Steel Walkway Connection 4

[BONILL]

Steel walkway spans between to portions of a concrete structure which I want to act indpendently of one another for lateral loads. The connection attached below is a regular shear connection. I need a connection that provides gravity restraint but that would allow movement in the direction normal to the plane.

 

[msquared48]

You can't use horizontally slotted holes on one end of the beam?

How much longitudinal movement do you need to design for?

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[Teguci]

What about lateral along the plane?

I'd suggest using a ledge with a slide bearing detail and a keeper angle to hold the steel beam perpendicular (assuming you don't care about lateral parallel with the concrete beam).

 

[msquared48]

OK. Got it... finally.

Slotted holes would still work with a double angle connection at the end of the beam. Just orient the slots normal to the plane of the walkway, and place the slots at the connection to the building.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[connectegr]

Don't use "poor-man's expansion joint", horizontal slots in a typical double-angle or double plate shear connection. Slots can bind and induce axial load into connection and support. Also structural connection requires at least snug-tight installation, which will also resist movement.

I would recommend a slide bearing, seat connection. Restrictors can used to control direction and distance of movement.

http://www.FerrellEngineering.com

 

[hokie66]

Agree with connectegr. This should be a guided slide bearing on one end of the bridge. This type connection has been discussed here before, so searching should find some recommendations.

Avoid slotted holes. Research the Pittsburgh Convention Center.

 

[BONILL]

See attached detail below.

It shows embed plate in concrete beam and a second steel plate with slotted holes normal to the steel beam to allow for movement out of plane. The bolt holes in the beam are slotted parallel to the steel beam to allow in plane movement. Between the two plates I'm thinking of some neoprene material?

msquared48 is this more or less what you were explaining?

connectegr,hokie66 where could I find a typical guided slide bearing detail?

 

[connectegr]

All I can say is, good luck. A single plate slide connection may be the worst case. The bolts are binding initially from the couple force. Also single plate connection to embed is not flexible and transfers shear and moment to the embed. The binding of the connection will add an axial force to all the components. In order to move horizontally the horizontal forces must exceed the snug-tight clamping force of the bolts, the bearing forces of the bolts on the surface of the holes (bolt plowing), and friction between the faying surfaces.

good luck!

http://www.FerrellEngineering.com

 

[connectegr]

Bonill
I don't know where you are located, but RCSC does not allow a non-steel filler in structural connections. This would exclude the use of a teflon fill. And as I mentioned above, RCSC also require at minimum a snug-tight bolt installation.

As Hokie mentioned, the Pittsburg Convention Center is a recent example of the slide connections you are proposing. Most of their connections were double angles with the outstanding legs welded to embeds or columns. When the bolts failed to slip, the axial load broke the welds from the supports. One significant failure dropped a semi truck through the floor. But, many locations showed cracks and other distortions after only a few years of service. Nearly every similar condition was retrofit with stiffened seats and slide bearing pads.

http://www.FerrellEngineering.com

 

[paddingtongreen]

Set the connection above or below the walkway, hang or strut the walkway with braces between the strut/hangers. Use single barrel bolts top and bottom of the hanger/strut.

I've used this on refinery structures where I wasn't permitted to weld to the vessels. A long time ago, for sure but i didn't get any negative feedback.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[Teguci]

Slots might be OK for long term shrinkage where some axial load transfer is allowed for (pending that the connection is protected). However, for wind or seismic the slots will not work.

Attached is a slide bearing arrangement with welded studs for keepers and a teflon on stainless steel plate arrangement.

 

[BONILL]

I read the article about the Pittsburgh Convention Center, and my situation is earily similar to theirs. I'm thinking of using the same solution used for the retrofit of their connections:

A stiffened steel seat with a bearing pad.

For that I would have to reduce the section of the steel beam at the support and remove the plate and bolts. I am wondering if a neoprene bearing pad would be adequate?

Thanks again.

 

[Teguci]

I use neoprene bearing pads for situations where I don't want slip.

 

[hokie66]

For design of the bearing, define your required movements and consult with a bearing manufacturer. The teflon on stainless steel bearings work well. The bearing manufacturers have options allowing for restraint in the transverse direction. Do you need to allow for differential movement in all directions?

 

[BONILL]

It is much easier where I am located to use neoprene bearing pads. I'm just trying to find out if this would be adequate for the required movements?

 

[BONILL]

Teguci,

In your detail what are the welded studs exactly for?
Can I replace the teflon for a neoprene bearing pad?

 

[slickdeals]

The headed studs are used to prevent it from sliding out perpendicular to the span of the member.

I have used 2 clip angles welded to the support and free against the web as an alternate.

 

[hokie66]

BONILL,
Not sure where you are located, but neoprene or natural rubber bearings may be a possibility, but whatever type you use, consult with a reputable bearing manufacturer first. Granor is a company which supplies a lot of bearings in Australia, not sure about in other countries.

http://www.granor.com.au/

 

[Teguci]

Neoprene or rubber pads will allow some lateral movement but they will also impart a lateral force through the connection. The thickness of the bearing pad governs how much lateral movement can be tolerated before the pads start slipping (slipping is bad). The detail will need to allow for the vertical movement into the pads based on variable loading. For light loads, steel or rigid plastic shims can be used but from your detail, I don't think apply.

As slickdeals noted, the studs are keepers and can be replaced with alternative options. We don't want the beam fully slipping off the support (bad day).