Thursday, January 10, 2019

Load Combinations for Structural Design


Load Combinations for RCC Structures


Combinations as per IS 456:
For Limit State of Collapse:
Load Combination
DL
LL
WL/EL
DL+LL
1.5
1.5
-
DL+WL/EL
0.9/1.5
-
1.5
DL+LL+WL/EL
1.2
1.2
1.2


For Limit State of Serviceability:
Load Combination
DL
LL
WL/EL
DL+LL
1.0
1.0
-
DL+WL/EL
1.0
-
1.0
DL+LL+WL/EL
1
0.8
0.8


For Foundation Design:
Load Combination
DL
LL
WL
EL
DL+LL
1.0
1.0
-
-
DL+LL+WL
0.8
0.8
0.8
-
DL+LL+EL
0.8
0.8
-
0.8


Note:
  1. In case of Earth quake load SBC can be increased by 25%
  2. In case of Wind load SBC can be increased by 25% by following codal provisions


The load combination (Dead load + live load + wind load or seismic load) may be neglected in design & first load combination i.e.  Dead load + Live Load shall be compared with safe bearing capacity due to shear criteria & allowable bearing capacity due settlement criteria where wind or seismic load is less than 25 percent of that due to dead and live loads. Where wind or seismic load is more than 25 percent of that due to dead and live loads, foundations may be so proportioned that the pressure due to combination of load (dead + live + wind load) does not exceed the safe bearing capacity by more than 25 percent. When seismic forces are considered, the safe bearing capacity shall be increased as specified in IS: 1893-1984.
Net safe SBC for (DL+LL +EQ) comb = SBC*(A)
A = 150% for footing with tie beams on Rock and hard soil 
A = 125% for footing with tie beams on Medium soil /or soft soil 
A = 150% for footing without tie beams on Rock and hard soil 
A = 125% for footing without tie beams on Medium soil 
A = 0.00% for footing without tie beams on soft soil 
  1. For both Earthquake and Wind Loads
Load Cases
  1. Earth quake load along +ve x direction
  2. Earth quake load along -ve x direction
  3. Earth quake load along +ve z direction
  4. Earth quake load along -ve z direction
  5. Wind load along +ve x direction
  6. Wind load along -ve x direction
  7. Wind load along +ve x direction
  8. Wind load along -ve x direction
  9. Floor Load (Dead Load) - FLDL
  10. Dead Load – DL
  11. Floor Load (Live Load) - FLLL
  12. Live Load – LL


***LIMIT STATE OF FLEXURE
LOAD COMB 13 DL*1.5+LL*1.5
9 1.5 10 1.5 11 1.5 12 1.5
*DL+EL
LOAD COMB 14 DL*1.5+EL+X*1.5
9 1.5 10 1.5 1 1.5
LOAD COMB 15 DL*1.5+EL-X*1.5
9 1.5 10 1.5 2 1.5
LOAD COMB 16 DL*1.5+EL+Z*1.5
9 1.5 10 1.5 3 1.5
LOAD COMB 17 DL*1.5+EL-Z*1.5
9 1.5 10 1.5 4 1.5
**********
LOAD COMB 18 DL*0.9+EL+X*1.5
9 0.9 10 0.9 1 1.5
LOAD COMB 19 DL*0.9+EL-X*1.5
9 0.9 10 0.9 2 1.5
LOAD COMB 20 DL*0.9+EL+Z*1.5
9 0.9 10 0.9 3 1.5
LOAD COMB 21 DL*0.9+EL-Z*1.5
9 0.9 10 0.9 4 1.5
*DL+WL
LOAD COMB 22 DL*1.5+WL+X*1.5
9 1.5 10 1.5 5 1.5
LOAD COMB 23 DL*1.5+WL-X*1.5
9 1.5 10 1.5 6 1.5
LOAD COMB 24 DL*1.5+WL+Z*1.5
9 1.5 10 1.5 7 1.5
LOAD COMB 25 DL*1.5+WL-Z*1.5
9 1.5 10 1.5 8 1.5
**********
LOAD COMB 26 DL*0.9+WL+X*1.5
9 0.9 10 0.9 5 1.5
LOAD COMB 27 DL*0.9+WL-X*1.5
9 0.9 10 0.9 6 1.5
LOAD COMB 28 DL*0.9+WL+Z*1.5
9 0.9 10 0.9 7 1.5
LOAD COMB 29 DL*0.9+WL-Z*1.5
9 0.9 10 0.9 8 1.5
*DL+LL+EL
LOAD COMB 30 DL*1.2+LL*1.2+EL+X*1.2
9 1.2 10 1.2 11 1.2 12 1.2 1 1.2
LOAD COMB 31 DL*1.2+LL*1.2+EL-X*1.2
9 1.2 10 1.2 11 1.2 12 1.2 2 1.2
LOAD COMB 32 DL*1.2+LL*1.2+EL+Z*1.2
9 1.2 10 1.2 11 1.2 12 1.2 3 1.2
LOAD COMB 33 DL*1.2+LL*1.2+EL-Z*1.2
9 1.2 10 1.2 11 1.2 12 1.2 4 1.2
*DL+LL+WL
LOAD COMB 34 DL*1.2+LL*1.2+WL+X*1.2
9 1.2 10 1.2 11 1.2 12 1.2 5 1.2
LOAD COMB 35 DL*1.2+LL*1.2+WL-X*1.2
9 1.2 10 1.2 11 1.2 12 1.2 6 1.2
LOAD COMB 36 DL*1.2+LL*1.2+WL+Z*1.2
9 1.2 10 1.2 11 1.2 12 1.2 7 1.2
LOAD COMB 37 DL*1.2+LL*1.2+WL-Z*1.2
9 1.2 10 1.2 11 1.2 12 1.2 8 1.2
***LIMIT STATE OF SERVICEABILITY
*DL+LL
LOAD COMB 38 DL*1+LL*1
9 1.0 10 1.0 11 1.0 12 1.0
***DL+EL
LOAD COMB 39 DL*1+EL+X*1
9 1.0 10 1.0 1 1.0
LOAD COMB 40 DL*1+EL-X*1
9 1.0 10 1.0 2 1.0
LOAD COMB 41 DL*1+EL+Z*1
9 1.0 10 1.0 3 1.0
LOAD COMB 42 DL*1+EL-Z*1
9 1.0 10 1.0 4 1.0
**DL+WL
LOAD COMB 43 DL*1+WL+X*1
9 1.0 10 1.0 5 1.0
LOAD COMB 44 DL*1+WL-X*1
9 1.0 10 1.0 6 1.0
LOAD COMB 45 DL*1+WL+Z*1
9 1.0 10 1.0 7 1.0
LOAD COMB 46 DL*1+WL-Z*1
9 1.0 10 1.0 8 1.0
**DL+LL+EL
LOAD COMB 47 DL*1+LL*0.8+EL+X*0.8
9 1.0 10 0.8 11 0.8 12 0.8 1 0.8
LOAD COMB 48 DL*1+LL*0.8+EL-X*0.8
9 1.0 10 0.8 11 0.8 12 0.8 2 0.8
LOAD COMB 49 DL*1+LL*0.8+EL+Z*0.8
9 1.0 10 0.8 11 0.8 12 0.8 3 0.8
LOAD COMB 50 DL*1+LL*0.8+EL-Z*0.8
9 1.0 10 0.8 11 0.8 12 0.8 4 0.8
**DL+LL+WL
LOAD COMB 51 DL*1+LL*0.8+WL+X*0.8
9 1.0 10 0.8 11 0.8 12 0.8 5 0.8
LOAD COMB 52 DL*1+LL*0.8+WL-X*0.8
9 1.0 10 0.8 11 0.8 12 0.8 6 0.8
LOAD COMB 53 DL*1+LL*0.8+WL+Z*0.8
9 1.0 10 0.8 11 0.8 12 0.8 7 0.8
LOAD COMB 54 DL*1+LL*0.8+WL-Z*0.8
9 1.0 10 0.8 11 0.8 12 0.8 8 0.8
*****FOR REACTIONS
*DL+LL
LOAD COMB 55 DL*1+LL*1
9 1.0 10 1.0 11 1.0 12 1.0
*DL+LL+EL
LOAD COMB 56 DL*0.8+LL* 0.8+EL+X*0.8
9 0.8 10 0.8 11 0.8 12 0.8 1 0.8
LOAD COMB 57 DL*0.8+LL* 0.8+EL-X*0.8
9 0.8 10 0.8 11 0.8 12 0.8 2 0.8
LOAD COMB 58 DL*0.8+LL* 0.8+EL+Z*0.8
9 0.8 10 0.8 11 0.8 12 0.8 3 0.8
LOAD COMB 59 DL*0.8+LL* 0.8+EL-Z*0.8
9 0.8 10 0.8 11 0.8 12 0.8 4 0.8
**DL+LL+WL
LOAD COMB 60 DL*0.8+LL*0.8+WL+X*0.8
9 0.8 10 0.8 11 0.8 12 0.8 5 0.8
LOAD COMB 61 DL*0.8+LL*0.8+WL-X*0.8
9 0.8 10 0.8 11 0.8 12 0.8 6 0.8
LOAD COMB 62 DL*0.8+LL*0.8+WL+Z*0.8
9 0.8 10 0.8 11 0.8 12 0.8 7 0.8
LOAD COMB 63 DL*0.8+LL*0.8+WL-Z*0.8
9 0.8 10 0.8 11 0.8 12 0.8 8 0.8








  1. For Earthquake Load


Load Cases
  1. Earth quake load along +ve x direction
  2. Earth quake load along -ve x direction
  3. Earth quake load along +ve z direction
  4. Earth quake load along -ve z direction
  5. Floor Load (Dead Load) - FLDL
  6. Dead Load – DL
  7. Floor Load (Live Load) - FLLL
  8. Live Load – LL


***LIMIT STATE OF FLEXURE
LOAD COMB 9 DL*1.5+LL*1.5
5 1.5 6 1.5 7 1.5 8 1.5
*DL+EL
LOAD COMB 10 DL*1.5+EL+X*1.5
5 1.5 6 1.5 1 1.5
LOAD COMB 11 DL*1.5+EL-X*1.5
5 1.5 6 1.5 2 1.5
LOAD COMB 12 DL*1.5+EL+Z*1.5
5 1.5 6 1.5 3 1.5
LOAD COMB 13 DL*1.5+EL-Z*1.5
5 1.5 6 1.5 4 1.5
**********
LOAD COMB 14 DL*0.9+EL+X*1.5
5 0.9 6 0.9 1 1.5
LOAD COMB 15 DL*0.9+EL-X*1.5
5 0.9 6 0.9 2 1.5
LOAD COMB 16 DL*0.9+EL+Z*1.5
5 0.9 6 0.9 3 1.5
LOAD COMB 17 DL*0.9+EL-Z*1.5
5 0.9 6 0.9 4 1.5
*DL+LL+EL
LOAD COMB 18 DL*1.2+LL*1.2+EL+X*1.2
5 1.2 6 1.2 7 1.2 8 1.2 1 1.2
LOAD COMB 19 DL*1.2+LL*1.2+EL-X*1.2
5 1.2 6 1.2 7 1.2 8 1.2 2 1.2
LOAD COMB 20 DL*1.2+LL*1.2+EL+Z*1.2
5 1.2 6 1.2 7 1.2 8 1.2 3 1.2
LOAD COMB 21 DL*1.2+LL*1.2+EL-Z*1.2
5 1.2 6 1.2 7 1.2 8 1.2 4 1.2
***LIMIT STATE OF SERVICEABILITY
*DL+LL
LOAD COMB 22 DL*1+LL*1
5 1.0 6 1.0 7 1.0 8 1.0
***DL+EL
LOAD COMB 23 DL*1+EL+X*1
5 1.0 6 1.0 1 1.0
LOAD COMB 24 DL*1+EL-X*1
5 1.0 6 1.0 2 1.0
LOAD COMB 25 DL*1+EL+Z*1
5 1.0 6 1.0 3 1.0
LOAD COMB 26 DL*1+EL-Z*1
5 1.0 6 1.0 4 1.0
**DL+LL+EL
LOAD COMB 27 DL*1+LL*0.8+EL+X*0.8
5 1.0 6 0.8 7 0.8 8 0.8 1 0.8
LOAD COMB 28 DL*1+LL*0.8+EL-X*0.8
5 1.0 6 0.8 7 0.8 8 0.8 2 0.8
LOAD COMB 29 DL*1+LL*0.8+EL+Z*0.8
5 1.0 6 0.8 7 0.8 8 0.8 3 0.8
LOAD COMB 30 DL*1+LL*0.8+EL-Z*0.8
5 1.0 6 0.8 7 0.8 8 0.8 4 0.8
*****FOR REACTIONS
*DL+LL
LOAD COMB 31 DL*1+LL*1
5 1.0 6 1.0 7 1.0 8 1.0
*DL+LL+EL
LOAD COMB 32 DL*0.8+LL* 0.8+EL+X*0.8
5 0.8 6 0.8 7 0.8 8 0.8 1 0.8
LOAD COMB 33 DL*0.8+LL* 0.8+EL-X*0.8
5 0.8 6 0.8 7 0.8 8 0.8 2 0.8
LOAD COMB 34 DL*0.8+LL* 0.8+EL+Z*0.8
5 0.8 6 0.8 7 0.8 8 0.8 3 0.8
LOAD COMB 35 DL*0.8+LL* 0.8+EL-Z*0.8
5 0.8 6 0.8 7 0.8 8 0.8 4 0.8


  1. For Wind Load


  1. Wind load along +ve x direction
  2. Wind load along -ve x direction
  3. Wind load along +ve x direction
  4. Wind load along -ve x direction
  5. Floor Load (Dead Load) - FLDL
  6. Dead Load – DL
  7. Floor Load (Live Load) - FLLL
  8. Live Load – LL




***LIMIT STATE OF FLEXURE
LOAD COMB 9 DL*1.5+LL*1.5
5 1.5 6 1.5 7 1.5 8 1.5
*DL+WL
LOAD COMB 10 DL*1.5+WL+X*1.5
5 1.5 6 1.5 1 1.5
LOAD COMB 11 DL*1.5+WL-X*1.5
5 1.5 6 1.5 2 1.5
LOAD COMB 12 DL*1.5+WL+Z*1.5
5 1.5 6 1.5 3 1.5
LOAD COMB 13 DL*1.5+WL-Z*1.5
5 1.5 6 1.5 4 1.5
**********
LOAD COMB 14 DL*0.9+WL+X*1.5
5 0.9 6 0.9 1 1.5
LOAD COMB 15 DL*0.9+WL-X*1.5
5 0.9 6 0.9 2 1.5
LOAD COMB 16 DL*0.9+WL+Z*1.5
5 0.9 6 0.9 3 1.5
LOAD COMB 17 DL*0.9+WL-Z*1.5
5 0.9 6 0.9 4 1.5
*DL+LL+WL
LOAD COMB 18 DL*1.2+LL*1.2+WL+X*1.2
5 1.2 6 1.2 7 1.2 8 1.2 1 1.2
LOAD COMB 19 DL*1.2+LL*1.2+WL-X*1.2
5 1.2 6 1.2 7 1.2 8 1.2 2 1.2
LOAD COMB 20 DL*1.2+LL*1.2+WL+Z*1.2
5 1.2 6 1.2 7 1.2 8 1.2 3 1.2
LOAD COMB 21 DL*1.2+LL*1.2+WL-Z*1.2
5 1.2 6 1.2 7 1.2 8 1.2 4 1.2
***LIMIT STATE OF SERVICEABILITY
*DL+LL
LOAD COMB 22 DL*1+LL*1
5 1.0 6 1.0 7 1.0 8 1.0
**DL+WL
LOAD COMB 23 DL*1+WL+X*1
5 1.0 6 1.0 1 1.0
LOAD COMB 24 DL*1+WL-X*1
5 1.0 6 1.0 2 1.0
LOAD COMB 25 DL*1+WL+Z*1
5 1.0 6 1.0 3 1.0
LOAD COMB 26 DL*1+WL-Z*1
5 1.0 6 1.0 4 1.0
**DL+LL+WL
LOAD COMB 27 DL*1+LL*0.8+WL+X*0.8
5 1.0 6 0.8 7 0.8 8 0.8 1 0.8
LOAD COMB 28 DL*1+LL*0.8+WL-X*0.8
5 1.0 6 0.8 7 0.8 8 0.8 2 0.8
LOAD COMB 29 DL*1+LL*0.8+WL+Z*0.8
5 1.0 6 0.8 7 0.8 8 0.8 3 0.8
LOAD COMB 30 DL*1+LL*0.8+WL-Z*0.8
5 1.0 6 0.8 7 0.8 8 0.8 4 0.8
*****FOR REACTIONS
*DL+LL
LOAD COMB 31 DL*1+LL*1
5 1.0 6 1.0 7 1.0 8 1.0
**DL+LL+WL
LOAD COMB 32 DL*0.8+LL*0.8+WL+X*0.8
5 0.8 6 0.8 7 0.8 8 0.8 1 0.8
LOAD COMB 33 DL*0.8+LL*0.8+WL-X*0.8
5 0.8 6 0.8 7 0.8 8 0.8 2 0.8
LOAD COMB 34 DL*0.8+LL*0.8+WL+Z*0.8
5 0.8 6 0.8 7 0.8 8 0.8 3 0.8
LOAD COMB 35 DL*0.8+LL*0.8+WL-Z*0.8
5 0.8 6 0.8 7 0.8 8 0.8 4 0.8


  1. For Live Load


  1. Floor Load (Dead Load) - FLDL
  2. Dead Load – DL
  3. Floor Load (Live Load) - FLLL
  4. Live Load – LL




***LIMIT STATE OF FLEXURE
LOAD COMB 5 DL*1.5+LL*1.5
1 1.5 2 1.5 3 1.5 4 1.5
***LIMIT STATE OF SERVICEABILITY
*DL+LL
LOAD COMB 6 DL*1+LL*1
1 1.0 2 1.0 3 1.0 4 1.0
*****FOR REACTIONS
*DL+LL
LOAD COMB 7 DL*1+LL*1
1 1.0 2 1.0 3 1.0 4 1.0




at

1 comment:

Subscribe to: Post Comments (Atom)

Design of Cantilever retaining wall - Software

  Link -  Cantilever retaining wall design