Diaphragm Basics - The Analysis of Irregular Shaped Structures - page 39

2.5 Drag Struts and Collectors

Code defines a drag strut as a diaphragm boundary element parallel to the applied load
that collects and transfers diaphragm shear forces to the vertical elements of the lateral-
force-resisting system or distributes forces within the diaphragm. For a collector, code
refers to the definition of a drag strut. Figure 2.14 shows a typical arrangement of struts,
collectors, and chords. The figure has been included to provide clarity and consistency
in the terminology used in the examples of this topic. A strut and a collector perform the
same function and are typically considered to be the same thing. The author's prefer-
ence is to label a strut as a member that collects shears from one side only. A collector is
a member that collects shears from both sides. The role these members play under
transverse and longitudinal loading is shown in the figure. For transverse loading, the
members along grid lines 2 and 3 receive shears on both sides of the members and there-
fore can be classified as collectors. The disrupted chord at grid line 2B is extended into
transfer diaphragm TD1 which transfers its disrupted force out to grid lines A and C.
Shears are applied on both sides of this member, which makes it a collector. The bound-
ary member coming off of the shear wall on grid line 1 receives shears from one side

F i g u r e 2.14 Strut, collector, and chord terminology.