Engineering problem...no...problem with engineers

I'm planning to build a hybrid house near the coast in an area where we have more than our share of hurricanes. (five in three seasons) I want a structure that is immune to any contingency. Even though I'm not in any flood hazard area the house will be well elevated. The foundation and major structural components are large, round timbers (poles). The poles transfer all loads deep into the ground. There are no load bearing walls.

The problem is, how and where to find a structural engineer who has a clue about construction with large timber members and pole frames. It seems the local field of expertise deals only in massive concrete and easily replaceable stick-framed blow-through wonders. When I mention pole frames and beams with deflection limits in excess of L/900, etc., I just get blank, slack-jawed stares and stupid comments like "We only design for L/360 'round heah."

Any tips on how to obtain decent uplift-wind load analyses from wizards like this? I need a structural analysis and approval to get a building permit but it seems somewhat hollow if I have to learn to do all the engineering so I can instruct the engineer in how to do the engineering that I have to pay him to do for me so I can get a permit to build my house.

Any ideas gratefully accepted.
Don

Don, where exactly are you building? Also, h/900 is a very strict limit and I assume you are refering to story drift. AISC (the American Institute for Steel Construction) recommends h/400 for story drift in steel framed buildings. Story drift limits more strict than this are usually based on glazing system criteria not found in the typical residence. h/900 is equivalent to 1/8 of an inch drift on a 10' tall story.

Hi Chris. I'm building in Lower Alabama, near Pensacola, about 25 miles upriver from the coast.
L/900, not h/900. I'm referring to deflection of wood beams. Code specifies a maximum deflection of L/360 which is allows a deflection of 1/360th of the span. For instance, a 20' beam loaded to 60# plf at L/360 would have an allowable deflection of 0.667". The same beam at L/900 has a maximum deflection of only 0.287". I'm designing this house to be much stronger than code requires. This is last house I expect to build.
Code is quite inadequate, if you ask me. For instance, designing for 15 lb. psf roof live load meets code. I believe that a 125 mph hurricane wind with a duration of a very long time (seems like forever) will load a structure far beyond code requirements.

I think that an L/900 designed structure will still fail in a hurricane if it is subject to the sort of domino failures that destroy most buildings in such storms; a wind driven projectile penetrates a window, shutter or sheathing and lets wind and water into the building. The resultant wind lift on internal floors and walls causes failures of the framing connections. Consider that a 100 MPH wind represents a force of 25 lb/sqft. and that this force grows as the square of the wind velocity and you can see how wind can destroy about anything if it gets in the wrong place.

In other words, I think that storm resistance is a complicated equation of structural strengths and frame stiffness is only one of them.

Duh?? Of course, ultimate wind resistance is not contingent upon frame stiffness...just as frame stiffness has absolutely no relevance to my original question posed to this forum.

Chris/Brian, your replies provide PERFECT illustration of my problem with engineers. I mentioned deflection limits only as a means of showing a local engineer's inability to comprehend and provide relevant information. To this I receive a reply providing info on story drift in skyscrapers. So I explain about deflection limits and receive an opinion that a stiff building will still fail in a hurricane. I do appreciate that bit of wisdom, but it doesn't require a rocket scientist (or a structural engineer) to figure that one out. I'm well aware of factors that make buildings fail but that isn't my concern here. I guess I have my answer. Thanks anyway, guys.
Don

Don, If you do not think your local building code is adequate try looking into one of the model building codes such as the Southern Building Code or ASCE-7. No local building code will prevent you from building something stronger than it requires.
The AF&PA publishes the "Wood Frame Construction Manual for One- and Two-Family Dwellings, 1995 High Wind Edition" which is not too technical, because even I, an engineer, can understand it.
FEMA publishes the "Coastal Construction Manual" which is a little out-dated but very helpful with structures elevated on piles, (it is also free.)
In the investegations of failures caused by Hurricane Andrew, most of the buildings that were built under current codes, failed due to poor workmanship rather than because of inadequacies in the code.
I would use the Southern Building Code and if you feel it is necessary factor the loads up to a higher confidence level, (a 100 year storm rather than 50 or 75). Also I would pay very close attention to uplift resistance and tying all elements down in a continuous load path to the foundation.
There is an old dutch saying that says "If you have 10 dollars to spend on planting a tree, spend 2 on the tree and 8 on the hole."
When building in a hurricane region I would modify the saying as such: "If you have 10 dollars to spend on a structure, spend 2 on the lumber and 8 on Simpson connectors."

You have to remember that it is the 97% of engineers who give the rest a bad name.


Sorry Guys could not resist sticking my nose in.

By the way have you noticed that the timber engineering topic is the most active active in this section forum ??
What does this say?

Bill

[This message has been edited by Bill Keir (edited 04-29-99).]

Don,

Harking back to your original question, there are plenty of Guild members who could help you design a frame to your spec, but the crux seems to be that you need a PE stamp on your plans and are hunting for an experienced timber engineer registered in Alabama. I am sure you can appreciate that Guild cannot be in the referral business when it means recommending one member over another. However this seems not to be a problem in your part of the world.

I suggest the following:

1. Check the Guild roster for fellow Alabamians and see if any of them has a working relationship with an Alabama PE.

2. Post your question on the Guild Guestbook (http://www.tfguild.org/guestbook.html) and also at the TFG Bulletin Board (http://www.tfguild.org/wwwboard/wwwboard.html) in the hope that a bigger net may catch more fish.

Don't know a candidate myself, but am checking with several timber engineers of my acquaintance to see if one of them can recommend someone with an Alabama stamp.

Good luck,

Ed


[This message has been edited by Ed Levin (edited 04-29-99).]

THANK YOU!!!

I have really enjoyed reading this topic! So I'll add my 2 cents worth, even though it is late. I can't beleive that any structural engineer in Alabama would have difficulty designing based on stricter deflection limits. (My folks live there and I did for a couple of years). I think the strange look they seem to have is that they're trying to comprehend why. Deflection frequently controls design, but not because deflection will cause failure, but b/c it is a servicability criteria. Excessive defl. causes user discomfort, or poor performance of mechanical equipment. Some of the "strongest" structures are extremely flexible.