Jinkyu Kim

Shear performance of plain UHPC (ultrahigh‐performance concrete) construction joints is studied in both experimental and analytical ways. In push‐off tests, three different contact surfaces of the construction joint were considered, while the case without any joint was provided for the reference. Test results indicate that the geometry of contact surfaces greatly affects shear performance of the construction joint. With simplifying structural behavior of contact surfaces and UHPC substrate, the

The extended framework of Hamilton's principle and the mixed convolved action principle provide new rigorous weak variational formalism for a broad range of initial boundary value problems in mathematical physics and mechanics. In this paper, their potential when adopting temporally higher order approximations is investigated. The classical single-degree-of-freedom dynamical systems are primarily considered to validate and to investigate the performance of the numerical algorithms developed from

Based upon the extended framework of Hamilton’s principle, unified space–time finite element methods for viscoelastic and viscoplastic continuum dynamics are presented, respectively. For numerical efficiency, mixed time-step algorithm in time- and displacement-based algorithm in space are adopted. Through analytical investigation, we demonstrate that the Newmark’s constant average acceleration method and the present method are the same for viscoelasticity. With spatial eight-node brick elements,

This paper presents experimental and numerical studies for predicting the seismic responses of welded and bolted steel beam–column connections, namely, welded unreinforced flange and bolted web connection, and welded unreinforced flange and welded web connection. Cyclic tests of these connections composed of members applied widely to steel structures are conducted to examine their seismic performance. Numerical simulations with a focus on the bolted joint are conducted using a nonlinear finite e

Hamilton's principle is extended to have compatible initial conditions to the strong form. To use a number of computational and theoretical benefits for dynamical systems, the mixed variational formulation is preferred in the systems other than particle systems. With this formulation and the Rayleigh's dissipation function, we could have all the pertinent initial/boundary conditions for both conservative and non-conservative dynamical system. Based upon the extension framework of Hamilton's prin

본 논문에서는 이중여자 유도발전기 기반 가변속도 풍력발전 시스템의 퍼지 모델링 및 안정도 해석에 관하여 다루고자 한다. 일반적인 풍력발전 시스템은 복잡한 비선형성 기반 동적방정식으로 구성되며, 플랜트를 구성하는 각 파라미터 수치 역시 주변 환경에 의해 변화할 여지가 있다. 풍력발전 시스템의 해석을 위하여 본 논문에서는 비선형성 및 불확실성에 강인한 퍼지 제어 기법을 기반으로 제어이론을 구성하고자 한다. 이중여자 유도발전기 기반 풍력발전 시스템의 퍼지 모델링 및 시스템 안정화를 위한 퍼지 제어기 설계 기법이 제안된다. 해당 제어 기법은 리아푸노프 기반 안정도 해석에 의해 점근 안정도를 보장받게 되며, 가상 시뮬레이션을 통한 시스템 효율성을 입증하게 된다. This paper propose the robust stability algorithm for controlling a variable speed wind power system which based on doubly-fed ind

With basic ideas of mixed Lagrangian formulation and sequential assigning process for initial conditions, the extended framework of Hamilton’s principle (EHP) was recently developed for continuum dynamics. Unlike the original Hamilton’s principle, this new variational framework can fully take initial conditions into account for both linear and nonlinear dynamics, so that it provides a sound base to apply a finite element scheme over the temporal domain without any ambiguity. This paper describes

Investigation of the lower molecular weight phenolics from the needles of Taxus cuspidata led to the isolation and structural elucidation of (+)-catechin, (-)-epicatechin and (+)-catechin-(5,6-bc)-4beta-(4''-hydroxyphenyl)-dihydro-2(H)-pyranone (1), a new phenylpropanoid flavan-3-ol. The structures of these compounds were established on the basis of chemical and spectroscopic evidence.