English to Russian Tech/Engineering Construction / Civil Engineering scaffolding

Bracing:
Bracing shall be in the form of ledger or cross bracing and longitudinal or facade bracing.
Ledger bracing shall be positioned at alternative standards in a scaffold and each brace shall run from a ledger in one lift to the diagonally opposite ledger the lift above.
Longitudinal bracing shall be in the form of a zig-zag arrangement of tubes running from the bottom to the top of the scaffold between a pair of adjacent standards.
Or
A continuous tube running from the bottom to the top of the scaffold at an angle ofbetween 35° and 55° to the horizontal.
Or
Individual tubes running from the bottom to the top of the scaffold between a pairof adjacent standards, all sloping the same way
*****Bracing assemblies***** shall be fixed along the face of the scaffold at intervals not exceeding 30m.

http://htmlimg3.scribdassets.com/1rpaeomvi8mdsih/images/25-0... - это facade (longitudinal) bracing
(т.е. вдоль стены здания)

http://htmlimg4.scribdassets.com/1rpaeomvi8mdsih/images/26-2... - cross (ledger) bracing, т.е. под угломи 90 градусов к стене.

Вопрос: что же такое braces assemblies? и почему их необходимо располагать через не более чем каждые 30 метров вдоль стены здания?

Спасибо!