scholarly journals Influence of the Saturation Ratio on Concrete Behavior under Triaxial Compressive Loading

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Xuan-Dung Vu ◽  
Matthieu Briffaut ◽  
Yann Malecot ◽  
Laurent Daudeville ◽  
Bertrand Ciree
Keyword(s):  
Nuclear Power ◽  
Water Saturation ◽  
Confining Pressure ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Saturation Ratio ◽  
Concrete Wall ◽  
Saturation State ◽  
Massive Concrete ◽  
The Impact

When a concrete structure is subjected to an impact, the material is subjected to high triaxial compressive stresses. Furthermore, the water saturation ratio in massive concrete structures may reach nearly 100% at the core, whereas the material dries quickly on the skin. The impact response of a massive concrete wall may thus depend on the state of water saturation in the material. This paper presents some triaxial tests performed at a maximum confining pressure of 600 MPa on concrete representative of a nuclear power plant containment building. Experimental results show the concrete constitutive behavior and its dependence on the water saturation ratio. It is observed that as the degree of saturation increases, a decrease in the volumetric strains as well as in the shear strength is observed. The coupled PRM constitutive model does not accurately reproduce the response of concrete specimens observed during the test. The differences between experimental and numerical results can be explained by both the influence of the saturation state of concrete and the effect of deviatoric stresses, which are not accurately taken into account. The PRM model was modified in order to improve the numerical prediction of concrete behavior under high stresses at various saturation states.

Coupling cyclic and water retention response of a clayey sand subjected to traffic and environmental cycles

Géotechnique ◽  
2021 ◽  
pp. 1-45
Author(s):  
Arash Azizi ◽  
Ashutosh Kumar ◽  
David G. Toll
Keyword(s):  
Unsaturated Soils ◽  
Water Retention ◽  
Resilient Modulus ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Soil Water Retention ◽  
Clayey Sand ◽  
Retention Model ◽  
Cyclic Response ◽  
The Impact

Compacted soils used as formation layers of railways and roads continuously undergo water content and suction changes due to seasonal variations. Such variations together with the impact of cyclic traffic-induced loads can alter the hydro-mechanical behaviour of the soil, which in turn affects the performance of the superstructure. This study investigates the impact of hydraulic cycles on the coupled water retention and cyclic response of a compacted soil. Suction-monitored cyclic triaxial tests were performed on a compacted clayey sand. The cyclic response of the soil obtained after applying drying and wetting paths was different to that obtained immediately after compaction. The results showed that both suction and degree of saturation are required to interpret the cyclic behaviour. A new approach was developed using (i) a hysteretic water retention model to predict suction variations during cyclic loading and (ii) Bishop's stress together with a bonding parameter to predict accumulated permanent strain and resilient modulus. The proposed formulations were able to predict the water retention behaviour, accumulated permanent strains and resilient modulus well, indicating the potential capability of using the fundamentals of unsaturated soils for predicting the effects of drying and wetting cycles on the coupled soil water retention and cyclic response.

FEM Analysis of Impact Tests for Steel Plate Concrete Panels against Scaled-Aircraft Impact

2013 ◽  
Vol 477-478 ◽  
pp. 777-783
Author(s):  
Xiu Yun Zhu ◽  
Rong Pan ◽  
Feng Sun
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Steel Plate ◽  
Experimental Result ◽  
Commercial Aircraft ◽  
Concrete Wall ◽  
Concrete Panels ◽  
Aircraft Model ◽  
The Impact ◽  
Aircraft Crash

Due to the rear-face steel plate of the steel plate concrete wall (SC) is very effective in preventing the perforation and scabbing of concrete, in order to resist the impact of commercial aircraft crash, steel plate concrete structures are usually used in the design of external walls of nuclear power plants. In this paper, the simulation analysis of the impact test of 1/7.5 scaled aircraft model impacting the steel plated concrete panels is carried out by using finite element code ANSYS/LS-DYNA. The Winfrith material model (*MAT_84) in ANSYS/LS-DYNA is used to simulate the concrete. The damage profile of panels and residual velocity of aircraft engine comparisons between the simulations and tests are presented in this paper. The results indicate that the damage modes from the impact simulations are very good agreement with the experimental result. It is verified that not only the selection of the material parameters needed for the steel plated concrete wall and aircraft model but also the entire analysis method was appropriate and effective. This paper provided the effective methodology for simulation of the response of the steel plated concrete structure of nuclear power plant due to commercial aircraft crash impact.

scholarly journals Analysis on the Mechanical Characteristics and Energy Conversion of Sandstone Constituents under Natural and Saturated States

2016 ◽  
Vol 2016 ◽  
pp. 1-14 ◽  
Author(s):  
Xinrong Liu ◽  
Jun Liu
Keyword(s):  
Energy Conversion ◽  
Strain Energy ◽  
Water Saturation ◽  
Physical And Mechanical Properties ◽  
Peak Stress ◽  
Confining Pressure ◽  
Triaxial Tests ◽  
Natural State ◽  
Saturated State ◽  
Strength And Deformation

Given that apparent differences exist between physical and mechanical properties of sandstone constituents under natural and saturated states, uniaxial and triaxial tests of sandstone specimens taken from a deep tunnel in Chongqing under the two states were, respectively, conducted in the laboratory. Analysis on the energy conversion of sandstone constituents under natural and saturated states reveals the varying strain energy conversion mechanisms under the two different conditions. It shows that water saturation has significant effects on the strength and deformation characteristics of sandstone constituents. The load bearing capacity and nondeformability decrease once the sandstone constituents are saturated. The strength weakening due to water in saturated specimens mainly takes place after the dilatancy stressσcdand reaches its maximum at the peak stressσf. Strain energies of sandstone constituents under the saturated state are lower than those under the natural state, which indicates that water reduces the strain energy absorption. The strain energy of specimens at the peak stress point under the two states has a good linear positive correlation with the confining pressure. Moreover, the fitting curve of the case under the natural state has a higher slope, which means that the strain energy under such state is more sensitive to the confining pressure than that under the saturated state.

scholarly journals The Environmental Effects of the April 2020 Wildfires and the Cs-137 Re-Suspension in the Chernobyl Exclusion Zone: A Multi-Hazard Threat

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 467
Author(s):  
Rocío Baró ◽  
Christian Maurer ◽  
Jerome Brioude ◽  
Delia Arnold ◽  
Marcus Hirtl
Keyword(s):  
Air Quality ◽  
Nuclear Power ◽  
Transport Model ◽  
Atmospheric Transport ◽  
Point Of View ◽  
Plume Dispersion ◽  
Exclusion Zone ◽  
Fire Plume ◽  
Mean Values ◽  
The Impact

This paper demonstrates the environmental impacts of the wildfires occurring at the beginning of April 2020 in and around the highly contaminated Chernobyl Exclusion Zone (CEZ). Due to the critical fire location, concerns arose about secondary radioactive contamination potentially spreading over Europe. The impact of the fire was assessed through the evaluation of fire plume dispersion and re-suspension of the radionuclide Cs-137, whereas, to assess the smoke plume effect, a WRF-Chem simulation was performed and compared to Tropospheric Monitoring Instrument (TROPOMI) satellite columns. The results show agreement of the simulated black carbon and carbon monoxide plumes with the plumes as observed by TROPOMI, where pollutants were also transported to Belarus. From an air quality and health perspective, the wildfires caused extremely bad air quality over Kiev, where the WRF-Chem model simulated mean values of PM2.5 up to 300 µg/m3 (during the first fire outbreak) over CEZ. The re-suspension of Cs-137 was assessed by a Bayesian inverse modelling approach using FLEXPART as the atmospheric transport model and Ukraine observations, yielding a total release of 600 ± 200 GBq. The increase in both smoke and Cs-137 emissions was only well correlated on the 9 April, likely related to a shift of the focus area of the fires. From a radiological point of view even the highest Cs-137 values (average measured or modelled air concentrations and modelled deposition) at the measurement site closest to the Chernobyl Nuclear Power Plant, i.e., Kiev, posed no health risk.

scholarly journals Aircraft Impact Effects on an Aged NPP

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 816
Author(s):  
Rosa Lo Frano
Keyword(s):  
Nuclear Power ◽  
Military Aircraft ◽  
Residual Resistance ◽  
Plant Safety ◽  
Need To Evaluate ◽  
Target Wall ◽  
Impact Area ◽  
Wall Perforation ◽  
The Impact ◽  
Loss Of Strength

The impact of an aircraft is widely known to be one of the worst events that can occur during the operation of a plant (classified for this reason as beyond design). This can become much more catastrophic and lead to the loss of strength of/collapse of the structures when it occurs in the presence of ageing (degradation and alteration) materials. Therefore, since the performance of all plant components may be affected by ageing, there is a need to evaluate the effect that aged components have on system performance and plant safety. This study addresses the numerical simulation of an aged Nuclear Power Plant (NPP) subjected to a military aircraft impact. The effects of impact velocity, direction, and location were investigated together with the more unfavorable conditions to be expected for the plant. The modelling method was also validated based on the results obtained from the experiments of Sugano et al., 1993. Non-linear analyses by means of finite element (FE) MARC code allowed us to simulate the performance of the reinforced concrete containment building and its impact on plant availability and reliability. The results showed that ageing increases a plant’s propensity to suffer damage. The damage at the impact area was confirmed to be dependent on the type of aircraft involved and the target wall thickness. The greater the degradation of the materials, the lower the residual resistance capacity, and the greater the risk of wall perforation.

Uncertainty studies on hydrogen source term with MAAP5 code

Kerntechnik ◽  
2021 ◽  
Vol 86 (2) ◽  
pp. 152-163
Author(s):  
T.-C. Wang ◽  
M. Lee
Keyword(s):  
Hydrogen Production ◽  
Nuclear Power ◽  
Hydrogen Generation ◽  
Pearson Correlation ◽  
Latin Hypercube Sampling ◽  
Severe Accident ◽  
Model Parameters ◽  
Power Company ◽  
Sensitivity Studies ◽  
The Impact

Abstract In the present study, a methodology is developed to quantify the uncertainties of special model parameters of the integral severe accident analysis code MAAP5. Here, the in-vessel hydrogen production during a core melt accident for Lungmen Nuclear Power Station of Taiwan Power Company, an advanced boiling water reactor, is analyzed. Sensitivity studies are performed to identify those parameters with an impact on the output parameter. For this, multiple calculations of MAAP5 are performed with input combinations generated from Latin Hypercube Sampling (LHS). The results are analyzed to determine the 95th percentile with 95% confidence level value of the amount of in-vessel hydrogen production. The calculations show that the default model options for IOXIDE and FGBYPA are recommended. The Pearson Correlation Coefficient (PCC) was used to determine the impact of model parameters on the target output parameters and showed that the three parameters TCLMAX, FCO, FOXBJ are highly influencing the in-vessel hydrogen generation. Suggestions of values of these three parameters are given.

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