Questions
1) In this Load management significance of Load case -1 & 2 ( SW-SUM &
STG-SUM) is not understood. Could you please explain what does this
signifies?
Does STG-SUM LOAD CASE= CS LOAD MANG+SW LOAD MANAG?
I have worked on a 12.5 m c/c simple supported slab and before using it in
other projects as I would like to understand that how the software works.
Therefor I have checked the structure for both strength condition &
serviceable condition
A) Strength condition:
I have calculated the area of reinforcement manually and verified with
the software.
i) In software I found the results as:
ii)
In manually I also got the same results as: 280 cm2.Which match
with the results
Question:
1) I have modelled the total length of slab as of 12.5 m length. I want
to design it as an effective span of 12.00 m as slab is resting on a
pier cap for a length of 0.5 m.
Does the software automatically change the spring position as per pier
length or manually we have to change the spring position?
12.5 m
12.0 m
Pier width: 1.00 m
B) Serviceable criteria:
a) Deflection: calculated by taking no shrinkage ( Ts=1000)
( Short term deflection)
( Long term deflection)
Long term deflection = 12.012/4.594 = 2.61 =1 + creep coeff.
Short term deflection
Hence creep coeff comes very close to 1.6 ( As per IRC code if loading is
applied on 28 days creep coeff =1.6)
2) Question:
in deflection calculation, E creep is considered but effective moment of
inertia is not considered i.e. Ieff (Cracked moment of inertia)
How to consider the cracked moment of inertia. Also is there any way to
check the moment of inertia which programme is using for calculation?
b) Stress check at top & bottom fibres at mid-section for following
condition
i) Early stage & long term (considering only creep effect 1.6 &
cracked section) manual calculation considering cracked effect
3) The results of top & bottom fibres are not matching as it is
considering I gross & moment of inertia due to tension area of
concrete is not neglected
4) RM Sets are defined to calculate the stresses .Could you please give
any reference that how to define it?
5) Although crack.sup is defined ,how to check the crack width
The manual calculation of serviceable criteria is attached .I like to validate
the results
9. Stress check in SLS case
Maximum compressive stress in N/mm
14.4
concrete under rare combination = 2
N/mm
2.5
2
Maximum tensile stress in concrete =
Permissible crack width = 0.2 mm
Maximum tensile stress in steel under N/mm
rare combination = 347.83 2
Section properties of uncracked section
Width of section , b = 1000 mm
Depth of section , D = 900 mm
Gross cross-sectional area = 900000 mm2
Gross moment of Inertia Igxx = 6.08E+10 mm4
Modular ratio : for early age check
Modulus of elasticity of concrete N/mm
,Eceff = 31220.2 2
N/mm
Modulus of elasticity of steel Es = 200000 2
modular ratio = 6.41
Modular ratio : for long term check
Creep coeff = 1.6
Eceff = 12008
Modular ratio = 16.66
N/mm
Maximum compressive stress = 14.40 2 As per clause 12.2.1 :IRC 112:2011
N/mm
Maximum tensile stress = 347.826 2
Load factor
leading thermal load = 1
Accompanied thermal load = 0.6
Neutral
axis depth
dc
9.A Check for Serviciable stress(rare combination)
Case:1 leading live load accompanied thermal load
For early age for long term age
Working bending moment = 752.188 752.188 kn
b = 1000 1000 m
D = 900 900 m
Effective depth d = 838 838 m
Eceff 31220 12008 N/
Es 200000 200000 N/
Ast provided = 4462.49 4462.49 m
dc 192.10 286.26
Cracked second moment of Inertia = 2227674626 1825450619 m
Section modulus Zt = 11596711.665 6376929.583 m
Section modulus Zb = 3451593.815 3311526.412 m
Normal bending Top(comp) = 10.13 7.08 N/
stress
Bottom(Tensio) = 217.92 227.14 N/
Thermal Temp: Top = -2.26 -2.26 N/
bending rise
stress case Bottom = -0.68 -0.68 N/
Temp:
Thermal fall Top = 1.70 1.70 N/
bending case
stress Bottom = 0.76 0.76 N/
Temp: 14.4
Final rise Top = 12.38 < 0 9.34 < 14.4 N/
bending case 347. 347.82
stress Bottom = 217.24 < 8 226.46 < 6 N/
Final Temp: Top = 8.42 < 14.4 5.38 < 14.4 N/
bending fall 347. 347.82
stress case Bottom = 218.68 < 8 227.90 < 6 N/
9.B Quasi permanent (Check for stress)
For early age
Working bending moment = 476.072 knm/m
b = 1000 mm
D = 900 mm
Effective depth d = 838 mm
Eceff = 31220 N/mm2
Es = 200000 N/mm2
Ast provided = 4462.49 mm2/m
dc = 192.10
Cracked second moment of Inertia = 2227674626 mm3
Section modulus Zt = 11596711.665 mm3
Section modulus Zb = 3451593.815 mm3 As per clauseIRC:112:
Normal bending Top = 6.41 N/mm2 < 10.8 (0
stress Bottom = 137.93 N/mm2 < 347.83
Hence linear creep is considered for serviceable stress ca
Cover = 50 mm
9.C Check for crack width ( As per clause 12.3.4 IRC:112-2010)
Crack width = Sr max X (ξsm-ξcm)
Above formula for calculation is applicable if the spacing between reinforcement is less than 5 *( c+φ/2)
5 X ( c+φ/2) = 312.50
Provided spacing = 110.00
Applicable
K1 = 0.80
K2 = 0.50
b = 1000 mm
D = 900 mm
d = 838
Depth of neutral axis = 192.10
hc eff = 156.25
Ac eff = 156250.00
ρ ρ eff = 0.029
Maximum spacing Sr max = 318.81
tensile stress in steel σsc = 137.93
Kt = 0.50
Tensile strength of concrete fctm = 2.5
αe=Es/Ecm = 6.41
εsm-εcm = 0.000431
Crack width = 0.137 < 0.2 safe
