• Steel and Composite Structures
• /
• 제44권3호
• /
• pp.437-450
• /
• 2022

When the vertical load-bearing members in high-rise structures fail locally, the beam-column joints play an important role in the redistribution of the internal forces. In this paper, a static laboratory test of three full-scale flush flange beam-reinforced connections with side and cover plates (CP-FBSP connection) with double half-span steel beams and single L-shaped columns composed of concrete-filled steel tubes (L-CFST columns) was conducted. The influence of the side plate width and cover plate thickness on the progressive collapse resistance of the substructure was thoroughly analyzed. The failure mode, vertical force-displacement curves, strain variation, reaction force of the pin support and development of internal force in the section with the assumed plastic hinge were discussed. Then, through the verified finite element model, the corresponding analyses of the thickness and length of the side plates, the connecting length between the steel beam flange and cover plate, and the vertical-force eccentricity were carried out. The results show that the failure of all the specimens occurred through the cracking of the beam flange or the cover plate, and the beam chord rotations measured by the test were all greater than 0.085 rad. Increasing the length, thickness and width of the side plates slightly reduced the progressive collapse resistance of the substructures. The vertical-force eccentricity along the beam length reduced the progressive collapse resistance of the substructure. An increase in the connecting length between the beam flange and cover plate can significantly improve the progressive collapse resistance of substructures.

• Wind and Structures
• /
• 제34권2호
• /
• pp.215-230
• /
• 2022

Majority of transmission line system failures at many locations worldwide have been caused by severe localized wind events in the form of tornadoes and downbursts. This study evaluates the structural response of two different transmission line systems under equivalent F2 tornadoes obtained from real incidents. Two multi-span self-supported transmission line systems are considered in the study. Nonlinear three-dimensional finite element models are developed for both systems. The finite element models simulate six spans and five towers. Computational Fluid Dynamics (CFD) simulations are used to develop the tornado wind fields. Using a proper scaling method for geometry and velocity, full-scale tornado flow fields for the Stockton, KS, 2005 and Goshen County WY, 2009 are developed and considered together with a previously developed tornado wind field. The tornado wind profiles are obtained in terms of tangential, radial, and axial velocities. The simulated tornadoes are then normalized to the maximum velocity value for F2 tornadoes in order to compare the effect of different tornadoes having an equal magnitude. The tornado wind fields are incorporated into a three-dimensional finite element model. By varying the location of the tornado relative to the transmission line systems, base shears of the tower of interest and peak internal forces in the tower members are evaluated. Sensitivity analysis is conducted to assess the variation of the structural behaviour of the studied transmission lines associated with the location of the tornado relative to the tower of interest. The tornado-induced forces in both lines due to the three different normalized tornadoes are compared with corresponding values evaluated using the simplified load case method recently incorporated in the ASCE-74 (2020) guidelines, which was previously developed based on the research conducted at Western University.

• Wind and Structures
• /
• 제34권2호
• /
• pp.199-213
• /
• 2022

The current study investigates the dynamic effects in the tornado-structure response of an aeroelastic self-supported lattice transmission tower model tested under laboratory simulated tornado-like vortices. The aeroelastic model is designed for a geometric scale of 1:65 and tested under scaled down tornadoes in the Wind Engineering, Energy and Environment (WindEEE) Research Institute. The simulated tornadoes have a similar length scale of 1:65 compared to the full-scale. An extensive experimental parametric study is conducted by offsetting the stationary tornado center with respect to the aeroelastic model. Such aeroelastic testing of a transmission tower under laboratory tornadoes is not reported in the literature. A multiaxial load cell is mounted underneath the base plate to measure the base shear forces and overturning moments applied to the model in three perpendicular directions. A three-axis accelerometer is mounted at the level of the second cross-arm to measure response accelerations to evaluate the natural frequencies through a free-vibration test. Radial, tangential, and axial velocity components of the tornado wind field are measured using cobra probes. Sensitivity analyses are conducted to assess the variation of the structural dynamic response associated with the location of the tornado relative to the lattice transmission tower. Three different layouts representing the change in the orientation of the tower model relative to the components of the tornado-induced loads are considered. The structural responses of the aeroelastic model in terms of base shear forces, overturning moments, and lateral accelerations are measured. The results are utilized to understand the dynamic response of self-supported transmission towers to the tornado-induced loads.

• Tribology and Lubricants
• /
• 제39권1호
• /
• pp.21-27
• /
• 2023

Surface texturing is widely applied to friction surfaces of various machine elements. Most of the theoretical studies have focused on isothermal (ISO) analyses which consider constant lubricant viscosity. However, there have been limited studies on the effect of oil temperature increase owing to viscous shear. Following the first part of the present study that investigated the effects of film-temperature boundary condition (FTBC) and groove number on the thermohydrodynamic (THD) lubrication characteristics of a surface-textured parallel thrust bearing with multiple rectangular grooves, this study focuses on the effect of groove depths. Current study numerically analyzes the continuity, Navier-Stokes, and energy equations with temperature-viscosity-density relations using a commercial computational fluid dynamics (CFD) software, FLUENT. The results of variation in temperature, velocity, and pressure distributions as well as load-carrying capacity (LCC) and friction force indicate that groove depth and FTBC significantly influence the temperature distribution and pressure generation. The LCC is maximum near the groove depth at which the vortex starts, smaller than the ISO result. For intense grooves, the LCC of THD may be larger than that from ISO. The frictional force decreases as the groove becomes deeper, and decreases more significantly in the case of THD. The study shows that groove depth significantly influences the THD lubrication characteristics of surface-textured parallel thrust bearings.

• Structural Engineering and Mechanics
• /
• 제85권5호
• /
• pp.593-605
• /
• 2023

This work presents a comparison between analytical and finite element analysis for bending of porous sandwich functionally graded material (FGM) plates. The plate is rectangular and simply supported under static sinusoidal loading. Material properties of FGM are assumed to vary continuously across the face sheets thickness according to a power-law function in terms of the volume fractions of the constituents while the core is homogeneous. Four types of porosity are considered. A refined higher-order shear with normal deformation theory is used. The number of unknowns in this theory is five, as against six or more in other shear and normal deformation theories. This theory assumes the nonlinear variation of transverse shear stresses and satisfies its nullity in the top and bottom surfaces of the plate without the use of a shear correction factor. The governing equations of equilibrium are derived from the virtual work principle. The Navier approach is used to solve equilibrium equations. The constitutive law of the porous FGM sandwich plate is implemented for a 3D finite element through a subroutine in FORTRAN (UMAT) in Abaqus software. Results show good agreement between the finite element model and the analytical method for some results, but the analytical method keeps giving symmetric results even with the thickness stretching effect and load applied to the top surface of the sandwich.

• Geomechanics and Engineering
• /
• 제33권1호
• /
• pp.11-18
• /
• 2023

This study explores a new energy partitioning approach to determine the fracture toughness of 3-D printed pristine/recycled high density polyethylene (HDPE) blends employing the essential work of fracture (EWF) concept. The traditional EWF approach conducts a uniaxial tensile test with double-edge notched tensile (DENT) specimens and measures the total energy defined by the area under a load-displacement curve until failure. The approach assumes that the entire total energy contributes to the fracture process only. This assumption is generally true for extruded polymers that fracture occurs in a material body. In contrast to the traditional extrusion manufacturing process, the current 3-D printing technique employs fused deposition modeling (FDM) that produces layer-by-layer structured specimens. This type of specimen tends to include separation energy even after the complete failure of specimens when the fracture test is conducted. The separation is not relevant to the fracture process, and the raw experimental data are likely to possess random variation or noise during fracture testing. Therefore, the current EWF approach may not be suitable for the fracture characterization of 3-D printed specimens. This paper proposed a new energy partitioning approach to exclude the irrelevant energy of the specimens caused by their intrinsic structural issues. The approach determined the energy partitioning location based on experimental data and observations. Results prove that the new approach provided more consistent results with a higher coefficient of correlation.

• Steel and Composite Structures
• /
• 제45권3호
• /
• pp.437-454
• /
• 2022

Elliptic-braced simple resisting frame as a new lateral bracing system installed in the middle bay of frame in building facades has been recently introduced. This system not only creates a problem for opening space from the architectural viewpoint but also improves the structural behavior. Despite the researches on the seismic performance of lateral bracing systems, there are few studies performed on the effect of the stiffness parameters on the elastic story drift and calculation of period in simple braced steel frames. To overcome this shortcoming, in this paper, for the first time, an analytical solution is presented for calculating elastic lateral stiffness in a simple steel frame equipped with elliptic brace subjected to lateral load. In addition, for the first time, in this study, a precise formulation has been developed to evaluate the elastic stiffness variation in a steel frame equipped with a two-dimensional single-story single-span elliptic brace using strain energy and Castigliano's theorem. Thus, all the effective factors, including axial and shear loads as well as bending moments of elliptic brace could be considered. At the end of the analysis, the lateral stiffness can be calculated by an improved and innovative relation through the energy method based on the geometrical properties of the employed sections and specification of the used material. Also, an equivalent element of an elliptic brace was presented for the ease of modeling and use in linear designs. Application of the proposed relation have been verified through a variety of examples in OpenSees software. Based on the results, the error percentage between the elastic stiffness derived from the developed equations and the numerical analyses of finite element models was very low and negligible.

• 한국지반공학회논문집
• /
• 제22권4호
• /
• pp.51-59
• /
• 2006

본 고에서는 선행연구(홍성연, 2004)에서 개발한 대형직접전단시험기를 이용하여 조립질 토목재료의 시험밀도와 균등계수의 크기가 전단강도에 주는 영향을 분석하였으며, 아울러, 각 수직응력별로 한계상태에서 조립재료가 갖고 있는 마찰계수를 Wood(1998)가 제안한 방정식을 이용하여 산출하였다. 시험에 사용한 재료는 경상과 전라지역 석산에서 생산중인 조립재료이다. 시험결과 시험밀도 $2.10g/cm^3$의 전단강도의 크기가 $1.85g/cm^3$의 값보다 상대적으로 크게 나타났으며, 균등계수는 상대적으로 10.0보다 5.0일때 더 큰 전단강도를 갖는 것으로 나타났다. 한편, 조립질 토목재료가 갖고 있는 한계상태에서의 마찰계수는 각 시험조건별로 $1.0{\sim}1.6$의 범위로 나타났다.

• 한국지반공학회논문집
• /
• 제23권3호
• /
• pp.141-147
• /
• 2007

말뚝의 동적 응답 해석을 위한 다양한 방법들이 개발되어 있으며, 이 중에서 비선형 스프링, p-y 곡선을 이용하여 지반-말뚝 상호작용을 고려하는 방법이 널리 사용되고 있다. 그러나, 현재 사용되는 동적 p-y 곡선은 정적 또는 주기 하중에 의한 횡방향 재하 시험에 의해 개발되었다. 또한, p-y 곡선에 scaling factor를 도입하여 액상화에 의한 지반-말뚝 상호작용의 영향을 모사하고자 하는 시도가 이루어져 왔으나, 지금까지 정확한 scaling factor를 산정하지 못하고 있는 실정이다. 이에 본 연구에서는 Ig 진동대 실험으로부터 구한 말뚝 주변 지반의 과잉간극수압과 지반-말뚝 시스템의 고유진동수 관계 및 수치해석으로부터 구한 말뚝 주변 지반의 탄성계수의 변화와 지반-말뚝 시스템의 고유진동수 관계로부터, 말뚝 주변 지반의 탄성계수의 변화로 표현되는 p-y 곡선의 scaling factor를 구하였다. 그 결과, scaling factor는 과잉간극수압비에 따른 지수 함수의 형태로 나타났다.

• 한국컴퓨터정보학회논문지
• /
• 제14권9호
• /
• pp.179-187
• /
• 2009

세계시장은 글로벌(Global)기업의 등장과 함께 국가 간 경계를 약화시켰으며, 제품의 설계, 마케팅 활동은 현지시장 위주, R&D 활동은 지식활동이 활발한 지역 단순 제품의 조립 제조는 저임금 지역으로 분산되고 있다. 이는 생산거점과 판매거점을 연결하는 네트워크(Network) 구성의 중요성이 대두되고 있다는 반증이다. 90년대 초부터는 다품종 소량생산, 고급화 및 소비자의 생산 프로세스 참여를 통한 수요창출 등 소비자 중심의 시장으로 다변화하고 있다. 이는 물류 체계에 있어 기술적 변화 요구에 적절히 대응하는 현상으로, 이를 증명하는 것이 e-비즈니스 등장과 이를 지원하는 부가가치 통신망(VAN: Value added Network) 전자문서교환(EDI : Electronic Data Interchange) 등이다. 본 연구에서는 국내외 육상, 해상 항공물류 시스템에 관한 문헌 연구를 통하여 각 시스템에 대한 실용분석을 시도하였으며, 한편으로 국내 항공사의 모델을 기초하여 항공사 물류시스템의 향후 개선 및 발전 방향을 제시하였다.