Week 1 Challenge

Aim: To assess dead loads in the given box girder bridge structure and perform analysis in Staad pro.

Introduction : The given structure is a box girder bridge having span 12m. The site of the structure is located within 60km radius from bay of bengal; unit weight of soil is 19kN/cu.m. The site comes under seismic zone IV and area has a wind speed of 47km/hr. Pier of given structure is circular with diameter of 2.5m. The width of bridge deck given is 10.2m.

Procedure :

Step 1 - To calculate dead load on and of superstructure.

The given box girder is divided into portions as top rectangle, bottom rectangle and exterior walls.

Top rectangle varies from 8.4 to 11.4m considering maximum length of 11.4m.

Straight length of exterior walls is (2.4-0.225-0.2) 1.975m having slope H:V = 1:2.5, therefore for inclined length calc is as follows :Arctan(2.5/1)=68 degree Inclined length = 1.975/sin68= 2.13m

Box Girder
Member	Length m	Thk/Depth m	Area sq.m	Weight kN/sqm
Top rect.	11.4	0.225	2.565	20.1
Bott rect.	4.02	0.2	0.804	64.125
Exterior walls(2Nos)	2.13	0.25	1.065	26.625
Total				110.85

• Dead Load due to deck slab

Width of deck = 10.2m

Assume thk of deck slab = 0.25m

Load= 10.2 x 0.25 x 25 = 63.75 kN/m

• Superimposed Dead Load due to floor finish

Assume floor finish of 75mm over the deck

Load = 10.2 x 0.075 x 22 = 16.83 kN/m

Above highlighted loads are applied in Staad for analysis.

Pier of height 10m is modelled in staad with dia 2.5m and selfweight command is automatically considered by staad.

Step 2 : Staad Modelling

In Staad Pro main window click on geometry tab in left side, create 1st node at coordinate 0,0,0 and then for pier height create node at height 10m 0,10,0, then create a beam between these two nodes.

Copy this member by ctrl c and paste it at a distance of 12m (span length) by ctrl v by X=12m.

Create fixed support from support tab and assign it to the bottom of both the piers. Create property by selecting circle of 2.5m dia concrete material and assign it to both the pier. Create a member connecting top of both the pier by selecting add member from point to point from geometry tab, create a material with zero density property and assign it to the member with member property as rectangle 11.4x2.4m as we are applying box girder load as udl.

Now click on loading in left tab and create load case definations as DL of girder, Deck Slab wt, Floor finish and SW of pier and assign the loadings above in each load cases. Select static check from analysis in geometry tab. Run Analysis and extract forces.

Results:

Deflection diagram for Dead load cases:

• Bending moment diagram for DL of box girder load case

The value obatined is approximately WL^2/8 as for simply supported beam.

• Shear Force diagram for DL of box girder load case

The value obatined is WL/2 as for simply supported beam.

In the same way load for all other load cases is verified and found to be in order.

Force on girder beam

Force on pier

Report : Staad input and output is presented below

1. STAAD SPACE
INPUT FILE: Challenge 1.STD
2. START JOB INFORMATION
3. ENGINEER DATE 08-JUL-22
4. END JOB INFORMATION
5. INPUT WIDTH 79
6. UNIT METER KN
7. JOINT COORDINATES
8. 1 0 0 0; 2 0 10 0; 3 12 0 0; 4 12 10 0
9. MEMBER INCIDENCES
10. 1 1 2; 2 3 4; 3 2 4
11. DEFINE MATERIAL START
12. ISOTROPIC CONCRETE
13. E 2.17185E+007
14. POISSON 0.17
15. DENSITY 23.5616
16. ALPHA 1E-005
17. DAMP 0.05
18. ISOTROPIC NO
19. E 3.5E+007
20. POISSON 0.17
21. DAMP 0.05
22. ISOTROPIC NULL
23. E 3.5E+007
24. POISSON 0.17
25. DAMP 0.05
26. END DEFINE MATERIAL
27. MEMBER PROPERTY AMERICAN
28. 1 2 PRIS YD 2.5
29. MEMBER PROPERTY AMERICAN
30. 3 PRIS YD 2.4 ZD 11.4
31. CONSTANTS
32. MATERIAL CONCRETE MEMB 1 2
33. MATERIAL NULL MEMB 3
34. SUPPORTS
35. 1 3 FIXED
36. LOAD 1 LOADTYPE DEAD TITLE DL OF GIRDER
37. MEMBER LOAD
38. 3 UNI GY -110.85
39. LOAD 2 LOADTYPE DEAD TITLE DECK SLAB WT
40. MEMBER LOAD
STAAD SPACE -- PAGE NO. 2

41. 3 UNI GY -63.75
42. LOAD 3 LOADTYPE DEAD TITLE FLOOR FINISH
43. MEMBER LOAD
44. 3 UNI GY -16.83
45. LOAD 4 LOADTYPE DEAD TITLE SW OF PIER
46. SELFWEIGHT Y -1 LIST 1 2
47. PERFORM ANALYSIS PRINT STATICS CHECK

P R O B L E M S T A T I S T I C S
-----------------------------------

NUMBER OF JOINTS/MEMBER+ELEMENTS/SUPPORTS = 4/ 3/ 2

SOLVER USED IS THE IN-CORE ADVANCED SOLVER

TOTAL PRIMARY LOAD CASES = 4, TOTAL DEGREES OF FREEDOM = 12

STAAD SPACE -- PAGE NO. 3

STATIC LOAD/REACTION/EQUILIBRIUM SUMMARY FOR CASE NO. 1
LOADTYPE DEAD TITLE DL OF GIRDER


CENTER OF FORCE BASED ON Y FORCES ONLY (METE).
(FORCES IN NON-GLOBAL DIRECTIONS WILL INVALIDATE RESULTS)

X = 0.599999997E+01
Y = 0.100000003E+02
Z = 0.000000000E+00

***TOTAL APPLIED LOAD ( KN METE ) SUMMARY (LOADING 1 )
SUMMATION FORCE-X = 0.00
SUMMATION FORCE-Y = -1330.20
SUMMATION FORCE-Z = 0.00

SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 0.00 MY= 0.00 MZ= -7981.20


***TOTAL REACTION LOAD( KN METE ) SUMMARY (LOADING 1 )
SUMMATION FORCE-X = 0.00
SUMMATION FORCE-Y = 1330.20
SUMMATION FORCE-Z = 0.00

SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 0.00 MY= 0.00 MZ= 7981.20


MAXIMUM DISPLACEMENTS ( CM /RADIANS) (LOADING 1)
MAXIMUMS AT NODE
X = 2.01264E-05 2
Y = -6.23860E-03 2
Z = 0.00000E+00 0
RX= 0.00000E+00 0
RY= 0.00000E+00 0
RZ= 1.44801E-05 4


STATIC LOAD/REACTION/EQUILIBRIUM SUMMARY FOR CASE NO. 2
LOADTYPE DEAD TITLE DECK SLAB WT


CENTER OF FORCE BASED ON Y FORCES ONLY (METE).
(FORCES IN NON-GLOBAL DIRECTIONS WILL INVALIDATE RESULTS)

X = 0.599999997E+01
Y = 0.100000003E+02
Z = 0.000000000E+00
STAAD SPACE -- PAGE NO. 4

***TOTAL APPLIED LOAD ( KN METE ) SUMMARY (LOADING 2 )
SUMMATION FORCE-X = 0.00
SUMMATION FORCE-Y = -765.00
SUMMATION FORCE-Z = 0.00

SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 0.00 MY= 0.00 MZ= -4590.00


***TOTAL REACTION LOAD( KN METE ) SUMMARY (LOADING 2 )
SUMMATION FORCE-X = 0.00
SUMMATION FORCE-Y = 765.00
SUMMATION FORCE-Z = 0.00

SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 0.00 MY= 0.00 MZ= 4590.00


MAXIMUM DISPLACEMENTS ( CM /RADIANS) (LOADING 2)
MAXIMUMS AT NODE
X = 1.15747E-05 2
Y = -3.58783E-03 2
Z = 0.00000E+00 0
RX= 0.00000E+00 0
RY= 0.00000E+00 0
RZ= -8.32751E-06 2


STATIC LOAD/REACTION/EQUILIBRIUM SUMMARY FOR CASE NO. 3
LOADTYPE DEAD TITLE FLOOR FINISH


CENTER OF FORCE BASED ON Y FORCES ONLY (METE).
(FORCES IN NON-GLOBAL DIRECTIONS WILL INVALIDATE RESULTS)

X = 0.599999997E+01
Y = 0.100000003E+02
Z = 0.000000000E+00

***TOTAL APPLIED LOAD ( KN METE ) SUMMARY (LOADING 3 )
SUMMATION FORCE-X = 0.00
SUMMATION FORCE-Y = -201.96
SUMMATION FORCE-Z = 0.00

SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 0.00 MY= 0.00 MZ= -1211.76


***TOTAL REACTION LOAD( KN METE ) SUMMARY (LOADING 3 )
SUMMATION FORCE-X = 0.00
SUMMATION FORCE-Y = 201.96
SUMMATION FORCE-Z = 0.00
STAAD SPACE -- PAGE NO. 5

SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 0.00 MY= 0.00 MZ= 1211.76


MAXIMUM DISPLACEMENTS ( CM /RADIANS) (LOADING 3)
MAXIMUMS AT NODE
X = 3.05572E-06 2
Y = -9.47187E-04 2
Z = 0.00000E+00 0
RX= 0.00000E+00 0
RY= 0.00000E+00 0
RZ= 2.19846E-06 4


STATIC LOAD/REACTION/EQUILIBRIUM SUMMARY FOR CASE NO. 4
LOADTYPE DEAD TITLE SW OF PIER


CENTER OF FORCE BASED ON Y FORCES ONLY (METE).
(FORCES IN NON-GLOBAL DIRECTIONS WILL INVALIDATE RESULTS)

X = 0.599999997E+01
Y = 0.500000017E+01
Z = 0.000000000E+00

***TOTAL APPLIED LOAD ( KN METE ) SUMMARY (LOADING 4 )
SUMMATION FORCE-X = 0.00
SUMMATION FORCE-Y = -2313.16
SUMMATION FORCE-Z = 0.00

SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 0.00 MY= 0.00 MZ= -13878.93


***TOTAL REACTION LOAD( KN METE ) SUMMARY (LOADING 4 )
SUMMATION FORCE-X = 0.00
SUMMATION FORCE-Y = 2313.16
SUMMATION FORCE-Z = 0.00

SUMMATION OF MOMENTS AROUND THE ORIGIN-
MX= 0.00 MY= 0.00 MZ= 13878.93


MAXIMUM DISPLACEMENTS ( CM /RADIANS) (LOADING 4)
MAXIMUMS AT NODE
X = -2.75387E-19 4
Y = -5.42432E-03 4
Z = 0.00000E+00 0
RX= 0.00000E+00 0
RY= 0.00000E+00 0
RZ= 0.00000E+00 0



************ END OF DATA FROM INTERNAL STORAGE ************


STAAD SPACE -- PAGE NO. 6

48. FINISH