Worsak Kanok-Nukulchai

Chulalongkorn University · Chulalongkorn School of Integrated Innovation

This paper presents an enhancement of the finite element method (FEM) by adopting the moving Kriging (MK) interpolation as a substitute for the traditional hat functions. The MK shape functions can be referred as element-free because their construction is not tied to the element geometry. Kriging interpolation is a geostatistical technique for spat...

This paper introduces a new variation of the Lagrangian formulation for large-deformation analysis of continua and structures. For each individual element in the deformed mesh, the standard parental element will be used as its reference configuration. With a new definition of "natural-coordinate-based" stress, strain and constitutive tensors associ...

In this study, a method for completely eliminating the presence of transverse shear locking in the application of the element-free Galerkin method (EFGM) to shear-deformable beams and plates is presented. The matching approximation fields concept of Donning and Liu has shown that shear locking effects may be prevented if the approximate rotation fi...

A simple and efficient finite element is introduced for plate bending applications. Bilinear displacement and rotation functions are employed in conjunction with selective reduced integration. Numerical examples indicate that, despite its simplicity, the element is surprisingly accurate.

A simple, efficient and versatile finite element is introduced for shell applications. The element is developed based on a degeneration concept, in which the displacements and rotations of the shell mid-surface are independent variables. Bilinear functions are employed in conjunction with a reduced integration for the transverse shear energy. Sever...

Structural stability of plate structure is an important issue in the design of many types of civil, mechanical, and aeronautical structures. Structural instability, in the form of bifurcation or a snap-through phenomenon, can be rigorously identified by tracing the nonlinear load-displacement paths of the structure. In this chapter the total Lagran...

The nodal exact displacement based finite element method for analyzing axially loaded pile embedded in multilayered of finite depth of elastic soil is presented. The condition of shape function by which exact value may be reproduced at the nodal points regarding a few number of elements is investigated. The examined shape functions which satisfy th...

A variant of the finite element method with Kriging basis functions has been recently developed and applied to plane, plate bending, and shell elastostatic problems. The main advantage of this novel method is that high degree of basis functions can be easily constructed without additional finite element nodes (such as mid-side and inner nodes).This...

In standard FEM, the stiffness of an element is exclusively influenced by nodes associated with the element via its element-based shape functions. In this paper, the author presents a method that can be viewed as a generalization of FEM for which the influence of a node is not limited by a hat function around the node. Shape functions over an eleme...

In this paper, "finite point method" (FPM) is presented for modeling 2D shallow water flow problem. The method is based on the use of a weighted least-square approximation procedure, incorporating QR factorization and an iterative adjustment of local approximation parameters. The stabilization of the convective term in this present work is derived...

Purpose ‐ The purpose of this paper is to study the effects of the choice of database and data retrieval methods on the research performance of a number of selected Asian universities from 33 countries using two different indicators (publication volume and citation count) and three subject fields (energy, environment and materials) during the perio...

An Element Free Galerkin Method (EFGM) for the analysis of degenerated shell structures is presented. The method is based on the Moving Kriging (MK) Interpolation function. The properties of the interpolation function possess the Kronecker delta property. With the MK Interpolation function no additional treatment required at the boundary conditions...

This paper presents an improved 8-node shell element for the analysis of plates and shells. The finite element, based on a refined first-order shear deformation theory, is further improved by the combined use of assumed natural strain method. We analyze the influence of the shell element with the different patterns of sampling points for interpolat...

In this article, we investigate the vibration analysis of plates and shells, using an eight-node shell element that allows for the effects of transverse shear deformation and rotary inertia. The natural frequencies of plates and shells are presented, and the forced vibration analysis of plates and shells subjected to arbitrary loading is carried ou...

A new seamless multiscale simulation was developed for coupling the continuum model with its molecular dynamics. Kriging-based Finite Element Method (K-FEM) is employed to model the continuum base of the entire domain, while the molecular dynamics (MD) is confined in a localized domain of interest. In the coupling zone, where the MD domain overlaps...

An enhancement of the FEM using Kriging interpolation (K-FEM) offers advantages over the conventional FEM and mesh-free methods. With Kriging interpolation, the approximated field over an element is influenced not only by its own element nodes but also by a set of satellite nodes outside the element. This results in incompatibility along intereleme...

Suvarnabhumi Airport was completed and opened for commercial use on 28 September 2006. In its first phase, the airport was designed to serve 14 000 passengers during the peak hour, or 45 million passengers a year, 76 flights per hour, and to transport cargo of up to 3 million tons a year. The Airport has two runways, one 4000 m long in the east and...

An enhancement of the finite element method with Kriging shape functions (K-FEM) was recently proposed. In this method, the field variables of a boundary value problem are approximated using ‘element-by-element’ piecewise Kriging interpolation (el-KI). For each element, the interpolation function is constructed from a set of nodes within a prescrib...

A disastrous tsunami struck North Sumatra, Indonesia and many other countries on December 26, 2004. In response to this disaster, we develop a two-dimensional numerical model to simulate tsunami propagation on the open sea. Tsunami propagation-a process during which the wave has a relatively small height compared to its breadth-is modeled using the...

In order to execute dam safety planning, it is necessary to develop an index, which considers and simulates actual physical dam deterioration. The objective of this study is to monitor the behavior of dams by the experimental modal analysis. Ten model dams were tested by free drop of a steel ball to generate the different degree of damage to the da...

In the present paper, the ELF (element-based Lagrangian formulation) 9-node ANS (assumed natural strain) shell element was combined with the spring element for geometrically non-linear analysis of plates and shells sustained by arbitrary elastic edge supports that are subjected to variation in loading.This particular spring element serves as tool f...

In standard FEM the stiffness of an element is exclusively influenced by nodes associated with the element via its element-based shape functions. In this paper the author presents a method that can be viewed as a generalization of FEM for which the influence of a node is not limited by a hat function around the node. Shape functions over an element...

In performing numerical structural analysis, computers are adept at "crunching" numbers but require close guidance from human users. Oftentimes, judgment and experience of seasoned users are necessary to obtain accurate results. Furthermore, for large and complicated simulations, the analyses may require excessive computational time. Web Services a...

Recently, Kriging-based finite element method (K-FEM) has been developed for analysis of Reissner-Mindlin plates. This method provides sufficient flexibility in customizing the interpolation function for desired smoothness and accuracy. In the application to thin plates, however, the well-known finite element drawback of transverse shear locking st...

Although ebonite has been discovered for a long time, its applications were still limited to some household products. Recently, ebonite rubber has become of interest, especially for structural applications due to its high and adjustable strength and rigidity. The rigidity can be enhanced by several folds by utilizing appropriate curing conditions....

Structures such as bridges, buildings and infrastructure were constructed to serve society over an expected long period of time. Today, many of them have decayed due to aging, deterioration, misuse or lack of proper maintenance. It is important to be able to identify and monitor the health status of these structures to prevent potential sudden stru...

Component-based software development has gained wide acceptance within the computer science discipline and the software development industry. Apparently, application of this concept has not been attempted for the development of software for structural engineering applications. This paper presents the overall framework for component-based software d...

The Element-Based Lagrangian Formulation of a 9-node resultant-stress shell element is presented for the isotropic and anisotropic composite material. The effect of the coupling term between the bending strain and displacement has been investigated in the warping problem. The strains, stresses and constitutive equations based on the natural co-ordi...

Following its first introduction, this study further scrutinizes new type of shape functions for the Element-free Galerkin Method (EFGM) based on the Moving Kriging (MK) interpolation. Kriging interpolation is a geostatistical method of spatial interpolation. Its basic premise is that every unknown point can be interpolated from known scattered poi...

The Component-Based Software Development (CBSD) has established itself as a sound paradigm in the software engineering discipline and has gained wide spread acceptance in the industry. The CBSD relies on the availability of standard software components for encapsulation of specific functionality. This paper presents the framework for the developmen...

Genetic Algorithm (GA) is a new technique in optimization procedure that works best in design problems with discrete variables. It employs the survival of the fittest philosophy in determining the optimum combination. GA optimization procedure is applied to weight optimization of steel plane frames subjected to different load cases. Database of ste...

An improved version of the Element-free Galerkin method (EFGM) is presented here for addressing the problem of transverse shear locking in shear-deformable beams with a high length over thickness ratio. Based upon Timoshenko's theory of thick beams, it has been recognized that shear locking will be completely eliminated if the rotation field is con...

In the conceptualization of a cable-stayed bridge, selection of its optimal configuration is normally based on past experiences and intuition of the designer. The selection process involves the choice among different types of pylons and cable arrangements, as well as the determination of pylon height, deck depth, and the side span of the bridge. An...

A wastewater treatment plant was under construction at the Yanawa Station as part of the Bangkok Wastewater Project. The plant contained an inlet pumping station (IPS), housed in deep shaft. For the shaft, a concrete diaphragm wall was constructed, which was designed to serve as an earth-retaining wall during the excavation and later as part of the...

A Lagrangian displacement-based fluid element has been developed to model large amplitude free surface motion of nearly incompressible viscous fluids in a tank of rectangular cross-section under dynamic excitation for tuned liquid damper applications. The penalty method is employed to enforce the nearly incompressible characteristic of fluids consi...

A finite-element formulation for the large displacement analysis of beams is proposed. It is based on the degeneration approach: The governing equations for a general solid are directly discretized. The assumptions of the Timoshenko beam theory are implemented in the discretization process by devising beam elements and utilizing the penalty method....

An application of the element-based Lagrangian formulation is described for large-deformation analysis of both single-layered and laminated shells. Natural co-ordinate-based stresses, strains and constitutive equations are used throughout the formulation of the present shell element which offers significant implementation advantages compared with t...

At approximately 10:10 in the morning on August 13, 1993, the most tragic building collapse in the history of Thailand shocked the nation. The Royal Plaza Hotel collapsed swiftly and totally, leaving high only the front elevator hall, which was structurally independent from the rest of the building. The collapse of the Royal Plaza is unusual becaus...

The finite element method (FEM) was used to model cutting of wet clay by a wide tine using measured soil stress-strain characteristics as input data. The incremental method was used to deal with this geometrically nonlinear problem and correspondingly a revised tangent stiffness formula was derived and employed in the calculation. The incompressibl...

This paper presents an application of a powerful thin-walled element and a special cable element for three-dimensional modelling of steel cable-stayed bridges. Both linear and nonlinear effects are considered, as geometric nonlinearity may arise from the finite displacement of the bridge deck as well as the cables. As cable-stayed bridge decks are...

The effect of prebuckling deformation on the elastic buckling of circular plates is studied. Based on Trefftz's initial stress theory, the energy functional is obtained from which the governing differential equation for equilibrium can be derived via calculus of variations. Exact and simple approximate closed-form critical-load expressions are obta...

Considerable efforts have been made in recent years to reduce the cost of tracing the nonlinear equilibrium path of complex discretized systems by the so-called reduction methods, based on Rayleigh-Ritz technique. One important aspect of the methods is the selection of basis vectors. Recent work by Wilson has indicated that the use of Ritz vectors...

Modern cable-stayed bridge construction involves the assembly of an almost unlimited variety of deck, pylon and cable elements together, in a multitude of different ways. For their static and dynamic analyses, the application of accurate and efficient mathematical models are essential. This paper presents various methods for modelling components of...

Paper presents a point-sink fundamental solution obtained by the Hankel- Laplace transform technique. Based on this solution, an approximate solution scheme is developed for land-subsidence simulation. The mathematical model was then applied to predict the subsidence in Bangkok area due to ground-water recovery by using the superposition and Duhame...

In the present paper, an important issue concerning the application of assumed strain methods, i.e. the judicious selection of sampling points for strain interpolation, is addressed. A systematic procedure is proposed based on the concept of desirable displacement fields.

An automatic arc length control algorithm for tracing smooth equilibrium paths of nonlinear structures is developed utilizing curvature of the paths. An example on a reticulated space elastic truss structure is presented to demonstrate the efficiency of the proposed algorithm.

Finite element idealization of thin-walled structural members under combined flexural and torsional deformation, using the degeneration concept, is presented. The warping displacement field is discretized by an assembly of finite elements which together forms a specific thin-walled cross section. Based on the assumption that the distortion in the p...

Based on the three-dimensional consolidation theory of Biot, the complete set of fundamental solutions for a saturated porous half-space is derived using McNamee-Gibson displacement functions by the Hankel-Laplace tranform technique. These are half space fundamental solutions for interior vertical and horizontal point loads and interior point sourc...

This paper describes a comprehensive use of microcomputer for professional practices of structural engineers. Transition from the conventional method to a computer-based procedure calls for a complete rethinking of an accurate, unambiguous definition of all the elementary activities, their logical orders as well as inter-relationships. An integrate...

Analysis interpretive treatise (AIT) is a powerful symbolic manipulation program. It was written to serve as a comprehensive 'computing tool' for students who need to exercise real-world structural problems in the classes of modern structural analysis and elementary finite element methods. The program is organized in modules and all data units are...

A general Lagrangian formulation of structural finite elements is presented, in the context of nonlinear continuum mechanics. The element characteristics are ‘degenerated’ from 3D field equations, using kinematic characteristics of the structural member. Consistent linearization is performed to establish a Newton-Raphson solution scheme. Numerical...

The degeneration of two classes of deep beam elements is conducted, one (DB6) based on the conventional Timoshenko beam assumptions and the other (DB7) based on the assumed cubic order longitudinal displacement profile. While an adjustable shear correction factor is required for the DB6 element to compensate for the unrealistic distribution of a sh...

This study endeavors to show the inadequacy of thin beam eigenfunctions commonly used to represent displacement profiles of tall buildings in the finite strip analysis. Particularly, the model fails to reflect the correct building behaviour whenever the storey-shear distortion may be significant. An attempt is made, therefore, to develop a new set...

A semi-analytical finite element scheme for the analysis of diffusion process in linear elastic porous media is presented. Variational principle based on Biot's Theory serves to establish discretized equilibrium and flow equations in terms of nodal displacements and fluid pore pressures. Time dependency of the system is removed by the Laplace trans...

Behaviour of a waffle slab under transverse loading is investigated through a series of three-dimensional finite element analyses, and modal analysis of a deformed waffle slab cell. “Macroelement” concept is introduced, taking an advantage of the repetitive nature of waffle slab cells and the fact that only few deformation modes participate signifi...

A total Lagrangian formulation for large deformation analysis of shells by the finite element method is presented. The development of the model is based upon the three dimensional field equations. To permit solution of shell problems without numerical difficulties, a special discretization in the thickness direction is employed. The displacement fi...

We present a finite element method for a class of contact-impact problems. Theoretical background and numerical implementation features are discussed. In particular, we consider the basic ideas of contact-impact, the assumptions which define the class of problems we deal with, spatial and temporal discretizations of the bodies involved, special pro...

In Section 1, theory and algorithms for large displacement contact- impact analysis in two dimensions (i.e. plane stress, plane strain and axisymmetric) are presented. The theory encompasses a wide range of contact- impact problems and allows for a completely arbitrary contact surface development, stick, slip and frictional sliding conditions, and...

Practicing engineers often face two obstacles during the course of a design project. One is the limited access to relevant knowledge and another is the limited access to convenient computing tools. Several tasks are involved when a project is launched, in terms of computing workflow, research work, and discussion among colleagues. These tasks are r...

A class of finite element method using kriging shape functions is developed to analyze Reissner-Mindlin plates. The shape functions are constructed using kriging interpolation (KI) over a set of nodes encompassing a number of layers of elements. In addition to the commonly used gaussian correlation function, a quartic spline function is introduced...

During the past two decades, a large variety of mesh-free methods have been introduced as superior alternatives to the traditional FEM. However, the acceptance in professional practices seems to be slow due to their implementation complexities. Recently, the authors proposed a very convenient implementation of Element-free Galerkin Method (EFGM) us...

The characteristic of tsunami propagation, which has a relatively small height compared to its length, is being studied and modeled in this study. The shallow water equations, which are derived from the Navier-Stokes equations, are used as the governing equations. The method used to solve these equations is the characteristic-based split Finite Ele...