Low-Cycle Fatigue Properties of Bimetallic Steel Bar with Buckling: Energy-Based Numerical and Experimental Investigations.

A bimetallic steel bar (BSB) consisting of stainless-steel cladding and carbon steel substrate exhibits excellent corrosion resistance and good mechanical properties. The bimetallic structure of BSBs may affect their low-cycle fatigue performance, and current investigations on the above issue are limited. In this study, the low-cycle fatigue properties of bimetallic steel bars (BSBs) with inelastic buckling were investigated. Experiments and numerical studies were conducted to investigate the low-cycle fatigue capacity for BSBs, considering buckling. The buckling mode of BSBs is discussed. The hysteretic loops and energy properties of BSBs with various slenderness ratios (L/D) and fatigue strain amplitudes (εa) are investigated. With increases in the L/D and εa, the original symmetry for hysteresis loops disappears gradually, which is caused by the buckling. A predictive equation revealing the relation between the εa and fatigue life is suggested, which considers the effects of the L/D. A numerical modelling method is suggested to predict the hysteretic curves of BSBs. The effect of buckling on the stress and energy properties of BSBs is discussed through the numerical analysis of 44 models including the effects of the L/D, εa, and cladding ratios. The numerical analysis results illustrate that the hysteresis loops of BSBs with various εa values exhibit similar shapes. The increase in the cladding ratio reduces the peak stress and the dissipated energy properties of BSBs. The hysteresis loop energy density decreases by about 3% with an increase of 0.1 in the cladding ratio. It is recommended that the proportion of stainless steel inBSBs should be minimized once the corrosion resistance requirements are met.

Effect of Superfine Cement Modification on Properties of Coral Aggregate Concrete.

In marine engineering, using corals as aggregates to prepare concrete can reduce both the exploitation of stones and the transportation cost of building materials. However, coral aggregates have low strength and high porosity, which may affect the workability and mechanical properties of concrete. Hence, superfine cement is used innovatively in this study to modify coral aggregates; additionally, the effects of the water-cement ratio and curing time on the water absorption and strength of modified coral aggregates are investigated. Modified coral aggregate concrete is prepared, and the effect of using modified superfine cement on its workability and strength is investigated. Experimental results show that when the water-cement ratio exceeds 1.25, the slurry does not form a shell on the surface of the coral aggregates and the water absorption of the coral aggregates increases significantly. The strength of the modified coral aggregates cured for a short duration is slightly lower than that of unmodified coral aggregates, whereas that cured for 28 days is approximately 20% higher than that of unmodified coral aggregates. Using superfine cement to modify coral aggregate concrete can improve its workability, but not its compressive properties.

Anti-Corrosion Reinforcements Using Coating Technologies-A Review.

Coated reinforcements are expected to improve the performance of reinforced concrete in aggressive environments, but different kinds of coated reinforcements can express a variety of properties, which can confuse researchers and engineers. This paper reviews the manufacture, corrosion mechanisms, behaviors, and applications of popular or promising coated reinforcements, incorporating galvanized reinforcements (GRs), epoxy coated reinforcements (ECRs), stainless cladding reinforcements (SCRs), and steel-fiber reinforced polymer composite bars (SFCBs). In terms of manufacture, GRs and ECRs should focus on minimizing the negative effect of manufacture on performance, while SCRs and SFCBs should reduce the cost and increase the production capacity. Behaviors of GRs and ECRs are primarily determined by the steel substrate, but the behaviors of SCRs and SFCBs are primarily affected by the coat and core, and their interaction. The corrosion mechanism of GRs and SCRs is about oxidation, while that of SFCBs is about hydrolysis. ECRs are usually corroded under film, which can be a cause of premature failure. Corrosion embrittles SCRs, as well as bare bars, but corrosion of SFCBs usually causes a reduction in maximum strength. The investigation of the corrosion behaviors of GRs and ECRs focuses on bond strength. GRs have controversial performance. ECRs have been proven to have drawbacks regarding bond strength. The use of anti-corrosion reinforcement is uneven in regions, which may correlate with the development of technology and the economy.

Design Suggestions on Resistance from Flange of Sorbite Stainless Steel Plate Girder under Shear.

A new S600E sorbite stainless steel (SS), which performs outstanding mechanical properties, was introduced in a plate girder to enhance the resistant performance and durability. The resistance from the flange for S600E sorbite SS plate girders developing post-buckling capacity was investigated through numerical analyses, which included the material and geometrical nonlinearity. The value of distance between plastic hinges performed significant effects on resistance from flange. There was a certain distribution range of the flange plastic hinge. Hence, it was difficult to determine the value of distance between plastic hinges accurately based merely on the failure behavior. Considering the theoretical basis of EN 1993-1-4: 2006+A1, the new methods to obtain resistance from the flange and determine the value of distance between the plastic hinges were proposed to avoid the aforementioned error. The parametric study was conducted to investigate the effect of key parameters on the resistance from the flange. To take the above effect into account, a correction factor was proposed for the design equation in EN 1993-1-4: 2006+A1 to predict the distance between flange plastic hinges accurately. The comparison was conducted to validate the accuracy of the proposed equations. The results indicated that the new modified equation could be used to predict the resistance from the flange of the S600E sorbite SS plate girder more accurately.

Effects of Polyoxymethylene Fiber on Fresh and Hardened Properties of Seawater Sea-Sand Concrete.

Seawater and sea sand are used in concrete to reduce the consumption of freshwater and river sand. To improve the mechanical properties and cracking resistance of concrete, polymer fiber is commonly used. In this study, polyoxymethylene (POM) fiber was innovatively applied to seawater sea-sand concrete (SWSSC), and the workability, early-age cracking behavior, and mechanical properties of SWSSC reinforced with POM fiber were investigated experimentally. A total of 6 kinds of SWSSC mixtures and 72 specimens were included. The test results indicated that with increases in fiber volume fractions (ρ), the workability of SWSSC decreased correspondingly. Compared with plain SWSSC, for SWSSC with ρ = 1%, the decreases in slump and expansibility were 110.6 and 91.9 mm, respectively. POM fiber had a significant enhancing effect on the early-age cracking resistance of SWSSC. Compared with those of plain SWSSC, the cracking indices ac, bc, and cc of the POM-1 specimen decreased by 77.0%, 89.4%, and 97.6%, respectively. Cube and axial compressive tests, splitting tensile tests, and flexural tests were conducted to clarify the effects of POM fiber on the mechanical properties of SWSSC. Compared with plain SWSSC, SWSSC with POM fiber performed better in terms of mechanical properties. Predictive equations were proposed to quantify the effects of POM fiber on the mechanical properties of SWSSC. The failure performances of the SWSSC specimens were discussed and their complete stress-strain curve was analyzed. A stress-strain model for SWSSC was suggested. According to the model, the complete stress-strain curve of SWSSC with any POM fiber content could be determined.

Effects of Polyoxymethylene Fiber on Mechanical Properties of Seawater Sea-Sand Concrete with Different Ages.

Workability and mechanical properties of the seawater sea-sand concrete (SWSSC) were similar to those of ordinary concrete made with freshwater and river sand, which had a wide application in structures. Since the polyoxymethylene (POM) fiber performed the outstanding alkali resistance and durability, POM fibers were added in SWSSC in this study to enhance the mechanical properties. Moreover, the mechanical properties of concrete during the early age have significant effects on the construction phase. The experiment, including 96 test specimens, was conducted to clarify effects of POM fibers on mechanical properties of SWSSC with different ages. The cube compressive, axial compressive, splitting tensile, and flexural tests of NF and POM0.6 SWSSC were conducted. Based on test results, the predictive equations were proposed to quantify relations between concrete age and mechanical properties of NF and POM0.6 SWSSC. Effects of the concrete age on ratios ftT/fcT and ffT/fcT were investigated and quantified through proposed equations. Failure performances of NF and POM0.6 SWSSC specimens with different ages were analyzed. The microstructure of POM0.6 SWSSC specimens was observed, and the reinforcing mechanism of POM fibers was further explained.

Concrete Elastic Modulus Experimental Research Based on Theory of Capillary Tension.

The risk of cracking in the early stage is a critical indicator of the performance of concrete structures. Concrete cracked when the tensile stresses caused by deformation under restraint conditions exceeded its tensile strength. This research aims at an accurate prediction of shrinkage cracking of concrete under constraints. Based on the theory of capillary tension under the concrete shrinkage mechanism, the method to test and compute the elastic modulus of a micro-matrix around the capillary, Et, was derived. Shrinkage and porosity determination tests were conducted to obtain the shrinkage values and confining stresses of concrete at different strength grades, different ages and under different restraint conditions, accordingly. Meanwhile, the proposed method of this research was used to obtain Et. The restraint stress given by Et was compared with the experimental result under the corresponding time. The results suggested a positive correlation between the elastic modulus of a micro-matrix around the capillary, Et, precomputed by the theory, and the static elastic modulus, Ec, and that the ratio between the two gradually decreased with the passage of time, which ranged from 2.8 to 3.1.

Mechanical Properties and Shrinkage Behavior of Concrete-Containing Graphene-Oxide Nanosheets.

Graphene oxide (GO) has been widely used as an additive due to its numerous unique properties. In this study, the compressive strength, flexural strength and elasticity modulus of concrete containing 0.02 wt%, 0.05 wt % and 0.08 wt % GO, and its dry shrinkage performance have been experimentally investigated. After the sample preparation, apparatus for compression test and flexural test were used to test the relevant properties of concrete containing GO. The dial indicators were used to measure the shrinkage of samples. The results indicate that GO can considerably improve the compressive strength, flexural strength, and elasticity modulus of concrete at the concrete age of 28 days by 4.04-12.65%, 3.8-7.38%, and 3.92-10.97%, respectively, which are substantially smaller than the increment at the age of 3 d by 5.02-21.51%, 4.25-13.06%, and 6.07-27.45% under a water-cement ratio of 0.35. It was also found that GO can increase the shrinkage strain of concrete. For example, at the age of 60 days, 0.02 wt%, 0.05 wt% and 0.08 wt% GO can increase the shrinkage strain of ordinary concrete by 1.99%, 5.79% and 7.45% respectively under a water-cement ratio of 0.49. The study has advanced our understanding on mechanical and shrinkage behavior of concrete containing GO.

Influence of Reinforcement Bars on Concrete Pore Structure and Compressive Strength.

In this research, the influence of reinforcement bars on concrete pore structure and compressive strength was experimentally investigated. Concrete samples with two mixture ratios and nine reinforcement ratios were provided. Tests were conducted on concrete pore structure and compressive strength at three ages (3 d, 7 d, and 28 d). It was found that reinforcement bars changed the concrete pore structure. In terms of size, the pore structure of concrete increased with the increase of reinforcement ratio. At the same age, concrete compressive strength in reinforced concrete specimens saw a gradual reduction when reinforcement ratio increased. A formula was proposed to calculate the compressive strength of concrete in reinforced specimens according to the strength of unreinforced concrete.

Modeling Shrinkage and Creep for Concrete with Graphene Oxide Nanosheets.

In this study, the shrinkage and creep of concrete containing graphene oxide (GO) nanosheets were experimentally and theoretically investigated. Experiments for the shrinkage and creep of concrete with 0.02% and 0.08% GO nanosheets by the weight of cement and common concrete were carried out. Subsequently, the influence of GO nanosheets on the shrinkage and creep of concrete was analyzed and discussed. A modified model was developed to accurately predict the shrinkage and creep of concrete containing GO nanosheets after models for predicting shrinkage and creep of common concrete were compared and the influential factors and application scope were determined. Results indicate that: (1) GO nanosheets can increase the shrinkage strain and reduce the creep coefficient of concrete, and (2) a modified ACI209 (92) model can accurately predict the shrinkage and creep of concrete containing GO nanosheets. Factors considering concrete strength can be introduced in the model to improve the model accuracy.

Influence of Steel Plates and Studs on Shrinkage Behavior and Cracking Potential of High-Performance Concrete.

To help designers develop solutions to overcome the cracking problem in steel-plate-reinforced concrete composite shear walls due to the concrete shrinkage, the influence of steel plates and studs on the shrinkage behavior of high-performance concrete (HPC), including restrained shrinkage strain, shrinkage strain gradient, and cracking potential, were theoretically and experimentally investigated in this study. A model for theoretical analysis was used to research the shrinkage performance of concrete that was restrained by steel plates and studs. The major parameters involved in the experiments include the thickness and material elastic modulus of the steel plate, in addition to the diameter, height, and number of studs. It was found that the shrinkage of HPC decreases and its potential cracking increases with the increase of thickness and elastic modulus of the steel plate, and the diameter, height, and number of studs. The restraining effect of the steel plate and stud on the HPC shrinkage decreases with the distance of their respective locations. It demonstrates that the HPC near a steel plate and stud is prone to crack compared with that far away from the steel plate and stud. This potential could be reduced by uniformly restraining the HPC.

Lipoprotein metabolism in an apoB-80 familial hypobetalipoproteinemia heterozygote.

OBJECTIVE: Familial hypobetalipoproteinemia (FHBL) is characterized by mutations in APOB, the majority of these causing protein truncations, and low plasma levels of apolipoprotein (apo) B. The hypobetalipoproteinemia may be due to enhanced clearance and possibly reduced production of apoB-containing lipoproteins; the mechanism may depend on the length of the apoB truncation. We studied fasting lipoprotein metabolism in an FHBL subject heterozygous for a mutation causing a truncated apoB, apoB-80. DESIGN AND METHODS: Very low density lipoprotein (VLDL)-, intermediate density lipoprotein (IDL)-, and low density lipoprotein (LDL)-apoB kinetics were determined in the fasting state using stable isotope methods and compartmental modeling. RESULTS: Compared with lean normolipidemic controls the apoB-80 FHBL subject had an elevated VLDL-apoB fractional catabolic rate and lower LDL production. ApoB production rates and IDL- and LDL-apoB fractional catabolic rates were not different. CONCLUSION: FHBL subjects heterozygous for a mutation truncating apoB to 80% of full-length are able to produce VLDL-apoB normally, but have rapid clearance of these particles, resulting in low levels of circulating apoB.

Lipoprotein Metabolism in APOB L343V Familial Hypobetalipoproteinemia.

CONTEXT: Familial hypobetalipoproteinemia (FHBL) is a codominant disorder of lipoprotein metabolism characterized by decreased plasma concentrations of low-density lipoprotein (LDL)-cholesterol and apolipoprotein B (apoB). OBJECTIVE: The objective was to examine the effect of heterozygous APOB L343V FHBL on postprandial triglyceride-rich lipoprotein (TRL) and fasting lipoprotein metabolism. METHODS: Plasma incremental area under the curve apoB-48 and apoB-48 kinetics were determined after ingestion of a standardized oral fat load using compartmental modeling. Very low-density lipoprotein (VLDL)-, intermediate-density lipoprotein (IDL)-, and LDL-apoB kinetics were determined in the fasting state using stable isotope methods and compartmental modeling. RESULTS: The postprandial incremental area under the curve (0-10 h) in FHBL subjects (n = 3) was lower for large TRL-triglyceride (-77%; P < .0001), small TRL-cholesterol (-83%; P < .001), small TRL-triglyceride (-88%; P < .001), and for plasma triglyceride (-70%; P < .01) and apoB (-63%; P < .0001) compared with controls. Compartmental analysis showed that apoB-48 production was lower (-91%; P < .05) compared with controls. VLDL-apoB concentrations in FHBL subjects (n = 2) were lower by more than 75% compared with healthy, normolipidemic control subjects (P < .01). The VLDL-apoB fractional catabolic rate (FCR) was more than 5-fold higher in the FHBL subjects (P = .07). ApoB production rates and IDL- and LDL-apoB FCRs were not different between FHBL subjects and controls. CONCLUSIONS: We conclude that when compared to controls, APOB L343V FHBL heterozygotes show lower TRL production with normal postprandial TRL particle clearance. In contrast, VLDL-apoB production was normal, whereas the FCR was higher in heterozygotes compared with lean control subjects. These mechanisms account for the marked hypolipidemic state observed in these FHBL subjects.

A pilot study of trimodality breast imaging surveillance in young women at high risk of breast cancer in Western Australia.

OBJECTIVE: To determine whether a surveillance program including clinical breast examination (CBE) and three screening modalities (magnetic resonance imaging [MRI], high-resolution ultrasound [U/S] and mammographic x-ray [MMX]) was feasible, and whether it could improve detection of pathological lesions in young women at high risk of developing breast cancer. DESIGN, SETTING AND PARTICIPANTS: Western Australian women aged 50 years or under at high risk of developing breast cancer were recruited to our study. For a 2-year period, they were offered breast MRI and U/S scans in addition to their annual MMX and CBE. Our study was conducted between June 2002 and October 2005. MAIN OUTCOME MEASURES: Number and type of cancerous or precancerous lesions; recall rates after screening; comparative sensitivity of screening modalities. RESULTS: Of 102 women approached, 72 agreed to participate. Fifteen lesions were detected, of which three were significant: a metastatic papillary cancer in an axillary lymph node, a borderline lesion (multiple papillomatosis with atypia), and a papilloma. All 15 lesions were visible on MRI, and four were detected by MRI only. Only one lesion was visible on all three imaging modalities. Nothing significant was detected by CBE. The recall rate after MRI scans fell from 9/72 (12.5%) in the first year to 5/67 (7.5%) in the second year. CONCLUSION: Our study gave valuable experience in a team approach to screening MRI, and showed that MRI can detect more lesions than MMX or U/S in women at high risk of developing breast cancer. Screening U/S may not add value to MMX and MRI screening, and we suggest a single oblique-view MMX may be used in some cases.

Adipose tissue compartments and insulin resistance in overweight-obese Caucasian men.

We examined the association between insulin resistance and adipose tissue compartments in overweight/obese men. Total intra-abdominal, intraperitoneal, retroperitoneal, total subcutaneous, anterior subcutaneous and posterior subcutaneous abdominal adipose tissue (PSAAT) masses (total intra-abdominal fat TIAATM, IPATM, RPATM, TSAATM, ASAATM and PSAATM, respectively) were quantified in 51 overweight/obese men using magnetic resonance imaging (MRI). Total adipose tissue mass (TATM) was also determined using bioelectrical impedance. Insulin resistance was estimated by homeostasis model assessment (HOMA) score. In univariate regression analysis, all fat compartments, with the exception of RPATM, were significantly and positively correlated with the HOMA score. The positive correlation between HOMA score and both IPATM and anterior subcutaneous adipose tissue mass was independent of obesity status. After adjusting total for TATM, only IPATM was significantly correlated with HOMA score (partial r=0.38, P<0.01). In stepwise regression, IPATM was the best predictor of HOMA score. In multivariate regression models including age, obesity status, non-esterified fatty acid (NEFAs) levels, triglycerides and energy expenditure, IPATM remained a significant positive predictor (P<0.05) of HOMA score. In overweight/obese men intraperitoneal AT is the fat compartment that best predicts the degree of insulin resistance. This association appears to be independent of age, total body fat mass and obesity status.

Elimination of COD, microorganisms and pharmaceuticals from sewage by trickling through sandy soil below leaking sewers.

To simulate the filtration and/or degradation of trickling sewage from leaky sewers through the non-water-saturated underground, sewage was trickled through sand of 0.4-2mm from the Rhine valley in glass columns of 125 cm length. For the same sewage the chemical oxygen demand (COD) removal was almost independent of low or high trickling rates. The COD removal efficiency varied, however, from 67% to 79%, for sewage from rain and dry weather periods, respectively. The water content of the moist sand increased from initially 80 ml kg(-1) with increasing sewage trickling rates to 108 ml kg(-1) sand. It remained at 108 ml kg(-1) at higher trickling rates higher than 600 ml d(-1). Analyses of effluent of five consecutive 25-cm soil columns revealed that about 50% of the initial COD were filtrated off on top of the sand or degraded in the uppermost 25 cm at varying trickling rates. Another 6-12% of the COD were removed in the following 25-50 cm of sand, whereas almost no further COD removal was seen in the subsequent two or three 25-cm columns. The COD elimination during trickling of sewage through the segmented column (interrupted random flow) was slightly better than that in the non-segmented column. Total and faecal coliform bacteria decreased faster with increasing trickling depth than that of total aerobic or anaerobic bacteria. After a filter/degradation stretch of 125 cm elimination of all bacteria reached 96.2-99.9%. The sewage contained low concentrations of at least 10 different pharmaceuticals or X-ray media. During trickling of sewage through sand, elimination of these compounds by adsorption onto sand and/or biodegradation varied from a complete removal, e.g. Ibuprofen or Naproxen, to almost no removal for several X-ray contrast media. Some of the medicals were removed as effectively as during conventional sewage treatment.

Fat compartments and apolipoprotein B-100 kinetics in overweight-obese men.

OBJECTIVE: To examine the association between the kinetics of very-low-density-lipoprotein (VLDL)-apolipoprotein B-100 (apoB) and intraperitoneal, retroperitoneal, subcutaneous abdominal, and total adipose tissue masses (IPATM, RPATM, SAATM, and TATM, respectively) in overweight/obese men. RESEARCH METHODS AND PROCEDURES: Hepatic secretion of VLDL was measured using an intravenous infusion of 1-[(13)C]-leucine in 51 men with a wide range of body mass index (25.1 to 42.2 kg/m(2)). Isotopic enrichment of VLDL-apoB was measured using gas chromatography-mass spectrometry and a multicompartmental model used to estimate VLDL-apoB metabolic parameters. IPATM, RPATM, and SAATM (kilograms) were quantified between T11 and S1 using magnetic resonance imaging; TATM (kilograms) was determined using bioelectrical impedance. Insulin resistance was estimated by homeostasis model assessment (HOMA) score. RESULTS: In stepwise regression, IPATM was the best predictor of hepatic secretion of VLDL-apoB (r = 0.390, p < 0.005) and TATM was the best predictor of VLDL-apoB fractional catabolic rate (r = 0.282, p < 0.05). IPATM remained significantly associated with VLDL-apoB secretion after adjusting for TATM or HOMA score (r = 0.360, p < 0.01 and r = 0.310, p < 0.05, respectively). This association was also independent of age, dietary intake, and body mass index. None of the fat compartments were significantly associated with the fractional catabolic rate of VLDL-apoB after adjusting for HOMA score. DISCUSSION: In overweight/obese men, the quantity of both IPATM and TATM determine the kinetics of VLDL-apoB. The effect of IPATM on VLDL-apoB secretion is independent of both total fat mass and the degree of insulin resistance.