Practical Treatise on the Construction of Iron Highway Bridges: For the Use of Town Committees ; Together with a Short Essay Upon the Application of the Principles of the Lever to a Ready Analysis of the Strains Upon the More Customary Forms of Beams and Trusses

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J. Wiley & sons, 1890 - Bridges - 144 pages
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Page 121 - ... Hence P5 is equal and opposite to the resultant of the other four* or the forces are in equilibrium. COR. The proposition is true of forces which do not lie all in one plane. For the proof is independent of this supposition. 25. SCHOLIUM. When three forces are in equilibrium, any three lines, taken parallel to their directions, will form a triangle, the sides of which respectively will represent the relative magnitudes of the forces ; but when there are four or more forces this will not hold,...
Page 120 - That is, if two forces are represented in direction and intensity by the adjacent sides of a parallelogram, their resultant will be represented in direction and intensity by that diagonal which passes through their point of intersection. This principle is called the Parallelogram of Forces. The operation of finding the resultant when the components are given is called Composition of Forces ; the reverse operation is called Resolution of Forces. When two forces are applied at the Filr...
Page 92 - ... his signature, which must be written in full. When firms bid, the individual names of the members shall be signed in full, and the firm name added. 6. The name of the contractor must be filled in the blanks left for that purpose. 7. The City of___ - reserves the right to reject any or all bids.
Page 99 - OF MOMENTS. 99 beam is supported by either abutment, all that is necessary to be done is to multiply the shorter or longer segment into which its centre of gravity divides the beam (according to the above law) by the weight, and then divide by the product by the sum of the segments, which is, of course, the same as the span. For example, supP A '1 ... 20 FIG.
Page 82 - Roman sheet-iron capitals about half way down the posts ! The result is that, at a little distance, the spectator beholds an arcade, without any visible means of support for a distance of 340 feet. To be thoroughly consistent, the architect (heaven save the name !) of this constructed " decoration " should have at least sanded his sheet-iron when painted, and marked out in strong lines the joints that masonry of similar forms suggests. About one mile north of this bridge, a noble structure spans...
Page 80 - You may take any single slaveholding county in the Southern States, in which the great staples of cotton and sugar are cultivated to any extent, and confine the present slave population within the limits of that county. Such is the rapid natural increase of the slaves, and the rapid exhaustion...
Page 82 - Such a principle conscientiously kept in view cannot but result in else than good work. Its violation results in a senseless fraud demoralizing to the taste of the community where such violations may occur. Public works, in a certain sense, play a part in the education of a people, and their authors and builders have consequently to that extent a responsibility in addition to the mere utilitarian idea of endurance and safety.
Page 82 - ... etc., for their aesthetic effect, thousands of dollars have been spent in actually covering up the trusses to a great extent with sheet-iron, forming an arcade as it were of great massiveness, by arching between the posts of the trusses, the arches springing from large Roman sheet-iron capitals about...
Page 118 - Power-riveting is so superior in all respects to hand-riveting that a higher unit of strain, by probably 10 per cent., can be used under the former system; so that if it is considered proper to strain hand-rivet work up to 13,500 lbs. per square inch, work riveted up by steam or hydraulic power can be safely proportioned on a basis of 15,000 lbs.
Page 61 - ... a higher factor of safety. It is probable that this difference is not less than 20 per cent ; so that when a pin bridge is called for, having a factor of five, a...

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