Engineering Question

[Alan D. Hyde]

A mast is a pole, a column braced by stays, and succesfully takes many shocks from the interaction of wind and waves pushing on a boat.

Some of us Midwesterners live near the New Madrid fault, which hasn't produced a serious quake for about one hundred years. It's claimed that we're about due for one.

If I build a boatshop using pole barn style construction methods, will that hold up well in a quake? From the analogy to a mast, it seems like properly sized and braced poles should do well, but I haven't found any discussion of this in the several pole barns books I have, or anywhere else so far.

Any thoughts on this from an engineering or experience (Californian?) perspective?

Alan

[TomRobb]

I'm not an engineer so MHO is worth what you paid... but I'd have supposed that tornados are more of a clear and present danger than 'quakes. Any structure that can stand up to a twister shouldn't be too much bothered by the Richter 1s and 3s we regularly get.
The number and quality of your fastenings and attention to detail may be the most telling variable.

[Alan D. Hyde]

Tom, you're right that there are more tornadoes around here than there are quakes. Tornadoes, however, are not like hurricanes: they don't typically cover a wide area. They kind of bounce along, changing altitude, touching ground more or less each time they land. Their horizontal paths are erratic.

The swath cut on the landscape is therefore variable. In some places they do little or no harm; in others, the destruction is fifty to one hundred feet wide or more. They're accompanied by an eerie greenish-yellow light, and remarkable thunderstorms. Quite a show!

As a boy, I watched one take the roof off a neighbor's house about two blocks away. I was looking around the trunk of a swamp oak tree in our front lawn. I held onto it with my hands, steadying myself. Later I noticed small black spots on my hands, kind of like small blackheads. Small bits of sand were embedded in my skin.

I don't think the power of a direct tornado hit can be withstood by any large structure that I can afford to build. But I do think I can make it strong enough that it would take a direct hit to do substantial damage. I just don't think the odds of a direct hit are very great.

An earthquake, though, is an unknown to me. And not (around here) covered by insurance, either.

Alan

[ 04-30-2002, 02:26 PM: Message edited by: Alan D. Hyde ]

[Dave Fleming]

Alan, look at these sites for a background in pole structures.
I live in earthquake country and when I build again I am going to use design techniques similar to what these folks use.

http://www.rl-intl.com/index-1.htm
http://www.kokorocountryhouse.qpg.com/index.htm

Hmm, there seems to be some changes in that second URL but if you enter Kokoro Country House in a search engine something should come up.
:confused:

[ 04-30-2002, 02:35 PM: Message edited by: Dave Fleming ]

[Donn]

Pole construction is extremely resistant to damage from seismic activity. Unless you are precisely on a faultline, the chance of earth rupture is slim, and earthquake damage would stem from either ground-shaking, or another structure falling on yours.

Wood construction has always been superior to rigid masonry in resistance to damage from ground shaking, and many feel that pole construction is among the most flexible technique. The elimination of the rigid masonry foundation in other types of wood construction, removes the most dangerous effect of ground-shaking. Look at the pier that each pole is mounted on as an individual foundation, isolated from the others by earth, and tied together with a flexing framework of poles, crossmembers and sheathing.

Here are several references:

"I chose pole-barn-type or post-frame construction for many reasons. This style is easily adaptable to the most difficult sites: steep hills, rocky soils, marshy or floodland areas, sand beaches, hurricane or earthquake zones."

planet earth home
The complete reference book for new self-sufficient homes
By Mel Moench

http://www.planetearthhome.com/tour/two.html

= = = = =

"Those Magificent Poles
Beyond the great strength and beauty of the Japanese Country House's visual presentation, the poles themselves are fundamental to a solid structural system... indeed, one of the strongest known.

The entire house is integral to the vertical, round columns, thereby demonstrating its versatility as well as stability against a battery of natural forces. A brief review of the facts will demonstrate the good sense of poles.

The familiar wooden posts of 'pier and dock pilings' provide the foundation of a Japanese Country House.The 16-inch diameter poles are stronger, pound-for-pound than steel. Like their cousins at the wharf, they resist both hurricane-force winds and catastrophic seismic activity."

much more at:

http://www.rl-intl.com/exterior.html

= = = = =

http://www.woodengineering.com/

= = = = =

Peace of Mind in Earthquake Counry
By Peter Yanev, 1974. Chronicle Books, San Francisco, CA. The history and causes of earthquakes, what the home buyer should look for and what the homeowner can do.

Out of print...try the library, or ABE

= = = = =

http://www.vch.com.au/systems/stumped.html

[ 04-30-2002, 02:53 PM: Message edited by: donnwest ]

[Alan D. Hyde]

Thanks for the great posts, Dave and Donn.

I've thought of building not only a boat shop but also a house this way. Now I'm even more inclined to do so.

Isn't this a remarkable Forum?

Alan

[Vern D]

Alan. I built Timber Frame homes for 8 years here on the left coast. Here are a few things I learned while building here, where the earthquake hazard zone is high.
1.Tie the building down to the foundation. In the case of pole building, the poles are buried deep so that is the same effect.
2. In timber framing the rule of thumb for braces is that the length of the brace should be about 1/3 the length on the post you are bracing. The longer the brace, the better.
3. in My opinion, Braces are better than shear walls.
Good luck with the "big one"
:D
Vern and Jake (the wonder dog)

[gary porter]

Alan, Seismic considerations are a big deal up here. Pole barn construction and timber frame are common and considered structurally stable. I can get you information on details and considerations if you really decide on going that way. I work with the engineers here that make earthquake designs as well as permafrost designs their forte.
Another consideration as far as a house and timber frame construction is concerned is fire. There are some incredible stories and documentation on the structural ability of timberframe to withstand fire as well as the cost to recover if a fire does occur. Its quite impressive. I've seen pictures of a very hot hanger fire where steel beams are laying bent over chared wooden beams that are still holding. I'm originally from Indiana and I'd say don't worry about the quakes just don't build too near a trailer park.....Gary Porter ;)

[Dave Fleming]

Vern, I agree just as long as the brace angle is as close to 45 degrees as possible.
Yeah a shear wall in big timber framing to really be effective would probably use 1 inch ply!
I can't grasp the use of SIPS with big wire nails for fastening???
:confused:

[Dave Fleming]

Gary, I recall when I had to go to 'uptown apprentice' classes in San Francisco because there were no boatbuilding apprentice classes. We had a presentatio one night from a glue lam company. Showed a few photos as you describe. One was the big theatre at Wolf Trap showing the steel purlins draped over the glue lam beams.
IIRC, solid wood chars and then burns at the rate of 1 inch and hour in a household fire, about 1500 to 2500 degrees. It is the char that actually protects and to some degree insulates the underlying wood from the flames.
Or so I recall.
;)

[John Gearing]

I lived for 11 years in the heart of Silicon Valley, just a few miles from the San Andreas fault, and rode out the Loma Prieta quake of 1989 on the top floor of a big 5-story office building. That was quite an experience. As for the house, it came through with flying colors. The only damage we had was from a drinking glass that slid off the counter and fell into the sink and broke. Common practice in houses there is to make sure they are well-fastened mechancically to their foundations. Very few houses had basements. From a design standpoint, it was the houses in the marina district of San Francsico that fared the worst. There, the houses were built with the first floor being used for the garage (again, no basement) with the living spaces on the second and third floors. Because of that, they really only had a three-sided foundation, and when the big one hit, they collapsed. One of the major dangers to houses in an earthquake is fire starting when gas lines rupture. Because gas hot water heaters can fall over and break their gas lines, it's standard practice to strap your gas hot water heater to the wall of your house using some pretty hefty lag screws, for example.

Donnwest is right that it's unsupported masonry that tends to get hammered by earthquakes. But overall, I was surprised at the relatively small amount of damage suffered in the Bay Area when the Loma Prieta hit. Collapsed bridges, elevated thruways, and old churches took a lot more damage than any private homes I knew of. I wouldn't go so far as to say that you have to build pole-frame style to be safe from earthquakes, but based on the info others have provided here they would appear to be plenty safe if you did choose to go that route.

[Dave Fleming]

I rode out the Loma Prieta 'shake' in the In-Laws house in Pinole.
That big chandalier(sp) was swaying all over the place but the house relatively new and with tie rods running from footings up through roof plate did just fine. The gas water heater was anchored to the wall studs but the pilot light blew out, now ain' that interesting.
I just like the idea of a Timber Frame structure or a Pole type ain't touting one nor 'tother over proper stick framing in earth quake country. Now hurricanes or tornados are something else yet again. Different set of problems as I see it.

As far as the Marina District is concerned I agree lack of good foundations is the major cause BUT, being built on fill didn't help the situation either.
Seen too many documentaries showing how the earth moves and the water collects in along shore, river type earthquake situations. Turns the soil to jello. Yanev in his book recounts the effect that had on the Santa Rosa area in the 1906 quake, damn near wiped the town out! Seeing as it is built on an old river bed or some fancy scientific name like alluvial( ? )plain.

Remember living in El Sobrante just down stream from an earthen fill dam, the San Pablo Dam, with a big body of water behind it. Glad we moved and that was the first thing I was looking for info about after LP hit. But I guess nothing happened or the powers that be were able to keep it quiet if it did.
Couldn't believe my eyes when on the news they showed that section of Bayshore freeway collapsed and the Bay Bridge with the out of kilter section. Again couldn't believe that that old Smith Rice Steam Crane was still in operation. That thing must be as old as I am!
;)

[ 05-03-2002, 11:41 AM: Message edited by: Dave Fleming ]

[reddog]

Interesting;
After the quake in Kobe(?),Japan they found that the major damage was to the timber framed structures traditional to that country.Many just collapsed.Oddly enough the newer buildings that were stick framed a la North American techniques fared better.In the rebuilding they actually imported carpenters from NA to teach them how to stick frame,(a couple of guys I worked with did a few "tours").

[Bruce Hooke]

You should be able to get an earthquake rider on your insurance in Indiana. I had one when I lived in Kansas City and I have one now here in Rhode Island. Granted I'm a renter so all I have is "Tenants Insurance" but I can't imagine that they would offer earthquake riders on tenants insurance and not on homeowners insurance. To me earthquakes are exactly what insurance should be used for -- to cover a very unlikely but potentially very large loss (especially here in New England where there are lots of old houses on old brick and stone foundations!). For what it's worth my insurance both here and in Kansas City has been through AMICA, which is a nationwide company...

[Vern D]

One year at a Timber Framers Guild conference, there was a seminar on Earthquakes, specificly, how a frame had fared in the Loma Prieta quake.
The frame was up, the second floor had the floor decking loaded and stacked. Approx size was 30'x40' if I remember, regular poured foundation with the Frame secured with standard Simpson hardware. Location, approx 25 miles from epicenter.
When the quake hit it was estimated that the actual ground amplitude was at least 4 feet.
The ONLY damage to the frame was that as the frame racked, the pegs securing the braces acted as wedges and split the braces in line with the pegs. Now this with just a bare frame and a huge load upstairs due to the decking. At some point, the elevation on one end of the house was at LEAST 4 feet different than the other. WOAHHHHH!
I built a house across Hwy 101 from the ocean near here. It lies face on to the direction of our winter storms. The house has a huge face as well as a 4 ft clearstory wall.
After the first nasty storm, gusting to 100KTS, the owners said they never felt safer. He said the house was talking all night. He could sense the frame deflecting and returning. No Damage of course.
As far as SIP's, they have NO shear value. The frame MUST be designed as a whole. No help from anything else. SIP's are pretty expensive as far as I'm concerned, though save quite a bit of time. When I eventually build my T.F. home, doing my own work ("free labor"), I think I'll be looking at either wood or metal stud framing, with wider plates and staggered studs.
:D
Vern and Jake (the wonder dog)

[PugetSound]

In the 1993 ('92?) Northridge/Los Angeles Earthquake (a 7.2 on the quake scale I believe), the most common damage to peoples homes was when the brick chimneys broke loose and fell thru the roof. Some 2/3 of all the houses in my mother's neighborhood of Granada Hills (some 5 miles from the epicenter) lost their chimneys. Virtually everyone lost the flex-hose connection on their hot water heaters. about 1/3 of all the homes moved off of their foundations (even though they were tied down.

Basically, a well anchored and well braced wood structure will do OK in an earthquake but you have to understand that you can only do so much to prepare. After that, when the big one does come, just hang on and enjoy the ride!!! (and yes, I was in the Loma Prieta quake - Vallejo - and the Newhall Saugus/Los Angeles quake and a host of others too small to really bother with -i.e. 5.0 and below).