• Magazine of the Korea Concrete Institute
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• v.9 no.4
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• pp.207-214
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• 1997

This study was performed to verify the effect of axial force due to restraint on the mechanical behavior and the average crack spacing of the reinforced concrett. ilexural menlbers. For. this purpose, the flexural sttvngt.h and rigidity werc experimentally investigated undcl. axially rcstmined and unr.est.rainrd conditions. Furthermore , the average crack spacing was also checkcd for the axilly restrained contlit.ion. Thc test results showd that the flexual strength and rigidity of t,he restrained beam were higher. than those of the unrestrained beam. The major. factors affecting on the average crack spacing were steeel stress, axial force, cicumference of reinforcing bar and effective tension arm of concrete. However. the concrete compressive strength was minor effect. Including thesc factors, a prediction equation for the average crack spacing of the restrained member was proposed.

• Structural Engineering and Mechanics
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• v.44 no.4
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• pp.521-538
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• 2012

In this study, the transverse vibrations of an axially moving flexible beams resting on multiple supports are investigated. The time-dependent velocity is assumed to vary harmonically about a constant mean velocity. Simple-simple, fixed-fixed, simple-simple-simple and fixed-simple-fixed boundary conditions are considered. The equation of motion becomes independent from geometry and material properties and boundary conditions, since equation is expressed in terms of dimensionless quantities. Then the equation is obtained by assuming small flexural rigidity. For this case, the fourth order spatial derivative multiplies a small parameter; the mathematical model converts to a boundary layer type of problem. Perturbation techniques (The Method of Multiple Scales and The Method of Matched Asymptotic Expansions) are applied to the equation of motion to obtain approximate analytical solutions. Outer expansion solution is obtained by using MMS (The Method of Multiple Scales) and it is observed that this solution does not satisfy the boundary conditions for moment and incline. In order to eliminate this problem, inner solutions are obtained by employing a second expansion near the both ends of the flexible beam. Then the outer and the inner expansion solutions are combined to obtain composite solution which approximately satisfying all the boundary conditions. Effects of axial speed and flexural rigidity on first and second natural frequency of system are investigated. And obtained results are compared with older studies.

• Journal of Korean Society of Steel Construction
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• v.17 no.2 s.75
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• pp.161-171
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• 2005

When the in-plane flexural rigidity is small in relation to the applied load, the arch ribs may buckle to the in-plane direction. Designers should therefore determine the in-plane buckling strength. To determine the buckling strength of arch ribs, designers have to consider the material nonlinear response. But in the case of arch ribs having large slenderness ratio, arch ribs may buckle in the elastic range, and when the arch ribs have low slenderness ratio, elastic buckling strength is useful in the preliminary design. In this paper, elastic buckling strength of arch ribs, which are frequently used in practical design, is studied using nonlinear finite element method. In general, the relation between flexural rigidity and elastic buckling strength is linear. As seen from the results, however, when the arch ribs have low slenderness ratio, the relation between flexural rigidity and elastic buckling strength is nonlinear.

• Magazine of the Korea Concrete Institute
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• v.11 no.1
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• pp.243-254
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• 1999

This paper presents a numerical study for developing the moment magnifier method that is applicable to RC flat plates subject to combined axial compressive and floor load. For the nonlinear finite element analysis, a computer program addressing material and geometric nonlinearities was developed. The flat plates to be studied are designed in accordance with the Direct Design Method in Korean Building Code for Structural Concrete. This paper proposes the buckling force and the moment magnification factor for the flat plate under the governing load condition that is the combined vertical and subsequently applied uniaxial compressive load. The buckling force is defined with two ingredients: the buckling coefficient and the effective flexural rigidity. Parametric studies are performed to investigate variations of the buckling coefficient and the effective flexural rigidity. Based on the numerical results, this paper provides the design values of the buckling coefficient and the effective flexural rigidity, and the design procedure for the moment magnifier method.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.287-294
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• 2000

Calculation of the flexural rigidity value (EI) is indispensable for prescription of deflection characteristics of crop stalks in harvesting□Conventionally□EI has been determined by either average EI of the whole stalk or average EI of each stems divided into node through the calculation method of cantilever with homogeneous section□However□deflection characteristics of crop stalks caused by mechanical operation such as combine harvester were not exactly presumed by these conventional EI through the experiment by authors. Further, actual EI of a stalk changes in company with a change of moisture contents as time passes during the experiment. Finally, efficient calculation method for determining EI is needed in order to improve these problems. In this study, mechanical model based on actual structure of the crop stalk with variety sectional area was proposed. This mechanical model is calculated by the theory of cantilever with continuous stages. Therefore, improvement of both calculating accuracy on EI and efficiency of measuring system was tried. At first, this calculation method was applied to piano wire of which EI was recognized in advance. As a result, EI calculated from this new method coincided approximately with piano wire's EI. Next, applying to crop stalks as same as piano wire, relationship between loads acting on crop stalks and deflection values calculated by EI using this new calculation method was exactly presumed in comparison with conventional method. Further, measuring time of deflection test was greatly reduced. Finally, new calculation method of EI will be available for estimating mechanical characteristics of so many kinds of crop stalks in harvesting operation. Further, in this study, new deflection test using image-processing apparatus by computer will be introduced.

• Smart Structures and Systems
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• v.11 no.4
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• pp.411-433
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• 2013

Due to its easy operation and wide applicability, the ambient vibration method is commonly adopted to determine the cable force by first identifying the cable frequencies from the vibration signals. With given vibration length and flexural rigidity, an analytical or empirical formula is then used with these cable frequencies to calculate the cable force. It is, however, usually difficult to decide the two required parameters, especially the vibration length due to uncertain boundary constraints. To tackle this problem, a new concept of combining the modal frequencies and mode shape ratios is fully explored in this study for developing an accurate method merely based on ambient vibration measurements. A simply supported beam model with an axial tension is adopted and the effective vibration length of cable is then independently determined based on the mode shape ratios identified from the synchronized measurements. With the effective vibration length obtained and the identified modal frequencies, the cable force and flexural rigidity can then be solved using simple linear regression techniques. The feasibility and accuracy of the proposed method is extensively verified with demonstrative numerical examples and actual applications to different cable-stayed bridges. Furthermore, several important issues in engineering practice such as the number of sensors and selection of modes are also thoroughly investigated.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.786-793
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• 2006

For the purpose of developing a vibration-based tension force evaluation procedure for hangers in suspension bridges, a 3D finite element model of hangers is constructed in this paper. With the developed finite element formulation, a frequency-based sensitivity-updating algorithm is applied to identify the target cable system the proposed method is also able to identify the flexural rigidity. the axial rigidity, and the torsion rigidity of a cable. For a field application, a vibration test on hangers of the Yong Jong Grand Suspension Bridge is carried out and the collected data is used to verify the proposed method.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.161-164
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• 2005

The flexural behavior of a strengthened beam, that is a reinforced. concrete beam with externally bonded fiber sheets, was theoretically and experimentally investigated. The effects of the amount of glass fiber sheets varying from 1 to 4 plies on the flexural capacity of the strengthened beam are also examined. The flexural rigidity of the strengthened beam was enhanced compared with RC beam. In addition, the failure mode and load-deflection relationship for the strengthened beam and the comparison of analysis with experiment are extensive investigated. Finally, the determination of the nominal moment capacity $M_n$ of the strengthened beam will be discussed

• Journal of applied mathematics & informatics
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• v.20 no.1_2
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• pp.17-34
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• 2006

Inverse coefficient identification problems associated with the fourth-order Sturm-Liouville operator in the steady state Euler-Bernoulli beam equation are investigated. Unlike previous studies in which spectral data are used as additional information, in this paper only boundary information is used, hence non-destructive tests can be employed in practical applications.

• Steel and Composite Structures
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• v.34 no.2
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• pp.171-188
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• 2020

The past research on cold-formed steel (CFS) flexural members have proved that rectangular hollow flanged sections perform better than conventional I-sections due to their higher torsional rigidity over the later ones. However, CFS members are vulnerable to local buckling, substantially due to their thin-walled features. The use of packing, such as firmly connected timber planks, to the flanges of conventional CFS lipped I-sections can drastically improve their flexural performance as well as structural efficiency. Whilst several CFS composites have been developed so far, only limited packing materials have been tried. This paper presents a series of tests carried out on different rectangular hollow compression flanged sections with innovative packing materials. Four-point flexural tests were carried out to assess the flexural capacity, failure modes and deformed shapes of the CFS composite beam specimens. The geometric imperfections were measured and reported. The North American Specifications and Indian Standard for cold-formed steel structures were used to compare the design strengths of the experimental specimen. The test results indicate clearly that CFS rectangular 'compression' flanged composite beams perform significantly better than the conventional rectangular hollow flanged CFS sections.