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Note that the loadings below are only applied when users choose to perform “Detailed” Structural and Geotechnical optimization.

Dead Loads (D)

Include PV Panel weights plus the self-weights of various components that comprise the structure. Dead loads are applied along the rake length of Array surfaces (i.e. as a downward load along the slope).


HST Defaults:

1- Panel weights = 3 psf


Wind Loads (W)

Calculated in accordance with the provisions of ASCE 7-10, Section 27.4.3, Main Wind Force-Resisting System (Directional Procedure) for Open Structures with Monoslope “PV Panel” Roofs. Wind loads are applied normal (perpendicular) to array surfaces.


HST Defaults:

1- Kd = Wind Directionality Factor = 0.85

2- Kz = Velocity Pressure Exposure Coefficient at height z = 0.85

3- KZT = Topographic Factor = 1.0

4- G, Gust Effect Factor = 0.85


Seismic loads (E)

Calculated in accordance with the requirements of ASCE 7-10, Chapters 12.4 and 12.8. Both lateral and vertical components of the seismic loads are determined.


HST Defaults:

1- Ip = 1.0 Component importance factor

2- Rp= 1.25 Component response modification factor


Snow loads (S)

Calculated in accordance with the requirements of ASCE 7-10, Chapter 7. Snow loads are applied to the horizontal projection of array surfaces.


HST Defaults:

1- Ce = 0.9 (using Terrain Category C and Fully Exposed Exposure).

2- Ct = 1.2 (Using unheated and open air structures).

3- Is = 1.0 (Using Risk Category II).


Combinations of Loads

Determined in the previous sections will be considered to act on racking structures and foundation elements using Allowable Stress Design combinations of ASCE 7-10, Section 2.4.1.


  1. D
  2. D + S
  3. D + 0.75S
  4. D + 0.6W
  5. D + 0.7E
  6. D + 0.75(0.6W) + 0.75S
  7. D + 0.75(0.7E) + 0.75S
  8. 0.6D + 0.6W
  9. 0.6D + 0.7E
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