Collector / Drag Strut Axial Force (ASCE 7 12.10)
Axial force in a collector that drags diaphragm shear back to the shear wall.
Example
You enter
- Diaphragm unit shear v (plf) 300
- Collector length to wall Lc (ft) 40
- Overstrength factor Omega0 (1.0 to skip) 2.5
You get
- Collector force (strength level) 12,000 lb axial
- Collector force omega (lb) 30000
Checked against published worked examples from: ASCE 7-22 Section 12.10 (collectors and drag struts).
Details, formula, and sources
ScopeThe accumulated axial force in a collector (drag strut) that gathers diaphragm shear across an opening and drags it back to the shear wall: collector_force = unit_shear x collector_length, plus the ASCE 7 12.10.2.1 Omega0 overstrength demand the diaphragm chord never carries. The separate load path a diaphragm shear check leaves out.
Formula or tablecollector_force = unit_shear x collector_length; collector_force_omega = Omega0 x collector_force.
Source and editionThe ASCE 7-22 Section 12.10.1 / 12.10.2 collector (drag strut) axial force and the 12.10.2.1 overstrength demand, by name.
Free accessASCE 7 is available through the ASCE Library at ascelibrary.org; the Section 12.10 collector provisions are public.
What governsEstimate. AHJ and licensed professional govern.
API field namesunit_shear_plf, collector_len_ft, omega0, collector_force_lb, collector_force_omega_lb
- Accumulated force collector_force = unit_shear x collector_length, peaking at the resisting wallASCE 7-22 12.10.1
- Overstrength Section 12.10.2.1 requires Omega0 amplification for the collector and its connections in the applicable SDCsASCE 7-22 12.10.2.1