• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.09a
• /
• pp.1190-1200
• /
• 2010

A method was developed to determine resilient modulus for crushed rock-soil mixtures whose usage has been increased recently without engineering specifications. The method is based on the subtle different modulus called nonlinear dynamic modulus and was lately implemented in residual soils and engineered crushed-stones. Hereby. the same method was expanded to crushed rock-soil mixtures containing as large grain diameter as 300mm. The method utilize field direct-arival tests for the determination of maximum Young's modulus, and a large scale free-free resonant column test, which is recently developed to is capable to test as large grain diameter as 25mm, for modulus reduction curves. The prediction model of resilient modulus was evaluated for crushed rock-soil mixtures of a highway construction site at Gimcheon, Korea.

• Tunnel and Underground Space
• /
• v.21 no.6
• /
• pp.480-493
• /
• 2011

Dynamic rock property is one of most important parameters in design of earthquake-resistant structures. In this study, free-free resonant column test has been conducted to obtain dynamic Young's modulus, dynamic shear modulus, and damping ratio among dynamic properties with granite specimen of Chungnam Yeongi area. The dynamic properties obtained from this test were compared with the physical properties from static rock tests, and their relationship has been analyzed. From our study, it has been concluded that the dynamic Young's modulus and the dynamic shear modulus are linearly proportional to the elastic wave velocity. And also the damping ratio has been identified to be in non-linear inverse proportion to the elastic wave velocity.

• Journal of the Korean Chemical Society
• /
• v.31 no.3
• /
• pp.244-249
• /
• 1987

Liquid-solid extraction technique was applied to enrich volatile free acids (VFAs) from aqueous matrices. Chromosorb P was found to be an efficient solid sorbent. The unionized VFAs could be quantitatively recovered from the Chromosorb P column with ether while interfering watermiscible components were retained in the adsorbed water on the surface of Chromosorb P. The method of simple and efficient isolation-enrichment of VFAs, followed by the quantitative analysis employing stainless steel capillary column coated with Carbowax 20M containing phosphoric acid has been applied to the determination of VFAs in several aqueous samples.

• Steel and Composite Structures
• /
• v.35 no.2
• /
• pp.295-306
• /
• 2020

This paper deals with free vibration analysis of non-uniform column resting on elastic foundations and subjected to follower force at its free end. The internal pores and graphene platelets (GPLs) are distributed in the matrix according to different patterns. The model is proposed with material parameters varying in the thickness of column to achieve graded distributions in both porosity and nanofillers. The elastic modulus of the nanocomposite is obtained by using Halpin-Tsai micromechanics model. The differential quadrature method as an efficient and accurate numerical approach is used to discretize the governing equations and to implement the boundary conditions. It is observed that the maximum vibration frequency obtained in the case of symmetric porosity and GPL distribution, while the minimum vibration frequency is obtained using uniform porosity distribution. Results show that for better understanding of mechanical behavior of nanocomposite column, it is crucial to consider porosities inside the material structure.

• Structural Engineering and Mechanics
• /
• v.73 no.1
• /
• pp.83-95
• /
• 2020

In this work, a mathematical model of beam-column system carrying a double eccentric end mass system is investigated, and solved analytically based on the exact solution analysis. The model considers the case in which the double eccentric end mass is a rigid storage tank containing fluid. Both Timoshenko and Bernoulli-Euler beam bending theories are considered. Equation of motion, general solution and boundary conditions for the present system model are developed and presented in dimensional and non-dimensional format. Several important non-dimensional design parameters are introduced. Symbolic and/or explicit formulae of the frequency and mode shape equations are formulated. To the authors knowledge, the present reduced closed form symbolic and explicit frequency equations have not appeared in literature. For different applications, the results are validated using commercial finite element package, namely ANSYS. The beam-column system investigated in this paper is significant for many engineering applications, especially, in mechanical and structural systems.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1996.10a
• /
• pp.3-10
• /
• 1996

Numerical methods are developed for solving the buckling loads and the elastica of clamped- free columns of circular cross-section with constant volume. The column model is based rut the Timoshenko beam theory. The Runge-Kutta and Regula-Falsi methods, respectively, are used to solve the governing differential equations and to compute the eigenvalues. Extensive numerical results, including buckling loads, elastica of buckled shapes and effects of shear de-formation, are presented in non-dimensional form for elastic columns whose radius of circular cross-section varies both linearly and parabolically with column length.

• Journal of Mechanical Science and Technology
• /
• v.18 no.12
• /
• pp.2225-2235
• /
• 2004

An observatory termed 'Steel Swing' has been developed, where a 15000 kg pendulum is hanged from a stiff steel frame. A building element can be tested after inserted between the pendulum and the frame. Free vibration, forced vibration tests and earthquake monitoring were performed on an exposed-type steel column base. The response records monitored during natural earthquakes were used to identify the vibration property of the specimen. Identified system gain was approximated by a theoretical gain of linear SDOF system, and the response calculated based on such a linear system agrees with the monitored response fairly well. This research technique can be applied to check the behaviors of new materials and new details of connections and the safety of non-structural elements as well.

• Korean Journal of Food Science and Technology
• /
• v.19 no.5
• /
• pp.392-396
• /
• 1987

A method for isolation of some phenolic acids from Korean ginseng(Panax ginseng C.A.Meyer)was studied using silicic acid column chromatography. preparative thin layer chromatography and high performance liquid chromatography. Two phenolic compounds were isolated and identified as ferulic acid, mp $156-157^{\circ}C$ and vanillic acid. mp $154-156^{\circ}C$ by spectral data of Mass and NMR spectroscopy.

• Steel and Composite Structures
• /
• v.6 no.3
• /
• pp.221-236
• /
• 2006

The objective of this work is to describe the main steps involved in the derivation of a GBT (Generalised Beam Theory) formulation to analyse the vibration behaviour of loaded cold-formed steel members and also to illustrate the application and capabilities of this formulation. In particular, the paper presents and discusses the results of a detailed investigation about the local and global free vibration behaviour of lipped channel simply supported columns. After reporting some relevant earlier GBT-based results dealing with the buckling and vibration behaviours of columns and load-free members, the paper addresses mostly issues concerning the variation of the column fundamental frequency and vibration mode nature/shape with its length and axial compression level. For validation purposes, some GBT-based results are also compared with values obtained by means of 4-node shell finite element analyses performed in the code ABAQUS.

• International Journal of High-Rise Buildings
• /
• v.9 no.4
• /
• pp.377-386
• /
• 2020

Beginning a few decades ago, Baku, the capital city of Azerbaijan, has experienced a dramatic construction boom that is revitalizing its skyline. The expansive growth looks to uphold the historic past of Baku as a focal point within the Caspian Sea Region while also evoking aspirations for a city of the future. With superstructure complete and interiors progressing, the Ministry of Taxation (MOT) tower is the latest addition to the city, with its stacked cubes twisting above a multi-level podium at the base. Each cube is separated by column-free green roof terraces, creating unique parametric reveals of the developing surroundings. Aside from MOT's stunning shape, its geolocation resulted in unusually high wind loads coupled with high seismic hazards for a tower of its height. In addition, limitations on possible structural systems required stepping away from a typical prescriptive code-based approach into one that utilized Performance-Based Design (PBD) methods. This paper presents the numerous structural challenges and innovations that allowed the design of a new icon to be realized.