tl \ 4"fc b 
 
 Buildings of Reinforced 
 
 Concrete. 
 
 1. 
 
 
 c- 
 
 <\£ 
 
 Ac 
 
 
 By Prof. Charles Derleth, Jr. ( 1 ) 
 
 Introduction. 
 
 In the Fall of 1908 a conference, which I attended, was held one 
 evening at the Faculty Club of the University of California. Two 
 groups of gentlemen were present: 1, representatives of the fire 
 surance interests of the Pacific Coast; 2, members of the technical 
 and economic departments of the University of California. 
 
 It was the purpose of the conference to discuss in general the busi¬ 
 ness problems of fire insurance and to point out if possible to what 
 extent an educational institution, particularly a technical school, might 
 aid in increasing the equipment and improving the efficiency of young 
 men,—applicants for admission to the fire insurance profession. It 
 would be out of place for me to give the argument which ensued. That 
 is not the object of my paper. Indeed, it would he impossible in a 
 sufficiently short statement to do justice to the arguments presented. 
 The views expressed by the fire insurance men brought home to me, 
 however, a situation with which I had not been clearly acquainted. 
 You will pardon, therefore, an introduction defining this situation as 
 I was led to understand it, because the principle involved bears upon 
 the subject of building construction as much as it concerns the busi¬ 
 ness of fire underwriting, and thus affords to me a pretext for present¬ 
 ing to you at this gathering a paper on engineering construction. 
 
 The Statement. 
 
 It was argued that there is a sharp distinction to be made between 
 the work of a fire insurance solicitor, on the one hand, and of the fire 
 insurance actuary, or fire insurance engineer, on the other. It may be 
 that I am misstating the views expressed, but I gathered that in the 
 main the gentlemen who are concerned with getting fire insurance 
 business, the men who daily are dealing with the commercial side of 
 that business, are men not by taste or training concerned with mathe¬ 
 matical, economical and engineering principles, though these prin- 
 
 4 
 
 F 
 
 1 Professor of Civil Engineering, University of California. 
 
 t 
 
2 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 ciples affect and influence the intelligent design of fire resistant, fire protect¬ 
 ive, and fire preventive building construction. I learned that technical 
 studies do not help the insurance apprentice whose daily routine is flavored 
 with statistical and bookkeeping accounts. 
 
 Reply to the Statement. 
 
 If this be true, it is hardly to be expected that a technical paper outlining 
 structural requirements for a special type of building will prove of absorbing 
 interest to members of an association interested primarily in the business 
 success of fire insurance. I have perused the reports of your annual meet¬ 
 ings for the four years past, 1906 to 1909, inclusive, and note that the papers 
 read are almost wholly on such subjects as “Inspections,” “Rating 
 Schedules,” “Adjustments,” “Conflagration Hazard and Co-Insurance,” 
 “Underwriting Conditions,” “Special Agents,” “Spontaneous Combus¬ 
 tion,” “On the Writing of Papers,” “The Doctrine of Waivers as Relates to 
 the Adjustments of Fire Insurance Claims,” etc. It will be noted that, 
 vital as these subjects are to the proper writing of insurance, there is little 
 of a strictly engineering nature in these papers. At the four meetings cited 
 you have had read only two papers which dealt particularly with construc¬ 
 tion; one by my colleague, Professor Charles Gilman Hyde, on the “Water 
 Supply of Cities;” the other by my friend, Mr. W. J. Miller, an architect 
 and structural engineer of San Francisco, on the subject of “Class A Con¬ 
 struction.” Both of these papers were read at the January meeting in 1907. 
 I have an idea that the subjects were prompted by our great conflagration of 
 the preceding year. At any rate in the early part of 1907 the subject of high 
 grade municipal construction was of apparent interest to everyone, and 
 people in general were eager to listen to discourses on the requirements and 
 specifications for sane structural design. Unhappily the taste for such dis¬ 
 courses appears to be satiated. 
 
 Of course, by these remarks it is not my intention to criticise the 
 absence or to deplore the omission of engineering discussions from the 
 deliberations of your annual meetings. It is obvious that the first 
 duty of an association of fire insurance companies of the Pacific Coast, 
 or of any similar body elsewhere, must be to instruct and encourage 
 its members to get business and to write papers that strengthen the 
 company at the same time that they give the individual a safe insur¬ 
 ance. Your main object, I take it, is to make the insurance business 
 grow and to set sound rates. However, notwithstanding all these facts, 
 it seems to me, as a layman in insurance, but as a student of en¬ 
 gineering, that you must acquaint yourselves more and more with the 
 requirements of construction. It is true that in the larger sense your 
 companies must be guided by the opinions of advising engineers, not 
 
BUILDINGS OF REINFORCED CONCRETE 
 
 3 
 
 by one, but by different persons representing different branches of 
 engineering. You must have your general advisers on mechanical engineer¬ 
 ing, electric work, structural design. Nevertheless, much will be gained, I 
 think, the more the insurance men themselves learn to appreciate those 
 elements necessary for the creation of the best construction of different types. 
 You should have a clear picture before you of different grades of building. 
 It is futile to recommend that all buildings be of the best types. The owner 
 of a lot, after all, must erect a building for a cost within his financial means 
 and of such size that he will get a reasonable return on his investment. 
 
 Discussion of the Statement. 
 
 I should be glad if these remarks produce a discussion. I should like to 
 know from insurance men more definitely to what extent a general acquaint¬ 
 ance with engineering would be of assistance to them in their work. It may 
 be that my opinions are imperfect and that it would be a detriment to the 
 average insurance man to divert a part of his energies to semi-technical 
 questions. I am perfectly aware that this is an age of specialization, but he 
 is a poor specialist who cannot appreciate the needs of those professions which 
 are closely allied to his own work. 
 
 You will pardon my long introduction. I offer it partly, as I have said, in 
 an attempt to solicit discussion; but mainly to justify my presentation of a 
 general descriptive picture portraying the present stage of development of 
 reinforced concrete design for city buildings. In what follows I shall give 
 you an elementary account, shorn wherever possible of mathematical and 
 mechanical terms. I offer nothing new or original; my facts are taken, 
 often without special acknowledgment, from standard text books, essays and 
 specifications. For more elaborate accounts the reader is referred to the foot 
 notes and to the bibliography appended to my article. 
 
 Classification of Building Types. 
 
 Different city ordinances have attempted to classify buildings ac¬ 
 
 cording to grades of construction. No uniform system has been 
 adopted in this country. In the San Francisco ordinance the scheme 
 used is to be deplored, since to the mind of the layman it seems to 
 indicate degrees of superiority. For instance, men speak of class A 
 and class B buildings with the general notion that whatever is class 
 B is distinctly inferor to class A. The San Francisco ordinance 
 
 places frame dwellings the lowest in the list, yet I can conceive of a 
 
 well-built wooden building, properly located with respect to prescribed 
 
4 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 fire limits, superior to an imperfect structure in which either a steel 
 frame is to be found, or part of which is reinforced concrete. We 
 should recognize in the beginning that all types of construction for 
 financial reasons must be encouraged. It should be our object only to 
 see to it that different types are applied in the most intelligent man¬ 
 ner. At your 1907 meeting, Mr. W. J. Milled referred to this subject 
 when he argued that a radical departure be made in the designation 
 of different types of buildings. He says that structures should not 
 be grouped primarily in classes, but according to type. 
 
 To emphasize the character of reinforced concrete building I sub¬ 
 mit the following grouping for different grades of construction: 
 
 Type I. Buildings with a cage-like steel frame supporting all floor 
 and wall loads; the combined dead and live load weights carried 
 directly to the foundation by the steel frame; all structural parts of 
 the building built of incombustible materials; all projecting parts 
 structurally anchored to the steel frame. In this type reinforced con¬ 
 crete may be used for floor slabs, partitions, curtain walls and foun¬ 
 dation footings. No beams or girders taking computed loads either in 
 the floors or walls should be of reinforced concrete; they should be 
 of structural steel. In heavy footings the reinforcement should consist 
 of rolled I-beam grillages instead of rods; for light footings rod re¬ 
 inforcement should be approved. 
 
 Type II. Buildings with reinforced concrete cage construction; all 
 floor and wall loads, dead and live, carried directly to the foundation 
 by the structural frame; all parts of incombustible materials; I refer 
 to floor slabs, curtain walls, partitions, etc.; all projecting parts to be 
 anchored to the frame. In this structure the frame, that is, beams, 
 girders, spandrel wall girders and columns are of reinforced concrete; 
 but in larger buildings heavy members may be of structural or rolled 
 steel encased in concrete. Floor slabs, curtain walls, partitions and 
 footings are of reinforced concrete. Normally every part is of rein¬ 
 forced concrete. 
 
 Type III. Buildings with self-supporting masonry walls; walls car¬ 
 rying adjacent floor panels; structural steel or reinforced concrete col¬ 
 umns in the interior; floor framing of structural steel or reinforced 
 concrete; all important parts, such as walls, floor slabs, partitions, of 
 incombustible materials. This description is intended to include most 
 of the schemes of building grouped under class B in the 1906 San 
 Francisco ordinance. That ordinance included all reinforced concrete 
 
 2Cf. “Class ‘A’ Construction from the Standpoint of the Architect and 
 Architectural Engineer”; by W. J. Miller; 31st Annual Meeting of the Fire 
 Underwriters’ Association of the Pacific Coast; January 1907; page 111. 
 
BUILDINGS OF REINFORCED CONCRETE 
 
 5 
 
 construction under class B. My classification puts reinforced con¬ 
 crete cage construction into a class by itself (see type No. II). It is 
 an injustice to group reinforced concrete cage frames with buildings 
 having self-supporting walls. 
 
 Type IV. Buildings with masonry walls supporting the adjacent 
 floors; interior of floors supported by studded partitions or by wooden 
 or steel girders; combustible materials may be used in all parts ex¬ 
 cept for walls. Cast iron columns may be used in this type. Walls, 
 columns, important floor girders, footings, may be of reinforced con¬ 
 crete. 
 
 Type V. Mill construction. Buildings of heavy timber frames and 
 floors with exterior walls and roof of corrugated iron fastened to tim¬ 
 ber framing and without boarding. 
 
 Type VI. Frame buildings. These buildings may be built entirely of 
 combustible materials, except roofs for buildings within certain 
 described fire limits, as specified by the city ordinance. 
 
 Wide Possibilities for Reinforced Concrete. 
 
 The range of application for reinforced concrete is very wide. It 
 may be used for details in all six building types; for footings in types 
 V and VI; structurally in the first four types for important members 
 taking computed stresses. It may be wholly employed in type II. It 
 finds its most important adaptation in types I and II. It is for these 
 two schemes of building, representing the classes requiring the most 
 developed engineering skill and knowledge, that the greatest care 
 must be taken in designing reinforced concrete parts. My later re¬ 
 marks apply mainly to the art and science of reinforced concrete build¬ 
 ing for the first two groups. 
 
 Economy and Adaptability of Reinforced Concrete. 
 
 In their text on Reinforced Concrete, theory and design, Messrs. 
 Buel and Hills give a clear exposition of the economic and practical 
 difficulties: “In directing building work in concrete-steel the engineer 
 has a long list of traditions to overcome. Foremen and masons whose 
 training has been wholly in the use of concrete as a filler over brick 
 arches or trough sections of steel do not readily perceive that a rein¬ 
 forced concrete floor slab is a radically different structure and must 
 be fabricated according to entirely different standards of workman¬ 
 ship. To meet this difficulty the engineer has to arm himself with a 
 rigidly-drawn specification and careful supervision and inspection. 
 
 3Cf. Reinforced Concrete; by Buel & Hill, second edition, p. 387; pub. 
 by Eng. News, 1906. 
 
6 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 The requirements for materials and workmanship in concrete-steel con¬ 
 struction and the imperative necessity of enforcing them have been 
 discussed in a preceding chapter. Negligence in these matters is fre¬ 
 quently punished by disaster in concrete steel building work.” 
 
 These remarks apply particularly to San Francisco and some other 
 parts of the Pacific Coast. In California the objection of labor to the 
 new material and methods has been peculiarly pronounced. Lack of 
 respect for new requirements has produced failures, but happily not 
 restricted to our Western community A An impartial study of these 
 failures will convince the reader that the disastrous results were not 
 due to a fault inherent in reinforced concrete design, but entirely to 
 an improper or unintelligent use of the combined materials. It would 
 be easy to review cases of collapse for buildings with structural steel 
 frames, but no one would think of using such citations as arguments 
 to impute dangerous qualities to steel frame construction."’ 
 
 Pertinent remarks for San Francisco conditions are made by Mr. 
 Lewis A. Hicks, a local engineer and contractor. He may be consid¬ 
 ered intimately acquainted with California building problems; his 
 words are quoted with emphasis. 6 “Before the earthquake, the efforts 
 of those interested in introducing this comparatively new material (re¬ 
 inforced concrete) had been abortive owing to the active resistance 
 of persons interested in the manufacture of clay products, the oppo¬ 
 sition of the bricklayers’ unions, and the general inertia of the build¬ 
 ing trades to accept changes in long established methods of construc¬ 
 tion. When the pressure of this conservatism was removed by the 
 conditions following the fire, there was a prompt reaction in the pub¬ 
 lic mind in favor of the indiscriminate use of a material that would 
 furnish greater security against damage by earthquake and fire than 
 the brick construction formerly prevailing, and without entailing the 
 excessive cost of a steel frame. For a time it seemed as if every build¬ 
 ing put up was to be made of concrete, but a sufficient interval has 
 now elapsed to make it possible to outline broadly the place in build¬ 
 ing work that it is well adapted to take, as well as such economic lim¬ 
 itations as insure the use of other materials for certain purposes.” 
 
 4For instructive examples of collapsed buildings I may cite: 
 
 1. The Bixby Hotel Disaster, Long Beach, California; cf. Official Report 
 of Cement Workers’ Union; the Architect and Engineer of California for 
 Dec., 1906, vol. VII, Nos. 1 and 2; and Eng. News, Vol. 56, p. 555. Nov. 29, 
 1906. 
 
 2. Failure of Reinforced Concrete Buildings at Philadelphia; cf. Eng. 
 News, Vol. 58, p. 69, July 18, 1907. 
 
 3. Report on Failure of Reinforced Concrete Building of Eastman Kodak 
 Co., Kodak Park, New York; cf. Eng. News, Vol. 57, p. 130, Jan. 31, 1907. 
 
 5Cf. The Collapse of a Building Under Construction; by H. de B. Par¬ 
 sons, Trans. Am. Soc. C. E., Vol. 53, p. 1, Dec., 1904. 
 
 6Cf. An article entitled, “Reinforced Concrete Construction”; by Lewis 
 A. Hicks, Mining and Scientific Press, p. 503, April 20, 1907. 
 
BUILDINGS OP REINFORCED CONCRETE 
 
 7 
 
 Mr. Hicks gives a concise statement of his views for building con¬ 
 ditions in the business, warehouse and banking districts surrounding 
 lower Market Street. He speaks of the necessary struggle to main¬ 
 tain down-town property values and points out that the character of 
 improvement must be determined largely by the ability of the owners 
 to pay for them. On the one hand, with high lot values and little 
 available funds, the owner selects a low building of brick walls with 
 interior wood construction (see type IV). On the other, with valuable 
 real estate and plenty of money, he selects a steel frame building, 
 type I. To quote Mr. Hicks again: “Between these two extremes 
 there are a large number of people owning valuable street frontage 
 with deep lots who must soon find some commercial use for their 
 property and who desire fairly permanent improvements of moderate 
 height but of class A character.” He has in mind the structure which 
 I describe as type II, or possibly also type III, in concrete. “It is 
 among such (people) that reinforced concrete will find its most ex¬ 
 tended use.” Further he says: 
 
 “These requisite conditions are most successfully fulfilled by a 
 building with reinforced concrete frame, floors, roofs, and curtain walls, 
 with its front veneered with stone, brick, or terra cotta bonded into 
 concrete backing, and all its structural members fireproofed with a 
 secondary skin of metal furring and plaster, furnishing protected air¬ 
 spaces. Such a building is class A in every detail of construction and 
 in appearance, and in its virtual power to resist fire and earthquake 
 it is, in my opinion, within the limit of height considered, equally as 
 reliable as a steel frame structure. 
 
 The amount of concrete used in fireproofing the columns, beams, 
 floor and roof of a modern steel building is practically sufficient to 
 build the same members in reinforced concrete, and the difference in 
 cost of the two structures will be roughly the difference in the weight 
 of steel used. The elimination of two-thirds to three-quarters of the 
 steel required for a steel frame is entirely practicable, but the saving 
 is not as significant as would appear at first glance. The cost of a 
 finished class A structure will range from four to six times the cost 
 of the steel frame, and the saving effected will therefore amount to 
 from 10 to 15 per cent of the cost of the improvements. 
 
 “Where the relation between the value of the ground and the cost 
 of the building is normal, or as one to one, there follows that the 
 saving on the entire investment amounts to from 5 to 7 per cent. It 
 will frequently happen that an owner will prefer to pay this addi¬ 
 tional cost for the sake of having a type of construction that has been 
 tested to a finality. It is also true that in incompetent hands this 
 
8 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 apparent saving of 5 per cent may easily shrink to disappearance and 
 that time, apparently in favor of the concrete type, may be wasted 
 to such an extent that the steel frame will gain rather than lose by 
 such a comparison.” 
 
 Hardly had the San Francisco fire ruins cooled when reinforced con¬ 
 crete experts, self-styled, arose as if from the ashes in every quarter 
 of the city. Results show that at least a number of these gentlemen 
 were grossly incompetent or careless. Their labors have been very 
 harmful to the cause of reinforced concrete construction in California. 
 In the two years following the conflagration a noticeable setback was 
 given to the selection of this type of building; happily at present there 
 are signs of a recovery of confidence. The incompetent or grossly 
 done work immediately after our disaster may be divided into two 
 classes: 1, work structurally safe but of unreasonably high cost; 2, 
 work faulty in design or introducing unique or quack systems. 
 
 All structural members of reinforced concrete which take computed 
 stress, or which form essential parts of a building frame, in rational 
 design must be protected by fireproofing envelopes, just as much and 
 to nearly the same extent as structural rolled steel members doing 
 similar duty. Such envelopes must not take computed stresses; they 
 must protect the main members from corrosion or fire, even though 
 they themselves are destroyed by heat or the action of the elements. 
 Proper design whereby sufficient protection is insured by envelopes 
 to main reinforced concrete members would prohibit, in some instances 
 at least, the use of reinforced concrete versus rolled steel. This pro¬ 
 hibition would be due to cost or to largeness of cross section, or both. 
 A case in point would be a main column in the lower stories of a high 
 building constructed wholly of reinforced concrete; such columns ade¬ 
 quately protected would often be of unsightly and excessive diameters 
 and would cost more than equivalent built-steel columns. 
 
 In order to make the cost of reinforced concrete buildings appear 
 favorable to the owner in comparison to steel frame, class A construc¬ 
 tion, local designers and contractors (especially the contracting en¬ 
 gineers for patented systems) have been tempted to propose designs of 
 excessive cheapness. Their results have been secured by: 1, cutting 
 down the thickness of floor slabs and curtain walls and reducing the 
 amounts of concrete wherever possible; 2, by omitting reinforcement 
 steel where theoretically desirable on the ground that without such 
 steel the building would stand up; for example, metal for reverse 
 bending in columns and over supports of continuous girders, anchorage 
 steel desired for stiffness and continuity of joints; 3, the simplification 
 of forms by omitting knee braces between main girders and columns; 
 
BUILDINGS OF REINFORCED CONCRETE 
 
 9 
 
 by omitting cross girders between columns (as in the Bixby hotel), 
 or spandrel wall beams; and, 4, by neglecting requirements for fire¬ 
 proofing that would be insisted upon by the same designers in the 
 case of alternative steel frame buildings, arguing that the reinforced 
 concrete type of construction needs no special fireproofing envelope. 
 Were some of these desirable conditions reasonably satisfied, the dif¬ 
 ference in cost between steel frame and reinforced concrete designs 
 would and could not be marked, even where the designers and con¬ 
 tractors are experts. 
 
 Immediately after the fire many professional men flocked to San 
 Francisco. Some with little experience proclaimed themselves struc¬ 
 tural engineers. They were unfamiliar with reinforced concrete de¬ 
 sign and construction; but worse, they were not acquainted with local 
 costs and markets for material, nor did they appreciate our peculiar 
 labor conditions. It is not surprising, therefore, that a large number 
 of reinforced concrete buildings were constructed which cost more 
 than the first estimates. Indeed, some notable structures, recently 
 completed, have cost almost double the originally stated figures. One 
 can hardly understand how otherwise intelligent owners could allow 
 themselves to be misled or duped to this extent. 
 
 For example, in one instance, an Eastern architect who combined 
 his designing office with a contracting staff, arranged to design and 
 construct complete a hotel in reinforced concrete, the lump sum to 
 be about $450,000. It was agreed that the work should be done upon 
 a percentage basis, the plausible argument being that the owner was 
 to pay only the actual expenditures for labor and materials, plus a 
 percentage for the architect, to defray the expenses of his office and 
 field establishments. A surprisingly large number of contracts were 
 let in this way, with no visible protection for the owner. The hotel 
 building just cited was completed after great delays. I am informed 
 that more than $750,000 was expended. Beside, who is to pay the 
 owner for loss of rents incident to the prolonged construction? 
 
 In another case a building for office purposes planned with steel 
 frame (type I) was studied by a competent engineer and upon his 
 design a reliable contractor offered to erect the building complete for 
 a lump sum payment of about $120,000. A reinforced concrete expert 
 who combined according to his prospectuses the talents of architect 
 and contractor offered to build the structure in reinforced concrete 
 (type II) .for about $94,000 on a percentage basis, as in the hotel case 
 just mentioned. By what seems almost hypnotic influence, the owner 
 agreed to the second proposition with no real security or assurance 
 that the work could be done at the $94,000 figure. Results have shown 
 
10 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 that the confidence was misplaced. The building in question, when 
 completed, cost nearly $150,000. 
 
 I might describe a number of other instances where buildings struc¬ 
 turally sound have cost too much money. San Francisco owners have 
 been disgusted by these cases and many of them are loth to try the 
 experiment. Fortunately, a goodly number of first-class, modern type 
 reinforced concrete buildings have been brought to successful com¬ 
 pletion at moderate prices, and it is to be expected that the attitude 
 of doubt or fear in the minds of prospective builders will be dissipated. 
 
 A number of reinforced concrete buildings have been completed in 
 the city with unusual designs. The illustrations (see figures 1 and 2) 
 exhibit fantastic reinforcement. Figure 1 shows the floor and spandrel 
 wall reinforcement made of straps meshed to form equilateral triangles. 
 Old wire cables were introduced to reinforce the light latticed floor 
 girders. The columns consist of a mixture of light rods and bars held 
 together by latticed bands. The designer claims for this building a 
 great advantage, that the reinforcement metal was erected complete 
 for the entire structure before depositing concrete. Indeed, the major 
 part of the steel work was put in place before the concrete forms were 
 built. I do not know the cost of this building, but it certainly repre¬ 
 sents an eccentric type. 
 
 Figures 3 and 4 deserve critical mention; they are views typical of 
 a class of structures which cost large amounts of money. One of the 
 great sources of expense is the unnecessarily large amount of steel 
 reinforcement for columns and heavy girders. It is to be presumed 
 that the designers were anxious to be on the safe side. Figures 3 and 4 
 give progressive views during the placing of first-floor steel. Note the 
 unusual amount of metal in the columns. The slab, girder, and column 
 metal meeting at column bases is so thick that there is little room left 
 for concrete. A column contains about sixteen rods, each about two 
 inches in diameter. The columns pictured carry only five stories. 
 
 Mr. Wm. H. Hall? gives a striking description of column design in 
 eighteen different buildings erected in 1907. From his table of figures, 
 his critical comparisons and his sketches, one may note at a glance the 
 great diversity in method, the utter lack of consistency, the wide va¬ 
 riation in the proportions of steel to concrete designed to effect sub¬ 
 stantially like duties. He says: “Viewed broadly, the designing of 
 columns in the reinforced concrete constructions of San Francisco seems 
 to show, in some cases, either ignorance of what is safe, or a determi¬ 
 nation to save money at the expense of structural safety; in other 
 
 7Cf. Reinforced Concrete Practice in San Francisco—Column Design; 
 by W. H. Hall; The Architect and Engineer of California, May, 1907. 
 
BUILDINGS OF REINFORCED CONCRETE 
 
 11 
 
 cases, ignorance of, or a lack of confidence in, what is just right in 
 design, and determination to be on the safe side in the matter of re¬ 
 inforcement strength, at the sacrifice of economy; in still other cases, 
 a weak concession to the desire to keep down sizes of interior columns, 
 and as a consequence, the reduction of concrete and increase of steel 
 to take place in compression, until the danger point, at the other 
 extreme of conditions, has been approached.” 
 
 Typical of high-class reinforced concrete work for warehouse con¬ 
 struction is a group of buildings built immediately after the fire for 
 the A. Schilling Company, wholesale merchants for tea, coffee, spices 
 and similar products. The Tea Building has self-supporting walls of 
 brick, with the interior columns and floors of reinforced concrete. The 
 structure is subdivided into three compartments per floor by two 
 brick cross or fire walls. The doorways leading through the fire wall 
 are protected by double fire doors,, asbestos lined and tin clad. All 
 windows are provided with metal sash and frame, with wire-glass 
 panes. One of the few buildings in the Mission district before the 
 fire which could compare with the above description was the California 
 Electrical Works at Second and Folsom Streets. The interior of the 
 latter building, however, was of timber, heavy mill construction, and 
 therefore inflammable. Buildings like the Schilling Building are now 
 common in the city. Indeed, a large number of the later ones built 
 are true reinforced concrete structures in that their walls are not 
 self-supporting but are carried upon a frame-work. Some of the re¬ 
 cent reinforced concrete warehouses have gone up in record time; an 
 excellent example is the warehouse building for the Tillman Bendel 
 Company, designed according to the Kahn System. 
 
 Exorbitant amounts of metal in the lower story columns of reinforced 
 concrete buildings is a common fault in a number of the first buildings 
 erected in San Francisco. The buildings to be so criticised are from 
 five to eight stories in height. The designers were anxious to get suffi¬ 
 cient strength. It is a fact that in at least one of these structures 
 there was relatively a dearth of continuity steel to take reverse bend¬ 
 ing moment in the upper sides of beams and girders. To reduce the 
 cost of forms many designers omitted knee brace connections between 
 columns and floor beams. One can not deny that buildings with these 
 deficiencies may never show signs of weakness; but such practice is 
 to be deplored in a community which has been subjected recently to a 
 severe earthquake shock. To save 3 per cent in the total structural 
 cost of a building vitally important structural features are omitted. 
 It would be better to save the 3 per cent by omitting unnecessary 
 architectural decorations. I might add maliciously that this could 
 
12 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 have been done with great effect in one building, which has been 
 loudly decorated in glaring tile of all colors of the rainbow. 
 
 For the California Market a one-story structure or shed was re¬ 
 cently built of reinforced concrete, and is worthy of comment. The 
 building consists of a series of reinforced columns supporting roof 
 trusses of the same materials. The framing is similar to that of a 
 typical steel mill building. The result is a number of sheds paralleling 
 each other. The designer is a man versed in reinforced concrete, 
 whose schooling and experience were obtained in continental Europe. 
 Small framed roof trusses of reinforced concrete are at present not 
 uncommon in France or Germany; but with our California conditions, 
 especially the high price of labor, I think it would have been more ap¬ 
 propriate to use light steel trusses. Reinforced concrete can not be 
 used to fit every situation. I believe this is a case where it would 
 have been better not to have used the material. 
 
 Again, designs in reinforced concrete prepared by an engineer not 
 thoroughly conversant with economic construction are very apt to 
 combine features distinctive of a number of the so-called patented 
 systems with an unnecessary complication of parts. It is not surprising 
 to the writer to find that buildings constructed in this patch-quilt man¬ 
 ner have cost from 30 per cent to 50 per cent more than equivalent 
 designs prepared according to first principles. A case of a hotel 
 recently came to the writer’s attention where the high estimated cost 
 was due mainly to uneconomic proportions for floor panels contem¬ 
 plating 20-foot square slabs, with an unintelligent placing of reinforce¬ 
 ment metal, proposing reinforcement in two directions. The original 
 designs were discarded. The revised plans changed the floor propor¬ 
 tions, substituted a ribbed floor with thin slabs reinforced in one 
 direction only and reduced the contractor’s bid in the ratio of 3 to 2. 
 
 Conclusions—Regarding Economy and Adaptability. 
 
 Concrete buildings of the most developed type, No. II, in my table 
 must be considered as worthy of classification with first-class steel¬ 
 framed structures. They require the same degree of structural talent 
 in the preparation of specifications and plans and in the field inspec¬ 
 tion and methods of erection. A building consisting wholly in struc¬ 
 tural parts of reinforced concrete, however, should not be built for 
 great heights. The San Francisco ordinance wisely limited the heights 
 of such structures to eight stories. I should prefer to limit them to 
 six stories, because I believe above that height the steel frame build¬ 
 ing is the more logical. For buildings over six stories the columns in 
 the lower floors would become excessively heavy when designed in 
 
BUILDINGS OF REINFORCED CONCRETE 
 
 13 
 
 reinforced concrete. Buildings have been built in San Francisco and 
 Los Angeles where reinforced concrete first-story columns actually 
 cost more than equivalent members of structural steel encased in fire¬ 
 proofing of concrete; because the architect, and in one instance the 
 owner also, approved of the extra cost merely to he able to say 
 that there was no structural steel in the building. Advocates of 
 reinforced concrete, in their zeal to exploit or defend its methods, have 
 argued, unwisely I think, that buildings of greater height than eight 
 stories should be erected in reinforced concrete. That higher struc¬ 
 tures can be built I readily admit. The McGraw Building, eleven 
 stories, in New York City; the Gloekler Building, ten stories, in Pitts¬ 
 burg; the Ingalls Building, fifteen stories, in Cincinnati, are examples. 8 
 
 Discussing his design of the McGraw Building, Mr. Burr, referring 
 to comments from other engineers, says: “Instances of bad design, 
 worse fabrication and marked unfamiliarity with concrete work have 
 been exhibited to illustrate the difficulties attending the construction 
 of reinforced concrete work and its alleged uncertain character. It is 
 probably fully understood among experienced and well-informed en¬ 
 gineers, as has been often stated, that the degree of ability necessary 
 in the design of a reinforced concrete structure, the thoroughness of 
 inspection, and the care in fabrication, are neither less nor more than 
 required in the best quality of structural steel work. In fact, in these 
 respects, it may be reasonably maintained that both classes of con¬ 
 struction are in the same category. To cite badly-designed and badly- 
 handled concrete work as an argument against first-class reinforced 
 concrete construction is precisely like citing unscrupulously-designed 
 and badly-built back-country highway bridges of poor steel as a legiti¬ 
 mate argument against first-class structural steel work. The proper 
 question is, What can be done with competent design and first-class 
 materials and work? not, What defects can be developed by bad 
 material and inefficiency of handling? 
 
 From what precedes I assume that it is amply shown that in type 
 II, reinforced concrete has its full development, and that it has come 
 to stay as a permanent form of construction, despite the fact that it 
 has still to overcome many defects of construction and many preju¬ 
 dices. 
 
 8The Reinforced Concrete Work of the McGraw Building; by W. H. 
 Burr; Trans. Am. Soc. C. E., Vol. 60, p. 443, June, 1908. 
 
 The Ingalls Building; by Messrs. Elzner and Anderson; The Architec¬ 
 tural Record, June, 1904. See also The Eng. Record, Vol. 47, p. 540, May 
 23, 1903. 
 
 A Ten Story Reinforced Concrete Building for the Bernard Gloekler Co.; 
 Eng. News, Vol. 58, p. 488. Nov. 7, 1907. 
 
14 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 It is further to be noted that in types I, III and IV of my list, 
 important parts may be of reinforced concrete; such parts as columns, 
 curtain walls, floor slabs, footings, according to the particular type of 
 building under construction. In the design and erection of these 
 parts the same degree of engineering skill and ability must be 
 employed as in case of type II. 
 
 Consequently in what follows I offer a number of important condi¬ 
 tions which should influence the proportions of frames and the details 
 of parts. I outline, in fact, salient features or specifications for rein¬ 
 forced concrete design and construction without undue emphasis on 
 technical phraseology.s 
 
 Specifications. 
 
 The various elements of building construction relating to reinforced 
 concrete design may be grouped under the following heads: 1, floor 
 and slab roofs; 2, beams and girders for roofs or floors; 3, spandrel 
 wall girders; 4, columns; 5, foundation footings; 6, spandrel or curtain 
 walls; 7, partitions and other interior construction. The reinforced 
 arch, culvert, truss and other complex forms do not naturally appear 
 in connection with building construction, and therefore need not be 
 considered. Retaining walls of counterfort types are commonly 
 designed in connection with buildings. 
 
 Slabs, Beams and Girders for Floors and Roofs. 
 
 Reinforced floor or roof slabs in buildings of type I are supported 
 on structural steel beams and girders. Desirable slab spans range 
 from 6 ft. to 8 ft. Such slabs also occur in type III. In type II floor 
 slabs are supported on reinforced concrete beams and girders instead 
 of on structural steel. For this case I should limit spans from 6 to 8 
 ft. also; that is to say, I recommend in all types what may be termed 
 a ribbed roof or floor. The beams and girders in types I, II, III, for 
 economy and architectural conditions, will usually range in span from 
 12 to 20 ft., rarely 25 ft. as a maximum. I should prefer in general to 
 see the limit of panels 20 ft. square; that is, columns spaced not to 
 exceed 20 ft. In some types of floor design, notably the mushroom 
 system devised by C. A. P. Turner,io the slabs are not ribbed, but 
 are of constant thickness for the complete panel marked by column 
 centers. Other things being equal, I consider this type of floor less 
 stiff than a ribbed floor. 
 
 9For a comprehensive list of reinforced concrete buildings in course of 
 construction in San Francisco, 1907, consult: “The Rebuilding of San 
 Francisco—Reinforced Concrete Buildings”; by W. H. Hall; The Archi¬ 
 tect and Engineer of California, Vol. 9, p. 61, July, 1907. 
 
 ioCf. Principles of Reinforced Concrete Construction; by F. E. Turneaure 
 and E. R. Maurer; 2nd ed., 1909; p. 328. 
 
BUILDINGS OP REINFORCED CONCRETE 
 
 15 
 
 In designing floor slabs of medium or short spans, say, less than 8 
 ft., the formula for bending moment should be for uniform loads, 
 
 Tvr=^- For longer spans the interior slabs of a floor plan should 
 1 x 12 
 
 be designed by the same formula, but outer or edge slabs, which are 
 naturally less rigidly held at the wall ends, should be designed for a 
 
 pi 2 
 
 bending moment, M In these formulae p — the uniform load 
 
 in lbs. per sq. ft, 1 — the span length in ft.; M the bending moment 
 in ft. lbs. In all cases the width of slab under design is 12 in. For 
 conservative design, disregarding lengths of spans, it is customary, for 
 
 simplicity and uniformity, to use in all cases the formula. M = 
 
 though this procedure will give slightly greater strength than neces¬ 
 sary and greater cost for the floors. 
 
 I do not advocate calculations for slabs assumed supported on all 
 four sides, and doubly reinforced; that is, reinforced with two groups 
 •of bars at right angles. For large slabs without beam ribs, double 
 reinforcement is necessary; also in special systems, for example, the 
 mushroom system of Turner, which requires a radical arrangement of 
 bars. In no case should double reinforcement be used for rectangular 
 slabs; such a design is not economic. Where slabs are reinforced in 
 two directions they should be square. The reinforcement should be 
 of equal amount in the two directions. It should be calculated on the 
 assumption that half the load is carried by each system of reinforce¬ 
 ment. The concrete is proportioned for only one system or one-half 
 the load, as the compressive stresses in the concrete, due to the two 
 systems, are at right angles to each other, and it may be assumed 
 that the stresses in one direction do not weaken the concrete with 
 respect to the stresses in the other direction. Square slabs are usually 
 designed for uniformly distributed loads, resulting in an equal spacing 
 of rods throughout the slab. More exact analysis for the stresses 
 would lead to the conclusion that rods should be spaced closer in the 
 central part of the panel than at the edges. The reinforcement in one 
 
 direction should be calculated for a bending moment, M = kL: 
 
 20 
 
 where p is the total load per sq. ft. on the slab. 
 
 In floor slabs, to prevent cracks running parallel to the main rein¬ 
 forcement, only one system of bars being used, some longitudinal 
 reinforcement should be provided. For close beam spacing, say 6 ft., 
 longitudinal bars are hardly needed. For wider beam spacing their 
 need is more important. The amount of longitudinal steel is a matter 
 of judgment and experience. The use of in. to % in. bars spaced 
 
16 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 about 24 in. is common practice, the heavier bars for heavier floors. 
 Of course, longitudinal reinforcement is unnecessary in square slabs 
 reinforced in two directions. 
 
 Floor slabs should not be less than 3 y 2 in. in total thickness. For 
 ribbed floors, with slab spans about 6 ft., the thickness will usually 
 range from 4 to 5 inches, depending upon the live loads specified. The 
 thinner the floor slabs the more care must be taken in placing the 
 reinforcement steel, particularly the steel over supports for reverse 
 bending moment. In thin slabs lack of precaution in placing steel is 
 a fruitful cause for ultimate sagging of the floor. Not only must the 
 steel be accurately placed, but it must be kept in its intended position 
 during the pouring and setting of the concrete. In slabs reinforcing 
 steel never should be nearer than y 2 in. to the concrete surface. 
 
 Recently I had occasion to examine carefully the structural parts 
 of a large reinforced concrete warehouse and factory located in San 
 Francisco. The floor slabs are approximately 18 ft. square, supported 
 on four sides, and reinforced in two directions. They are 7 in. thick. 
 The steel in the center of the slab is within y 2 in. of the bottom sur¬ 
 face of the concrete. But at the supports, though bent upward for 
 reverse bending moment on all four sides, the bars do not reach within 
 2 y 2 in. of the top surface. This is partly to be explained by the fact 
 that the top dressing of mortar is about 2 in. thick. In almost all 
 cases these slabs have sagged and show considerable cracking. I 
 offer this example to show how easily reinforced concrete designs may 
 get into bad repute. The sags and cracks in these floors are a source 
 of inconvenience to the owners of the building. Had the steel been 
 placed more effectively so that at the supporting edges it came within 
 % in. instead of 2 y 2 in. of the top surface, the slabs would have been 
 much stiffer. As it is, the 7 in. slabs are really no stronger or stiffer 
 than 5 in. slabs, and carry an extra weight of top dressing. There is 
 no reason why the top dressing should be more than % in. to 1 in. 
 in thickness. Further, had these slabs been built of the ribbed type 
 with 4 in. floor slabs supported on reinforced concrete beams, by fram¬ 
 ing auxiliary beams into the square panels, a much greater stiffness 
 could have been obtained with practically no change in the amount 
 of materials and with little, if any, extra cost. 
 
 In slabs, beams and girders the compressive stress in the concrete 
 should not exceed 500 lbs. per sq. in. For main reinforcement steel 
 I should recommend deformed bars of a medium grade of steel with 
 an elastic limit about 40,000 lbs. per sq. in.; percentage of final 
 stretch not less than 22 per cent. I should always recommend that 
 steel for reinforcement pass a bending test; that is, that it be required 
 
BUILDINGS OF REINFORCED CONCRETE 
 
 17 
 
 to bend cold 180 deg. over a bar of its own diameter without showing 
 injury on the outside of the bend. It is a mistake to specify high 
 carbon steel or steel manipulated in the shops to give higher ultimate 
 resistance and elastic limit. Higher values are secured at the expense 
 of ductility and toughness. Where steel must bend to forms, par¬ 
 ticularly for anchorage purposes, where it must bend to angles of 90 
 deg. or less, a high-strength steel is more apt to be injured than a 
 medium or soft variety. In columns the steel can not be stressed more 
 than about fifteen times the allowable stress in the concrete; there¬ 
 fore not more than about 15x600—9000 lbs. per sq. in. Clearly, for 
 columns, there is nothing to be gained by specifying a steel with elas¬ 
 tic limit exceeding 40,000 lbs. per sq. in. In slabs, beams and girders 
 the futility of higher strength steel can not be so clearly stated. Most 
 ordinances specify that the steel in beams and slabs shall be stressed 
 to 16,000 lbs. per sq. in., or to about that value. One ordinance uses 
 the phrase, “to one-third the elastic limit.”n This is a careless speci¬ 
 fication, since it encourages the use of high elastic limit steel.12 in 
 conservative specifications which limit the working stress to 16,000 
 lbs per sq. in. there is nothing to be gained by using a steel stronger 
 than medium grade. It is curious to observe that in a number of 
 recent constructions in San Francisco architects have insisted, with¬ 
 out good judgment, upon specifying high elastic limit and have re¬ 
 jected metal which did not give it. The metal was promptly removed 
 by the contractor to his shops, cold twisted, a process which has long 
 been known to increase the ultimate resistance and elastic limit, and 
 as promptly returned to the building and accepted by the architect. 
 This manipulation at the same time decreases the percentage of final 
 stretch and contraction and injures the toughness in bending. The 
 metal has lost desirable qualities of ductility for undesirable, not 
 needed, greater strength. 
 
 In most building ordinances it is prescribed that reinforced con¬ 
 crete girders be designed as though they were simply supported. The¬ 
 oretically, then, no steel would be required over the supports in the 
 concrete at the upper side of the beam. Practically, reinforced con¬ 
 crete construction must be considered continuous over the supports, 
 and if reverse bending moment steel is not provided, cracks will 
 occur. The conservative rule for reverse bending moment steel is to 
 prescribe an equal amount of metal over the supports to that required 
 
 nCf. The Building Law of the City and County of San Francisco, 1906, 
 section 168. 
 
 i2This tecnical point was one of the real questions at issue, but overlooked 
 by non-technical judges, in the hearing, May, 1909, before the Mayor of 
 San Francisco, re the County Infirmary Building. 
 
18 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 at the center of a span for bending moments defined in an earlier 
 paragraph. 
 
 For heavy beams and girders web reinforcement must be consid¬ 
 ered. In thin floor slabs, spans not exceeding 6 ft., stirrups are un¬ 
 necessary. It is sufficient to bend a portion of the bars upward near 
 the quarter points. For beams and girders a number of the main 
 reinforcement rods should be bent up at successive points near the 
 quarter of the span so as to provide diagonal bars through the web 
 at intervals near the abutment. Beside this, diagonal reinforcement 
 stirrups, usually in vertical planes, should be introduced.^ 
 
 It is common observation to note in San Francisco today the use 
 of reinforced concrete in buildings of types III and IV where the 
 designers have used working stresses in steel and concrete, so high that 
 they are seriously prohibitive from a conservative, safe, point of view. 
 Recently I had occasion to check the structural design for a building 
 already erected for automobile interests, in which stresses in con¬ 
 crete and steel may easily be double the values prescribed by the 
 San Francisco ordinance. These bold departures from usual practice 
 are, of course, due to the desire to decrease the cost of the structure. 
 I have heard engineering contractors boast that they were able to 
 build on Market Street a store and garage building in reinforced con¬ 
 crete . cheaper than a first-class mill constructed building of timber. 
 The reason for this is that in the reinforced concrete structure as 
 built, the designers unwisely provided excessively long spans and 
 improperly allowed calculations based on the use of abnormally high 
 and unsafe working stresses. It would be interesting to inquire why 
 we have a building ordinance when nobody necessarily follows its 
 prescriptions. 
 
 Design of Columns. 
 
 Six years ago our ideas on the design of reinforced concrete col¬ 
 umns were imperfect, not to say hazy. Considere has just published 
 his investigations for the strength and elasticity of hooped columns. 
 it was confidently expected then that hooped columns could be loaded 
 far above plain concrete pillars; that is to say, with stresses approach¬ 
 ing 1000 to 1200 lbs. per sq. in. Much difference of opinion still 
 exists as to the proper percentage of longitudinal and hooping steel 
 to be used. Certainly working stresses in the concrete should not 
 
 i3An excellent discussion of web reinforcement is given in: Principles of 
 Reinforced Concrete Construction; by Turneaure and Maurer, 2nd ed., 1909; 
 Arts. 86-90, 124-126. 
 
 i4Cf. Experimental Researches on Reinforced Concrete; by A. Considere; 
 translated from the French by L. S. Moisseiff; 1903. 
 
BUILDINGS OF REINFORCED CONCRETE 
 
 19 
 
 exceed 500 lbs. per sq. in. for unhooped columns, or 700 lbs. for those 
 with spiral or banded hoops. 
 
 Column longitudinal rods should be tied by horizontal hoops not 
 less than *4 inch in diameter, spaced not more than 24 inches. The 
 heavier the column the more should the bands increase in size and 
 decrease in spacing. The pitch of spiral hooping should not exceed 
 one-seventh to one-tenth the hoop diameter. 
 
 Analysis shows that purely for theoretical economy the use of 
 longitudinal steel in columns is unwarranted. This is an argument 
 in favor of structural steel columns coated with concrete as a fire¬ 
 proofing. But when reinforced concrete columns are to be used they 
 must contain longitudinal steel for practical strength requirements. 
 Where reinforced concrete columns are employed percentages of longi¬ 
 tudinal steel should not exceed 5 per cent to 6 per cent of the con¬ 
 crete area enclosed by the hooping. There are in San Francisco 
 buildings whose first story columns contain from 7 per cent to 21 per 
 cent of longitudinal rods; that is, ratio of metal cross section to con¬ 
 crete area within bands. Hooping should never be omitted. Recent 
 tests show that its actual effect in increasing the ultimate carrying 
 capacity of a column is far less than its beneficial effects regarding 
 deformation. The chief object of hooping is to increase the toughness 
 or ductility of concrete columns. Hooping in combination with longi¬ 
 tudinal steel increases, so to speak, the elasticity of the column with¬ 
 out greatly enlarging its safe carrying capacity. By toughening the 
 member it makes hooped columns much more reliable and much safer 
 and saner parts of a building frame of height and weight. It must be 
 observed that practical efficiency and toughness can only be gained 
 by hooping in combination with longitudinal steel. 
 
 In buildings over five stories in height usually it is to be observed 
 that the columns of the first floor have large percentages of longi¬ 
 tudinal steel. This is caused by the necessity of keeping diameters 
 of columns small so as not to obstruct the floor space unduly. There 
 are numerous examples of buildings, erected in San Francisco imme¬ 
 diately after the fire, in which excessive amounts of longitudinal steel 
 have been used; indeed, sufficient amounts almost to build the col¬ 
 umns of structural or rolled steel members. 
 
 Too little attention has-been paid in design to the effect of eccentric 
 loads on columns, particularly for columns which support floor slabs 
 and girders which are themselves symmetrical. It is entirely possible 
 that floor panels tributary to a column will be unequally loaded. 
 In warehouses the inequality of live loading may be great; for instance, 
 the panel on one side may be fully loaded while that on the other 
 
20 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 carries no live load at all. Such conditions will throw bending 
 moments upon the columns and also upon the floor girders. In 
 a high building of small plan dimensions in one direction the effect 
 of wind or other lateral forces may impose upon the floor girders and 
 columns still larger bending stresses akin to those produced by 
 eccentricity of floor loading. In some columns and girders eccentric 
 loading of necessity occurs, even for the dead weight; for example, 
 where projecting balconies and cornices are supported by wall col¬ 
 umns. In arranging the reinforcement steel for columns and girders 
 in these cases intelligent application of mechanical principles for 
 design must be observed, particularly in regard to so-called reverse 
 bending moment metal. 
 
 Bond of Concrete Steel. 
 
 Bond stresses should be considered especially in connection with 
 the overlapping of main reinforcement bars for beams and columns. 
 Tests show that the ultimate bond strength between plain steel bars 
 and concrete ranges from 200-250 lbs. per sq. in. of surface of contact. 
 A working bond stress of 75 lbs. per sq. in. is a usual specification. 
 For approved forms of deformed bars, bars which provide a positive 
 grip when imbedded in concrete, a safe working bond stress of 150 
 lbs. per sq. in. may be assigned. A plain round bar to develop its full 
 strength and insure safe bond working stresses should be imbedded 
 in concrete for a length not less than 62y 2 diameters; a deformed bar 
 not less than about 25 diameters. These figures indicate to what 
 extent bars should overlap so that they may transmit safely their full 
 working stress. For anchor bars in addition to the bond capacity it 
 is well to secure additional safety by bending the bars; or where short 
 anchorage distances only can be secured, lugs may be bolted or 
 screwed to the bars. 
 
 Concrete Shear. 
 
 The average ultimate shearing strength of concrete, as observed in 
 beams having no web reinforcement, may be taken at about 100 lbs. 
 per sq. in., calculated for the whole cross section. It is best not to 
 assign a working shear stress in plain concrete of more than 30 lbs. 
 per sq. in. Where the webs of beams are properly reinforced with 
 inclined bars and stirrups the allowable working shearing stress may 
 be taken as high as 100 lbs. per sq. in. The calculation for web rein¬ 
 forcement is not a simple matter, as it is based in theory upon some¬ 
 what difficult analysis. An excellent exposition for the calculation 
 of web reinforcement is given in Turneaure and Maurer’s Principles 
 of Reinforced Concrete Construction, second edition, pp. 219-227. 
 
BUILDINGS OF REINFORCED CONCRETE 
 
 21 
 
 In heavy work designs often may be criticised for crowding steel 
 bars too close together. The most common cases are the tension 
 flange of long slender girders and first-story columns in high build¬ 
 ings. When bars are massed they reduce the monolithic action of the 
 concrete, a very unfortunate effect. The larger the stone used for 
 concrete the larger should be the minimum clear spacing of rods. The 
 clear spacing of reinforcing bars should never be less than one inch 
 when using %-inch stone, nor l 1 /^ inch when using 1-inch stone. 
 
 Forms for Concrete Members. 
 
 The practical success of reinforced concrete work depends as much 
 upon the intelligent design of forms as upon any other factor. The 
 forms must be simple, easily removable, and so far as possible should 
 be used more than once. In buildings of many stories this remark 
 applies particularly to the forms for floors and columns. Roughly, the 
 cost of forms may be placed at 30 to 40 per cent of the total cost of 
 concrete in place. Buel and Hill, page 388, give instructive prices 
 and conclude as follows: “Experience on about thirty buildings shows 
 that it is rarely possible to furnish the centering and remove it for 
 much less than $4.00 per cubic yard, and that only by very bad man¬ 
 agement or under unfavorable circumstances can the cost exceed 
 $6.00 per cubic yard.” 
 
 Forms must be designed of sufficient strength and rigidity to sup¬ 
 port the concrete and any other loads that may be put upon them, 
 for at least thirty days after placing the concrete. Forms must be so 
 arranged that they are readily accessible for inspection. They must 
 not warp or bulge, due to moisture or from the lateral pressure of 
 fluid concrete. They must be water tight so that the concrete will not 
 lose water needed for crystallization or any of the finer cement fluid 
 upon which the final strength of the hardened mixture depends. Forms 
 must be laid to line and grade; they require expert carpenter work 
 and careful inspection from the foreman and engineer. Forms must be 
 cleaned of rubbish before pouring concrete. The surface of lumber 
 must fit the requirements of finish; the finish desired also affects the 
 specification for oiling forms. Forms should not be removed from the 
 under side of floor or roof slabs in less than two weeks, and preferably 
 should remain for still longer periods. The shores under beams and 
 girders should be removed later than the forms for the adjacent 
 slabs. Column forms ought always to be removed and the concrete 
 strength of columns inspected before the supports are taken from 
 beams and girders. Forms should remain longer in place in winter 
 than in summer. Important reinforced concrete members should not 
 
22 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 be poured in freezing weather. Whenever practicable forms should 
 be so built that edges of beams, girders and columns will be cham¬ 
 fered. Sharp, re-entrant angles in concrete are sources of weakness 
 and defects. The sides of beams and girders should be slightly 
 splayed, say 1 in 8 or 10; thus forms may be removed more readily. 
 In placing important reinforcement rods upon forms it is good prac¬ 
 tice to use special devices of metal, or notched blocks molded of 
 cement mortar, to insure the exact position and spacing of bars.is 
 
 Surface Finish. 
 
 The strongest argument against all-concrete buildings is the unsatis¬ 
 factory finish and color of concrete masonry. We are only beginning 
 to understand how to treat concrete surfaces. We have a great deal 
 to learn before concrete buildings will give a pleasing architectural 
 effect. To me our concrete fronts are dull and uninteresting. They 
 can not be compared with brick, terra cotta and natural stone eleva¬ 
 tions. Where coloring has been attempted I consider the results a 
 dismal failure. The best treatment, in my judgment, has been 
 achieved for buildings in which the natural concrete texture and color 
 have been preserved. 
 
 Waterproofing of Concrete. 
 
 Waterproofing of concrete is another important consideration. There 
 are three classes of treatments; first, that obtained by mixing a com¬ 
 pound consisting of an impalpable material with the cement—alum, 
 finely divided clay and soap solutions have been used with consider¬ 
 able success; second, that obtained by covering the concrete with a 
 coat of asphalt, and third, that obtained by laying impregnated paper 
 or felt against the concrete surface. To these may be added the par¬ 
 tial waterproofing which results when curtain walls, for example, are 
 painted on the outside with a rich liquid cement mortar. 
 
 The subjects of concrete finish and concrete waterproofing for the 
 past five years have commanded much of the attention of architects 
 and engineers. Recently papers on these topics have been read at the 
 annual meetings or before the conventions of a number of national 
 societies to whom the problem of reinforced concrete building is 
 naturally of absorbing interest.™ 
 
 isForms for Concrete Construction, by S. E. Thompson; paper read before 
 Assn, of Cement Users, 1907; See also Scientific American Supplement, 
 April 27, 1907. 
 
 loFor further consideration I refer the readers to: Making Concrete 
 Waterproof, by I. O. Baker, Eng. News, Vol. 62, p. 390, Oct. 7, 1909; 
 Discussion on Impervious Concrete; Trans. Am. Soc. C. E., Vol. 51. p. 114, 
 1903; The Permeability of Concrete and Methods of Waterproofing; by 
 R. H. Gaines, Eng. News, Vol. 58, p. 344, Sept. 26, 1907; A Surface Finish 
 for Concrete, by H. H. Quimby, Cement Age, Nov., 1906; The Treatment 
 
BUILDINGS OF REINFORCED CONCRETE 
 
 23 
 
 Expansion Joints. 
 
 Expansion joints are hardly required for building work, but to pre¬ 
 vent unsightly cracks from changes of temperature or from contrac¬ 
 tion of concrete through setting, light metal reinforcement should be 
 provided, running both ways, usually at 24-inch centers, over the face 
 of plane surfaces of large area, even when no rods are needed to with¬ 
 stand shearing or tensile stresses due to dead or live loadings. In 
 general, the size and spacing of cracks may be assumed to vary 
 inversely with the bond strength of the reinforcing steel per unit of 
 concrete section. The prevention of large cracks by means of rein¬ 
 forcement is a matter of using sufficient steel to force the concrete 
 to crack at small intervals. In conservative practice about V 2 per 
 cent of steel is used and gives satisfactory results. In order to dis¬ 
 tribute the deformation as much as possible, a mechanical bond bar 
 is advantageously selected. 
 
 Concrete Mixtures. 
 
 In the scope of this paper it is not necessary for me to consider 
 in detail the proportioning, mixing and placing of concrete, or to out¬ 
 line completely specifications for suitable cement, sand and broken 
 stone or gravel. 17 Concrete preferably should be mixed by machine. 
 If mixed by hand it should be spread upon a water-tight wood plat¬ 
 form. It should be placed in position immediately after mixing and 
 before initial set has taken place. Concrete for reinforced building 
 floors, columns and walls never should be retempered. Concrete re¬ 
 quiring retempering invariably must be condemned. Mixing and plac¬ 
 ing of concrete, so far as practicable, should be a continuous operation. 
 When work must stop over night or discontinue for other causes, 
 special care must be observed in bonding new to older material. Con¬ 
 crete should be poured as a wet mixture and can not be too thoroughly 
 stirred and agitated in the forms to insure a dense, uniform product, 
 filling the forms and surrounding the reinforcements completely; thus 
 avoiding air spaces and honey-comb effects. Fresh concrete must be 
 kept wet for at least one week after depositing; it must be protected 
 
 of Concrete Surfaces, by L. White, paper read before Association of Cement 
 Users, 1907, see also Eng. News, Jan. 17, 1907; The Artistic Treatment 
 of Concrete, by A. O. Elzner, Eng. Record, Jan. 12, 1907; The Finish of 
 Concrete Surfaces, by M. C. Tuttle, Boston Society of C. E., also see 
 Eng. Record, Dec. 28, 1907; The Treatment of Concrete Surfaces, by E. B. 
 Green, National Assn, of Cement Users; see also Eng. Record, Feb. 22, 
 1908. 
 
 i7The Laws of Proportioning Concrete; by W. B. Fuller and S. E. Thomp¬ 
 son; Trans. Am. Soc. C. E., Vol. 59, ,p. 67, Dec., 1907. 
 
 On the Theory of Concrete; by G. W. Rafter; Trans. Am. Soc. C E., Vol. 
 42, p. 104, Dec., 1899. 
 
24 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 from the rays of the sun, and in hot summer weather should be damp- 
 ened by sprinkling. 
 
 Only the best brands of Portland cement should be used. The con¬ 
 tractor should be required always to furnish cement subject to ap¬ 
 proval or rejection by the architect or engineer, who should submit the 
 cement to standard tests, such as are prescribed by the Committee on 
 Uniform Tests of the American Society of Civil Engineers. Sand 
 should be clean, hard, sharp, coarse and free from clay, loam, sticks, 
 organic matter and other impurities. Screenings or crusher dust from 
 broken stone, in which term is included all particles passing a ^-inch 
 screen, may, by slightly altering the proportions of the ingredients, be 
 substituted for the whole or a portion of the sand in such proportions 
 as to give a dense mixture and the same relative volumes of total 
 aggregates. Gravel, when used, should be composed of clean pebbles, 
 free from foreign matter, without excessively smooth surfaces. The 
 broken stone should consist of homogeneous pieces of hard or durable 
 rock, such as trap, granite or conglomerate. For floor slabs in build¬ 
 ings, limestone should be avoided whenever possible. In a fire it 
 tends to pop or split and may in jure a floor slab when trap would not. 
 
 1 should object in general to the use of slag or cinder for structural 
 concrete. Foundation concrete may contain stone of major dimensions 
 2 y 2 inches, one cement to about eight aggregate; approximately 1 
 cement, 3 sand, 5 stone. Concrete to resist water pressure, such 
 as in basement floors and area walls, should have stone not exceeding 
 
 2 inches, one. cement to six of aggregates; approximately 1-2-4. Plain 
 wall concrete should have 2 inch stone, one cement to seven and one- 
 half of aggregate; approximately 1-2 y 2 -5. Reinforced concrete for 
 slabs, beams, girders, curtain walls, and columns should have stone 
 never exceeding 1 in.; for thin slabs and walls with much metal 
 preferably not exceeding % in.; one of cement to six of aggregate, 
 approximately 1-2-4. In general the mixture of cement, sand and stone 
 should be so proportioned that for the particular size and fitness of 
 sand and stone the resulting concrete will be dense; that is, the voids 
 should be filled as far as practicable. Any experienced concrete 
 engineer can determine by simple methods the exact scientific propor¬ 
 tions of the three ingredients. In general for slender work and com¬ 
 plex reinforcement rods the mixture should be richer and the stone 
 smaller as the slenderness of mass and complexity of metal parts 
 increase. 
 
 Economic Proportions of Steel and Concrete. 
 
 The least costly beams and girders do not result from design calcu¬ 
 lations using the highest permissible working stresses in steel. If the 
 
BUILDINGS OF REINFORCED CONCRETE 
 
 25 
 
 allowable compressive stresses in the concrete be fixed at 400 to 500 
 lbs. per sq. in., then the economic working stress in the steel will 
 follow, given the relative costs of steel and concrete per unit of 
 volume. For normal prices, a working steel stress ranging from 
 11,000 to 14,000 lbs. per sq. in. is found economic. A prescribed work¬ 
 ing stress of 12,000 lbs. for average computations is reasonable. 
 Unfortunately architectural requirements, such as clearances and deco¬ 
 ration, so generally affect the proportions of the beam or girder in 
 width and depth that strict economy in the proportions of concrete 
 and steel can not be observed. 
 
 Members with Reinforcement Composed of Structural Shapes. 
 
 Columns with large amounts of reinforcement have been designed, 
 notably in the case of the McGraw Building, New York City. In that 
 building a structural column unit consisting of four laced angles was 
 used. These units enclose a concrete mass binding it like hooping, 
 and are themselves encased in a fireproofing of concrete. The struc¬ 
 tural steel units were designed to be themselves capable of acting as 
 columns to carry dead load of the structure. It is clear that, as a gen¬ 
 eral principle, such a scheme might be employed to carry on the steel 
 frame at least the false work and dead load of two or more floors, 
 thus enabling the placing of concrete to proceed simultaneously on 
 several floors. In such a design some of the initial dead load stress 
 would be applied to the steel of the columns before much of the con¬ 
 crete is placed, thus giving to the metal at an early stage some elastic 
 strain, enabling it thereby later to carry greater stresses than deter¬ 
 mined by the ratio of coefficients of elasticity of steel to concrete. 
 This would seem to be a source of economy, but it must be noted 
 that structural steel members riveted together by lacing cost more 
 than plain rods with wire hooping. Moreover, the initial dead load 
 erection stress must always be uncertain. It would seem, too, that 
 where angles or other rolled shapes are used, offering broad plane 
 surfaces of contact, the adhesion of the concrete to steel would not be 
 so good as for deformed bars. With such large percentages of struc¬ 
 tural steel the bond to the concrete is not readily secured. There are 
 apt to be planes of division or cleavage detracting from the mono¬ 
 lithic character which should be insisted upon in reinforced concrete 
 design. 
 
 Columns with rolled steel reinforcement have been criticised severely 
 by some engineers and approved by others. The subject is in its 
 infancy. The ideas involved might readily be applied also to the design 
 of main girders and beams. Indeed, so-called unit frames of various 
 
26 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 types have been proposed, particularly for reinforced concrete beams. 
 It is entirely feasible at present to erect a steel frame work capable 
 of carrying its own load, false work and erecting machinery, later to 
 be clothed in concrete. I remember that one building was so con¬ 
 structed in San Francisco, namely, the Owl drug store’s building on 
 Mission Street. There appear to be some advantages in such a sys¬ 
 tem. It insures the definite placing of the reinforcement metal and 
 enables a designer to know that the exact connections will be made 
 which he provided, thus securing strength at the joints of the struc¬ 
 ture. Moreover, more definite continuity in columns and between col¬ 
 umns and girders would result without relying too much upon the intel¬ 
 ligence and integrity of t he field foreman. I question, however, 
 whether a system of this character will ever become fashionable. With 
 its structural merits it has the attendant defect of increasing costs. 
 At any rate, in the present state of reinforced concrete construction 
 it may be applied successfully to single units such as columns and 
 beams, but not to the whole structure as one articulated metal cage. 
 
 Fire Resisting Qualities of Reinforced Concrete. 
 
 There are certain qualities of reinforced concrete construction which 
 must appeal to fire insurance men. All evidence to date justifies us 
 in concluding that the steel, where properly imbedded in the concrete, 
 will be protected from corrosion. It is admitted that concrete, with 
 the possible exception of brick, gives a most satisfactory fire protec¬ 
 tion. Laboratory fire tests and experiences from the conflagrations of 
 Baltimore and San Francisco indicate that from 2 in. to 3 in. of con¬ 
 crete will offer practically a complete protection to steel. From per¬ 
 sonal observation in San Francisco it is my opinion that properly 
 designed reinforced concrete members like columns and beams will 
 safely resist any ordinary fire; provided the members have their metal 
 sufficiently coated with concrete. In order to cut down the expense of 
 reinforced concrete buildings in comparison to buildings with struc¬ 
 tural steel frames it has been too much the custom to decrease costs 
 by eliminating concrete, which would be specified eagerly as a protect¬ 
 ing surface to the structural steel members of an alternative building. 
 It is further my observation in examining reinforced concrete buildings 
 constructed in San Francisco during the last three years that their 
 secondary parts are composed too commonly of combustible materials. 
 It is a great mistake to spend much money on a reinforced concrete 
 frame and then finish the floors, partitions and casings chiefly of wood. 
 Partitions, particularly, have been the great offenders in this respect. 
 What would otherwise be an ordinary fire would become severely 
 
BUILDINGS OF REINFORCED CONCRETE 
 
 27 
 
 destructive where a large part of the trim of the building in close 
 contact with the structural concrete is highly combustible. It should 
 be remembered that a well-built reinforced concrete frame will cost 
 money to take down when once too severely injured by a fire. This 
 element of cost in razing a fire loss ought to be considered. In the 
 case of factories and warehouses the more inflammable the contents 
 to be stored, the less should be the inflammable fixtures of the build¬ 
 ing, the thicker also the concrete fire protection. My argument in this 
 respect is much akin to remarks which might have been made con¬ 
 cerning first-class class B buildings which were destroyed in 1906 in 
 San Francisco. I refer to structures with self-supporting outer walls 
 and independent interior frames partially of rolled steel and cast iron 
 with much wood for secondary parts. One of the most costly examples 
 was the Emporium Building; a less notable instance the Cowell Build¬ 
 ing. To be sure, both structures were subjected to most intense heat, 
 due to the nature of their stored contents, aside from the inflammable 
 fixtures of the structures themselves. The ruins of such buildings 
 after great fires always offer great hindrance to rapid reconstruction. 
 A great conflagration destroys them completely so far as repairs are 
 concerned, but leaves the remains of twisted steel members and 
 cracked masonry in a sufficient stiff and tangled mass to make it 
 necessary to expend large sums of money and to consume much time 
 in disposing of the wreck. 
 
 Municipal Building Ordinances Versus Building Inspection. 
 
 While my chief object has been to discuss reinforced concrete, you 
 will pardon me if I refer to some matters affecting not merely rein¬ 
 forced concrete building construction, but the construction of buildings 
 in general in a city like San Francisco. 
 
 Immediately after the fire the building ordinance was revised; as 
 well it might be. The old ordinance, though it was spoken of as a 
 building law, was really composed of many different and sometimes 
 conflicting enactments of the Board of Supervisors made at different 
 times during the last ten years. Of course it was full of contradictory 
 clauses and open to the criticism that it was indefinite and of poor 
 arrangement. While the present building law may be criticised also, 
 it is a vast improvement upon the old ordinance. An ordinance natu¬ 
 rally can not be perfect. No such instrument ever was or could be. 
 Ours has many defects and contains a number of articles that should 
 be changed as soon as possible. Any one remembering the circum¬ 
 stances and pressure, however, under which the new ordinance was 
 arranged will have considerable respect for the authors of the law, 
 
28 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 for it is based on sound practice and good scientific judgment. It is 
 gratifying to note that for some time past a revision of the building 
 law has been under contemplation. While we will be anxious to use 
 the revised ordinance, it is to be deplored that it may have little 
 practical effect; for one of the most unfortunate conditions affecting 
 building in San Francisco is the lack of sufficient inspection on the 
 part of the building department. Earlier in my remarks I have given 
 examples of actual buildings built since 1907 in which the law has been 
 grossly disobeyed; that is, its structural prescriptions. The law may 
 be conservative and, if rigorously enforced, would considerably in¬ 
 crease the structural cost of a building. But such an argument can not 
 justify the acceptance of designs going to the other extreme of reck¬ 
 less economy, leading to the erection of buildings of questionable 
 stiffness, if not of certain weakness. It is the details of San Fran¬ 
 cisco buildings which are inspected and not their larger requirements 
 for strength. It is more likely that an owner is obliged to place a petty 
 fire escape in accordance with the letter of the ordinance than that 
 he is restrained from erecting a frame so slender that reinforced 
 beams are stressed to 1200 lbs. per sq. in. in the concrete. 
 
 It would not be just to make these strictures upon the building de¬ 
 partment and its inspecting force without at the same time observing 
 that they are hardly to blame. At present the city does not provide 
 an adequate force. We can not expect the limited force to give due 
 attention to all matters which our building ordinance proposes shall 
 be considered in connection with the erection of buildings. The staff 
 as now constituted is more capable to examine plumbing and electric 
 fixtures than to check the stress sheets for the frame-work or foun¬ 
 dations. What we need is emphasis on inspection and not on a build¬ 
 ing ordinance. A building ordinance should not be looked upon as a 
 text book or as a hand book whose purpose is to instruct a greenhorn 
 in engineering or architecture. A building law can not and never should 
 be a specification. It ought to be as terse and to the point as possible 
 without treating details, and have for its object the protection of the 
 city and the general public against persons who want to build too 
 poorly. The building ordinance should provide definite penalties if 
 its clauses are broken. While an ordinance in part partakes of the 
 nature of a specification, it should only do so as far as it is necessary 
 to elucidate some of its provisions. As a law the ordinance tells what 
 shall be done, and in order that its provisions may be enforced, it in 
 some cases tells how the work shall be done. It is a function of a 
 specification to tell how to do a thing. The sole and vital reason for 
 the existence of a building ordinance, however, is merely to tell what 
 
BUILDINGS OF REINFORCED CONCRETE 
 
 29 
 
 to do. What is needed in San Francisco is not so much a newly revised 
 ordinance with greater detail of specifications, but rather the present 
 ordinance with a few modifications and, if possible, greater brevity, 
 coupled with an efficient building department commanding the services 
 of properly trained inspectors. I should be glad to see more recogni¬ 
 tion in our building law of those clauses relating to fire hazard, fire 
 protection and prevention which are outlined in the building code 
 recommended by the National Board of Fire Underwriters. 
 
 Fire Testing Stations. 
 
 Immediately after our fire it was the desire of some members of the 
 building community to establish a fire testing station in San Francisco. 
 The scheme had the earnest support of many architects, engineers, 
 contractors, and manufacturers of building materials. Representa¬ 
 tives of the city fire department and municipal government were inter¬ 
 ested. The laboratories of the universities were ready to co-operate. 
 It was found that a fire testing station means an expensive establish¬ 
 ment and that it costs money to run one on an efficient and practical 
 scale. It was argued by some who visited us at that time from the 
 East that we had no need for a fire testing station; that it was useless 
 to duplicate results. We were told that we might as well save our 
 money and benefit by Eastern experiments. It is true that we have 
 learned much from the fire testing station conducted at Columbia 
 University in co-operation with the building department of the city of 
 New York. We can benefit by perusing the reports of W. C. Robin¬ 
 son, Chief Engineer of the Underwriters’ Laboratories at Chicago. 
 Reports from the Insurance Engineering Experiment Station at Boston 
 and from the special Testing of Materials Laboratories of the U. S. 
 Geological Survey, at St. Louis, are always instructive. It may be that 
 it would be a mistake for us to establish a fire testing station on the 
 Pacific Coast. But I am not convinced that this is the case. California 
 is separated by mountains and deserts from the Mississippi Valley 
 almost as though an ocean intervened. We have our distinct local 
 problems. Beside, and what is more to the point, it is worth some¬ 
 thing to us to make a few tests of our own. There is a distinct ele¬ 
 ment of value in having been present at and concerned with, or having 
 been an eye-witness to special fire tests of materials used in or 
 furnished by the local market. 
 
 Conclusions. 
 
 In my opening remarks I referred to a possible salutary relation 
 existing between fire insurance underwriting and principles of engi¬ 
 neering design as factors of knowledge worth while to an insurance 
 
30 
 
 BUILDINGS OF REINFORCED CONCRETE 
 
 man. I have concluded with reference to the status of the San Fran¬ 
 cisco building ordinance and the worth of a fire testing station. Be¬ 
 tween these digressions I have attempted to give you what I thought 
 might be a suggestive description of the present art of building in 
 reinforced concrete. I have attempted to indicate that almost no type 
 of future construction will be entirely free of parts in reinforced con¬ 
 crete. I have reminded you that for the highest types of building 
 reinforced concrete is used for most essential parts and may be used 
 to the entire exclusion of other forms of construction. I have outlined 
 the important specifications for safe stresses, for economic proportions 
 of parts of the frame, and for the distribution of concrete and metal. 
 One of my main objects was to explain that whenever used, reinforced 
 concrete design requires a high degree of engineering talent. While 
 I do not advocate its use for high buildings, I trust I have made clear 
 that it can be recommended unconditionally for heavy construction, 
 such as warehouses, or for low buildings, such as schools and hos¬ 
 pitals. It has effective fire resisting qualities. We have heard so 
 much about earthquakes that I hesitate to use the term, but I must 
 observe that reinforced concrete lends itself most readily to sensible 
 earthquake construction. 
 
 In short, for buildings, reinforced concrete is a most valuable 
 material. We have much yet to learn, but always we will have to be 
 masters of engineering arts to use the combination of steel and con¬ 
 crete intelligently. It is no wonder, therefore, that some structures 
 have been failures. It is rather to be wondered that so few structures 
 have collapsed. When a new type of building has been suddenly 
 introduced, we should rather be surprised if we could not recall cases 
 where owners have learned from bitter experience that they might 
 have built more cheaply with structural steel. Nevertheless, sum¬ 
 ming up all arguments, for and against, I believe I could not be 
 considered partisan to reinforced concrete in recommending it gener¬ 
 ously to the attention of the building community and particularly to 
 gentlemen interested in fire insurance. 
 
 Bibliography Not Specially Mentioned in the Text. 
 
 1. La Construction en Ciment Arme; by C. Berger and V. Guillerme; 
 
 Paris, 1902. 
 
 2. Reinforced Concrete; reports from different countries; Trans. Am. 
 
 Soc. C. E.; Vol. 54, Part E; Papers read at the Engineering 
 convention, St. Louis, 1904. 
 
 3. Le Beton Arme; by M. Christophe. 
 
BUILDINGS OP REINFORCED CONCRETE 
 
 31 
 
 4. Handbuch fur Eisenbetonbau; by F. von Emperger. 
 
 5. Graphical Handbook for Reinforced Concrete Design; by J. 
 
 Hawkesworth. 
 
 6. Engineer’s Pocket Book of Reinforced Concrete; by E. L. Heiden- 
 
 reich. 
 
 7. Steel Concrete Construction; by G. Hill; Trans. Am. Soc. C. E.; 
 
 Vol. 39, p. 617; 1898. 
 
 8. Reinforced Concrete; by C. F. Marsh and W. Dunn. 
 
 9. Reinforced Concrete; A Manual of Practice; by E. McCullough. 
 
 10. Reinforced Concrete Pocket Book; by L. J. Mensch. 
 
 11. Concrete and Reinforced Concrete Construction; by A. Homer 
 
 Reid. 
 
 12. Reports of Tests; Bulletins of the University of Illinois Engineer¬ 
 
 ing Experiment Station. 
 
 13. A Treatise on Concrete, Plain and Reinforced; by F. W. Taylor 
 
 and S. E. Thompson. 
 
 14. Traite Theorique et Practique de la Resistance des Materiaux 
 
 Appliques au Beton et au Ciment Arme; by N. de Tedesco and 
 A. Maurel. 
 
 15. Concrete Steel Construction; Reasons and Rules for Proper 
 
 Design; by Edwin Thatcher. 
 
 16. Concrete Steel; by W. N. Twelvetrees. 
 
 17. A Handbook on Reinforced Concrete; by F. D. Warren. 
 
 18. Beton-Kalendar; published by Beton and Eisen, with the co-opera¬ 
 
 tion of experts. 
 
 19. Report of the Committee on Reinforced Concrete; Proceedings 
 
 Am. Soc. Testing Mats., Vol. 6, p. 85, 1906. 
 
 20. Report of the Commission du Ciment Arme; to the Minister of 
 
 Public Works; Paris, 1907. 
 
 21 . Concrete Engineers’ and Contractors’ Pocket Book; Technical Pub¬ 
 
 lishing Co.; Cleveland, Ohio. 
 
 22. Report of the Committee on Reinforced Concrete; National Asso¬ 
 
 ciation of Cement Users. 
 
 23. Report of the British Joint Committee on Reinforced Concrete; cf. 
 
 review in Engineering Record, Vol. 56, p. 103, July 27, 1907. 
 
 24. Report of the Committee on Cement for Building Construction; 
 
 Eleventh Annual Meeting, National Fire Protection Associa¬ 
 tion, May, 1907. 
 
32 BUILDINGS OF REINFORCED CONCRETE 
 
 25. Philadelphia Regulations in Regard to the Use of Reinforced Con¬ 
 
 crete; see special reference thereto in Engineering News, Vol. 
 58, p. 514, Nov. 14, 1907. 
 
 26. The Use of Reinforced Concrete in Engineering Structures; An 
 
 Informal Discussion; Trans. Am. Soc. C. E., Vol. 61, p. 35, 
 Dec., 1908. 
 
 27. The New Regulations of the Prussian Government for Reinforced 
 
 Concrete Buildings; see extracts in Cement, Vol. 9, p. 69, July, 
 1908. 
 
 28. Economic Designs of Reinforced Concrete Floor Systems; by J. S. 
 
 Sewell; Trans. Am. Soc. C. E., Vol. 56, p. 252. 
 
 29. Reports of Tests; Bulletins of the University of Wisconsin; Engi¬ 
 
 neering Series. 
 
 30. Designing Methods; Reinforced Concrete Construction; Expanded 
 
 Metal and Corrugated Bar Co.; St. Louis. 
 
 31. General Specifications for Concrete Work as Applied to Building 
 
 Construction; by W. J. Watson, 1908. 
 
 32. Progress Report of Special Committee on Concrete and Reinforced 
 
 Concrete; presented to the Annual Meeting, Jan. 20, 1909, Am. 
 Soc. C. E.