Straight Line Winds

[jar546]

They are more common each year. We need better design criteria.

 

[Msradell]

What part of Texas was this?
Assuming it's not along the coast I wonder if the design requirements for hurricane protection would also work for straight-line wind protection. It seems like they are both very similar and quite a bit different from the effects of tornadoes.

 

[ICE]

What was the wind speed?

 

[jar546]

What was the wind speed?

95-100MPH

 

[Paul Sweet]

Was that the average speed, or 3-second gust? A 90 MPH (working stress design) gust is the minimum for most of the country, and higher near the coast or mountain passes. A factor of safety of 2 is built into the code, so it should take almost a 130 MPH gust to cause structural failure. Shingles & siding will probably start blowing off at much lower speeds.

 

[rktect 1]

I heard that the contractors were good, knew what they were doing and built it to minimum code requirements. Which is why the municipality didn't need to inspect it.

 

[jar546]

Was that the average speed, or 3-second gust? A 90 MPH (working stress design) gust is the minimum for most of the country, and higher near the coast or mountain passes. A factor of safety of 2 is built into the code, so it should take almost a 130 MPH gust to cause structural failure. Shingles & siding will probably start blowing off at much lower speeds.

They come from microbursts so I would think they are not sustained winds

 

[Mark K]

The Factor of safety is less than two, probably closer to 1.7, and is intended to address a number of concerns so not all of it is available to deal with higher wind speeds. Also the wind pressure increases with the square of the velocity. Remember the strength of wood of a given grade varies considerably.

Did they use the right grade of lumber? Were all the needed fasteners installed?

It is even possible that the members may have been sized to resist the wind but the failure could have been because some roofing or other element was not properly installed. Once part of the roof failed it allowed adjacent areas to fail at lower wind speeds..

 

[jar546]

The Factor of safety is less than two, probably closer to 1.7, and is intended to address a number of concerns so not all of it is available to deal with higher wind speeds. Also the wind pressure increases with the square of the velocity. Remember the strength of wood of a given grade varies considerably.

Did they use the right grade of lumber? Were all the needed fasteners installed?

It is even possible that the members may have been sized to resist the wind but the failure could have been because some roofing or other element was not properly installed. Once part of the roof failed it allowed adjacent areas to fail at lower wind speeds..

Great questions. Seeing how 115mph is becoming the standard with ICC codes, previously 90mph, I fail to see how any of the construction in the photo met any standard other than the good ole' boys standard, hence the results in the photo.

 

[my250r11]

Great questions. Seeing how 115mph is becoming the standard with ICC codes, previously 90mph, I fail to see how any of the construction in the photo met any standard other than the good ole' boys standard, hence the results in the photo.

It is Texas, they don't like rules & laws. Most places only have code just in major cities. Last I heard they don't require any kind of licensing. We get a lot of contractors here from Texas and a few are good, the rest are very questionable.

 

[ADAguy]

It is Texas, they don't like rules & laws. Most places only have code just in major cities. Last I heard they don't require any kind of licensing. We get a lot of contractors here from Texas and a few are good, the rest are very questionable.

Sure that wasn't a tornado?

 

[jar546]

Sure that wasn't a tornado?

Was not a tornado. This was a straight line wind as investigated by FEMA and NOAA. I have plenty of tornado photos which is why I chose this one. These are always a threat anywhere in the US.