Structural engineering - Swain

The present volume is the first of a series treating of the theory and design of structures, embodying the course which the writer has been giving for many years, with amplifications which, it is hoped, will make it a fairly complete treatise for engineers.

Considering the extent of the field, some subjects are omitted, and others touched upon briefly. Foundations, for instance, though extremely important for the structural engineer, are not discussed. There are several satisfactory treatises on that subject, and it is more largely a matter of judgment, experience, and practical detail, and less dependent on fundamental principles, than the topics here included.

It was originally intended that this work should comprise two volumes only; but the theory of structures is so intimately connected with that of the strength of materials, of which it is, strictly speaking, a continuation, that it was decided to limit this first volume to the latter subject. There are many excellent works on the strength of materials, but it was necessary for the writer, in order to present the theory of structures in the way that he prefers, to cover a good part of what is usually included in strength of materials; and if the writer's views and methods are of value, it is hoped that this volume will prove attractive and useful to other than structural engineers.

In connection with the strength of materials, it is desirable that the engineer should be familiar with the fundamental properties of the materials themselves, including their principal physical characteristics, and the most important matters connected with their strength. There are several excellent and exhaustive works on the subject of materials, but it has been thought desirable to prepare a briefer one particularly designed to accompany this volume on strength of materials.

Another volume will complete the theory and the design of simple structures of wood, metal, and masonry; and a final volume will treat of more complicated and statically indeterminate structures.

The first two volumes, namely the present volume on strength of materials, and the one on the fundamental properties of materials, are completed; the last two are well on the way to completion.

The aim of the present volume is to give a complete, clear, and simple discussion of the fundamental principles of the strength of materials applicable in the design of structures of various kinds, not merely of framed structures but of those of masonry and concrete also.

It is believed to contain all that is needed for machine design also, and so is suited for any student of engineering.

Some books on this subject are so brief that they do not serve as a foundation for further study, while others are so encyclopedic that the principles are likely to be obscured by a mass of detail. The writer believes that every student of engineering should be required to study a treatise on the strength of materials, and that such treatise should go beyond the limits of the course which his curriculum provides, thus giving him material for further study. By reference to original sources and other works, it should also put him in a position to pursue the subject as far as our present knowledge permits. To accomplish this, has been the aim of the present volume. It is recognized that the curriculum of most engineering schools will not permit the student to go through the whole of this volume. Indeed, the importance of the subject and the necessity of getting thorough and accurate fundamental notions are not sufficiently appreciated. The teacher will be able to omit such parts of the present work as he considers least important for his own purposes, or which his time does permit him to cover.

A brief statement follows suggesting the portions of his work which may be so omitted.

In the present volume there is perhaps little that cannot be found in other works on the subject, but it is believed that the method of presentation is somewhat novel, and that there are original points of view and methods in many places. The material will, it is hoped, be found to be thoroughly digested and presented in such a way and with such abundant references that it may serve as a guide for more extensive study. The writer is acquainted with most of the published works on the subject and is indebted to many of them. Acknowledgements are made in the proper places.

There is some repetition, but the writer does not consider it objectionable. The student of any subject must continually repeat and review if he wishes to impress on his mind.

The student of this book is assumed to possess a copy of the Pocket Companion issued by the Carnegie Steel Company, and he should familiarize himself with the various shapes used in steel construction and should check some of the results and tables in the Companion as he learns the principles involved. It is believed that the work will be found appropriate for students in Mechanical and Electrical Engineering as well as for those in Civil Engineering. Students of any branch of engineering should, in the writer's view, be thoroughly grounded in the strength of materials, but some parts of the present work may be omitted by students who do not intend to pursue the subject of structures.

The writer will be grateful to any reader who will point out any errors, typographical or others, which may be found in this book, and he will welcome suggestions of possible improvements.

This volume Is the second of the writer's work on Structural Engineering, which work is intended to cover the parts of the subject most important for the engineer and especially for the engineering students in technical schools.

It was originally intended that the present volume should form the second part of the volume on the Strength of Materials, with which it is closely connected; but in order to avoid making the first volume too bulky, this part is published separately. It does not deal in detail with processes of manufacture, which should be studied, as far as necessary, in the more specialized books herein referred to; but is intended to give the fundamental properties of the principal materials, which should be familiar to the engineer. Thus it does not overlap or replace the detailed works on Materials, but brings together logically, and it is hoped clearly, the fundamental properties, the constitution and physical structure, the importance and effect of various ingredients, the effect of different treatments, and the significance of the specifications used to secure desired properties in the material to be employed

The book is intended to be used in connection with the previous volume on the Strength of Materials, and the needs of constructing engineers have been mainly considered. The point of view of the practical engineer has been emphasized throughout, as it was in the earlier volume. However incomplete this work, it may be of some interest to the student of the subject to see what portions of it the writer, who has done as much practical engineering work as teaching, considers most important for the constructing engineer to know.

It is hoped that this volume will be found a suitable continuation of the first volume of the series. The third and fourth volumes, dealing respectively with the Theory and Design of Elementary Structures and with structures of more complicated character, are well under way.

This volume, which is the third in my work on Structural Engineering, comprises:

1. The theory of statically determined framed structures, by analytical and graphical methods. The subject of graphical statics is presented in a comprehensive manner, showing how any problem of statics may be solved graphically as well as analytically.

2. The theory and design of masonry structures, giving the fundamental principles and the methods of their application, and the theory of earth pressure.

Reinforced concrete is not treated in this volume.

The next volume, which is nearly completed, will treat of the design of framed structures and of beams and girders, with the principles governing dimensioning; and it will also contain an extended chapter in which the theory and design of structures of reinforced concrete are discussed. Statically undetermined structures, such as the reinforced concrete arch, will be treated in the fifth and final volume of the series, which is about half completed.

The present volume and the succeeding one contain essentially the course which the writer has been giving for many years at the Massachusetts Institute of Technology and at Harvard University, considerably extended and brought to date. It is hoped that they will meet the needs of practicing engineers as well as of students in technical schools.

A course of four years in a technical school, in the writer's opinion, does not permit of doing more than two things, or rather, of attempting to do them, namely:

1. To train the student to think and to acquaint him with the principles governing scientific investigation.

2. To show him the elementary fundamental principles of the branches of engineering.

Unless he has learned these two things, the student is not qualified to pursue the higher or more complicated branches of the subject with understanding. Realizing this, the writer has never attempted to teach statically undetermined structures in an undergraduate course. Many schools do attempt this; but from the writer's experience it results in making the student do things which he is shown how to do, without clearly understanding why he is doing them ; or else it results in a narrow specialization which prevents a student from being a broadly cultivated engineer. It is impossible to build securely on an insufficient foundation.

This seems to the writer to be what is too often attempted. The school cannot make an engineer; it can only give fundamentals, if it does its work thoroughly. Indeed, all that any teacher can do is to help the student to teach himself. The only real education is self-education, as was long ago pointed out by William Ellery Channing, in his address on Self Education. The teacher may of course give rules and formulae, and show the student how to use them; but this is merely vocationalizing education and making a man a machine which performs certain motions without understanding the reason and purpose of them. It is not true education. True education is drawing out, or developing the innate powers of the student, not putting facts into him. The writer is concerned only with true education.