ASCE7 Maps 4

[csd72]

Anyone else out there think that the ASCE7 maps totally stink?

The lines are blurrred and the only markings are the county lines. Why not put some cities on there to give you a point of reference. Who knows which county any of my jobs are in.

Does anyone have neat tricks to help.

csd

 

[JAE]

If you are talking about seismic maps....

We don't use the ASCE maps - we determine the Latitude and Longitude of the site in question using this site:

http://tiger.census.gov/cgi-bin/mapbrowse-tbl

And then plug the Lat and Long values into this site:

http://earthquake.usgs.gov/research/hazmaps/products_data/48_States/index.php

(see the Hazard Values - Hazard by Lat/Long link on the page)

And get the S1 and Ss values from that directly.

 

[csd72]

JAE,

Thanks, but wind governs on the east coast and this does not help for that.

csd

 

[ash060]

Well, I know in Florida every county in the state provides their own wind contour map. Maybe other states do this as well.

 

[UcfSE]

The wind maps are meant to be accurate only to the county, so they probably won't ever get any finer than that. If you don't know your speed or location on the maps, you can always call the building department for the city your project is in. I've done that many times, and on a few occasions found that the city had an ordinance requiring design to a wind speed higher than that on the map.

 

[csd72]

I do lots of small projects throughout the east coast and calling the local building department on every one is rather tedious.

I find it crazy that you can meet the state designated wind code and still have the town overide it.

csd

 

[UcfSE]

Such is life.

 

[JKW05]

Has anyone else noticed that the Seismic Maps have changed between '02 and '05?

 

[csd72]

The tectonic plates must have moved around a lot in those 3 years!

 

[joder]

I agree. It should not be hard for the contours to be overlain onto Google Earth.

In fact, I was going to attempt to contact the developers of ASCE-7 to see if that has been done. I'm not sure who to contact. Mehta does not appear in the Texas Tech directory and Delahay has passed away.

 

[MarcbSE]

One of my peeves with the maps are that not only are the lines blurred, but most of the time there aren't even darker lines at the state lines. It sure makes it fun trying to locate the project site sometimes.

 

[10guage]

keep in mind that the lines are drawn thick for a reason. Along the coastal regions, these lines are derived based on monte carlo simulations for 100,000 years of storms. There is uncertainty in the simulation process and thus cannot be that precise. My suggestion is to call permit office to see what is required for your project. Regardless of what ASCE map says, they will likely have their own requirements based on their best interpretation of the map.

 

[csd72]

10guage,

There is uncertainty in anything that has to do with wind - that is why we have a code!

If there is uncertainty to do with interpretation of the code, then that is a big problem for us engineers.

Some dots for major cities would go a long way to clarifying the map.

csd

 

[steve1]

The US Census has a map web site here:

http://quickfacts.census.gov/qfd/index.html

Once there you will be able to insert a city and state and be given the county.

Also you can view and download state maps with the county outlines and names.

Using the above you can then identify the county of interest on the ASCE maps.

 

[csd72]

Thanks steve,

that is very usefull.


csd

 

[JKW05]

USGS also has a site that I find very useful. It will provide latitude, longitude, elevations, counties, etc of towns or other features.

http://geonames.usgs.gov/pls/gnispublic/f?p=171:1:3407925109097789039::NO:::

 

[10guage]

csd

I agree with your comments. Difficult interpretation of the code is unacceptable and opens the doors for decisions that could have drastic differences in outcomes (V^2). My point though is that no matter how nice the map is visually, there is still uncertainty in wind hazard, wind speed degredation, etc. Thus, uncertainty is somewhat inherent - not saying that this is right. Even if the map were perfect, most jurisdictions have decided where they fall geographically. In some states, jurisdictions have traced the design wind speed contour to the street level! I agree, frustrating to deal with. There will likely be significant changes to the map in the next few revisions to deal with statistical reliabilty for different design methods. We can hope that your point will be resolved at that time.

 

[vincentpa]

if you go to

http://www.weatherforyou.com

and type in the city or zip code, the website gives you the weather report. I have also discovered that the website gives a picture of the state with all the county lines shown and a dot showing the location of your search on the map. I use this to find where the location is on the ASCE maps. I enlarge the map and print it and put it in my calcs.

 

[Grizzman]

I use streets and trips to locate the county a particular city is in. then it's pretty easy to locate the county on the wind maps.
always go with the next higher wind zone.
really not that difficult, though a feature similar to the USGS for seismic would be nice.