Abstract
In this report, I propose one practical calculating method for the wooden lattice girders with throughing booms:- 1st-decide the max, deflection of the girder. 2nd-take consider on only its booms, and calcutate the loads (P_γ') that let the booms bend to the decided deflection. Here P_γ'=α・P_γ α=const, P_γ=bearing load. 3rd-check P_γ exceed the boom's bearing power or not. 4th-reduce the P_γ' from the P_γ P_γ-P_γ'=P_γ(1+α)=P_γ" 5th-with the P_γ", design the lattice girder as ordinary pin panel point truss, limitted in the decided deflection using following formula [numerical formula] N": stress of members caused by P_γ" N: virtual stress ε: axial strain of joints of lattice work. And I show follows:- The reduction of bearing power of wooden lattice girder calculated as ideal truss, is depend on the secondary stress grow in the panel points of the boom throughing panel to next panel. Exceeding secondary stress is secondary moment caused by beam's deflction. That means, if wooden lattice girders are designed very rigid and have thin booms (flexiable chord to the beams deformation), the reduction of bearing power of beams would be minimized. These were proofed by the experimentation.
