Classical Wind Analysis of Truss Bridges.ppt

Wind analysis of truss bridges have been described in this presentation.

1. Wind Analysis of Trussed Bridges
Muhammad Akram Tahir
Associate Professor
SIIT-Thammasat University
School of Civil Engineering-
AIT
CE 804 Design of Buildings & Bridges
27/11/199
8

2. Wind Pressures on Bridge
•Unloaded Bridge
50 psf on truss area exposed to wind
•Loaded Bridge
30 psf on truss area
200 plf on vehicle acting at 5' from Road
surface
SIIT-Thammasat University
School of Civil Engineering-
AIT

3. TRUSS AREA
•1.5 to 2.00 times of the exposed
area of one truss
•Exposed area consists of
lengthaxawidth of members plus
gusset areas
•Widths of various members as
found in preliminary design
SIIT-Thammasat University
School of Civil Engineering-
AIT

4. Widths (in absence of
design)
SPAN (ft) WIDTH (Inches)
TOP/BOT VER DIAG
<100 20 6 8
101-150 24 7 9
151-200 28 810
>200 32 912
SIIT-Thammasat University
School of Civil Engineering-
AIT

5. <100 2.50
101-150 3.50
151-200 4.00
>200 5.00
SIIT-Thammasat University
School of Civil Engineering-
AIT
Gusset Areas
(in absence of design)

Span (ft) Area per Joint (ft
2
)

6. Load Configuration

SIIT-Thammasat University
School of Civil Engineering-
AIT
5'
1-1.5'
200 plf

7. Load Configuration

Top Chord
Bot Chord
Top Chord
Bot Chord
Vehicle
Full Wind Pressure Red Wind Pressure
SIIT-Thammasat University
School of Civil Engineering-
AIT

8. 3-D View
SIIT-Thammasat University
School of Civil Engineering-
AIT

Lee Ward
Top Lateral Bracing
Bot Lat BracingWind Ward

9. Overturning Effect
(Bridge UNLOADED)

SIIT-Thammasat University
School of Civil Engineering-
AIT
Wind Ward
Lee Ward
2R 2R

10. Loaded Bridge

SIIT-Thammasat University
School of Civil Engineering-
AIT
Wind Ward
Lee Ward
2R 2R

11. Windward Truss

SIIT-Thammasat University
School of Civil Engineering-
AIT
Equivalent Action
Wind
Reaction

12. WINDWARD TRUSS

SIIT-Thammasat University
School of Civil Engineering-
AIT
R
R
2R/N 2R/N 2R/N
R/N
R/N
N=No of Panels
Tension Compression

13. Leeward Truss

SIIT-Thammasat University
School of Civil Engineering-
AIT

14. LEEWARD TRUSS
SIIT-Thammasat University
School of Civil Engineering-
AIT

R
R
2R/N 2R/N 2R/N
R/N
R/N
N=No of Panels
Tension Compression

15. LATERAL EFFECTS
•On Top/Bottom Lateral Bracings
•On Top/Bottom Chord of Trusses
SIIT-Thammasat University
School of Civil Engineering-
AIT

16. Top Lateral Bracing

SIIT-Thammasat University
School of Civil Engineering-
AIT
Load on Top Chord Only
Critical when Bridge Unloaded
WW
LW
50 psf

17. Bottom Lateral Bracing

SIIT-Thammasat University
School of Civil Engineering-
AIT
Load on Bottom Chord Only
when Bridge Unloaded
WW
LW
50 psf

18. Bottom Lateral Bracing

SIIT-Thammasat University
School of Civil Engineering-
AIT
Load on Bottom Chord + Vehicles
when Bridge Loaded
WW
LW
30 psf
200 plf

19. Top/Bot Lateral Bracing

WW
LW
SIIT-Thammasat University
School of Civil Engineering-
AIT

20. Top/Bot Lateral Bracing

SIIT-Thammasat University
School of Civil Engineering-
AIT
WW
LW
Tension Compression
Inactive Struts

21. Top/Bot Lateral Bracings
LW
WW
LW
SIIT-Thammasat University
School of Civil Engineering-
AIT

22. Combined Effects: WINDWARD TRUSS

SIIT-Thammasat University
School of Civil Engineering-
AIT
Overturning
Gravity

23. Combined Effects: LEEWARD TRUSS
SIIT-Thammasat University
School of Civil Engineering-
AIT

Overturning
Gravity

24. Combined Effects: WINDWARD TRUSS

SIIT-Thammasat University
School of Civil Engineering-
AIT
Top Lateral
Bracing
Gravity

25. Combined Effects: LEEWARD TRUSS

SIIT-Thammasat University
School of Civil Engineering-
AIT
Top Lateral
Bracing
Gravity

26. Combined Effects: Windward TRUSS
SIIT-Thammasat University
School of Civil Engineering-
AIT

Bot Lateral
Bracing
Gravity

27. Combined Effects: Leeward TRUSS
SIIT-Thammasat University
School of Civil Engineering-
AIT
Bot Lateral
Bracing
Gravity