Dynamic and Impact Behavior of Half-Through Arch Bridges

The objective of this paper is to present the results of an investigation of the dynamic and impact characteristics of half-through arch bridges with rough decks caused by vehicles moving across them. Seven arch bridges modeled as three-dimensional structures with overall span lengths ranging from 20?to?200?m (65.5?to?656.2?ft) are analyzed. The American Association of State Highway and Transportation Officials Specifications HS20-44 truck is the applied vehicle loading used in the analysis and is simulated as a three-dimensional, nonlinear vehicle model with 11 degrees of freedom. Truck components include the body, suspension, and tires. The bridge deck surface is assumed to have a “good” surface roughness and is simulated using a stochastic process (power spectral density function). The effect on impact factors of span length, rise-to-span ratio, and vehicle speed is discussed. The results of the analyses show that the impact factors of bending moment and axial force will not exceed 0.4 and 0.25, respectively. The proposed impact equations are simple and conservative and can be used in the design of half-through arch bridges.     

Effect of a circumferential feeding groove on fluid force in short squeeze film dampers

The present work studies fluid forces in a squeeze film damper with a circumferential feeding groove. The groove is taken as a special damper to analyse fluid forces. The dynamic performance of the squeeze film damper is attributed to the special damper, two film lands, and their interactions. From this viewpoint, dynamic effects in the groove are studied based on linearized Navier-Stokes equations to consider effects of variations of fluid velocity and pressure in the groove on forces in the damper. Investigations on film lands are conducted by using a simplified Navier-Stokes equation to include fluid inertia. Then, the two part analyses are combined together by studying the interactions of the flow and the pressure between the groove and film lands from the continuity condition and a Navier-Strokes equation, resulting in new models for force predictions. The new models are compared with experimental results and published work. Comparisons show the new models give better predictions and correlation with experimental data than traditional theory. The new models give a significant improvement on results obtained by traditional theory, especially for tangential force. Based on the new models, the effects of the groove on fluid forces are studied.     

Estimation of cutting forces and surface roughness for hard turning using neural networks

Metal cutting mechanics is quite complicated and it is very difficult to develop a comprehensive model which involves all cutting parameters affecting machining variables. In this study, machining variables such as cutting forces and surface roughness are measured during turning at different cutting parameters such as approaching angle, speed, feed and depth of cut. The data obtained by experimentation is analyzed and used to construct model using neural networks. The model obtained is then tested with the experimental data and results are indicated.     

Effects of Missile Size and Glass Type on Impact Resistance of “Sacrificial Ply” Laminated Glass

Experiments were performed as part of a larger study to develop the “sacrificial ply” design concept for laminated architectural glass. This concept allows windborne debris impacts in severe windstorm environments to break the outer laminated architectural glass ply while the inner ply is preserved in order to carry the design wind pressure. Steel ball size and inner/outer glass ply type (level of thermal tempering) were varied to determine their effects on the impact resistance of the inner glass ply of laminated architectural glass when impacted on the outer glass ply. A mean minimum breakage velocity (MMBV) was determined for each variation in steel ball size and glass temper level, which defines the mean debris impact velocity on the outer glass ply that causes breakage in the inner glass ply. A 46% reduction in MMBV was observed for an increase in steel ball size from 2 g (7.9 mm diameter) to 8.4 g (12.7 mm diameter), and a 65% reduction in MMBV was observed for an increase in steel ball size from 2 g (7.9 mm diameter) to 28.2 g (19.1 mm diameter). Laminated architectural glass constructed with heat-strengthened or fully tempered inner glass plies, regardless of outer-glass-ply type, was found to have a significantly higher MMBV than laminated architectural glass constructed with annealed glass plies. In contrast, changing the outer glass ply from annealed to fully tempered glass was found to reduce the MMBV, regardless of the inner glass ply type. Relating these results to those in a previous impact study by Kaiser et al. suggests that the order of importance for design variables that most influence the inner glass ply impact resistance of sacrificial ply laminated architectural glass is the following, starting with the most important: (1) inner glass ply type; (2) inner glass ply thickness; (3) polyvinyl butyral (PVB) interlayer thickness; and (4) outer glass ply thickness.     

Friction and Adhesion Hysteresis between Surfactant Monolayers in Water

We briefly review the model that correlates friction between two surfaces in adhesive contact with the loading-unloading adhesion hysteresis between them. We then examine in light of this model the observed low friction between two mica surfaces coated with a double-chained quaternary ammonium surfactant in intimate adhesive contact in water. This enables us to propose a mechanism for surfactant boundary lubrication in water that is rather different from the classic boundary lubrication in air: in this mechanism, adhesion takes place at the interface between the opposing surfactant hydrocarbon tails, whereas frictional sliding takes place at the interface between the hydrated surfactant headgroups and mica. The implications of our findings to biolubrication processes are discussed.     

Globalisation and local resistance: Alternative city developmental scenarios on capital's global frontier—the case of Yalova,Turkey

Today, defining objectives and setting priorities at local level becomes more and more difficult as the nature and direction of urbanisation is increasingly influenced by global economic integration and the struggle of countries, and indeed, individual cities, to be competitive in the global marketplace (Cohen, 2004). In general, local strategies have to be formed and reformed, based on the logic of macro-level factors as to what is, or is not, feasible, and actors’ responses and political judgments about which values and interests they most wish to promote.     

Application of computer in hot forging

The research to establish a foundation for metal forging industry was done to gather the data concerning the shape of forging products in domestic factory. The products were classified into three categories with respect to die manufacturing and forging, namely, simple, medium, and complex. Forging process from the initial step of receiving order until final inspection before shipment was studied, Parameters, formula and data were explained along side of each step for the application in actual situation. Furthermore, C-language computer program to calculate forging force was developed. Two types of products were forged and the data collected were used to calculate the multiplication factor C by the formula P=C • σ_m • A. The C values from tested results were in good agreement with the previous research’s work. It can be concluded that the developed program can be used to calculate and estimate forging force in order to select a suitable forging machine in the factory.     

The effect of extremely low lubricant volumes in machining

Cost, the effect on the environment, and health issues are all relevant when considering the choice of a lubricant and application system in a modern metal cutting process. The need to use less, limit the disposal and operator contact are all now very important. This paper shows the results of preliminary tests using very low quantities (200–300 ml h⁻¹) of lubricant when machining steel. The low quantities were applied in a fast flowing air stream. The results are compared to traditional flood cooling as a benchmark with 5.2I min⁻¹. The results show that surface finish, chip thickness and force variation are all affected beneficially with the low coolant volume compared to flood cooling.     

Controlling bubble size using a frit and sleeve sparger

This paper describes a frit and sleeve sparger designed to control the size of bubbles produced. The design comprises a porous ring (frit) surrounded by a sleeve through which water is passed to generate shear. A prototype is described and results confirm that bubble size can be controlled independent of gas velocity and is governed by the shear in the annular gap between the frit and sleeve independent of gap size.