Steel Joist Concentrated Load - typical panel point detail 1

[JAE]

I think most engineers, when using an open steel joist, will have on their plans a typical detail that calls out a steel angle to be added to the side of the joist when a concentrated load is applied either to the top or bottom chords - but - away from a joist panel point.

Over the years we've generally used a detail that says the following:
Use the extra angle if the concentrated load is BOTH over 150 lbs. and more than 4 inches away from a panel point.

I've searched all over the SJI site and the Vulcraft site and cannot find any justification for these two numbers (4" and 150 lbs.). I've also seen 6" and 500 lbs.

Anyone know a source document, website, etc. that actually attempts to dictate the source of these numbers - or what they actuall can or should be?

Thanks

 

[Ron]

JAE...have typically just required angle at point of concentrated load, without regard to the distance from panel point.

I don't know of a reference for that, but you could probably prove it out as a percentage of overstress. (say >X percent increase).

$0.02

 

[SteelPE]

JAE we have a similar detail and I can tell you that I have no idea where it came from. There is no justification for the detail in any SJI requirements that I have seen.

 

[JedClampett]

I've seen that detail on joist manufacturer's drawings. It wouldn't surprise me if different manufacturer's change the criteria slightly.

 

[spats]

I also have a standard detail I've used for years that says 150 lbs. max no more than 6" from a panel point... I have no idea where it comes from either, except from my old company.

It's obvious that there is no way to calculate an allowable since we have no idea what chord angle sizes would be, and of course they'd be different sizes for different size joists. Your only clue might come from the fact that it is an SJI standard to ignore top chord bending for a 24" panel point spacing, which is the standard for K-series joists. Of course, that doesn't help you for the bottom chord, which is always lighter than the top.

Let's just call it a judgement/rule-of-thumb. Anyway, when you think of it, how often do you suppose the guy in the field is saying "Gee, I think this is over 150 lbs., so I'm going to add an angle". SJI really needs to weigh in on this... possibly develop an industry-wide table.

 

[MiketheEngineer]

If new construction - just specify the loads and the mfg will provide.

If retrofit you are on your own - but I have found the Vulkraft engineers to be very helpful - if not a bit general. They will say how they would it - but you must do the calcs and accept the responsibility.

 

[mrengineer]

The SJI "43rd Edition Catalog of Standard Specifications and Load and Weight Tables for Steel Joists and Joist Girders" says "For nominal concentrated loads between panel points, which have been accounted for in the specified uniform design loads, a strut to transfer the load to a panel point on the opposite chord shall not be required, provided the sum of the concentrated loads within a chord panel does not exceed 100 pounds and the attachments are concentric to the chord".

 

[MiketheEngineer]

And don't forget that the joist and deck installers often weigh in excess of 250 lbs. There are few "lightweight" construction workers!!

 

[dik]

Mike... I consider them as part of the snow loading <G>.

Dik

 

[dik]

From my General Notes (modify as needed for the project):

OPEN WEB STEEL JOISTS AND LONG SPAN TRUSSES

OWSJ AND LONG SPAN TRUSSES SHALL CONFORM TO THE REQUIREMENTS FOR STRUCTURAL STEEL U/N

OWSJ SHALL BE IN ACCORDANCE WITH THE STEEL JOIST INSTITUTE U/N

OWSJ AND LONG SPAN TRUSSES ARE TO BE DESIGNED FOR ALL LOADS NOTED ON THE DWGS

TOP CHORD MEMBERS SHALL BE DESIGNED FOR A SUPERIMPOSED [250 | 300 | 400 | 500] LB LIVE LOAD LOCATED BETWEEN ANY TWO PANEL POINTS

BOT CHORD MEMBERS SHALL BE DESIGNED FOR A SUPERIMPOSED [100 | 150 | 200] LB LIVE LOAD LOCATED BETWEEN ANY TWO PANEL POINTS

WEB MEMBERS WITHIN THE MIDDLE 1/4 SPAN SHALL BE DESIGNED FOR A MIMIMUM COMPRESSION LOAD EQUAL TO 20% OF THE END REACTION

JOIST SEATS LESS THAN 4" HIGH SHALL BE DESIGNED TO RESIST A 2000 LB LATERAL LOAD APPLIED TO THE TOP OF THE JOIST CHORD U/N

JOIST SEATS LESS 4" HIGH OR GREATER SHALL BE DESIGNED TO RESIST A 1500 LB LATERAL LOAD APPLIED TO THE TOP OF THE JOIST CHORD U/N

OWSJ AND LONG SPAN TRUSSES SHOP DRAWINGS SHALL BEAR THE SEAL OF AN ENGINEER REGISTERED IN THE PROVINCE WHERE THE PROJECT IS LOCATED WHO WILL BE RESPONSIBLE FOR THE DESIGN, FABRICATION AND INSTALLATION OF SAME

OWSJ AND LONG SPAN TRUSSES SHALL NOT BE FIELD MODIFIED WITHOUT WRITTEN PERMISSION FROM THE ENGINEER WHOSE SEAL HAS BEEN AFFIXED TO THE SHOP DRAWING

THE CONTRACTOR SHALL SUBMIT SHOP DRAWINGS FOR REVIEW BY THE [CONSULTANT | ENGINEER] PRIOR TO FABRICATION. SUBMIT SHOP DRAWINGS AS FOLLOWS:
1 SET OF DWGS ON REPRODUCIBLE VELLUM
1 SET OF DWGS IN DIGITAL FORMAT
2 SETS OF PRINTS MADE FROM THE REPRODUCIBLE VELLUM

PROVIDE BRIDGING FOR OWSJ AND LONG SPAN TRUSSES IN ACCORDANCE WITH CSA S16

SECURE OWSJ TO SUPPORTING BEAMS AND COLUMNS WITH 3/16" X 2" FILLET WELDS EA SIDE MIN. REFER TO OWSJ SHOP DRAWINGS FOR FASTENING

SECURE LONG SPAN TRUSSES TO SUPPORTING BEAMS AND COLUMNS WITH 2 - 3/4" DIA A325 BOLTS MIN (SLIP CRITICAL). REFER TO SHOP DRAWINGS FOR FASTENING

COORDINATE HOR BRIDGING WITH MECHANICAL EQUIPMENT TO AVOID CONFLICTS IN PLACEMENT

OWSJ SPACING NOT TO EXCEED DESIGN CAPACITY OF VICWEST W 938, [0.030 | 0.76] ROOF DECK IN AREAS OF SNOW ACCUMULATION

OWSJ SPACING NOT TO EXCEED THAT REQUIRED FOR VICWEST W 938, [0.030 | 0.76] ROOF DECK TO MEET THE LOADING REQUIREMENTS SPECIFIED BY FM GLOBAL

OWSJ SUPPLIER TO PROVIDE FOR SUPPORT OF MECHANICAL EQUIPMENT AND PIPING NOTED IN THE CONTRACT DOCUMENTS

PROVIDE CAMBER TO OWSJ WITH LENGTHS GREATER THAN [30FT | 10.0M]. CAMBER TO BE EQUAL TO DEFLECTION CAUSED BY DL U/N

PROVIDE CAMBER TO LONG SPAN TRUSSES. CAMBER TO BE EQUAL TO DEFLECTION CAUSED BY DL U/N

PROVIDE SUFFICIENT CAMBER AND STIFFNESS TO OWSJ AND LONG SPAN TRUSSES TO PREVENT 'PONDING'

TAKE PRECAUTIONS WHEN PLACING TOPPING SLABS OVER OWSJ TO AVOID LATERAL DEFLECTION OR TWISTING

THE DEPTH OF THE OWSJ SHOE SHALL BE [4" | 100 MM] U/N

THE LENGTH OF THE OWSJ SHOE IN THE DIRECTION PERPENDICULAR TO THE WALL SHALL BE [4 | 100] MIN. THE C/L OF BEARING SHALL BE THE C/L OF WALL U/N

PROVIDE BEARING PLATES FOR OWSJ BEARING ON MASONRY. MAX SERVICE LOAD BEARING STRESS UNDER BEARING PLATES ON MASONRY TO BE [160PSI | 23KPA]

TIE OWSJ BOT CHORD TO COLS U/N. WHERE AN OWSJ DOES NOT 'LINE UP' WITH A COL, PROVIDE A TIE FROM THE OWSJ ON EA SIDE OF THE COL. PROVIDE A STRUT BTN OWSJ AT THE LOCATION OF THE TIE. TIES AND STRUTS TO BE [L3x3x1/4 | L75x75x6] U/N

TJ ON PLAN DENOTES A TIE FROM THE BOT CHORD OF THE OWSJ TO A STEEL BM/COL

Dik