Flexural Strength of Partially Concrete-Filled Steel Tubes Subjected to Lateral Loads by Experimental Testing and Finite Element Modelling

In this paper, the flexural strength and buckling of the partially concrete-filled steel tubes (PCFST) under laterally repeated loads was investigated through three-point bending test configuration. Three-dimensional Finite Element (FE) models of the bending tests of the PCFST were developed, in which the concrete filling was modelled using elastic-plastic-fracture model capturing crack development and the tube steel was modelled using elastic-plasticity model. The bond between concrete and tube was considered as frictional touching contact. The validation showed the FE results including the ultimate flexural load and buckling failure mode of the steel tube were in excellent agreement with the experimental ones. A parametric study was then conducted using the verified FE models to investigate the effects of the tube diameter-to-thickness ratio, the concrete filling length ratio, the compressive strength of concrete, and the tube steel’s yield and tensile strengths on the PCFST’s ultimate flexural strength. Based on this study, buckling modes, the optimal concrete filling lengths, and the confined compressive strengths of concrete were determined considering the effects of all these parameters. The confined compressive stresses and strains in concrete predicted by the FE models were evaluated against those determined by theoretical models. The results revealed that the effects of concrete compressive strength to the PCFST’s flexural capacity was insignificant while increasing the tube diameter-to-thickness ratio or the tube steel’s yield and tensile strengths could significantly increase the PCFST’s flexural capacity and the confined compressive strength of concrete; and there was an optimal length of concrete filling at about 66% of the tube length. It demonstrated that the Finite Element analysis can therefore be used as a powerful method to the analysis and design the PCFST columns under lateral loads

Design optimisation for cold rolled steel beam sections with web and flange stiffeners

This paper presents the analysis and design optimisation of the cold rolled steel sections for flexural strength considering the effect of cold working exerted on the section during the roll forming process. The sections included channel and zed shapes with complex longitudinal web and flange stiffeners. Nonlinear Finite Element (FE) modelling was developed to model the flexural strength of the channel and zed beams and validated against the four-point bending experiments for these sections. The material properties of steel at the section’s flat parts, corners, and stiffener bends were obtained from tensile tests and were incorporated into the FE simulations to account for the true material properties at these regions due to the cold working during the roll forming process. The strength enhancement at the section corners and stiffener bends obtained from tensile tests were also compared with the predicted values from design standards. The section strength was then optimised using FE modelling results based on the Design Of Experiments (DOE) and response surface methodology. Optimal designs for the channel and zed sections with maximum strength in distortional buckling could be obtained while changing the stiffeners’ position, shape, sizes, and considering true material properties at section corners and stiffener bends. It revealed that, for the two sets of channel and zed sections with the depths of 145 mm and 170 mm, the optimal designs provided up to 43% and 39% increase in flexural strength for the channel and zed sections, respectively; however, when the true material properties at the section corner and the stiffener’s bend regions was included, the increase in flexural strength increased up to 50% and 41%, respectively. Including flange stiffeners to the sections with longitudinal web stiffeners generally increased further the section strength. However, the levels of increase were largely dependent on the section depths and material properties

An Australian Fuel Substitution

Over the past ten years, the revenue collected by Australia's Commonwealth government from excises and royalties on liquid fuels has increased substantially. These revenues have risen from around six per cent of total taxation in 1975-76 to nearly 12.5 per cent in 1985-86, and from 43.6 per cent of total excise revenue to 76 per cent over the same period (Figure 1). The proportion of liquid fuels excise and royalties raised from each of crude oil and petroleum products has also varied considerably, and changed particularly dramatically during 1986-87 (Figure 2). These changes have been induced variously by movements in volumes produced and demanded and by policy decisions affecting import parity prices and tax rates. For example, it is clear from Figure 3 that the dramatic fall in crude oil revenue can be associated with falls in all three of the import parity price, the crude oil levy rate, and the production of indigenous crude. But in Figure 4, the corresponding substantial increase in products revenue is most closely aligned with an increased excise rate. A major general purpose of this paper is therefore to identify the principal aggregate and structural impacts which result from a substantial switch to petroleum products excise revenue from crude oil levy revenue. Industrial ·sector interfuel substitution effects are explicitly allowed for, under conditions of no net change in nominal or real liquid fuel tax receipts. Specific account is also taken of two important strands of the Australian government's pre-1988 oil regulatory framework, namely the import parity pricing (IPP) and domestic allocation systems for crude oil

Design optimisation for cold rolled steel beam sections with complex stiffeners considering cold working effects

This paper presents the analysis and design optimization of the cold rolled steel sections for flexural strength considering the effect of cold working exerted on the section during the roll forming process. The sections included channel and zed shapes with complex longitudinal web and flange stiffeners. Nonlinear Finite Element (FE) modelling was developed to model the flexural strength of the channel and zed beams and validated against the four-point bending experiments for these sections. The material properties of steel at the section’s flat parts, corners, and stiffener bends were obtained from tensile tests and were incorporated into the FE simulations to account for the true material properties at these regions. The section strength was then optimized using FE modelling results based on the Design of Experiments (DOE) and response surface methodology. Optimal designs for the channel and zed sections with maximum strength in distortional buckling could be obtained while changing the stiffeners’ position, shape, sizes, and considering material properties at section corners and stiffener bends. It revealed that, the optimal designs provided up to 13% and 17% increase in flexural strength for the channel and zed sections, respectively; however, when the true material properties at the section corner and the stiffener’s bend regions was included, the increase in flexural strength increased up to 20% and 23%, respectively

Sulfur management strategies to improve partial sulfur balance with irrigated peanut production on deep sands

Sands have favourable physical properties for harvesting peanut, but improving S and water use efficiency on these soils remains a challenge. We studied partial S balance in irrigated peanut crops on sands of Central Vietnam to identify key factors of S fertiliser management affecting S inputs and outputs. Field trials were conducted in the spring seasons of 2015 and 2016 to determine the effects of S application rates (0, 15, 30, 45 kg ha−1) on peanut yield and partial S balance. Sulfur balances were negative (-28.3 to 5.6 kg S ha−1) at rates < 30 kg S ha−1, while at higher rates of S fertiliser application that produced maximum pod yield (30 - 45 kg S ha−1), three of four sites showed neutral to slightly positive S balance (1.5 - 5.6 kg S ha−1). The negative partial S balance decreased with increasing S rates but was mostly attributable to the large S removal in peanut shoots (9.7 - 22.3 kg S ha−1) which are used on farms for animal feed. The negative partial S balance results in depletion of soil S reserves and hence efficient recycling of S on farms is critical for sustainable crop production on sands of VN

Influences of cold working on tensile and bending strength of cold roll formed steel sections contain complex folded-in stiffeners

This paper aims to study the cold working influences on material and structural properties of the cold roll formed steel sections contain complex longitudinally stiffeners under bending. Tensile tests on flat and curved samples extracted from the complex stiffeners of channel and zed sections were conducted to investigate the change of material properties due to cold working during the roll forming process. The influences of cold working in the section flat regions, corners and stiffener bends were investigated and evaluated against some predictive models in literature studies. Nonlinear Finite Element modelling was developed to model the four-point bending tests to study the effects of cold working on the buckling and ultimate strengths of channel and zed sections. In the bending models, experimental material properties of section flat parts, corners and stiffener bends were implemented to search for the optimal shapes of the sections. Significant improvements were obtained for the section strength of the optimized sections in comparison to the original sections. Optimal shapes for the channel and zed sections with maximum strength in distortional buckling could be obtained while changing the stiffeners’ position, shape, sizes, and considering the effect of cold working. It revealed that, the optimal sections provided up to 13% and 17% increase in bending strength for the channel and zed section, respectively; however, when the effect of cold working at the section corner and the stiffener’s bend regions was included, the increase in bending strength increased up to 20% and 23%, respectively.We would like to acknowledge the University of Derby for providing the sponsor of this work [PGTA Studentship - E&T_14_PGTA_0717]. The tensile tests were carried out at the University of Sheffield

Proximity effects and Andreev reflection in mesoscopic SNS junction with perfect NS interfaces

Low temperature transport measurements on superconducting film - normal metal wire - superconducting film (SNS) junctions fabricated on the basis of 6 nm thick superconducting polycrystalline PtSi films are reported. The structures with the normal metal wires of two different lengths L=1.5 $\mu$m and L=6$\mu$m and the same widths W=0.3$\mu$m are studied. Zero bias resistance dip related to pair current proximity effect is observed for all junctions whereas the subharmonic energy gap structure originating from phase coherent multiple Andreev reflections have occurs only in the SNS junctions with short wires.Comment: ReVTex, 4 pages, 4 eps figures include

Skin lesion segmentation method for dermoscopic images with convolutional neural networks and semantic segmentation

Melanoma skin cancer is one of the most dangerous forms of skin cancer because it grows fast and causes most of the skin cancer deaths. Hence, early detection is a very important task to treat melanoma. In this article, we propose a skin lesion segmentation method for dermoscopic images based on the U-Net architecture with VGG-16 encoder and the semantic segmentation. Base on the segmented skin lesion, diagnostic imaging systems can evaluate skin lesion features to classify them. The proposed method requires fewer resources for training, and it is suitable for computing systems without powerful GPUs, but the training accuracy is still high enough (above 95 %). In the experiments, we train the model on the ISIC dataset – a common dermoscopic image dataset. To assess the performance of the proposed skin lesion segmentation method, we evaluate the Sorensen-Dice and the Jaccard scores and compare to other deep learning-based skin lesion segmentation methods. Experimental results showed that skin lesion segmentation quality of the proposed method are better than ones of the compared methods.This research was funded by University of Economics Ho Chi Minh City, Vietnam

Results of the BiPo-1 prototype for radiopurity measurements for the SuperNEMO double beta decay source foils

The development of BiPo detectors is dedicated to the measurement of extremely high radiopurity in $^{208}$Tl and $^{214}$Bi for the SuperNEMO double beta decay source foils. A modular prototype, called BiPo-1, with 0.8 $m^2$ of sensitive surface area, has been running in the Modane Underground Laboratory since February, 2008. The goal of BiPo-1 is to measure the different components of the background and in particular the surface radiopurity of the plastic scintillators that make up the detector. The first phase of data collection has been dedicated to the measurement of the radiopurity in $^{208}$Tl. After more than one year of background measurement, a surface activity of the scintillators of $\mathcal{A}$($^{208}$Tl) $=$ 1.5 $\mu$Bq/m$^2$ is reported here. Given this level of background, a larger BiPo detector having 12 m$^2$ of active surface area, is able to qualify the radiopurity of the SuperNEMO selenium double beta decay foils with the required sensitivity of $\mathcal{A}$($^{208}$Tl) $<$ 2 $\mu$Bq/kg (90% C.L.) with a six month measurement.Comment: 24 pages, submitted to N.I.M.

Spectral modeling of scintillator for the NEMO-3 and SuperNEMO detectors

We have constructed a GEANT4-based detailed software model of photon transport in plastic scintillator blocks and have used it to study the NEMO-3 and SuperNEMO calorimeters employed in experiments designed to search for neutrinoless double beta decay. We compare our simulations to measurements using conversion electrons from a calibration source of $\rm ^{207}Bi$ and show that the agreement is improved if wavelength-dependent properties of the calorimeter are taken into account. In this article, we briefly describe our modeling approach and results of our studies.Comment: 16 pages, 10 figure