Issue 9

Sir Courtauld Thomson, chairman of the Limmer and Trinidad Lake Asphalt Company, in his speech at the annual general meeting in March, referred to the attention the company’s staff was paying to the problem of vibration, and the writers, who have worked in collaboration with the company’s staff, are now able to reproduce some results of experiments recently carried out. W.P. Digby and R.B. Fairthorne

The Department of Scientific and Industrial Research has just issued, through H.M. Stationery Office, a volume of its special reports on the mineral resources of Great Britain. It deals with the geological relations, nature and uses, and mineral, chemical and physical properties of ball clays, that is to say, of those plastic "transported" clays which, when fired in an oxidising atmosphere to the temperature of certain pottery ovens approximately 1,150 deg.-1,200 deg. C.-have a white or nearly white colour. They are formed by the decomposition of felspathic rocks, by natural agencies. In this decomposition, silicates such as the felspars break down, and the products ultimately undergo hydration with the formation of the hydrated silicate of aluminium, kaolinite, and, in many cases, mixtures of hydrated oxides. Where these products are found resting in the parent rock, the clays are termed residual; where they have been transported and deposited elsewhere, they are known as transported clays. The china clays of Cornwall are typical examples of the former; the ball clays discussed in this memoir are characteristic examples of the latter. Dr. Alex Scott

The Minister of Transport has caused a circular to be issued to all highway authorities in Great Britain drawing attention to the provision of the Bridges Act, 1929. The main provisions of this Act are designed to facilitate the procedure for the reconstruction of weak bridges in private ownership, e.g., in the ownership of railway companies, canal companies, etc. Many of these bridges, as is well known, are not fitted to carry modern traffic, and the restrictions which their owners are authorised by law to impose on their use by heavy vehicles have caused considerable inconvenience and loss to trade and industry.

A correspondent of "The Times" gave recently some exceedingly interesting details of some of the great Colonial water power developments in hand or under contemplation. These include schemes of hydro-electric power which are being carried out in tropical countries. Apart from the £6,000,000 Shannon project, which stands in a different category, the harnessing of the River Jordan below Lake Tiberias, the approaching completion of the Niger River storage dam, and the offer of tenders for the Pangani River works in Tanganyika illustrate the general demand for cheap and efficient power. The great Mandi scheme in the Himalayas will cost £4,000,000, and produce a maximum of 38,000 kilowatts.

The preliminary report by Mott, Hay and Anderson, consulting engineers, of Westminster, to the Ministry of Transport regarding a proposed road bridge over the Forth at Queensferry has been sent to the local authorities for consideration. The report recommends that the bridge be constructed about a mile dwnstream from the railway bridge, the cost being estimated at £5,570,000 or £6,110,000, according to the route selected for the north approach. A bridge of the suspension type and having a main span of 2,400 ft. with a minimum clearance of 150 ft.-the same as the Forth Bridge-is recommended. The report states thathe present railway bridge was completed in 1889 and was located at the narrowest part of the river, advantage being taken of the rocky island of Inch-Garvie for the site of one of the main piers. It therefore occupies the best position in this stretch of the river. The bridge consists of a main span of 2,400 ft., with a minimum clearance above H.W.O.S.T. of 150 ft. This clearance is the same as that of the Forth Bridge, but while in the case of that bridge the clearance rapidly diminishes under the cantilevers, in the proposed bridge the clearance is maintained under the whole span. The side spans are each 1,040 ft. with clearance above H.W.O.S.T., diminishing from about 150 ft.

Under the title “Siemensbauten,” a which striking volume has been issued by the German Siemens concern, wherein are reproduced many fine photographs of the company's buildings, at Siemensstadt, and elsewhere, erected to the designs of the head of the firm’s constructional department, Regierungsbaumeister Hans Herilein. W.E. Fuller

A very interesting description of the construction of the new Stare Bridge, Warwickshire, was given by Mr. D. H. Brown, County Surveyor of Warwickshire, in a paper prepared for a meeting of the Institution of Municipal and County Engineers, West Midlands District, which was held at Kenilworth recently.

It is an old saying that we learn more by our failures than from our successes, but, unfortunately, in this country engineers are prone to hide their failures, rather than to publish them so that their brethren may benefit. H.J. Deane

Statistics relating to the Portland cement industry in 1928, compiled by the United States Bureau of Mines, Department of Commerce, from the final returns of the producers for the year, which are, however, still subject to revision, confirm the estimates published by the Bureau of Mines early in January. Production of Portland cement in 1928--176,195,488 barrels-was the largest quantity manufactured thus far in any year, exceeding that in 1927, the next highest year in production, by 2 per cent.

The number of buildings erected in the United States by the use of electric arc welding has increased 50 per cent. during the space of one year, according to a list prepared by Frank P. McKibben, nationally known authority on the subject. In a list published under his name in the "General Electric Review" for July, 1928, 100 structures were mentioned, including bridges, buildings, cars, cranes, frames and towers, ships, tanks, tests, etc., and this total, according to the revised figures, is now 138.

Damp-proof casings and methods of providing against damp are matters which concern the structural engineer, if only in some stages of his task, and Messrs. F. T. Carson and F. V. Worthington, in the July issue of the “Bureau of Standards Journal of Research" have furnished much valuable data, which might well be used in the formulation of a standard specification. The work was carried out at the request of the National Lumber Manufacturers’ Association and 36 samples of building papers, consisting of asphalte-saturated, paraffin-saturated, laminated and asphslte treated and machine finished papers, were tested for weight, thickness, tensile-breaking strength, bursting strength, tearing resistance, water resistance and air-permeability.

The Western Society of Engineers of Pennsylvania has inaugurated a comprehensive test on two panels of steel structure at the plant of the American Bridge Company, Gary, Ind. The object of these tests is to determine the strength added to a typical steel utructure by the concrete used for fireproofing and regulation concrete slab floors.

The recently issued specification for concrete and reinforced concrete prepared by a committee of the Canadian Engineering Standards Association (No. A23-1929. Price $1)is a highly interesting document. It has lately been the subject of a critical review in Engineering, which, in a much condensed form, is reproduced below.

The Department of Scientific and Industrial Research has, it is announced, completed arrangements for an important investigation into the application of modern theory of structures to the design of steel structures. The investigation is to extend over several years. Its objective is to secure, if possible, scientific results which may justify a more economical use of steel in building construction.

We have received from Mr. Hal Williams a letter pointing out that the photograph of the new Heinz Building at Harlesden, shown on the front cover of The Structural Engineer for August, hardly does justice to the architectural and constructional features of that interesting addition to London's "far West" industrial buildings. Mr. Hal Williams says that the photograph shown below conveys a much better impression of the finished building, in the construction of which time was an all-important element. That the work was completed within the time specified was due very largely to the excellent work of the structural steel contractors, Messrs. Peirson & Co., Ltd., to whom he pays a well-deserved tribute.

The introduction of scientific engineering methods in the measurements of racing yachts is probably a matter in which few of our readers have ever had the opportunity of indulging. First of all, to those who know little of sailing, and still less of the complications of measurement for "rating" of sailing yachts, we should state that before a boat can compete in any but handicap races she must be measured in order to see that she complies strictly with the rules laid down for "class" yachts.

In the Middle Ages, when mankind had considerably more leisure than at present for the consideration of what are now termed academic questions, one of the favourite subjects of discussion is said to have been, "Which came first; the hen or the egg?" No satisfactory conclusion appears ever to have been reached, and a busy world has since decided that the solution of the problem is one of the things that do not matter. We might ask nowadays, and with profit-the question being by no means as academical as it seems -who came first; the architect, or the engineer, civil, mechanical or structural? The first enterprising arboreal who bent a branch to serve as a foundation, or as a shelter for its tentative home; the first prehistoric man who adapted a cave to the purposes of a dwelling, was only imitating what the lower animals had done before: employing materials of the nature and properties of which instinct first, and a process of trial and error later, had afforded some rough empirical knowledge. He was thus certainly a structural engineer, one, that is, who employs materials for the purpose, first and foremost, of making a structure, even as the beaver, or the bird had done before him. Of purposive architectural design, or of knowledge of civil or mechanical engineering in all this there is little trace; the materials at hand were taken and adapted, according to their nature and suitability to a crude purpose. It seems almost indisputable, therefore, that a knowledge of the properties of materials, combined with eventual experience of their behaviour when built into a structure, must have been the primitive, and almost simultaneous bases of all knowledge of structures. These, and the selection of a suitable site and foundation; a tree, or a rock; a hummock, the open plain, or a treacherous and marshy tract necessitating, at the dictate of experience, the use of piles mask the early stages in the evolution of the structural engineer. His subsequent progress and development have been due to his increasing knowledge of materials and of their applications, but, more especially, of their limitations. To those with which nature originally endowed him he has added others. He has laid under contribution the discoveries of chemistry, and metallurgy, and has himself invented, and inspired the invention of the new materials suited to the new requirements he is called upon constantly to fulfil.

At first glance it may appear somewhat absurd to talk to Structural Engineers, or, indeed, any engineer, about welding or the high temperature treatment of modern industrial metals; most members of the engineering profession are more or less familiar with the theory and main principles governing the use of one or other of the half dozen fusive agents now universally employed by the specialist, but one finds quite commonly that an impression exists that welding has positive and well-defined limitations, or that its employment is only possible in certain classes of work and in relation to the union of certain metals. This prejudice is so widespread that it may be well at, the outset to assert without qualification that, in mechanical repairs and reconstructions and in the recreation of any of the industrial metals, there is practically no limit to its application. The idea, no doubt, had its origin in the unfortunate experience a certain number who have been the victims of incompetent operators, who have either failed to do what was required to be done or have employed an unsuitable process or fusive agent, with the inevitable result that the unit or member treated has lost efficiency or been irreparably damaged. C.W. Brett