Snow Load Calculator

[Medeek]

Finally finished up the snow load calculator. Moved it to this page:

http://design.medeek.com/resources/snow/snow_calculator.pl

Give it a whirl and let me know what you think.

I wish there was an easy way to calculate the ground snow loads for a given location but unfortunately there is not.

 

[Medeek]

As part of this research I've also compiled and coded an interactive map for the State of Utah for determining Ground Snow Loads:

http://design.medeek.com/resources/snow/utahgroundsnowloads.html

and an interactive map for the State of Montana which acquires its data from the University of Montana's snow load database.

http://design.medeek.com/resources/snow/montanagroundsnowloads.html

 

[Medeek]

I've recently spent some time on looking at the snow load requirements of the ASCE 7-10 and the various state modifications to the IBC and IRC. Obviously this is a gargantuan task, to summarize all this data and present it in a usable fashion. I have managed to chip away at a few states that have standardized snow load data or equations. The latest state I've tabulated is New York State:

http://design.medeek.com/resources/snow/newyorkgroundsnowloads.html

My map of the ASCE 7-10 ground snow loads is still unfinished, not because I cannot finish it but because I am currently waiting on a response back from the ASCE licensing division about the reproduction of the data presented in Fig. 7-1 (ground snow load map). Reproducing or displaying a scanned version of the map seems to be less of a concern that creating an accurate electronic version of the map that is much more useful to the general public and engineering community.

I am summarizing each States snow load requirements on this page:

http://design.medeek.com/resources/snow/statesnowloads.html

As you can see I've only just started. Some states such as Colorado let the local jurisdictions (City and County) set their own snow load requirements so creating a map for the entire state is more difficult but not necessarily impossible. Some states such as Oregon have developed much more sophisticated online systems, I applaud their efforts.

 

[Medeek]

Updated the Snow Load Calculator so that it now gives the reactions for a given truss or rafter based on the O/C spacing.

 

[alwaysFlOoReD]

Thanks for taking the time.

Richard

 

[Medeek]

Oregon Snow Load map is up. This one, like the Montana Map, connects to the snow load database hosted by the SEAO. It also compares the retrieved value against the 20 psf snow load minimum as well as checks the modeled elevation against the actual site elevation and flags the user based on these checks.

The advantage to using this tool is that you don't need to know the lat. and long. off hand, just click on the map and it does the rest.

http://design.medeek.com/resources/snow/oregongroundsnowloads.html

 

[Medeek]

Just completed the Ground Snow Load Map tonight.

http://design.medeek.com/resources/snow/groundsnowloads.html

Digitizing it, so that it was accurate, took far longer than I had planned on but once I was underway I wasn't about to stop.

Note how most of the western US requires case studies, hence many of these states have their own snow load maps and research to back them up.

 

[Medeek]

Interestingly I had a company that manufacturers and installs solar panels contact me regarding the ASCE ground snow load map. They were wondering if there was a way so that their website could send an http request to the map with a latitude and longitude and have it kick back the snow load. Since the map is already in digital format you would not think this would be hard to do. So I got thinking about how I could build a program that given a certain lat and long would automatically click on the map and then fire back the elevation, snow load, etc...

The only problem is google maps implementation of the KML layer does not allow this transmittal of information. So I basically banged my head against the wall for almost 2 weeks trying to do the impossible. However, I was not ready to throw in the towel just yet. Since the KML data is just plain text, (coordinates) I thought there must be some way to analyze this data and determine if a given location is within a certain polygon and if it is then be able to assign that polygon description (ASCE snow load details) to a variable which is then delivered to the client. Turns out this is called the point in the polygon problem and it is well documented:

http://en.wikipedia.org/wiki/Point_in_polygon

So I was about to write an algorithm for ray casting which would have taken some time. Then I thought maybe someone else has done this before and sure enough I found a couple of good perl modules that handled this nicely and I narrowly avoided reinventing the wheel. Just a few lines of Perl later and I had managed to create a nice little API for the ASCE ground snow load data:

http://design.medeek.com/resources/medeekapi.html

 

[sberry]

Over my head but neat.

 

[Harley94]

I'll be waiting for you to post Wisconsin. Thanks for working on this.

 

[Medeek]

Just put up an interactive map for Basic ASCE and IRC wind speeds:

http://design.medeek.com/resources/wind/basicwindspeeds.html

If your designing a residential structure then the IRC 2012 value is the appropriate Basic Wind Speed.

 

[Medeek]

I'll be waiting for you to post Wisconsin. Thanks for working on this.

Wisconsin map is now up:

http://design.medeek.com/resources/snow/wisconsinroofsnowloads.html

Note that this is not the ground snow load but the minimum roof design snow load. Wisconsin does things a little differently when it comes to residential design and has their own code (UDC) versus the more widely adopted IRC.

 

[Medeek]

I apologize, up until now I had no idea that some of these maps were not working correctly with Firefox. I've updated one of my javascript functions which has corrected this error.

Minnesota map is up:

http://design.medeek.com/resources/snow/minnesotagroundsnowloads.html

 

[Medeek]

Michigan Ground Snow Loads map is now up.

http://design.medeek.com/resources/snow/michigangroundsnowloads.html

This zone map is essentially an approximation of the ASCE snow load map with isolines fitted to county and township boundaries.

I'm not entirely satisfied with the appearance of this map since the county lines make the map appear too busy.

 

[Medeek]

Vermont Ground Snow Loads Map is now complete:

http://design.medeek.com/resources/snow/vermontgroundsnowloads.html

This zone map defines ground snow loads by township and city boundaries and is derived from the zone map on page 48 of the 2012 Vermont Fire & Building Safety Code.

Vermont is a small state so the KML for this map was relatively easy to create.

 

[Slowboat]

Very cool! Thanks.

 

[MN4x4]

I already knew my my snow load was 50 psf, but what do I do now with that info? I want to remodel my trusses and I will get an engineer to approve the plans but I'd like to know what I am getting into?

 

[Medeek]

I already knew my my snow load was 50 psf, but what do I do now with that info? I want to remodel my trusses and I will get an engineer to approve the plans but I'd like to know what I am getting into?

If you want to get an idea of what that ground snow load value does, try out the snow load calculator:

http://design.medeek.com/resources/snow/snow_calculator.pl

This will give you an idea of the roof loads involved.

You will still need an engineer to correctly size your truss member based on these loads, but his calculations to determine the loads should match those of the calculator.

 

[Medeek]

Idaho Ground Snow Loads Map is now in Beta testing:

http://design.medeek.com/resources/snow/idahogroundsnowloads.html

This map is quite complex compared too all of the previous ones and requires a much more complicated alogrithm to interpolate between NGSL isolines. Additionally, there are some specific locations on the map that do not conform to the isolines and those are in the process of being added into the final calculations.