Checking if shoring post design is adequate to support 2

[MaxMedic]

Good Morning,

I just want to double check if the shoring layout attached is adequate.

The existing masonry wall is to be removed and supported by the shoring until a steel beam and posts are put into its place.
The dead weight of the wall above is 1.5k/lf, there is no live or roof load.

The capacity of each shore is 6100lbs jacked up to a height of 10'-0".

I believe that the shoring will be adequate, I just want to double check.

Thank you.

 

[phamENG]

I believe that the shoring will be adequate

Why? What makes you think it's adequate? What calculations have you run? What were the results?

 

[MaxMedic]

I distributed the 1,500lb/lf dead load of the wall above into the slab above as a load per square foot. Then found the worst case tributary area of an individual shoring post and applied the load and saw that that was less than the capacity of the post. I am not sure if I am oversimplifying this. I also added the self weight of the needle and spreader beams.

 

[driftLimiter]

Do you wan't help with your calculation or do want someone here to do it all for you? That kind of weight accumulates pretty quick I wouldn't want any question in my mind before I draw something like this and send it out the door. Do you have a senior engineering who is experienced in this type of thing to discuss your work with? Bringing the loading and the drawing here and saying.... I just want to double check is like asking for a free peer review from an anonymous party.

I assume that you are removing an entire lower level of wall and using this shoring to support the upper level, does the shoring include sufficient lateral bracing? These things concern me more, coming up with the gravity load to the shores should be a trivial task for a structural engineer.

 

[MaxMedic]

I just wanted some help. I do not have a senior engineer to look to.

There is no lateral bracing for the shores. Only posts are proposed to be used. I figured that getting the gravity load to the shores would not be a complicated task, but I just want to make sure.

 

[WinelandV]

MaxMedic,

You can't ignore lateral stability. Your system MUST have some capacity to resist incidental lateral loads. My first company had a policy of throwing a minimum of 10% of the gravity loads as lateral to ensure a robust load path. It was likely overkill, but you certainly don't want that wall to come down because some minor source of lateral load caused your posts to tip over like a matchstick.

Please note that is a "v" (as in Violin) not a "y".

 

[phamENG]

A specific question about something you're struggling with - awesome - we'd all love to help. But a general "please review my work" rarely goes over well here.

I don't know if you have kids, but if you do, ask yourself this question: would you feel good about having your kid sit under those shores while they demo that wall and install the new beam? If there is any hesitation in saying yes, then it's not good enough or you at least need to seek out a real, formal review. Because somebody's kid, father, sister, etc. will be working under it. If you're not thoroughly qualified to design shoring - don't. It's not something to mess around with. There's a reason this is frequently the purview of specialty engineers with a bag of proprietary tricks.

 

[Lomarandil]

Star for winelandv -- lateral load path is critical. 10% is appropriate in many cases, and I typically have a bare minimum threshold of 5% lateral for construction activities even in the best circumstances (shielded from wind, low seismic, hand tools).

Now, it's possible that you are shoring up underneath (and connecting to) a floor diaphragm which is taking lateral loads out to a LFRS elsewhere in the structure. If that's the case, godspeed! But you'll forgive us for being a little cautious to assume that without all the context.

We're happy to help provide some sanity checks and suggestions. Unfortunately, the real world is full of situations where the ideal level of oversight and mentoring isn't available in our own companies. But to add to what phamENG is saying above, also keep in mind the limitations of a career without that sort of direct mentorship. If this is an area you want to grow in long-term, you'll need to find that senior engineer to ask questions of directly, either officially in your company, or in your local network of connections.



----
just call me Lo.

 

[Enable]

I'm an engineer that primarily does shoring and for peat's sake use frames for this kind of application. We have nice, stable, 10-12 kips legged frames available; it's a slap in the face to our shoring gods not to use them here. I don't know what's around or above your shores but typically we extend the unused legs to the next slab or diaphragm above to create stability.

You'll also want to look at securing your posts or frame legs to the spreader beam for incidental loading conditions and possible roll-over (in addition to overall lateral mentioned by others). Your bearing surface is also unlikely to be level so you'll need provisions for shimming / grouting your spreader beams or however you want to deal with that (bonus about the frames is that you can get swivel feet that'll help with at least the foot to beam issue). Don't forget about torsional restraint in all the connections; just because it's temporary doesn't mean we can simply stack beams on beams (well..we can and do but for light loads and your loads are getting a bit much for that).

Beyond that, I generally agree with the above that shoring has a lot of "feel" elements to it and having someone who has been around the block walk the site is highly recommended.

BTW your label indicates needle beams as W8x18 like the spreader beams (text mid right of picture) but your writing suggests HSS.

 

[Enable]

In addition to the loading issues you need to resolve, you should really keep a dead eye on deflection. If you're supporting an existing wall above you can't just go with L/240 or something like that. Any incremental movement may be extremely detrimental to the finishes, and usually necessitates much beefier members than the strength design would call for. Also forget to account for deflections due to on-grade loading in your calculus (it's the system deflection that matters in this case).

 

[human909]

I just wanted some help. I do not have a senior engineer to look to.

I sympathise and can understand that circumstance. Unfortunately like many here have said this really isn't a place to review designs. You could be fine or you could have mised half a dozen things. Lateral loads have been raised and that is just one of MANY possible gremlins than could turn a workable design into a disaster.

Best to refer to an outside consultant if you lack an senior engineer to provide for this. Using an outside consultant can ensure you have a suitable design and you might learn a bit for the next time.

My first company had a policy of throwing a minimum of 10% of the gravity loads as lateral to ensure a robust load path.

I concur with this and it is what I do. 10% also happens to align with the code I used for seismic loads on small structures... It is normally not an onerous requirement on small/medium structures and it lets you sleep at night. The consequences of a lack of lateral restraint can quickly throw any conservatism of the gravity loads out the window.

A specific question about something you're struggling with - awesome - we'd all love to help. But a general "please review my work" rarely goes over well here.

I don't know if you have kids, but if you do, ask yourself this question: would you feel good about having your kid sit under those shores while they demo that wall and install the new beam? If there is any hesitation in saying yes, then it's not good enough or you at least need to seek out a real, formal review. Because somebody's kid, father, sister, etc. will be working under it. If you're not thoroughly qualified to design shoring - don't. It's not something to mess around with. There's a reason this is frequently the purview of specialty engineers with a bag of proprietary tricks.

Agreed. And despite my conflicting comments in that recent thread, I always advocate people be risk adverse and stay within their own capabilities.

Almost any engineer can design a simple structure. But temporary works, rectification works and a host of other things can quickly introduce complications. Personally it is the sort of engineering I relish and enjoy due to the challenges involved. But even 'simple' things can complicate things rapidly.

(I'm in the process of planning out significant floor strengthening for a movement of very heavy equipment with high point loads on a metal deck floor. It is a nightmare, but also a challenge. I'm still going to reach out to an expert I trust to review what I eventually plan out.)