Determination Of Safety Factors Research Articles

Determination of safety factors for load testing of falsework system following the current Vietnamese standards

The partial safety factor used when carrying out load testing on falsework is not defined in any current Vietnamese standards. On the other hand, the requirements for calculation as well as load testing of falsework are well defined in the European standards system. This paper presents the method for determining of partial safety factor for falsework load testing.

A Deterministic Method for Evaluating Safety Factor of Deep Excavation Stability against Groundwater Inrush Equivalently Considering Soil Uncertainty

In current design specifications for deep excavation, the determination of safety factors against groundwater inrush only considers the self-weight effect of soil mass at the bottom. However, the shear strength and its spatial variability in a cement-solidified bottom layer also plays an important role in safety factor estimation. Based on that, in this study, the strength reduction method was introduced into reliability analysis of deep excavation engineering, and the influence of shear strength and its spatial variability of cement-solidified soil on the stability of deep excavation is studied. Furthermore, a deterministic analysis method that can equivalently consider soil uncertainty is proposed and verified.

Mechanical investigations supported by DIC of structural components intended for operation

The paper deals with experimental attempts for determination of the mechanical resistance of various components subjected to static loading by analysis of displacement values in a 3D coordinate system using a non-contact testing method. The problem is studied on the basis of results from tests of the wheelchair and SUV’s wheel, supported by means of a PONTOS 5M Digital Image Correlation (DIC) system enabling determination of the patterns deflection at discretised facet measuring zones of an element. The objects tested extend a knowledge on the components’ behaviour under static loading within their loading capacity. Data collected in the experiments are expressed by variations of the resultant vector of deflection in the 3D coordinate system and images under loading and unloading stages as well. The results enabled to indicate the weakest zone in the wheelchair and to express an influence of the foot tire on the rim edge, giving necessary knowledge on the mechanical resistance of tested components. In case of the wheelchair a rear side and axle represent the weakest regions, while for the wheel a rim edge is the most loading sensitive region on the tire guard with respect to safety of the operational process. All data captured by DIC system as a function of time can be directly used for modelling and improving a suitability of the selected components since they can be employed as the limit levels during determination of safety factor. The experimental approach applied to the SUV wheel investigation can be also used as a procedure for wheels of other type vehicles tested either in laboratories of research institutions or technical universities.

A Study on the Influence of Vegetation Growth on Slope Stability

Vegetation plays a major role in terms of slope stability. Roots of grass and trees can increase the strength properties of soil which improves the stability of slope. A natural slope consists of grass and infinite number of trees inclined in different directions along with inclined roots. The aim of the paper is to study the effects of vegetation growth on slope stability for different root reinforced soil depth by varying tree inclination (along with roots), root spread and tree spacing for different slope geometry. The study involves determination of safety factor (FOS) of natural slope existing with and without vegetation growth (such as only grass, grass and trees). GeoStudio Slope/w software with limit equilibrium method was used for stability analysis of different slope inclinations. A tree was modelled as a point load and its roots were represented as reinforced soil properties with anchors and only as root reinforced soil. When compared to the bare slope, it was observed that there was an increase in FOS of slope on both the models of vegetation. Variations in FOS by varying root reinforced soil depth, tree inclinations and spacings were reported for different slope geometry and compared. Considering all these parameters, an empirical corelation for computation of vegetation influenced FOS has been developed. This study provides a mechanical accountability of vegetation cover on the stability of slopes.

Determination of Safety Factor for Rock Mass Surrounding Tunnel by Sudden Change of Equivalent Plastic Strain in Strength Reduction Method

The safety factor of rock mass surrounding tunnel can be determined using the strength reduction method (SRM), furthermore, it is very important to solve the criterion of critical state. For the stability estimation of rock mass surrounding tunnel, there is need to discuss that it is preferable to use the same criteria for the slope stability, such as non-convergence of finite element calculation, penetration of plastic strain and sudden change of horizontal displacement. The safety factor can be determined by sudden change of equivalent plastic strain in relationship between a reduction coefficient of strength parameter and equivalent plastic strain. This method is based on the elasto-plastic finite element method (FEM) and the SRM by ABAQUS and Mohr–Coulomb yield criterion. Simulation results using this method show how a safety factor varies with geometries, friction angles and cohesions for circle and square tunnels. Simulation results also show the safety factor varying with quality change of rock mass, pore water pressure and tunnel depth.

FDA Guidance on Medical Devices Containing Nitinol

Abstract New FDA guidance for Nitinol used in medical devices includes clarification on the determination of safety factors, the requirements for corrosion testing, and proper labeling of potentially harmful elements.

Deformation analysis of a construction pit in high-plasticity clay

In Slovakia, construction process already begins in less suitable locations. Such a location is also situated in Podhorie, small village near the city of Žilina. The subsoil is formed by high-plasticity clay with claystone in lower position. This article deals with the analysis of the influence of various input parameters as well as Rinter mesh discretization on the determination of safety factor – M SF. The Mohr-Coulomb constitutive model was used in numerical model with respect to availability of input parameters. The ability to identify the parameter with the biggest impact on the resulting value of safety factor is an indisputable benefit. Various studies have been published on this topic. In our case, cohesion c had the biggest influence on the M SF parameter when reducing shear parameters. In the future, the authors will compare the achieved results of numerical modelling with the actual deformations of the structure.

Determination of safety factors for structural bamboo design applications

ABSTRACT Use of bamboo as a construction material has world-wide potential given it is lightweight, highly-renewable, and fast-growing. The pitfall lies largely in the variability of the material properties reported by numerous investigators. Previous research has sought to correlate various material properties to external factors but results are conflicting. This paper applies the same approaches previously applied to other structural materials using U.S. approved standards. It outlines the significance of a common set of material properties with the goal of identifying the necessary safety factors designers can incorporate when using bamboo to ensure a given level of reliability and an acceptable failure rate. These results when combined with international building codes for bamboo can allow for greater structural application of bamboo in architectural designs.

A general framework for coupled hydro-mechanical modelling of rainfall-induced instability in unsaturated slopes with multivariate random fields

An accurate estimation of rainfall-induced instability of slopes for extremely nonhomogeneous materials such as lignite mine spoils is a major challenge. This paper investigates the stability of nonhomogeneous soil slopes with respect to slip surface development, size of sliding volume, and determination of safety factor. Specified dependent random variables are cross-correlated using a multivariate Gaussian copula, the use of which provides a faster and more accurate representation of the inter-dependent properties of randomly-distributed soil. A Monte-Carlo simulation is used to generate a series of multivariate random fields for slopes. These are then implemented in Abaqus and analysed under constant rainfall conditions using a fully coupled hydro-elasto-plastic model. The resulting stress, strain, pore pressure, and displacement data are further processed in MATLAB to evaluate critical slip surfaces and safety factors. Results indicate that the factor of safety in a homogenous case is overestimated compared to the nonhomogeneous condition, while the sliding volume is underestimated. Moreover, the factor of safety decreases as the rainfall simulation continues and the probability of failure increases to nearly 100% after 10 days of rainfall. The framework developed in this paper can provide guidance for conducting relatively inexpensive probabilistic analyses.

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.

Modelling and Simulation of Laser Welded Joints of Reinforced PP and PC Plastics

Welding of composites decreases their material strength. Proper evaluation of FEM simulations is necessary for correct design and safety factor determination. Neat and reinforced PP and PC specimens were measured on a testing machine to obtain their material properties. Experimental tensile curves were used as inputs in FEM simulations. 15 combinations of specimen were welded on laser work machine and afterwards the welded joint strength was measured on the testing machine. The results of shear tests and FEM simulations are compared in this paper. Also the influence of fiber presence in composites on welded joint strength is discussed. At the end suggestions for safe machinery design of laser welded reinforced composites are given.

Determination of Safety Factors for Mango Fruit Paperboard Transport Crates under Refrigerated Conditions

The use of corrugated board packaging is very popular in most industry sectors, but the food industry is one of the main consumers. Special requirements are placed on corrugated board in the food industry since the level of humidity necessary may be as high as 85-90% rH and this can greatly influence on the performance of the packaging. This influencing circumstance is taken into account in this paper when estimating a safety factor aimed at reducing risk. Knowing the safety factor can save transport and material costs, and can also prevent serious damage during the distribution of goods. The aim of this study is to determine the influence of humidity, pre-compression and load carriers on the stability of corrugated board mango fruit crates and thus to determine the safety factor. The results show that it is possible to calculate the safety factor by measuring realistic static stresses. Further researches into determining the dynamic stresses are required so as completing the calculation of the safety factor.

NUMERICAL MODELLING OF SLOPE STABILITY IN OPEN PIT LIGNITE MINES: A COMPARATIVE STUDY

Slope stability of an open pit lignite mine was studied using numerical methods (FEM and FDM), by means of three different software packages whose performance was compared and similarities - differences were identified. Plane strain analyses were performed using the shear strength reduction technique under drained conditions and Mohr-Coulomb constitutive models. Based on the results, all three programs demonstrated qualitatively a good agreement in the determination of safety factors and the kinetics of the collapse mechanisms. Small differences were observed in terms of shear strains localizations. Important differences were evident in the development of plastic (shear) and tensile failure indicators. Nevertheless, the problem under examination may be addressed satisfactorily by all three programs.

A comprehensive analysis of pipeline safety factors and of the basic mechanical properties of pipe steels

This PAPER presents an analysis of standard strength calculations for pipelines using allowable stresses and limit states, based on the quantitative determination of safety factors according to yield strength and ultimate strength and developed from decades of practice both in Russia and abroad. A new scientific background for design analysis and substantiation for safety factors is presented, quantitatively taking into account all basic operational, technological, and construction factors, including the effects of ageing, the degradation of pipe steels and pipes, and

Method of Determination of Safety Factor on Example of Selected Structure

The article shows a method of determining safety factors of a frame steel structure of the dump body in a vehicle used in the agricultural transport. The focus is on the method of use of the machine along with indicating the situations where a load-bearing structure is particularly exposed to damage. The determined values of safety coefficients are confirmed with the data obtained from long-term operation of machines manufactured based on the same technology. Long-term operation has not shown any cases of damage to the structure due to an overload.

Discussion and Suggestion for the Design of Slope Anchor Bolt

In the design of anchor bolt for slope reinforcement, determination of safety factor, anchorage length and free part length, choosing anchor-type were closely linked with the practical situation and experience of the designer. In this paper, in terms of above four aspects, some problems in the process of design have been discussed and corresponding solutions have also been put forward based on the codes and personal experience.

Study on the Determination of Safety Factor in Calculating Building Fire Evacuation Time

How to deal with the uncertainty in calculating building fire evacuation time is the key issue of building fire design and evaluation, and is the foundation of result credibility of evacuation safety design and evaluation. Based on the study of uncertainty in calculating evacuation time, this paper put forward a safety factor determination method on the basis of fuzzy comprehensive evaluation, this method can solve the uncertainty problem effectively.

A Probabilistic Safety Factor for Defect Assessment of Water Pipes Subjected to Water Hammer

The aim of this paper is to determine the probabilistic safety factors for water pipes exhibiting surface defects such as gouges. The pipes are located in a water network that consists of a pump, a reservoir, and five pipe sections. Three different materials usually used for water pipes have been studied: cast iron, pipe steel, and polyvinyl chloride (PVC). The water pipes are subjected to the water hammer phenomenon, which is considered to be the loading condition. The overpressure due to water hammer is calculated for each pipe connection with a software program. The circumferential stress induced by the overpressure is then evaluated. Probabilistic safety factors associated with low failure probability are determined using a notch failure assessment diagram (NFAD). Fracture toughness, yield stress, and gouge depth are assumed to be randomly distributed to allow the determination of safety factors by Monte Carlo and FORM/SORM methods. A comparison of pipe material behaviour is then made by means of probabilistic safety factors. For the studied water network it is shown that the probabilistic safety factor is acceptable for steel and cast iron pipes but not acceptable for PVC pipes because its value is lower than 2.

Criteria for rapid sliding I. A review of Vaiont case

Vaiont slide has been represented by a model of two interacting evolutive wedges. Mass conservation during the motion implies that the upper wedge transfers mass to the lower one through an internal shearing plane. The model respects available in situ observations. It was formulated in dynamics terms. Outcomes of the analysis are the determination of safety factors of the valley before dam impoundment, and the calculation of run-out distance once the motion starts. Rock strength degradation as motion develops has also been included. This degradation, even if it is intense, was unable to explain the very high estimated landslide velocities.

تحلیل سینتکی، محاسبه توان مصرفی و تعیین ضریب ایمنی ماشین پوست کن پسته نوع دو قفسه ای ساینده

Pistachio is one of the strategic products of our country, Iran, which takes a lot of time yearly to be processed, So doing scientific and applicable researches about it's power demand through the different process stages, can play an important role in power demand and expense decreases. Based on the achievements of researchers, pistachio peeling stage takes the highest amount of energy compared to other stages and due to the orientation of pistachio peeler development toward the corrosive cage types, in this study we have tried to calculate the power demand and focus on kinetic analysis and safety factor determination of a two-corrosive-cage pistachio peeler. According to the achieved results, this type of pistachio peeler has the maximum power demand of 41.8 KW and the 2.1 safety factor. Key words: Pistachio, Pistachio peeler, peeling power, safety factor.