Wood is a living organism. The tissue that connects the cells functions as a structure that absorbs vibration, it also has non-uniform characteristics.
6m-timber's bottoms are fixed on steel base plates. Relying on their elasticity and stability, they are twisted and bolted together. By the generation of this internal-stress, sagging is prevented. The general method to increase rigidity is to ”pull" both-ends, but "twist" here.
So, we're "braiding" timbers rather than "building" with it. Braiding as a primitive method has load-balancing characteristics that caused by friction and tension.