Ice Loading Analysis (for C & MC Shapes)

Per ASCE 7-05 Code - Chapter 10
for Ice Loads Due to Freezing Rain on C and MC Shapes

Input Data

Member Size =    
Building Classification = [?]   Table 1-1, page 3
Nominal Ice Thickness, ti = in. Figures 10-2 through 10-6, pages 104-108
Topographic Factor, Kzt = [?]   Section 6.5.7 & Figure 6-4
Height Above Ground, z = ft.  

Result Data

Member Properties for :
Depth, d = in.  
Web Thickness, tw = in.  
Flange Width, bf = in.  
Flange Thickness, tf = in.  
 
Design Parameters:
Importance Factor, Ii =   Table 10-1
Ice Height Factor, fz =   If  0 < z <= 900, then fz = (z/33)^(0.10), else fz = 1.4
Design Ice Thickness, td = in. td = 2.0*ti*Ii*fz*(Kzt)^(0.35)
Density of Ice, Id = pcf Id = density of ice (assumed = 56 pcf)
Weight of Ice (for td), Wi = psf Wi = (td/12)*Id
 
Ice Load Based on Circumsribing Diameter of Member per Code:
Circumscribing Dia., Dc = in. Dc = SQRT(d^2+bf^2)
Area of Ice (for td), Ai = in.^2 Ai = p*td*(Dc+td)
Unif. Distributed Ice Load, wi = plf wi = (Ai/144)*Id
   
Ice Load Based on Perimeter of Member: (for comparison purposes)
Perimeter, Pm = in. Pm = 2*((d+td)+2*(bf+td)-(tw+td))
Unif. Distributed Ice Load, wi = plf wi = (Pm/12)*Wi

Nomenclature

x
TABLE 1-1
Occupancy Category of Buildings and Other Structures for Flood, Wind, Snow, Earthquake, and Ice Loads
Nature of Occupancy
Occupancy Category
Buildings and structures that represent a low hazard to human life in the event of failure including, but not limited to:
- Agriculture facilities
- Certain temporary facilities
- Minor storage facilities
I
Buildings and other structures except those listed in Categories I, III and IV II
Buildings and other structures that represent a substantial hazard to human life in the event of failure including, but not limited to:
- Buildings and other structures where more than 300 people congregate in one area
- Buildings and other structures with day-care facilities with capacity greater than 150
- Elementary or secondary school facilities with capacity greater than 250
- Colleges & adult education facilities with a capacity greater than 500
- Health care facilities with a capacity greater than 50 resident patients but not having surgery or emergency treatment facilities
- Jails and detention facilities
Buildings and other structures, not includes in Occupancy Category IV, with potential to cause substantial economic impact and/or mass disruption of day-to-day civilian life in event of failure, including, but not limited to:
- Power generating stations, water treatment facilities, sewage treatment facilities, and telecommunication centers
- Buildings and structures not included in Category IV containing sufficient quantities of toxic, explosive, or other hazardous materials dangerous to the public if released
III
Buildings and other structures designated as essential facilities including, but not limited to:
- Hospitals and health care facilities having surgery or emergency treatment facilities
- Fire, rescue and police stations and emergency vehicle garages
- Designated earthquake, hurricane or other emergency shelters
- Designated emergency preparedness, communication, and operation centers and other facilities required for emergency response
- Power-generating stations and other public utility facilities required in an emergency
- Ancillary structures required foroperation of Category IV structures during an emergency
- Aviation control towers, air traffic control centers and emergency aircraft hangars
- Water storage facilities and pump structures required to maintain water pressure for fire suppression
- Buildings and other structures having critical national defense functions
- Buildings and structures containing extremelyhazardous materials where quantity of material exceeds a threshhold quantity established by authority having jurisdiction
IV


The Topographic Factor, Kzt, accounts for effect of wind speed-up over isolated hills and escarpments (Sect. 6.5.7 and Fig. 6-4).

Kzt = (1+K1*K2*K3)^2 (Eq. 6-3), where:

H = height of hill or escarpment relative to the upwind terrain, in feet.

Lh = Distance upwind of crest to where the difference in ground elevation is half the height of hill or escarpment, in feet.

K1 = factor to account for shape of topographic feature and maximum speed-up effect.

K2 = factor to account for reduction in speed-up with distance upwind or downwind of crest.

K3 = factor to account for reduction in speed-up with height above local terrain.

x = distance (upwind or downwind) from the crest to the building site, in feet.

z = height above local ground level, in feet.

The effect of wind speed-up shall not be required to be considered (Kzt = 1.0) when H/Lh < 0.2, or H < 15' for Exposures 'C' and 'D', or H < 60' for Exposure 'B'.
TABLE 10-1
IMPORTANCE FACTOR, I, (ICE LOADS)
Category*I
I 0.8
II 1.0
III 1.25
IV 1.25
*See Section 1.5 and Table 1-1.

Notes:
Atmospheric ice loads due to freezing rain, snow, and in-cloud icing shall be considered in the design of ice-sensitive structures. In areas where records or experience indicate that snow or in-cloud icing produces larger loads than freezing rain, site-specific studies shall be used. Structural loads due to hoarfrost are not a design consideration.

Definitions:
FREEZING RAIN: Rain or drizzle that falls into a layer of subfreezing air at the earth’s surface and freezes on contact with the ground or an object to form glaze ice

Disclaimer: This calculator are not intended to be used for the design of actual structures, but only for schematic (preliminary) understanding of structural design principals. For the design of an actual structure, a competent professional should be consulted.

 

‘Calculations courtesy of Alex Tomanovich, PE