Stress Of Dam Research Articles

Postnatal Light Effects on Pup Stress Axis Development Are Independent of Maternal Behavior.

Postnatal environment shapes brain development during key critical periods. We have recently found that postnatal light environment has long-term effects on the stress and circadian systems, which can lead to altered stress responses, circadian behavior and a depressive phenotype in adulthood. However, it is still unclear how light experience affects the postnatal development of specific stress markers in the pup brain and the role played by maternal behavior and stress. To test this, we raised mice under either light-dark cycles (LD), constant light (LL) or constant darkness (DD) during the suckling stage. After weaning, all mice were exposed to LD until adulthood. Results show that postnatal light environment does not have any significant effects on dam stress levels (plasma corticosterone concentration, Arginine-vasopressin and Glucocorticoid receptor (GR) protein expression in the brain) or maternal behavior, including licking and grooming. Light environment does not have a major effect on litter characteristics or pup growth either. Interestingly, light environment during the suckling stage significantly impacted Corticotrophin-releasing hormone (CRH) and Gr mRNA expression in pup brain during development. Furthermore, a difference in Crh mRNA expression between LL- and DD-raised mice was still observed in adulthood, long after the exposure to abnormal light environments had stopped. Taken together, these data suggest that the long-term effects of postnatal light environment on the pups' stress system cannot be attributed to alterations in either maternal behavior and/or stress axis function. Instead, postnatal light experience may act directly on the pup stress axis and/or indirectly via circadian system alterations.

Erratum: Effects of disturbed liver growth and oxidative stress of high-fat diet-fed dams on cholesterol metabolism in offspring mice.

[This corrects the article on p. 386 in vol. 10, PMID: 27478544.].

Numerical prediction of stress and displacement of ageing concrete dam due to alkali-aggregate and thermal chemical reaction

The damage of concrete due to the expansion of alkali-aggregate reaction (AAR) and thermal-chemical reactions affecting the strength of concrete is studied. The empirical equations for the variations of expansion of AAR, compressive strength and degradation of the modulus of elasticity with time, and compressive strength with degradation of the modulus of elasticity are proposed by analysing numerous experimental data. It is revealed that the expansion of AAR and compressive strength increase with time. The proposed combination of the time variations of chemical and mechanical parameters provides a satisfactory prediction of the concrete strength. Seismic analysis of the aged Koyna dam is conceded for two different long-term experimental data of concrete incorporating the proposed AAR based properties. The responses of aged Koyna dam reveal that the crest displacement of the Koyna dam significantly increases with time while the contour plots show that major principal stress at neck level reduces with time. As the modulus of elasticity decreases with ages the stress generated in the concrete structure get reduces. On the other hand with lesser value of modulus of elasticity the structure becomes more flexible and the crest displacement becomes very high that cause the seismic safety of the dam reduce

Coupled and uncoupled seepage-stress analysis of roller compacted concrete dams

The seepage problem of roller compacted concrete (RCC) dams is more complex because of involving compaction in its construction process in a series of layers. After completion of reservoir storage, the distribution of dam seepage field will affect that of the stress field. At the same time, the change in the dam stress field will react on the dam’s pores and cracks, reflecting the significance of seepage. Clearly, an interaction exists between seepage and stress fields. Therefore, it is of great importance and interest to evaluate the safety of gravity dams under the coupled seepage–stress interaction. In this paper, the interaction between seepage and stress fields of RCC dam is analysed based on coupled and uncoupled models. Numerical solution of coupled and uncoupled seepage and stress fields of Kinta RCC gravity dam (located in Malaysia) is analysed by means of the finite-element method in this study. The results show a similar distribution of seepage, stress and displacement fields for both models. However, compared to the uncoupled model, the displacement and stress components increase at different rates and the stress concentration near the dam heel is more obvious in the coupled model.

Stress Analysis of Dongjiang Arch dam by Finite Element Method under Different Concrete Elastic Modulus and High-Low Temperature Seasons

Elastic modulus and temperature are the main influences of dam stress. In order to study the Dongjiang dam stress for crack controlling, the critical parts stress of dam under different elastic modulus and high-low temperature seasons is analyzed by the finite element method. The results show that: (1) the arch crown and abutment principal tensile stress at upstream face and principal compressive stress at downstream face under high temperature season are greater than the calculation results under low temperature season for the whole at the normal storage water level; (2) the influence on stress caused by elastic modulus are more significant under high temperature season compared to low temperature season at arch crown and abutment, the maximum stress increase with the increasing of elastic modulus. (3) Dongjiang arch dam should pay more attention to the safety control under high temperature season and surface crack prevention and control work in low temperature season.

Analysis of working behavior of Jinping-I Arch Dam during initial impoundment

To study the stress, deformation, and seepage pressure during the initial impoundment of the Jinping-I Arch Dam, monitoring analysis and numerical calculation were used in a dam behavior analysis that focused on the working behavior of the dam during the late period of the initial impoundment up to the end of November 2014. The numerical calculation was performed based on feedback analysis of the deformation and stress of the arch dam through inversion of the elastic moduli (E) of the dam body and foundation, using a three-dimensional finite element model for the linear elastic material of the arch dam. The main monitoring indices presented insignificant changes in the late period of the initial impoundment, and the results of feedback analysis were consistent with monitoring results. Analysis results also show that the deformations of the dam body and dam foundation were within the design range; the dam stress distributions were normal, with values lower than the design control criteria; and the seepage flows through the dam body and dam foundation were lower than the design drainage capacity of the deep-well pump house, demonstrating that the Jinping-I Arch Dam was in good working condition, and the initial impoundment had been successfully completed. The results of the working behavior analysis of the Jinping-I hydropower project during the initial impoundment can provide references for safe operation of similar projects.

Weaning and separation stress: maternal motivation decreases with litter age and litter size in farmed mink

The optimal timing of separating the mink dam from the litter is suggested to be a balance between the partly conflicting needs of the mother and the kits. Early removal of the dam or partial removal of the litter may protect the dam against exhaustion. Little is, however, known about dam stress and maternal motivation around the time of weaning and separation. Therefore, we investigated effects of separating the dam from the litter using brown first-parity farm mink dams (n=374) taken away from the litter either day 49±1 (7w, n=185) or day 56±1 (8w, n=189) after birth. The aim was to investigate whether the dams experienced stress/had a different motivation to be reunited with the litter after 7 and 8 weeks, estimated by non-invasive determination of cortisol (FCM: Faecal Cortisol Metabolites) and dam behaviour including calls the first week after separation (D0: Day of removal, D1: next day, D7: seven days after). Supplementary, we evaluated dam body condition (weight, score), nipple activity and health at separation. The two treatment groups had an equal litter size at the time of separation (7w: 5.5±0.17; 8w: 5.5±0.17 kits; P=0.76). Likewise, there was no significant difference in dam body weight (7w: 1420±15.0g, 8w: 1404±14.7, P=0.43). However, the litter size negatively influenced both the dam weight and body condition (P<0.001) regardless of the separation age. Stereotypies D0-D1 were influenced by group (8w>7w) and increased with number of young (P<0.01), indicative of dam hunger/metabolic burden in the preceding period. We found no signs of nipple/inflammation problems, evaluated visually and by Infrared Thermography (IRT) measuring surface temperatures of active teats. Dams separated at litter age 7 weeks had higher concentrations of cortisol metabolites during the first week after removal; i.e. day of separation, D0: 18.8%, D1: 34.5%, D7: 36.9% higher FCM than in 8w dams (P=0.014). Likewise, the dam calls increased on the separation day, peaking on the first day after separation (D1). The proportion of dams with calls was higher in the 7w group (P=0.024). We interpret these results as a higher maternal motivation in dams at 7 weeks than at 8 weeks after birth. Additionally, the separation-induced calling in dams decreased with increasing litter size (P=0.022). Thus in addition to litter age, the size of the litter is important for the maternal motivation. These factors should, therefore, be taken into account for determining the optimal separation time on mink farms.

Periconceptional Heat Stress of Holstein Dams Is Associated with Differences in Daughter Milk Production during Their First Lactation

The fertility of lactating Holstein cows is severely reduced during periods of heat stress. Despite this reduction in fertility, however, some inseminations conducted during heat stress result in successful pregnancies from which heifer calves are born. Many of these heifer calves are retained and raised to enter the milking herd as replacement animals. Heat stress experienced by these females around the time they were conceived may confer long-lasting effects that alter subsequent milk production capacity. The objective of this study was to examine the relationship between periconceptional heat stress and subsequent milk production of primiparous cows. National Dairy Herd Improvement Association data was obtained from Dairy Records Management Systems. Records included Holstein cows that had completed at least one lactation in one of three states with large populations of dairy cattle and which are known for having hot, humid summers: Georgia, Florida or Texas. Dates of conception were calculated by subtracting 276 d from the recorded birth date of each individual cow. Records for cows conceived within the months of June, July, and August were retained as heat stress-conceived (HSC) cows (n = 94,440); cows conceived within the months of December, January, and February were retained as thermoneutral-conceived (TNC) contemporaries (n = 141,365). In order to account for the effects of environmental conditions on total milk production for a given lactation, cows were blocked by season of calving (winter, spring, summer or fall). Adjusted 305-day mature-equivalent milk production was evaluated with a mixed model ANOVA using SAS, in which random effects were used to account for variability between herds. Of the cows that calved in the summer, fall and winter, TNC cows had higher milk yield than the HSC cows in all states. Interestingly, the cows that calved in the spring presented a unique relationship, with HSC cows producing more milk. Overall however, heat stress at the time of conception is associated with lower milk production during the first lactation. While this association does not prove cause and effect, it does provide justification for additional investigation into whether heat stress around the time of conception results in long-term, detrimental consequences for the conceptus.

Effects of disturbed liver growth and oxidative stress of high-fat diet-fed dams on cholesterol metabolism in offspring mice.

BACKGROUND/OBJECTIVESChanges in nutritional status during gestation and lactation have detrimental effects on offspring metabolism. Several animal studies have shown that maternal high-fat diet (HFD) can predispose the offspring to development of obesity and metabolic diseases, however the mechanisms underlying these transgenerational effects are poorly understood. Therefore, we examined the effect of maternal HFD consumption on metabolic phenotype and hepatic expression of involved genes in dams to determine whether any of these parameters were associated with the metabolic outcomes in the offspring.MATERIALS/METHODSFemale C57BL/6 mice were fed a low-fat diet (LFD: 10% calories from fat) or a high-fat diet (HFD: 45% calories from fat) for three weeks before mating, and during pregnancy and lactation. Dams and their male offspring were studied at weaning.RESULTSDams fed an HFD had significantly higher body and adipose tissue weights and higher serum triglyceride and cholesterol levels than dams fed an LFD. Hepatic lipid levels and mRNA levels of genes involved in lipid metabolism, including LXRα, SREBP-2, FXR, LDLR, and ABCG8 were significantly changed by maternal HFD intake. Significantly lower total liver DNA and protein contents were observed in dams fed an HFD, implicating the disturbed liver adaptation in the pregnancy-related metabolic demand. HFD feeding also induced significant oxidative stress in serum and liver of dams. Offspring of dams fed an HFD had significantly higher serum cholesterol levels, which were negatively correlated with liver weights of dams and positively correlated with hepatic lipid peroxide levels in dams.CONCLUSIONSMaternal HFD consumption induced metabolic dysfunction, including altered liver growth and oxidative stress in dams, which may contribute to the disturbed cholesterol homeostasis in the early life of male mice offspring.

Design Optimization of a Concrete Face Rock-Fill Dam by Using Genetic Algorithm

This paper combined with the adaptive principle to improve the genetic algorithms (GA) and applied it to optimal design of the shape of the concrete face rock-fill dam (CFRD). Based on the improved GA, a mathematical model was established for the design optimization of CFRD. CFRD utilizes dam cost as objective function and dam slope and geometries of the dam material partition as design variables. Dam stability, stress, displacement, and stress level are used as the main condition constraints. The calculation procedures were prepared, and the GA was used to optimize the design of Jishixia CFRD. Results show that the GA could solve the global optimal solution problem of complex optimization design, such as the high degree of nonlinearity and the recessiveness of constraint conditions, and using the GA to optimize the CFRD design can reduce the quantities of projects and engineering safety costs.

Periconceptional Heat Stress of Holstein Dams Is Associated with Differences in Daughter Milk Production and Composition during Multiple Lactations.

Heat stress at the time of conception affects the subsequent milk production of primiparous Holstein cows; however, it is unknown whether these effects are maintained across multiple lactations. Therefore, the objective of the current study was to examine the relationship between periconceptional heat stress and measurements of milk production and composition in cows retained within a herd for multiple lactations. National Dairy Herd Improvement Association data was obtained from Dairy Records Management Systems. Records included milk production data and milk composition data from over 75,000 and 44,000 Holstein cows, respectively, born between 2000 and 2010 in Florida, Georgia, and Texas. Conception dates were calculated by subtracting 276 d from the recorded birth date. Records for cows conceived within the months of June, July, and August were retained as heat stress conceived (HSC) cows; cows conceived within the months of December, January, and February were retained as thermoneutral conceived (TNC) contemporaries. Adjusted 305-d mature equivalent milk, protein percent and fat percent were evaluated with a mixed model ANOVA using SAS. Milk production was significantly affected by periconceptional heat stress. When a significant difference or tendency for a difference was detected between the HSC and TNC cows, the TNC produced more milk in all but one comparison. The advantage in milk production for the TNC cows over the HSC cows ranged from 82 ± 42 to 399 ± 61 kg per lactation. Alterations in fat and protein percentage were variable and most often detected in first lactations (first > second or third). Overall, the most striking result of this study is the consistency of the relationship between HSC and milk production. The nature of this relationship suggests that heat stress at or around the time of conception impairs cow milk yield throughout her lifetime.

The Analysis of Stress, Deformation and Arch Effect of the Lianghekou Earth-rockfill Dam

Deformation, stress and arch effect are problems of interest for high earth- rockfill dams. Deformations and stresses during construction, impoundment and operation stages of Lianghekou earth-rockfill dam were studied through numerical methods. The filling materials were modeled by using the Mohr- Coulomb and Burgers models. As a result, the maximum vertical displacement is located in the middle of the dam height during every stage. The vertical displacement increases evidently during operation stage due to the time dependent behavior of the dam materials. The dam moves in the downstream direction after impoundment. The horizontal displacements of upstream rockfill and downstream rockfill increase during operation stage. The level of arch effect increases evidently after 10 years of operation due to the time dependent behavior of dam materials. The possibility of horizontal cracks and hydraulic fracturing is little during construction stage and impoundment stage, but increases evidently after operation.

General displacement arch-cantilever element method for stress analysis of arch dam

Based on the general displacement method and the basic hypothesis of the trial load method, a new advanced trial load method, the general displacement arch-cantilever element method, was proposed to derive the transformation relation of displacements and loads between the surface nodes and middle plane nodes. This method considers the nodes on upstream and downstream surfaces of the arch dam to be exit nodes (master nodes), and the middle plane nodes to be slave nodes. According to the derived displacement and load transformation matrices, the equilibrium equation treating the displacement of middle plane nodes as a basic unknown variable is transformed into one that treats the displacement of upstream and downstream nodes as a basic unknown variable. Because the surface nodes have only three degrees of freedom (DOF), this method can be directly coupled with the finite element method (FEM), which is used for foundation simulation to analyze the stress of the arch dam with consideration of dam-foundation interaction. Moreover, using the FEM, the nodal load of the arch dam can be easily obtained. Case studies of a typical cylindrical arch dam and the Wudongde arch dam demonstrate the robustness and feasibility of the proposed method.

Influence on Stress and Strain of High Embankment Dams Caused by Different Reservoir Filling Path

For computing the stress and strain of embankment dams, FEM is employed. Two reservoir filling paths which are constructing filling and completed filling are considered to affect the computing results. It is proved that constructing filling path can enhance the stress of embankment dams. So constructing filling path can take from the hydraulic fracturing of core wall. In addition, constructing filling path can decrease the amount of settlement, and can control the displacement of dam shoulders. In a word, constructing filling path is prior to completed filling path.

Stress and Strain Analysis of Waste Dam and Stability Analysis of Landfill

Stress and strain of waste dam were analyzed based on the construction design and situations in the field. In situ stress field was calculated according to linear elastic material model and deformation was simulated according to hyperbolic nonlinear plastic model. On the basis of the deformation and stress analysis, dam stability was evaluated according to the deformation by total stress method. The result shows that the stability of the dam can meet the specification requirements and be operated normally even if the deformation occurs when solid waste are heaped up to 0-12 m according to the preliminary design scheme.

Influence Analysis of Dam Stress and Displacement Caused by Stiffness Degradation and Mass Loss

The concrete dam under dead load, water pressure load and wind load is in high stress state for a long time, whose safety is in a dangerous station to a certain extent. The static calculation of the dam was done by ANSYS. In order to know the static characteristics of the dam, and to provide a theoretical basis for dam health diagnosis and routine maintenance, the variation of the dam stress and displacement caused by the stiffness degradation and mass loss was studied. The influence degree of the dam mass loss and stiffness degradation on stress and displacement were discussed. The results show that stress along the dam height (Y direction) is higher than it along the horizontal direction (X direction), the maximum stress difference is to about 4 times. The influence degree of dam stress and displacement caused by stiffness degradation is more serious than those by mass loss.

Seismic Fortification Analysis of the Guoduo Gravity Dam in Tibet, China

The primary aim of this research was to analyze the seismic performance of the Guoduo gravity dam. A nonlinear FEM method was implemented to study the deformation, stress, and overall stability of dam under both static and dynamic loading conditions, including both normal and overloading conditions. A dam seismic failure risk control method is proposed based on the cracking mechanism induced by the dynamic load to ensure dam safety and stability. Numerical simulation revealed that (1) under normal static and dynamic loading the symmetry of the displacement distributions is good, showing that the dam abutments and riverbed foundation have good overall stiffness. The stress distribution is a safe one for operation under both normal water loading and seismic loading. (2) Attention should be paid to the reinforcement design of outlets of the diversion dam monoliths, and enhance the capability of sustaining that tensile stress of dam monoliths. (3) The shape of the dam profile has a significant effect on the dynamic response of the dam. (4) By employing the “overload safety factor method,” the overall seismic fortification is as follows:K1=1.5,K2=2~3, andK3=3~4.

ASSESSMENT OF STRESS DISTRIBUTION IN DARAB'S ROODBAL EMBANKMEND DAM USING COMMERCIAL CODE FLAC

Abstract. Evaluation of performance and behavior of a dam is viable by monitoring of dam using instrumentation. Stress and deformation analysis during end of construction is one of the important parameters in analysis, design, and stability of an embankment dam. In this study, a comparison between various models in stress and deformation analysis of Roodbal dam during end of construction using finite element method in FLAC software was established. The results showed that Mohr-Coulomb model has good accuracy in analysis of vertical settlement of dam core. It was also known that vertical displacement of Darab's Roodbal dam is slow ascending which is slower in upstream than downstream shell. The overall stress in dam body is also slow ascending that shifted from lower level near the core to middle lower level of core during first impoundment through the end of first 10-year utilization period. The analysis over whole body showed that after completion of construction and then initial impoundment of dam pore water pressure in the core of dam is 370 kPa which was the same in middle level of core. According to analysis conducted over whole body of dam, displacement reached 96 cm after completion of construction which was also the same for one-third middle level of core.

Study on Real-Time Simulation Analysis and Inverse Analysis System for Temperature and Stress of Concrete Dam

In the concrete dam construction, it is very necessary to strengthen the real-time monitoring and scientific management of concrete temperature control. This paper constructs the analysis and inverse analysis system of temperature stress simulation, which is based on various useful data collected in real time in the process of concrete construction. The system can produce automatically data file of temperature and stress calculation and then achieve the remote real-time simulation calculation of temperature stress by using high performance computing techniques, so the inverse analysis can be carried out based on a basis of monitoring data in the database; it fulfills the automatic feedback calculation according to the error requirement and generates the corresponding curve and chart after the automatic processing and analysis of corresponding results. The system realizes the automation and intellectualization of complex data analysis and preparation work in simulation process and complex data adjustment in the inverse analysis process, which can facilitate the real-time tracking simulation and feedback analysis of concrete temperature stress in construction process and enable you to discover problems timely, take measures timely, and adjust construction scheme and can well instruct you how to ensure project quality.

Upstream Slope Ratio Effects on the Heel Stress of Concrete Gravity Dam

Heel is a critical area due to the high-gradient when the stress of a concrete gravity dam is analyzed. This article employed ANSYS, a kind of structure analysis software, to establish a two-dimensional model and to analyze the stress of a concrete gravity dam with Finite Element Method. Then the effects of upstream slope ratio on the stress of the dam heel in the operating conditions were researched and some valuable conclusions drawn from this paper can be adopted by the designer of concrete gravity dam.