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NOliTEI WALES .SANITARY INSPECTORS'…

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NOliTEI WALES .SANITARY INSPECTORS' ASSOCIA- TION. INTERESTING MEETING AT RHYL. VISIT TO THE NEW PAVILSON AND MARINE GARDENS, DESCRIPTION OF FERRO CONCRETE WORK BY MR HARRY BURKE, C.E. On Saturday the members of the North Wales Saaitary Inspectors' Association visaed iiiiyl for their sessional meeting. The day was boauu- f lùJy lmoC, and the new marine gardons nmh pavilion works were soon to the bøsl advantage. Too company first a-ssembied in the tea-rooms adjoining' the gardens, and here Mr A. A. doifJail (town surveyor), who has designed the gard 'ns and their buildings, described his work. He said that. Rhyl for many years. was noted for its s&.ids, sunshine and shmniis, bui of late years it had beoomo notorious for tiros, two iiiie pavilions being destroyed in that way. To lires and sand, therefore, the scheme now being can- ned out might be attributed. In the winter months sand w&i blown up from the shore In enormous quantities, and the oost. of its removal amounted to about 3d in the i). This serious item, and the fact that Rhyl had no pavi.ion after the Palace was destroyed, induced the C'ouiioJ to do something theruso.ivJs. Following the introduction of tho echeme by Mr J. H. Eil Is a deputation was appointed to visit Yar- mouth, where t.he sand trouble had been suc- cessfully overcome. Tho result waa that the town had decided to go in for marine gardens and a new pavilion. Four acres of foreshore were taken up ill the scheme, three being de- voted to the gardens. The plans of the new pavilion were entrusted to Messrs Maxwell and Tuki.' and F. B. Smith, after several eminent archil ei-is had sent in designs. Mr Goodall then described the gardens, which are surrounded on two sides by shelters, the south boundary being the Promenade, and the west side the pavilion. In the oentre of the gardens is a fine bandstand, with an asphalted surrounding. The laying out of the gardens and sea-wall had been done dpl)artnwittav, the estimated cost being £ 4750, while the pavilion, which is the first of its kind in the I MVd: Kingdom, will cost about £9250, the material used in its construction being as far as practi- cable ferro, or reinforced, concrete. VISIT TO THE PAVILION. The delegates were conducted over the build- ing by Mr Stead (resident engineer), who de- scribed the method by which forro concrete was used. At present the auditorium is a confusion of timber uprights and boardings, serving to support and mould the concrete baioony and the concrete cornice above which will spring the central dome. Great, interest wag taken in the pillars which wiil support the dome, and in order to test the strength of the ferro concrete several of the party tested it with hammers, but failed to make any impression on it. It wat* explained that the gallery is in one solid piece, the cantilever principle being followed, while the dome is made of ferro concrete in one li/ncj Span, the outside being of white granite with red spar rib,. The marino baioony Will surround, thQ dome, and this portion of the work was in progress on Saturday. Being tho first, oocasion oOn which the delegates had seen ferro concreic, used they were naturally much interested 1n the work. BUSINESS MEETING: A WELCOME. The noting was held subsequently in tho Council Chamber, when the chair was taken by Air G. A. Tavorner (chairman of the Council, Among those present were: Mr A. Ilhydw-tiij Jones (vice-chairman), Mr 11. A. Tudv, Mr J. II F 113 (rhe originator of the scheme), Mr Edmund Hughes, Mr J. W. Jones; Dr. Williams, .Wrexham; Messrs R H. Parry (president, of the Association), Gwvrfal; W. E. Ilughœ, Oonuahs Quay; Levi John, Conway; D. L. Williams, ,VVTre-vliam; J. A. Jones. Wroxharn; G. Davics. 13.1aenau Feetirnog; \V. II. VVorrall, Bangor; W. Littler, Llandudno; J. J. Marks, ex-chairman of the I^u-ndudno Council, R. I<owe, Rhyl; J. O. Jones, Wrexham; E. Evans, Nantglyn; W. Jonos, Ruthin; Mr Griffiths, contractor fpr the pavilion; Mr Stead, resident engineer; Mr Buckncll; Mr H. Roberts, foreman of tho pavil- ion; Mr Harry Burko, C.E., Manchester; Mr R. J. Lftig-lif--s, Penmaenmiiwr (?/oeretary), and others. Mr TAVERNER said ho had the greatest plea- sure in welcoming the Association to Ithyl, and did so in the name of the Council, of thot town. and on his own behalf. He was told that it was three years ago since they had visited, Illiyl, and that it was eleven years sinoe their first visit. Ho hoped that, as they had en- joyed that afternoon the salubrious air of the town they would come more often, as they must realise that Rhyl was a health resort not exeehod in the Principality (hear,, hear). lie thought they had derived somo profit and pleasure frpm an inspection of the fine pavilion they were putting up, and from their visit to the new marine gardens—the first of their kind on ISorih Wales Coast (hear, hear) 110 regretted that their Medical Officer (Dr. A. Eyton Lloyd) could not be present, for the Rhyl pooplo felt that lie was an official who was not excelled, if equalled, in the Principality (hear, hear). That Association was a purely educational institution, and he trusted that their vijit would be of bene- fit to all concerned. Mr MARKS proposed a. hearty vote of thanks to Mr Tuverner for his welcome. They were greatly interosjed in the works they had seen, and believed they would be not only a great at- traction to Rilyl, but a lasting monument to the foresight and pluck of the Rhyl Council (ap- plause). It would be very foolish on the part of anyone interested in another watering-place to h0 jcaiQus of what Rhyl was doiog-(hear, hear)—as whatever directly benetlted one water- ing piaoa the North Wale-a Coast also inctto rectly benefited other towns as well. Judging from the warm welcome extended to the Associa- tion that afternoon he was of opinion that it would not be three years before they cam.ei agitm (laughter and hear, hear). The vote of thanks was carried with applause, and their Mr Parry took the cliair for tho business meeting. THE BUSINESS SESSION. Mr John Evans, Wrexham, w elected a mem- hpcr, and the CHAIRMAN expressed tho hope that -.i-e new men] ber would be as loyal to tho Association as had been his Wrexham colleagues. PLANING AND HOUSING BILL. The Secretary placed before the mooting copies oi various Bills now before the House of Com- mons dealing with sanitary matters, and Mr MARK'S urged that they should take no- tice of section b7, sub-sectio.n 3 of the Planing and Housing Bill, which, ho said, placed the medical officers in a peculiar position, as it pro- posed to take away from County and District Council the power of appointing medical offi- cers. He was afraid that that vai a retrograde Step, as it might load to the appointing of numerous medical officers at salanes of about £ 10, and no matter how capable medical gentle- men might be in their ordinary profession they did not "possess that training which medical offi- cers of health required. He proposed that they urge the Parliamentary Committee of tho Central Body io take steps to oppose tins clause. Mr WORRALL (Bangor) seconded, and it was carried. DAIRIES AND COWSHEDS.. The PRESIDENT said he had intended tp address them on the subject of dairies and cow- sheds, which was a matter of great interest to many but in view of the fact that they had present Mr Harry Burke, C.E., of Manchester, who was to read a paper on "Ferro Concrete, he would postpone tus remarks to a later date. From what they had seen of ferro concrete at the new pavilion they were most anxious to hear the paper, as the subject was new to maey of then, and it was of the greatest importance to them that they should know the possibilities of such a wonderful material, and not lose any opportunity of gaining knowledge about it. INTERESTING PAPER ON FERRO CONCRETE. Mr HARRY BURKE, C.E., Manchester, gaid The Pantheon at Rome is a remarkable and convincing testimony to the value and durability of concrete. It was built by Agrippa two thousand years ago, and stands to-day as the most perfect of the old olassio buildings in Rome. The walls of the circular part are nearly 20 foet in thickness, while the roof is a hemi- spherical concrete dome of 142 feet 6 inches fipan with a circular opening in the centre about 30 feet in diameter. It ctoes not show a single crack, which is remarkable, apd one can- net doubt that the success which the early Romano had in applying concrete in important eut-;inooiing- and architectural operations ft ui t>2 surpass* in presout- genera-ti-on* 1 he works oi thano early Roman architects and budders in oeojent have endured the ravages of time, and still existing side by side with those built ot natural stone are sufficient eviddnce of the fact I cl the durability of concrete in building oon- struotu-n. More remarkable does it seem that ti-Lot-0 early Romans have had such a. success with their concrete buildings, seeing that they were "built with Potsoland, a material greatly inferior to the modern Portland, conient. From i this you will see that ooncreto has boon in use i7 an a material of construction from very early tirrwe, and itu use haii largely increased in re- cent years aa it, became possible to obtain cetnr-nt of good and reliable quality with greater facility. Wo can now get a ocment from any of the best makers sufficiently safe for any class J of structure, and to pass any tcst which the Britsh Standard Committee .-ave franio • readon why the use of concrete has been i till a few years ago was owing to its oornpara- tive weakness in its resistance to tonsUe ana transverse strain,, but when reiutorccd by lroa or stool to withstand tlieso strains, its iicss is largely increased, ana it. can be to- many purposes not otherwise possible- Probably the first concrete reinforced wa* a floor patented bv a Mr Vi ilkinson, oi j- cast lo-ou-'l n ne in '1854. This (-on,tsted of a lir^- re-sisting floor made of concrete, and rointoi-ed by the use of iron burs or wire ropes,^ but as a nillitt-Lr of fact a gardener living in the zioigli- b our hood of Paris, named Monter, is renera ty given the cre-dit for introducing ferro concrete- He required some large pots -in which to p*ant orange trees, and cfuioeived the of LL-in-, concrete with wire netting embedded in it to give it .trength. For this he received a dip- loma at the Paris Exhibition in 1878, but linding that tho illye-Ili lOll covered a much larger field tlian he had supposed, lie brought the to the attention of engineers and capita no s with the result that in a comparative short time many tanks, bridge. sewers, and the like were built: on this system in France, Germany, and Austria- It was only a step from this to the construction of more important structures. n chief objection to the Monier system is that a large number of rods must be used, and it is necessary to weave these rods together or to lattice them and secure with wire at taiei intersections. As those rods are usually p e but two or three inches apart this is a tedIous and exr>ensive ojKration, and one wiiicn rC- quires considerable care on the part of the mechanic or fixer, becau.se the network of steel must be kept near the lower surface of the con- crete in order that its full benefit may be avail- able, while at tho same time the rods must be entirely embedded in the concrete. lhougn ferro concrete is only in its infancy in fcius country, yot in France, Germany, and parti- cularly in America great headway has been made. In America probably more systems are at work. The American railways now design their own work, and specify the bar they re- quiro for the particular purpose, keeping it on- tirely under their own oontrot. The Americans have gone into the subject very minutely, and are now probably the best experts. Though there are many kind's and many systems oi ferro, or reinforced, concrete they t. Jer very little from .each other, and practically ro..I.t be designed very much the same. In concrete and steel the problem is to elfoc-t their combination in such a manner that they may be employed to satisfy the requirements of a good design and sound construction. Concrete has a high coefficient of residence to compressive stresses, while its resistance to tensile and shearing strcti^es may for all practical purposes be con- sidered nil. Steel on the oontrary offers great resistance both to tensile and shearing stresses. From the properties of tho two materia.s arises the idea of making use of one in order to complete or correct the shortcomings of the other. The.re then remains to be found the most effective and economical method of com- bining t.ile two material in a structure, and to make them work simultaneously and harmon- iously, that is, to use the concrete for compres- sion and! to meet the tensile and shearing stress- es bv the use of irckii or steel. If we compa,re a ferro concrete beam to a rolled steel joist we have the steel rod's at the bottom of the beam, whidh is equal to the area of the bottom por- tion of the joist for taking the tensile stress, and the ooncrete at the top taking the com- pression just as il:e top flange of the stzel girder is doing. The web of the girder is formed by the concrete which encases the bars, and con- nects the axis of compression to the axis of tension, but this would be a very weak web indeed if it was composed solely of concrete, and could not resist the shearing stresses. The effect of shearing stresses is to cause the fol- mation of cracks in the beam at the angle of 45 degrees, with tho horizontal, close to the supports. This angle decreases and the cracks become of less importance as they get nearer the middle of the span. To meet these stressczi in many cases stirrups are placed vertically, and their number is increased at the supports, where the shearing is greatest, to fake this. Without, stirrups tho bars, or some of them at the bottom of the beam, are bent up at an angle of 45 degrees, cutting the natural axis at the line of support or bearing. This, of course, ca.n only be done where you have a bar which acts as a mechanical bond. Again, in ferro concrete work the beams are mostly designed continuously, with the result that the bars are carried along into the next beam, thereby making a tie from one to the other. In a sre-el frame connection it is impossible to get this in the same way. CAUSES OF CRACKS. In considering tensile stresses at the upper part of the beains cl-oee to the supports, or in the words, reverse bending, you. will often no- tice that in a concrete floor carried by steel joists, a crack occurs over these points. ThM is through the steel not being in the correct plaoe. In a ferro concrete floor, over the supports and from about a fourth of the span alternate bars taking the tensile stresses in the lower portion of the floor should be bent up and carried within an inch of the top of the concrete to a fourth of the span on the further side of the support and vice-versa. This will take up any reverse bending action and rarely will you find a crack in the concrete over the supports in a fcrro concrete slab- In passing to pillars both steel and concrete are suitable for its construction. A pillar so constructed would be unsafe be. YOnd' a certain limit, and would offer a low oo- efficient of safety. High as is the cc-fficient of compression in concrete a rupture may occur owing to the low resistance of concrete to ten- sile stresses. To obviate this distance pieces are spirally wound, or wire strips about six inches apart, are placed to form a belt round the pillar. These not only hold together the upright bars in the pillar and prevent them from buckling, but they also form round the core of concrete between the main bars, a sort of belt which compresses it, and moreover gives to that volume of concrete delimited by the in- ternal prism just described, and the outer sur- face of the pillar—the fibre which will strengthen it and communicate to it the necessary tensile properties. The load which can be supported by ferro concrete pillars in this manner is con- siderable, and1 equal to several times that which a pillar of identical dimensions made of con- crete pure and simple could carry. In heavy retaining walls, bridges or arch works, ferro concrete is adaptable and economical. IS FERRO CONCRETE AS ECONOMICAL AS ORDINARY METHODS? In the majority of cases, yes, by 15 per cent. We have recently designed some precipitation tanks for taking sewage, etc.. for a large paper ruill ill Lancashire. The original intention was to have the tanks 7-ft. high and 12-ft. wide, the walls of common brick built in cement 2-ft. thick. The capacity was 750.000 gallons. For ferro con- crete the walls are 12 inches thick at the bottom and 6 inches at the top. In the centre 5-8in. bars sp&ce<i 6_m, oentro-s are pla-oed, and nail- way up the walls they are made 12-inehe cen- way up the walls they are made 12-inehe cen- tres. The floors of the tanks are reinforced by 3-8-1 n. bars 18-in. centres, and made 6 inches thick. The having was 23 per cent, in ftvour of ferro concrete over the brick wall schome. For the same works, say the beating room floor that is carrying the engines for boating the puLp up, and of which there are 24 weighing, when full, close on 40 tons each—160 by 80. As a compari- son against the steel frame the following taking strength was how it came out:- Ferro concrete beam. 22 by 14, JE3; 15 by 6 R. S. joists, £ 4 8s. Ferro concrete beam, 25 by 18, £ 4; 18 by 7, R. S. joists, J65 16s 3d. Ferro concrete beam, 25 by 18, £ 4; 20 by 7 £ R. S. jOltoJ.s, £6 18. "Ferro concrete beam, 30 bv 20, £ 6 3s; 24 by 7A, R. S. joists, £ 7 5s. Forro concrete boiam, 23 by 15, £ 4 lis 6d; Forro concrete boiam, 28 by 15, C4 113 6d; IS by 7, R. S. joists, £ 6 18& 9d. From this you wiU see the saving over ordinary floor construction. For retaining walls we have I iu.?t completed for the fame works a wall 22-ft. hjo-h and 360-ft. long. The section of the wall consists of buttresses 2 feet thick and 11 feet at the ba-se, tapering to 6 mcihes at the top. These were Krviced 10 feet ecu tree, and in between the buttress a slab 6 inches, thick of concrete bav- in"- bars 5 inoli thick running from buttress to buttress Thev were spaced 4-in., 8-tn., or 12-m., according to the strength required for height. The ea-t was equal to a rubbie wall at 9B 6d per cubic vard, winch ia an exceptionally low figure, (train living the extra filling room behind the wall which meant a saving of about 8 feet at the base between the slabs. For t.he same works we are constructing machine sheds, the roofs of which are pitched at 45 degreea Thtve roofs have no inside tics, simply being tied together from the outside, leaving a perfectly clean slope inside. The oost works out at 9s to 9s 6d per suiperficiai ya.rd, including slater. The reason of the. ties being outside is to avoid condensation accumulating and falling on the machines, there- by spoiling tlie paper. This in a paper mill is very eerious, an4 though the. roof li" been very hard to design, yet it is an ideal one for such works. In ordinary flooring, say for a cotton mill, etc., taking a load of 2cwt. safe, you would want a joist about 6 by 3 section over 15-ft. span, and spacing those at 18 inch centres, the cost per yard would be about 2s 6d. The bar reinforoe- ment. using steel of higli tensile such as is being used m the Rhyl Now Pavilion, you would want yard would be about.26 6d. The bar reinforoe- ment. using steel of high tensile such as is being used m the Rhyl Now Pavilion, you would want I say for a. 15 feet s-pan, half an inch bars, 6-in. centres, and the cost wotim be a'bout Is 9d per square yard, henoo i6 a good caving, lor floors or fitrueturesi where you have a moving or vibrations load. it is proved that a ro.d or ferro concrete floor is much steadier than one whid, is built of steel girders or brick arches. The II Pavilion, which is being built for the Rhyl Coun- cil. by Messrs Maxwell and Titlie and Mr F. B. Smith, and which you have been over, it a good illustration of ferro concrete work. To my mind, and what I have seen. I believe thi* build- ing. when completed, will give very great satis- faction. Again, you know that it does not want 'painting to keep the rust, etc.. away, but its strength will increase daily, m-akuig AN ABSOLUTE MONOLITHIC STRUC- T U ILL. It is as near fire-proof as is possible to (tosigri and construct. For a. theatre or hah tin* bo esential. Great credit should be given t-c .he architects for their fort-thought in constructing tris work a* they are doing. Ihey aie a firm with many large works behind them, for in- stance. Blackpool and New Brighton lowers and the Exhibuioii 'buiklm^.s in Man-chi^ter in 1837. 1 In the short time allowed for tins paper it is difficult to touch very much on rlhe subject of reinforced concrete, yet, before there are a few et-ven:iaU I should like to give you. Con- 6taiit practice show w, that oxide of iron can- not exist in contact with concrete, and that rust- ed bars embedded in concrete will in the courte of a mo-nth or so be as bright as new, the tust being deoxidized by the format ion cf-errite of calcium, which forms a protectlve skin round the har. Again, it murt o!«-o be borne m nnnd that COILcrtta iwed in fer.ro concrete is markeuiy different from ordinary concrete, in its compo- sition and in its make, and m the way it is em- ploved. It should also be composed ot materials of small volume (three-quarters of an inch medti), the proportion of sand and stone bell, vaijttted fo as io give- a. ooncrete quite full, and if u.ed 1l those small quantities at a time arid vigorour-ty rammed, allowing no cavities,—that is what is required. The adherence of concrete to steel haj been questioned many a time many people differ. Approximately. 5701bs. to the square wcih of metal come in contact with the concrete. In realitv thie adhersion is mechanical bond as it res ul Us from the oement particles entering sin all microscopical pores on the sun&oc of the This mieroseopical bond is neither strong or per- manent. The development of the working st-resa in the metal produces a slight etretca of same, and a corresponding shrinkage in cross section which impairs the mtoroscopical bond above men- tioned. For example, suppose toe 1-in. bar Í6 developing a stress of 12.000Ilw. per square inch then it hart a stretch .0004 inches per inch of lera-th, and its shrinkage in each laternal dimen- sion i* approximately .0002 inches (the square root of one plus a very ainall quantity being plus half for all practical purposes). Now, while the above quantity is no doubt email, it is by no means mieerceoopical, and it seeuis likely t.hat such a fhrinkage would have a very great in- fluence on the bond. In work where you re- quiro anchorage, or my own idea oif ferro, oon- crete. is that you should have a bar which has a mechanical bond of its own. 1 here, are, many, and i.he one used on the Rhyl Pavilion is prob- ably the best. I am not paying this because I am interested in it, but for this reason1 here may be a chance of the concrete sliding over or away from the bar, causing cracks, which will often enough be up to three or four feet. Now, by a bar as the one ^een oai the Rhyl works, it io proved from actual practice that the dip cannot be mere than the indent of the bar. a.nd which in the largest bar is 1 ^-in., hence liiy rea- son. In conclusion, Mr Burke paid reinforced con- crete was an extremely interesting study, and in the future he had no doubt it would 00 used very

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