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4. Calculate Lightening Protection for Building / Structure

CALCULATE LIGHTNING PROTECTION FOR BUILDING / STRUCTURE

Example: Calculate Whether Lightning Protection is required or not for following Building. Calculate No of Down Conductor for Lightning Protection

Area of Building / Structure:

  • Length of Building (L) = 60 Meter. * Width of Building ( W ) = 28 Meter. * Height of Building (H) = 23 Meter.

Lightning Stock Flushing Density

  • Number of Thunderstorm (N)= 80.00 Days/Year * Lightning Flash Density (Ng)=69 km2/Year * Application of Structure (A)= Houses & Buildings * Type of Constructions (B)= Steel framed encased without Metal Roof * Contests or Consequential Effects (C)= Domestic / Office Buildings * Degree of Isolation (D)= Structure in a large area having greater height * Type of Country (E)= Flat country at any level * Maximum Acceptable Overall Risk Factor =0.00000001

Reference Table As per IS:2309 Thunder Storm Days / Year Lightning Flash Density (Flashes to Ground /km2/year) 5 0.2 10 0.5 20 1.1 30 1.9 40 2.8 50 3.7 60 4.7 80 6.9 100 9.2

Application of Structure Factor Houses & Buildings 0.3 Houses & Buildings with outside aerial 0.7 Factories / workshop/ Laboratories 1 Office blocks / Hotel 1.2 Block of Flats / Residences Building 1.2 Churches/ Hall / Theaters / Museums, Exhibitions 1.3 Departmental stores / Post Offices 1.3 Stations / Airports / Stadium 1.3 Schools / Hospitals / Children’s Home 1.7 Others 1.2

Type of Constructions Factor Steel framed encased without Metal Roof 0.2 Reinforced concrete without Metal Roof 0.4 Steel framed encased with Metal Roof 0.8 Reinforced concrete with Metal Roof 1 Brick / Plain concrete or masonry without Metal Roof 1.4 Timber framed or clad without Metal Roof 1.7 Brick / Plain concrete or masonry with Metal Roof 2 Timber framed or clad with Metal Roof

Contests or Consequential Effects Factor Domestic / Office Buildings 0.3 Factories / Workshop 0.3 Industrial & Agricultural Buildings 0.8 Power stations / Gas works 1 Telephone exchange / Radio Station 1 Industrial key plants, Ancient monuments 1.3 Historic Buildings / Museums / Art Galleries 1.3 Schools / hospitals / Children Homes 1.7

Degree of Isolation Factor Structure in a large area having greater height 0.4 Structure located in a area of the same height 1 Structure completely Isolated 2

CALCULATION:

Collection Area (Ac)=(L x W) + 2 (L x H) + 2(W x H) +(3.14 x H2)

  • Collection Area (Ac) = (60×28)+2x(60×23)+2x(28×23)+(3.14x23x23) * Collection Area (Ac) =7389 Meter2

Probable No of Strikes to Building / Structure (P)= Ac x Ng x 10-6 No’s / Year

  • Probable No of Strikes to Building / Structure (P)= 7389x69x10–6 No’s / Year * Probable No of Strikes to Building / Structure (P)= 05098 No’s / Year

Overall Multiplying Factor (M) =A x B x C x D x E

  • Application of Structure (A)= Houses & Buildings as per Table Multiplying Factor = 0.3 * Type of Constructions (B)= Steel framed encased without Metal Roof as per Table Multiplying Factor =0.2 * Contests or Consequential Effects (C)= Domestic / Office Buildings as per Table Multiplying Factor =0.3 * Degree of Isolation (D)= Structure in a large area having greater height as per Table Multiplying Factor =0.4 * Type of Country (E)= Flat country at any level so as per Table Multiplying Factor =0.3 * Overall Multiplying Factor (M) =0.3×0.2×0.3×0.4×0.3 * Overall Multiplying Factor (M) =0.00216

Overall Risk Factor Calculated (xc)= M x P

  • Overall Risk Factor Calculated (xc)= 0.00216 x0.05098 * Overall Risk Factor Calculated (xc)= 000110127

 Base Area of Structure (Ab) = (LxW)

  • Base Area of Structure (Ab)=60×28 * Base Area of Structure (Ab)=1680 Meter2

Perimeter of Structure (P) =2x (L+W)

  • Perimeter of Structure (P)=2x(60+28) * Perimeter of Structure (P)=176 Meter

Lightning Protection Required or Not

  • If Calculated Overall Risk Factor Calculated > Maximum Acceptable Overall Risk Factor than only Lighting Protection Required * Here Calculated Overall Risk Factor is 0.000110127 > Max Acceptable Overall Risk Factor is 00000001 * Lightning Protection is Required

 No of Down Conductor

  • Down Conductors As per Base Area of Structure (s) =1+(Ab-100)/300 * Down Conductors As per Base Area of Structure (s) =1+(1680-100)/300 * Down Conductors As per Base Area of Structure (s) =6 No’s * Down Conductors As per Perimeter of Structure (t)= P/30 * Down Conductors As per Perimeter of Structure (t)= 176/30 * Down Conductors As per Perimeter of Structure (t)= 6 No’s * Minimum No of Down Conductor is 6 No’s

 RESULTS:

  • Lightning Protection is Required * Down Conductors As per Base Area of Structure (s) =6 No’s * Down Conductors As per Perimeter of Structure (t)= 6 No’s * Minimum No of Down Conductor is 6 No’s