A Simplified Approach to Creep Buckling of Structures Under Varying Loads

1980 ◽  
Vol 102 (3) ◽  
pp. 303-308 ◽  
Author(s):  
J. M. Chern
Keyword(s):  
Axial Compression ◽  
Constant Temperature ◽  
Critical Strain ◽  
Experimental Results ◽  
Test Results ◽  
Numerical Examples ◽  
Simplified Approach ◽  
Special Cases ◽  
Creep Buckling ◽  
Life Fraction

A critical strain approach to the prediction of creep buckling time in structures under varying loads is investigated and its relationship with the conventional linear cumulative damage (life-fraction) approach is established under condition of constant temperature. The latter approach is shown to be inconsistent in some special cases and may result in overprediction or underprediction of creep buckling time depending on whether the loads are monotonically increasing or decreasing. Numerical results obtained with the present approach are compared with incremental solutions for columns, and with recently available theoretical and experimental results of cylindrical shells under axial compression. These comparisons indicate that the critical strain approach is suitable for use in design analysis. Further investigations are needed to assess the effect of varying temperature, which is excluded in the numerical examples because no test results are available for comparison.

Behavior of CFRP-confined reactive powder concrete-filled steel tubes under axial compression

2020 ◽  
pp. 136943322097478
Author(s):  
Song Li ◽  
Chu-Jie Jiao
Keyword(s):  
Bearing Capacity ◽  
Axial Compression ◽  
Local Buckling ◽  
Steel Tube ◽  
Experimental Results ◽  
Reactive Powder Concrete ◽  
Test Results ◽  
Steel Tubes ◽  
Reactive Powder ◽  
Concrete Filled Steel Tubes

Reactive powder concrete-filled steel tubes (RPCFSTs) have become an important research target in recent years. In engineering applications, RPCFSTs can provide superior vertical components for high-rise and tower buildings, thereby enabling developers to provide more floor space. However, this type of composite structure is prone to inelastic outward local buckling. The use of carbon fiber reinforced polymer (CFRP) wrapping to suppress such local buckling has shown great potential in limited test results. This paper presents experimental results concerning the axial compression of CFRP-confined reactive powder concrete-filled circular steel tubes (CF-RPCFSTs). We included 18 specimens in our experimental investigation, varying the number of CFRP layers, steel tube thickness, and RPC strength. According to our test results, CF-RPCFSTs exhibit compression shear failure and drum-shaped failure. The CFRP wrap can effectively enhance bearing capacity and postpone local buckling of the steel tube. In addition, three-layer CFRP-confined RPC-filled thin-wall steel tubes are suitable for engineering. We also propose a model to calculate the bearing capacity of CF-RPCFSTs. Compared to the existing model of CFRP-confined concrete-filled steel tubes, the results obtained using the proposed model are in good agreement with our experimental results.

Compiler-Aided Run-Time Performance Speed-Up in Super-Scalar Processor

10.28945/3391 ◽  
2009 ◽  
Author(s):  
Moshe Pelleh
Keyword(s):  
Embedded Systems ◽  
Embedded System ◽  
General Purpose ◽  
Experimental Results ◽  
Medium Size ◽  
Organic System ◽  
Software Application ◽  
Organic Systems ◽  
Special Cases ◽  
Run Time

In our world, where most systems become embedded systems, the approach of designing embedded systems is still frequently similar to the approach of designing organic systems (or not embedded systems). An organic system, like a personal computer or a work station, must be able to run any task submitted to it at any time (with certain constrains depending on the machine). Consequently, it must have a sophisticated general purpose Operating System (OS) to schedule, dispatch, maintain and monitor the tasks and assist them in special cases (particularly communication and synchronization between them and with external devices). These OSs require an overhead on the memory, on the cache and on the run time. Moreover, generally they are task oriented rather than machine oriented; therefore the processor's throughput is penalized. On the other hand, an embedded system, like an Anti-lock Braking System (ABS), executes always the same software application. Frequently it is a small or medium size system, or made up of several such systems. Many small or medium size embedded systems, with limited number of tasks, can be scheduled by our proposed hardware architecture, based on the Motorola 500MHz MPC7410 processor, enhancing its throughput and avoiding the software OS overhead, complexity, maintenance and price. Encouraged by our experimental results, we shall develop a compiler to assist our method. In the meantime we will present here our proposal and the experimental results.

Exergy-Based Ecological Optimization of an Irreversible Quantum Carnot Heat Pump with Spin-1/2 Systems

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Xiaowei Liu ◽  
Lingen Chen ◽  
Yanlin Ge ◽  
Huijun Feng ◽  
Feng Wu ◽  
...  
Keyword(s):  
Heat Pump ◽  
Performance Comparison ◽  
Ecological Function ◽  
Performance Characteristics ◽  
Numerical Examples ◽  
Ecological Performance ◽  
Special Cases ◽  
Heating Load ◽  
Ecological Optimization

AbstractBased on an irreversible quantum Carnot heat pump model in which spin-1/2 systems are used as working substance, an exergy-based ecological function and some other important parameters of the model heat pump are derived. Numerical examples are provided to investigate its ecological performance characteristics. The influences of various irreversibility factors on the ecological performance are discussed. Performance comparison and discussion among maximum points of ecological function, heating load, and so on, are conducted. At last, three special cases are discussed.

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 When to Substitute a Missing Upper Lateral With a Canine: A Simplified Approach

2021 ◽  
pp. 030157422098054
Author(s):  
Renu Datta
Keyword(s):  
Anterior Segment ◽  
Specific Treatment ◽  
Simplified Approach ◽  
Special Cases ◽  
Randomized Control ◽  
The One ◽  
Individual Presentation ◽  
Available Information ◽  
Missing Tooth ◽  
Made In

Introduction: The upper lateral incisor is the most commonly missing tooth in the anterior segment. It leads to esthetic and functional imbalance for the patients. The ideal solution is the one that is most conservative and which fulfills the functional and esthetic needs of the concerned individual. Canine substitution is evolving to be the treatment of choice in most of the cases, because of its various advantages. These are special cases that need more time and effort from the clinicians due to space discrepancy in the upper and lower arches, along with the presentation of individual malocclusion. Aims and Objectives: Malocclusion occurring due to missing laterals is more complex, needing more time and effort from the clinicians because of space discrepancy, esthetic compromise, and individual presentation of the malocclusion. An attempt has been made in this article to review, evaluate, and tabulate the important factors for the convenience of clinicians. Method: All articles related to canine substitution were searched in the electronic database PubMed, and the important factors influencing the decision were reviewed. After careful evaluation, the checklist was evolved. Result: The malocclusions in which canine substitution is the treatment of choice are indicated in the tabular form for the convenience of clinicians. Specific treatment-planning considerations and biomechanics that can lead to an efficient and long-lasting result are also discussed. Conclusion: The need of the hour is an evidence-based approach, along with a well-designed prospective randomized control trial to understand the importance of each factor influencing these cases. Until that time, giving the available information in a simplified way can be a quality approach to these cases.

RELIABILITY ASSESSMENT OF AXIALLY COMPRESSED COMPOSITE CYLINDRICAL SHELLS WITH RANDOM IMPERFECTIONS

2011 ◽  
Vol 11 (02) ◽  
pp. 215-236 ◽  
Author(s):  
MATTEO BROGGI ◽  
ADRIANO CALVI ◽  
GERHART I. SCHUËLLER
Keyword(s):  
Mathematical Models ◽  
Axial Compression ◽  
Cylindrical Shells ◽  
Reliability Assessment ◽  
Buckling Analysis ◽  
Buckling Load ◽  
Experimental Results ◽  
Drastic Decrease ◽  
Different Types ◽  
Probability And Statistics

Cylindrical shells under axial compression are susceptible to buckling and hence require the development of enhanced underlying mathematical models in order to accurately predict the buckling load. Imperfections of the geometry of the cylinders may cause a drastic decrease of the buckling load and give rise to the need of advanced techniques in order to consider these imperfections in a buckling analysis. A deterministic buckling analysis is based on the use of the so-called knockdown factors, which specifies the reduction of the buckling load of the perfect shell in order to account for the inherent uncertainties in the geometry. In this paper, it is shown that these knockdown factors are overly conservative and that the fields of probability and statistics provide a mathematical vehicle for realistically modeling the imperfections. Furthermore, the influence of different types of imperfection on the buckling load are examined and validated with experimental results.

Dynamical theory of neutron diffraction

1978 ◽  
Vol 56 (10) ◽  
pp. 1261-1288 ◽  
Author(s):  
V. F. Sears
Keyword(s):  
Neutron Diffraction ◽  
Theoretical Basis ◽  
Dynamical Theory ◽  
Experimental Results ◽  
Neutron Interferometry ◽  
New Techniques ◽  
The Past ◽  
Neutron Optics ◽  
Coherent Wave ◽  
Special Cases

We present a review of the dynamical theory of neutron diffraction by macroscopic bodies which provides the theoretical basis for the study of neutron optics. We consider both the theory of dispersion, in which it is shown that the coherent wave in the medium satisfies a macroscopic one-body Schrödinger equation, and the theory of reflection, refraction, and diffraction in which the above equation is solved for a number of special cases of interest. The theory is illustrated with the help of experimental results obtained over the past 10 years by a number of new techniques such as neutron gravity refractometry, Pendellösung interference, and neutron interferometry.

Line Contact Deformation: A Cylinder Between Two Flat Plates

1981 ◽  
Vol 103 (1) ◽  
pp. 21-25 ◽  
Author(s):  
M. R. Hoeprich ◽  
H. Zantopulos
Keyword(s):  
Plane Strain ◽  
General Equation ◽  
Roller Bearing ◽  
Experimental Results ◽  
Line Contact ◽  
Contact Deformation ◽  
Flat Plates ◽  
Special Cases ◽  
Analytical Work

Various line contact deformation equations used in roller bearing technology are analyzed. Many of these deformation equations, primarily involving plane strain, are shown to be special cases of a general equation derived in this paper. Experimental results are also presented to support the results of the analytical work.

Experimental Study and Finite Analysis on Flexural Capacity of Laminated Glass

2011 ◽  
Vol 243-249 ◽  
pp. 258-262
Author(s):  
Jun Chen ◽  
Jia Lv ◽  
Qi Lin Zhang ◽  
Zhi Xiong Tao ◽  
Jun Chen
Keyword(s):  
Experimental Results ◽  
Laminated Glass ◽  
Test Results ◽  
Design Code ◽  
Flexural Capacity ◽  
Equivalent Thickness ◽  
High Rise ◽  
Safety Glass ◽  
Current Design ◽  
Good Agreement

Laminated glass has been increasing widely used in high rise buildings as a kind of safety glass in recent years. So we should analyze its material property. In this paper, we use flexural experiments and ANSYS program to analyze the main factors that affect the flexural capacity of the laminated glass. The test results show that the flexural capacity is closely related to film. And the ANSYS program had got good agreement with the experimental results. Comparison of experimental results with calculated ones indicates that the current design code will lead to conservative results and the equivalent thickness of laminated glasses provided in the code should be further discussed.

scholarly journals Edge detection with trigonometric polynomial shearlets

2021 ◽  
Vol 47 (1) ◽  
Author(s):  
Kevin Schober ◽  
Jürgen Prestin ◽  
Serhii A. Stasyuk
Keyword(s):  
Edge Detection ◽  
Trigonometric Polynomial ◽  
Two Dimensions ◽  
Characteristic Functions ◽  
Numerical Examples ◽  
Special Cases ◽  
Periodic Characteristic ◽  
Boundary Curves ◽  
Theoretical Results ◽  
De La Vallée Poussin

AbstractIn this paper, we show that certain trigonometric polynomial shearlets which are special cases of directional de la Vallée Poussin-type wavelets are able to detect step discontinuities along boundary curves of periodic characteristic functions. Motivated by recent results for discrete shearlets in two dimensions, we provide lower and upper estimates for the magnitude of the corresponding inner products. In the proof, we use localization properties of trigonometric polynomial shearlets in the time and frequency domain and, among other things, bounds for certain Fresnel integrals. Moreover, we give numerical examples which underline the theoretical results.

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