The posts would need some horizontal framing near the top to hold them in position so perhaps the beams will be better. How are the floor and the beams to be supported at the edge of the pit? Will there be built in ledgers? or will they be part of the cover and bolted to the wall of the pit using cast-in-place sockets or drilled in anchors?

Continuous ledger of steel angle permanently fixed to the wall of the pit with brackets to prevent the beams from sliding horizontally. More information I think may be asked about later - The beams and floor decks will be recessed in the pit so the cover sits flush with the stage floor. The stage floor captures the cover so it can't move horizontally. There is no seismic requirement or concern in the area so we don't have to worry about the panels bouncing out of position. There is no ventilation to the pit when the cover is in place, so there is no uplift concern... although I have asked the MEP engineer to address the Permit Required Confined Space issue created by covering the 9 foot deep hole with a solid roof for weeks or months at a time.

Hello txmedic (Vincent) , I'd be glad to help you as much as I can. Also, PassingtonGreen his a very good engineer and knows his stuff too. He has some very valid initial comments and questions. So do I. We need much more information from you in order to provide you some advice.

Lucky for you that I have done something very similar to this type of project (when I worked for an Albany-based Consulting Engineering firm) in the past (nearly 25 years ago?) at Proctor's Theater in Schenectady New York, where they filled-in the orchestra pit with a similar floor & steel frame. In that case, they utilized electric actuators to raise and lower the entire floor system, depending on it's scheduled use. The NFP organization (community funded + grants) felt that the original stage was too small for plays and stage dancing. Also, it was dangerous as well, with many people falling off the edge into the pit and becoming seriously injured. With the stage expansion they were able to attract much larger troupes and productions, like off-Broadway ones. BTW, Proctor's is a pre-1900 era (I believe that date is correct, but I may be totally off) that was totally rehabilitated in the late 1980's and early 1990's.

www.proctors.org/

You may want to re-think the overall scheme in this vein. It adds flexibility for your facility.

Where are you located, Texas? I'm assuming this by your "moniker"......

From your posting info, can I safely assume that you've already involved the opinion and possibly services of a Registered Architect and/or Structural Engineer already? Or, are you basing your floor system layout based on what other theaters have done in the past?

Is there a plan for this floor deck and framing in existence already? If so, I would really like to review it, possibly an emailed CAD drawing? It's sort of difficult to ascertain the particulars by posted word alone....a picture is worth a thousand words.

Also, what phase of the project are you in currently?

I believe that if you utilize a 4 foot x 4 foot or 8 foot grid layout, based on the plywood sheathing and aluminum panel overlay you would be better served because it cuts down on waste of a very expensive product.

If regard to choosing the correct beam and their spacings: it all depends, and is largely based of the judgement of the design engineer because there are combinations of Live load, Dead Load, Impact Factors, optimum framing layout, spacings, and spans. There is no hard and fast rule, but experience typically trumps inexperience in these matters. Also, another consideration to consider is vibration analysis of the steel frame, which is specially relevant in this case, because of dancer's and actor's "heel drops" as well as dropped and movable theatrical backdrops and other scenery, which could pose some serious dynamic loadings. This in an absolute MUST DO during the design phase.

Okay, this is my last question for now, and the most important one: What is your exact role in this scheme of things?

[BTW, if you are indeed located in Texas you may be in luck. I will be traveling to San Antonio for my son's U.S Air Force Basic Military Training Graduation Ceremonies (at Lackland AFB) on June 6 - 9, with layovers at DFW to and fro. May want to briefly meet together to discuss this project.]

We await your reply Vincent.

Hello CM and PTG - First a quick question for you then I will give many more details and drawings - What is the proper forum etiquette for posting drawings - A) Should I post full E-sheet .pdf directly to the forum? B) Post only snippets of the drawings or sketches? C) Post links to my public dropbox of the .pdfs D) Email the .pdfs to your offline email? I have the full A/S/MEP drawings of the entire project but feel uncomfortable posting links to that much work for all the world to share. What is the usual process here at CR4? Thanks TXM

Rough Dimensions for Pit

https://www.dropbox.com/s/b945zd1uxc17ac3/Pit%20Rough%20Dimensions.pdf

Four Foot Beam Spacing Illustration--

https://www.dropbox.com/s/arxv9okexg0ly3v/CWOW%20pit%20cover%20beams%20and%20ledger.pdf

Four Foot Beam Spacing Illustration with Decks--

https://dl-web.dropbox.com/get/CR4/CWOW%20pit%20cover%20decks%20and%20beams%204%20feet%20spacing.pdf?w=17c2d816

Three Foot Beam Spacing Illustration--

https://www.dropbox.com/s/r4af1k2b4k0r8wx/CWOW%20pit%20beams%20and%20decks%203%20foot%20spacing.pdf

Pit Section Detail 1--

https://www.dropbox.com/s/kl2pxcvg9m953el/Pit%20Section%20Detail%201.pdf

Pit Section Detail 2--

https://www.dropbox.com/s/6pwf2ix2964vc0m/Pit%20Section%20Detail%202.pdf

Pit Section Detail 3 --

https://www.dropbox.com/s/a2gnj74el3433dy/Pit%20Section%20Detail%203.pdf

Hello txmedic,

It would be best to post a framing plan in *.pdf format. When you do so, provide some of the dimensions in text because at the scale the drawing plan will be posted it will be almost impossible to read them. Also, for privacy sake do not post the plan with a title block and the RA & PE seals, if any.

You can also post any pertinent structural sections and details. That would be a great help to fully understand the overall scheme of things.

So, it may appear that a Registered Architect and a Registered Structural Engineer have rendered their respective services for this project, correct? If so, may I inquire why you are seeking outside advice here in this CR4 Forum? Professionally, I don't like to step on toes of another professional. Not only is it non-ethical it is not prudent.

I think we need some straight shooting questions answered here before anyone proceeds further. I hope you understand my hesitation to go further without some sort of solid explanations and background regarding this project and your involvement with it.

Please Note: I will be out for the remainder of the afternoon today shopping with Mrs. Moosie (I call her Sarge LOL). If and when you respond to this posting please understand that there will be some delay on my part, at least until the evening here in ET (NYS). You can always talk to other forum members.....

Hello All,

I will post a plan view and section in .pdf format, along with dimensions.

To answer some of the questions and concerns -

Yes, we are in Texas. Based in Houston, where the project is being built.

I am not an engineer. I wish I was. I love you guys. Differential Equations and non-linear algebra did not love me back. Maybe someday I will have the time and focus to try again.

I have 30 years experience in solving rigging problems and production problems. My company provides rigging and production services, audio and lighting design and installation for theaters, arenas, stadiums, churches. We also do tour design work and one-off design work for corporate shows and events.

I call on the project engineers for help for most projects, but usually my projects go like this -

"Can I hang X pounds? on the top or bottom chord? at these points? Lateral Bracing? Torque or no Torque on these beams? How far from the panel points will you let me go without reinforcing the chords or re-submitting? That 8" pipe-looking thing seems like a sprinkler main, yes? And since we already talked about attachments and limits, I don't think it should hang on my speaker cables here, or the HVAC duct strap over there... Will you have it moved or is it really just some fake plastic tube to fool the inspector, and helium filled?

And, usually our loads are in the 4-8 psf range and most SE's look at our work and our experience and tell us to do what we do and ask more questions if we need to, and they stamp our drawings for our methods of attachment to the beams, and the total load applied to the roof.

We also build flying platforms. Of course that's different than standing them on posts. Most of those platforms use already-engineered aluminum box trusses and we are experienced in how they perform in those applications. We build the custom decks and attach them to the engineered trusses. Usually on 4x4 spacing or even smaller spacings. Usually for very light loads of 800-1200 pounds. Due to costs and because we already know those trusses won't do what we need for this project, we are looking for other methods.

Right now, the guys at CR4 are the most fun and creative bunch I've run across in a while. I thought since this is a little different for us, it would be good to discuss here on the forum.

Yes, there is an RA and SEOR and GC on the project. The project is an expansion of a large church - a new sanctuary and other buildings seating almost 4000.The tilt walls are up, roof is on, the sacrificial precast work slab is being wrecked out, and the sloped floor grade work is in progress for the on-grade sanctuary floor. We have not been hired or contracted to do the pit filler work. We have been asked to bid the project, and present some alternative solutions, as described below.

I would like to consider and present the costs of:

1) Pit filler with clear span beams

2) Pit filler with intermediate posts

3) Moving/Elevating pit floor that rises to a level just below stage level so it can be filled with thin decks that match the stage finished floor.

4) Hydraulics versus Serapid rigid chain versus Spiralift for the lifting mechanism

The orchestra pit is mid stage, not at the front as is typical of most houses.The downstage area in front of the pit will be stick built to provide below-floor infrastructure access. The upstage area, under the choir risers is concrete on grade.

The pit will be covered with a safety net when open, which very slightly complicates the beam placement but is otherwise not an issue for the pit cover.

Here's how I got involved - The architect, church and video contractor had worked with another scenery/portable staging contractor on other projects. This staging contractor frequently hired me for their production rigging needs.

We were initially called to provide a special 120 fpm 8000 lb. 90w x 12h flying backdrop hoist and curtain system - which is another discussion entirely. As I said I am not an engineer, but experience had me worried there might be trouble a'comin... 25 HP drum hoist, 120 fpm fixed speed, 8000 pounds hung on 32LH09 joists designed for 5.0k at the nodes - yes, off topic for now. I am trying to help them solve this part of the production requirement by slowing the travel and reducing the load and going to soft start and ramp/variable speed.

Back to the pit ---

For many months, the staging contractor had provided information to the architect for the choir risers and pit filler based on their standard portable platforms and decks. These decks and risers were engineered and stamped 5-10 years ago ( I don't know how, where, by who ) at 50 psf live load which does not meet any performance space requirements I know about. I'm not even sure they actually meet that rating.

That prior contractor submitted a sketch to the architect, who included the design in the section drawings. The SEOR then placed a note on the drawings that the pit filler elements had to meet the 125 psf live load schedule (UBC?) requirement and that the pit cover would be provided by the staging contractor, and that's what went to plan review. The staging contractor had already submitted a schedule of values. The drawings came back from plan review with the SEOR note that the pit filler and choir risers are to meet the requirement of 125 psf.

I have included the framing plan presented by the other contractor. The (1"x2" Aluminum Tubular Steel) framing and 3/4" plywood clearly cannot meet the requirement on 4 foot spans and 16" centers. The drawing also shows the SEOR plan for the stick built stage area calling for 2" thick plywood and 3-5/8" steel framing on 16" centers to meet the requirement for the fixed staging.

Yes, many have asked about "aluminum tubular steel" and we are still waiting for clarification on the pressures and temperatures at which this magic pit cover alloy is expected to function and what flame retardants to use on the plywood for those temps.

Once the 125 psf load requirement was made clear, and after about six months of frustrating communications, the other contractor declined to participate and has left the project.

The architect has turned to me for a workable solution that stays within the previously under-quoted budget. Always optimistic that only someone else can prove me wrong, I believe I can make it happen. I know it won't be 1x2 tubing and 3/4 ply.

The pit area measures about 42' 6" x 16' 8"

The reason I have not approached the SEOR for design assistance/approval is that the architect has asked me to first come up with budgets for -

1)beam-only and 2)with-posts budget to take to the client.

They expect me to do this initial design work, present a new schedule of values, then have the SE stamp the client approved approach. I am trying to keep smiling, learn something new and keep a client happy.

I can see that there are many questions and considerations.

When I first looked at it, it seemed like such a simple question - Big Beams, or Posts???

I've already mentioned in a few meetings that the very least expensive material cost would be to fill the pit with sand or crusher run and deck it with plywood. I thought about water and inner tubes or styrofoam and plywood but thought it would be way too much fun. They didn't ask about labor cost to clean it out.

There are plenty of commercial fabricators of pit fillers - Wenger, StageRight, StagingConcepts to name a few. The problem is that 22 of the 30 decks shown in the present design are custom curved pieces, will require multiple site visits for measuring and fitting from far-away factories, and this blows the budget. We have the ability to water jet/plasma/cnc the laminated decks and attach to the steel or aluminum understructure at a much more affordable rate, and just the freight costs saves thousands.

So, the architect is looking to us for a solution that fits, and I'd like to give a great answer. No toe-stepping or hurt feelings anywhere here. This is a completely up-front "please come save the day" call for solutions to a problem that on the face would seem simple. I just don't want to go to the SE and look stupid. I guess I really don't even care about that. I know I can learn a few things here, and I've read enough of yall's posts (see? Texas!) that I knew I could get some good help.

I don't want to waste any time or speculation funds (mine or yours) on something that can't even be done - for instance if I were to chase the beams-only method and make the entire schedule of parts and budget and then submit and get it tossed back at me and get told I'm an idiot - that it will never work. At which moment I would quietly leave, because I don't like to work with people who call me an idiot for asking questions to solve a problem they can't solve themselves!

Here are some of the complications -

A) there is very little access at the left and right edges of the pit, so it is not possible to drive a forklift/pallet jack/stock picker to the downstage edge to aid in placement of the beams. It is possible to dolly that downstage edge around the end, but then it will have to be lifted off the dolly and lowered into the pit to sit on the ledger/bracket.

B) the pit will be full of instruments and the church would prefer to not have to remove the piano (requiring re-tuning) in order to cover the pit. No posts or minimal posts is better for this reason.

C) there is very little, practically none, storage backstage for the pit cover so it needs to be stackable or at least cartable so that it can be moved and stored elsewhere. I don't think it's practical to look at making the largest pieces 4x16 for this reason, so I think we have to use beams beams and decks, or intermediate posts, rather than a deck that can span the distance without the beam. That deck would also be quite heavy to move. On the other hand, some of the decks closer to the edges might be capable of making the span without using the beams.

D) This will inevitably be installed or removed by persons with little or no training. At some point, someone on the church staff is going to decide they need a rehearsal, and they are going to attempt this without proper training. While we can't be responsible for stupid, we can try to make a system that is at least "Ikea Instructions" simple. Maybe. We can certainly insist and document that only trained personnel are to install and remove the pieces.

E) The pit is 9 feet deep. Touching the pit cover from the pit floor will require ladders, adding to the complexity and safety issues. A system that can be installed from the stage floor will be safer.

Drawings next. Thanks for your help.

CM --- A Huge Lone Star Thank You to you and and your son from all of us here in for his service to our country. I would be honored to meet you both if possible while you are here for his graduation.

Good Morning Vincent,

Thank you for providing the drawings, however I was not able to pull up the framing plan depicting the layout w/ beam spacings @ 4' o.c. together with the deck overlay. The file will not open.

I sincerely apologize to you not getting back to you until this morning. Mrs. Moosie & I were out shopping most of yesterday afternoon and a good part of the evening, so after dinner & desert and a good strong German brewski I went into a diabetic coma for the remainder of the night. Sorry about that!

One of the first things that I'm going to ask you is: Why does this pit infill have to be removable/temporary? Can it not be permanent? I do understand that the orchestra instruments, incl. the untouchable piano, as stored in the pit, but is there a way to move them in & out via an entrance at the lower level (pit floor level)? I may be somewhat deft regarding this....

I REALLY don't know why the Architect for this project is relying on you to do his work? It should be the other way around. Ditto for the SE. the should be undertaking the design, spec'ing it, and going out to Bid. Seems to me that the project is a little ass backwards in a lot of regards, especially going to you for the solutions. To me, they appear to have failed their client, the church in question, with an adequate solution and economical budget (or staying within the budget). It's what we used to say in the Army "CYA" (Cover-Your-Ass), as it'll come around to bite you at know where. Please watch yourself, particularly with the RA, as he seems to be saving face with the client, as his problem will become your problem.

IMPO, the high degree of the pit wall curvature is adding a lot of expense and complexity to this project. It makes framing over the pit very difficult to say the least.

As you have said it would have made life much more easier for you if the pit was completely filled in. I agree with you on this, as it is the cheapest construction option in my opinion. Or, the pit "roof" was permanent. Or, the pit walls were demolished and a new rectangular pit was constructed to eliminate the curvature(s) and a permanent frame and deck installed. Of course this option would require the construction of new reinforced concrete pit wall along the entire perimeter, with an access portal (w/ a door or double-leaf door) so that the instruments can be retrieved. To me, a steel frame with a clear span appears to be the only viable option. Installing intermediate steel posts isn't going to work because of the instrument storage issues.

Q: If the infill pit roof is to be temporary, does the steel frame have to be removable as well, or are the deck panels that are the only removable portion?

I also don't understand the need for that aluminum tubing (or an adequate substitute steel tube frame) framing running perpendicular to the steel beam framing. Yes, I see the need IF the deck panels are 4'x4' they act like a two-way slab and they bear on framing along their entire perimeter....but if the panels were 4'x6' or 4' x 8' they'd bear only on the steel framing. Of course the individual panel edges should interlock with one another for continuity sake. Ideally, the panels should be attached to the top flange of the beams with screws or clips.

I also question the need to have the deck panels constructed from plywood and a aluminum skin. With a specified 125 psf design service Live Load, other more acceptable and appropriate deck materials could be installed, especially if the entire pit roof was permanent.

Some viable options if the pit infill roof was permanent:

1. Structural steel framing w/ welded shear studs (along the top flanges of the steel), galvanized steel corrugated composite floor deck, and a thin reinforced cast-in-place concrete floor slab. This is construction industry standard for suspended floor slabs in buildings.

2. FRP framing in lieu of structural steel framing. It's light & strong, but may pose a problem in regard to fire rating.

3. Manufactured wood framing members, such as Micro=Lam beams etc etc., but again there may be fire code issues unless a UL/FM-rated sheet rock ceiling is installed that conforms to the fire code.

4. An all-aluminum "space frame" in installed in lieu of structural steel. This would be ideal if the pit was rectangular in nature, but because of the pit curves this may not be viable. Also, due to it's depth there most likely be a minimum head room issue. Additionally, if the deck panels are removable the space frame most likely will interfere with passing the musical instruments through it (if there is no other entrance to the pit at the lower level).

Forgive me for the limited response to your query this morning, but I've only had 2 mugs of Joe so far and the gray matter is a little slow on uptake! LOL

Thank you for thanking us for our service. In regard to my upcoming trip to San Antonio, about the only time I would be free to meet with you would be the evening of Weds. June 6th. the remainder of my stay will be spent at the Graduation Ceremonies (on the 7th, 8th and the morning of the 9th) at Lackland AFB. You need a pre-authorized DOD/USAF Visitor's Pass to gain access to the base, so I don't think you'll need go that route and the requisite security check/clearance. There's only one other evening/night available, and that is I believe is on Friday the 8th where my son receives his one and only "one night pass/leave" to go out to diner with his guests. Since my x-wife and 2 grown-up daughters will also be attending the graduation I suppose I will be sharing Brian with her and them at a restaurant. Ohhhhhh joy, ain't that grand! LOL

On Weds. June 6th, my flight is scheduled to arrive at SAT around 1:10 PM CT. By the time I get my rental car and find my way to the hotel near the base & "Check-in", it'll be at least 3:30 PM, the earliest we could meet. I can meet with you to discuss this project thereafter, that is, if you want to drive all the way from Houston (love that city!), which could be quite a haul just one-way!!!! Instead of you needing to travel to SA and expend a small fortune in gasoline + crimp your business schedule, we may be able to discuss your project on the telephone? PM me if this is possible....my call and dime.

Hey, a question for you.....if you're familiar with the San Antonio area. Do you know of any decent, but inexpensive, Texas steak houses or Tex-Mex restaurants near or within easy driving distance of Lackland AFB? I'm a HUGE BBQ lover, and love anything Texas BBQ'ed! Chain restaurants are acceptable as well.

Have a great Sunday!

Good Morning Captain!Sorry for the drawing mis-load. Please try again, I took them all off, reloaded, and redownloaded. They open here. If they don't open there, it's a bug I need to know about because I use this method to share files will lots of clients. Good to know there might be an issue.
Pit cover has to be removable/temporary because 46 Sundays of the year the performance is done with the pit open and the players in the pit. The camera shots include sweeping job shots from audience over the stage, over the down stage ensemble, over the pit, and up into the choir risers. When the pastor is on stage, the players and instruments have to be "in the hole" and the magic wall I am building flies in (crashes/falls???) and divides the stage so there's a clear background for the message.
Beams have to come out so the players in the pit don't feel like they are in a cage. Nevermind the pit safety net that makes them look like they are in a birdcage at the zoo. Really, please never mind for now... Arggggg. It's just crazy!!!! Time for another cup of coffee.
There is a personnel (ADA requirement) wheelchair elevator backstage but it is too small to move even the tympani and no way to move piano. So the beams have to come out to get the big stuff out of the pit and to give the open look they want.
I agree on all points about the RA and the SE, except that I think the RA is actually trying to give me a chance to provide a solution and let me get the job, rather than going back to the church and saying - "hire Wenger, pay them $100,000, have posts in the pit, never like it, and be disappointed" - and then I don't get the job. He wants me to have a shot at making some money on the project, but I have to offer a workable alternative he can sell.
Curved pit walls wall will not change. There are too many other staging elements and design elements of the entire room, including the proscenium arch, built around the same centroid and radii.
Overnight, I devised a plan for a beam dolly/hoist that makes it practical to move big I-beams into place. I can move and place a W8xx or W10xx steel or aluminum with no problems. We can dolly the beams back upstage to their storage cart. That problem is solved.
The 1x2 tubing shown was intended to be the ribs for the decks to stiffen the decks for the 4 foot span. That 1x2 with 3/4 ply would never be enough to make that 4 foot span, even if the 1x2s were on 8 inch spacings... I don't think.
To keep the ribs from rolling, I was thinking 1-1/2 x 3 on 16 centers, with 1-1/2" plywood. Makes attaching the plywood easier also, as the screw lines can zig-zag for just a little more anti-roll stiffness to the top of the rib.
Deck ribs would have plates that will pin to the beams with these - http://www.bigskyprecision.com/T-Handle.php
We looked at decks like the StageRight honeycomb laminate, and foam core aluminum. Again, the curves make these cost prohibitive. I even thought about air-entrained or other kinds of lightweight concrete, as it would be easy to form, easy to make "special decks" for special events, and they sure couldn't tear it up, and it would meet any fire codes I could think of. We could dang near do it like this - place beams. Lay in pan deck. Line edges of pit with gasket material. Lay in reinforcing mesh. Pour slab. Lift out slab? Diamond Wet Saw cut panels. Glue on finished floor surface. Done. What would each deck piece weigh? More than the steel and plywood, of course. But, it is far less expensive??? More profit, more happy people, more smiles.I am open to ideas on that.

I think the firecode issues knock FRP and Lam things off the table.

We can use fire treated plywood and if we don't need the skin, then we will delete it - it is heavy and expensive and a pain to cut when laminated to the plywood.
You are exactly right about the all aluminum space frame - it's a headroom issue and a cost issue. To make it use less tubing, it has to be 16 - 22 inches tall, and the fabrication labor is big dollars compared to a 10" inch stock I-beam. Lighter? Sure.
San Antonio Mexican and BarB-Q... Yep. Gotcha covered.
Vincent

Regarding the beams -

What about bar joists?

Lighter for this span than I-Beam?

Use more joists, on 2 foot spacing? Making the decks thinner and lighter?

Okay,

Try this link to the drawings. Dang. Never had this problem before.

https://www.dropbox.com/sh/0ynsrelpr5d9edq/ouhVQFSDas

Hello Vincent. Good news is that I was able to open up all of the files!

I was thinking about this project of yours all day long, and the more I thought about it the more questions I came up with.

Q#1: How are the musicians getting into the pit so that they can play their instruments? Is there a door in the pit wall below to allow ingress and egress? I sure hope so, because forcing them up and down a ladder may be a huge Building Code violation. At a minimum, stairs w/ handrails complying with the Code are in order.

Q#2: Why does the floor deck need to be in compliance with the fire code and fire rating since the pit walls are reinforced (?) concrete (and presumably there's a concrete slab on grade at the bottom of the pit?)? I just don't get it, especially when the pit, as it exists now, is wide open to the rest of the church. Is the existing floor under the assemblage and the choir areas fire-rated as well, even though they appear to rest directly atop a concrete slab on grade? Some food for thought. If there are mechanical rooms downstairs adjacent to the pit, then IMPO all that is needed is a fire-rated self-closing door in the pit wall. I think the RA needs to re-think this fire-rating requirement of the removable pit deck, as I really don't think it is absolutely needed. I may be missing an important fact about this that I am now currently unaware of.

Q#3: How are the new steel floor beams to be attached to the existing concrete walls, especially the curved walls? Steel Shear Tab Plates and structural bolts? Has the project SE even detailed this and/or designed it?

Q#4: Why are the existing concrete pit walls receiving what appears to be light gauge metal studs and drywall? I hope it isn't for a fire rating sake, because that doesn't make sense to me. For appearances sake? Having these new wall coverings is going to compound the installation and removals of the structural steel. They will get beaten up!

ASIDE: I looked at a few codes and found some disparities between them regarding the design Live Load for your Occupancy, which falls under "Assembly Areas and Theaters", with the specific area falling under "stages".....

According to the State of Texas Building Code, Chapter 16, "Table 1607.1 MINIMUM UNIFORMLY DISTRIBUTED LIVE LOADS AND MINIMUM CONCENTRATED LIVE LOADS", the minimum Uniformly Distributed Live load for this floor is 125 psf. Fine enough, so far. We know that already.

But,

According to the American Society of Civil Engineers (ASCE) ASCE Standard 05-07, Chapter 4, "Table 4-1, MINIMUM UNIFORMLY DISTRIBUTED LIVE LOADS, Lo, AND MINIMUM CONCENTRATED LIVE LOADS", the minimum Uniformly Distributed Live load for this floor is 150 psf. Professionally, I would opt to use the higher Design Live Load requirement of 150 psf, based on nearly 35 years of engineering experience and knowledge.

In regard to using Open Web Steel Joists, I wouldn't, for 5 primary reasons alone:

1. Even if you reduced the joist spacings down to 24" o.c. your joist depths are going to end up with somewhat greater joist depths than the structural steel Wide Flange (WF) beams. Remember the head room issues....

2. The floor will be much more susceptible to vibrations which can be induced by heel drops (especially women and their high heels!), which is a common occurrence inherent with this type of "light" floor construction. They, the joists, make for some really bouncy floors that many people can perceive quite easily. The client will not be a happy camper with a bouncy floor that spent a lot of money on recently. Vibration analysis of this type of floor system is absolutely required. To solve the vibration frequency problems requires adding more mass carried by the joists, such as the permanent construction of a carried reinforced concrete floor slab of sufficient thickness (say greater than 4.5", possibly more) with galvanized corrugated Composite steel floor deck that must be puddle welded to the top chords of the joists. The welds are absolutely required at the Top Chord members (a compression member also under bending) because lateral restraint is required to prevent rotation of the joists and thus failure. Really, I don't think that this is a viable option with removable floor deck, regardless f the type of deck material(s) employed.

3. All OWS Joists require several rows of permanent steel "bridging", top and bottom and running perpendicular to the joists, for stiffness of the floor framing and to prevent longitudinal axis rotation. The bridging must be secured to each joist top and bottom chord. Usually this is done either by field welding or bolted clip angles. Also, the bridging must be structurally secured to the existing pit walls with steel angles and anchor bolts. By having removable floor joists with removable bridging is a recipe for disaster in the future, because someone somewhere somehow will forget to reattach the steel bridging or reattach them incorrectly, which will lead to a catastrophic structural failure.

4. How are the ends of each joist to be supported at their respective bearing shoe (ie, a flat horizontal rectangular plate under the end of the top chord)? Normally, joist ends bear directly upon masonry walls featuring horizontal steel bearing plates with underside anchors cast into the top of the concrete or concrete masonry wall. With the existing pit walls curved as they are, this is not technically feasible nor economical. The technical design is an engineer's nightmare....ditto for the steel joist fabricator. Lots of extra expense here because very exacting and detailed field measurements are required by the steel joist fabricator (bodies in the field = Mega $$$$), and equally expensive shop fabrications to make this even workable.

5. How are the deck panels to be structurally secured to the joist top chord members, irregardless of the deck material type? Steel joists require lateral top chord support at least every 24" o.c. (and no greater) with some sort of fasteners or welds. I would recommend in this case fasteners be provided every 6" o.c. along the entire top chord of each joist. Removable screws compound this problem. I hope nobody forgets to use the screws when reinstalling the deck panels....another recipe for disaster down the road. Torquing and re-torquing self-tapping metal screws and the like is going to be a BIG Problem. You can expect many screw failures, even in the near term.

I believe the only viable and feasible option is to install the steel beams. Too bad that they must be removable, as that sets-up a scenario for structural failure if someone screws the pooch by incorrectly reinstalling them and the floor deck....bolted connections are unforgiving if someone doesn't install them or installs them incorrectly (torque wrenches are required to obtain the prerequisite bolt tension/preload etc.).

In regard to the removable panels: have you thought of or investigated the use of 24" x 48" lightweight concrete panels w/ steel reinforcement? A 2" thick panel could weigh around 200# using 115 pcf LWC. Actual thickness will depend on design flexure and shear requirements. You can possible get 5,000 or 6,000 psi Compressive Strength (f'c) 28-day age LWC. I honestly think that it could be done, and two grown men could hoist them. You could also limit their individual widths to 12" to make it easier to lift them. Talk to you local precast concrete manufacturers about this. You may be able to have custom made prestressed concrete panels manufactured locally or nearby. This type of manufacturer is located all over the country, and there are many in Texas alone. I'd go with a prestressed lightweight concrete panel if it were me because you're using very thin stretched wire instead of standard rebar for providing the tensile strength. Check it out, as you have nothing to lose doing so. Also, all panels should feature a Tongue & Groove interlocking mechanism along their entire perimeter to provide floor stiffness.

[The more I personally learn about aspects of this project, the more that I am really beginning to think that the RA and the Owner have not thought things out, nor consequences of their designs and desires. Just my opinion.]

Have a great Monday!

===Captmoosie

Hello Capt!

1) - There's a stairway down from backstage and an ADA elevator.

2) Agreed. The downstage stick-built stage is calling for fire rating. I will ask why.

3) The section drawings currently indicate a continuous 4x6 angle attached to the concrete upstage face, and to the steel posts on the downstage face. I have already mentioned that will probably need to be beefed up in some fashion.

4) Acoustics and appearance and a way to route the audio and video conduit behind the wall surface. I agree, not a good plan.

5) Yes, when first asked to participate in the project, I asked about how they planned to access the over-stage lighting. They said they would drive a boom lift to the upstage edge of the pit. Enter through the far upstage roll-up door. I said OMG are you crazy??? The floor of the stage and the pit cover are to be the same dark hardwood finish. Not even a border delineation. Someone is going to drive that 36,000 pound lift right out onto that pit cover. Or worse, into the pit without the cover. I've suggested an interlocking laser interference system that kills the lift if it breaks the beam. They ARE listening to me on that.

Meanwhile I've also suggest going as high as 250 psf because of some of the scenery I've seen them use in the past, and I guarantee they are going to drive a car on this thing at some point. Cars may not be 250 psf overall, but can be if only one wheel is on only one deck - As I've seen you discuss at length regarding garage floors in North Dakota. Yes, I read a lot of the forum trying to learn!!!

Open web joists and bouncy - totally agree, Thanks for confirming my suspicion.

Lateral bracing - see, I KNEW I would be learning through this process. I knew it. That bracing is not there just for construction and "wind bracing" it's there because if the joist rolls even slightly, it loses dang near all strength, yes?

YES also to the complication of install and removal.

Field Visits and Custom Joist ends - Bad Plan #4. You are so right.

Fasteners - Bad Problem Waiting to Happen #5. I will not participate if they even mention bar joists again.

I'm liking the prestressed concrete panel idea. I will investigate Monday.

What are your thoughts on aluminum beams versus steel beams? Aluminum will be more expensive. Other concerns? Is it possible that by the time we get an aluminum beam that meets the load requirement, it's nearly as heavy as the steel beam?

Thanks for everything.

BTW - My awesome girlfriend is a chef, and she has the scoop on good eats in and near San Antonio. We also have a great friend who is an Army MD and works there all the time. We will get you all set.

Vincent

Hello Vincent. Sorry for the delay getting back to you, as I was somewhat swamped with meetings yesterday, especially meeting with my attorney. Well, it's now official; I received my NYS Certificate of Incorporation paperwork for my engineering firm....I'm now a Professional Corporation (S-Corp)!

I'm offering some comments based on your latest posting:

1) - There's a stairway down from backstage and an ADA elevator.

Okay, I was previously unaware of this. So, is there a wall opening and/or self-closing fire-rated door in the pit concrete wall anywhere?

2) Agreed. The downstage stick-built stage is calling for fire rating. I will ask why.

The RA should be seriously looking into this and possibly revising the Contract Documents, but I'm not going to second guess him/her why this is being done like this, as there may be circumstances and conditions that I am not aware of presently......BUT, Is this downstage stick-built floor system area proposed atop an existing concrete slab on grade, or is there a basement or crawlspace underneath it? I would make more sense to demo the existing floor slab and raise the entire area with infill gravel topped with a new slab. Just my thoughts....

3) The section drawings currently indicate a continuous 4x6 angle attached to the concrete upstage face, and to the steel posts on the downstage face. I have already mentioned that will probably need to be beefed up in some fashion.

There's a strong possibility that those continuous curved L6x4 lip angles will need to be be beefed up. Depending on the eventual determined Design Live Load (125, 150, or 250psf, etc.) and the thickness of the angle legs, they may need to be seriously beefed-up with equally stronger expansion anchors. To me, there appears to be no detail or provision provided for connecting the ends of the floor beams to the wall. ideally, these connections could be a shear tab plate with structural bolts located at the beam webs, w/ said plate welded to a vertical wall-mounted plate with 2 vertical rows of expansion anchors like Hilti, Studs, etc. These connections will have to be engineered by the SE. I do not see the cont. L6x4 ledger angles supporting the ends of the floor beams. They're only needed to support the edges of the deck along the curved walls.

Another thing, why can't these floor beams remain in-place permanently, with the floor decking being the only removable sections? Having removable floor beams will be another recipe for a future disaster, as someone is going to screw-up down the road reattaching them. You could use the frame to support that safety fall net. Just curious, but how are the musical instruments extracted out of the pit, especially the piano? Is it a upright or whatever? and will it fit between floor beams if they're spaced @ 48" o.c.? Someone ought to field measure the widest instrument and make doubly sure it is actually retrievable.

4) Acoustics and appearance and a way to route the audio and video conduit behind , the wall surface. I agree, not a good plan.

Agreed, not a good idea placing those conduits there. IF they stick-build the "downstage" floor area (the "pew" area, correct?), why not run the conduits there instead where they'd be concealed, thus eliminating the need to build these new walls lining the entire pit perimeter + reducing the overall usable space of the pit for storage. All of this wall work adds extra expense IMPO where it really isn't needed, plus it hinders installation of the infill floor system. There are a lot of architectural finishes/coatings that can be applied to the bare concrete wall and pit floor slab that would render it visually acceptable and pleasing to the eye. Again, the RA should be addressing this.

5) Yes, when first asked to participate in the project, I asked about how they planned to access the over-stage lighting. They said they would drive a boom lift to the upstage edge of the pit. Enter through the far upstage roll-up door. I said OMG are you crazy??? The floor of the stage and the pit cover are to be the same dark hardwood finish. Not even a border delineation. Someone is going to drive that 36,000 pound lift right out onto that pit cover. Or worse, into the pit without the cover. I've suggested an interlocking laser interference system that kills the lift if it breaks the beam. They ARE listening to me on that.

You must be kidding me, right? Drive a motorized boom lift of that magnitude onto the stick-built upstage is shear madness, especially when it may not be design to support the maximum rated wheel loads of the lift + impact factor because it's a rolling load just like a bridge. If they were driving this atop a concrete slab on grade with sufficient thickness, reinforcement and subbase material that can safely support this vehicle, then I'd say no problem. Also, if they drive atop a suspended concrete slab or other type of floor system located over a basement or crawlspace area there may be some very big structural safety issues at stake. Has anyone even thought this through? Both the RA and the SE had better thing about this issue long and hard and come up with some viable solutions.

Okay, so this lift is required to safely access the stage lighting? How high above the finish floor are these stage lights, and can they be safely reached by another mechanism such as a tall stage ladder rated for 300# live load (person), or a smaller and lighter scissor-lift that Contractor's usually utilize on jobsites? Why can't the entire stage lighting assembly (assuming multiple rows of lights, etc mounted on a steel or aluminum frame) be lowered to the floor instead for easier and safer access at the floor level. Hell, that's what they do on Broadway in NYC in many of the large (and smaller) theaters. Just another cat to skin.......

Meanwhile I've also suggest going as high as 250 psf because of some of the scenery I've seen them use in the past, and I guarantee they are going to drive a car on this thing at some point. Cars may not be 250 psf overall, but can be if only one wheel is on only one deck - As I've seen you discuss at length regarding garage floors in North Dakota. Yes, I read a lot of the forum trying to learn!!!

Agreed Vincent, the minimum Design Live Load (LL) may have to be bumped up to 250 psf, possibly even 300 psf, for the Uniformly Distributed LL. But if a motorized boom lift or even a car is to be introduced to the floor system, then I would use a minimum vehicle wheel (not axle) Concentrated Live Load of no less than 3,000# (pursuant to ASCE Standard 7-05, or later edition; Table 4-1). Or if they are insistent on using that boom lift, then you must employ a maximum rated wheel loads of the lift (as well as axle load, depending on the wheel spacings side-to-side, and front-to-aft). 36,000# vehicle is a lot of weight, much akin to driving a small 8 or 10-wheeler truck on that floor. Also, to take into consideration is the largest dolly wheel load of the stage prop frames, which I can imagine can be quite robust. Impact factoring must be included in the designs of the floor. Yet more issues to be addressed by the RA and SE.

Thanks for remembering and even mentioning the blog re TCHMECH's garage floor framing issues up there in ND! I'm very glad that someone is reading them and learning! LOL

Open web joists and bouncy - totally agree, Thanks for confirming my suspicion.

Lateral bracing - see, I KNEW I would be learning through this process. I knew it. That bracing is not there just for construction and "wind bracing" it's there because if the joist rolls even slightly, it loses dang near all strength, yes?

Yes, you are correct in your assumption that if the open web steel floor joist rotate (roll) about their longitudinal axis they will lose nearly all of their load carrying capacity. That's a very scary scenario. Ever seen on the news where they experience a roof collapse during construction? Most of them occur because the joists or roof trusses (wood or steel) were not secured properly (lack of lateral bracing) all it takes is for one to start rotating and the end effect is a like playing dominos>

YES also to the complication of install and removal.

Field Visits and Custom Joist ends - Bad Plan #4. You are so right.

Fasteners - Bad Problem Waiting to Happen #5. I will not participate if they even mention bar joists again.

I'm liking the prestressed concrete panel idea. I will investigate Monday.

What are your thoughts on aluminum beams versus steel beams? Aluminum will be more expensive. Other concerns? Is it possible that by the time we get an aluminum beam that meets the load requirement, it's nearly as heavy as the steel beam?

Thanks for everything.

BTW - My awesome girlfriend is a chef, and she has the scoop on good eats in and near San Antonio. We also have a great friend who is an Army MD and works there all the time. We will get you all set.

Sorry about splitting up my post into 2 parts, but the CR4 editor went hay-wire, then crashed and burned....

I hope you made out alright talking to a precast concrete company. Some additional foods for thoughts:

No matter what type of material is chosen for the removable floor deck panels, make sure that each edge features a strong enough tongue & groove mechanism so that all of the panels interlock. They must be robust enough to transfer load from one panel to the adjacent panels; to facilitate continuity and diaphragm action. If the panels end up as some sort lightweight precast concrete arrangement, then continuous galvanized steel T&G inserts (w/ anchors) can be cast into each edge of the panel. Also, it is possible to cast into the top of the panels permanent and retractable lifting eyes or other similar type of lifting lug with anchoring wires, etc, with certified maximum load ratings (minimum Factor of Safety of 4:1 is preferable, or more...). Personally, I wouldn't use less than 4 lifting inserts per panel, unless it's a small panel (like a triangular or corner one). The deck panels do not necessarily have to be manhanded per see, but it would be nice just for being able to stack them or move them about. Cast them into any size that you desire; sizes that are easily moved, especially through door openings, hallways, and the storage ares. the owner could even by a pair of small movable engine hoists that feature: 4 dolly wheels on extendable fore-legs, a hydraulically operated piston (hand pumped) to lower and lift the loads, and extendable lift boom, and capable of at least lifting 1,500#. You can find them on Ebay or NorthernTools.com for roughly $300 apiece. I have one downstairs in my garage that is great for lifting heavy loads and not just engine blocks and lawn tractors!

Aluminum wide flange beams or rectangular tube may be easy to lift, but the sections may get deeper then you want because of head room issues, as compared to say Fy=36 ksi or Fy=50 ksi structural steel wide flange beams, or rectangular tubes (Fy=46 ksi). Whatever the aluminum material grade is and the member configuration is, it'll be most likely custom manufactured and very likely very expensive. Then there's the issue of steel being much more ductile and resilient to absorbing repeated dynamic (ie. wheel loads, dolly loads, etc., with impacts) loads (fatigue life) vs. aluminum. I wouldn't even bother looking into this alternative, unless the RA and SE want to look into it. The SE had better be well versed in the design and limitations of aluminum framing members. NOTE: The lightness of the beams may be a non-issue if they can remain permanently in their respective positions.

Very kewl that your GF is a chef!!! So, what type of chef is she, and what is her specialty? LUCKY LUCKY LUCKY YOU!!!! :-)~ Talking about chefs et all, the Culinary Institute of America (CIA) is located right down the road from us, some 20 miles away in Hyde Park NY. Luv the place!!! ***YUMMERS*** We're very lucky here in the mid-Hudson River Valley to have so many great restaurants around, mainly staffed with CIA grads! Most are excellent and have contributed to my bulging waistline. Ditto with my wife's cooking and baking. although she's Registered nurse I tell her that she missed her calling and should have gone to the CIA. She's that good! I'm no slouch either in the kitchen, so we usually cook together as a team.....it's fun!

I look forward to a long list of good eateries around or in close proximity of Lackland AFB outside SA! Just have to be affordable as I'm on a tight leash with Mrs. Moosie! LMAO