Conventional Shear Plate Connection AISC 3

[Veer007]

Hey Guys,
This may sound silly but if you could help me I would be happy.
I have seen a table from AISC which shows the maximum thickness of the shear plate. assume 1" bolt
case 1:
Bolt numbers: 2 to 5 e=a/2, where e=3 1/2" max
If the connection holes to be SSLT, no limit to the max thickness of shear plate, so Can I use a 5/8" thick plate?
If the connection holes to be STD, Plate thick to be d/2+1/16"=9/16", so can't I use 5/8" as plate thick?
case 2:
Bolt numbers: 6 to 12 e=a/2(SSLT),e=a(STD) where e=3 1/2" max
If the connection holes to be SSLT, Plate thick to be d/2+1/16"=9/16", so can't I use 5/8" as plate thick?
If the connection holes to be STD, Plate thick to be d/2-1/16"=7/16", so can't I use 5/8" as plate thick?

Concludes that, whether can I use more thickness of shear plate than specified in table 10-9 or not?

Thanks in advance!!

 

[strucbells]

Single shear plate connection procedures assume some degree of rotational ability and ductility which is accomplished through bolt "plowing" through either the plate or the web of the beam prior to the bolts failing in shear. Basically the holes will elongate a bit horizontally.

The SSLT holes inherently provide a bit of rotational capacity without plowing occurring which is why they don't have a max plate/web thickness for the fewer bolt rows.

Good explanation here:

https://www.aisc.org/globalassets/modern-steel/archives/2006/10/2006v10_simpler_shear.pdf

 

[strucbells]

Also, do you have the actual steel manual or just this screenshot? There is more information prior to the tables that should give you everything you need to know.

 

[Veer007]

I have full set of AISC 13th edition

Thanks in advance!!

 

[Veer007]

So, the bolts try to make like a SSLT from an STD hole, will elongate STD hole a little bit, so we need more thickness d/2+1/16? right?

Thanks in advance!!

 

[dauwerda]

The idea is to limit the thickness of the the shear plate for a standard hole so that the plate will locally yield, allowing the connection to behave as pinned as designed. If your plate is too thick, local yielding won't happen and your connection will behave more like a semi-rigid connection, which can cause excess load to be dumped into members that aren't designed for it. A slotted hole has an allowance for movement without the need for the plate to yield, therefore it does not have a maximum thickness.

 

[r13]

I am getting a little lost here, as this is something new to me. In general, failure initiated from beam is preferred over the connection. Can anybody provide an example that semi-rigid connection will cause failure of a beam designed with pinned ends, and sized by the maximum positive moment?

 

[dauwerda]

retired13, my comment above was not pertaining to the beam - I was thinking about the member the beam is connecting to (whether it be another beam now seeing more torsion or a column seeing more moment, etc).
At the end of the day, the max plate thickness requirement is to help ensure the connection performs more closely to the design assumptions than it otherwise would.

 

[r13]

dauwerda,

I was not doubting your explanation, just thinking about the philosophy of AISC for setting this limit, and trying to see/find real examples/concerns that I might not aware of.

I guess in the over load situation, due to the unaccounted moment capacity, the beam will not deflect as much as simply supported, without ample warning, the bolts might fail before everything else. Under such condition, the yield of the connection plate signals warning for imminent failure, so it is desirable, thus it is essential to set limit on plate rigidity.

 

[PROYECTOR]

Concludes that, whether can I use more thickness of shear plate than specified in table 10-9 or not?

In single-plate connections, the geometry and thickness of the plate are configured so that the plate will yield, bolt group will rotate, and/or the bolt holes will elongate (bolt plowing) to accommodates the beam end rotation. Note that the Table 10-9 specify the limit for "tp or tw". So, you can specify a thicker plate as long as the beam web thickness satisfy the Table 10-9 limits.

Alternatively, the Table 10-9 limits can be ignored if the connection is designed using the Extended Single Plate design procedure, where a maximum plate thickness is determined such that the flexural strength of the plate is less than or equal to the bolt group flexural strength. In this case, the connection plate act as a fuse to protect the bolts from shear rupture in order to achieve the expected rotational ductility.

It should be noted that the geometrical limitations and design procedures of the AISC Manual should not be viewed as code requirements. The Manual contains only guidelines and recommendations. However, such recommendations are often a way to satisfy requirements contained in the Specification. In this case, the limitations in Table 10-9 and the design procedure for Extended Single Plate connections are intended to meet the requirements of B3.6a and J1.2 of the AISC Specification.

 

[Veer007]

So, we must satisfy the table 10-9, we don't use more thickness of shear tab as it doesn't allow the elongation of holes unless it's an extended shear plate connection, right?

Thanks in advance!!

 

[Veer007]

If a connection acting as semi-rigid than pinned connection, Is it not good for shear? Coz if a beam has axial force, it's not goodto provide short slot in connection bolts, Am i wrong?

Thanks in advance!!

 

[Veer007]

What if beam has 1/2" web thick, don't I use 3/4"Ø bolt, which is likely having 3/8"+1/16"=7/16" as plate thick max for STD holes when bolt row is 5 No's.

Thanks in advance!!

 

[Veer007]

??

Thanks in advance!!

 

[r13]

Here is PROYECTOR's comment made earlier, which is extremely well said:

It should be noted that the geometrical limitations and design procedures of the AISC Manual should not be viewed as code requirements. The Manual contains only guidelines and recommendations. However, such recommendations are often a way to satisfy requirements contained in the Specification. In this case, the limitations in Table 10-9 and the design procedure for Extended Single Plate connections are intended to meet the requirements of B3.6a and J1.2 of the AISC Specification.