stairs rajesh sir
Post on 06-May-2015
154 Views
Preview:
DESCRIPTION
TRANSCRIPT
Lecture Notes 15 July 2010
Dr. B. Rajeevan 1
Dr. B. RajeevanSenior Lecturer
Department of Civil EngineeringGovt. College of Engineering Kannur
E-mail: rajeevan@gcek.ac.inMob: 9495 333 088
Contact Time: 4 pm – 5 pm
DESIGN OF STAIRSSTRUCTURAL DESIGN
15 July 2010 Dr. B. Rajeevan 2
Geometrical Classification
15 July 2010 Dr. B. Rajeevan 3
Geometrical Classification
15 July 2010 Dr. B. Rajeevan 4
15 July 2010 Dr. B. Rajeevan 5
Structural Classification-Stair spanning longitudinally
15 July 2010 Dr. B. Rajeevan 6
Lecture Notes 15 July 2010
Dr. B. Rajeevan 2
15 July 2010 Dr. B. Rajeevan 7
Structural Classification-Stair
spanning transversely
Parts of a stair
15 July 2010 Dr. B. Rajeevan 8
15 July 2010 Dr. B. Rajeevan 9
Public BuildingsRise = 150 mmTread = 270 mm to 300 mm
Residential BuildingsRise = 160 mmTread = 250 mm
Number of rise in one flight < 12
15 July 2010 Dr. B. Rajeevan 10
Empirical relation
550 < (2R + G) < 750 (in mm)
(2R + G) = 600 (approx)
Principles of Design
• Cl. 33 of IS 456-2000
– Stair spanning horizontally (transversely)
– Stair spanning longitudinally
15 July 2010 Dr. B. Rajeevan 11
Stair spanning horizontally
15 July 2010 Dr. B. Rajeevan 12
Lecture Notes 15 July 2010
Dr. B. Rajeevan 3
Stair spanning horizontally
15 July 2010 Dr. B. Rajeevan 13
Stair spanning horizontally
15 July 2010 Dr. B. Rajeevan 14
Stair spanning longitudinally
Slab between beams
15 July 2010 Dr. B. Rajeevan 15
Stair spanning longitudinally
Slab between landings
15 July 2010 Dr. B. Rajeevan 16
Stair spanning longitudinally
Slab between walls
15 July 2010 Dr. B. Rajeevan 17
Dead Loads
15 July 2010 Dr. B. Rajeevan 18
Lecture Notes 15 July 2010
Dr. B. Rajeevan 4
Live Loads
• Live Load (IS 875)
– Residential building without overcrowding – 2 kN/m2
– Public building with overcrowding – 5 kN/m2
15 July 2010 Dr. B. Rajeevan 19
Depth of Section
• One way reinforced slab
– Longitudinally spanning – min thickness = W
– Transverse spanning – average depth of step; D/2
15 July 2010 Dr. B. Rajeevan 20
Structural Detailing
• Maximum BM – simply supported = wl2/8– One half of tension steel taken to supports
• Maximum BM – slab built-in to beams at supports = (0.9) wl2/8; – 2/3 of tension steel to support as negative steel
• Maximum BM – slab continuous over beams at supports = wl2/10; – Full tension steel to support as negative steel
• Distributors– 0.0012bD or 0.0015bD in transverse direction; – Full tension steel to support as negative steel
15 July 2010 Dr. B. Rajeevan 21 15 July 2010 Dr. B. Rajeevan 22
15 July 2010 Dr. B. Rajeevan 23
Calculation of Dead Loads and Effective Depth
• Transverse Stair
– Effective span = width of stair
– Individual steps of width = G and span = width of stair
15 July 2010 Dr. B. Rajeevan 24
Lecture Notes 15 July 2010
Dr. B. Rajeevan 5
Calculation of Dead Loads and Effective Depth
• Longitudinally spanning Stair
15 July 2010 Dr. B. Rajeevan 25
Design Example 1
A staircase has the following dimensions: waist W = 75 mm; nosing N = 25 mm; rise R =175 mm; going G = 225 mm. The live load expected is 2 kN/m2. Calculate the factored loads and effective depths for design if the staircase is spanning (a) transversely , and (b) longitudinally
15 July 2010 Dr. B. Rajeevan 26
15 July 2010 Dr. B. Rajeevan 27
Ref Step Calculations Output
1
wu=2.3kN/m
2
2 2 2 2250 175 305
tan
125 1.08 /
1 2
0.225 2 0.45 /
, 1.5( ) 2.295 /u
B G R mm
Slab spanning seversely
RTDL WB kN m
LL kN m
Design Load w DL LL kN m
covercos 2 2
161.5 ( 12 )
W Rd
mm Use mmdia161.5d mm
15 July 2010 Dr. B. Rajeevan 28
Ref Step Calculations Output
1
wu=10.22 kN/m
2
2 2 2 2250 175 305
tan
125 4.81 /
2
2 /
, 1.5( ) 10.22 /u
B G R mm
Slab spanning seversely
RTDL WB kN m
G
LL kN m
Design Load w DL LL kN m
cover2
54 ( 12 )
d W
mm Use mmdia54d mm
Design Example 2
A longitudinal type of stair spans a distance of 3.75 m c/c of beams. R = 175 mm, T =250 mm. The treads have 15 mm granite finish and consists of 15 steps. Use M25 grade concrete and Fe 415 steel. Take Live load = 5 kN/m2. Width of stair = 1.5 m.
15 July 2010 Dr. B. Rajeevan 29 15 July 2010 Dr. B. Rajeevan 30
Ref Step Calculations Output
IS 456Cl. 26.4
1 Thickness of waist slab, WAssume l/d =30, d = 3750/30 = 125W = 125 + cover + /2 = 125 + 15 + 6 = 146 mm = 150 mm (say)
d = 150 -15 -6 =129 mm W = 150 mmd = 129 mm
2 Loads – Dead Load
DL =
Design Load = 1.5(DL + LL) = 18.48 kN/m2
SP 16 Table D
3 Bending Moment, Mu, Check for Mu,lim
SP16Table 3
4 Area of main steel
2 2 2 2250 175 305B G R mm
2125 23.5 7.32 /
2
RT FTWB kN m
G G
218.48 /uw kN m
2
26 /10
wkN m
,limu uM M
2
2
1.56, 0.472
606100
u
st
Mp
bd
pbdA mm
Lecture Notes 15 July 2010
Dr. B. Rajeevan 6
15 July 2010 Dr. B. Rajeevan 31
Ref Step Calculations Output
SP 16 Table 96
5 Compute Spacing Provide 12 mm dia bars at 180 mm c/cMax spacing 3d or 300 mm
12 mm dia bars at 180 mm c/c
IS 456Cl. 25.5.2.1
SP 16 Table 96
6 Distributors
Provide 8 mm dia @ 270 mm c/c
Max spacing 5d or 450 mm
8 mm dia @ 270 mm c/c
IS456Table 19
7 Shear Check
No shear reinforcement necessary
IS 456Fig 4
8 Check for Deflection(l/d)allowed = 1.2 x 26 =31.2(l/d)assumed = 30 < 31.2
(l/d) ratio OK
2
,min 0.12 /100 180stA bD mm
34.65 ; / 0.272
0.36 ; Noshear reinforcement
v
c v c
wV kN V bd MPa
MPa
Design Example 3
15 July 2010 Dr. B. Rajeevan 32
Design a waist slab type stair shown in Figure. Landing slab A is supported on beams along JK and PQ, while the waist slab and landing slab B are spanning longitudinally as shown in Figure. The finish load and Live load are 1 kN/m2 and 5 kN/m2 , respectively. Use R = 160 mm and T = 270 mm, concrete grade = M20 and steel grade = Fe 415
15 July 2010 Dr. B. Rajeevan 33 15 July 2010 Dr. B. Rajeevan 34
15 July 2010 Dr. B. Rajeevan 35 15 July 2010 Dr. B. Rajeevan 36
Lecture Notes 15 July 2010
Dr. B. Rajeevan 7
15 July 2010 Dr. B. Rajeevan 37 15 July 2010 Dr. B. Rajeevan 38
15 July 2010 Dr. B. Rajeevan 39 15 July 2010 Dr. B. Rajeevan 40
15 July 2010 Dr. B. Rajeevan 41 15 July 2010 Dr. B. Rajeevan 42
Lecture Notes 15 July 2010
Dr. B. Rajeevan 8
15 July 2010 Dr. B. Rajeevan 43 15 July 2010 Dr. B. Rajeevan 44
15 July 2010 Dr. B. Rajeevan 45
Homework
15 July 2010 Dr. B. Rajeevan 46
15 July 2010 Dr. B. Rajeevan 47 15 July 2010 Dr. B. Rajeevan 48
Lecture Notes 15 July 2010
Dr. B. Rajeevan 9
15 July 2010 Dr. B. Rajeevan 49 15 July 2010 Dr. B. Rajeevan 50
LOADS AT SECTION 1-1
15 July 2010 Dr. B. Rajeevan 51 15 July 2010 Dr. B. Rajeevan 52
15 July 2010 Dr. B. Rajeevan 53 15 July 2010 Dr. B. Rajeevan 54
Lecture Notes 15 July 2010
Dr. B. Rajeevan 10
15 July 2010 Dr. B. Rajeevan 55 15 July 2010 Dr. B. Rajeevan 56
15 July 2010 Dr. B. Rajeevan 57
top related