PREFACE. This book has been developed from lectures given by the author during- the past five years, under the auspices of the Dominion Bridge Co. His object has been to teach the elements of bridge and structural design in a simple and practical manner. Arts. I to 14 inclusive treat of the general principles of design, and are illustrated by numerous examples while the remaining Articles are examples of typical structures, in which the stresses are analyzed, the members proportioned, and the details carefully worked out. Both analytical and graphical methods have been employed for obtaining stresses, and the one which seemed best suited for any particular subject has been adopted. But few tables are given, as it was thought unnecessary to repeat information given in any of the rolling mills hand-books. Although the book is intended principally for students and draughtsmen, there are parts which may be of interest to practicing bridge designers. Particular attention is here drawn to Art. 17, which treats of the design of a knee-braced mill building and to Art. 19 which discusses the rivet spacing and web splices in plate girders, in which one-eighth of the web plate as flange area. MONTREAL, March 10, 1905. is counted on CONTENTS. Art. I. Definitions i Page 2. The Composition and Resolution of Forces 2-3 3. Examples in Graphical Statics 4-6 4. The Lever and Moments 7-8 5. Shearing and Bending- Stresses in Beams 9-10 6. Moment of Resistance 1 1 7. Moment of Inertia 12 8. Radius of Gyration 13 9. Formulae Relating to Beams 14 10. Examples in the Computation of Properties of Simple and Compound Sections 14-19 11. Examples Illustrating the Method of Determining the Sizes of Beams 20 12.Columns and Struts 21-23 13. Examples Illustrating Method of Designing Columns and Struts 24 14. Rivets and Riveting 25-26 15. The Complete Design of a Roof Truss for Building with Masonry or Brick Walls Capable of With- standing Wind Pressure 27-32 16. Roof Trusses Supported by Steel Columns 33 17. The Design of a Knee-Braced Mill Building 34-41 18. The Design of a Plate Girder 42-49 19. Plate Girder with One-Eighth of Web Plate Com- puted as FlangeArea 5O53 20. Design for a Warren Girder Highway Bridge 546i 21. Design for SkewWarren Girder Highway Bridge. . .62-67 22. Design for a Pin-Connected Pratt Truss Highway Span 68-88 BRIDGE AND STRUCTURAL DESIGN, Bv W. CHASE THOMSON, M. Can, Soc. C. E. ART. 1. DEFINITIONS. Mechanics is the study of the effect of force upon matter. Force is the action of gravity, wind, steam, etc., causing or tend- ing to cause motion. Matter is any substance whatever, as metal, stone, wood, water, air, etc. A body is any piece of matter, and its weight is the amount of force which gravity exerts upon it. Statics is that branch of mechanics which investigates the stresses in a body produced by forces which keep it stationary, as in bridges and buildings. Dynamics, on the other hand, investigates forces which move the body upon which they act, as in engines and other machinery. Stress is the effect produced by equal and opposite forces, and is measured in pounds or tons. It is equal to only one of the forces, ends of a however. Thus, if two men pull 40 Ibs. each at opposite rope, the stress will not be 80 Ibs., but only 40 Ibs. and if a load of 1,000 Ibs. rest on top of a column, then the reaction of the founda- tion on which the column rests will also be 1,000Ibs., but the stress in column will be equal to but one of these forces, viz. 1,000 Ibs. There can be no stress without a reaction which is always equal to the force acting on body...