Calculation Of Safety Factor Research Articles

Design and Simulation of Cracks in A Four-Cylinder Engine Crankshaft Using Finite Element Method

The translational motion of the piston was transformed into a rotational motion by the crankshaft. The combustion resulted in straight thrust in the piston was passed through the piston rod and pushed the crank pin, resulting in a rotational force on the crankshaft. In other words, the crankshaft received high loading and rotated at high speed in each cycle of work. Therefore, crankshafts should be made of high carbon steel with a high endurance limit. The major cause of failure is thermal fatigue since the contact between journal and bearing surface occurred. The contact may result from two reasons: problems of lubrication and use. Based on the factor of safety calculation, crank 1 and 4 were considered to meet the safety criteria because their positions were close to the support of the crankshaft

The DTEQ Code for Toroidal MHD Equilibria with Diamagnetic Current Modeling Using the deal.II Finite Element Library

The Deal Two Equilibrium (DTEQ) code solves the Grad-Shafranov (GS) equation for magnetohydrodynamics equilibrium in the axisymmetric toroidal geometry using the deal.II finite element library. In this paper, we introduce DTEQ that can solve the GS equation both linearly and nonlinearly. The linear solution obtained from this code is verified by comparing with a known analytic solution of the linear GS equation. For the nonlinear solution, DTEQ requires two input profiles, p(ψ) and F(ψ), to be specified as a function of the normalized minor radius ρ. The pressure profile p(ψ) is specified based on Thomson scattering, charge exchange spectroscopy data, and an energetic particle pressure model. The toroidal field profile F(ψ) is obtained from our model that makes the diamagnetic current play a significant role when the poloidal beta βp is greater than one. With these two input profiles, the nonlinear GS equation can be solved using Picard iteration within the plasma boundary from EFIT. Using this newly developed code, we obtain several meaningful results that show its validity. The calculated poloidal current density is very large in the transport barrier due to the diamagnetic current, and the characteristics of the Pfirsch-Schlüter current appear in the toroidal current density. In addition, the results obtained from this code agree well with those from EFIT, and the calculated safety factor values in the center are well correlated with the sawtooth activity in the discharge.

The influence of number of grid points and radius increments in determining safety factor and estimated sliding volume on three-dimensional slope stability analysis

The existence of geometric complexity in the longitudinal direction makes 3D Limit Equilibrium Method (LEM) able to depict conditions in the field well and obtain Safety Factor (SF) that is more representative than the 2D limit equilibrium method. Safety factor calculations are not only influenced by the Direction of Sliding (DoS), but also by the location of the slip surface. Therefore, determining the location of the slip surface is important in the 3D limit equilibrium method. In this study, the method used for generating slip surfaces is a grid search where variations are made on the number of grid points and the radius increments to determine the effect of these two variables on the determination of safety factor and estimated sliding volume. Based on the results of the study, it can be stated that the greater the number of grid points and the radius increments, the estimated sliding volume will be more precise, while the calculation of safety factor is only affected by the number of grid points where the greater the number of grid points, the search of critical slip surface will be more accurate.

New insights on the cardiac safety factor: Unraveling the relationship between conduction velocity and robustness of propagation

Cardiac conduction disturbances are linked with arrhythmia development. The concept of safety factor (SF) has been derived to describe the robustness of conduction, but the usefulness of this metric has been constrained by several limitations. For example, due to the difficulty of measuring the necessary input variables, SF calculations have only been applied to synthetic data. Moreover, quantitative validation of SF is lacking; specifically, the practical meaning of particular SF values is unclear, aside from the fact that propagation failure (i.e., conduction block) is characterized by SF < 1. This study aims to resolve these limitations for our previously published SF formulation and explore its relationship to relevant electrophysiological properties of cardiac tissue. First, HL-1 cardiomyocyte monolayers were grown on multi-electrode arrays and the robustness of propagation was estimated using extracellular potential recordings. SF values reconstructed purely from experimental data were largely between 1 and 5 (up to 89.1% of sites characterized). This range is consistent with values derived from synthetic data, proving that the formulation is sound and its applicability is not limited to analysis of computational models. Second, for simulations conducted in 1-, 2-, and 3-dimensional tissue blocks, we calculated true SF values at locations surrounding the site of current injection for sub- and supra-threshold stimuli and found that they differed from values estimated by our SF formulation by <10%. Finally, we examined SF dynamics under conditions relevant to arrhythmia development in order to provide physiological insight. Our analysis shows that reduced conduction velocity (Θ) caused by impaired intrinsic cell-scale excitability (e.g., due to sodium current a loss-of-function mutation) is associated with less robust conduction (i.e., lower SF); however, intriguingly, Θ variability resulting from modulation of tissue scale conductivity has no effect on SF. These findings are supported by analytic derivation of the relevant relationships from first principles. We conclude that our SF formulation, which can be applied to both experimental and synthetic data, produces values that vary linearly with the excess charge needed for propagation. SF calculations can provide insights helpful in understanding the initiation and perpetuation of cardiac arrhythmia.

Comparative Analysis of the Hard Hillsides Stability by Empirical Methods and Limit Equilibrium: Case of Ultra Basic and Andesites of Mako and Marbles of Bandafassi (Senegal)

The purpose of this paper is to characterize rock mass stability using basic rock mass method and to compare them. Rock mass quality and strength are determined using rock mass classification and numerical methods. The Factors of safety are calculated with the results of stereographic projection. Results show that quality of ultrabasite and marble are better than quality of andesite. The Slope Mass Ratings (SMR) show that rocks with the best quality are stable and andesite partially stable. The calculation of the factors of Safety by limit equilibrium assigns a stable state for ultrabasite and marble and instable for andesite. Calculation of Safety factor using stereographic parameters in one hand and finite element code in another shows more possibility of planar sliding along discontinuities than rock matrix failure. At last, quality of endogeneous rock mass is correlated with its stability state. The better rock mass is, the more stable the rock it is.

Regional Stability Analysis of Red Clay Slope Based on Different Failure Modes: A Case Study in Taizaifu Area, Fukuoka

Red clay slopes have different failure modes in different geological and climatic contexts. Underlying weak layers are frequently witnessed in integral failures because of the reverse consolidation characteristics. On the contrary, heavy rainfall often causes superficial sliding for a considerable infiltration through developed microfractures. Based on the Geographic Information System, regional stability of red clay slopes was evaluated with two failure modes, such as “integral sliding” and “planar sliding.” First, terrain and borehole data of the study area were used to construct the digital elevation model. Second, slope units were partitioned as research objects. For integral sliding, the slip surface was supposed to lie above the strata interface, and it was regarded as a lower part of an ellipsoid. After calculating safety factors of potential slip surfaces that were randomly generated by the Monte Carlo method, the minimum safety factor of the slope unit and the critical slip surface could be determined. For shallow landslides triggered by rainfall infiltration, the one‐dimensional infiltration model and infinite slope model were used. Moreover, the difference between the sliding direction of each column and the main aspect of entire slope unit was considered in safety factor calculation. Finally, regional slope stability characterized by the safety factor would be available; thus, it would be beneficial to sliding prevention and disaster treatment in this region.

Modification of the gravity increase method in slope stability analysis

The gravity increase method (GIM) has an inherent defect that may result in an incorrectly calculated safety factor or result in a failure to obtain the expected outcome. In this study, the error source of the GIM was quantitatively analyzed through theoretical derivation to address this problem. Hence, the modified gravity increase method (MGIM), which can eliminate the error in the GIM, was developed by adding a correction factor to the friction angle during the gravity increase procedure. The MGIM was comparatively studied by applying the GIM, shear strength reduction method (SSR), and MGIM to homogeneous slope models under different dimensions, and an ACADS (Australian Computer Aided Design Society) test was introduced to validate the applicability of the MGIM to heterogeneous slopes. The analysis results proved that the MGIM does not have the inherent defect present in the GIM, and can provide accurate results in the stability analysis of both homogeneous slope and heterogeneous slopes with various slope angle and slope height. Finally, the MGIM and GIM were applied to the numerical analysis of a geotechnical centrifugal model test of a soil slope. The results indicate that the MGIM is capable of capturing the deformation and failure characteristic of geotechnical centrifugal model test of soil slopes.

The Implementation of the Gradual Movement of Sliding Blocks to a New Method for Evaluating the Seismic Stability of Slopes Reinforced by Geotextile

Evaluating the seismic stability of a rock slope typically involves searching for the minimum value of calculated safety factors (SF) for each supposed sliding block. Because only the transient equilibrium is evaluated, the likelihood of any slope failure can be deemed negligible if all the calculated SFs are greater than unity. However, even if some of the calculated SF are less than unity, it cannot be assumed that the slope will collapse. Recently, in the wake of extremely large earthquakes in Japan, the design earthquake standards for nuclear power plants (NPP) have been extended. After the experience of the 2011 off the Pacific coast of Tohoku Earthquake, the designer is expected to consider beyond design basis earthquakes to determine whether more can reasonably be done to reduce the potential for damage, especially where major consequences may ensue [IAEA (2011). IAEA international fact finding expert mission of the Fukushima dai-ichi NPP accident following the Great East Japan Earthquake and Tsunami, Mission report, IAEA]. With this in mind, the method employed to evaluate the seismic performance of the slope surrounding an NPP needs to be capable of doing more than determining the likelihood of failure: it must also consider the process toward failure in the event of an earthquake beyond the design basis. In this paper, a new evaluation flow which considers the failure process is proposed to evaluate the seismic performance of slopes surrounding an NPP. This is followed by confirming the validity of the concepts in the proposed flow chart by re-evaluating centrifuge tests in past literature and the numerical simulations designed for those tests.

Comparison of Safety Factor Evaluation Methods for Flexural Buckling of HSS Welded Box Section Columns

The statistical evaluation of the experimental and numerical results is an essential task in case of resistance model development for civil engineering structures. If a design model is developed which has analytical or empirical background, its safety level has to be confirmed and it should be proved that the developed design method fits the safety requirements of the EN 1990 [1]. However, in the EN 1990 and also in the international literature there are several different safety factor evaluation methods that can be used to check the necessary safety level of the analyzed design method (e.g.: 5% quantile level, 2.3% quantile level, 1‰ quantile level, γM partial safety factor, γM⁎ partial safety factor, β reliability index). In the international literature different calculation methods can be found even for the calculation of the same partial safety factor as well. In the present study the flexural buckling resistance of high strength steel (HSS) welded box sections is analyzed and the application of different safety approaches are demonstrated and compared. The authors investigated the buckling resistance of the analyzed columns by laboratory tests and by numerical simulations and the necessary partial safety factors are determined by different approaches. Based on the comparison tendencies are identified and the differences between the statistical evaluation methods are demonstrated.

PSO-based stability analysis of unreinforced and reinforced soil slopes using non-circular slip surface

Slope stability analysis is one of the most intricate problems of geotechnical engineering because it is mathematically difficult to search the critical slip surface of earth slopes with complex strata owing to the involved multimodal function optimization problem. At present, a minimum factor of safety for a non-circular slip surface in a uniform and unreinforced earth slope can be calculated using several methods; however, for a reinforced soil slope, it cannot be easily calculated because of the additional effect of the reinforcement. One efficient method to search the critical slip surface is particle swarm optimization (PSO). PSO can solve complex non-differentiable problems, and its increasing ease of use has facilitated its application to multimodal function optimization problems in a variety of fields. However, the recommended PSO parameters to calculate the safety factors of unreinforced and reinforced soil slopes, namely the inertia and local and global best solution weighting coefficients, have not been sufficiently investigated. Moreover, the computational efficiency of PSO for safety factor calculation, including computational accuracy and time, has not been clarified. To calculate the unreinforced and reinforced soil slope safety factors, this study considers force and moment equilibriums, including the tensile force of the reinforcement. Firstly, the computational efficiency of the calculation process by PSO was shown to increase the maximum number of slip surface nodes in the calculation of the safety factor. Then, an analysis was carried out to investigate the safety factor sensitivity to the PSO parameters. Based on this analysis, appropriate PSO parameters for the safety factor calculation of unreinforced and reinforced soil slopes were proposed.

Probabilistic and Geotechnical Modeling of an Excavation in the Outskirts of Qaen

Summary An excavation operation for the building purposes is a high-risk activity, which is done for different reasons, such as achieving an appropriate level of the earth for foundation or construction of basements. In this paper, using the Slide 6.0 program the stability of a pit wall in the outskirts of Qaen is investigated at first and then the pit wall stability after using soil nailing with various patterns is analyzed. Using back analysis, sensitivity analysis, and probabilistic analysis, this study presents a comprehensive model for analyzing pit walls, and will be useful for excavation operation in neighboring areas as well. Finally, several pit designs with acceptable safety factors have been proposed for pit excavation. Introduction Due to the growing trend of urban populations, the construction activities are increasing in central and marginal areas of cities. One of the basic concerns in these constructions is the stability of the excavated pit wall. The basic rule of judgment about the stability of a pit wall is the standard safety factor. In the traditional deterministic approach of safety factor calculation, any error or uncertainty in the soil parameters is directly reflected in the results. In recent years, the use of the probabilistic approach that provides additional measures related to the probability of failure and risk rate has become popular. In the probabilistic approach in addition to the mean safety factor, the probability of failure and reliability index are also obtained. Methodology and Approaches To perform a probabilistic analysis of a pit wall, strength properties of the soil layer and the soil density were defined as variable inputs. The coefficients of variation of these parameters according to laboratory experiments were selected. Normal and log-normal statistical distributions were used for the input variable parameters as recommended by USACE. For the efficient performance of the probabilistic analysis, Monte Carlo simulation was used. This way, and using the Slide 6.0 program, the stability of a pit wall in the outskirts of Qaen is investigated with various patterns of soil nailing as the supporting system. Results and Conclusions According to the results of this study, the soil is unstable for excavation operation and employing soil nailing technique and reducing the pit wall slope angle are appropriate steps to achieve a secure condition. Several safe pit designs have been proposed for excavating the pit.

The modelling influence of water content to mechanical parameter of soil in analysis of slope stability

One of the parameters in slope stability analysis is the shear strength of the soil. Changes in soil shear strength characteristics lead to a decrease in safety factors on the slopes. This study aims to see the effect of increased moisture content on soil mechanical parameters. The case study study was conducted on the slopes of Sitinjau Lauik Kota Padang. The research method was done by laboratory analysis and simple liniear regression analysis and multiple. Based on the test soil results show that the increase in soil water content causes a decrease in cohesion values and internal shear angle. The relationship of moisture content to cohesion is described in equation Y = 55.713-0,6X with R2 = 0.842. While the relationship of water content to shear angle in soil is described in the equation Y = 38.878-0.258X with R2 = 0.915. From several simulations of soil water level improvement, calculation of safety factor (SF) of slope. The calculation results show that the increase of groundwater content is very significant affect the safety factor (SF) slope. SF slope values are in safe condition when moisture content is 50% and when it reaches maximum water content 73.74% slope safety factor value potentially for landslide.

Analysis of La Dehesa paleo-landslide. Central Pre-Andes of Argentina

The main objective of this paper is to consider the influence of Quaternary faults as likely triggering factor for rockslides occurrence in the Central Pre-Andes, a region with intense shallow seismic activity. A rockslide deposit was selected as study case, placed in the western flank of La Dehesa and Talacasto (DT) range (31°3′37″ S and 68°46′ 8″ W). Applied methodology includes the characterization of main discontinuities, reconstruction of the topography using a high-resolution digital elevation model, safety factor calculation along the sliding surface and, Newmark displacements estimation for three different hypothetical seismic scenarios, recreated from existing neotectonic local information. Equilibrium-limit method's results confirm that study case, La Dehesa rockslide (LDR), had a stable and safe slope's configuration under static conditions. However, a seismic horizontal coefficient between 0.2 and 0.3 decreases safety factor below the safety threshold. Newmark's displacements for different seismic reconstructed scenarios varies between 4.1 and 15.9 cm, values that agreed with a coherent failure process, likely triggered by Pleistocene to Holocene seismogenic sources in Central Pre-Andes. LDR trigger could be assigned mainly to an earthquake related to La Dehesa Quaternary fault (LDF) activity; however, similar movements produced by neighboring faults should not be discarded. LDR triggering related to climatic conditions is despised. Finally, the methodology presented in this work is easy to reproduce and may be applied to other rockslides located in the mountainous areas of the Central Pre-Andes of Argentina.

Effect of cement injection on sandy soil slope stability, case study: slope in Petang district, Badung regency

Slope is a part of soil topography formed due to elevation difference from two soil surface. Landslides is frequently occur in natural slope, it is because shear force is greater than shear strength in the soil. There are some factor that influence slope stability such as: rain dissipation, vibration from earthquake, construction and crack in the soil. Slope instability can cause risk in human activity or even threaten human lives. Every years in rainy season, landslides always occur in Indonesia. In 2016, there was some landslide occurred in Bali. One of the most damaging is landslide in Petang district, Badung regency. This landslide caused main road closed entirely. In order to overcome and prevent landslide, a lot of method have been practiced and still looking for more sophisticated method for forecasting slope stability. One of the method to strengthen soil stability is filling the soil pores with some certain material. Cement is one of the material that can be used to fill the soil pores because when it is in liquid form, it can infiltrate into soil pores and fill the gap between soil particles. And after it dry, it can formed a bond with soil particle so that soil become stronger and the slope as well. In this study, it will use experimental method, slope model in laboratory to simulate a real slope behavior in the field. The first model is the slope without any addition of cement. This model will be become a benchmark for the other models. The second model is a slope with improved soil that injects the slope with cement. Injection of cement is done with varying interval distance of injection point is 5 cm and 10 cm. Each slope model will be given a load until the slope collapses. The slope model will also be analyzed with slope stability program. The test results on the improved slope models will be compared with unimproved slope. In the initial test will consist of 3 model. First model is soil without improvement or cement injection, second model is soil with cement injection interval 5 cm and third model is soil with cement injection interval 10 cm. The result is the shear strength (ϕ value) the soil is increase from 32.02° to 47.57°. The increase value of internal friction angle (ϕ) shows that an increase in shear strength of the cement improved soil. While, the value of cohesion (c) is zero indicating there is no cohesion in the soil. This is common for sand soil or sandy soil. The calculation of safety factor with GeoStructural Analysis obtained an increase of safety factor from 0.78 if the soil without cement injection to 1.07 and 1.17 if the soil is injected with cement at a distance of 10 cm and 5 cm.

Assessment of Durability of Concrete Structure Subject to Carbonation with Application of Safety Factor

A reliability‐based method for identifying appropriate safety factors for use in predicting the service life (i.e., corrosion‐free life) of concrete structures subject to carbonation is described in this paper. Reinforced concrete (RC) columns located in CO2‐rich urban environments were investigated to estimate their service life. Carbonation depths and cover depths were measured for sound, cracked, and jointed concrete cover conditions. The measurements were used to calculate safety factors for columns subject to carbonation. Goodness‐of‐fit tests were used to obtain optimal probability distributions for carbonation depths and cover depths. A reliability index of 1.28, corresponding to a 10% probability of corrosion initiation, was taken as a threshold for determining the safety factor. The safety factor proposed in this paper can be used to estimate the service life of RC structures subject to carbonation. The sensitivity of the safety factor to the casting method and coefficient of variation of the cover depth were also evaluated.

Study on the Influence of Elevation of Tailing Dam on Stability

This paper takes Yunnan as the object of a tailing, by theoretical analysis and numerical calculation method of the effect of seismic load effect of elevation on the stability of the tailing, to analyse the stability of two point driven safety factor and liquefaction area. The Bishop method is adopted to simplify the calculation of dynamic safety factor and liquefaction area analysis using comparison method of shear stress to analyse liquefaction, so we obtained the influence of elevation on the stability of the tailing. Under the earthquake, with the elevation increased, the safety coefficient of dam body decreases, shallow tailing are susceptible to liquefy. Liquefaction area mainly concentrated in the bank below the water surface, to improve the scientific basis for the design and safety management of the tailing.

High dimensional model representation for reliability analyses of complex rock–soil slope stability

The high-dimensional model representation (HDMR) and its modifications, the fractional HDMR (FHDMR) and hybrid HDMR (HHDMR), are new tools for calculating reliability indexes in stability analyses when several variables with large uncertainties are used to describe rock and soil behaviours. Plain HDMR utilises an inverse reliability analysis for the study of unknown design parameters associated with target reliability index values. This approach uses implicit response functions, named limit state functions, according to the response surface method (RSM). In this study, both the FHDMR and HHDMR are applied to the reliability index calculation of safety factors related to the stability analyses of sliding failure mechanisms in complex formations. These two methods improve the computational efficiency of the RSM in reliability index calculations compared to the HDMR. A case study of Carpathian Flysch rock–soil slopes is presented, and the efficiency of the reliability index calculation is estimated by comparing results with ones from neural network application.

Assessment of slope stability under uncertain circumstances

Slope stability assessment is a difficult geotechnical problem because of the many uncertainties involved. The uncertainties associated with soil parameters are significant, originating from limited and imprecise information, which allows for the soil parameters to be expressed as uncertain variables. The distributions of these uncertain variables are built on the basis of the structure of the soil layers of a slope, and the safety factor of slope stability is defined as a ratio of resisting and acting moments under uncertain environments. The expected value of the safety factor is therefore calculated by utilizing the operational laws of the uncertain variables. The concept of the reliability index of slope stability is also introduced in order to evaluate the risk of slope instability. Three numerical examples, including a homogeneous slope and two non-homogeneous slopes, are used to verify the proposed model; meanwhile, the results are compared with those of the Fellenius method. The numerical results indicate that the proposed model can not only improve the reliability of the calculated safety factor but also reduce the computational complexity compared to deterministic methods. Fifteen project instances taken from the literature are used to investigate the validity of reliability index, and the results illustrate that the reliability index is another useful indicator to assess the stability of a slope.

Study on Calculation of Slope Safety Factor by Strength Reduction Finite Element Method

One of the main topics of slope stability analysis is to determine the safety factor of sliding surface. In this paper, firstly, the basic principle of finite element strength reduction method is introduced. Then the slope stability is analyzed by the finite element strength reduction method, discontinuous deformation strength reduction method and Spencer method respectively. The results show that the error between them is less than 2%, which indicates that the finite element strength reduction method can be applied to the engineering practice.

Long-term strength determination for cooled blades made of monocrystalline superalloys

For the manufacture of blades for modern gas-turbine installations, monocrystalline alloys are used. Traditional methods for the calculation of stressed-deformed state and safety factors for these alloys developed and verified for polycrystalline materials need to be adjusted. This paper deals with methodological principles for an approach to the solving of the problem concerning a finite-element determination of the long-term static strength for cooled monocrystalline blades employed in gas-turbine installations based on the use of two different models (phenomenological and micromechanical) considering the inelastic deformation of monocrystalline superalloys. An analysis has been performed for the distribution of Schmid factors in the spherical triangle for primary and secondary octahedral and cubic slip systems. Calculations are performed using Larson–Miller’s parametric dependences taking into account the crystallographic orientation of the material. A determination procedure for the anisotropy coefficients of long-term strength is described based on data for different orientations. A comparative analysis of the results of finite-element calculations made using phenomenological and micromechanical (crystallographic) creep models for the long-term static strength of cooled monocrystalline blades used in a gas-turbine engine has been performed. It is shown that the location of the most loaded sections of such a blade coincide with the results of calculations according to these models. It has been found that the micromechanical deformation model results in the obtaining of the most conservative estimate for the long-term strength of turbine blades made of monocrystalline alloys. It is shown that the calculations using models for materials with isotropic properties can produce considerable errors in determining the durability of the blades. The possibility is considered for using 1D-, 2D-, and 3D-models for turbine monocrystalline blades in the determination of their durability parameters.