The fourth edition of the Specification for Steel Structures for Buildings, is, in many respects, a completely new document, differing both in content and in form from the previous three editions of 1924, 1930 and 1940. This. has been occasioned by the desire to cast the Specification in a manner acceptable to the National Building Code, and suitable for adoption by municipalities. A great deal of work has been occasioned by this particular policy, as the members of the Committee, representing, as they do, so many interests, have not all been equally impressed with the necessity of conforming to requirements of bodies other than the Canadian Standards Association and a great deal of patience, toleration and even compromise, has been called for in the compilation of this new edition. Many clauses have been the subject of long and continued discussion while the majority opinion has veered to-and—fro as new appreciations of the scope and purpose of the Specification have been seen or understood, and even now. at the temporary completion of the work. there are individual clauses which do not meet with the full approval of every member, although all members have been exceeding willing to examine the views of those holding different opinions and have shown considerable goodwill in conceding various points for the sake of progress and in deference to the majority view.
The numbering system has been completely revised, and it is considered quite impracticable to include a list of changes from the earlier 1940 edition, both on this account and on account of the variation in content. The Specification differs in appearance also. The Appendices are lettered rather than numbered and deal with entirely different subjects to those so treated in the earlier edition.
Appendix A now covers the classification of items and the instructions regarding weighing and shipping, all of which previously found a place in the body of the text.
Appendix B is entirely new and treats of the usage more or less prospective, of high-tensile steel bolts.
Appendix C includes a few tentative clauses on the use of cold rivets which have been used occasionally in Canadian practice and which it is felt may still be used in special circumstances.
Among the new features is a section on types of design, and this is one of those items that has not been accorded universal approval, some opinions still remaining that the matter is extraneous to such a Specification.
The clause on Impact (7.4) has been enlarged and sub—divided, but the unit stresses are substantially unchanged. the principal variation being in Clause 12.6 where the values in double-shear bearing have been substantially increased. Some slight change has been made in the permissible slenderness ratio and a few notes on depth ratios have been added. The requirements with respect to net sections in girder flanges, etc., have been brought more in line with other contemporary specifications, and in Section 19, a number 0f references to the use of fastening units, such as rivets, welds and sundry types of bolts, have been collected.
Another section upon which much time was spent and where many diverse opinions were expressed, is that which concerns intermediate stiffeners and the associated question of web crippling. Clauses 22.4 and 22.8 deal with these matters.
The reference in previous editions to the importance of engaging competent Professional Engineers must, of course, be repeated, as the new edition tends to greater complexity in spite of the determined efforts of your Committee to make it simple both to understand and to operate.
Finally, it is felt by your Committee that the admittedly long period that has been occupied in preparing this Specification ‘has been advantageous in that the whole gamut of opinion based on experience and training, both as found in our own country and as presented in the specifications from outside of Canada, has been canvassed very thoroughly, and time has been taken to make new and private studies so that the final result, while not having the qualification of permanency, which in itself is undesirable and impracticable, may yet serve to assist the engineering profession and all those associated with them in building construction, for a number of years.