Issue 2

The following is an extract from a paper on “Ocean Beach Esplanade, San Francisco, California,” by M. M. O’Shaughnessy, M.Am.Soc.C.E., which appeared in the Proceedings of the Am.Soc.C.E., for November 1923, page 1846.

LIKE it or not, concrete is with us. It is with us to stay and grows faster in its hold day by day. These facts being realised our course is obvious. It is for us to change those aspects of concrete which we do not like; and this we can do only by familiarising ourselves with not only the existing products but also with the processes of its manufacture and the machinery used therein. By this means only shall we place ourselves in a position to improve and enhance the possibilities of concrete. To recognise the full justice of this point of view it is necessary to go back in mind only a very few years and to recall the horrible monstrosities which resulted from the undisciplined introduction of cast iron mantle registers. These, at first, until taken under the wing of certain architectural designers were mongrels until refinement was induced into their outward expressions. H. Bryant Newbold

Concrete Roads, Dear Sir,-With reference to the correspondence in No. 1, Vol. II., of THE STRUCTURAL ENGINEER, now to hand, I think I may be able to supply some information regarding a reinforced concrete road I have just completed. This road, known as the Great West Raad Extension, is a continuation of the Great West Road, and will (when the remaining sections are complete) link up the Bath Road at the Great West Road Junction with the Staines Eoad at Bedfont.

A Meeting of the Institution was held at Denison House, Vauxhall Bridge Road, London, S.W.l, on Thursday, December 20th, 1923, when a paper on "The Practical Designing of Structural Steelwork Details" was read by Mr. Joseph B. Clarke; after which a vote of thanks was proposed by MR. S. BYLANDER, M.I.Struct.E., in the following terms:- He said it was very delightful to listen to a paper of this kind, where a thorough study had been made of the subject, both mathematically and practically. He thoroughly agreed with the principle of the paper, that connections should be denoted by the efficiency; but whether or not each individaal connection should be given a number to represent its strength he was not quite so sure about. Personally, he considered that the simplest method, and the method which undoubtedly would be followed in future by good designers, was to have a table giving the efficiency factor for any one group of rivets with a certain eccentricity. Mr. Clarke had called it the “index number,” but he (Mr. Bylander) preferred the term “efficiency factor.” Mr. Clarke had shown a simple formula for arriving at this factor, and, after all, that was the essential part of the paper. It would be agreed that it was a very laborious matter to calculate the actual strength of every group of rivets used for connections, but Mr. Clarke had worked out and given structural engineers a factor which they could use, without this labour of ascertaining the polar moment of inertia, of a group of rivets, and further, of ascertaining the maximum strength, knowing the stress due to twisting. He did not quite understand why Mr. Clarke had selected the graphical method of ascertaining the factor, from the stress due to the loading and the stress due to the twisting. He himself would prefer to adopt the mathematical formula shown on the screen, and he hoped that, Mr. Clarke would, later, add the details of the derivation of his formula. Obviously the formula he had given indicated the solution by a graphical method. It could be expressed equally well under the root sign. Mr. Clarke had made a statement that the vertical and horizontal component of the stress due to twisting was derived from a formula, but he had not stated the derivation of that formula. He had said that it was, of course, important that th6 stress was ascertained for the outermost rivet, but that, said Mr. Bylander, was not necessarily so. It must be the rivet on which the greatest total stress occurred, and not necessarily the rivet which was the greatest distance away from the centre. Then, Mr. Clarke had not drawn attention to two or three conditions which were very essential to the truth of his argument, namely, that certain assumptions had to be made. The assumption that the centre of gravity of the rivet was the point around which the connection would turn in case any movement took place within the elastic limit, was one, it was an assumption which he quite agreed with, because it was a si

WHEN the writer was asked to compare the theoretical strength of certain small sash sections, he adopted a method which gave comparative results with as great an accuracy as the problem merited. W.A. Green

THE method of calculation commonly adopted among steel work designers in allowing for eccentricity of loading in the design of steel columns is to find thc equivalent central load by means of the ecccntricity coeficients which are usually tabulated in the various manufacturers' handbooks, and to design, the column or stanchion for this equivalent central load from the particular column formula which they fancy or which municipal authorities specify. Ewart S. Andrews

The essential factors that I have in mind for the purpose of this short article are labour and materials. There are others, including that of need. Space will not, however, permit oi my dealing with this aspect of the question, although I would summarise the views that I have previously and more definitely expressed with reference to it by saying that the need is very great indeed; and although variously estimated there can be no doubt that it is limited in practice only by the availability of our resources in labour, material and finance. Sir Charles T. Ruthen

Prof. S. W. Perrott, in opening the discussion, said he would like to suggest that each member taking part would mention his name. As Mr. Clarke was not present to hear the remarks it was essential in dealing with each point in the paper, to do so as clearly as possible in order that the reports sent forward to Mr. Clarke would be as clear as possible. Continuing, he said that this was a paper very suitable for meetings, and one which should be welcomed because matters of this kind were always wanted to deal with. It is in the details that new things can be done with great advantage. The suggestions set out in this paper formed a type of detail which might be of great use to structural engineers. He hoped everyone would contribute to it. The Hon. Secretary then read a written criticism from Mr. Durose which we hope to publish in a later issue.

A “Monolith ” pile is a concrete pile which is cast in its permanent position in a hole prepared for the purpose. The hole for the pile is formed by driving a hollow steel cylinder or tube, 16 ins. diameter, with the bottom end sealed with a special shoe, in the same manner as a pile. When the hollow or tube is driven to the final penetration, it is filled with plastic concrete to a height of several feet (according to the length of the pile) above the desired finished top of the pile. Thecylinder or tube is thcn slowly withdrawn, leaving the shoe in position. (See Figure 1.) In this manner, the concrete fills the entire void left by the hollow cylihder or tube, and any irregularities of the earth, cementing and uniting the surroundirig soil, this gives thc “Monolith” pile a frictional resistance greater than any other type of pile of equal diameter and length. In all cases where “Monolith” piles have been exposed, they have been found almost perfectly cylindrical and of a greater diameter than l6 ins.

Heat Insulation. UNDER the supervision of Prof. A. Bugge, of the Norwegian Technical Academy, a series of 24 huts were erected, identical as to design and dimensions, but differing as to the materials used in construction. These huts consisted of a single chamber, 6 ft. 6 3/4 in, by 6 ft. 6 3/4 in. by 7 ft. 4 1/2 in., built over a cellar, which, together with the roof, was carefully insulated. Each hut was heated by electricity, automatically controlled by a thermo-regulator. Thermal measurements were taken during l 1/2 winters. These measurements were plotted, the results obtained with a wooden-framed house being taken as 100 for purposes of comparison. The two huts which directly interest our readers were hut 8, built of three-air-duct concrete blocks on the Lean system, fixed by means of tarred dowels, the hollow spaces being filled with coke breeze at floor level to a depth equal to the thickness of the floor, matchboarded and plastered. This was rated at 140. Hut 18, with walls of High-Rib lathing fixed to wood framing, the external wall with 1 1/4 in. plaster rendering, the inner lathing rendered with 3/4 in. of plaster, a space of 5 in. being left between the two sections. This was rated at 129. The best insulated house was constructed of two walls of matchboard, packed between with sawdust; rated at 96.5. It was found that hollow walls gave better insulation than solid walls, but where these are built of bricks or blocks the mortar between joints should not be allowed to obtrude inwardly or droppings of mortar to accumulate. That in hollow walls, the heaviest and thickest should invariably be the inner one, so as to guard it against damp. It was found that a lightly-burnt brick was a better non-conductor than a hard burnt brick; it was therefore recommended that the bulk of the wall should be built of medium bricks with hard brick outside skin. (Teknisk ukebald.) Messrs. H. Kreuger and A. Erikson,

From time to time arguments for and against the Channel Tunnel have appeared in the daily press and elsewhere, so that a few brief notes on the various schemes may be interesting. Whilst it would be beyond the province of THE STRUCTURAL ENGINEER to discuss its advantages and disadvantages from a commercial point of view, to the writer the advantages appear obvious. These have been recently set out by the Association "France-Grande-Bretagne.”

This issue of THE STRUCTURAL ENGINEER contains my Presidential Address to The Institution of Structural Engineers. As the reader may or may not have discovered, I took as my text the History of the Invention and Development of Portland Cement, this year being the Centenary of the invention of that cement, which has had so large an influence on the profession af Structural Engineering. Having taken a text, I had, more or less, to confine myself to a discourse upon it, and the result was that I was left with no space or time in which to dilate upon the aims, activities and engagements of the Institution of which I have the hanour to be President. I will now endeavour to give an account of my Stewardship as far as it has gone, and to foreshadow what I hope will be done during the remainder of my period of office.

Ladies and Gentlemen, With the example of my illustrious predecessors before me, I feel that I am at a loss in knowing how to give you such an Address as will be a worthy follower to those which have already been delivered to this Institution. Major James Petrie

The subject of the attrition of concrete surfaces exposed to sea action was dealt with by me in a paper read on January 22nd, 1920, before the Concrete Institute, now known as the lnstitutim of Structural Engineers. The object of the present communication is to describe the results of the experiments referred to in that paper. I endeavoured there to analyse the mechanism of attrition, going on from that to investigate the factors governing, and the possible methods for reducing attrition. It was shown that the injury to the concrete surface was primarily due to a fracturing and breaking away of the particles forming that surface, the conditions being exceptionally favourable for the removal of the broken material by the water. In the latter respect such surfaces as are now considered differ fundamentally from horizontal surfaces upon which the products of disintegration are allowed to collect in the form of dust, forming a protecting layer. It was shown, broadly, that whether or not surface would resist the attack of boulders driven against it by the sea would depend upon two main factors :-(n) The stress produced on the material by the blows of the boulders.(b) The resistance of such material to disintegration. Dr. J.S. Owens

THE above heading is the title of a recent paper dealing with the prortioning of concrete. The information is of such value that it is proposed to give a summary of the paper arranged so that the main divisions will be similar to thosc of the Bulletin fo facilitate reference. J. Singleton-Green