Design of Stair Case

Design of  Stair Case

 

Vertical distance between two floors= 3.2 m

Assuming two flights

Height  Of each  flights= 3.2/2 = 1.6m

Clear Width Of each Step=1500mm

Rise  Of  each Step =150mm

Thread Of each Step=230mm

No  of  rise/flight=12

Going of each flight=12×230 = 2760mm

Width of Support=230mm

Grade of Concrete=M20

Grade of Steel =Fe415

 

SPAN OF STAIR CASE:

Clear Span=6m

Effective Span=6000+230 =6230mm

 

DESIGN OF FLIGHT:

Bearing of the flight  = 150mm

Effective horizontal Span=6.075m

 

THICKNESS OF SLAB:

Considering 50mm Per m of Span

1.6×50=300mm

2.Dead load=230×25×1×1 = 5750N/m2

3.Finish=50×24=1200 N/m2 = 6950N/m2

Corresponding load/eq.moment  of span

(R2+T2)/T)×L

Load/M                                 =8297.41N/M

Waist slab&ceiling finish =8.300N/M

Dead load of slab                                =1/2×230×150×19=0.32KN/M

Live Load                             =4KN/M

Total Load                                            =12.62KN/M

Factored Load                     =12.62×1.5=18.93KN/M

Factored load for 1.5M      =18.93×1.6=30.288KN/M

 

MOMENT AND REACTION:

RA=50.19KN & RB=50.30KN

Moment @3.0M

50.3×3.0-(8.5×0.5×0.32)+(12.52×1×1.10)+(30.26×0.720)

M  =95.68KNM

Mu=Mlimit

95.68=0.138×20×1000×d2

d  =186.18mm<200mm

 

 

 

 

TO GET AST:

Ast             = 50×(1-1√1-(4.6/20)×(95.68×106/1000×2002))/(415/20))

=1.12%

Ast             =1.12/100×1000×200 = 2240mm

No .of 16mm dia bars = 2240/(3.14(16)2/4) = 11 bars

DISTRIBUTION BARS

(0.12/100)×1000×200 =240mm2

Spacing of 6mm dia bars =(3.14(6)2/4)240×1000=120mmc/c

Provide 6 mm dia @ 120mmc/c as distribution steel

 

 

 

DESIGN OF LANDING:

Reaction from flight = Rb×1.5-(8,5×0.5)×0.5+(12.52×1) ×0.5

=68KNM

Mu  =  Mu limit

68×106 = 0.138×20×1000×d2

d  =  157 < 200mm

Ast  =  50×(1-1√1-(4.6/20)×(68×106/1000×2002))/(415/20))

=0.8%

Ast =0.8/100×1000×200=1600mm2

Spacing of 12 mm dia bars =(3.14(12)2/4)1600×1000= 70mm

Provide 12 mm dia @ 70mmc/c   on  landing

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