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GSBN:Compression & bumble bees



Hi Barbara, John, Rene...and all...

  perhaps you remember, only few weeks ago I explained  that we tried a different system to build a Nebraska-style-home...so - of course- we now have problems.
  On top of the walls (house aprox. 5m wide x 13.5m long) we placed two huge wood panels (flat roof). Each panel 1700kg, total load 3400kg. We wanted to try not to use a ring-beam and use this huge panels as ring-beam and compress with them afterwards...so, now the load is too little and the load is "too well spreaded"...only 2cm of compression and the walls move and don't give a very "nice feeling". Now the idea was eventually to compress with a crane and fix all with the "plastic-belts" (sorry, I don't know the English name).Does anybody know which is the force you need to compress a wall this 6% you recommend?) If you think it's crazy to do it with a crane, please, we're open to every suggestion!!!

  If not, perhaps we try it with truckload belts with spanners fixed to the  panels and the...if not,  perhaps we need to take away the panels, build a ring-beam and pre-compress the walls and place again the panels.

  Thanks again for all your help,

  Maren


Rene Dalmeijer rene.dalmeijer@... escribi?:  John, Barbara,

I wish to set things right before you all get a completely wrong idea
of the German tests. Basically what the German tests have tried to
determine is the maximum load you can apply to a bale either 2 string
or Jumbo. The reason for these tests is that the current codes in
Germany will not accept a load bearing SB building based on a plastered
SB sandwich ie bare bales should be able to carry the load all on their
own. Off course we and the testers know that the plasters carry most of
the loads.

What the tests have shown me so far is that bare bales can carry
immense loads 30t for a single 2 string bale.
That bales in a wall work better then on their own because they but
against each other.
That bales placed on their side are stronger/stiffer then layed flat.
And quite a few other aspects that I will await the final outcome of
the tests.
To put things right these tests are not silly we will now know better
what the mechanical properties are of bare bales and which aspects are
of influence on these properties.

Rene
On Aug 22, 2006, at 18:28, John Swearingen wrote:

> Ahhh, compression....the squishing of bales. 30%????!!!!
>
> Barbara's observations concur with everything I've heard, seen and
> measured
> from the field--around 3-6% squishing under gravity loads (depending
> upon
> the quality of bales), most of it happening in the first weeks. With
> our
> Kalifornia Terminator Bales (TM), we have to work really hard to get
> 2%,
> using jacks and levers. This is commonly called compression, but I
> would
> suggest that the bales are already quite compressed when we put them
> in the
> walls. It appears self-evident to me, that the majority of this
> "creep" has
> to do with the bales settling in to one another, rather than squishing.
> This is an important distinction.
>
> Thirty percent compression, as the German Scientists suggest,
> is....well,
> Barbara said it politely: "I think it is always useful when conducting
> research in laboratory conditions to check in with what happens in
> practice
> as well."
>
> About plaster, Barbara went on, "A useful observation from the German
> tests
> however is that load bearing bale walls do not require plaster in
> order to
> make them structurally strong, which should add to the debate in the
> US on
> this subject." That the bales would work without plaster isn't in
> dispute,
> but nobody has suggested, except for a few of us after a long day and a
> couple of beers, to forget about the plaster altogether.
>
> And since it's there, the plaster might as well work. Compression
> loads will
> travel to the stiffest element. In the case of our bodies, it's our
> bones
> (endoskeleton) that are stiffer than muscles and skin, and so we don't
> collapse, even when jumping off of bale walls. In the case of a
> plastered
> bale wall, the plaster skins are stiffer than the bales, and so they
> take
> the load FIRST. If the load exceeds the capacity of the skins, the
> skins
> crack (bones break), and the load is then taken by the bales which, we
> are
> reassured by German Scientists, they will do very nicely.
>
> In earthquake country, we figure that skins will take most seismic
> events
> without too much damage, but in a catastrophic quake will become
> useless
> before the quake is finished--at which point the bales will bounce
> around
> but not break. The plaster, being stiffer than bales, keeps your
> windows
> from breaking every time the ground quivers.
>
> Note: in order for this to work most effectively, the plaster skins
> would
> rest on the foundation (rather than hang in air). This is more true in
> theory than practice, I think, because in reality the loads seem to
> transfer
> in and out between the skin and bales.
>
> The question of plaster skins isn't one only of gravity loads, however.
> Walls also bend and stretch apart (in the wind and earthquakes), and
> bales
> don't do very well when pulled upon. In that case the other element of
> plaster skins, lathing, can be very important. By surrounding the
> bales with
> a basket of mesh the walls are held together, and loads which develop
> in
> tension are confined and brought back into the bale walls, in
> compression.
> This is a Very Good Thing, and allows the bumble bee bales to fly like
> an
> eagle. It is also a subject of debate, because lathing costs (a
> little)
> money and trouble, and because if it's METAL lathing, it might turn the
> occupants into electro-jellyfish due to EMF, which would be a Very Bad
> Thing.
>
> John "Squish me in the Moonlight" Swearingen
>
>
> John Swearingen
> SKILLFUL MEANS
> design and construction
> www.skillful-means.com
>
>
> -----Original Message-----
> From: GSBN [<a  target="_blank" href="mailto:GSBN@...";>mailto:GSBN@...] On Behalf Of
> Strawbalefutures
> Sent: Tuesday, August 22, 2006 2:42 AM
> To: GSBN
> Subject: RE: GSBN:Compression &amp; bumble bees
>
>
> Hi Maren
> It has to be made clear that the tests done in Germany showing the
> need for
> so much pre-compression (30%) are not borne out in practice. They are
> very
> interesting results and we need to understand them, but we have built
> a 2
> storey loadbearing house that remained unplastered over the winter -
> that
> is, had it's full load on the walls for several months - and the
> maximum
> compression we had on the ground floor walls was 6%. We know from many
> practical experiences that loadbearing walls do compress a certain
> amount
> under their full loading, that most of this happens in the first 2
> weeks,
> and that it has virtually stopped by 6 weeks. On top of this, there is
> the
> effect of plaster on the walls, which definitely has an effect to
> reduce the
> amount of compression experienced if it is applied before the 6 week
> period
> is over.
>
> A useful observation from the German tests however is that loadbearing
> bale
> walls do not require plaster in order to make them structurally strong,
> which should add to the debate in the US on this subject.
>
> I think it is always useful when conducting research in laboratory
> conditions to check in with what happens in practice as well. Hence the
> inability of the bumble bee to fly analogy.
>
> Best wishes
> Barbara
>
>
>
>
> WARNING: Strawbale building can seriously transform your life!
>
> Amazon Nails
> Strawbale Building, Training and Consultancy
> Hollinroyd Farm
> Todmorden
> OL14 8RJ
>
> Tel/fax: 00 44 (0)1706 814696
> email: info@...
> web: www.strawbalefutures.org.uk
>
>
> -----Original Message-----
> From: GSBN [<a  target="_blank" href="mailto:GSBN@...]On";>mailto:GSBN@...]On</a> Behalf Of Rene
> Dalmeijer
> Sent: 22 August 2006 09:15
> To: GSBN
> Subject: Re: GSBN:Compression
>
> Maren,
>
> I just visited the FASBA (German SB association) gathering in
> Walthershausen
> where 2 presenters focussed on this subject based on laboratory testing
> trying to determine how much pre-tension is required to avoid creep
> with
> unplastered bales. Basically what it boils down to is that you need
> 30% pre
> compression on 100kg/m^3 dry density bales. ie practically impossible.
> At
> the same time though I must clearly state that the tests being done
> are very
> useful and will give us some very useful data on the behavior of
> unplastered
> 2 string and Jumbo bales.
>
> John Zahng of Australia has done similar plastered full wall tests and
> found
> that about 4% pre-compression is required to avoid initial creep. This
> figure roughly corresponds to what has been found in practice to be the
> right amount of pre-compression. Incidentally the force-deflection
> curves
> presented at the Fasba gathering exhibited the same flow as those
> found by
> John Zahng.
>
> Rene
> On Aug 22, 2006, at 06:54, Maren Termens wrote:
>
>> Hi all,
>>
>> does somebody know which pressure per area it's needed to compress
>> Nebraska-walls? Or can you tell me which pressure are you normally
>> using? I'm looking after essays and tests which work with this item, I
>> couldn't find technical information about that.
>> Thanks a lot.
>>
>> Maren
>>
>>
>> ---------------------------------
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