Magnitude | Consequence (and some examples) |
---|---|
1 to 3 | recorded on local seismographs, but generally not felt |
3 to 4 | often felt, no damage |
5 | felt widely, slight damage near epicentre |
6 | damage to poorly constructed buildings and other structures within 10 km |
7 | major earthquake – causes serious damage up to 100 km (recently in Taiwan; Turkey; Kobe, Japan; and California) |
8 | great earthquake – great destruction, loss of life over several 100 km (1906 San Francisco; 1949 Queen Charlotte Islands) |
9 | rare great earthquake – major damage over a large region over 1000 km (1960 Chile; 1964 Alaska, and west coast of British Columbia; 1700 Washington, Oregon). |
Magnitude | Consequence |
---|---|
I | Not felt except by a very few under especially favourable conditions. |
II | Felt only by a few persons at rest, especially on upper floors of buildings. Delicately suspended objects may swing. |
III | Felt quite noticeably by persons indoors, especially on the upper floors of buildings. Many do not recognise it as an earthquake. Standing motorcars may rock slightly. Vibration similar to the passing of a truck. |
IV | Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably. |
V | Felt by nearly everyone; many awakened. Some dishes and windows broken. Unstable objects overturned. Pendulum clocks may stop. |
VI | Felt by all; many frightened and run outdoors, walk unsteadily. Windows, dishes, glassware broken; books fall off shelves; some heavy furniture moved or overturned; a few instances of fallen plaster. Damage slight. |
VII | Difficult to stand. Furniture broken, damage negligible in building of good design and construction: slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. Noticed by persons driving motorcars. |
VIII | Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture moved. |
IX | General panic. Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. |
X | Some well built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent greatly. |
XI | Few if any masonry structures remain standing. Bridges destroyed. Rails bent greatly. |
XII | Damage total. Lines of sight and level distorted. Objects thrown into the air. |
Date | Place | Railway | Description |
---|---|---|---|
1830, 15 Sept | Rainhill | L & M | Mr Huskisson run down |
1840, 7 Aug | Howden | H & S | casting fell from truck |
1840, 10 Nov | Bromsgrove | B & G | boiler explosion |
1846, 1 Jan | Tonbridge | SE | bridge collapsed |
1847, 24 May | Dee Bridge | C & H | bridge collapsed |
Southall | GW | broken wheel tyre, goods derailed | |
1849, 27 June | Hemerdon | SD (GW) | boiler explosion |
1850 | Wolverton | L & B | boiler explosion |
1860, 20 Feb | Tottenham | EC | derailment, broken tyre |
1861, 8 July | Easenhall | LNW | boiler explosion, Irish mail |
1862, 8 Nov | Westbourne Park | GW | boiler explosion |
1864, 5 May | Colne | Mid | boiler explosion |
1864, 9 May | Bishop's Road | GN | boiler explosion |
Leominster | S & H | boiler explosion | |
1870, 20 June | Newark | GN | collision, broken wagon axle |
1870, 26 Dec | Hatfield | GN | derailment, broken coach tyre |
1873, 3 Aug | Wigan | LNW | high-speed derailment on points |
1874, 24 Dec | Shipton-on-Cherwell | GW | derailment from broken coach tyre |
1879, 28 Dec | Tay Bridge | NB | bridge collapsed in gale |
Event | Approximate date |
---|---|
appointment of Bouch to E&N railway | 1849 |
first train ferry across Forth | 1850 |
bridge proposal put to NBR | 1854 |
act passed to approve Tay Bridge | July 1870 |
contract to build a bridge across the Tay | October 1872 |
survey of estuary | December 1872 |
start of site work | January 1873 |
Wormit foundry at south end of bridge built | February 1873 |
Hopkins, Gilkes & Co take over contract | July 1874 |
accident in caisson on pier 54; 6 die | August 1875 |
fall of main girder in storm | February 1877 |
bridge finished and first train passes over | September 1877 |
testing of bridge by Major-general Hutchinson | February 1878 |
first passenger train passes over completed bridge | May 1878 |
Queen Victoria rides over bridge; Bouch knighted with Bessemer | June 1878 |
bridge collapses in gale killing 75 people | December 1879 |
Board of Trade enquiry starts in Dundee | January 1880 |
Board of Trade enquiry to London to hear expert evidence | April 1880 |
final report to Parliament in London | June 1880 |
942. You are an engineer? – Yes 943. You live with your father, who is an ex-baillie of this town at Magdalen Green, do you not? – I do 944. I believe it is immediately to the north of the bowstring girder? – Yes 945. On Sunday evening, the 28th of December, do you remember that there was a great storm? – Yes 946. Did anything happen to your house or about your house which alarmed you? – Yes, in the first place I noticed the chandeliers of the room shaken; I noticed them move, and about 10 minutes past 7 the chimney cairns came down from the top of the house, about five of them 947. There were some friends at your house that night, I believe? – There were 948. And there was a suggestion made that you should look out and see the bridge, and what effect the gale would have upon it? – Yes … 951. You turned down the lights in your house and looked out? – Yes … 953. Tell me what you saw? – The first thing that caught my attention was the signal light, a little to the north of the high girders, it was flickering, I thought that the lamp of the signal was on fire. Then almost at that moment, or shortly afterwards, I saw two lights of the engine coming on to the bridge on the south side, and I followed it on closely to the big girders, where I saw a flashing of the lights; the light would be flashes as it were passing the spars. … 957. When it got to the high girders tell us what you saw? – At that time I thought I saw the lights shaken, but I suppose it would not be the case. Before it came to the big girders I thought I saw the lights shaken, but when it came to the big girders I saw as it were, flashes passing as it would be the spars of the big girders between me and the train. 958. You saw it coming on, but it was occasionally observed as it came past a high girder or spar? – Yes; then it suddenly disappeared about the third or fourth girder from the south side 959. At the time of its disappearance did you see any fire or light? – Not at the time, but about a second or two seconds afterwards there was a flash about two girders in advance of the train; then after that there was another light at about two girders, all coming towards the north; then there was a third flash. Taking it roughly, it would be two girders from the north side. 960. (The Commissioner): Will you say that over again; about two seconds after you had seen the light disappear what did you see? – There was a flash from about two girders in front of the train.
2893. On Sunday, the 28th of December, were you at home in the evening? – I was. 2894. Did anything happen to your chimney pots? – Yes, one of the cairns came rolling down. 2895. Did that bring you out of the house? – Yes. 2896. What kind of night was as regards light? – The moon came out occasionally; there were clouds passing. 2897. When the clouds were not obscuring the moon did you see the bridge? – Easily. 2898. At your house are you on the east or west side of the bridge? – I would be about 200 yards on the west side of the bridge. 2899. Can you see its whole length from the place where the curve ceases and the comparatively straight line begins to run across from the north side to the south? – Yes. 2900. The whole length? – Yes. 2901. When you came out on Sunday night to look at what happened to your house did you see the bridge? – I went round when I came out first, and one chimney cairn went. I had some glass at the back side of my house, and I then found it was blown out, and I put a stone locker or two in. I just put them in to keep the glass in. Some splits were coming down round about my ears, and I bolted. Before I went to the house I said I would go and see what the bridge was doing. I knew it was train time. I came straight across Blackness Road, a 20-foot-wide road, and there was a gate belonging to Mr Hunter and two posts, and I took one of them in my arm, and put myself in that position (describing) and I kept my eye on the north end of the bridge not further than that (describing). I was in that position for a second or two, and then I saw, as I thought then, and as I think yet, something about the first or second girder passing into the river, as it appeared to my eye. I looked immediately behind, and then another fell, and I saw a light, as it was just a mere blink. 2902. You saw as you believed then, and believe now, two distinct parts of the bridge fall into the river; on what side? – On the east side. 2903. Those were the parts of the bridge to the south, the beginning of the high part of it? – Exactly. 2904. Did the first part that you saw fall far away immediately from the place where the high part began? – As near as I could guess in my mind it would have been about the first girder or the second girder upon the high girders. I just immediately got nervous at once, and I rubbed my eye and in a second I saw another movement at that time, and I saw a light. 2905. What light was it? – I could not tell. 2906. Do you mean on the bridge? – Yes, on the southernmost part of the high girders, or near it. 2907. Further south than where you saw the pieces of fire? – Decidedly, just a blinking light; just a second. 2908. Was it a white light or a coloured light? – I would not speak upon the light. It was just a blink that I got altogether, just a sort of blink. I cannot speak as to the colour; it was a clear light. 2909. Did you see the light before the girder fell? – No. 2910. The first thing that struck you in reference to this was the fall of one piece of a high girder of the bridge? – Yes. 2911. Then there fell a second bit, and then a light? – No; what I saw first, as I thought then, and think still, was a part of the second girder going off, and then in a second or two I saw another lump going, and just at the time that I saw the southernmost part of the girder, I saw a blink of light, and the blink of light had cleared away. The moon was shining as clear as could be on the river, and I saw the large piers from end to end nearest to the girders.
4916. Did the passing of the trains have any effect on the bridge? – Very much. 4917. What was its effects? – Oscillation, I would term it first, side to side movement. 4918. Was there any other movement? – Yes. 4919. What? – Vertical movement. 4920. With regard to the oscillation or lateral movement, was that severe? – Yes, it was very severe. … 4940. What effect did you see the motion thus produced have on anything that was placed on the bridge? – I have seen the spilling of a pail of water a long while before the train approached. You could feel the oscillation half a mile off. 4941. But you have seen a pail of water upset? – No, not upset, only the water oscillating and spilling over the side. 4942. Had it any effect on the paint-pots? – We always secured them with every passing train. … 4953. Were both those movements greatest inside or outside of the high girders? – Inside, about the centre.
5383. When the two movements got combined was there a severe movement of the particular place at which you were standing? – Yes, it would make an unaccustomed man feel a little strange. 5384. Not steady on his legs you mean? – Yes, that is the feeling; you felt the under part shaking under you. 5385. And you felt it shaking from side to side? – Yes. 5386. At the place where the movement was greatest, at the joining of the high and low girders, was it enough to produce alarm? – Well, I considered it weak there. 5387. What was weak? – That it was alarming. 5388. What was alarming? – The side movement. 5389. What did you think was weak at that place? – Well, I thought from the side movement that the columns must have given way. 5390. You mean that the bridge was weak? – Yes, exactly.
5428a. (Colonel Yolland) At the time when you felt the side motion most you were over a pier, were you not, where the high girders and low girders meet? – Yes. 5429. Did you at that time look along the piers either to the north or the south so as to notice whether you were sensibly deflected to the east or to the west? – Yes, if you looked along the side of the girders. 5430. Did you form any opinion at the time to what extent the deflection took place? – I would say it was considerable but I could not say exactly in inches what it was. 5431. Did you form any opinion at the time? – Yes. 5432. What was it? – I would say from two to three inches. 5433. You formed an opinion, but you cannot say what it is now? – From two to three inches. 5434. Would that two to three inches be the extreme of the motion eastwards to the motion westwards, or was it half that quantity? – Well, I could not say; it was difficult to measure, but the motion was distinct and large. 5435 (Mr Trayner) And visible? – Yes.
11,404. Leaving the foundations, let us go up a little bit, Did you discover whether any of the ironwork of the bridge was getting unstable or loose? – In taking those soundings that I have spoken of, I noticed or heard a chattering of the bars. 11,405. You heard them moving or shaking? – Yes. 11,406. Was it in the lowest tier of bars nearest the stone work that you found the bars chattering? – Generally. as far as my remembrance goes, it was something like the third or fourth tier down. I cannot positively say: Such a thing might have taken place in the second tier from the top to the bottom. 11,407. Speaking from the best of your recollection, can you say whereabouts in any of those piers or columns, not the supports, you first observed that any of those bars were too loose? – I cannot speak from recollection. 11,408. Were those loose bars within the high girders or without the high girders, or both? – They were both. 11,409. Did you examine the bars in order to see what was the matter with them, or whether they needed any repairs? – Yes. 11,410. Tell me what it was you found to be wrong with the bars on your examination of them? – I do not know whether I can explain it to you. I found that the cotters in coming together had got a little loose – there was not a sufficient width to get a good grip, and they had got a little loose. … 11,416. How loose were they? – Had they been loose of course they would have been found at sight. We had to go and find out where this chattering motion took place, and then through the cotters to see which was loose, which showed me that they must have been just about as tight as this. In sounding them with a hammer we found that they were not tightened up sufficiently. In driving them home we found that they were scarcely wide enough to get a tight grip. … 11,419. Did you find that you could drive them home tight easily with the hammer? – I found out that I could drive them home tight with the hammer on account that they were not wide enough in those places where I found them. 11,420. Then the cotters were too small for the slot-holes you think? – Yes, in those places. 11,421. No amount of driving would have made them catch each side of the slot-hole so as to make them tight? – Not properly. 11,422. Would any amount of driving have made them tight in the slot-hole in the first instance? – Not those cotters. 11,423. Then it comes to this – that from the outset those cotters were too small for those particular slots? – That is my opinion. 11,424. It was not careful work you think? – I should not think so. 11,425. Did you report what you had found to anybody? – No. 11,426. Why? – Because I thought I could remedy it. … 11,431. What was the use of those cotters? – To tighten up the bracings. 11,432. What was the purpose of having the bracings tight? – To make the bridge stable. … 11,438. But you thought it a sufficiently important thing to induce you at once to repair it? – Where I heard a noise from the jingling of the bars I tried to remedy it.
change in diagonal distance due to backlash = 0.75 inch.
1.414 × 0.75 inch = 1.06 inches.
sway at top = 7 × 1.06 inches ≈ 7.5 inches.
Casting defects | Number | Where found | Reference | |
---|---|---|---|---|
1 | column wall thickness variations | 2 | P6T?C6, P5T?C4 | 14,169 |
2 | cold shuts, with poor fusion around the lug hole | 1 or 2 | ? | 12,599 |
3 | burnt-in lugs | possible where lug break extends to column | ? | 14,187 |
4 | blow holes from gas bubbles often filled with rosin and iron filings (beaumont's egg) | very extensive | e.g. P28, T?C3 | 12,599 |
5 | longitudinal ribs on column walls where moulds not mating correctly | many columns | e.g. P4 | 12,590 |
6 | longitudinal cracks on columns | 4 | P73, P76, P10 | 12,923 11,656 |
7 | slag inclusions | very extensive | ? | 12,599 12,604 |
8 | ‘sluggish’ metal | all (?) | – | 12,602 |
9 | flanges not flat, so column joints poorly formed | most columns | – | 12,577 |
Fitment flaw | Number | Where found | Reference | |
---|---|---|---|---|
1 | enlarged, damaged bolt holes formed during erection of piers | many | e.g. P2 | 14,341 |
2 | quadrants for horizontal tie rods poorly fitted; metal only 0.5 inch thick | most | – | 14,593 12,638 |
3 | four bolts attaching L girders to pier heads, rather than eight | 1 | P2 | 14,609 12,651 |
4 | extra set of holes drilled in flange | 1 | P1, T1, C3 | 14,718 |
5 | poor adhesion between cement and masonry at pier base | many piers | e.g. P9, C6 | 12,533 |
6 | base bolts poorly embedded | many piers | ? | 12,565 |
7 | poor quality of cement in some columns | a few columns (?) | ?P6+ | 12,876 |
8 | cement in joint | a few columns | P5, 6 ,C1 | 12,694 |
9 | gibs/cotters poor fit: cotter compressed when tie bar strained | 2 cotters/gib only, 2 gibs/cotter OK | – | 14,374 12,619 |
10 | packing pieces used in tie bars by noble | 12 picked up from pier bases | e.g. P1, T1/2, C5/6, C5/3, 4 | 12,676 |
Design defects | Number | Where found | Reference | |
---|---|---|---|---|
1 | lugs of low strength | all lugs | – | 14,193 |
2 | bolt holes with conical sections, so bolts act only against a short length of the hole | all bolt holes | – | 12,619 |
3 | 1.125 inch bolts for tie bars fitted to 1.25 inch bolt hole in lugs, flanges | all joints | – | 12,580 |
4 | strut not abutting column wall | all struts | – | 14,669 12,608 |
5 | strut bolts difficult to tighten | all struts | – | 14,553 |
6 | no spigot on column ends, so columns can move laterally | some columns | P1, T1/2, C3/4 | 14,718 |
7 | L girders not continuous across pier head | all | – | 12,655 |
8 | pier base too small | all | – | 12,712 |
9 | batter on 18 inch columns too low | all | – | 12,717 |
10 | girders resting only on piers | most | P1, 2, 4–6, 8–10, 12 | 12,665 |
11 | girder not centred on piers; deviation at joint between high and low girders | 1 | P28 | 12,703 |
15,001. (Mr Trayner) Did you notice that on some of the piers the lower tier of columns had been forced to the westward? – I did. 15,002. The great mass of the superstructure we know went over to the east? – Yes 15,003. In your opinion what led to the forcing of these columns westward? – At no. 5 pier the eastern set of columns is underneath the eastern girder crushed up. 15,004. The eastern set of columns is under the eastern girder? – Yes, as it lies on its side, or as it did lie on its side at the bottom. The western columns are lying over the top of the western girder, and that renders it absolutely clear to my mind that the three eastern columns gave way first, that the structure went over sufficiently quickly, and that then the three outer columns or western columns fell over on to the top of the girder, and so they are found. … 15,007. (Mr Barlow) Showing that the eastern and western parts separated from each other? – That they separated from each other. I think the probability is that the separation would not have taken place had the angle girders or L-girders at the top been connected together so as to have brought the whole six columns in unison. … 15,015. (Mr Barlow) If those columns had been strongly cross-braced, strongly fitted, and strongly held down by holding-down bolts, do you think the bridge would have been sufficient? – I believe that it would be standing at the present moment; it is a question of the strength of the bracing of course.
15,798. (The Commissioner) Mr Noble was asked ‘Did you discover whether any of the ironwork of the bridge was getting unstable or loose?’ His answer was, ‘In taking these soundings that I have spoken of, I noticed or heard a chattering of the bars’. During the five months you were there, and during the three months subsequent to the inspection, you observed and you heard no chattering at all? – No, unless it was with the wind; the wind would chatter those bars, though they were as tight as fiddle strings. 15,799. If they were as tight as fiddle strings, they would not be required to be tightened up? – No. 15,800. The chattering would have been of no importance at all? – No, unless they were really loose.
15,874. I will ask you a question which was put by Court to the last witness. You have heard the expression used in this room that there was a chattering of the bars together, or some sound coming from the piers resembling rattling? – Yes. 15,875. Were trains passing over the bridge during the last two months? – Yes, ballast trains. 15,876. How frequently? – As frequently, I think as four trains a day or five trains a day. 15,877. Did you ever hear during the time, before you left the bridge, anything that you would understand by a chattering of any parts of the ironwork? – Yes. 15,878. When was that? – Before the bars were perfectly tightened.
15,942. You said that before you tightened it up you did hear a chattering of the ties, did you not? – Yes. 15,943. But when you left it in December you heard none? – I never heard any of these bars vibrating, or chattering, as it is called, after they were properly tightened. I have been down in different parts of the pier when trains have been passing, and my attention was particularly called to that, because I heard them chattering on a previous occasion.
The lateral oscillation … was very slight, and the structure altogether showed great stiffness.
… with full regard to all the strains likely to come upon them, the calculations have not been preserved in such a form as to be available for our present purpose ….
… seeing that the strains are borne by the concurrent resistances of many bars in different positions.
19,143. Take the hypothesis that is put to you, that these tie bars were giving to the extent of a quarter of an inch, do you say that would add to the stability of the structure, or that it would detract from the stability of the structure? – Of course you mean this and the one opposite (pointing to the model)? It would add to the stability of the structure. (Mr Bidder) Do you mean giving by extension, or by bolt bending? (Mr Trayner) I mean giving by extension. (Mr Stewart) I still hold to the view I have expressed. If Sir Thomas Bouch could have put in some kind of spring that would have allowed a yielding of a quarter of an inch it would have added to the strength of the structure. It would have been very difficult to do. 19,144. It would have been something like building a castle in the air? – Perhaps. … 19,156. When these bars chattered in the way we have heard described, it was again a piece of unnecessary work on Mr Noble's part to fill them up with packing pieces? – You have already asked me that question. I do not know that it is always wise to increase the stability of a bridge by looseness, I think it wiser to pack it up. It is difficult to answer that question.
15,033. (Mr Trayner) You heard the suggestion that the train had gone off the rails and knocked over the bridge; have you formed any opinion as to whether the train had gone off the rails, and by so doing had contributed in any way to the result? – I think it did not from all I saw. I do not believe the train left the rails.
There is no evidence to show that there has been any movement or settlement in the foundations of the piers; The wrought iron was of fair quality; The cast iron was also fairly good, though sluggish on melting; The girders were fairly proportioned for the work they had to do; The iron columns, though sufficient to support the vertical weight of the girders and trains, were owing to the weakness of the cross-bracing and its fastenings, unfit to resist the lateral pressure of the wind; The imperfections in the work turned out at the Wormit foundry were due in great part to want of proper supervision; The supervision of the bridge after its completion was unsatisfactory; If by loosening of the tie bars the columns got out of shape, the mere introduction of packing pieces between the gibs and the cotters would not bring them back to their positions; Trains were frequently run through the high girders at much higher speeds than 25 mph; The fall of the bridge was probably due to the giving way of the cross-bracing and its fastenings; The imperfections in the columns might also have contributed to the same result.
… we have to state that there is no requirement issued by the Board of Trade respecting wind pressure, and there does not appear to be any understood rule in the engineering profession regarding wind pressure in railway structures; and we therefore recommend that the Board of Trade should take some steps as may be necessary for the establishment of rules for that purpose.
… gain the confidence of the public and enjoy a reputation of being not only the biggest and strongest, but also the stiffest in the world.