• Title, Summary, Keyword: nonlinear dynamic analysis

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Effects of damping ratio on dynamic increase factor in progressive collapse

  • Mashhadi, Javad;Saffari, Hamed
    • Steel and Composite Structures
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    • v.22 no.3
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    • pp.677-690
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    • 2016
  • In this paper, the effect of damping ratio on nonlinear dynamic analysis response and dynamic increase factor (DIF) in nonlinear static analysis of structures against column removal are investigated and a modified empirical DIF is presented. To this end, series of low and mid-rise moment frame structures with different span lengths and number of storeys are designed and the effect of damping ratio in DIF is investigated, performing several nonlinear static and dynamic analyses. For each damping ratio, a nonlinear dynamic analysis and a step by step nonlinear static analysis are carried out and the modified empirical DIF formulas are derived. The results of the analysis reveal that DIF is decreased with increasing damping ratio. Finally, an empirical formula is recommended that relates to damping ratio. Therefore, the new modified DIF can be used with nonlinear static analysis instead of nonlinear dynamic analysis to assess the progressive collapse potential of moment frame buildings with different damping ratios.

Nonlinear Dynamic Response Structural Optimization of an Automobile Frontal Structure Using Equivalent Static Loads (등가정하중법을 이용한 차량 전면 구조물의 비선형 동적 반응 구조최적설계)

  • Yoon, Shic;Jeong, Seong-Beom;Park, Gyung-Jin
    • Proceedings of the KSME Conference
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    • pp.1156-1161
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    • 2008
  • Nonlinear dynamic analysis is generally used in automobile crash analysis and structural optimization considering crashworthiness uses the results of nonlinear dynamic analysis. Automobile crash optimization has high nonlinearity and difficulty in calculating sensitivity. Recently the equivalent static load (ESL) method has been proposed in order to overcome these difficulties. The ESL is the static load set generating the same displacement field as the nonlinear dynamic displacement field at each time step in dynamic analysis. From various researches regarding the ESL method, it has been proved that the ESL method is fairly useful. The ESL method can mathematically optimize a crash optimization problem through nonlinear analysis and well developed static optimization. The ESL is applied to nonlinear dynamic structural optimization of the automobile frontal impact problem. An automobile bumper is optimized. The mass of the structure is minimized while some constraints are satisfied.

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A performance based strategy for design of steel moment frames under blast loading

  • Ashkezari, Ghasem Dehghani
    • Earthquakes and Structures
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    • v.15 no.2
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    • pp.155-164
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    • 2018
  • Design of structures subjected to blast loads are usually carried out through nonlinear inelastic dynamic analysis followed by imposing acceptance criteria specified in design codes. In addition to comprehensive aspects of inelastic dynamic analyses, particularly in analysis and design of structures subjected to transient loads, they inherently suffer from convergence and computational cost problems. In this research, a strategy is proposed for design of steel moment resisting frames under far range blast loads. This strategy is inspired from performance based seismic design concepts, which is here developed to blast design. For this purpose, an algorithm is presented to calculate the capacity modification factors of frame members in order to simplify design of these structures subjected to blast loading. The present method provides a simplified design procedure in which the linear dynamic analysis is preformed, instead of the time-consuming nonlinear dynamic analysis. Nonlinear and linear analyses are accomplished in order to establish this design procedure, and consequently the final design procedure is proposed as a strategy requiring only linear structural analysis, while acceptance criteria of nonlinear analysis is implicitly satisfied.

Evaluation of dynamic increase factor in progressive collapse analysis of steel frame structures considering catenary action

  • Ferraioli, Massimiliano
    • Steel and Composite Structures
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    • v.30 no.3
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    • pp.253-269
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    • 2019
  • This paper investigates the effects of the tensile catenary action on dynamic increase factor (DIF) in the nonlinear static analysis for progressive collapse of steel-frame buildings. Numerical analyses were performed to verify the accuracy of the empirical and analytical expressions proposed in the literature in cases where the catenary action is activated. For this purpose, nonlinear static and dynamic analyses of a series of steel moment frame buildings with a different number of spans and stories were carried out following the alternate path method. Different column removal scenarios were considered as separate load cases. The dynamic increase factor that approximately compensates for the dynamic effects in the nonlinear static analysis was selected so to match results from the nonlinear dynamic analysis. The study results showed that the many expressions in literature may not work in cases where the catenary stage is fully developed.

Approximate Analysis for Shear Force Amplification Effect in Ordinary RC Shear Walls (철근콘크리트 보통전단벽의 전단력 증폭효과 근사해석)

  • Jeon, Seong-Ha;Park, Ji-Hun
    • Journal of the Earthquake Engineering Society of Korea
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    • v.24 no.3
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    • pp.129-139
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    • 2020
  • An approximate analysis method is proposed to predict the dynamic amplification of shear forces in ordinary reinforced concrete shear walls as a preliminary study. First, a seismic design for three groups of ordinary reinforced concrete shear walls higher than 60 m was created on the basis of nonlinear dynamic analysis. Causes for the dynamic amplification effect of shear forces were investigated through a detailed evaluation of the nonlinear dynamic analysis result. A new modal combination rule was proposed on the basis of that observation, in which fundamental mode response and combined higher mode response were summed directly. The fundamental mode response was approximated by nonlinear static analysis result, while higher mode response was computed using response spectrum analysis for equivalent linear structural models with the effective stiffness based on the nonlinear dynamic analysis result. The proposed approximate analysis generally predicted vertical distribution of story shear and shear forces of individual walls from the nonlinear dynamic analysis with comparable accuracy.

Nonlinear dynamic analysis for large-span single-layer reticulated shells subjected to wind loading

  • Li, Yuan-Qi;Tamura, Yukio
    • Wind and Structures
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    • v.8 no.1
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    • pp.35-48
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    • 2005
  • Wind loading is very important in structural design of large-span single-layer reticulated shell structures. In this paper, a geometrically nonlinear wind-induced vibration analysis strategy for large-span single-layer reticulated shell structures based on the nonlinear finite element method is introduced. According to this strategy, a computation program has been developed. With the information of the wind pressure distribution measured simultaneously in the wind tunnel, nonlinear dynamic analysis, including dynamic instability analysis, for the wind-induced vibration of a single-layer reticulated shell is conducted as an example to investigate the efficiency of the strategy. Finally, suggestions are given for dynamic wind-resistant analysis of single-layer reticulated shells.

Nonlinear analysis of thin shallow arches subject to snap-through using truss models

  • Xenidis, H.;Morfidis, K.;Papadopoulos, P.G.
    • Structural Engineering and Mechanics
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    • v.45 no.4
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    • pp.521-542
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    • 2013
  • In this study a truss model is used for the geometrically nonlinear static and dynamic analysis of a thin shallow arch subject to snap-through. Thanks to the very simple geometry of a truss, the equilibrium conditions can be easily written and the global stiffness matrix can be easily updated with respect to the deformed structure, within each step of the analysis. A very coarse discretization is applied; so, in a very simple way, the high frequency modes are suppressed from the beginning and there is no need to develop a complicated reduced-order technique. Two short computer programs have been developed for the geometrically nonlinear static analysis by displacement control of a plane truss model of a structure as well as for its dynamic analysis by the step-by-step time integration algorithm of trapezoidal rule, combined with a predictor-corrector technique. These two short, fully documented computer programs are applied on the geometrically nonlinear static and dynamic analysis of a specific thin shallow arch subject to snap-through.

Nonlinear dynamic analysis by Dynamic Relaxation method

  • Rezaiee-Pajand, M.;Alamatian, J.
    • Structural Engineering and Mechanics
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    • v.28 no.5
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    • pp.549-570
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    • 2008
  • Numerical integration is an efficient approach for nonlinear dynamic analysis. In this paper, general category of the implicit integration errors will be discussed. In order to decrease the errors, Dynamic Relaxation method with modified time step (MFT) will be used. This procedure leads to an alternative algorithm which is very general and can be utilized with any implicit integration scheme. For numerical verification of the proposed technique, some single and multi degrees of freedom nonlinear dynamic systems will be analyzed. Moreover, results are compared with both exact and other available solutions. Suitable accuracy, high efficiency, simplicity, vector operations and automatic procedures are the main merits of the new algorithm in solving nonlinear dynamic problems.

Nonlinear dynamic analysis of spiral stiffened functionally graded cylindrical shells with damping and nonlinear elastic foundation under axial compression

  • Foroutan, Kamran;Shaterzadeh, Alireza;Ahmadi, Habib
    • Structural Engineering and Mechanics
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    • v.66 no.3
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    • pp.295-303
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    • 2018
  • The semi-analytical method to study the nonlinear dynamic behavior of simply supported spiral stiffened functionally graded (FG) cylindrical shells subjected to an axial compression is presented. The FG shell is surrounded by damping and linear/nonlinear elastic foundation. The proposed linear model is based on the two-parameter elastic foundation (Winkler and Pasternak). A three-parameter elastic foundation with hardening/softening cubic nonlinearity is used for nonlinear model. The material properties of the shell and stiffeners are assumed to be FG. Based on the classical plate theory of shells and von $K{\acute{a}}rm{\acute{a}}n$ nonlinear equations, smeared stiffeners technique and Galerkin method, this paper solves the nonlinear vibration problem. The fourth order Runge-Kutta method is used to find the nonlinear dynamic responses. Results are given to consider effects of spiral stiffeners with various angles, elastic foundation and damping coefficients on the nonlinear dynamic response of spiral stiffened simply supported FG cylindrical shells.

Geometrical nonlinear dynamic analysis of laminated skew plates made of advanced composite materials (적층된 ACM 경사판의 기하학적 비선형 동적 해석)

  • Lee, Sang-Youl;Chang, Suk-Yoon
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.1 no.4
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    • pp.28-34
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    • 2010
  • W e performed a geometrical nonlinear dynamic analysis of laminated skew plates made of advanced composite materials (ACM ) based on the first-order shear deformation plate theory (FSDT). The Newmark method and Newton-Raphson iteration are used for the nonlinear dynamic solution. The effects of skew angles and layup sequences on the nonlinear dynamic response for various parameters are studied using a nonlinear dynamic finite element program developed for this study. The several numerical results were in good agreement with those reported by other investigators for square composite and skew plates, and the new results reported in this paper show the significant interactions between the skew angle and layup sequence in the skew laminate. Key observation points are discussed and a brief design guideline is given.

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