0
00:00:04,276 --> 00:00:07,886
>> During Telford's time, James Watt was a leading critic of bridges,

1
00:00:08,476 --> 00:00:11,696
and he critiques Telford's design of a London bridge proposal.

2
00:00:12,606 --> 00:00:15,506
And Telford takes this critique very seriously.

3
00:00:16,026 --> 00:00:19,996
Telford is then asked to write an article on Bridges for The Edinburgh Encyclopedia

4
00:00:20,556 --> 00:00:25,326
and when he writes this he critiques the Iron Bridge and others including his own,

5
00:00:25,876 --> 00:00:29,396
and in this critique he uses the ideals of structural art,

6
00:00:29,676 --> 00:00:32,456
although again, he's not using this terminology.

7
00:00:32,916 --> 00:00:37,346
In this course we're going to critique bridges using the measures of structural art.

8
00:00:37,796 --> 00:00:40,356
We're going to look at it from the scientific perspective,

9
00:00:40,756 --> 00:00:43,236
looking at the materials, meaning efficiency.

10
00:00:44,066 --> 00:00:48,246
From the social perspective, minimum cost, meaning economy,

11
00:00:48,686 --> 00:00:52,776
and from the symbolic perspective where we have maximum personal expression

12
00:00:53,216 --> 00:00:54,546
where we measure the elegance.

13
00:00:55,366 --> 00:00:57,686
We call these critiques, when we compare one bridge

14
00:00:57,686 --> 00:01:00,436
to another, a comparative critical analysis.

15
00:01:01,136 --> 00:01:04,816
So, from the scientific point of view we're going to compare the form and materials.

16
00:01:05,226 --> 00:01:06,496
Is it a suspension bridge?

17
00:01:06,526 --> 00:01:07,406
Is it an arch?

18
00:01:07,486 --> 00:01:08,286
Is it steel?

19
00:01:08,326 --> 00:01:09,126
Is it concrete?

20
00:01:09,916 --> 00:01:13,016
From the social point of view we're going to look at costs and utility.

21
00:01:13,016 --> 00:01:16,346
What were the construction costs of these two comparisons?

22
00:01:16,346 --> 00:01:18,966
And, we're going to look at not only the construction costs,

23
00:01:19,056 --> 00:01:20,646
but the maintenance cost as well.

24
00:01:21,236 --> 00:01:25,036
And, from the symbolic point of view we look at the appearance and the meaning.

25
00:01:25,366 --> 00:01:27,996
We look at the form, the details, and the ideas.

26
00:01:29,236 --> 00:01:33,936
So let's do a comparative critical analysis using the Iron Bridge that we already looked at

27
00:01:34,406 --> 00:01:39,866
and The Craigellachie Bridge, one of Thomas Telford's later arch bridges made of iron.

28
00:01:40,866 --> 00:01:45,126
From the efficiency point of view, the Iron Bridge is a semi-circular form.

29
00:01:45,896 --> 00:01:50,356
The Craigellachie Bridge is "parabolic" and I put that in quotes

30
00:01:50,506 --> 00:01:54,936
because it's not really truly parabolic, it's really a very flat circle.

31
00:01:54,936 --> 00:01:56,726
It's a small slice of a circle.

32
00:01:57,926 --> 00:02:02,576
The Iron Bridge is 100 foot in span and the Craigellachie is 150 foot in span,

33
00:02:03,436 --> 00:02:05,416
and despite being 50 percent longer,

34
00:02:05,586 --> 00:02:09,416
the Craigellachie has one third less material than the Iron Bridge.

35
00:02:09,476 --> 00:02:14,446
So, from that point of view, the Craigellachie Bridge is more efficient.

36
00:02:15,176 --> 00:02:19,186
From the economy point of view we don't have numbers, but we could look at it

37
00:02:19,286 --> 00:02:21,926
and make guesses as to how it was constructed.

38
00:02:22,536 --> 00:02:27,436
So, the Iron Bridge we see it's constructed of many different parts with many connections

39
00:02:28,076 --> 00:02:32,216
versus the Craigellachie Bridge we see it is made in mass production.

40
00:02:33,056 --> 00:02:37,126
The arch, you can see, it's separated in to seven segments.

41
00:02:37,336 --> 00:02:40,526
There's little vertical elements that show you where those connections

42
00:02:40,666 --> 00:02:43,826
of the segments are made, so it is mass produced,

43
00:02:43,946 --> 00:02:47,126
and we can assume that it was more economical to build.

44
00:02:48,096 --> 00:02:54,206
And, from the elegance point of view, we see the semi-circular for the Iron Bridge versus again,

45
00:02:54,206 --> 00:02:56,416
"parabolic" for the Craigellachie.

46
00:02:57,016 --> 00:03:01,096
Both are arch bridges, so both are carrying the loads in compression.

47
00:03:02,716 --> 00:03:07,166
The shape of the Iron Bridge is what we define as mutilated, meaning if you look

48
00:03:07,166 --> 00:03:12,446
at those arches, the lower arch goes completely through from one abutment

49
00:03:12,576 --> 00:03:17,616
to the other uninterrupted, but the upper two arches are interrupted by the deck,

50
00:03:17,866 --> 00:03:20,606
so those upper two arches are what we call mutilated

51
00:03:21,336 --> 00:03:24,596
versus the Craigellachie Bridge has the arch that's unbroken.

52
00:03:25,036 --> 00:03:28,526
It goes from one abutment to the other uninterrupted by the deck.

53
00:03:29,196 --> 00:03:32,046
The spandrel is what connects the deck to the arch,

54
00:03:32,396 --> 00:03:35,136
and in the Iron Bridge we see that they are circles.

55
00:03:35,416 --> 00:03:40,536
They are there for essentially decoration, whereas for the Craigellachie we have triangles,

56
00:03:40,976 --> 00:03:42,836
and those spandrel's are there for support.

57
00:03:44,596 --> 00:03:49,226
Even though in this analysis we see that the Craigellachie Bridge essentially, say, wins

58
00:03:49,676 --> 00:03:53,736
in the context of measuring for structural art, it doesn't destroy the idea

59
00:03:53,736 --> 00:03:55,636
that the Iron Bridge is a great work,

60
00:03:56,136 --> 00:04:00,236
because it was so innovative using this material iron for the first time.

61
00:04:00,616 --> 00:04:02,726
It is a very important structural work.

62
00:04:03,856 --> 00:04:08,366
Thomas Telford goes on to become the President of the first formal engineering society,

63
00:04:08,446 --> 00:04:13,666
The Institution of Civil Engineers which is still in existence today in Great Britain.

64
00:04:14,406 --> 00:04:19,176
He is the leading engineer of the modern world and he also considered himself an artist.

65
00:04:20,386 --> 00:04:23,286
Telford is the first modern engineer to show that a concern

66
00:04:23,286 --> 00:04:27,556
for aesthetic does not compromise the technical quality that can improve it,

67
00:04:28,456 --> 00:04:32,386
and the people that we're going to talk about are the most accomplished and found engineers.

68
00:04:32,786 --> 00:04:35,176
Technically competent, but also artists.

69
00:04:35,476 --> 00:04:37,976
That is one of the themes that runs through this course.