The shear failure probabilities of reinforced concrete beam-column joints have been investigated by Monte Carlo method. The theoretical shear strength of joints is based on the softened strut-and-tie model proposed by Hwang and Lee (2002). The random variables included in this study are the strengths of concrete, the ultimate compression strain of concrete, the strengths of reinforcement, the dimensions of cross-section, and the model error of theoretical shear strength of joints. The shear failure probabilities of joints with SD 280 flexural reinforcement in the beams designed using the ACI Code are all higher than 0.04. The joints designed according to the softened strut-and-tie model are safer than those designed according to the ACI Code. The shear failure probabilities of exterior joints are higher than those of interior joints. The shear failure probabilities of joints with SD 280 flexural reinforcement in the beams are higher than those of joints with SD 420 flexural reinforcement.

The effect of Coriolis force on the rivulet (fingering) instability, the onset of rivulet phenomena during spin coating, is investigated by flow visualization experiments incorporating with dimensional analysis. This study demonstrates that the Coriolis force will affect significantly the critical radius of rivulet instability and the deflection angle of instability rivulet. For the cases of low Bond number, the effect of Coriolis force is a stabilizing factor, and the dimensionless critical radius increases slightly with increasing rotational Reynolds number Reω. In the case of high Bond number, the effect of Coriolis force becomes a destabilizing factor while Reω < 1, and a characteristic length is found by balancing the viscous force with the surface tension. For Reω > 1, the radial Corilois force, which is always pointing inward, plays a stabilizing role with magnitude Reω2.

An energy-based damage model is proposed and applied to predict the fracture initiation of the sheet metal forming process. The fracture mechanism is investigated through the plastic energy dissipation. The concepts of the damaging work and the fracture energy are proposed for the quantitative description of damage evolution and crack initiation. The developed formulations are implemented into the finite element program ABAQUS to simulate the biaxial stretching of sheet metals and to predict the fracture strains. The material parameter needed in the damage model for fracture prediction is determined by the stress-strain history of the uniaxial tensile test. The forming limits for aluminum alloy sheets under various strain paths are predicted by the present approach and then compared to the measured data quoted from the literatures [1,2]. Good agreements are found between this study and the previous results.

Equations governing large eddy simulations are usually closed by incorporating with the Smagorinsky-Lilly's turbulence model of eddy viscosity. The model contains a so-called filtering length and a Smagorinsky-Lilly “constant” that changes among different researchers. The variation range of the constant is wide and its value is usually determined in a sense of “guessing”. Since the constant is closely related to the magnitude of eddy viscosity, hence to our numerical solutions eventually, setting a more precise and determinate procedure for prescribing the constant seems to be worthy it. The constant, CSL, is first estimated in use of the properties of fluid flow within the inertia subrange. Then, along with a general derivation, the explicit closed-form expression for the constant is presented for steady uniform flows. It is found that, with the analogy between the filtering technique and Reynolds average, CSL may not necessarily be constant but proportional to the Manning n and water depth. Other than the determination of CSL, the vertical flow velocity profile in an infinitely long wide rectangular channel without spiral flow motion is obtained through the use of the Smagorinsky-Lilly's turbulence closure model. It is shown analytically that the velocity profile in unsteady open channel flow can be expressed as a function of an integration function Jn(z) that accounts for wind stress and inertia terms. With the velocity profile, effects of inertia terms, wind stress, and channel bed roughness on CSL are deeply explored in response to the dependence of CSL on Jn(z).

A semi-analytical finite element (SAFE) method is presented for constructing solutions for an arbitrarily loaded cylinder, whose cross-section is general in terms of its shape and the number of distinct, perfectly bonded elastic, rectilinear anisotropic materials. The surface traction and body force loads need to be expressed in a power series of the axial coordinate. Linear three-dimensional theory is used. For a homogeneous isotropic cylinder, it is known as the Almansi-Michell problem, and the SAFE analysis herein is an extension to inhomogeneous, anisotropic bodies. By SAFE, the cross-section is discretized. The displacement field is expressed by interpolation functions over the cross-section and by analytical functions axially. The method herein is an extension of the authors' previous method cylinder with a general cross-section. Herein, the SAFE solution procedure is given and numerical examples will be presented.

An approach to establish a master curve for effective creep compliances of polymeric off-axis composites with various fiber orientations was presented. Carbon/epoxy composite IM7/977–3 was used to fabricate four types of off-axis specimens and then subjected to momentary creep tests after a period of initial aging. Creep compliance and elastic compliance were separated from the total compliance. Using one-parameter creep potential theory, creep compliances were transformed to effective creep compliances. After choosing a proper value for the one-parameter, all effective creep compliances with various off-axis fiber orientations were superposed into a master curve. This master curve enables us to obtain creep compliance with any off-axis fiber orientation by testing only one off-axis specimen.

Numerical properties of the Newmark explicit method in the solution of nonlinear systems are explored. It is found that the upper stability limit is no longer equal to 2 for the Newmark explicit method for nonlinear systems. In fact, it is enlarged for stiffness softening and is reduced for stiffness hardening. Furthermore, its relative period error increases with the increase of the step degree of nonlinearity for a given value of the product of the natural frequency and the time step. It is also verified that the viscous damping determined from an initial stiffness is effective to reduce displacement response in the solution of a nonlinear system as that for solving a linear elastic system. All the theoretical results are confirmed with numerical examples.

The oscillatory characteristics and dynamic structure of periodic flow in an oscillatory gas flow meter were studied experimentally and numerically. The flow oscillations were triggered by the Coanda effect and an universal correlation between Strouhal number and Reynolds number, Str = 1.09 × 10−3 for ReHD >800, was deduced based on spectral analysis of the pressure fluctuations in the flow channel. Numerical simulation indicated that the evolution of the flow patterns was classified into stages of induction and sustainable periodic oscillation. The transformation between the two stages was noticeably affected by the design of the feedback channels. The results further revealed that the development of the main vortex in the oscillating chamber and the small vortices at the entrance of the feedback channels concurrently modulate the mechanism of oscillation. The small vortices located at both entrances of the feedback channels play the role of a pair of modulating valves, which alternatively switch on and off the bypass flow through each feedback channel, thus reinforcing the periodic oscillation.

The α-function method is a family of second-order explicit methods with controlled numerical dissipation. Thus, it is very promising for the pseudodynamic testing of a system where high frequency responses are of no interest. This is because that favorable numerical dissipation can suppress the spurious growth of high frequency responses, which might arise from numerical and/or experimental errors during a test. Furthermore, the implementation of an explicit method for the pseudodynamic testing is much simpler than for an implicit method. The superiority of using this method in performing a pseudodynamic test was verified both analytically and experimentally. In fact, results of error propagation analysis reveal that the spurious growth of high frequency responses can be suppressed and less error propagation is identified when compared to the Newmark explicit method. Actual tests were conducted pseudodynamically to confirm all the analytical results. It is also illustrated that although the high frequency response is insignificant to the total response it may be significantly amplified and propagated and finally destroys the pseudodynamic test results.

The order of stress singularity at a sharp corner of a plate needs to be known before a numerical approach can be taken to determine accurately the stress distribution of a plate with irregular geometry (such as a V-notch) under loading. This work analyzes the order of the stress singularity at a bi-material corner of a thick plate under bending, based on Reddy's third-order shear deformation plate theory. An eigenfunction expansion technique is used to derive the asymptotic displacement field in the vicinity of the sharp corner by solving the equilibrium equations in terms of displacement functions. This paper explicitly shows the first known characteristic equations for determining the order of the stress singularity at the interface corner of a bonded dissimilar isotropic plate. Moreover, the numerical results are given in graphic form for the order of stress singularity at the interface corner in bonded dissimilar isotropic plates and at the vertex of a bi-material wedge with free radial edges. The results presented herein fill some of the gaps in the literature

The mixing behavior of a two-channel micromixer with a circular mixing chamber at four different chamber depths and six different flow rates had been investigated. Experiments were implemented with the mixings of two fluids. An image inspection method using the variance of the image gray level contrast as the measurement parameter to determine the mixing efficiency distribution in these mixers. The steady, three-dimensional and laminar flow fields inside the micromixers were also simulated numerically with a finite volume discretization. Through the numerical integration over the chamber depth, the three-dimensional numerical prediction could be compressed into a two-dimensional result, which could be directly used to compare with the experimental measurements. Experimental results show that the measured mixing efficiency is raised with the increase of chamber depth. The numerical prediction of mixing efficiency agreed qualitatively with those obtained from the experimental measurements, while the ratio of the depth to diameter of the mixing chamber is big enough to eliminate the viscosity effect.

This paper develops the method of fundamental solutions (MFS) to solve eigenfrequencies of plate vibrations of multiply connected domains. The complex-valued MFS combined with the mix potential method are utilized in order to avoid the spurious eigenvalues. The benchmarked problems of annular plates with clamped, simply supported and free boundary conditions are studied analytically as well as numerically. Wherein the results demonstrate that all true eigenvalues are contained and no spurious eigenvalues are included. In the analytical studies, the continuous version of the MFS is utilized to obtain the eigenequation by applying the degenerate kernels and Fourier series. The proposed numerical method is free from singularities, meshes, and numerical integrations and thus can be easily utilized to solve plate vibrations free from spurious eigenvalues in multiply connected domains.

The purpose of the present study is to investigate laminar fully developed flow in a horizontal rectangular channel with a cylinder solutal source adjacent to planar boundary. The boundaries in this experiment include four cases:

(A) Cylinder is cathode and top plate is anode;

(B) Cylinder is anode and top plate is cathode;

(C) Cylinder is cathode and bottom plate is anode;

(D) Cylinder is anode and bottom plate is cathode.

The influences of the mass transfer rate and the boundary types between the sources have also been investigated. An experimental investigation of mixed convection mass transfer between a cylinder and a plate mass source with an electrochemical system is carried in a horizontal rectangular channel. The working fluid here is CuSO4 + H2SO4 + H2O. The shadowgraph technique is used to visualize the flow and to determine the nature and effect of solutal driven secondary flows in a horizontal channel. The ranges of the parameters in the work are Pr = 7, Ar = 1, Sc = 1700 ∼ 2400, Re = 50 ∼ 200 (Red= 12.5 ∼50), Grm = 9.45 × 105, d/H = 0.25, h/d=0, 3.

A method for investigating the pure squeeze action in an isothermal elastohydrodynamically lubrication (EHL) problem, i.e., circular contacts lubricated with couple stress fluid, was developed. A constant load condition was used in the calculations. The initial conditions such as pressure profiles, normal squeeze velocities, and film shapes were obtained from the classical hydrodynamic lubrication theory at a specified large central film thickness. The coupled transient modified Reynolds, elasticity deformation, and load equilibrium equations are solved simultaneously. The simulation results reveal that the effect of the couple stress is equivalent to enhancing the lubricant viscosity, thus enlarging the film thickness. The effect of couple stress in thin film lubrication varies with film size. That is, the thinner the lubricating film is, the more obvious the effect of couple stress is. For larger characteristic length, materials parameter, and load, the central pressure, central film thickness, and rigid separation are larger than those of smaller characteristic length under the same load. The time needed to achieve maximum central pressure and the Hertzian pressure increases with increasing characteristic length.

This paper presents the Statistical Analysis of Passive Sonar Performance Prediction in Littoral Environments. Passive sonar performance and acoustic prediction mainly refer to the detection range. The inputs for estimating the sonar detection range include the Figure of Merit (FOM), Transmission Loss (TL), and Ambient Noise (NL) of the operation region. These inputs are directly related to the ocean environment; hence, the detection range is, too. A littoral environment is highly variable both in time and space. This paper proposes a methodology for analyzing the statistical properties of the detection range from measurements of ocean water column properties. It is found that the detection range of the southwestern region of Taiwan in the summer is 13.8km with 5.9km as the standard deviation and in the winter is 37.8km with 33.6km as the standard deviation.

Creep is the time-dependent, viscoelastic strain observed in materials under constant stress. Creep can increase structural strains/deformations to non-serviceable levels or alter the stress distribution among structural components. While stress redistribution can be helpful in composite materials by relieving the stress on one component, it might have a detrimental effect on another, especially if it leads to overstressing.

A step-by-step in time approach for modeling creep in quasi-brittle materials such as concrete and masonry is utilized, and a new continuum damage model based on Weibull's failure rate distribution is introduced. A multiplicative approach to integrate the creep and damage effects within the step-by-step in time analysis is invoked. The significance of the proposed approach is exemplified through analysis of a clay masonry column filled with grout and subjected to concentric axial load. It is shown that the proposed approach can provide insights on the stress evolution in both components of the composite material that might not be inferred using classical methods of analysis.

Biot's poroelastic theory is employed to study stress wave propagation in an infinite slab of arbitrary thickness. The frequency equation is obtained each for pervious and impervious surfaces for a nondissipative medium. Appropriate numerical data is presented in the form of graphs and then results are discussed. Waves in a thin bar and in a semi-infinite slab are discussed as limiting cases.

The flow of a viscous fluid disturbed by an oscillating plate of arbitrary initial phase is studied in present note. The exact solutions of the velocity and the shear stress are solved using a Laplace transform method. The velocity is derived in terms of complementary error functions and the shear stress on the boundary is given in the form of Fresnel integrals. Since the steady-state solutions are well known, our discussions are focused on the transient solutions. The transient state will disappear faster for the wall stress than that for the velocity field. Comparing the results corresponding to different initial phases, the cosine case reaches to the steady state more rapidly than the sine case.

This work studies the natural convection heat and mass transfer near a horizontal cylinder of elliptic cross section with constant wall temperature and concentration in a fluid-saturated porous medium. A coordinate transformation is used to obtain the nonsimilar governing boundary layer equations. The transformed governing equations are then solved by the cubic spline collocation method. Results for the local Nusselt and Sherwood numbers are presented as functions of the Lewis number, the buoyancy ratio, and the aspect ratio when the major axis of the elliptical cylinder is vertical (slender orientation) and horizontal (blunt orientation). The heat and mass transfer rates of the elliptical cylinder with slender orientation are higher than those with blunt orientation.