1844.] 



THE CIVIL ENGINEER AND ARCHITECrS JOURNAL. 



431 



the particles by drawing them asunder at the bottom, and crushing them at 

 the top. Consequently it was found, by the very numerous. Ingenious, and 

 laborious experiments of my friend Mr. Eaton Hodgliinson, that the bottom 

 flange came out a proportion of about one-half of the whole section of the 

 beam ; and, in the beams in question, the quantity of metal in the bottom 

 flange is probably not more than from a quarter to one-third of the section. 

 The bottom flange should be parabolas ; and, in order to give it the correct 

 form, this beam would have to be enlarged along the lower flange, and then 

 it would be of equal strength along the whole line of the beam. I mention 

 this merely to show the necessity which exists for getting greater strength, 

 by throwing the greatest portion of the metal into the lower flange. 



"These facts having been proved by direct experiment, it is important to 

 all those concerned in the construction of fire-proof buildings, in which the 

 lives of the public and the property of individuals are at stake, that the form 

 of beams and the section cjf greatest strength should be jterfectly and thoroughly 

 understood; and to those unacquainted with the subject, we would beg to 

 refer them to Mr. Hotlgkinson's paper on the strength of iron beams, in the 

 fifth vol. second series, of the ' Memoirs of the Literary and Philosophical 

 Society of Manchester.' In ordinary cases, we should not have troubled the 

 jury with these remarks; but in a case of such importance as the present, 

 where the lives of so many peraons have been sacrificed to defective know- 

 ledge and skill in the construction of buildings, wherein considerations of 

 such importance are involved, we have considered it our duty thus publicly 

 to direct attention to the subject, not only as regards the present but in all 

 future cases, and respectfully to urge upon the proprietors of mills, and of 

 other buildings containing workpeople, the necessity which exists for a more 

 secure and perfect system of building, and for a further devclopement of the 

 principles upon which fire-proof edifices are founded. If this suggestion is 

 properly received and acted upon, we have reason to believe, that we shall 

 not again have occasion to investigate occurrences of so lameniable and so 

 distressing a nature. We have already observed, that the beams «,«. s, in 

 the preceding sketch were strengtlicned ; not, however, in the bottom flange, 

 but in the middle part of the team, where they are thickened, and where it 

 was absolutely of no use. Had the same quantity of metal Ijeen given to the 

 lower flange, these beams (the weakest in tlie building*) would have carried 

 nearly double the weight : and thus, by a proper and judicious distribution of 

 the metals, the building as well as the lives of the people, would have been 

 saved. These observations apply to all the other beams of the mill, which 

 are also defective as respects their strength." 



" In computing the weights upon each beam, it was found that those sup- 

 porting the arches of ten feet six inches, and those of eleven feet six inches 

 span, nad to support a load (without machinery) respectively of ten and 

 eleven tons." 



That is thus :— We compute the weight of the arch at about 10 tons for the 

 short span, and 11 tons for the other ; and that is about the weight required, 



" And those sustaining the ends of the longitudinal beams were acted upon 

 with a load of 13J tons." 



That is, particularly, the two shown here [the two outside beams, a. a], be- 

 cause each of them had not only half the long arch to carry, but also half, 

 or more than half, of the short arches on the other side. 



"Now, if we take the sections of these beams, and calculate the weights 

 necessary to break them, when laid upon the middle, it will be found that the 

 breaking weights for tlie beams a, a, a, and h,J>, b, &c. will be nearly the 

 same, or about 9} tons. This is the breaking weight of an average quality of 

 iron; and, allowing for tlie difl'erence of metals, it could not be raised much 

 above 10 or lOJ tons." 



They must of necessity be broken, with a weight of from 10 to lOJ tons. 1 

 have taken the average at 10 tons. 



" The breaking weight would therefore be about 10 tons when the beam is 

 loaded in the middle, and 20 tons when equally distributed over the whole 

 surface of the projecting flange of the beam." 



Now, there is a wide difference between the beam being loaded on one point 

 in or near the middle, and being loaded along the whole beam. In the latter 

 case, it would carry just double the weight, Consequently, you have in ar- 

 ches an equally distrbuted weight ; so that a beam supporting them, and 

 which would break with 10 tons, applied to a single point in or near the 

 middle of the beam, will take 20 tons to break it, when the weight is so dis- 

 tributed. 



"Having ascertained the bearing of the beams, we shall next compare 

 their strength with the actual loads they were called upon to sustain ; and, 

 in making that comparason. it must be borne in mind that the two beams 

 a. a, next the side wall, had their loads unequally distributed, which reduced 

 their bearing powers to 15 tons." 



Now, you see, that on the west side of the beam o, it was equal to carry 10 

 tons ; but the cross beams on the east side threw the whole weight upon the 

 middle of the beam ; and, consequently, instead of the breaking weight of 

 the beam a being 20 tons (as it would have been, if equally distributed], it 

 was only 15 tons, having a distribution of the weight only on one side ; and 

 the weight on the other bearing upon one point only. 



" Now, the load which these beams had to support was 13} tons, 8J tons 

 being supported on a single point on one side, and 5J tons distributed over 

 the surface of the opposite flange on the other. From this it will be seen, 

 that the actual load was to the breaking weight as the numbers 1375 to 15, 



[* Mr. Faivbairn added, that these beams were rather weaker in original con- 

 struction than the transverse beams ; and that the whole of them were cer- 

 tainly not such as would be considered safe.] 



or as 1 to 109 being within a mere fraction, or one tenth, of absolute des- 

 truction." 



That was the very critical state in which this building was standing, as to 

 those beams, just previously to the fall. 



" Viewing the subject in this light, and taking the above calculations as 

 data, we are no longer at a loss as to the cause of the accident. Even sup- 

 posing the arches to have stood, it will appear obvious that so close an ap- 

 proximation of the breaking weight to the actual load was extremely unsafe ; 

 and that, ander such circumstances, no precautions could have prevented the 

 rupture of the transverse beams n, a, a, whenever they happened to be sub- 

 jected 10 the slightest impact, or any vibrationg motion tending to disturb 

 the parts under strain, and eventually, still further, to lessen their already too 

 much diminished powers of resistance." 



It is clear, that they must have gone some time or other. I believe Mr. Bell- 

 bouse and I are of the same opinion, that that was the real cause of the ac- 

 cident; that, probably, from the vibratory action of the mill gearing on be- 

 ing set going, or from some other cause, the slightest shock in the wi rid 

 would fracture either of these beams (a, a,) ; and then it is easy to conceive 

 how the others would follow. It would not only carry the gable end down, 

 but it would loosen the whole of these arches on the same floor, and the 

 whole would soon come down in the mass. It would be impossible to account 

 for the entire destruction of the whole building, unless, by some cause, the 

 whole of the framework of one floor came down; and one of these beams 

 [a, a] giving way, would account for that. — The Foreman : I called the coro- 

 ner's attention at the time to the evidence of Mills, taken as he lay in bed, 

 to the effect, that after the arch fell, where he was working, the whole gable- 

 end fell. This seems to confirm the view taken by Mr. Fairbairn. — The Coro- 

 ner: "It fell bay by bay," was Mills's expression. — Mr. Fairbairn: Of 

 course, we were not present at the time of the accident. All we can do is to 

 reason upon it from the facts given in evidence : — 



" Irrespective of the weakness of the iron beams, w hich we consider as the 

 primary cause of the accident, we would beg to advert to the tie-rods, which, 

 although suflScient in number and strength, were not judiciously placed as 

 respects their position for resisting the strain of the arch, their miiximum 

 poini of tension at the bottom flange of the beam ; but, that Ijeing inconve- 

 nient, they should on no account be placed hiiiber than the soffit of the arch ; 

 and in this position, they would perforate the neutral axis, and give sufficient 

 security to the arch, without injuring the strength of the beam. Instead, 

 however, of approaching this point, they were on the top of the beam, and 

 18 inches from the bottom flange." 



Now, with respect to the tie-rods, instead of their being placed above the 

 arch, the true position of the tie-rods should be below, forming the chord of 

 an arc. But that, especially in low rooms, would be found exceedingly in- 

 convenient; and, according to the experience of Mr. Bellhouse and myself, 

 we say, that it should never go higher than the soffit of the arch. 



" As respects the aiches, we found the versed sine, or rise of the arch, too 

 low ; on mo.st occasions they arc \\ inclies to the toot." 

 We generally prefer an inch and a half rise to every foot of span, if it can 

 be obtained. If this be done, you will find the arch come out a very fair and 

 correct form of arch ; and it is only at the sacrifice of an inch or two in ihe 

 floor, which would not be an object, com|iared with the security of the arches. 

 1 do not know that this has any relerence to the present inquiry, except that 

 it is a proof that the arches were too low. — Mr. Bellhouse : I think it bears 

 directly upon it ; because the arch in the top slory gave way or sunk, simply 

 from that cause, — a want of sufficient rise. — Mr. Fairbairn : I have already 

 stated, that we had two objects in our inijuiry ; the one to trace out the true 

 cause of this accident, and the other to direct public attention to these facts, 

 in order to prevent not only tlie loss of property, but, above all things, the 

 loss of life. In this latter view, every thing bearing on the construction of 

 these buildings is important. 



" As respects the arches, we found the versed sine, or rise of the arch, too 

 low : on most occasions they .■ire IJ inches to the foot. But, in order to in- 

 sure perfect security, we should advise, in all future buildings of this descrip- 

 tion, ihat the rise be U inches to every foot of span. In the arch which first 

 gave way, the rise was only a small fraction above an inch, having a rise of 

 only 12 inches in a span of 11 feet (i inches-" 



[The Foreman suggested an alteration in the reptrt (which is made above), 

 to prevent any mistake as to the supposition that the proportion of rise was 

 the same in all the arches; and Mr. Fairbairn observed thai, of course, a 

 rise of one inch in every foot of span would be a greater rise in that arch 

 which was only 10 feet 2 inches, than it would be in that which was II feet 6 

 inches. The correction was accordingly made, and Mr. Fairbairn resumed 

 reading.] 



"On viewing the columns, several imperfections were observed in the va- 

 riable thickness of the metal ; but, in other respects, the pillars wcie satis- 

 factory, and presented no features of weakness indicating nanger from those 

 parts: one inch more in oiameier, inth ilie same weight ol metal, would, 

 however. Iiave given greater seiunly and greater sirengili." 

 On the whole it would have been better, probably, if the pillars had been a 

 little larger. 



" We cannot close this report, without adverting to the anxious solicitude 

 of Messrs. Radclille. and the strong desire evinced by those gentlemen, to 

 have every part of the siruciure upon the first and strongest principle; and 

 we should imperfectly discharge our duty, if we neglected, on this occasion, 



3i* 



