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The Structural Engineer

THIS specification covers the design of bridges, and is a notable addition to the matter extant upon this subject. It is interesting as there is no other generally-known specification in this country with which to compare it; and it is difficult to find any text books which cover all the points of design called for in this specification, except by having recourse to matter published abroad. The specification appears to be moulded along the lines of the Canadian and American, and to some extent the German specifications, and comparison with these is interesting.

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The Structural Engineer

The Acme Stone Breaker This machine is well known amongst councils, quarry owners and, in fact, all users of stone-crushers, and, as is generally well known, is a departure from the stereotyped form of Blake crusher, which is supplied by all other first-class makers of such machines. The special nature of this machine is the combination in one part of the two chief moving parts of the Blake type of stonebreaker, thus obtaining a direct action and increased weight and momentum of the operating part which affects the breaking of the stone. The direct action of the machine eliminates unnecessary mechanical complications of levers, toggle plates, connecting rods of the Blake type of power consumption. The direct action results in a sharp crusher, and thereby resulting in economy in upkeep costs and hammer-like blow at the top of the swing jaw where the large pieces of stone are encountered, while there is a secondary finishing and clearing below at the bottom of the mouth, and under equal conditions, than from any other machine on the abling the machine to deal with a larger output, size for site market. The largest movement is at the top of the mouth, where the stone enters the machine, and this enables maximum sizes of stone to be fed into the mouth. In the Blake type of crusher, as made by all other manufacturers, there is very little movement at the top of the mouth, and a simple backward and forward swinging motion at the bottom of the jaws.

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The Structural Engineer

Sir,-I find it difficult to reply to Mr. F.E. Drury’s criticism of my article on the above subject, as he has so largely misunderstood my argument and has ascribed to me views which I do not hold.

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The Structural Engineer

A meetinf of the Institution was held at Denison House, Vauxhall Bridge Road, London, S. W., on Thursday, February 21, 1924, when a paper on “Column Fallacies” was read by Dr. E. H. Salmon, D.Sc.

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The Structural Engineer

The Trade Position Statistics relating to trade, although eminently useful, are not always a true index of the position, for they fail of necessity to reflect the actual feelings of traders at any particular moment. Some of the figures from which we are accustomed to judge the commercial outlook are indeed, apt to be misleading at the present time, for while they show in most respects a continuance of the slight improvement which has been noticeable during the past few months in business circles confidence has given place to some degree of hesitancy. The Board of Trade returns for the month of February were encouraging when compared with the January figure, and show a general increase over the corresponding month of the previous year, although they are, of course, affected by the rise in commodity prices during the past twelve months. Commodity prices themselves show a further rise for February, the Board of Trade index number being 66.9 per cent. higher than in 1913, compared with 65.4 per cent. for January and 53.3 per cent. in February, 1923, while last month's official figures of unemployment also showed an improvement. Other statistics, such as bank clearings and advances, which may also be regarded as an index to the activity of trade, continue to show improvement, while the volume of commercial bills in the Money Market has fairly well maintained the increase which has been noticeable recently. There is nevertheless a less confident feeling among those actually engaged in commerce than existed a month or so ago, and this slight change of sentiment is naturally not yet reflected in the available statistics. Caution on the part of traders is only natural in view of the strikes which have actually taken place, the labour unrest which is reported from several quarters, and, above all, by the fear of a stoppage in the coal industry. A further disturbing factor has been the violent fluctuations in several of the European exchanges, and particularly in the value of the French franc. Depreciation in the currency of any country, although an unfavourable factor in the long run from the national point of view, gives a bonus to the exporter for the time being, for the rise in internal prices, which invariably follows, always lags behind the fall in the external value of the currency. Exchange fluctuations in either direction, on the scale to which we have become accustomed during the past few years are, however, a serious deterrent to international trade. The present tendency for the incipient trade expansion to hesitate is also possibly due to a realisation of the fact that the laying down of relief works and the hastening forward of railway renewal programmes for the relief of unemployment can only be a temporary palliative for commercial stagnation. It is obvious that the works to which reference has just been made are being paid for out of the nation's capital, although, as in the case of railway renewals and extensions, that capital may have b

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The Structural Engineer

PAINT spraying machinery has been developed along somewhat divergent lines, but for our present purpose it is not necessary to dwell upon those types which have been designed for the finer kinds of decorative work. Our immediate concern is with painting the heavier forms of buildings, girders and stanchions, large expanses of concrete and the like.

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The Structural Engineer

Calcium Chloride in Cement If from 6 to 10 per cent of calcium chloride is added to cement on mixing when the temperature is below 20 deg. Fahr., not only is freezing prevented, but setting is hastened and increased hardness secured. But such all addition is not safe in reinforced work unless the steel is completely imbedded. In ordinary rendering on metal lathing, there were early signs of bad deterioration of the lathing. (U.S.A., Bureau of Standards)

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The Structural Engineer

In describing this work it is the object to show how pre-eminently suitable reinforced concrete proves to be in the construction of industrial buildings, and particularly buildings used for the manufacture and storing articles of food. Alfred S. Grunspan

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The Structural Engineer

All available experience in experimental data shows that for slabs covering considerable areas, subjected to loading which may be concentrated over relatively small areas or for slabs which may be insufficiently supported over similar areas, bending moments are inevitably induced in the slab, producing tensile stresses in the underside of the slab, which in ordinary cases exceed those resultant from contraflexure in the upper faces. Harry Weston

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The Structural Engineer

The annual dinner of the Institution was held at the Criterion Restaurant, the whole of the Italian Roof Garden having been specially booked, on St. Patrick’s Day, Monday, March 17, 1924. For the third successive year the attendance record was broken, over 300 members and guests being present.

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The Structural Engineer

“Inspection to be final, as no responsibility can be accepted for such materail after it has left the sellers’ works. Where testing or inspection has to be done, the buyer must make the necessary arrangements for this to be carried out as soon as possible after receipt of ndotice that the material has been rolled. All bars from which test pieces have been taken must be accepted by the buyers if complying with the specification of tests. For material under 5/16 in. thick, bend test only will be given in accordance with the British standard specification for such material.” H.J. Davey

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The Structural Engineer

FEW bridges in this country have attracted so much attention and study as the Old Bridge at Pontypridd. Not only is it remarkable in itself, but it is rendered more so as a structure in that at the time of its construction very little was known about the statics of the arch. Also it was the work of a self-taught mason, named William Edwards. Born at Eglwysilian, by the time he was sixteen he was known to be the best builder of dry walls within a wide area. While engaged in enclosing a field for a farmer about two miles from Caerphilly, he saw the foundations prepared for a blacksmith’s shed, and later on the mixing of mortar, a substance hitherto unknown to him. The sight inspired him to study the practices of the mason, and being commissioned to build a house and workshop for a friend the successful achievement thereof soon led to other building operations. Captain F.W. Rees

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The Structural Engineer

THE satisfactory roofing of large areas has always been a problem presenting somewhat additional difficulties to the engineer. All the customary essentials with regard to a roof are present, viz., that it should be water-tight, be as inexpensive to keep in repair as possible, and that it should have a good appearance, but there is added to these requirements, if anything, the more important one that the material used for covering must be light. In the past, for this purpose, galvanised iron has been possibly most used, but of recent years cement which is entering into so many of our building products, has been combined with asbestos and a new roofing material is now becoming the vogue.

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The Structural Engineer

IV. Mortar Voids and Water Content, The magnitude of the voids and its change with additions of water will depend upon the gradation of the particles of F.A., each A. having its own individuality. J. Singleton-Green

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The Structural Engineer

A TRUE record of the repairs of Tintern Abbey will not fail to indicate that a very great advance in the scientific analysis, understanding and treatment of ancient monuments was made possible by cxpericnce as the work progressed, and that as the result of this fuller knowledge certain expedients were adopted in the later stages of the work which would have been considered absolutely beyond the scope of the conservator’s art at the commencement of operations. William Harvey

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