Numerical Simulation-Based Analysis of the Impact of Overloading on Segmentally Assembled Bridges

Segmentally assembled bridges are increasinglyfinding engineering applications in recent years due to their unique advantages,especially as urban viaducts.Vehicle loads are one of the most important variable loads acting on bridge structures.Accordingly,the influence of overloaded vehicles on existing assembled bridge structures is an urgent concern at present.This paper establishes thefinite element model of the segmentally assembled bridge based on ABAQUS software and analyzes the influence of vehicle overload on an assembled girder bridge struc-ture.First,afinite element model corresponding to the target bridge is established based on ABAQUS software,and the load is controlled to simulate vehicle movement in each area of the traveling zone at different times.Sec-ond,the key cross-sections of segmental girder bridges are monitored in real time based on the force character-istics of continuous girder bridges,and they are compared with the simulation results.Finally,a material damage ontology model is introduced,and the structural damage caused by different overloading rates is compared and analyzed.Results show that thefinite element modeling method is accurate by comparing with on-site measured data,and it is suitable for the numerical simulation of segmental girder bridges;Dynamic sensors installed at 1/4L,1/2L,and 3/4L of the segmental girder main beams could be used to identify the dynamic response of segmental girder bridges;The bottom plate of the segmental girder bridge is mostly damaged at the position where the length of the precast beam section changes and the midspan position.With the increase in load,damage in the direction of the bridge develops faster than that in the direction of the transverse bridge.Thefindings of this study can guide maintenance departments in the management and maintenance of bridges and vehicles.

Overloading of Landing Based on the Deformation of the Lunar Lander

Along with the progress of sciences and technologies, a lot of explorations are taken in many countries or organizations in succession. Lunar, the natural satellite of the earth, become a focus of the space discovery again recently because of its abundant resource and high value in use. Lunar exploration is also one of the most important projects in China. A primary objective of the probe in lunar is to soft-land a manned spacecraft on the lunar surface. The soft-landing system is the key composition of the lunar lander. In the overall design of lunar lander, the analysis of touchdown dynamics during landing stage is an important work. The rigid-flexible coupling dynamics of a system with flexible cantilevers attached to the main lander is analyzed. The equations are derived from the subsystem method. Results show that the deformations of cantilevers have considerable effect on the overloading of the lunar lander system.

Study on Crack Closure Considering Welding Residual Stress Under Constant Amplitude Loading and Overloading

Welding residual stress in the engineering structure has a non-negligible influence on crack propagation,and crack closure is a significant factor affecting the crack propagation.Based on the elastoplastic finite element method and crack closure theory,we studied crack closure and residual compressive stress field of butt-welded plates under constant amplitude loading and overloading regarding the stress ratio,maximum load,overload ratio,and number of overloads.The results show that the welding residual tensile stress can decrease the crack closure because of a decrease in the residual compressive stress in the wake zone,but the effect is gradually reduced with increased stress ratio or maximum load.And the combined effect of welding residual tensile stress and overload can produce a stronger retardation effect on crack propagation.

Study of the structure and architecture of aortic smooth muscle cells under pressure overloading in rats

Male Wistar rats were used to study the changes of the structure and architecture of the smooth muscle cells(SMCs) of the aorta under pressure overloading(PO).The aorta was cut open longitudinally and the tunica media was examined with a histological tech

EFFECT OF NON-PROPORTIONAL OVERLOADING ON FATIGUE CRACK GROWTH

The effect of proportional and non-proportional overloading on mode l fatigue crack growth have been studied,and the influences of crack tip plastic zone,crack tip blunting as well as crack closure were discussed.Proportional(model I)overloading may cause more serious crack growth retardation than non-proportional(mixed mode)overloading.Therefore,for estimating the fatigue life of engineering structures to simplify a real overload which may of- ten be non-proportional as a proportional one is not always safe.

Overloading and Pavement Service Life <br/>—A Case Study on Narayanghat-Mugling Road, Nepal

The ability of a pavement structure in carrying out its function reduces in line with the increase of traffic load, especially if there are overloaded heavy vehicle passing through the road. This study was done to know the effect of overloading vehicles on the road pavement and remaining service life of the pavement. In this study, the service life of pavement due to overloaded vehicles was analyzed using the AASHTO 1993. In Narayanghat-Mugling road the composition of traffic seems to be 83.76% heavy vehicles, 9.18% medium vehicle and 7.05% light vehicle. For the direction of Narayanghat-Mugling, the pavement service life might be reduced by 59.90% due to overloading condition, while for the opposite direction, the service life would not reduced caused by the same factor. The impact of overload conditions on the road pavement showed premature failure;that is, a condition which the damage reduced the life of roads before the design life of the road is reached. From the results, it can be concluded that overloaded vehicles on the road are very influential to the reduction in pavement service life. Therefore, it is expected that road users to comply with existing regulations in the conduct of transportation. As overloading is increasing, it has to be controlled by rules and regulations with penalty to control the overloading. So fines must be associated with intensified enforcement when considered in further strategy. Regular monitoring, inspection and enforcement are the effective ways to control overloading. Use of technology (Automatic overloading information system) may be the effective way to control the overloading.

OCDMA/OCDMA Overloading Scheme for Cellular DS-CDMA Using Orthogonal Gold Codes and Complex Scrambling

Overloading is a method to extend capacity limitation of multiple access techniques. The system becomes overloaded, when the number of users exceeds the signal dimensions. One of the efficient schemes to overload a CDMA system is to use two sets of orthogonal signal waveforms (O/O). In this paper, the BER performance of a new overloading scheme using scrambled orthogonal Gold code (OG/OG) sets is evaluated with soft decision interference cancellation (SDIC) receiver. When complex scrambling is not used, it is shown that OG/OG scheme provides 25% (16 extra users) channel overloading for synchronous DS-CDMA system in an AWGN channel, with an SNR degradation of about 0.35 dB as compared to single user bound at a BER of 1e-5. We have evaluated the overloading performance, when two set are scrambled with set specific deterministic or random complex scrambling sequence. It is shown that the amount of overloading increases significantly from 25% to 63% (40 extra users) by using random complex scrambling for N=64. For deterministic (periodic) scrambling, the overloading percentage increases considerably to 78. On a Rayleigh fading channel, an overloading of 40% is obtained without scrambling at a BER of 5e-4 with near single user performance. With complex scrambling overloading % increases considerably to 100%.

Evolution of the Deflection According to Truck Overloading—Comparison between Benkelman Beam Method and FEM of Lateritic Pavements

The study of the deflection due to the passage of an axle on a pavement structure has the advantage to make possible to pronounce on the portance, the rigidity and the homogeneity of this one. In the case where the allowed axle load is not respected, surface deflection leads to premature deterioration of the roadway. In order to study the evolution of these deformations, deflection measurements were made by using the Benkelman method in the Fatick-Kaolack road in Senegal by varying the axle load with the following values: 10, 13 and 16 tons on three different zones. The results show a linear evolution of the deflection as a function of the axle load. Also, the impact of truck overloading was studied by considering different values of the axle load with comparison to the allowed axle load by using frequent types of vehicle. A numerical simulation of the Cast3M pavement was done first, in the case of an isolated single wheel with a radius of 12.5 cm, then in the case of an equivalent dual wheel with a radius of 18.1 cm for loads of 10 to 19 tons. In the same way, the pavement design software (ALIZE) is used to analyse the variation of the axle load. The results show a linear evolution of the deflection, which corroborates the measurements made in the field and those obtained by Samb (2014) with a slope coefficient equal to 1.7. Nevertheless, the case of an isolated single wheel of 12.5 cm radius is closest to the measurements with a straight line of slope coefficient equal to 1.9.

Evaluation of the Impact of Truck Overloading on Flexible Compacted Gravel Lateritic Soil’s Pavements by FEM with Cast3M^&copy;

Within the framework of a FEM of the nonlinear behavior of lateritic pavement of Senegal, the effect of truck overloading is studied to estimate its impact on the deformability of road pavement on compacted gravel lateritic soils. For that purpose, various loading conditions were tested to measure the impact on the critical response parameters of road pavement design. The implementation of the models was realized with Cast3M&copy;. This study allowed us to point out that the observed variations are linear and would help to plan in advance the impact of axle overloads for a better evaluation within the framework of the mechanistic (M. E.) design of pavements.

A model of vehicle replacement time with overloading cost constraint

Vehicle replacement time depends mainly on the rate of deterioration.Overloading has been found to be a significant factor of deterioration and cost accumulation.We examined the impact of overloading on vehicle deterioration and its total costs and hence the replacement time of vehicle fleets in Nigeria.The research design was a mixture of field survey and a longitudinal study of vehicle fleets of three transport companies in Benin City,Nigeria.The population of the study consisted of all interstate transport companies in Benin City.Multi-stage sampling was used to select the three transport companies studied.An overloading factor was developed and used to estimate the cost of operating overloaded vehicles.Research data were analysed using discrete dynamic programming,which was implemented using computer software developed through Pascal Programming.Results indicate that overloading significantly precipitates vehicle deterioration,increases operating and total cost and thus affects replacement time of vehicles.

Treatment with β-sitosterol ameliorates the effects of cerebral ischemia/reperfusion injury by suppressing cholesterol overload, endoplasmic reticulum stress, and apoptosis

β-Sitosterol is a type of phytosterol that occurs naturally in plants.Previous studies have shown that it has anti-oxidant,anti-hyperlipidemic,anti-inflammatory,immunomodulatory,and anti-tumor effects,but it is unknown whetherβ-sitosterol treatment reduces the effects of ischemic stroke.Here we found that,in a mouse model of ischemic stroke induced by middle cerebral artery occlusion,β-sitosterol reduced the volume of cerebral infarction and brain edema,reduced neuronal apoptosis in brain tissue,and alleviated neurological dysfunction;moreover,β-sitosterol increased the activity of oxygen-and glucose-deprived cerebral cortex neurons and reduced apoptosis.Further investigation showed that the neuroprotective effects ofβ-sitosterol may be related to inhibition of endoplasmic reticulum stress caused by intracellular cholesterol accumulation after ischemic stroke.In addition,β-sitosterol showed high affinity for NPC1L1,a key transporter of cholesterol,and antagonized its activity.In conclusion,β-sitosterol may help treat ischemic stroke by inhibiting neuronal intracellular cholesterol overload/endoplasmic reticulum stress/apoptosis signaling pathways.

Piezo1 channel exaggerates ferroptosis of nucleus pulposus cells by mediating mechanical stress-induced iron influx

To date,several molecules have been found to facilitate iron influx,while the types of iron influx channels remain to be elucidated.Here,Piezo1 channel was identified as a key iron transporter in response to mechanical stress.Piezo1-mediated iron overload disturbed iron metabolism and exaggerated ferroptosis in nucleus pulposus cells(NPCs).Importantly,Piezo1-induced iron influx was independent of the transferrin receptor(TFRC),a well-recognized iron gatekeeper.Furthermore,pharmacological inactivation of Piezo1 profoundly reduced iron accumulation,alleviated mitochondrial ROS,and suppressed ferroptotic alterations in stimulation of mechanical stress.Moreover,conditional knockout of Piezo1(Col2a1-CreERT Piezo1^(flox/flox))attenuated the mechanical injury-induced intervertebral disc degeneration(IVDD).Notably,the protective effect of Piezo1 deficiency in IVDD was dampened in Piezo1/Gpx4 conditional double knockout(cDKO)mice(Col2a1-CreERT Piezo1^(flox/flox)/Gpx4^(flox/flox)).These findings suggest that Piezo1 is a potential determinant of iron influx,indicating that the Piezo1-iron-ferroptosis axis might shed light on the treatment of mechanical stress-induced diseases.

Sema3A secreted by sensory nerve induces bone formation under mechanical loads

Bone formation and deposition are initiated by sensory nerve infiltration in adaptive bone remodeling. Here, we focused on the role of Semaphorin 3A(Sema3A), expressed by sensory nerves, in mechanical loads-induced bone formation and nerve withdrawal using orthodontic tooth movement(OTM) model. Firstly, bone formation was activated after the 3rd day of OTM,coinciding with a decrease in sensory nerves and an increase in pain threshold. Sema3A, rather than nerve growth factor(NGF),highly expressed in both trigeminal ganglion and the axons of periodontal ligament following the 3rd day of OTM. Moreover, in vitro mechanical loads upregulated Sema3A in neurons instead of in human periodontal ligament cells(hPDLCs) within 24 hours.Furthermore, exogenous Sema3A restored the suppressed alveolar bone formation and the osteogenic differentiation of hPDLCs induced by mechanical overload. Mechanistically, Sema3A prevented overstretching of F-actin induced by mechanical overload through ROCK2 pathway, maintaining mitochondrial dynamics as mitochondrial fusion. Therefore, Sema3A exhibits dual therapeutic effects in mechanical loads-induced bone formation, both as a pain-sensitive analgesic and a positive regulator for bone formation.

Venous Doppler flow patterns,venous congestion,heart disease and renal dysfunction:A complex liaison

The World Journal of Cardiology published an article written by Kuwahara et al that we take the pleasure to comment on.We focused our attention on venous congestion.In intensive care settings,it is now widely accepted that venous congestion is an important clinical feature worthy of investigation.Evaluating venous Doppler profile abnormalities at multiple sites could suggest adequate treatment and monitor its efficacy.Renal dysfunction could trigger or worsen fluid overload in heart disease,and cardio-renal syndrome is a well-characterized spectrum of disorders describing the complex interactions between heart and kidney diseases.Fluid overload and venous congestion,including renal venous hypertension,are major determinants of acute and chronic renal dysfunction arising in heart disease.Organ congestion from venous hypertension could be involved in the development of organ injury in several clinical situations,such as critical diseases,congestive heart failure,and chronic kidney disease.Ultrasonography and abnormal Doppler flow patterns diagnose clinically significant systemic venous congestion.Cardiologists and nephrologists might use this valuable,noninvasive,bedside diagnostic tool to establish fluid status and guide clinical choices.

Analysis of Slope Stability with Dynamic Overloading from Earthquake

The analysis of slope earthquake stability is one of the most important research subjects in geotechnical engineering and earthquake engineering.Two different concepts of slope earthquake stability are put forward：strength reserve stability and dynamic overloading stability.The first concept of slope earthquake stability has been widely accepted,and relative analysis methods are also well de-veloped;the second one,however,is seldom mentioned until now,and the failure criterion and the analysis method based on this concept are yet to be explored.What are researched are just the failure criterion and the analysis method of dynamic overloading earthquake stability.The criterion of critical earthquake peak acceleration for the dynamic overloading stability of a slope and its analysis method,the load increasing method（LIM）,are put forward.The dynamic overloading earthquake stability of a loess slope at Changshougou（长寿沟） in Baoji（宝鸡） City,Shaanxi（陕西） Province,China,is analyzed with LIM.The analysis result reveals that the dynamic overloading earthquake stability of the slope is quite high to the action of the earthquake ground motion,with exceeding probability of 10% in the next 50 years.

Global stability coefficient of large underground caverns under static loading and earthquake wave condition

Underground energy and resource development,deep underground energy storage and other projects involve the global stability of multiple interconnected cavern groups under internal and external dynamic disturbances.An evaluation method of the global stability coefficient of underground caverns based on static overload and dynamic overload was proposed.Firstly,the global failure criterion for caverns was defined based on its band connection of plastic-strain between multi-caverns.Then,overloading calculation of the boundary geostress and seismic intensity on the caverns model was carried out,and the critical unstable state of multi-caverns can be identified,if the plastic-strain band appeared between caverns during these overloading processes.Thus,the global stability coefficient for the multi-caverns under static loading and earthquake was obtained based on the corresponding overloading coefficient.Practical analysis for the Yingliangbao(YLB)hydraulic caverns indicated that this method can not only effectively obtain the global stability coefficient of caverns under static and dynamic earthquake conditions,but also identify the caverns’high-risk zone of local instability through localized plastic strain of surrounding rock.This study can provide some reference for the layout design and seismic optimization of underground cavern group.

Investigations of the mechanical response of dummy HTPB propellant grain under ultrahigh acceleration overload conditions using onboard flight-test measurements

In this paper,to study the mechanical responses of a solid propellant subjected to ultrahigh acceleration overload during the gun-launch process,specifically designed projectile flight tests with an onboard measurement system were performed.Two projectiles containing dummy HTPB propellant grains were successfully recovered after the flight tests with an ultrahigh acceleration overload value of 8100 g.The onboard-measured time-resolved axial displacement,contact stress and overload values were successfully obtained and analysed.Uniaxial compression tests of the dummy HTPB propellant used in the gunlaunched tests were carried out at low and intermediate strain rates to characterize the propellant's dynamic properties.A linear viscoelastic constitutive model was employed and applied in finite-element simulations of the projectile-launching process.During the launch process,the dummy propellant grain exhibited large deformation due to the high acceleration overload,possibly leading to friction between the motor case and propellant grain.The calculated contact stress showed good agreement with the experimental results,though discrepancies in the overall displacement of the dummy propellant grain were observed.The dynamic mechanical response process of the dummy propellant grain was analysed in detail.The results can be used to estimate the structural integrity of the analysed dummy propellant grain during the gun-launch process.

SiO_(2) Induces Iron Overload and Ferroptosis in Cardiomyocytes in a Silicosis Mouse Model

Objective The aim of this study was to explore the role and mechanism of ferroptosis in SiO_(2)-induced cardiac injury using a mouse model.Methods Male C57BL/6 mice were intratracheally instilled with SiO_(2) to create a silicosis model.Ferrostatin-1(Fer-1)and deferoxamine(DFO)were used to suppress ferroptosis.Serum biomarkers,oxidative stress markers,histopathology,iron content,and the expression of ferroptosis-related proteins were assessed.Results SiO_(2) altered serum cardiac injury biomarkers,oxidative stress,iron accumulation,and ferroptosis markers in myocardial tissue.Fer-1 and DFO reduced lipid peroxidation and iron overload,and alleviated SiO_(2)-induced mitochondrial damage and myocardial injury.SiO_(2) inhibited Nuclear factor erythroid 2-related factor 2(Nrf2)and its downstream antioxidant genes,while Fer-1 more potently reactivated Nrf2 compared to DFO.Conclusion Iron overload-induced ferroptosis contributes to SiO_(2)-induced cardiac injury.Targeting ferroptosis by reducing iron accumulation or inhibiting lipid peroxidation protects against SiO_(2) cardiotoxicity,potentially via modulation of the Nrf2 pathway.

Repressing iron overload ameliorates central poststroke pain via the Hdac2-Kv1.2 axis in a rat model of hemorrhagic stroke

Thalamic hemorrhage can lead to the development of central post-stroke pain.Changes in histone acetylation levels,which are regulated by histone deacetylases,affect the excitability of neurons surrounding the hemorrhagic area.However,the regulato ry mechanism of histone deacetylases in central post-stroke pain remains unclea r.Here,we show that iron overload leads to an increase in histone deacetylase 2expression in damaged ventral posterolateral nucleus neurons.Inhibiting this increase restored histone H3 acetylation in the Kcna2 promoter region of the voltage-dependent potassium(Kv)channel subunit gene in a rat model of central post-stroke pain,thereby increasing Kcna2expression and relieving central pain.However,in the absence of nerve injury,increasing histone deacetylase 2 expression decreased Kcna2expression,decreased Kv current,increased the excitability of neurons in the ventral posterolateral nucleus area,and led to neuropathic pain symptoms.Moreover,treatment with the iron chelator deferiprone effectively reduced iron overload in the ventral posterolateral nucleus after intracerebral hemorrhage,reversed histone deacetylase 2 upregulation and Kv1.2 downregulation,and alleviated mechanical hypersensitivity in central post-stroke pain rats.These results suggest that histone deacetylase 2 upregulation and Kv1.2 downregulation,mediated by iron overload,are important factors in central post-stroke pain pathogenesis and co uld se rve as new to rgets for central poststroke pain treatment.

Novel compound heterozygous mutations in the hemojuvelin gene in a juvenile hemochromatosis patient:A case report

BACKGROUND Juvenile hemochromatosis(JH)is an early-onset,rare autosomal recessive disorder of iron overload observed worldwide that leads to damage in multiple organs.Pathogenic mutations in the hemojuvelin(HJV)gene are the major cause of JH.CASE SUMMARY A 34-year-old male Chinese patient presented with liver fibrosis,diabetes,hypogonadotropic hypogonadism,hypophysis hypothyroidism,and skin hyperpigmentation.Biochemical test revealed a markedly elevated serum ferritin level of 4329μg/L and a transferrin saturation rate of 95.4%.Targeted exome sequencing and Sanger sequencing revealed that the proband had a novel mutation c.863G>A(p.R288Q)in the HJV gene which was transmitted from his father,and two known mutations,c.18G>C(p.Q6H)and c.962_963delGCinsAA(p.C321*)in cis,which were inherited from his mother.The p.R288W mutation was previously reported to be pathogenic for hemochromatosis,which strongly supported the pathogenicity of p.R288Q reported for the first time in this case.After 72 wk of intensive phlebotomy therapy,the patient achieved a reduction in serum ferritin to 160.5μg/L.The patient's clinical symptoms demonstrated a notable improvement.CONCLUSION This study highlights the importance of screening for hemochromatosis in patients with diabetes and hypogonadotropic hypogonadism.It also suggests that long-term active phlebotomy could efficiently improve the prognosis in severe JH.