scholarly journals The influence of initial geometric imperfections on the buckling load of single and double curvature concrete shells

2012 ◽  
Vol 96-97 ◽  
pp. 34-45 ◽  
Author(s):  
Antonio Tomás ◽  
Juan Pedro Tovar
Keyword(s):  
Buckling Load ◽  
Geometric Imperfections ◽  
Double Curvature ◽  
Initial Geometric Imperfections ◽  
Concrete Shells

scholarly journals Hybrid Artificial Intelligence Approaches for Predicting Critical Buckling Load of Structural Members under Compression Considering the Influence of Initial Geometric Imperfections

2019 ◽  
Vol 9 (11) ◽  
pp. 2258 ◽  
Author(s):  
Hai-Bang Ly ◽  
Lu Minh Le ◽  
Huan Thanh Duong ◽  
Thong Chung Nguyen ◽  
Tuan Anh Pham ◽  
...  
Keyword(s):  
Artificial Intelligence ◽  
Mean Squared Error ◽  
Optimization Technique ◽  
Buckling Load ◽  
Structural Members ◽  
Geometric Imperfections ◽  
Inference System ◽  
Critical Buckling Load ◽  
Initial Geometric Imperfections ◽  
Hybrid Artificial Intelligence

The main aim of this study is to develop different hybrid artificial intelligence (AI) approaches, such as an adaptive neuro-fuzzy inference system (ANFIS) and two ANFISs optimized by metaheuristic techniques, namely simulated annealing (SA) and biogeography-based optimization (BBO) for predicting the critical buckling load of structural members under compression, taking into account the influence of initial geometric imperfections. With this aim, the existing results of compression tests on steel columns were collected and used as a dataset. Eleven input parameters, representing the slenderness ratios and initial geometric imperfections, were considered. The predicted target was the critical buckling load of columns. Statistical criteria, namely the correlation coefficient (R), the root mean squared error (RMSE), and the mean absolute error (MAE) were used to evaluate and validate the three proposed AI models. The results showed that SA and BBO were able to improve the prediction performance of the original ANFIS. Excellent results using the BBO optimization technique were achieved (i.e., an increase in R by 7.15%, RMSE by 40.48%, and MAE by 38.45%), and those using the SA technique were not much different (i.e., an increase in R by 5.03%, RMSE by 26.68%, and MAE by 20.40%). Finally, sensitivity analysis was performed, and the most important imperfections affecting column buckling capacity was found to be the initial in-plane loading eccentricity at the top and bottom ends of the columns. The methodology and the developed AI models herein could pave the way to establishing an advanced approach to forecasting damages of columns under compression.

Application of Modified Consistent Mode Imperfection Method in Stability Analysis of Single-Layer Reticulated Shells

2013 ◽  
Vol 477-478 ◽  
pp. 744-748 ◽  
Author(s):  
Sheng He ◽  
Jian Cai ◽  
Qi Qi Liu
Keyword(s):  
Stability Analysis ◽  
Single Layer ◽  
Buckling Load ◽  
Structure Stability ◽  
Geometric Imperfections ◽  
Stability Performance ◽  
Mode Method ◽  
Initial Geometric Imperfections ◽  
The Stability ◽  
Reticulated Shell Structure

Based on the probability reliability theory, this paper proposes a modified consistent mode imperfection method, which fits the integral stability analysis of single-layer reticulated shells with the initial geometric imperfections. Nearly 1000 elasto-plastic load-deflection overall processes of four different rise-to-span ratio for Kiewitt-8 single-layer reticulated shells are analyzed by using the random imperfection mode method, the consistent mode imperfection method and the modified consistent mode imperfection method respectively. The study shows that the random imperfection mode method can assess the influence of initial geometric imperfections on structure stability more scientifically, but the calculation is quite large. By using the consistent mode imperfection method, the buckling load is not sure to be the most unfavorable, and the degree of reliability couldnt be ensured effectively. The modified consistent mode imperfection method can gain the buckling load which meets the requirement of probability reliability with less calculation. It can also assess the stability performance of single-layer reticulated shell structure more reasonably and safely.

Appraisal of Allowable Loads by Simplified Rules

1986 ◽  
Vol 108 (2) ◽  
pp. 131-137
Author(s):  
D. Moulin
Keyword(s):  
Experimental Investigation ◽  
Plastic Region ◽  
Thin Structures ◽  
Geometric Imperfections ◽  
Buckling Behavior ◽  
Simplified Method ◽  
Post Buckling ◽  
Initial Geometric Imperfections ◽  
Fast Breeder Reactors ◽  
Breeder Reactors

This paper presents a simplified method to analyze the buckling of thin structures like those of Liquid Metal Fast Breeder Reactors (LMFBR). The method is very similar to those used for the buckling of beams and columns with initial geometric imperfections, buckling in the plastic region. Special attention is paid to the strain hardening of material involved and to possible unstable post-buckling behavior. The analytical method uses elastic calculations and diagrams that account for various initial geometric defects. An application of the method is given. A comparison is made with an experimental investigation concerning a representative LMFBR component.

Evaluation of Compressive Strengths of HPS Plate Systems Stiffened with Trapezoidal Stiffeners

2013 ◽  
Vol 671-674 ◽  
pp. 1025-1028
Author(s):  
Dong Ku Shin ◽  
Kyungsik Kim
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
High Performance ◽  
Nonlinear Finite Element ◽  
Linear Strain ◽  
Element Analysis ◽  
Geometric Imperfections ◽  
Eurocode 3 ◽  
Initial Geometric Imperfections ◽  
Plate System

The ultimate compressive strengths of high performance steel (HPS) plate system stiffened longitudinally by closed stiffeners have been investigated by the nonlinear finite element analysis. Both conventional and high performance steels were considered in models following multi-linear strain hardening constitutive relationships. Initial geometric imperfections and residual stresses were also incorporated in the analysis. Numerical results have been compared to compressive strengths from Eurocode 3 EN 1993-1-5 and FHWA-TS-80-205. It has been found that although use of Eurocode 3 EN 1993-1-5 and FHWA-TS-80-205 may lead to highly conservative design strengths when very large column slenderness parameters are encountered

Dynamic Buckling of Externally Pressurized Imperfect Cylindrical Shells

1975 ◽  
Vol 42 (2) ◽  
pp. 316-320 ◽  
Author(s):  
D. Lockhart ◽  
J. C. Amazigo
Keyword(s):  
Asymptotic Expression ◽  
Cylindrical Shells ◽  
Simple Relation ◽  
Dynamic Buckling ◽  
Fourier Component ◽  
Buckling Load ◽  
Buckling Mode ◽  
Geometric Imperfections ◽  
Circular Cylindrical Shells ◽  
Step Loading

The dynamic buckling of imperfect finite circular cylindrical shells subjected to suddenly applied and subsequently maintained lateral or hydrostatic pressure is studied using a perturbation method. The geometric imperfections are assumed small but arbitrary. A simple asymptotic expression is obtained for the dynamic buckling load in terms of the amplitude of the Fourier component of the imperfection in the shape of the classical buckling mode. Consequently, for small imperfection, there is a simple relation between the dynamic buckling load under step-loading and the static buckling load. This relation is independent of the shape of the imperfection.

scholarly journals ANÁLISE NUMÉRICA DE PERFIS DE AÇO FORMADOS A FRIO EM SEÇÃO “I” CONSTITUÍDA POR DUPLO “U” SUBMETIDOS À COMPRESSÃO

2020 ◽  
Vol 12 (1) ◽  
pp. 95-110
Author(s):  
Gabriel Cintra Macedo ◽  
Wanderson Fernando Maia
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Plate Thickness ◽  
Experimental Studies ◽  
Structural Behavior ◽  
The Finite Element Method ◽  
Geometric Imperfections ◽  
Initial Geometric Imperfections ◽  
Normal Strength ◽  
Double Channel

Although the section “I”, in double channel, is widely used, there are few studies on its behavior. Therefore, this work aims to contribute to a greater mastery over the structural behavior of this built-up sections. A nonlinear numerical analysis was performed using the Finite Element Method in the Ansys program, using existing experimental studies as a comparative database. The effect of length, number of connections, plate thickness and the presence of geometric and material imperfections on the normal strength of the columns. For this analysis, it was essential to consider the initial geometric imperfections, because there was a considerable reduction in the normal strength of the columns, thus getting closer to the values obtained experimentally. With regard to normative procedures, values against security were found in most cases, showing the need to conduct further studies in the area for the development of more appropriate formulations.

Clamped torispherical shells under external pressure — some new results

1988 ◽  
Vol 23 (1) ◽  
pp. 9-24 ◽  
Author(s):  
J Blachut ◽  
G D Galletly
Keyword(s):  
Failure Mode ◽  
External Pressure ◽  
Spherical Cap ◽  
Geometric Imperfections ◽  
Collapse Pressure ◽  
Modes Of Failure ◽  
Shell Buckling ◽  
Bifurcation Buckling ◽  
Initial Geometric Imperfections ◽  
The One

Perfect clamped torispherical shells subjected to external pressure are analysed in the paper using the BOSOR 5 shell buckling program. Various values of the knuckle radius-to-diameter ratio ( r/D) and the spherical cap radius-to-thickness ratio ( Rs/ t) were studied, as well as four values of σyp, the yield point of the material. Buckling/collapse pressures, modes of failure and the development of plastic zones in the shell wall were determined. A simple diagram is presented which enables the failure mode in these shells to be predicted. The collapse pressures, pc, were also plotted against the parameter Λs (√( pyp/ pcr)). When the controlling failure mode was axisymmetric yielding in the knuckle, the collapse pressure curves depended on the value of σyp, which is unusual. However, when the controlling failure mode was bifurcation buckling (at the crown/knuckle junction), the collapse pressure curves for the various values of σyp all merged, i.e., they were independent of σyp. This latter situation is the one which normally occurs with the buckling of cylindrical and hemispherical shells. A limited investigation was also made into the effects of axisymmetric initial geometric imperfections on the strength of externally-pressurised torispherical shells. When the failure mode was axisymmetric yielding in the knuckle, initial imperfections of moderate size did not affect the collapse pressures. In the cases where bifurcation buckling at the crown/knuckle junction occurred, small initial geometric imperfections at the apex did not affect the buckling pressure, but axisymmetric imperfections at the buckle location did influence it. With the other failure mode (i.e., axisymmetric yielding collapse at the crown of the shell), initial geometric imperfections caused a reduction in the torisphere's strength.

Thermo-Mechanical Buckling Analysis of Functionally Graded Skew Laminated Plates with Initial Geometric Imperfections

2018 ◽  
Vol 10 (02) ◽  
pp. 1850014 ◽  
Author(s):  
Sanjay Singh Tomar ◽  
Mohammad Talha
Keyword(s):  
Shear Deformation Theory ◽  
Functionally Graded ◽  
Laminated Plates ◽  
Geometric Imperfections ◽  
Efficiency And Effectiveness ◽  
Governing Differential Equation ◽  
Parametric Studies ◽  
Mechanical Buckling ◽  
Initial Geometric Imperfections ◽  
Continuous Displacement

The aim of the present study is to investigate thermo-mechanical buckling response of skew functionally graded laminated plates (FGLP) with initial geometric imperfections. The formulation has been performed using Reddy’s higher order shear deformation theory (HSDT) with the [Formula: see text] continuous displacement field. A nine-noded isoparametric element has been employed to discretize the domain of the plate. Variational principle has been used to derive the governing differential equation of the problem. Several examples with various comparison and parametric studies have been shown to prove the efficiency and effectiveness of the present formulation. The numerical results have been highlighted with different system parameters and boundary conditions.

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