Internal Pressure Coefficients Research Articles

Sensitivity analysis of slope stability based on eXtreme gradient boosting and SHapley Additive exPlanations: An exploratory study

Slope instability through can cause catastrophic consequences, so slope stability analysis has been a key topic in the field of geotechnical engineering. Traditional analysis methods have shortcomings such as high operational difficulty and time-consuming, for this reason many researchers have carried out slope stability analysis based on AI. However, the current relevant studies only judged the importance of each factor and did not specifically quantify the correlation between factors and slope stability. For this purpose, this paper carried out a sensitivity analysis based on the XGBoost and SHAP. The sensitivity analysis results of SHAP were also validated using GeoStudio software. The selected influence factors included slope height (H), slope angle (β), unit weight (γ), cohesion (c), angle of internal friction (φ) and pore water pressure coefficient (ru). The results showed that c and γ were the most and least important influential parameters, respectively. GeoStudio simulation results showed a negative correlation between γ, β, H, ru and slope stability, while a positive correlation between c, φ and slope stability. However, for real data, SHAP misjudged the correlation between γ and slope stability. Because current AI lacked common sense knowledge and, leading SHAP unable to effectively explain the real mechanism of slope instability. For this reason, this paper overcame this challenge based on the priori data-driven approach. The method provided more reliable and accurate interpretation of the results than a real sample, especially with limited or low-quality data. In addition, the results of this method showed that the critical values of c, φ, β, H, and ru in slope destabilization are 18 Kpa, 28°, 32°, 30 m, and 0.28, respectively. These results were closer to GeoStudio simulations than real samples.

Optimization of High Pressure Forming Parameters in Conical Tubes Based on Response Surface Method

The appearance of conical muffler improves the aerodynamic performance and acoustic performance of expansion chamber muffler. The inner surface of this type of pipe has variable section and continuous smoothness. The improvement of the manufacturing efficiency of such tubes is a key issue that needs to be addressed urgently today. To this end, a method of producing conical muffler tubes using a hydraulic expansion process is proposed, using which the weight of the conical muffler tubes can be reduced while the aerodynamic impact of the weld on the muffler tubes is eliminated thereby enhancing the fuel economy of the vehicle. The effect of internal pressure, taper ratio and friction coefficient on the forming results was investigated by using finite element simulation combined with response surface optimization for the hydraulic expansion process method.

Investigation of varying louver angles and positions on cross ventilation in a generic isolated building using CFD simulation

Louvers are an integral component of natural ventilation. This study presents a numerical analysis using computational fluid dynamics (CFD) on cross ventilation in an isolated building equipped with louvers. Opening configurations of (i) center-center, (ii) top-top, (iii) bottom-bottom, (iv) top-bottom and (v) bottom-top (whereby the configurations are defined as ‘windward’-‘leeward’) with varying louver configurations of No-Louver (NL), 0°, 15°, 30° and 45° are studied. Atmospheric Boundary Layer (ABL) condition is applied at the inlet of the flow domain and Renormalization Group (RNG) k-ε turbulence model with enhanced wall function (EWT) is employed for the numerical simulations. Grid sensitivity analysis is performed using Grid Convergence Index (GCI) whilst model validation is performed using Factor of two of observation (FAC2) analysis. The highest dimensionless flow rate (DFR) is achieved by configuration top-top without louvers at 0.719. The highest air exchange efficiency (AEE) is obtained by louver angle of 15° for center-center configuration at 53.4%. The lowest AEE obtained is obtained at louver angle of 0° for top-top configuration at 20%, indicating short-circuiting of air. For configuration bottom-bottom with louver angle of 30°, high AEE is obtained but at the cost of reduced DFR. The optimal balance between AEE and DFR can be obtained by factor-optimization (α) as presented in this paper. The study concludes that opening position alongside louver angle plays an integral role on the internal airflow, pressure coefficient, DFR and AEE in natural cross ventilation.

Nonlinear deformation and instability of a dielectric elastomer tube actuator

The mechanical response and electromechanical instability (EMI) of a dielectric elastomer tube actuator (DETA) under the coupling loadings of voltage, internal pressure and axial force are studied in this paper. Based on the Gent model and considering the nonlinear relationship between dielectric permittivity and stretches, two different loading conditions are discussed: force tuning and voltage tuning. For the force tuning, it is found that the radius of the DETA first decreases, then increases and finally decreases due to the competition between the axial force and voltage as well as the strain-stiffening property of the Gent model under the large deformation. For the voltage tuning, the effects of axial force, internal pressure and electrostrictive coefficient on the electromechanical response are explored. The electrical breakdown (EB) during the nonlinear deformation of DETA is also analyzed. The stress distribution along the thickness of the DETA is given by the analytical solution, and the two failure modes including EMI and loss of tension for the DETA are studied with axial constraints. It is found that the EMI can be eliminated by changing the stretch in the z-direction and internal pressure, which may also lead to the failure of loss of tension. The competitive relations of the two failure modes are discussed in detail. This work can contribute to the design of DETAs with a large actuation.

An equation for hole-spanning design of underground cast iron pipes lined with polymeric liners

Defects such as through-wall holes may significantly affect the performance of cast iron pipes lined with polymeric liners. Literature review reveals that the hole spanning design formulae in the Appendix X1 of ASTM F1216 (2016), also adopted in AWWA (2019), produce conservative results for holes with diameters smaller than the cut-off value defined in ASTM F1216 (2016) and AWWA (2019) for partially and fully deteriorated pipes but unconservative results for holes with diameters larger than the cut-off value, and the effect of holes on the mechanical behaviors of lined water pipes has not been thoroughly investigated. This paper aimed to address the issue in the hole spanning design formulae in ASTM F1216 (2016) and AWWA (2019), and numerically investigated and quantified the effect of holes in cast iron host pipes on the performance of lined pipes. A wide range of pipe dimensions, hole diameters, liner modulus, liner wall thickness, internal pressure and friction coefficients at the interface between the cast iron pipe and liner were considered. An equation for the maximum stresses in polymeric liners was derived based on the numerical results. It was found that the maximum stress in the polymeric liner increases with the diameter of the hole in the cast iron pipe until the hole size reaches a threshold level where the effect of hoop stresses takes over and the maximum stress will tend to plateau. It was also found that increasing the friction coefficient, the ratio of pipe modulus to liner modulus and the liner wall thickness will reduce the maximum stress in the liner. The outcome of this study can assist engineers in more accurate hole spanning design of polymeric liners for deteriorated cast iron pipes and quantifying the size of an unacceptable hole for a given host pipe and a liner product.

Nonlinear hysteretic behavior of wound reinforced composite pipe with steel strip in service

Steel strip wound reinforced composite pipe (SSRCP) is used for shallow sea oil and gas transportation. Its hysteresis characteristics under low-cycle cyclic loads can absorb external energy by deformation. That is beneficial to ensure the stability of ships, drilling platforms and other marine structures. Considering the nonlinear contact between layers, the nonlinear hysteresis characteristics of SSRCP under bending load were investigated. The results show that SSRCP has different strength change trends under different loading modes during the bending cycle loading process, but stiffness degradation characteristics occurs in all conditions. The frictional energy dissipation increases with an accelerated rate. The increasing of limit displacement is the main factor for the rapid accumulation of frictional energy. When the small displacement amplitude is not applied at the initial stage, the effect of stiffness degradation weakens with the internal pressure increases. The stiffness degradation rate decreases with the increasing of the internal pressure and friction coefficient between layers. When the internal and external pressures are both 3 MPa, a minimum point appears on the skeleton curve, which means that the SSRCP stiffness increases. Frictional energy dissipation increases nonlinearly with the increasing of diameter-to-thickness ratio, shelf friction coefficient and internal pressure. There is a critical spiral angle, which makes the ability of SSRCP increases suddenly for absorbing external energy.

Research on Hydraulic Push-Pull Bending Process of Ultra-Thin-Walled Tubes

Due to their high strength, high performance, and lightweight characteristics, bent tubes are widely used in many high-end industries, such as aviation, aerospace, shipbuilding, automobile, and petrochemical industries. Ultra-thin-walled (thickness-to-diameter ratio t/D < 0.01) bent tubes are more prone to wrinkling, fracture, and cross-section distortion than ordinary bent tubes, which are difficult to form integrally by traditional bending processes. In this paper, a new bending process with combined loading of hydraulic pressure, push, and pull was proposed to provide a new method for the bending of ultra-thin-walled tube. This process is characterized by the ability to optimize the combination of push, pull, and internal pressure according to the actual bending process in order to minimize the wrinkling of ultra-thin-walled tube during bending. Based on ABAQUS finite element (FE) software, the FE model of the hydraulic push-pull bending process for ultra-thin-walled tube was established. The influence of internal pressure, die clearance, and friction coefficient on the forming quality of bent tubes was discussed, and the optimum process parameters were obtained. Bent tubes with an initial thickness of 0.3 mm, diameter of 60 mm, and bending radius of 165 mm were manufactured in experiments. Through the comparative analysis of experiment and simulation, the accuracy of the FE simulation was verified.

Dependence of internal pressure in low-rise buildings on aerodynamic parameters, defect features and background leakage

Internal pressure is an important parameter in the estimation of wind effects on low-rise buildings. Cracks and defects located around building fenestrations, lead to air leakage that affects internal pressure. To assess this effect, an experimental study was conducted at the NSF NHERI Wall of Wind Experimental Facility at Florida International University on a full-scale building model. Defects of various sizes and shapes were modeled on one of the building walls. The effect of two simultaneous wall defects on the internal pressure was also investigated. In addition, an analytical procedure was used to predict the internal pressure caused by various wall leakage areas. Results of the analytical procedure were compared with those computed experimentally and reasonable agreement was observed for all leakage areas being considered. The experimental and analytical results showed that the internal pressure increases as the leakage area increases. The correlation between the external and internal pressures was evaluated for the walls and the roof, and the measured peak internal pressure coefficients were compared with those provided by ASCE 7–16 for enclosed and partially enclosed building configurations. It was shown that ASCE 7–16 peak internal pressure coefficients were underestimated for most of the leakage ratios being considered.

Experimental Investigation of Wind Pressure Characteristics for Cladding of Dome Roofs

Cladding for dome roofs is often made of membrane materials that are light and easy to install. Due to these characteristics, wind damage to dome roof cladding is very common. In particular, open or retractable dome roofs are prone to wind damage because of inadequacies in wind load calculations. In this study, the wind pressure characteristics of a dome with a central opening were investigated. Wind tunnel tests were performed, and the pressure distribution was investigated by analyzing external and internal pressure coefficients. Based on the experimental results, the peak net pressure coefficients for the cladding design of a dome roof with a central opening were proposed. For the external peak pressure coefficients, the values of leeward regions were similar despite height–span ratios and turbulence intensity values. For the internal peak pressure coefficients, negative pressure was dominant, and the coefficients were not significantly affected by changes in height–span ratio. This tendency locally increased the negative peak net pressure, in which the load acts in the upward direction, and relatively significantly increased the positive peak net pressure, in which the load acts in the downward direction.

Experimental and theoretical study on the internal pressure induced by the transient local failure of low-rise building roofs

A case study on the internal pressure induced by a local failure on the vulnerable gable roof of a low-rise building was extensively conducted experimentally and numerically. Five roof opening configurations were tested in the wind tunnel under three different boundary layer conditions, based on 1:40 scaled models. The effects of opening shape, opening position, opening ratio, building internal volume, and wind speed on peak transient and steady-state internal pressures were studied. The study results indicate that the peak transient and steady-state internal pressures and the corresponding transient overshoot ratio all increase with an increasing opening ratio. The peak steady-state internal pressure is little affected by the approaching wind speed; while the peak transient internal pressure coefficient shows a significant linear relationship with the wind speed. The coupling effect of vortex shedding and Helmholtz resonance in double building volume compensation situation may cause larger fluctuating internal pressure. Both the vortex shedding and Helmholtz resonance reduce the internal pressure coherence to some extent. The agreement between the numerical and experimental results is much better for the mean internal pressure than that for fluctuating internal pressure or peak internal pressure.

Internal pressure modelling for low-rise buildings in tornadoes

It is well-established that internal pressure can be modelled using the geometric details of the opening and the external pressures near the opening as input. The objective of this study is to determine whether the unique details of tornadic wind fields alter the dynamics of internal pressures, and whether these internal pressures can also be simulated using external pressures at a dominant opening. This is done using measurements from a relatively large-scale tornado simulator for a flow field with multiple sub-vortices, which is expected to be a worst-case scenario for the internal pressure model. These results are then compared to similar studies from atmospheric boundary layer (ABL) wind fields. It is found that the internal pressure model is able to reasonably simulate measured internal pressures in tornadic winds, although not quite as well as in ABL winds. The modelled internal pressure coefficients are mostly within a difference of 0.1 of the measured internal pressure coefficients, which is close to the measurement uncertainty bounds. The reduced accuracy for tornadoes appears to be due to differences in the wind fields in the vortex core of the tornado, particularly the presence of sub-vortices and the vertical component of the wind.

Physicochemical parameters of the binary mixtures of formamide/N-methylformamide with 2-chloroethanol at different temperatures

ABSTRACT The pseudo-Gruneisen parameter , effective Debye temperature, acoustic nonlinearity parameter , internal pressure and isobaric thermal expansion coefficient have been evaluated for binary liquid mixtures of formamide (FA) and N-methylformamide (NMF) with 2-chloroethanol (2Cl-OH) at 298.15 K, 308.15 K and 318.15 K, over the entire concentration range. The excess pseudo-Gruneisen parameter , excess effective Debye temperature , excess nonlinearity parameter, excess internal pressure and excess isobaric thermal expansion coefficient were also calculated. The calculated values are reasonably satisfactory with the experimental results on sound propagation data of liquid mixtures. These physicochemical parameters play an important role in understanding of the significance of anharmonic and nonlinear behaviour with regard to intermolecular interactions in the liquid mixtures.

Tornado-like-vortex-induced wind pressure on a low-rise building with opening in roof corner

This study focuses on internal pressures and wind forces on a gable roof of a low-rise building with an opening in the roof corner in stationary tornado-like vortices. Three roof corner opening sizes and one roof center opening size are tested. The influence of radial distance between building model and tornado center is also investigated. Results indicate that the roof corner opening ratio significantly influences the internal pressures and lift forces on a gable roof. With increase in opening ratio up to 8%, the mean internal pressure coefficient inside the tornado core decreases while the standard deviation increases. In addition, the mean internal pressure coefficient exhibits a minimum value when the building is located at 0.75 times the tornado radius with the roof opening on the windward side. The lift force on the roof may change direction from upward to downward depending on opening ratio and opening position. The coherence function of internal pressure in the high frequency band increases with increase in opening ratio. The correlation between internal and external pressures near the opening is high and increase with increase in opening ratio, which is different from those in straight-line winds.

Uncertainty analysis of a loss of cooling and loss of coolant accident in a spent fuel pool using TRACE

In this work the fundamentals and application results of an uncertainty analysis of a loss of coolant and loss of cooling accident in a spent fuel pool are presented. The spent fuel pool was modeled with TRACE V5.0 Patch 5 using a VESSEL 3D component in Cartesian coordinates. A more detailed nodalization was necessary as compared with a previous study of the same accident scenario to better develop the uncertainty analysis in the framework of the Best Estimate Plus Uncertainty (BEPU) approach. First, the model was calibrated using Main Yankee spent fuel pool experimental data of temperatures and flows measured in steady state conditions. Using the calibrated model, the analysis of the accident was performed considering uncertainty in boundary conditions and in all the coefficients included in the TRACE uncertainty quantification data module. The figure of merit selected in this work is the time at which the cladding oxidation reaches 0.17 times the cladding thickness before oxidation (CFR 50.46 b2). The uncertainty analysis was performed using Wilks’ method and surrogate models. In particular, the Elastic Net surrogate model has demonstrated its potential not only to predict the evolution of the figure of merit in an appropriate way with lower computational effort than the Wilks’ method but also its capability to identify the most relevant uncertain parameters, such as the fuel and cladding specific heats, rod internal pressure coefficient, burst temperature coefficient, a group of fluid regime heat transfer coefficients, the cladding metal-water reaction rate coefficient and the cladding tolerance for the average cores. In addition, the surrogate model provides more information of the distribution of the evolution of the figure of merit. The estimations of the 5/95 tolerance limits, both with the Wilks’ method and with the surrogate models, are very similar, ranging from 30.432 to 30.461 h.

Steady-state and transient wind characteristics of low-rise building roofs with openings in vulnerable areas

A strong wind would cause roof openings on a low-rise building and bring further structural damage. Previous related studies focused on different shapes of openings on flat roofs. Little study has been done on the sloped roofs with openings in vulnerable roof areas. In this study, wind tunnel tests were carried out to investigate the steady-state and transient internal pressure characteristics due to opening at the vulnerable roof areas of a low-rise building. The tests considered both steady-state and transient openings of roof. The experimental results indicated that the steady-state internal pressure distribution tends to be uniform and that the internal pressure induced by leeward roof ridge opening is obviously lower than that induced by the windward one. The fluctuation effect around the orifice area is apparent with the skewed wind direction and the combined effect of internal and external pressures on the unopened roof side is significantly smaller than that on the opened side. Current design provision of China for internal pressure evaluation is found to be unconservative. The transient overshoot is closely related to the opening location in the vulnerable roof area and is more pronounced when the opening is on the leeward side. Among the internal pressure coefficients commonly adopted in design, the extreme net wind pressure coefficient is most important, which is affected most at the orifice near eaves, roof corners and tails, and leeward roof ridge.

Rezul'taty chislennogo modelirovaniya vyazkogo potoka v maloraskhodnykh stupenyakh tsentrobezhnykh kompressorov kak osnova sozdaniya matematicheskoy modeli napora

The paper envisages the results of calculation of a threedimensional viscous flow in 18 lowflow stages of centrifugal compressors in the range of optimal conditional flow coefficient Фopt = 0.007-0.018. Gasdynamic characteristics of the internal and polytropic pressure coefficients in full parameters were plotted and compared with experimental data. The calculated gasdynamic characteristics of viscous flow satisfying the engineering accuracy of calculations and experimental character of the curves were obtained using Ansys CFX software

Режимы проведения исследований с применением технологий фильтрации на газоконденсатных месторождениях

The article shows the methods of hydrodynamic research: in stationary and non-stationary mode, which were carried out at the Urengoy gas condensate field. The filtration resistance coefficients A (by the nature of opening a gas well) and B (by the degree of opening of a gas well) are determined in the article. As a result, conclusions were drawn that in the process of developing the Urengoy field in recent years, the coefficients A and B did not change significantly. As a result of the analysis of hydrodynamic studies at the Urengoyskoye field, several recommendations have been made to improve the development of the Senoman reservoir. The most important is the conduct of PIP to assess the adhesion of cement stone to the column and filling the annular space with cement mortar in the intervals of opening of productive thicknesses, this is indicated by the anomalies of the internal pressure coefficient.

Experimental investigation of wind-induced internal pressures in nominally sealed building structures

The action of internal pressure cannot be neglected in wind-resistant design of large-span structures, high-rise buildings, and low-rise residential buildings. In this study, the internal pressure characteristics were first measured in still air in a completely closed building structure without any leakage. Then a series of wind tunnel tests were conducted to study the probability density distribution characteristics of the internal pressure responses in a nominally sealed building with background leakage. The mean and peak internal pressure responses associated with different background leakage distributions and wind directions were further investigated, and the experimental results were compared with those suggested by the Chinese wind load code GB50009-2012. The results indicated that the internal pressure in the completely closed building was non-stationary, and varied significantly when collected at different time points. Furthermore, a period of about 24 h was observed from the measured time history of internal pressure over 9 d. The internal pressure in a nominally sealed building structure nearly fitted a normal Gaussian distribution. When background leakage was uniformly arranged on the surface of the building, the mean internal pressure coefficient remained unchanged with increasing background leakage, varying within the range from −0.15 to −0.14, indicating lower magnitudes than the value of −0.2 suggested by the Chinese wind load code. The minimum negative peak internal pressure coefficient was −0.255 when the peak factor was 3.5, indicating a lower magnitude than the value of −0.326 calculated in the Chinese wind load code.

Slope stability prediction for circular mode failure using gradient boosting machine approach based on an updated database of case histories

Prediction of slope stability is one of the most crucial tasks in mining and geotechnical engineering projects. The accuracy of the prediction is very important for mitigating the risk of slope instability and enhancing mine safety in preliminary design. However, existing methods such as traditional statistical learning models are unable to provide accurate results for slope instability due to the complexity and uncertainties of multiple related factors with small unbalanced data samples thus requiring complex data processing algorithms. To address this limitation, this paper presents a novel prediction method that utilizes the gradient boosting machine (GBM) method to analyze slope stability. The GBM-based model is developed by the freely available R Environment software, trained and tested with the parameters obtained from the detailed investigation of 221 different actual slope cases between 1994 and 2011 with circular mode failure available in the literature. The stability of the circular slope accounts for the unit weight (γ), cohesion (c), angle of internal friction (φ), slope angle (β), slope height (H) and pore water pressure coefficient (ru). A fivefold cross-validation procedure is implemented to determine the optimal parameter values during the GBM modeling and an external testing set is employed to validate the prediction performance of models. Area under the curve (AUC), classification accuracy rate and Cohen’s Kappa coefficient have been employed for measuring the performance of the proposed model. The analysis of AUC, accuracy together with kappa for the dataset demonstrate that the GBM model has high credibility as it achieves a comparable AUC, classification accuracy rate and Cohen’s kappa values of 0.900, 0.8654 and 0.7324, respectively for the prediction of slope stability. Also, variable importance and partial dependence plots are used to interpret the complex relationships between the GBM predictive results and predictor variables.

Numerical Analysis of Mechanical Behavior of Buried Pipes in Subsidence Area Caused by Underground Mining

The buried pipe crossing the subsidence area is prone to failure. The mechanical behavior of buried pipe in subsidence area was investigated in this paper. Effects of subsidence displacement, pipe parameters and soil parameters on the mechanical behavior were investigated. The results show that high stress appears on the pipe's surface and exceeds the yield strength after the strata subsidence. As subsidence displacement increases, the ranges of high-stress area and displacement increase, and the pipe section changes from a circle to an ellipse. The maximum axial strain occurs on the pipe in no-subsidence area. The maximum plastic strain and ovality of the pipe increase with the increasing of subsidence displacement. The displacement, plastic strain, and ovality of the pipe increase with the increasing of diameter–thickness ratio and buried depth. Internal pressure and friction coefficient has a little effect on the pipe displacement. The ovality decreases as internal pressure increases. The plastic strain and ovality increase with the increasing of the friction coefficient. As the elastic modulus and cohesion of soil increase, the displacement, plastic strain, and ovality of the pipe increase. The effect of Poisson's ratio on the deformation of pipe is small.