# Treatise on the Theory of the Construction of Bridges and Roofs

J. Wiley & sons, 1883 - Bridges - 249 pages

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Page 243 - If three forces acting at a point are in equilibrium they can be represented in magnitude and direction by the three sides of a triangle taken in order.
Page 243 - If three forces, acting at a point, be represented in magnitude and direction by the sides of a triangle taken in order, they will be in equilibrium.
Page 177 - Bi the reaction at the point of support Ai. This is the equation of a parabola whose axis is vertical and whose vertex is over the middle of the truss. Remark. — The usual method of computing the strains upon the pieces of a truss is that of adding and subtracting for each consecutive piece, as shown in the previous methods for calculating strains. General formulas are used in connection with these methods...
Page 30 - Pig. 151. \CHORO distinction is quite unnecessary in an analytical point of view, as will be seen hereafter, but it is so common in practice that it will not do to ignore it. A Main-Brace is a brace which inclines from the end of a truss towards the centre, as in Fig. 151. A Counter -Brace is one which inclines from the centre and towards the ends.
Page 193 - The inclined pieces AC, and BC, Fig. 207, which support the roof are called rafters. When the roof is light, the roof boards DE are placed...
Page 200 - ... broke under a strain of 42 Ibs. per square foot, whilst a tornado was passing near by. During the severest gale on record at Liverpool, England, there was a pressure of 42 Ibs. per square foot directly upon a flat surface. During a very violent gale in Scotland, a wind-gauge once indicated 45 Ibs. per square foot. Buildings which are more or less protected will not be subjected to such pressures. Although there are high winds at Ann Arbor, yet no such gales as those mentioned above have ever...
Page 73 - ... the load on the footing. The purpose of the ribs and base is to resist the tendency to break, due to this uniformly distributed load on the footing. Failure would generally occur through the bending action of the portion of the base projecting beyond the box. The moment on this may be figured as for a beam fixed at one end and free at the other and loaded uniformly with the load per unit of bearing surface. Taking one rib and the base half way on each side between the next rib would give a section...
Page 199 - Some say that snow is equivalent to from -jJj,- to -J- of its depth in water, while others say that it may be equivalent to J its depth of water. European engineers consider that six Ibs. per square foot is sufficient for snow, and eight Ibs. for the pressure of the wind, making fourteen Ibs. fo,r both. Trautwine says that not less than twenty...
Page 193 - ... purpose of receiving the roof proper. AB is a tie, and F and G represent the ends of posts. The frame ABC is called a roof truss. 689. Roof Trusses have a great variety of forms, and differ greatly in the details of their construction. All the trusses which have been discussed in the preceding pages are suitable for this purpose in many cases. Some other forms are given in the following pages. 690. General Data. A roof truss is required to carry its own weight, the weight of the purlins, the...
Page 200 - Tredgold recommends the use of 40 Ibs. per square foot. A gauge in Girard College broke under a strain of 42 Ibs. per square foot, whilst a tornado was passing near by. During the severest gale on record at Liverpool, England, there was a pressure of 42 Ibs. per square foot directly upon a flat surface. During a very violent gale in Scotland, a wind-gauge once indicated 45 Ibs. per square foot. Buildings which are more or less protected will not be subjected to such pressures. Although there are...