1
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so what I've got here is a steel bar and

2
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to wait about ten pounds each I think

3
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and they're attached to these columns

4
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here and they're actually nails in a

5
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square around on both sides well I'm

6
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gonna do is heat up the bar in the

7
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middle here and what I anticipate

8
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happening is perhaps a slight expansion

9
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you might not be noticeable you might

10
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see the bar expand and you probably see

11
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some paint burning off and then you

12
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should see it's safe now what I've tried

13
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to explain here is why a sagging beam

14
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pulls in the column to do that and right

15
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now the beam is step so this weight is

16
00:00:51,110 --> 00:00:48,239
been transferred straight down here when

17
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the beam bends the beam is no longer

18
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stiff so it can't resist anything

19
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pulling or pushing in from the sides the

20
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angle of this will may be the fourth go

21
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down that way we should make the two

22
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columns go in from the side so let's see

23
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what happens I've got two torches I'm

24
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just gonna use my smaller one to start

25
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off with anything needs it I'm gonna

26
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bring my a bigger one into play so let's

27
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give it a go before I show you that I'm

28
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gonna do a slightly different

29
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demonstration here I've got two columns

30
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and I've got two lengths of identical

31
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chain right here and another one here

32
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the difference between them is that this

33
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length of chain this has been welded so

34
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it's stiff and this is just a regular

35
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piece of chain so why don't they do

36
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first is take the stiff piece of chain

37
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which would be the floor truss or a

38
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regular floor beam and attach it to

39
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these two columns and you'll see it does

40
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a nice job of acting like a floor I can

41
00:02:01,969 --> 00:01:57,780
even put on some load on it I've learned

42
00:02:04,520 --> 00:02:01,979
walking around any X just fine but say

43
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this walk there's more trust this beam

44
00:02:07,120 --> 00:02:05,600
or whatever

45
00:02:09,699 --> 00:02:07,130
to lose its structural integrity and

46
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start to Sag that's gonna be represented

47
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by this of course is a very extreme

48
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example it's lost all of its integrity

49
00:02:17,949 --> 00:02:16,400
he demonstrates the principle of what

50
00:02:19,750 --> 00:02:17,959
happens when something is sagging and

51
00:02:21,790 --> 00:02:19,760
it's attached to something that was

52
00:02:23,229 --> 00:02:21,800
previously stiff now one thing to know

53
00:02:25,750 --> 00:02:23,239
to say this is the core of the building

54
00:02:28,780 --> 00:02:25,760
goes to the outside any exterior loads

55
00:02:31,030 --> 00:02:28,790
actually get transmitted through the

56
00:02:33,250 --> 00:02:31,040
floor because it's depth so this will

57
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resist being pushed in from the side so

58
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any generation of this column will be

59
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resisted by the floors as well as laws

60
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holding up what underneath them so let

61
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me take this this floor off and replace

62
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it with a failed four and move them out

63
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so they're straight and straight away

64
00:03:00,699 --> 00:02:57,709
you can see that it does it just pulling

65
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in that it's not stable at all if I pull

66
00:03:04,930 --> 00:03:03,019
it so it's perfectly straight straight

67
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away as soon as it starts to sag a

68
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little bit it's calling in the reason of

69
00:03:13,030 --> 00:03:11,299
course is that when you have something

70
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suspended between two points you have

71
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this catenary action which means it's

72
00:03:19,509 --> 00:03:17,690
very very difficult when when it's

73
00:03:26,039 --> 00:03:19,519
straight pretty much all of the force is

74
00:03:32,289 --> 00:03:26,049
going this way if member is not stiff so

75
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this is what happens this law is just

76
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[Music]

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so there you go the bar failed in the