# Using Spanman - what is the definition of 1 and 2 rows bridging



## Mikeoz (Apr 23, 2018)

I found https://spanman.net/ 
A calculator for Australian Building code span loads!

You can supply any email for trial, no need to give details or activate.
Just give the site an email address and use.
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My question:

When you use Purlin Single Span to Calculate *C Section.*
https://spanman.net/Members/purlin-single-span

I choose Country Australia, Building type Garage.
*Span 4220mm*, *Spacing 1000mm*.
*Roof Custom Setting 33kg/m2*.
Ceiling (none).
Design Material = Cold Formed / Light *C Section.*


The results are returned for using C Section using minimum material with:
1 Row Bridging.
Or,
2 Rows Bridging.
Or,
Just the C Section size without bridging.
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SOLUTIONS
Name                            kg/m  Depth (mm)

C10015 2 rows bridging 2.6  102

C15012 1 row bridging 2.9   152

C10019 2 rows bridging 3.3 102

C15015 1 row bridging 3.6 152

C20015 1 row bridging 4.5 203

C15019 1 row bridging 4.5 152

C15024 1 row bridging 5.7 152

C20019 1 row bridging 5.7 203

C25019                          6.5 254

C20024 1 row bridging 7.2 203

C25024                         8.2 254

C30024                         10.1 300

C30030                         12.8 300

C35030                          15.2 350
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I am assuming the C Section recommendations with no bridging can support load independently?

What do they mean by 1 or 2 row bridging?

Mike


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## cda (Apr 23, 2018)

Welcome

Our first Australian Farmer!!!


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## Mikeoz (Apr 23, 2018)

Yes,
Dabbler.

The Spanman Calculator has me confused with 1 or 2 row/s bridging.
My assumption is that load is always shared across 2 purlin's.

But what is 1 row bridging?
My thinking is that the load should be the same for every purlin in system, which makes this confusing.



Perhaps a builder can point out the logic?


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## Paul Sweet (Apr 23, 2018)

Bridging (at least in the US) is solid blocking or diagonal bracing to prevent the joists from flopping over on their sides.  One row would be at midspan, and 2 rows would be at the third points.


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## Showme (Apr 26, 2018)

As a guy who erected many bar joists in commercial and industrial buildings over the years, I can say that a single bridging job means that there will be a single row of either small 1" angle or 3/8"-1/2" round stock steel bar at (usually) the bottom chord of a panel point about every 10-20 feet, perpendicular to the joists. 2 rows of bridging would call for a row of angle or round stock welded up under the top chord as well as at the bottom chord. Normally, the top and bottom chords would be made up of two long angles with flanges pointed out, with the second flange/leg pointing toward the opposing chord. These angles are welded to round stock or small angle that is welded to the two cords at each contact point as it is zigzagged (for lack of a better word) diagonally back and forth the length of the joist. They perform the job of stabilizing the joists while the roof or flooring sheets are placed and welded. The second row of bridging reinforces the top span from spreading. It also stops the wiggle in the iron (joist) when walking and working on them before the corrugated sheeting is placed.


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## ADAguy (Apr 27, 2018)

Welcome Mate,
How far in the "outback" are you (smiling)
What City? I have family in Perth.


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## Mikeoz (May 2, 2018)

Showme said:


> As a guy who erected many bar joists in commercial and industrial buildings over the years, I can say that a single bridging job means that there will be a single row of either small 1" angle or 3/8"-1/2" round stock steel bar at (usually) the bottom chord of a panel point about every 10-20 feet, perpendicular to the joists. 2 rows of bridging would call for a row of angle or round stock welded up under the top chord as well as at the bottom chord. Normally, the top and bottom chords would be made up of two long angles with flanges pointed out, with the second flange/leg pointing toward the opposing chord. These angles are welded to round stock or small angle that is welded to the two cords at each contact point as it is zigzagged (for lack of a better word) diagonally back and forth the length of the joist. They perform the job of stabilizing the joists while the roof or flooring sheets are placed and welded. The second row of bridging reinforces the top span from spreading. It also stops the wiggle in the iron (joist) when walking and working on them before the corrugated sheeting is placed.










The Calculator is said to be Australian Code, which would include tolerances for specific material and building practices.

Recommendations for preset roofing materials, Iron or Tiles effectively tie the Purlins as part of Australian Standards!   
The Calculation is adjusted according to a code taking the roof material into account.

The question relates to the Calculation Algorithm for Custom Weight?
I assume this is just a modified version based on Iron?

I used the calculator to design a self supporting frame for Solar Panels!
It Should Including a tolerance for 100kg person and panels based on basic iron settings.
The bridges will be the same C-Section material, so locking top and bottom of Purlins.
I just borrow the roofing Terminology. 


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I see there are C-Section joiners that clamp the open C side of Purlin. More money?
What are your tricks for making a good right angle connection to open side of C-Section?

Thanks


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## Mikeoz (May 2, 2018)

Spanman don't reply to question.
No technical support, but a handy guide for design.


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## drahcirtimothy (May 13, 2018)

http://www.stramit.com.au/sites/def...s__bridging_detailing__installation_guide.pdf

Go to page 5 under Bridging Hole Location.


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## cda (May 13, 2018)

Welcome !!!

Winter time down under??


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## drahcirtimothy (May 13, 2018)

cda said:


> Welcome !!!
> 
> Winter time down under??


Perth 'winter' is 8 to 18 Celsius (45 to 65 F), very mild.


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## cda (May 13, 2018)

drahcirtimothy said:


> Perth 'winter' is 8 to 18 Celsius (45 to 65 F), very mild.



Yep

Some people are lucky 

My sister traveled most of the coastline of Australia a few years back 

She sent great pictures


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