables as compared with linear cables. For irregular waves the power spectral densities (PSD's) has been computed for sway and heave degrees of freedom, at $45^0$ wave direction PSD's are higher with linear cables as compared with nonlinear cables and at $90^0$ wave direction the PSD's are higher with non-linear cables. The mooring force responses are also computed in y and z directions for linear and nonlinear cables.

Long-term structural analysis and stability assessment of three-pinned CFST arches accounting for geometric nonlinearity

  • Luo, Kai;Pi, Yong-Lin;Gao, Wei;Bradford, Mark A.
    • Steel and Composite Structures
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    • v.20 no.2
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    • pp.379-397
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    • 2016
  • Due to creep and shrinkage of the concrete core, concrete-filled steel tubular (CFST) arches continue to deform in the long-term under sustained loads. This paper presents analytical investigations of the effects of geometric nonlinearity on the long-term in-plane structural performance and stability of three-pinned CFST circular arches under a sustained uniform radial load. Non-linear long-term analysis is conducted and compared with its linear counterpart. It is found that the linear analysis predicts long-term increases of deformations of the CFST arches, but does not predict any long-term changes of the internal actions. However, non-linear analysis predicts not only more significant long-term increases of deformations, but also significant long-term increases of internal actions under the same sustained load. As a result, a three-pinned CFST arch satisfying the serviceability limit state predicted by the linear analysis may violate the serviceability requirement when its geometric nonlinearity is considered. It is also shown that the geometric nonlinearity greatly reduces the long-term in-plane stability of three-pinned CFST arches under the sustained load. A three-pinned CFST arch satisfying the stability limit state predicted by linear analysis in the long-term may lose its stability because of its geometric nonlinearity. Hence, non-linear analysis is needed for correctly predicting the long-term structural behaviour and stability of three-pinned CFST arches under the sustained load. The non-linear long-term behaviour and stability of three-pinned CFST arches are compared with those of two-pinned counterparts. The linear and non-linear analyses for the long-term behaviour and stability are validated by the finite element method.

A partial factors methodology for structural safety assessment in non-linear analysis

  • Castro, Paula M.R.P.;Delgado, Raimundo M.;Cesar de Sa, Jose M.A.
    • Computers and Concrete
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    • v.2 no.1
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    • pp.31-53
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    • 2005
  • In the present structural codes the safety verification is based on a linear analysis of the structure and the satisfaction of ultimate and serviceability limit states, using a semi-probabilistic security format through the consideration of partial safety factors, which affect the action values and the characteristic values of the material properties. In this context, if a non-linear structural analysis is wanted a difficulty arises, because the global safety coefficient, which could be obtained in a straightforward way from the non-linear analysis, is not directly relatable to the different safety coefficient values usually used for the different materials, as is the case for reinforced concrete structures. The work here presented aims to overcome this difficulty by proposing a methodology that generalises the format of safety verification based on partial safety factors, well established in structural codes within the scope of linear analysis, for cases where non-linear analysis is needed. The methodology preserves the principal assumptions made in the codes as well as a reasonable simplicity in its use, including a realistic definition of the material properties and the structural behaviour, and it is based on the evaluation of a global safety coefficient. Some examples are presented aiming to clarify and synthesise all the options that were taken in the application of the proposed methodology, namely how to transpose the force distributions obtained with a non-linear analysis into design force distributions. One of the most important features of the proposed methodology, the ability for comparing the simplified procedures for second order effects evaluation prescribed in the structural codes, is also presented in a simple and systematic way. The potential of the methodology for the development and assessment of alternative and more accurate procedures to those already established in codes of practice, where non-linear effects must be considered, is also indicated.

Geometrically Non-linear Analysis of Shell Structures (쉘구조물의 기하학적 비선형해석)

  • Jang, Myung-Ho;Kim, Jae-Yeol;Sur, Sam-Yeol
    • Journal of Korean Association for Spatial Structures
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    • v.3 no.4
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    • pp.85-92
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    • 2003
  • In this work, a finite element model is presented for geometrically non-linear analysis of shell structures. Finite element by using a three-node flat triangular shell element is formulated. The non-linear incremental equilibrium equations are formulated by using an updated Lagrangian formulation and the solutions are obtained with the incremental/iterative Newton-Raphson method and arc length method. Some of results are presented for shell structures. The obtained results are in good agreement with the results available in existing literature.

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Structural Optimization of Truss with Non-Linear Response Using Equivalent Linear Loads (선형등가하중을 이용한 비선형 거동을 하는 트러스 구조물의 최적설계)

  • Park, Ki-Jong;Park, Gyung-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.4
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    • pp.467-474
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    • 2004
  • A numerical method and algorithms is proposed to perform optimization of non-linear response structures. An analytical and numerical method based finite element method is also proposed for the transformation of non-linear response into linear response. Loads transformed from this method are defined as the equivalent linear loads. With the loads and the transformed response, linear static optimization is performed for nonlinear response structure with geometric and/or material non-linearity. The results of the optimization are compared with them of typical non-linear response optimization using finite difference method. The proposed method is very efficient and derives good solution.

Earthquake performance evaluation of three-dimensional roller compacted concrete dams

  • Kartal, Murat Emre;Karabulut, Muhammet
    • Earthquakes and Structures
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    • v.14 no.2
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    • pp.167-178
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    • 2018
  • A roller compacted concrete (RCC) dam should be analyzed under seismic ground motions for different conditions such as empty reservoir and full reservoir conditions. This study presents three-dimensional earthquake response and performance of a RCC dam considering materially non-linearity. For this purpose, Cine RCC dam constructed in Aydın, Turkey, is selected in applications. The three-dimensional finite element model of Cine RCC dam is obtained using ANSYS software. The Drucker-Prager material model is considered in the materially nonlinear time history analyses for concrete and foundation rock. Furthermore, hydrodynamic effect was investigated in linear and non-linear dynamic analyses. Researchers observe that how the tensile and compressive stresses change by hydrodynamic pressure effect. The hydrodynamic pressure of the reservoir water is modeled with the fluid finite elements based on the Lagrangian approach. In this study, dam body and foundation are modeled with welded contact. The displacements and principle stress components obtained from the linear and non-linear analyses with and without reservoir water are compared each other. Principle stresses during earthquake were obtained at the most critical point in the upstream face of dam body. Besides, the change of displacements and stresses by crest length were investigated. Moreover demand-capacity ratio criteria were also studied under linear dynamic and nonlinear analysis. Earthquake performance analyses were carried out for different cases and evaluated. According to linear and nonlinear analysis, hydrodynamic water effect is obvious in full reservoir situation. On the other hand, higher tensile stresses were observed in linear analyses and then non-linear analyses were performed and compared with each other.

Analysis of Orthotropic Bearing Non-linearity Using Non-linear FRFs

  • Han Dong-Ju
    • Journal of Mechanical Science and Technology
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    • v.20 no.2
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    • pp.205-211
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    • 2006
  • Among other critical conditions in rotor systems the large non-linear vibration excited by bearing non-linearity causes the rotor failure. For reducing this catastrophic failure and predictive detection of this phenomenon the analysis of orthotropic bearing non-linearity in rotor system using higher order frequency response functions (HFRFs) is conducted and is shown to be theoretically feasible as that of non-rotating structures. The complex HFRFs based on the Volterra series are newly developed for the process and investigated their features by using the simple forms of the FRFs associated with the forward and the backward modes.

Non-linear performance analysis of existing and concentric braced steel structures

  • Erdem, R. Tugrul
    • Steel and Composite Structures
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    • v.19 no.1
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    • pp.59-74
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    • 2015
  • Since there are several places located in active seismic zones in the world, serious damages and losses have happened due to major scaled earthquakes. Especially, structures having different irregularities have been severely damaged or collapsed during these seismic events. Behavior of existing structures under several loading conditions is not completely determined due to some uncertainties. This situation reveals the importance of design and analysis of structures under seismic effects. Several non-linear static procedures have been developed in recent years. Determination of the seismic safety of the existing structures and strengthening techniques are significant civil engineering problems Non-linear methods are defined in codes to determine the performance levels of structures more accurately. However, displacement based ones give more realistic results. These methods provide more reliable evaluation possibilities for existing structures with developing computer technology. In this study, non-linear performance analysis of existing and strengthened steel structures by X shaped bracing members with 3, 5 and 7 stories which have soft story irregularity is performed according to FEMA-356 and Turkish Earthquake Code-2007. Damage ratios of the structural members and global performance levels are determined as well as modal properties and story drift ratios after non-linear finite elements analysis for each structure.