Effect of Imperfections on Buckling of Thin Cylinders and Columns Under Axial Compression

1950 ◽  
Vol 17 (1) ◽  
pp. 73-83 ◽  
Author(s):  
L. H. Donnell ◽  
C. C. Wan
Keyword(s):  
Axial Compression ◽  
Shell Theory ◽  
Large Deflection ◽  
Strain Curve ◽  
Test Results ◽  
Average Strain ◽  
Lower Yield ◽  
Initial Imperfections ◽  
Buckling Failure ◽  
Type Of Failure

Abstract Von Kármán and Tsien have shown that under elastic conditions the resistance of perfect thin cylinders subjected to axial compression drops precipitously after buckling. It is considered that this indicates that this type of buckling is very sensitive to imperfections or disturbances. In this paper the effects of certain imperfections of shape (assumed to be equivalent to all the actual defects or disturbances combined) are studied by the large-deflection shell theory developed in a previous paper (2). It is found that two types of buckling failure may occur. One is of a purely elastic type which occurs when the peak of the average stress versus average strain curve is reached, while the other type is precipitated by yielding, which for thicker cylinders or lower-yield material may occur before such a peak is reached. Curves are derived giving the dependence of each type of failure upon the dimensions and elastic and yield properties of the specimen and also upon an “unevenness factor” U which determines the magnitude of the initial imperfections and is assumed to depend on the method of fabrication. The relations derived are in line with test results, and similar studies of the buckling of struts indicate that the magnitude of the initial imperfections which have to be assumed to explain test strengths are reasonable.

scholarly journals Hopkinson rod test results and constitutive description of TRIP780 steel resistance spot welding material

Open Physics ◽  
2020 ◽  
Vol 18 (1) ◽  
pp. 961-967
Author(s):  
Xiaomin Li ◽  
Jianrong Zhang
Keyword(s):  
Spot Welding ◽  
Steel Strip ◽  
Strain Curve ◽  
Test Machine ◽  
Strain Rates ◽  
Test Results ◽  
Welding Material ◽  
Static Tensile ◽  
Split Hopkinson ◽  
Brittle Fractures

Abstract A quasi-static tensile test was performed on a 1.4 mm-thick TRIP780 steel strip with welding points. An MTS810 material test machine was used in the test, and a Split Hopkinson tension bar device was used in performing impact stretch loading at different strain rates. The dynamic tensile stress–strain curve of the spot welding material with different strain rates was obtained through the finely designed Hopkinson rod test, and the strain rate dependence of a TRIP780 steel spot welding material was discussed. According to the dynamic constitutive equation of the TRIP780 steel spot welding material, the test results were numerically simulated, the constitutive description and test curves were compared, and the simulation results and test results were discussed and analyzed. The fractures of the test recovery specimen were scanned with the scanning electron microscope, and the fracture mechanism of the TRIP780 steel spot welding material was explored by observing the fractures. The surfaces of the fractures surface showed obvious cleavage river patterns, and the evolution process of microcracks was determined and used in characterizing brittle fractures in specimen spot welding sample subjected to dynamic stretch loading.

scholarly journals Confinement effects for rubberised concrete in tubular steel cross-sections under combined loading

2021 ◽  
Vol 21 (2) ◽  
Author(s):  
A. Mujdeci ◽  
D. V. Bompa ◽  
A. Y. Elghazouli
Keyword(s):  
Axial Compression ◽  
Cross Section ◽  
Cross Sections ◽  
Image Correlation ◽  
Combined Loading ◽  
Test Results ◽  
Compression Tests ◽  
Confinement Effects ◽  
Rubber Content ◽  
Dependent Modification

AbstractThis paper describes an experimental investigation into confinement effects provided by circular tubular sections to rubberised concrete materials under combined loading. The tests include specimens with 0%, 30% and 60% rubber replacement of mineral aggregates by volume. After describing the experimental arrangements and specimen details, the results of bending and eccentric compression tests are presented, together with complementary axial compression tests on stub-column samples. Tests on hollow steel specimens are also included for comparison purposes. Particular focus is given to assessing the confinement effects in the infill concrete as well as their influence on the axial–bending cross-section strength interaction. The results show that whilst the capacity is reduced with the increase in the rubber replacement ratio, an enhanced confinement action is obtained for high rubber content concrete compared with conventional materials. Test measurements by means of digital image correlation techniques show that the confinement in axial compression and the neutral axis position under combined loading depend on the rubber content. Analytical procedures for determining the capacity of rubberised concrete infilled cross-sections are also considered based on the test results as well as those from a collated database and then compared with available recommendations. Rubber content-dependent modification factors are proposed to provide more realistic representations of the axial and flexural cross-section capacities. The test results and observations are used, in conjunction with a number of analytical assessments, to highlight the main parameters influencing the behaviour and to propose simplified expressions for determining the cross-section strength under combined compression and bending.

scholarly journals Certification tests of a protective device such as ROPS to ensure safe usage of tractors

2018 ◽  
Vol 224 ◽  
pp. 02061
Author(s):  
Irina Troyanovskaya ◽  
Anton Kalugin
Keyword(s):  
Strain Curve ◽  
Protective Device ◽  
Test Results ◽  
Experimental Procedure ◽  
Structure Deformation ◽  
Safety Requirements ◽  
Performance Check ◽  
Protective Structures ◽  
Full Scale Tests ◽  
Tractor Plant

According to the safety requirements, all protective devices of tractor units are subject to obligatory certification. One of the main means of protecting the operator during overturning is ROPS system. In accordance with GOST (National State Standard), a performance check of ROPS protective structures is carried out on basis of full-scale tests. The purpose of the presented study is to develop the experimental procedure and to obtain the performance check result of ROPS protective device of the tractor unit’s cabin using B10 bulldozer manufactured by the Chelyabinsk Tractor Plant as an example. The tests were carried out at the Ural Test Center NATI. For this purpose, a special bedplate was used, allowing to test the protective cabins of tractors with the total mass of up to 110 tons. The hydraulic system of the bedplate allowed to carry out the process of lateral loading of ROPS step by step, where each step corresponded to the 10 mm structure deformation. The applied load and structure deformation were recorded at each step. The energy accumulated by the structure was calculated as the area under the stress-strain curve. The energy U = 40867 J, which was required according to GOST, was accumulated during lateral deformation Δ = 270 mm. The force constituted Fy = 243 kN. After removing the lateral load, the structure was subjected to the vertical static and longitudinal loading. During the whole experiment of ROPS protective device, repairs, deformation corrections and adjustments were not allowed. The test results of ROPS structure of B10 bulldozer cabin showed compliance with the GOST safety requirements. During ROPS deformation, penetration of the protective structure elements into the driver’s limited zone was not observed.

Buckling of a Circular Cylindrical Web-Stiffened Sandwich Shell Under Axial Compression

1974 ◽  
Vol 18 (01) ◽  
pp. 55-61
Author(s):  
Vincent Volpe ◽  
Youl-Nan Chen ◽  
Joseph Kempner
Keyword(s):  
Axial Compression ◽  
Large Deflection ◽  
Single Layer ◽  
Subsequent Development ◽  
Buckling Load ◽  
Sandwich Shell ◽  
Cylindrical Sandwich Shell ◽  
Axisymmetric Mode ◽  
Shell Equations ◽  
The Mathematical Model

A stability analysis of an infinitely long web-stiffened, circular cylindrical sandwich shell under uniform axial compression is presented. The formulation begins with the establishment of a set of suitable large-deflection shell equations that forms the basis for the subsequent development of the buckling equations. The mathematical model corresponds to two face layers that are considered as thin shells and a thick core that is capable of resisting both transverse shear and circumferential extension. The associated eigenvalue problem is solved. Results show that the lowest buckling load is associated with the axisymmetric mode and is less than one half the buckling load of an equivalent single-layer shell.

scholarly journals Analysis and Calculation of Stability Coefficients of Cross-Laminated Timber Axial Compression Member

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4267
Author(s):  
Qi Ye ◽  
Yingchun Gong ◽  
Haiqing Ren ◽  
Cheng Guan ◽  
Guofang Wu ◽  
...  
Keyword(s):  
Bearing Capacity ◽  
Axial Compression ◽  
Calculation Method ◽  
National Standards ◽  
Test Results ◽  
Average Deviation ◽  
Stability Coefficient ◽  
Cross Laminated Timber ◽  
Stability Bearing Capacity ◽  
The Stability

Cross-laminated timber (CLT) elements are becoming increasingly popular in multi-storey timber-based structures, which have long been built in many different countries. Various challenges are connected with constructions of this type. One such challenge is that of stabilizing the structure against vertical loads. However, the calculations of the stability bearing capacity of the CLT members in axial compression in the structural design remains unsolved in China. This study aims to determine the stability bearing capacity of the CLT members in axial compression and to propose the calculation method of the stability coefficient. First, the stability coefficient calculation theories in different national standards were analyzed, and then the stability bearing capacity of CLT elements with four slenderness ratios was investigated. Finally, based on the stability coefficient calculation formulae in the GB 50005-2017 standard and the regression method, the calculation method of the stability coefficient for CLT elements was proposed, and the values of the material parameters were determined. The result shows that the average deviation between fitting curve and calculated results of European and American standard is 5.43% and 3.73%, respectively, and the average deviation between the fitting curve and the actual test results was 8.15%. The stability coefficients calculation formulae could be used to predict the stability coefficients of CLT specimens with different slenderness ratios well.

Ultimate Longitudinal Strength of Ship Hulls of Composite Materials

2008 ◽  
Vol 52 (03) ◽  
pp. 184-193
Author(s):  
Nian-Zhong Chen ◽  
C. Guedes Soares
Keyword(s):  
Composite Materials ◽  
Cross Section ◽  
Reaction Force ◽  
Strain Curve ◽  
Ship Hull ◽  
Stiffened Panel ◽  
Average Strain ◽  
Ship Hulls ◽  
Longitudinal Strength ◽  
Load Average

A progressive collapse analysis method is proposed to predict the ultimate longitudinal strength of ship hulls of composite materials. The load-average strain curve derived from a progressive failure nonlinear finite element analysis is adopted for representing the behavior of each stiffened composite panel forming a hull cross section. The bending moment of the ship hull under a prescribed curvature is achieved by integrating the reaction force of each stiffened panel over a hull cross section based on the load-average strain curves. The ultimate longitudinal strength of a ship hull is obtained from the moment-curvature relationship of the ship hull, which is established by imposing progressively increasing curvatures of a hull cross section. An all-composite ship is analyzed as an application.

Seismic behaviour of prestressed high-strength concrete piles under combined axial compression and cyclic horizontal loads

2018 ◽  
Vol 22 (5) ◽  
pp. 1089-1105 ◽  
Author(s):  
Xizhi Zhang ◽  
Sixin Niu ◽  
Jia-Bao Yan ◽  
Shaohua Zhang
Keyword(s):  
Finite Element ◽  
Axial Compression ◽  
High Strength Concrete ◽  
High Strength ◽  
Element Model ◽  
Test Results ◽  
Seismic Behaviour ◽  
Strength Concrete ◽  
Concrete Piles ◽  
Concrete Pile

In order to simulate the seismic behaviour of the prestressed high-strength concrete piles under working state, six full-scale prestressed high-strength concrete piles were tested under combined axial compression and cyclic horizontal loads. Different axial compression levels and prestressing levels of prestressed tendons were studied in this test programme. The failure mode, bending resistance, displacement ductility, stiffness degradation and energy dissipation of the prestressed high-strength concrete piles under different loading scenarios were measured and analysed. Test results indicated that the axial compression ratio and prestressing level of prestressed tendon significantly influenced the seismic performance of prestressed high-strength concrete piles. Theoretical models were developed to predict cracking, yielding and ultimate bending resistances of the prestressed high-strength concrete pile under combined compression and bending. Finite element model was also developed to simulate the ultimate strength behaviour of the prestressed high-strength concrete pile under combined compression and flexural bending. The accuracies of the theoretical and finite element model were checked through validations of their predictions against the reported test results.

Post-buckling Behavior of Stiffened Cross-Ply Cylindrical Shells

1994 ◽  
Vol 61 (4) ◽  
pp. 998-1000 ◽  
Author(s):  
M. Savoia ◽  
J. N. Reddy
Keyword(s):  
Axial Compression ◽  
Carrying Capacity ◽  
Shell Theory ◽  
Load Carrying Capacity ◽  
Imperfection Sensitivity ◽  
Buckling Modes ◽  
Geometric Imperfection ◽  
Buckling Behavior ◽  
Load Carrying ◽  
Post Buckling

The post-buckling of stiffened, cross-ply laminated, circular determine the effects of shell lamination scheme and stiffeners on the reduced load-carrying capacity. The effect of geometric imperfection is also included. The analysis is based on the layerwise shell theory of Reddy, and the “smeared stiffener” technique is used to account for the stiffener stiffness. Nu cylinders under uniform axial compression is investigated to merical results for stiffened and unstiffened cylinders are presented, showing that imperfection-sensitivity is strictly related to the number of nearly simultaneous buckling modes.

Mechanical Properties of Large Scale Confined Concrete

2011 ◽  
Vol 94-96 ◽  
pp. 1983-1988
Author(s):  
Jia Song ◽  
Zhen Bao Li ◽  
Yong Ping Xie ◽  
Xiu Li Du ◽  
Yue Gao
Keyword(s):  
Mechanical Properties ◽  
Experimental Study ◽  
Axial Compression ◽  
Large Scale ◽  
Plain Concrete ◽  
Concrete Columns ◽  
Confined Concrete ◽  
Transverse Reinforcement ◽  
Test Results ◽  
Reinforcement Configuration

An experimental study was made of the mechanical properties of large scale confined concrete subjected to the axial compression test. Eleven tied concrete columns and six plain concrete prisms were tested. In the test, each specimen had the same transverse reinforcement configuration, and similar volumetric ratio of lateral steel, while different size. The test results in this paper indicate that the size of the specimen has no obvious relationship with the ultimate strength, however, it does affect the post-peak ductility to some extent. As a supplement to the experimental study, a finite element method was adopted to imitate the mechanical behavior of the confined concrete under axial compression. The results of the imitation in this paper indicate the confinement mechanism of large scale specimens.

An Experimental Study on the Creep of FRC Sub-Base for Pavement Using a New Testing Device

2013 ◽  
Vol 639-640 ◽  
pp. 493-497
Author(s):  
Woo Tai Jung ◽  
Sung Yong Choi ◽  
Young Hwan Park
Keyword(s):  
Creep Test ◽  
Strain Curve ◽  
Hydraulic Pressure ◽  
Slight Variation ◽  
Test Results ◽  
Creep Tests ◽  
Loading Device ◽  
Permanent Load ◽  
Term Creep

The hydraulic loading device commonly used for creep test necessitates continuous recharge of the hydraulic pressure with time and is accompanied by slight variation of the permanent load at each recharge. Therefore, accurate test results cannot be obtained for long-term creep tests requiring time-dependent behavioral analysis during more than 6 months. This study conducts creep test as part of the analysis of the long-term characteristics of fiber-reinforced lean concrete sub-base of pavement. The creep test is executed using the new load-amplifier device not a conventional loading device. Since the results of the preliminary verification test on the new creep test device show that constant permanent load is applied without significant variation, it can be expected that more accurate measurement of the creep will be possible in a long-term compared to the conventional hydraulic device. In addition, the creep test results of sub-base specimens reveal the occurrence of large instantaneous elastic strain, differently from the strain curve observed in ordinary concrete, as well as the occurrence of small creep strain leading to low creep coefficient.

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