Effect of Skew Angles on Longitudinal Girder and Deck Slab of Prestressed Concrete T Beam Girder Bridges

The present paper shows the effects of varying skew angles on pre-stressed concrete (PSC) bridges using finite elemental method. Studies are carried out on PSC bridge decks to understand the influence of skew angle and loading on behaviour of bridges. The results of skewed bridges are compared with straight bridges for IRC Class AA Tracked loading. Also, a comparative analysis of the response of skewed PSC Slab Bridge decks with that of equivalent straight bridge decks is made. The variation of maximum longitudinal bending moment (BM), maximum transverse moment, maximum torsional moment, and maximum longitudinal stresses deflection at obtuse corner, acute corner with skew angles are studied for bridge deck. It is found that Live load longitudinal bending moments decreases with an increase in skew angle, whereas a maximum transverse moment and maximum torsional moment increases with an increase in skew angle. The benefit of pre-stressing is reflected in considerable decrease in the longitudinal bending moment, transverse moment and longitudinal stresses. The models are analysed with the help of software CSI-Bridge V 20 Version. Keywords: Skew angle effect, Longitudinal moment, Transverse moment, CSI- Bridge software, Deck slab, Finite element method.

Increasing the longitudinal bending stiffness of runners’ habitual shoes: An appropriate choice for improving running performance?

This study analysed the effects of increasing the longitudinal bending stiffness (LBS) of runners’ habitual shoes on the metabolic energetic demand, lower limb muscle activation and stride spatiotemporal parameters during a prolonged running session through classical group investigation, as well as a more individualised approach. Eleven recreational male participants ran overground for 40 min at 95% of their ventilatory anaerobic threshold with their own shoes or their shoes with higher LBS (stiff carbon plate inserted under insole). The net energetic cost of running, lower leg muscle activation and spatiotemporal parameters were measured during the prolonged running. The variables of interest were analysed for 1 min in seven time intervals. There were no main effects of LBS or interaction effects with running duration on the group averaged variables. Overall, the participant-specific metabolic effects induced by an increased shoe LBS were not beneficial. Beneficial metabolic effects were more likely to occur when the increased LBS induced a decrease or no change in the ground contact time relative to their habitual shoes, as well as for taller runners. Increasing the LBS in runners’ habitual shoes did not induce systematic metabolic effects for all the runners and may not be beneficial for performance purposes if the runners’ shoe habits were too disrupted.

An Investigation into the Effect of Rolling Reduction on 3D Curved Parts Rolling Process

Rolling technology based on arc-shaped rollers is a novel method for rapid manufacturing of 3D curved parts. The method uses a pair of arc-shaped rollers (a convex roller and a concave roller) as forming tools, forming an unevenly distributed roll gap. The sheet metal has both transverse bending and longitudinal uneven extension during rolling, so that surface parts with double curvature are processed. The curvature of the formed surface part can be changed by changing the rolling reduction. Changing the vertical distance between the rollers will cause the overall change of the roll gap height, which will inevitably have a great impact on the forming effect of formed 3D curved parts. In this paper, a finite element model and experiment with different rolling reductions was designed; the influence of rolling reduction on the bending deformation and shape accuracy of formed 3D curved parts was studied. The results show that, with the slight increase of rolling reduction (from 0.04 to 0.12 mm), the longitudinal bending deformation of the formed 3D curved part increases significantly, but its transversal bending is almost not affected. When the maximum rolling reduction is 0.04 and 0.06 mm (the corresponding minimum rolling reduction is less than or equal to zero), the shape accuracy of the formed 3D curved parts is not good enough; when the maximum rolling reduction is greater than 0.06 mm (the corresponding minimum rolling reduction is greater than zero), the shape accuracy of the formed 3D curved parts is significantly better. This indicates that, for the rolling of 3D curved parts based on arc-shaped rollers, ensuring that the minimum rolling reduction is greater than zero is the key to ensuring good shape accuracy of the formed 3D curved parts.

Comparison and analysis of electroacoustic characteristics of high power density compact low frequency hydroacoustic transducers

Typical features and principal differences of electroacoustic characteristics and impedance spectra of compact low-frequency hydroacoustic piezoelectric radiators of high power-density to-weight ratio of the longitudinal-bending, oncoming-piston and inertial-bending types are presented in the paper. Analysis and comparison of electroacoustic characteristics of differ-ent types transducers allow to clear the direction of design search. This is also important to specify technical solutions to overcome contradictions between compact dimensions, band-width, sensitivity, low resonance frequency and efficiency of hydroacoustic radiators. Using the considered types of transducers for different classes of hydroacoustics applications are suggested.