A new hierarchic degenerated shell element for geometrically non-linear analysis of composite laminated square and skew plates

우광성,Jin-Hwan Park,홍종현 국제구조공학회 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.17 No.6

This paper extends the use of the hierarchic degenerated shell element to geometric non-linear analysis of composite laminated skew plates by the p-version of the finite element method. For thegeometric non-linear analysis, the total Lagrangian formulation is adopted with moderately largedisplacement and small strain being accounted for in the sense of von Karman hypothesis. The presentmodel is based on equivalent-single layer laminate theory with the first order shear deformation includinga shear correction factor of 5/6. The integrals of Legendre polynomials are used for shape functions withp-level varying from 1 to 10. A wide variety of linear and non-linear results obtained by the p-versionfinite element model are presented for the laminated skew plates as well as laminated square plates. Anumerical analysis is made to illustrate the influence of the geometric non-linear effect on the transversedeflections and the stresses with respect to width/depth ratio (a/h), skew angle (b), and stacking sequenceof layers. The present results are in good agreement with the results in literatures.

Comparison of model order reductions using Krylov and modal vectors for transient analysis under seismic loading

한정삼 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.5

Generally, it is necessary to perform transient structural analysis in order to verify and improve the seismic performance of high-rise buildings and bridges against earthquake loads. In this paper, we propose the model order reduction (MOR) method using the Krylov vectors to perform seismic analysis for linear and elastic systems in an efficient way. We then compared the proposed method with the mode superposition method (MSM) by using the limited numbers of modal vectors (or eigenvectors) calculated from the modal analysis. In the calculation, the data of the El Centro earthquake in 1940 were adopted for the seismic loading in the transient analysis. The numerical accuracy and efficiency of the two methods were compared in detail in the case of a simplified high-rise building.

Fluid conveying piezoelectric nanosensor: Nonclassical effects on vibration stability analysis

Sayyid H. Hashemi Kachapi 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.76 No.5

In current study, surface/interface effects for pull-in voltage and viscous fluid velocity effects on dimensionless natural frequency (DNF) of fluid-conveying piezoelectric nanosensor (FCPENS) subjected to direct electrostatic voltage DC with nonlinear excitation, harmonic force and also viscoelastic foundation (visco-pasternak medium and structural damping) are investigated using Gurtin–Murdoch surface/interface (GMSIT) theory. For this analysis, Hamilton’s principles, the assumed mode method combined with Lagrange–Euler’s are used for the governing equations and boundary conditions. The effects of surface/interface parameters of FCPENS such as Lame’s constants (λI,S, μI,S), residual stress (τ0I,S), piezoelectric constants (e31psk,e32psk) and mass density (ρI,S) are considered for analysis of dimensionless natural frequency respect to viscous fluid velocity u̅f and pull-in voltage V̅DC.

Strength and microstructure of composites with cement matrixes modified by fly ash and active seeds of C-S-H phase

Grzegorz Ludwik Golewski,Bartosz Szostak 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.82 No.4

Fly ash (FA) is the main additive to concretes currently produced. This substitute of ordinary Portland cement (OPC) have a positive effect on the structure and mechanical parameters of mature concrete. Unfortunately, the problem of using FA as the OPC replacement is that it significantly reduces the performance of concretes in the early stages of their curing. This limits the possibility of using this type of concrete, e.g., in the prefabrication, where it is required to obtain high strength composites after short periods of their curing. In order to minimize these negative effects, research has been undertaken to increase the early strength of the concretes with FA through the application of a specially dedicated chemical nanoadmixture (NA) in the form of seeds of the C-S-H phase. Therefore, this paper presents results of tests of modified concretes both with the addition of FA and with NA. The analyses were carried out based on the results of the macroscopic and microstructural tests in 5 time periods, i.e. after: 4, 8, 12, 24 and 72 hours. The greatest increase in mechanical strength parameters and rapid development of the basic matrix phases in composites in the first 12 hours of composites curing was observed.

Analysis of torsional-bending FGM beam by 3D Saint-Venant refined beam theory

Ilies Guendouz,Mourad Khebizi,Hamza Guenfoud,Mohamed Guenfoud,Rached El Fatmi 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.3

In this article, we present torsion-bending analysis of a composite FGM beam with an open section, according to the advanced and refined theory of 1D / 3D beams based on the 3D Saint-Venant’s solution and taking into account the edge effects. The (initially one-dimensional) model contains a set of three-dimensional (3D) displacement modes of the cross section, reflecting its 3D mechanical behaviour. The modes are taken into account depending on the mechanical characteristics and the geometrical form of the cross-section of the composite FGM beam. The model considered is implemented on the CSB (Cross- Section and Beam Analysis) software package. It is based on the RBT/SV theory (Refined Beam Theory on Saint-Venant principle) of FGM beams. The mechanical and physical characteristics of the FGM beam continuously vary, depending on a power-law distribution, across the thickness of the beam. We compare the numerical results obtained by the three-beam theories, namely: The Classical Beam Theory of Saint-Venant (Classical Beam Theory CBT), the theory of refined beams (Refined Beam Theory RBT), and the theory of refined beams, using the higher (high) modes of distortion of the cross-section (Refined Beam Theory using distorted modes RBTd). The results obtained confirm a clear difference between those obtained by the three models at the level of the supports. Further from the support, the results of RBT and RBTd are of the same order, whereas those of CBT remains far from those of higher-order theories. The 3D stresses, strains and displacements, obtained by the present study, reflect the 3D behaviour of FGM beams well, despite the initially 1D nature of the problem. A validation example also shows a very good agreement of the proposed models with other models (classical or higher-order beam theory) and Carrera Unified Formulation 1D-beam model with Lagrange Expansion functions (CUF-LE).

An assumed-stress hybrid element for modeling of plates with shear deformations on elastic foundation

Kutlu Darilmaz 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.33 No.5

In this paper a four-node hybrid stress element is proposed for analysing arbitrarily shaped plates on a two parameter elastic foundation. The element is developed by combining a hybrid plate stress element and a soil element. The formulation is based on Hellinger-Reissner variational principle in which both inter element compatible boundary displacement and equilibrated stress fields for the plate as well as the foundation are chosen separately. This formulation also allows a low order polynomial interpolation functions. Numerical examples are presented to show that the validity and efficiency of the present element for the plate analysis resting on an elastic foundation. In these examples the effect of soil depth,interaction between closed plates on soil parameters, comparison with Winkler hypothesis is investigated.

Life cycle cost analysis and smart operation mode of ground source heat pump system

윤석,이승래 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.16 No.4

This paper presents an advanced life cycle cost (LCC) analysis of a ground source heat pump (GSHP) system and suggests a smart operation mode with a thermal performance test (TPT) and an energy pile system constructed on the site of the Incheon International Airport (IIA). First, an economic analysis of the GSHP system was conducted for the second passenger terminal of the IIA considering actual influencing factors such as government support and the residual value of the equipment. The analysis results showed that the economic efficiency of the GSHP system could be increased owing to several influential factors. Second, a multiple regression analysis was conducted using different independent variables in order to analyze the influence indices with regard to the LCC results. Every independent index, in this case the initial construction cost, lifespan of the equipment, discount rate and the amount of price inflation can affect the LCC results. Third, a GSHP system using an energy pile was installed on the site of the construction laboratory institute of the IIA. TPTs of W-shape and spiral-coil-type GHEs were conducted in continuous and intermittent operation modes, respectively, prior to system operation of the energy pile. A cooling GSHP system in the energy pile was operated in both the continuous and intermittent modes, and the LCC was calculated. Furthermore, the smart operation mode and LCC were analyzed considering the application of a thermal storage tank.

Scour-monitoring techniques for offshore foundations

Yong-Hoon Byun,Kiwon Park,이종섭 국제구조공학회 2015 Smart Structures and Systems, An International Jou Vol.16 No.4

The scour induced by strong currents and wave action decreases the embedded length of monopiles and leads to a decrease of their structural stability. The objective of this study is the development and consideration of scour-monitoring techniques for offshore monopile foundations. Tests on physical models are carried out with a model monopile and geo-materials prepared in a cylindrical tank. A strain gauge, two coupled ultrasonic transducers, and ten electrodes are used for monitoring the scour. The natural frequency, ultrasonic reflection images, and electrical resistivity profiles are obtained at various scour depths. The experimental results show that the natural frequency of the model monopile decreases with an increase in the scour depth and that the ultrasonic reflection images clearly detect the scour shape and scour depth. In addition, the electrical resistivity decreases with an increase in scour depth. This study suggests that natural frequency measurement, ultrasonic reflection imaging, and electrical resistivity profiling may be used as effective tools to monitor the scour around an offshore monopile foundation.

Energy dissipation of steel-polymer composite beam-column connector

Yun-Che Wang,Chih-Chin Ko 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.5

The connection between a column and a beam is of particular importance to ensure the safety of civil engineering structures, such as high-rise buildings and bridges. While the connector must bear sufficient force for load transmission, increase of its ductility, toughness and damping may greatly enhance the overall safety of the structures. In this work, a composite beam-column connector is proposed and analyzed with the finite element method, including effects of elasticity, linear viscoelasticity, plasticity, as well as geometric nonlinearity. The composite connector consists of three parts: (1) soft steel; (2) polymer; and (3) conventional steel to be connected to beam and column. It is found that even in the linear range, the energy dissipation capacity of the composite connector is largely enhanced by the polymer material. Since the soft steel exhibits low yield stress and high ductility, hence under large deformation the soft steel has the plastic deformation to give rise to unique energy dissipation. With suitable geometric design, the connector may be tuned to exhibit different strengths and energy dissipation capabilities for real-world applications.

Cyclic test for beam-to-column abnormal joints in steel moment-resisting frames

Zu Q. Liu,Jian Y. Xue,Xiu N. Peng,Liang Gao 국제구조공학회 2015 Steel and Composite Structures, An International J Vol.18 No.5

Six specimens are tested to investigate the cyclic behavior of beam-to-column abnormal joints in steel moment-resisting frames, which are designed according to the principle of strong-member and weak-panel zone. Key parameters include the axial compression ratio of column and the section depth ratio of beams. Experimental results indicate that four types of failure patterns occurred during the loading process. The P-hysteretic loops are stable and plentiful, but have different changing tendency at the positive and negative direction in the later of loading process due to mechanical behaviors of specimens. The ultimate strength tends to increase with the decrease of the section depth ratio of beams, but it is not apparent relationship to the axial compression ratio of column, which is less than 0.5. The top panel zone has good deformation capacity and the shear rotation can reach to 0.04 rad. The top panel zone and the bottom panel zone don't work as a whole. Based on the experimental results, the equation for shear strength of the abnormal joint panel zone is established by considering the restriction of the bottom panel zone to the top panel zone, which is suitable for the abnormal joint of H-shaped or box column and beams with different depths.