--archimedes leveraged( vaulted) roof system--

the concept--

    i was scribbling on the public dry-erase board, at a very nice coffee shop, in the downtown area today...here are my thoughts, and a few numbers to "roll around"--


    i noticed this morning, that a roof can hold twice the weight, if the "roof-face" on each side, has a "fulcrum point" closer to the top of the wall that the eves of the roof sit upon...in this way, the usual "a-frame" can be "cantilevered", in a sense( diagram soon to uploaded), the concept is based on the premise that, each "fulcrum-point" before the "base" of the roof, divides the downward force, by 2, on each side of the roof( on each "roof-face"), this reduces the force, trying to spread the top of the 4 walls of the structure( a small shed for example), resulting in the collapse of the structure, into itself--

   if a shed has 200 pounds of weight( the roof materials), against the walls it sits on, 200 is divided by 2( and 100 is the resulting value), to each side of the roof...at the point of the usual "a-frame" cross-beam, the force is also divided by two, one force going down to the foundation, and one going at 90 degrees away from the center of the "a-frame" of the roof( see diagram)--

note--

   if we view the physical results of this building style, the way the weight is managed becomes more obvious...it's like having a traditional roof, on top of another roof, with a steeper pitch, the top has a traditional "a-frame" shape, and only the weight above the cross-bar of the top "a-frame" is relative to this first "a-frame", in the roof structure...allowing it to reduce the spreading loads below it, while still handling the weight of the entire roof, even though it's splitting the load with the steeper pitched "a-frame" portion, at the lower part of the roof...also, the lower spars go from the center of the upper cross-bar of the top "a-frame" of the roof, and this centers the load, on each side of the roof, that's trying to spread away from the center of the structure( "cantilevered" )...this puts the load of the lower roof in the center of the top "a-frame" of the roof...and also moves roof loads, to the areas that the roof sits on( the walls)...

   this amount, is the force trying to "flatten the building"( 50 is this value), this concept explains the effectiveness, and dynamics, of "flying-buttresses" utilized in Europe long ago, for the building of structures( churches), with "vaulted-ceilings", which had to overcome engineering issues regarding their surface-area/weight ratio, and the need for the structure to stand, while delivering the desired volume within( essentially, these "buttresses" were on the outside of the structure, resisting the pressures of the roof wanting to spread the walls, from a force-vector that was pushing down, and away...not directly down, on the roof's supporting walls...this allowed the removal of the traditional cross-bar of a roof's upper "a-frame" structure, due to the "flying buttresses" presence handling the weight, in their absence)--


best wishes, john kruschke--