For a bi-linear SDOF system subjected to a specific wave form of the ground acceleration, the unique yielding pseudo spectral acceleration and spectral displacement (Say, Sdy) together with various inelastic responses (Sai, Sdi) can be obtained via nonlinear time history analyses, respectively, by tuning the different levels of peak ground acceleration as various input ground motions. Meanwhile, the corresponding elastic responses (Sae, Sde) of a linear SDOF system with the identical mass, viscous damping and elastic stiffness as those of the bi-linear one can also be determined through linear time history analyses under the same excitations. The proposed NSAD format shown on the diagram of the elastic force ratio, Ω=Sae/Say I Say, versus the ductility ratio, (μ= (Sdi/Sdy), is a dimensionless plot of the seismic demands suitable to the engineers who are familiar with the conventional force-based design using linear structural analysis. In this paper, more than two hundred ground motions recorded in the Chi-Chi earthquake, Taiwan (1999) were chosen as the seismic inputs for the establishment of the NSAD format. The characteristics and applications of the NSAD format on the performance-based seismic design of the bridge structures were discussed, and realistic procedures for the methodology were proposed.

The results obtained shows that the NSAD format can help the engineers evaluate the multiple-level seismic demands not only with a well precision but also with a great convenience.

In this paper, a general matrix cracking model including the effect of fiber/matrix debonding in the crack wake is developed for a unidirectional fiber reinforced composite. The debonding mechanics is incorporated into matrix cracking model by treating the crack-wake debonding as a particular crack propagation problem along the interface. Then, the closed-form analytical solution of the critical stress for the onset of widespread matrix cracking is derived, based on the analysis of steady state crack growth in the matrix. The fracture mechanics approach adopted in the present analysis is compared with the analysis in which the crack-wake debonding mechanics was modeled by energy balance approach. The conditions for attaining no-debonding and debonding as onset of widespread matrix cracking are discussed in terms of the interfacial properties of debond toughness and frictional shear stress. The theoretical results are compared with experimental data that are available in the literature.

Experiments were made with 14 MEMS sensors situated along the span of a circular cylinder whose aspect ratio was 5. The signals of the MEMS sensors were sampled simultaneously as flow over the cylinder at Reynolds numbers of 104. The results of Wavelet analysis of the signals indicate that the percentage of time during which strong three-dimensionality of vortex shedding was detected is about 10%.As noted, strong three-dimensionality took place when the fluctuating amplitude of the signals was severely modulated and the vortex shedding frequency reduced appeared abnormally high or low. Further noted was that the addition of a splitter plate of 0.5 or one diameter in length behind the circular cylinder was not able to suppress the three-dimensionality of the flow.

This paper is to present the design and development of a piezoelectric actuator for SPM in ultrahigh vacuum (10−7∼10−9 Torr). The measuring probe is installed on a precise scanning actuator, which is further driven by a fast approaching actuator. The precise scanning actuator composed of a piezo-tube with segmented electrodes can realize 3-D precise scanning motions at subnanometer level to move the measuring probe over the measured surface. Because of its stable and smooth actuating behavior, the inchworm actuating principle is selected for the fast approaching actuator, which is build up with two controllable clamping devices and an actuating device. Diverse flexure mechanisms are applied in the actuator to attain frictionless guiding and recovery functions. To realize balanced clamping forces on the scanning tube, each clamping device is integrated with a fine regulating mechanism for clamping force. By applying the theoretical model and the finite element analysis, the relations between force and deflection inside the actuator were investigated to validate its function. The developed actuator has sustained the severe baking and pumping process, and their function and performance were verified experimentally in ultrahigh vacuum.

The paper investigates the hydromagnetic stability theory of a thin electrically conductive fluid film flowing down along the outside surface of a vertical cylinder. The long-wave perturbation method is employed to solve for generalized kinematic equations with free film interface. The normal mode approach is used to compute the stability solution for the film flow. The modeling results display that the degree of instability in the film flow is further intensified by the lateral curvature of cylinder. This is somewhat different from that of the planar flow. It is also observed that by increasing the effect of the magnetic field and increasing the radius of the cylinder the film flow can become relatively more stable as traveling down along the vertical cylinder.

A material function of endochronic theory is proposed for investigating the plastic behaviors of material. Depending on the material parameters properly chosen, the present model can be classified into four categories, and is appropriate for describing various materials behaving cyclic strain hardening inherently with respect to the deformation history. Experimental verification of the theory was demonstrated using the experimental results of Shiao [1] and Lamba and Sidebottom [2]. The theory is in good agreement with experimental results obtained by Shiao [1] through comparing the stress-strain hysteresis loops of SAE 4340 steel under axisymmetrically cyclic loading condition with various amplitudes. In addition, the present model is shown to be capable of describing the behavior of erasure of memory of materials, as experimentally observed by Lamba and Sidebottom [2].

In this paper, a locally implicit scheme on unstructured dynamic meshes is presented to study transonic turbulent flows over vibrating blades with positive interblade phase angle. The unsteady Favre-averaged Navier-Stokes equations with moving domain effects and a low- Reynolds-number k-ε turbulence model are solved in the Cartesian coordinate system. To treat the viscous flux on quadrilateral-triangular meshes, the first-order derivatives of velocity components and temperature are calculated by constructing auxiliary cells and Green's theorem for surface integration is applied. The assessment of accuracy of the present scheme on quadrilateral-triangular meshes is conducted through the calculation of the turbulent flow around an NACA 0012 airfoil. Based on the comparison with the experimental data, the accuracy of the present approach is confirmed. From the distributions of magnitude of the first harmonic dynamic pressure difference coefficient which include the present solution and the related experimental and numerical results, it is found that the present solution approach is reliable and acceptable. The unsteady pressure wave, shock wave and vortex-shedding phenomena are demonstrated and discussed.

A soil-structure system associated with a semi-infinite structure such as tunnel or pavement is usually investigated by finite element analysis. If the boundary of the finite element model selected is not far enough from the excitation source or does not have an appropriate energy-absorption mechanism, it may introduce a significant error induced by reflected waves. This study develops a structural transmitting boundary to absorb the transmitting energy at the boundary of the analytical model. The structure is divided into finite and semi-infinite regions. The stiffness of the semi-infinite region is established by the principle of virtual work and applied at the transmitting boundary. The comparisons of the structural displacements induced by vertical harmonic excitations show that the analytical model size can be significantly reduced, if the proposed transmitting boundary is used to simulate the semi-infinite structural region.

An analytical model for determining the shear strength of concrete pile caps under the failure mode of diagonal-compression originally based on the softened strut-and-tie model is proposed. The failure probabilities of reinforced concrete pile caps are investigated by Monte Carlo method. The results indicate that the proposed model can accurately predict the shear strength of the pile caps. The distribution of the failure probabilities for pile caps designed to ACI 318-02 Appendix A and the proposed design method are more uniform than that designed to the ACI 318-99. The ACI 318-99 is very conservative and cannot provide a consistent safety for pile caps design. It is suggested that the procedures in the ACI 318-02 Appendix A should be moved to the main body of ACI 318-02 and the proposed design method should be incorporated into the current reinforced concrete pile cap design methods.

In this paper, an exergetic efficiency optimization method that combines the concept of exergy and finite-time thermodynamic theory is developed to analyze an irreversible heat engine. With the total thermal conductance constraint, the analytical solutions of optimal allocation of thermal conductance and the corresponding maximum exergetic efficiency, thermal efficiency, as well as operating temperatures of hot and cold sides are obtained under a fixed overall heat supply rate. The results show that the exergetic efficiency optimization method can effectively analyze an irreversible heat engine.