Strengthening an Existing Truss 1

[canstruct12]

Hello All,

Canadian structural engineer here. I am currently exploring options to add section capacity to an existing truss. The work would be required to be done in place at ~30feet from the slab below.

The top and bottom chords are T-Sections
Truss Span: 50 feet
Truss Depth: 5 feet
Top Chord: ST 7 WF 30.5
Bottom Chord ST 7 WF 26.5
Web Members: Various Star-Arranged Double Angle Sections (with a single midspan interconnector) 2 - L 3.5 x 3.5 x 5/16 at the truss end to 2 - L 2 x 2 x 1/4 at the truss middle

The truss top chord is proving to be the most difficult to determine a method. It is not possible to add to the top of the T-section without removing the roof and OWSJ. The web members make adding continuous sections to the side or bottom of the T not possible.
Currently exploring welding angles (L4x4x3/4) to the underside of the top chord T. This seems like the only viable option that I can see, due to the physical limitations and interferences. The angle size was chosen to add sufficient area to increase capacity to the required amount, as well fit over the web members and allow weld between the underside of the t-section and angle at the outside.

I am using STAAD Section wizard to determine section properties (STAAD does not give an entirely accurate visual representation of the flange to web radius transition) , then using these to verify sufficient capacity based on applicable CISC S16-19 Standard.

My only concern with this is at the radius transition between the Flange and Web will require chamfering the angle to fit at this location. I was planning to use a 1/4" intermittent weld at 3"-6", and am not sure if there would be enough meat on the angle to effectively weld if it is chamfered to fit.

Any feedback would be appreciated.

 

[dik]

It still may be less costly to use two BAR 2-5/8" dia

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[KootK]

Also, glad to see KootK back in the game!

Thanks, it's good to be back. I'll be ramping up slowly but deliberately, and with joy in my heart.

I was starting to get afraid you had left us for greener pastures.

I have been a bit unfaithful. I've been doing a lot of bicycle repair and restoration work the last year or so and I've been spending time on [link bikeforums.net]bikeforums.net[/url]. Frankly, it's made me appreciate our community even more. The bike forum is riddled with "difficult" personalities. We (mostly me) get a bit heated from time to time but, here at least, you can generally bank on your sparring partners being rational and gentlewomanly. Not so over at the bike place. I was recently accused there of being deliberately obtuse to the point of being "Zoolander" like. Ouch. That gang also as a fairly poor understanding of physics fundamentals which can be frustrating.

 

[dik]

Apparently it can easily be milled off and 'Some shops have 6-axis laser cutters that can laser cut some of these chamfers'.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[KootK]

Thanks for chasing that down dik. I'm surprised at the result but grateful to know the truth of it.

 

[human909]

I have been a bit unfaithful. I've been doing a lot of bicycle repair and restoration work the last year or so and I've been spending time on bikeforums.net. Frankly, it's made me appreciate our community even more. The bike forum is riddled with "difficult" personalities. We (mostly me) get a bit heated from time to time but, here at least, you can generally bank on your sparring partners being rational and gentlewomanly. Not so over at the bike place. I was recently accused there of being deliberately obtuse to the point of being "Zoolander" like. Ouch. That gang also as a fairly poor understanding of physics fundamentals which can be frustrating.

Sounds exactly like my experience on a different bicycle forum! On a local forum here I have a reputation with some of being abrasive and quite "anti-lycra" simply because I don't conform.

I wouldn't put it down to bikes as much just to a more general selection of the population. Here on this forum we have a common set of beliefs and understandings mostly grounded the physics fundamentals of which you refer to. AKA we are all believers in the same one true god!

Nice to hear you have been enjoying a bit of bicycle work. I hope you also had the time to get out riding them and enjoying the sun and fresh air!

 

[KootK]

...quite "anti-lycra" simply because I don't conform.

Fascinating. I got tagged a Zoolander because I made the mistake of mentioning that, when I ride alone, I usually just ride my titanium road bike in a Hawaiian shirt and cargo shorts. It's cool, comfortable for a short training ride, and generates no extra laundry. I consider the extra air resistance to be just added training effect. I mostly ride a multi use path around a body of water and I already probably travel faster than is wise for the environ.

I wouldn't put it down to bikes as much just to a more general selection of the population.

Yes, my thought exactly. Probably closer to true "pub" experience than anything here. Anybody can enter a pub. We're substantially self selected.

I did get out a lot this summer. About 100, 40 minute lunch rides over the course of our painfully short, six month riding season.

 

[bones206]

So this drift condition has existed for 60 years?

 

[dik]

I remember at DB, they had a flat bed machine that dragged the steel edge against a 'carbide?' cutting edge. I have no idea of how long the stock can be... I should have asked, but didn't think about it. Maybe they can do the same with angles... have to try to minimise field welding somehow...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik