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Bar Joists on CD's by EOR
2

Bar Joists on CD's by EOR

Bar Joists on CD's by EOR

(OP)
I'm reviewing some shop drawings for a set of bar joists on a 6:12 slope and the mfg'r keeps asking for the axial drag force due to the roof slope.  I looked at the 2005 SJI Specification, Section 6.1 and could not find anywhere that this information was required to be specified by the EOR.  The joist mfg'r's catalog states this requirement but I'm not sure I agree that it is my responsibility to provide this axial load if the roof loads are only DL+LL, nothing special.  Has anyone else come across this issue?

http://www.njb-united.com/ncj/ncj20061.pdf   Section VIII

TIA


RE: Bar Joists on CD's by EOR

Could be just me, but that sure seems like something they could calculate on their own.  They've got the loads and the geometry; the resulting drag force should be part of their joist design.  I've never had that come up.

RE: Bar Joists on CD's by EOR

(OP)
I just spoke with the technical director from SJI and he agreed with the joist designer...go figure.  They basically want every load spelled out and diagrammed.  I just wish their specification would spell this out to the EOR.

RE: Bar Joists on CD's by EOR

Are they asking for the down slope component of the gravity loads?  

I don't design steel joists, but I do design glulam trusses.  In a case where the trusses is only required to carry gravity loads, I can't imagen asking the EOR for the down slope component.

RE: Bar Joists on CD's by EOR

STR04, is there a metal deck diaphragm attached to the joists? I have a project going now where I just asked my local joist mfr the same question about whether I should show this component or if he would come up with it and design for it. He stated they don't consider this downward drag if there is a welded diaphragm to the joist top chord, that they consider this component goes into the diaphragm then into the LFRS and bypasses the top chord. I don't know if I completely buy that though.


We make a living by what we get, we make a life by what we give.
Sir Winston Churchill

RE: Bar Joists on CD's by EOR

STR04

The reason the joist mfr doesn't want to consider the downward component is that it will probably increase the cost of each joist.

I wonder how many people include the down slope gravity load component in their diaphragm design?

RE: Bar Joists on CD's by EOR

Do you think the diaphragm is stiff enough to be relatively close to the axial stiffness of the joist?  It would have to be in order for the diaphragm to take load.  I would guess that for typical flexible diaphragm this is not the case unless you have small spans.

RE: Bar Joists on CD's by EOR

If the joist is only connected to its end walls, or some beam, there theoretically is zero (or very little) joist stiffness in its axial direction - i.e. the joist has nothing pushing back uphill at its ends.  Therefore, the diaphragm must take it all.

RE: Bar Joists on CD's by EOR

I agree.


We make a living by what we get, we make a life by what we give.
Sir Winston Churchill

RE: Bar Joists on CD's by EOR

JAE - Thanks. Got it. Don't know what I was thinking.

RE: Bar Joists on CD's by EOR

I guess one twist might be if it is a gable building with joists welded on either side to a beam at the ridge, the joist top chord could be acting as a tension drag bringing force into the top joist connection. The force at the ridge may then cancel, assuming the building is symmetrical and loaded the same on each side of the ridge.

But that would be more of a joist connection concern (if you assumed the diaphragm did not take it all in this case since you have a stiff joist reaction point due to opposite forces at the ridge) rather than buckling of the top chord.


We make a living by what we get, we make a life by what we give.
Sir Winston Churchill

RE: Bar Joists on CD's by EOR

Nevermind, the end reaction at the ridge connection would still be vertical in that case. The joist end reactions would only be not-vertical in the single slope case where the diaphragm is assumed to take all the downward component and you are left with the perpendicular to joist component reaction at each end of the joists.


We make a living by what we get, we make a life by what we give.
Sir Winston Churchill

RE: Bar Joists on CD's by EOR

I like to make some observations regarding the free body diagram in the joist catalogue:

1. The FBD shows the upper joist support/seat to be a roller. Theoretically this may be correct. The way to achieve roller end conditions the joist seat must be allowed to move horizontally. This can be achieved via various means such as bolting, providing slotted holes and lubricating the bearing surface. However, majority of joist seats, at both ends, that I see are welded to supporting beams (or bearing plates) with minimum of 3/16 by 2 inch long fillet welds.

2. If my observations above are correct, then both ends of the joist should be pinned; not pinned-roller due to the vertical and horizontal restraint that the welds will impose.
 
3. If you model any truss with pinned-roller end conditions you will get differing joist reactions and member stresses from those obtained from pin-pin boundary conditions.

Comments anyone?

Regards,
Lutfi

RE: Bar Joists on CD's by EOR

Lutfi,

You would have a larger stiffness requirement for a pin-roller than for a pin-pin, correct?  That seems like a good reason to model a joist pin-roller.  Plus you wouldn't have the horizontal thrust to take care of at the support.  It makes it easier to use a joist in a larger variety of details.  That's my guess.

RE: Bar Joists on CD's by EOR

Just trying to be the devil's advocate here-

If you have a 6 in 12 sloped roof, and somehow the snow sticks to it, where does the thrust loading go?

Pulling numbers out of the air:

(30 ft joist)x(8 ft trib)x(20psf Snow)x(SIN(31.3) [6 rise in 12 run]) = ~2.5kips per joist

I don't even know if that psf is reasonable, I live in Texas and design high-rises, snow usually doesn't control in my designs.. And I might have totally messed up the geometry- but I did stay at a Holiday Inn last night..

But a simple calc could give the manufacturer an idea of how much additional force to design the connection for, would reduce their potential liability, and should make you as the EOR feel more comfortable with the final product and your design. This also may be a subtle way for the manufacturer to tell you they see that something is off in your design.

My punchline is that it doesn't make sense to me to 'neglect' an effect, especially if you are the EOR, the manufacturer is asking for it, and in the real world it exists; plus the manufacturer may indirectly be trying to tell you something.

RE: Bar Joists on CD's by EOR

There is a very good book, "Designing With Steel Joist Joist Girders Steel Deck". The book was published by the Nucor Corporation and authored by James Fisher, Michael West, and Julius Van De Pas.

In chapter 8, Responsibilities, the book states "The Codes of Standard Practice of SDI and SJI govern in the absence of other contract requirements". The key element here is what are the contract requirements.

When I work for a structural engineering firm I designed a number of structures using press plate wood trusses. The specifications required that the trusses were designed by or under the direct supervision of a PE. In addition the specifications required the truss supplier to desig and supply all the truss to truss connections, truss hold downs and supplementaly bracing required for truss stability.

I often got the response from the truss supplier that they were supplying a component and that they were not responsible for the addition requirements. I would explain to them that if they wished to supply the trusses then they must meet the specification. And that if they were unwilling to meet the specifications, there were other suppliers who would.

RE: Bar Joists on CD's by EOR

(OP)
RARSWC,

I agree with your statement and would say that I am very disappointed with this particular joist mfg'r, but after reviewing the SJI specifications, which has no teeth, I could not say where the responsibilities of the EOR stops and the mfg'r picks up.  The technical director from SJI even agreed about the ambiguity in the code.  This industry lives in a vacuum and wants every load spelled out or they will assume no special design work is required and pick out their canned joist design per SJI load tables.

STR04
 

RE: Bar Joists on CD's by EOR

STR04

I tend to agree with the joist manufacturer, that the EOR should provide this force.  The axial force depends on factors unrelated to the joist design, i.e. is the ridge beam supported by columns?  Is there a tension tie between the walls?

RE: Bar Joists on CD's by EOR

(OP)
jmiec,

The ridge is supported by columns, therefore no tension tie is required.  Keep in mind steel frame with steel bar joists.  Not wood rafters & tie collars.

STR04

RE: Bar Joists on CD's by EOR

Since I work for a fabricator of glulam trusses, I partially understand why the joist mnf may have request load information.  

In many cases the design load used is based on the engineer's judgement.  If the fabricator determines the design load and completes  the shop drawings, the fab may be forced into additional work later when the EOR disagrees with the fab assumption.  

In the above case the fab will incurr additional cost for redesign and shop drawing revisions.  So in many cases it is easier for the fab to ask the EOR for the load.

This is a very interesting thread with a lot of good comments  that have been posted.

One aspect I am still interested in, is where does the load go?

Based on my experience, assuming the down slope component is resisted by the deck, probably is the best approach over all.  However if the joist mnf makes that assumption, I think the mnf should tell the EOR.

I don't know any one who has designed a steel deck diaphragm for wind load and the down slope component of the gravity load that is not being carried by the joists.   

RE: Bar Joists on CD's by EOR

I can't say I have seen anyone design a diaphragm for the downslope component plus lateral loads either, but that is what should be done where the joists can't resist the load themselves.

I was thinking about valley beams yesterday with joists framing in on each side. Even with a diaphragm, this should be a case where the joists could resist the downslope component on their own. So I can see where there may be confusion on when to include the downslope component and when not to, and that is why this manufacturer is probably trying to say he always leaves it up to the EOR to decide. If you tell him that the downslope component should be added to all joists and he still does not do it without you specifically telling him for every case, then maybe he is just being lazy. But it is finally the EOR's responsibility to check whatever the joist mfr. has done in the end anyway.


We make a living by what we get, we make a life by what we give.
Sir Winston Churchill

RE: Bar Joists on CD's by EOR

STR04-

In any case, the EOR should provide the axial force.  The path of the forces is the responsibility of the EOR. These joists may have axial force, depending on how the EOR carries the loads.

RE: Bar Joists on CD's by EOR

It has been a very long time since I specified bar joists.  However if I remember correctly you can get horizontal joist seats for a 6/12 slope.

If I was reviewing  shop drawings, that showed the joist with horizontal bearing seats; I would expect the joist mnf to design the joists to resist all gravity load. I would not expect the mnf to transefer part of the load in to the metal deck.

With horizontal bearing seats, under gravity load the only force that would be transferred to the supports should be a vertical reaction.  The stresses developed parallel to the slope would be internal to the joist.

Requiring the joists to resist all the forces on the slope probably would not be cost effective. So I am not surprised that a mnf would make that assumption.  If mnf is assuming that the deck is resisting the down slope component the mnf should make that clear to the EOR.  However from experience the mnf may already know that the down slope component will not be critical to the deck design.

RE: Bar Joists on CD's by EOR

I am designing my first sloped steel joist roof structure.  After reading the thread can I assume the horizontal thrust at the bearing wall is dumped back into the diaphragm and distributed into the masonry shear walls?  I've been thinking about the wood structures I've designed and have never considered a horizontal thrust on the walls, but the trusses all had a horizontal bottom chord to tie the bearing walls together and internalize the horizontal force.  What about wood scissor trusses?  How are those supports designed?

My major dilema is that we have a 4:12 pitched roof over an auditorium area with a potential large span (if the architect has his way) which will produce some enormous horizontal forces at the bearing walls (like 7.5 k/ft!!) unless they can be assumed to be distributed into the diaphragm and taken out into the shear walls.  I've looked through several of my books and cannot find mention of how to deal with this horizontal force.  I even have a book with an example of a sloped roof joist with a ridge beam and it does not address the horizontal reaction.  

I do have "Designing with Steel Joists, Jiost Girders and Steel Deck" and have read the section on sloping joists.  The author notes that if translation is restrained that horizontal thrust will be imparted to the support structure.  Back to the previous discussion, does this thrust go into the wall or can it be dispersed into the diaphragm and the lateral system?     

RE: Bar Joists on CD's by EOR

Dispersed into the diaphragm as long the diaphragm is adequately connected to the steel joists and designed to take the downslope component over to the LFRS. And the LFRS has to be able to take it.  The 7.5k/ft sounds really high, you might double check that.

RE: Bar Joists on CD's by EOR

knelll

On what page in "Designin with Steel Joist....", is the discussion about sloped joists?  I tried to find something in my addition with out luck.  Hopefully I just overlooked it, as I would be interested in reading  that section.

RE: Bar Joists on CD's by EOR

Hi RARSWC,

I have the 2nd edition of the book from 2002.  The discussion is on pages 102 and 103.  
I still don't understand why the EOR is responsible for specifying the internal axial load on a sloped joist.....  They cover that load calc on pg 103 in the last paragraph.

knelli  

PS.  I think I found a solution to my problem, I was getting the major kickout force because my joist was partially a scissor joist.  I found a way to add a ridge joist girder without interupting the auditorium space.  

RE: Bar Joists on CD's by EOR

I was thinking about this today again.

Say you have a single slope building with steel joists spanning from a beam at the low end to a beam at the high end. There is nothing special about the beams (they are not intended to take thrust in the horizontal direction like a tension ring). Also, assume there is NO diaphragm capable of carrying the downslope component.
 
If there is only gravity load on the roof, the vertical reaction at the low end will have a component parallel to the top chord of the joist. So I think there still can be compression in the top chord of the joist even with only the vertical reaction at the low end acting on the horizontal seat. So there is no stiffness provided in the axial direction of the joist but there is the component of the vertical reaction at the low end which allows compression in the top chord to be generated. The joist is not stable if you look at it this way (no horizontal reaction is available) but there is only a vertically applied load anyway.

Or have I lost my freakin mind today?

RE: Bar Joists on CD's by EOR

Haynewp:

I think your mechanics for the situation are sound, but that it's a question of degree:  There is almost no way you're going to generate enough load to have the joists fail out.  It would be an extreeme case indeed, since the diaphragm is always going to have some capacity against this loading, and will allow the joists to help each othe out.

Or is it my turn to question my own sanity?

Regards,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...

RE: Bar Joists on CD's by EOR

I modeled a sloped member today with vertical loads with pinned supports and I did not get a horizontal reaction at the support.  then I changed one support to a roller and it did not move horizontally.  I think as long as the joist is sloped and not a scissor type then there is no horizontal reaction at the support?  Like you said haynewp, there is only vertical loads applied and the horizontal forces would be internal to the joist....  
SO that means that SJI is requiring the EOR to give an internal drag force??

Quote from "Designing with Steel Joists....." pg 103 in the sloped joist example:  

"In addition, the manufacturer will need to design this joist for the affects of the load parallel to the joist.  This load would be:  {LL*cos(theta) + DL)sin(theta).  This load will be applied as an additional top chord axial force in the joist by the manufacturer."  

Back to Statics 101.  Vertical load a sloped member.  Give pinned connection one end and roller the other.  Sum moments about the pinned connection and voila!  No horizontal rxn!?

RE: Bar Joists on CD's by EOR

I am just thinking that before the diaphragm has been connected to the LFRS, that the joists are building forces parallel to their top chord by virtue of their own vertical reactions at each end. Once the diaphragm is welded down and connected to the LFRS, the loads applied ato the roof after this point may be assumed to go into the diaphragm.

RE: Bar Joists on CD's by EOR

Knell

Thank you for the information.  I have an older edition of the book.  10 years ago when I specified a lot of bar joists I found the book very usefull.

RE: Bar Joists on CD's by EOR

My take is a sloped member with a support(wall or beam) at each end has only a vertical reaction at each end. Gravity load acts solely in the vertical direction. If you break this load into two vectors: one perpindicular to the beam and parallel to the beam, it still has a vertical resultant along the beam and at the supports. This will even apply to a beam with a sloped seat bearing connection. The loads are resolved within the connection. If you model this in a computer modeling program, you can verify there are no horizontal reactions taking place at the supports....A sloped beam does not have axial load from gravity loading, a sloped column(or beam-col) does since it does not have a support at one end, although this axial load would be  resolved internally within the truss....          

RE: Bar Joists on CD's by EOR

I have an old, 2 page (some of it hand written) article from Vulcraft illustrating how to calculate the axial component on the joist but it is only due to wind loads not gravity.

RE: Bar Joists on CD's by EOR

A sloped beam does have axial force from gravity load. It's hard to visualize, but it's there.

RE: Bar Joists on CD's by EOR

For interesting reading, go to:

www.sbcindustry.com/technotes.php

The Michigan Tech Notes was just updated Sept 13, 2006 so this is very current.

I've been on both sides of the issue - I've been the one sending plans out to component manufacturers and I've been the one designing the component.  Both sides think they don't have the responsibility for calculating loads on a truss or joist.  Here's the answer...

The WTCA has published Tech Notes for each state and a National version specifying the Design Responsibilities for Commercial Construction Projects.  The WTCA represents the structural building components industry.  This version specifically mentions trusses, but I bet you'll find a steel joist version out there somewhere too.

Here is what the Michigan version says:

"WTCA has developed this Technical Note to clearly outline a component manufacturer's role and responsibility for commercial construction in the context of the building code and professional engineering law applicable in the State of Michigan.  This Technical Note is based on conversations with and questions from various Michigan local building officials and registered design professionals.  The analysis is based on the current engineering laws of the state Michigan and the 2003 Michigan Building Code (MBC), which is based on the nationally recognized model building code the 2003 International Building Code (IBC)."

Skip to Page 4 -

"In preparing the Construction Documents, the Building Designer needs to provide the Truss Designer with the information necessary to properly design the Structural Building Components for the Building.  According to ANSI/TPI 1-2002 (TPI 1) Chapter 2 (see Appendix C for complete text), which is adopted by reference in the MBC Sections 102.4 and 2303.4, and Chapter 35 "Reference Standards" provisions (see appendix B), the following information should be provided:

........skip to...  2.5.2.4 The location, direction, and magnitude of all dead and live loads applicable to each Structural Element and Truss...

2.5.2.5  All Structural Element and Truss anchorage designs required to resist uplift, gravity, and lateral loads;

2.5.2.6  Allowable vertical and horizontal deflection criteria and any specific criteria...

2.5.2.7  Proper transfer of design loads affecting the Structural Elements and Trusses;

2.5.2.8  Adequate connection between Trusses and between Structural Elements...but not Truss to Truss girder connections...

2.5.2.9  Permanent bracing design for the Building...and permanent bracing for all Structural Elements and Trusses...



I think this is pretty clear.  It is the Building Designer, not the component designer who had better specify the loads to be applied.  I read that as the EOR, if a structural engineer is involved, or the Architect if no SE is involved.


Right below that section reads:

"The Truss Manufacturer and Truss Designer must rely on the Building Designer to take the information provided by the Truss Design Drawing, the Building Component Safety Information (BCSI 1), and the Building Designer's analysis of the flow of loads through the Building to design a Permanent Building Stability Bracing system that takes the reisted truss member buckling loads (if any) and tie these loadsas off tto the Building's load path system...   The Building Designer is the professional who is most intimately familiar with the flow of loads through the entire Building and is the one who can use this knowledge to ensure bracing load transfer and overall Building performance success..."

It is recommended that a copy of this be included with contract documents.  I think that is a great idea.  

And to any structural engineers out there who don't think they should have to take responsibility for figuring the loads on a truss (me included...), this should help explain why truss designers make $15/hour and engineers make $30+, don't you think?

  


 

RE: Bar Joists on CD's by EOR

Here is similar info from the SJI regarding joists:

steeljoist.org/graphics/assets/media/Whats_New/NASCC_2006_Final_Paper.pdf

RE: Bar Joists on CD's by EOR

I like the statics 101 example.
I too want to be simple.

You have a mono sloped member with supports at each end.

The only way a horizontal thrust is generated, from vertical loads, is if the support at the high end moves vertically down and the member rotates about the high end.

RE: Bar Joists on CD's by EOR

Look at the following perfect example, taken from a good old college textbook:

http://tinypic.com/view/?pic=42i37s7

Conclusions:
1) There is no horizontal thrust at either reaction.
2) There is an axial force in the member.  This force balances out in the joist, but will range from compression at one end of the joist to tension in the other end of the joist.

Model a typical sloped beam in an analysis program.  There will be no horizontal reactions.  The member axial force will definitely be non=zero, and vary depending on the load.

RE: Bar Joists on CD's by EOR

I think the point of argument here is that the EOR is responsible for specifying the APPLIED loads and that the axial force due to the geometry is an INTERNAL load.  The engineer doesn't tell the joist/truss supplier what the internal web and chord forces are, so why is this internal load any dirrerent?

RE: Bar Joists on CD's by EOR

knelli-

As I said much earlier in this discussion, it's because the axial force is dependant on how the building carries the forces, and only the EOR knows this.  Looking at the example in AggieYank's textbook,  the joist is fixed at the bottom with a roller at the top.  Other buildings have different boundary conditions which will result in different axial forces in the joist.

RE: Bar Joists on CD's by EOR

jmeic.  If there is only a vertical load, there are only vertical reactions.  Different boundary conditions won't change that.

I agree with the people who say this should be calculated by the joist designers.

We spell out the loads and geometry (end to end) and they design for any forces.  The axial force we are discussing is a direct result of the typical dead and live roof loads.

RE: Bar Joists on CD's by EOR

Re: AggieYank's post...

A pin-roller scenario will have no horizontal reaction.  I pin-pin reaction will.  Different boundary conditions do matter.  (This is a pet peeve of mine.)

RE: Bar Joists on CD's by EOR

nutte,
sovle the problem with a pin-pin condition.  There are still no horizontal forces.  If you solve it by hand, scan it and post it to the site so you can prove that a pin-pin does have a horizontal reaction.  The statics are the statics and the statics dictate that no horizontal forces exist.

RE: Bar Joists on CD's by EOR

This is simple statics.  A pin-pin has four reactions (a vertical and horizontal at each end).  This is statically indeterminate.  Three equilibrium equations, four unknowns.  When you sum up the forces in the horizontal direction, you get H1+H2=0.  You know the magnitudes are equal, but you don't know the value.

A pin-roller only has three reactions, so you can solve it easily.

RE: Bar Joists on CD's by EOR

The amount of horizontal deflection required for a support to be treated as a roller is extremely small.

While almost all connections in reality are somewhere between pinned and roller, I would never try to design a member as true pinned-pinned.

RE: Bar Joists on CD's by EOR

The sloped member carries tension (internally) even though there is no horizontal reaction or externally applied force.

RE: Bar Joists on CD's by EOR

Vincentpa, no offense, but if you can prove that a sloped member carrying gravity loads will not produce horizontal reactions at its supports - I will tear up my license and eat it:) Do a simple test: take a plastic ruler, put one end on slippery surface (no horizontal reaction) and elevate the other end at 1:2 slope (or any slope for that matter), take a pencil and use it as a support at other (elevated) end. I publicly announce that I will stop practicing engineering if the ruler doesn't slide towards the lower side!!!
The horizontal part of reaction needs to be accounted for at such a big slope. It needs to be resisted either by the diaphragm (most commonly) or by the biaxial bending of bond beam (if masonry system) or by biaxial bending of steel beam (if steel framing). There will be increase in axial compression of top cord between the puddle welds or fasteners. This can be calculated by obtaining the total axial force that joist will transfer to the diaphragm (assuming one is used) and dividing it by the number of fasteners, or if no diaphragm is used, then entire force is taken by the top cord of the joist. In either case, max. additional axial force taken by any member of the top cord of joist should be reported to manufacturer, since they seem unwilling to run their own calcs (some will do it, some won't, Vulcraft does it, for example).

RE: Bar Joists on CD's by EOR

Big appology, Vincentpa, the above comment was addresed to nutte, pin-ruller connection does have horiz reac. The only way to avoid horiz reac. is to provide (as required by SJI) sloped seated connections, where bottom of the seat is horizontal. Sorry for the mix-up. I still stand by what I said, though, drag force occurs either way. Again, sorry Vincentpa, it was directed to nutte.

RE: Bar Joists on CD's by EOR

Right, this is equivalent to joist supported by sloped seats, with bottom of seat horizontal. Since the roller provides reaction perpendicular to tangent of contact surface, there will be no horiz reaction as long as joist is supported by sloped seat, like I said earlier. Also, note that your example assumes the point of contact is at the center line of beam. When this is not the case, additional moment is developed. By the same principle, roof deck is supported by the joist, which is sloped. Joist provides reaction perpendicular to the plane of roof deck, so shear between roof deck and joist wiil have to be resisted by pudle welds or fasteners, which will further transfer it to top cord of joist - resulting in compressive stress increase.

RE: Bar Joists on CD's by EOR


There has to be a diaphragm connected back to the LFRS to take the downslope component out. Until then, there is an axial force component in the top chord of the sloped joist as soon as it is installed, participating in support of the construction loads.

There is no horizontal external reaction from vertical loads prior to diaphragm and LFRS connection for a pinned-roller case (assuming horizontal end supports!), unless you are analyzing the joist as pinned-pinned. Then there is still a NET horizontal reaction of zero.

When you place the diaphragm and assume it takes the downslope component along the length of the joist under SUBSEQUENT loads, then it changes the orientation of the external reactions at the top and bottom of the joist under these subsequent loads. At the low end, the horizontal component would actually be directed inward towards the building.

The gist of this whole thread for me is that I am going to specify the downslope component for the joist mfr. and may give a load diagram since I don't know what mfr. will be fabricating the job. And I can't rely on when the diaphragm and LFRS will be installed to assist the joist top chord. That seems to be the conservative way to go with all this.


When things are steep, remember to stay level-headed.

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