With portable cranes means must be provided to ensure the requisite stability against overturning; this is done by weighting the tail of the revolving part with heavy weights, and in steam cranes the FIG.
Overturning backwards than forwards.
In the latter case the overturning tendency begins as soon as the load leaves the ground, but ceases as soon as the load again touches the ground and thus relieves the crane of the extra weight, whereas overturning backwards is caused either by the reaction of a chain breaking or by excessive counterweight.
From consideration of the rigid triangular frame described above, it is clear that the " overturning " force acts horizontally from the centre of gra'Vity, and that the length of its lever arm is, at any instant, the vertical distance from the centre of gravity to the level of the outer rail.
If therefore the outer rail is laid at a level above that of the inner rail at the curve, overturning will be resisted more than would be the case if both rails were in the same horizontal plane, since the tilting of the vehicle due to this " superelevation " diminishes the overturning moment, and also increases the restoring moment, by shortening in the one case and lengthening in the other the lever arms at which the respective forces act.
For example, what is a safe speed at a given curve for an engine, truck or coach having the load equally distributed over the wheels may lead to either climbing or overturning if the load is shifted to a diagonal position.
Armed with it he passed safely into heathen Germany and began a systematic crusade, baptizing, overturning idols, founding churches and monasteries, and calling from England a band of missionary helpers, monks and nuns, some of whom have become famous: St Lull, his successor in the see at Mainz; St Burchard, bishop of Wurzburg; St Gregory, abbot at Utrecht; Willibald, his biographer; St Lioba, St Walburge, St Thecla.
Interpreted in the most general sense, these decrees, which enacted that the council of Constance derived its power immediately from Jesus Christ, and that every one, even the pope, was bound to obey it and every legitimately assembled general council in all that concerned faith, reform, union, &c., were tantamount to the overturning of the constitution of the church by establishing the superiority of the council over the pope.
For safety against overturning they considered a factor of 2 sufficient.
Passive resistance; but it contained a military element who had more courage, and who had learned their power when Ismail employed them for overturning his constitutional ministry.
While Spanish navies were exploring the ocean, and Spanish paladins were overturning empires, Charles V.
In no case shall the overturning moment due to wind pressure exceed seventy-five per centum of the moment of stability of the structure.
The next class of dam to be considered is that in which the structure as a whole is so bound together that, with certain reservations, it may be considered as a monolith subject chiefly to the overturning tendency of waterpressure resisted by the weight of the structure itself and the supporting pressure of the foundation.
Masonry dams are, for the most part, merely retaining walls of exceptional size, in which the overturning pressure is water.
As the pressure of water is nil at the surface and increases in direct proportion to the depth, the overturning moment is as the cube of the depth; and the only figure which has a moment of resistance due to gravity, varying also as the cube of its depth, is a triangle.
Thick of a monolithic dam, subject to the pressure of water against its vertical side to the full depth ab= d in feet, the horizontal _ eL 2 pressure of water against the section of the dam, inI creasing uniformly with the depth, is properly represented by the isosceles right-angled triangle abe, in which be is the maximum water-pressure due to the Cent full depth d, while the area 2 abe = d is t h e total hor12 d3 6 If x be the width of the base, and p the density of the masonry, the weight of the masonry in terms of a cubic foot of water will be acting at its centre of gravity g, situated at 3x from the outer toe, and the moment of resistance to overturning on the outer toe, p x 2 d (2) In countries where good clay or retentive earth cannot be obtained, numerous alternative expedients have been adopted with more or less success.
Then a is the resultant horizontal pressure with an over turning moment of (I) Equating the moment of resistance (2) to the overturning moment (I), we have pxzd =d3 3 6 and x =?2 p ..
(3) That is to say, for such a monolith to be on the point of overturning under the horizontal pressure due to the full depth of water, its base must be equal to that depth divided by the square root of twice the density of the monolith.
Next, Rankine pointed out that, in a structure exposed to the overturning action of forces which fluctuate in amount and direction, there should be no appreciable tension at any point of the masonry.
We have hitherto considered only the horizontal overturning pressure of the water; but if from originally defective construction, or from the absence of vertical pressure due to weight of masonry towards the water edge of any horizontal bed, as at ab in fig.
14, water intrudes beneath that part of the masonry more readily than it can obtain egress along bc, or in any other direction towards the outer face, we shall have the uplifting and overturning pressure due to the full depth of water in the reservoir over the width ab added to the horizontal pressure, in which case all our previous calculations would be futile.
Years after this, and about fifteen years after the dam was first brought into use, it overturned on its outer edge, at about the level indicated by the dotted line just above the counterfort; and there is no good reason to attribute to the movement of 1884, or to the vertical cracks it caused, any influence in the overturning of 1895.
Directly this occurred, the front part of the wall was subject to an additional overturning pressure of about 35 ft.
His refusal united all the Jacobins in the project of overturning the monarchy by force.