bbs of staircase with an easy example

preparing bbs of staircase includes calculation of Main bar cutting length, top extra bat at plinth and mid landing and no. of bars and the calculating the weight of bars after that the data table is prepared.

staircase plan

staircase plan

In the figure above which is plan of the staircase, we will cut the section of staircase and calculate the bars upto mid landing (1 flight) and after that we will multiply it by 2 to get the total value including cutting length, bar nos. and weight of one whole staircase (both flight).

staircase section X-X

Landing = 1200x125mm

waist slab thickness = 125mm

rise = 150mm

tread = 300mm

beam = 250x200mm

stair length = 1200mm

main bar = 10mm@200mm C/C

top extra bar (plinth, landing) = 10mm@200mm C/C

distribution bar = 8mm@150mm C/C

landing and steps

no. of steps = 9

no. of riser = 9+1 = 10

cover (beam, landing, waist slab) = 25mmm

angle of staircase (ϴ) = tan-1 (rise/run) = 26.56 = 27°

Slant Main bar & distribution bar

staircase Slant Main bar & distribution bar

Slant Main bar

LX = Tread*no. of steps

= 300*9 = 2700mm = 2.7m

LY = Riser*no. of riser

= 150*10 = 1500mm = 1.5m

length of waist slab (LWS) = sqrt(LX^2+LY^2)

= sqrt(2700^2+1500^2) = 3088.68 ~ 3090mm

Slant Main bar Cutting length =(beam width-beam cover)+LWS+(Landing width-tread)+(beam depth-beam cover)-2*2d(bends)-2*1d(bends)

= (200-25)+3090+(1200-300)+(250-25)-(2*2*10)-(2*1*10) = 4330mm

No. of main bars = (stair length/spacing)+1

= (1200/200)+1 = 7 nos.

Weight = ((d^2/162)*CL)/1000

= ((10^2/162)*4330)/1000 = 2.68Kg

Distribution bar

stair length – (2cover)

= 1200-(2*25) = 1150mm

No . of distribution bar = ((LWS+(landing-tread))/spacing+1)

= ((3090+(1200-300))/150)+1) = 27.6 ~ 28 nos.

Weight = ((d^2/162)*CL)/1000

= ((8^2/162)*1150)/1000 = 0.454Kg

Top extra bar & distribution bar at plinth

staicase Top extra bar & distribution bar at plinth

Top extra bar

No. of top extra bar = (stair length/spacing)+1

= (1200/200)+1 = 7 nos.

Top extra bar cutting length = (LWS/3)+(beam depth-beam cover)-1*2d(bend)

= (3090/3)+(250-25)-(1*2*10) = 1235mm

Weight = ((d^2/162)*CL)/1000

= ((10^2/162)*1235)/1000 = 0.762Kg

Distribution bar

No. of distribution bar = ((LWS)/spacing)+1

= ((3090/3)/150)+1 = 7.86 ~ 8 nos.

Distribution bar cutting length = stair length – (2cover)

= 1200-(2*25) = 1150mm

Weight = ((d^2/162)*CL)/1000

= ((8^2/162)*1150)/1000 = 0.454Kg

Top extra bar & distribution bar at mid landing

staircase Top extra bar & distribution bar at mid landing

Top extra bar

No. of top extra bar = (stair length/spacing)+1

= (1200/200)+1 = 7 nos.

Top extra bar cutting length = (LWS/3)+(landing-tread)+(beam depth-beam cover)-1*1d(bend)

= (3090/3)+(1200-300)+(250-25)-(2*1*10) = 2135mm

Weight = ((d^2/162)*CL)/1000

= ((10^2/162)*2135)/1000 =1.318Kg

Distribution bar

No. of distribution bar = (((LWS/3)+(landing-tread))/spacing)+1

= (((3090/3)+(1200-300))/150)+1 = 13.86 ~ 14 nos.

Distribution bar cutting length = stair length – (2cover)

= 1200-(2*25) = 1150mm

Weight = ((d^2/162)*CL)/1000

= ((8^2/162)*1150)/1000 = 0.454Kg

Sl. No.DescriptionBar dia (mm)Cutting length (mm)Weight (Kg)No. of barsTotal Weight (Kg)
1Slant Main bar1043302.68737.52
2Distribution bar811500.4542825.424
3Top extra bar at plinth1012350.762710.668
4Distribution bar at plinth811500.45498.172
5Top extra bar at mid landing1021351.318718.452
6Distribution bar at mid landing811500.4541412.712

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