• Journal of the Korean Statistical Society
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• v.34 no.2
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• pp.153-160
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• 2005

In this paper, modified second order slope rotatable designs are introduced and modified slope rotatable central composite designs (SRCCD) are constructed for $2 {\le} v {\le} 17$ (v: the number of factors). Further, it can be shown for certain values of 'v', the modified SRCCD can be viewed as SRCCD constructed as with the technique of augmentation of second order rotatable design (SORD) using central composite design to SRCCD. These designs are useful in parts to estimate responses and slopes with spherical variance functions.

• The Korean Journal of Applied Statistics
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• v.32 no.6
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• pp.867-878
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• 2019

In this paper, we applied modified slope rotatability introduced by Victorbabu (2005) to the central composite design of second type, and studied related content. We suggested methods of constructing central composite designs of second type which have modified slope rotatability. Especially, this property has the advantage that it can be used to sequential experiments, because we can obtain central composite designs of second type which have modified slope rotatability by adding experimental points without changing the axial values to central composite designs of second type having Box-Hunter rotatability. We explained central composite designs of second type which have modified slope rotatability by using two examples.

• Carbon letters
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• v.10 no.2
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• pp.97-100
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• 2009

In this work, effects of carbon matrix on sliding friction and wear behavior of four kinds of C/C have been investigated against 40 Cr steel ring mate. Composite A with rough lamination carbon matrix (RL) shows the highest volume loss and coefficient of friction, while composite D with smooth lamination/resin carbon matrix (SL/RC) shows the lowest volume loss. The worn surface of composite A appears smooth, whereas that of composite C with smooth lamination carbon (SL) appears rough. The worn surface of composite D appears smooth under low load but rough under high load. Atomic force microscope images show that the size of wear particles on the worn surface is also dependent on the carbon matrix.

• Steel and Composite Structures
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• v.47 no.2
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• pp.203-216
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• 2023

The composite beam connections often encountered fracture failure in the welded bottom flange joint, and a bottom flange bolted connection has been proposed to increase the deformation ability of the bottom flange joint. The seismic performance of the bottom flange bolted composite beam connection was suffered from both the composite action of concrete slab and the asymmetric load transfer mechanisms between top and bottom beam flange joints. Thus, this paper presents a comprehensive numerical study on the working mechanism of the bottom flange bolted composite beam connections. Three available modelling methods and a new modelling method on the flange-stud-slab interactions were compared. The efficient numerical modeling method was selected and then applied to the parametric study. The influence of the composite slab, the bottom flange bolts, the shear composite ratio and the web hole shape on the seismic performance of the bottom flange bolted composite beam connections were investigated. A hogging strength calculation method was then proposed based on numerical results.

• Steel and Composite Structures
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• v.28 no.1
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• pp.39-49
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• 2018

The concrete bridge decks are usually precast and in-situ assembled with steel girders with post-pouring joint in the construction practice of super-wide steel-concrete composite beam. But the difference of concrete age between the precast slabs and the post-pouring joint has been not yet considered for the long-term performance analysis of this kind composite beam. A simply supported precast-assembled T-shaped beam was taken as an example to analyze the long-term performance of steel-concrete composite beam with post-pouring joint. Based on the deformation coordination conditions of the old-new concrete deck and steel girder, a theoretical model for the long-term behavior of precast-assembled composite beam is proposed in this paper according to age-adjusted effective modulus method. Then, the feasibility of the proposed model is verified by the available test data from the Gilbert's composite beams. Parametric studies were preformed to evaluate the influences of the cross-sectional area ratio of the post-pouring joint to the whole bridge deck, as well as the difference of concrete age between the precast slabs and the post-pouring joint, on the long-term performance of the composite beam. The results indicate that the traditional method without considering the age difference would seriously underestimate the effect of creep and shrinkage of concrete bridge decks. The concrete age difference between the precast slabs and the post-pouring joint should be demonstrated for the life cycle design and long-term performance analysis of precast-assembled steel-concrete composite beams.

• Steel and Composite Structures
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• v.24 no.3
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• pp.309-322
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• 2017

This paper conducted both numerical and theoretical studies to investigate the composite action of notched circular concrete-filled steel tubular (CFT) stub columns under axial compression and established a theoretical method to predict their ultimate bearing capacity. 3D finite element (FE) analysis was conducted to simulate the composite action and the results were in good agreement with experimental results on circular CFT stub columns with differently oriented notches in steel tubes. Parametric study was conducted to understand the effects of different parameters on the mechanical behavior of circular CFT stub columns and also the composite action between the steel tube and the core concrete. Based on the results, a theoretical formula was proposed to calculate the ultimate bearing capacity of notched CFT stub columns under compression with consideration of the composite action between the steel tube and the core concrete.

• Steel and Composite Structures
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• v.9 no.4
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• pp.367-380
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• 2009

This study focuses on the experimental evaluation of the flexural-torsional performance of high strength thin-walled composite members. A series of tests on composite members with various sectional aspect ratios subjected to eccentric cyclic loads were conducted. Test results show that the composite member's torsional strength could be approximated using a series of linear segments and evaluated using the superposition of the component steel and reinforced concrete responses. It is also validated from the tests that the strength deterioration of members subjected to combined loads is closely related to the aspect ratios of the sections. An interaction expression between the bending and torsion for high strength thin-walled composite members is proposed for engineering practice references.

• Computers and Concrete
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• v.29 no.3
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• pp.127-144
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• 2022

To investigate the flexural stiffness of the steel-composite beam, the contributions of the concrete slab and steel beam to the stiffness were considered separately. The method for flexural stiffness of the composite beam, considering the stiffness of the concrete slab and steel beam, was proposed in this paper. In addition, finite element models of the composite beams were established and validated. Parametric analyses were carried out to study the effects of different parameters on the neutral axis distance reduction factors of the concrete slab and steel beam. Afterward, the neutral axis distance reduction factors were fitted, and the stiffness combination coefficients of the two parts were solved. Based on the stiffness combination coefficients, the flexural stiffness of the composite beam can be obtained. The proposed method was validated by the tested and analyzed results. The method has a simple form and high accuracy in predicting the flexural stiffness of the steel-concrete composite beam, even though the degree of shear connection is less than 0.5.

• The Pure and Applied Mathematics
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• v.25 no.3
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• pp.193-201
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• 2018

In this paper, we discuss central index oriented and slowly changing function based some growth properties of composite entire functions.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.242-245
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• 1999

In aerospace industry improvement of structural performance of flight structure without increasing weight has great advantage. In this study, an innovative design method to increase the buckling load and tension failure load at the same time without increasing the weight was investigated by using the curvilinear fiber format in composite plates with central hole. It was investigated how much gain can be obtained with curvilinear fiber format for the plates with different hole size and different stacking sequence.