scholarly journals Revisited the Critical Load Assessment of Huang et al. on Willems Tested Beck Column

2021 ◽  
Vol 29 (1) ◽  

Dynamic stability of elastic structures is a fascinating topic. Many researchers have examined the problem theoretically considering a cantilever column under a tip-concentrated tangential load, the so-called Beck column. Experimental verification is demanded since the critical load of Beck column is found to be approximately eight times to that of the classical Euler column. Different types of testing procedures are being adopted to create the follower force. Among them, notable Willems experimentation provides the critical load close to that of Beck column. Investigations made by other researchers indicate the controversy associated with modeling and testing of Willems on Beck column. Such an intriguing problem of structures loaded by non-conservative forces is revisited here through a simple mathematical formulation. This paper confirms the adequacy of Willems approach on Beck column and the wrong critical load assessment of others. It indicates the possibility on the practical realization of follower forces

2022 ◽  
Vol 30 (1) ◽  
pp. 801-811
Author(s):  
Jakkana Peter Praveen ◽  
Boggarapu Nageswara Rao

Dynamic instability is an interesting topic in the mechanics of elastic structures. Though the subject has been formed by many analytical, numerical, and experimental investigations, it has many issues, as evidenced from the critical overview of Elishakoff. Furthermore, the controversial articles of Koiter and Sugiyama on unrealistic and realistic follower forces demand experimental verification. Mullagulov has proposed a device for creating the follower forces and tested steel rods under compression. This paper highlights the experimentation of Mullagulov and his observations briefly to examine the influence of material properties on the stability load estimations and to confirm the practical realization of follower forces.


AIAA Journal ◽  
2000 ◽  
Vol 38 ◽  
pp. 1070-1077
Author(s):  
Si-Hyoung Park ◽  
Ji-Hwan Kim

2021 ◽  
Vol 25 (1) ◽  
Author(s):  
Kelsey Morgan ◽  
Erin Adams ◽  
Teresa Mary Elsobky ◽  
Marcia Brackbill ◽  
Amber Darr

The COVID-19 pandemic required academic institutions to quickly transition to online learning and make changes to assessment procedures. This study examines how a school of pharmacy creatively approached the challenge of online assessment while maintaining the standards necessary to prepare practice-ready student pharmacists. To conduct traditional exams, instructors deployed two different types of methods utilizing testing software: a video conferencing technology approach which mimicked pre-pandemic, on-campus proctored exams; or open-book, internet access-enabled exams that ensured academic integrity and rigor through various testing strategies. To assess students’ clinical skills, faculty used a combination of techniques such as physical examinations, patient interviews, and patient presentations. To understand the student experience with these assessments, students were surveyed using a 12-item questionnaire. Overall, online video proctoring maintained consistency in exam structure and administration, but required extensive instruction for both students and proctors. Students preferred unproctored, open-book, internet access-enabled, standard time exams versus proctored, closed-book, internet-access disabled, extended time exams. Changes to testing procedures, whether with proctored or unproctored methods, appeared to increase student stress.


2019 ◽  
Vol 102 ◽  
pp. 03006
Author(s):  
Oksana A. Grebneva

Both in Russia and abroad, there are works that are devoted to the problem of optimal placement of measuring devices, which are evidenced by the current literature. The proposed methods are not universal, that does not allow them to be directly used for different types of pipeline systems. In addition, the developed algorithms does not guarantee a global solution. In this regard, there is a demand for solving the problem of optimal placement of measuring devices for pipeline systems. At the same time, not only the number and accuracy of measuring devices, but also their composition and placement locations are important. In this paper, a mathematical formulation of the problem of optimal placement of measuring devices is given, methods for its solution are proposed. The numerical example shows the effectiveness of the proposed method of optimal placement of measuring devices, which allows to get a global solution for a previously known finite number of steps.


Author(s):  
D. S. Yang ◽  
C. M. Wang ◽  
J. D. Yau

This paper is concerned with the dynamic stability and response of an inclined Euler–Bernoulli beam under a moving mass and a moving follower force. The extended Hamilton’s principle is used to derive the governing equation of motion and the boundary conditions for this general moving load/force problem. Considering a simply supported beam, one can solve the problem analytically by approximating the spatial part of the deflection with a Fourier sine series. Based on the formulation and method of solution, sample dynamic responses are determined for a beam that is inclined at 30[Formula: see text] with respect to the horizontal. It is shown that the dynamic response of the beam under a moving mass is rather different from an equivalent moving follower force. Also investigated herein are the dynamic stability of inclined beams under moving load/follower force which are described by four key variables, viz. the speed of the moving mass/follower force, concentrated mass to the beam distributed mass, vibration frequency and the magnitude of the moving mass/follower force. The critical axial load and the critical follower force are different when they are located at different positions in the beam; except for the special case when they are at the end of the beam.


1990 ◽  
Vol 17 (3) ◽  
pp. 277-286 ◽  
Author(s):  
G. M. L. Gladwell

This paper provides an historical account of Leipholz's research into elastic stability. Emphasis is placed on divergence and flutter instability of follower force systems, the derivation of lower bounds for the critical load for divergence, and estimates for critical loads for flutter. Key words: elastic stability, divergence, flutter, lower bounds, nonconservative systems, symmetrisable matrix.


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