Bolted Tension Connections. Limit State: Yield or Ultimate?? Yield: 36 ksi (strain = 0.0013)
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Bolted Tension Connections
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Transcript of Bolted Tension Connections. Limit State: Yield or Ultimate?? Yield: 36 ksi (strain = 0.0013)
Bolted Tension Connections
Limit State: Yield or Ultimate??
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.40
10
20
30
40
50
60Stress-Strain for A36 Steel in Tension
Strain (in/in)
Stre
ss (k
si)
Ultimate: 58 ksi (strain = 0.32)
Yield: 36 ksi (strain = 0.0013)
Limit State: Yield or Ultimate??
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
Limit State: Yield or Ultimate??
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322” long brace
mmmm….. Maybe we should not let it yield
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322” long brace
mmmm….. Maybe we should not let it yield
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322” long brace
If we limit the stress to less than yield, then….
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322” long brace
If we limit the stress to less than yield, then….
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322.4” long brace
The brace would not extend more than 0.4” (do the math: eL = 0.4”)
If we limit the stress to less than yield, then….
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322.4” long brace
The brace would not extend more than 0.4” (do the math: eL = 0.4”)And the column would be leaning by no more Than 0.45” (do the math: Pythagoran
Then again…. Yield is no where near the maximum the steel can take.
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322” long brace
Then again…. Yield is nowhere near the maximum stress the steel can take.
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322” long brace
I mean…. Even if it yields at 36 ksi, it doesn’t break, right?
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322” long brace
I mean…. Even if it yields at 36 ksi, it doesn’t break, right?
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322” long brace
It seems like yielding is no big deal
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322” long brace
It doesn’t break at 36 ksi (yield)Why not just say that 58 ksi (ultimate) is the limit??
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322” long brace
It doesn’t break at 36 ksi (yield)Why not just say that 58 ksi (ultimate) is the limit??
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322” long brace
If we limit the stress on the brace to Anything Less than Ultimate (58 ksi), then…
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
322” long brace
If we limit the stress on the brace to Anything Less than Ultimate (58 ksi), then…
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
425” long brace
The brace would not extend more than 103” (do the math: eL = 103”)
132”
If we limit the stress on the brace to Anything Less than Ultimate (58 ksi), then…
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
425” long brace
The brace would not extend more than 103” (do the math: eL = 103”)And the column would be leaning by about 132”(do the math: its fun, complicated)
132”
Now, we’re in the world of 2nd order effects (the Statics are changed because of the huge change in
geometry
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
425” long brace
The brace would not extend more than 103” (do the math: eL = 103”)And the column would be leaning by about 132”(do the math: its fun, complicated)
132”
Gravity loads will make it collapse
0 0.1 0.2 0.3 0.40
102030405060
Strain (in/in)
Stre
ss (k
si)
12’
24’
P
425” long brace
The brace would not extend more than 103” (do the math: eL = 103”)And the column would be leaning by about 132”(do the math: its fun, complicated)
132”
So….We DO NOT WANT THE MEMBER TO YIELD
YIELD IS THE LIMIT FOR THE MEMBER
But…The connection is different
Around holes, a little bit of yielding is fine (holes are tiny).
