Mean Factor Of Safety Research Articles

Tree Form, Height Growth, and Susceptibility to Wind Damage in Acer Saccharum

The influence of tree dimensions on efficiency of height growth was analyzed for Acer saccharum (sugar maple), an important shade-tolerant species of the northeastern United States. Support efficiency was analyzed in terms of the ratio of actual trunk diameter to the minimum required to keep the tree erect (the stability safety factor). Susceptibility of trees to wind was computed in terms of tree dimensions and was also estimated from measurements of catastrophic storm damage to sugar maple in northern Wisconsin. A trade-off was expected between height growth efficiency, which is maximized by a minimally designed trunk, and ability to resist storm winds. The analysis included canopy trees, suppressed saplings, and more rapidly growing saplings with apical dominance, so that the form of sugar maple could be evaluated throughout its life cycle. The lowest stability safety factors were observed in the saplings with apical dominance, which had a mean safety factor of 1.8, indicating an efficient form for height growth. The suppressed saplings were somewhat thicker trunked, while canopy maple had trunks ranging from 2 to 6 times the minimum diameter required to keep trees erect in the absence of wind. The stability safety factor increased with trunk diameter in canopy trees, but so did trunk breakage due to catastrophic winds. Calculations of wind-generated bending moments suggest that the greater vulnerability of large trees to wind is due to the loss of flexibility caused by increased girth, and to the expected increase in wind speed with height in the canopy. Comparison of these results for sugar maple with a similar analysis of Populus tremuloides (aspen), a shade-intolerant species with short-lived ramets, indicates that maple trees have greater stability safety factors than aspen and are more resistant to catastrophic wind. Maple saplings with apical dominance approached the minimal design of aspen, but were growing in more sheltered conditions beneath a maple canopy.

Natural slope reliability : Chowdhury, R N Proc 4th Australia-New Zealand Conference on Geomechanics, Perth, Western Australia, 14–18 May 1984V2, P601–606. Publ Barton: Inst of Engineers, 1984

An approach to estimating the reliability of natural slopes is outlined. The problem is defined in a three-dimensional context and attention is given to the spatial variability of shear strength. The concept of a most probable extent of failure is explained. The influence of the lateral extent of failure on the mean safety factor, the critical failure length and reliability is demonstrated by means of an example. (Author/TRRL)

Load Capacity of Row of Shear Late Connectors

Based on 69 tests, recommendations are made for immediate revision o design standards and necessary additional research on timber connectors. he mean safety factor for four‐connector joints is alarmingly low at .88 for the first series of 34 specimens and increases to 1.21 for the 20 tests of he second series from a new shipment of billets. The mean safety factor for 5 three‐connector tests is 1.06. Tensile strengths perpendicular to the glueline re reported and compared with tests reported in 1975. The strength of the test aterial is about 1/3 to 1/2 of that expected. The low safety factors are attributed o a combination of the poor distribution of loads among connectors and he low perpendicular to glueline tensile strength. A finite element stress analysis n single connector joints is used to investigate the effect of varying end istances.

Risk analysis of slopes and its application to slopes in Canadian sensitive clays

The problem of defining better measures of the safety of slopes has been approached from a probabilistic point of view. Using a mechanistic description of stability (the method of slices), a first order probability analysis was implemented in order to allow for a rational evaluation of the different sources of uncertainty involved. A preliminary sensitivity analysis shows that the uncertainties in the cohesion parameter, the pore-pressure and the method of analysis are the relevant ones in governing the resulting uncertainty in the slope safety. The method developed serves, however, to predict the probability of failure of a given slope once the different types of uncertainty can be quantified. The analysis of an actual case of slope failure in sensitive clay deposits leads to a number of graphs showing the variation of risk with (a) level of uncertainty in the involved parameters, and (b) the degree of correlation of soil properties. A relationship between mean safety factor and probability of failure is then developed for the conditions likely to prevail in Champlain Sea deposits. This relationship compares well with previous published results based only on empirical observations. Le problème de la détermination de meilleures mesures pour la sécurité des pentes a été approché au point de vue probabilité. En utilisant une description mécanique de stabilité (la méthode des tranches), une première règle d'analyse de probabilité fut exécutée afin de permettre une évaluation rationnelle des différentes sources d'erreurs en cause. Une analyse préliminaire de sensibilité montre que les erreurs relatives au paramètre de cohésion, à la pression interstitielle et à la méthode d'analyse, sont les plus importantes en ce qui concerne les erreurs finales dans la securité des pentes. La méthode développée sert néanmoins, à prédire la probabilité de rupture d'une pente donnée, une fois que les différents types d'erreurs peuvent être quantifiés. L'analyse d'un cas réel d'une rupture de pente dans des dépôts d'argile sensible au remaniement, conduit à un nombre de graphiques montrant la variation du risque avec: (a) les erreurs dans les paramètres en jeu, et (b) le degré de corrélation des propriétés du sol. Une relation entre un facteur de sécurité moyen et une probabilité de rupture est alors établie pour les conditions probablement dominantes dans les dépôts de mer de Champlain. Cette relation correspond bien aux résultats publiés antérieurement et basés seulement sur des observations empiriques.