Following a series of catastrophic bridge failures, the adverse effects of wind loading on bridges has become a widely discussed topic in the realm of bridge design and research. Currently however, the majority of research focuses on the contribution of wind in long span bridge design. This is primarily because long span bridges have a greater inherent tendency to become aerodynamically unstable. Nonetheless, wind can also contribute to the shear and moment of short span bridges, thereby influencing the limit state of various components in these short span bridge systems. To narrow this scope, the following presentation focuses specifically on the contributions of wind to the shear and moment of slab and girder bridge decks. These contributions are quantified by a model that calculates the shear and moment due to wind loads for a number of variable parameters including angle of impact, bridge height, span length, and deck thickness. Ultimately, it is found that angle of attack has the greatest impact on moment, while span length has the greatest impact on shear about center span.

1. AVI GORI
JULIANNE CRAWFORD
WIND EFFECTS ON SHORT SPAN
BRIDGE DECKS

2. HISTORY OF WIND EFFECTS ON BRIDGES
❖ Tacoma Narrows Bridge in 1940
❖ Hood Canal Bridge in 1979
❖ Sabo Pedestrian Bridge in 2012

3. HISTORY OF WIND EFFECTS ON BRIDGES
❖ Tacoma Narrows Bridge in 1940
❖ Hood Canal Bridge in 1979
❖ Sabo Pedestrian Bridge in 2012
WHAT IS WIND’S EFFECT ON SHORT SPAN BRIDGES?

4. AASHTO Wind Equations
Where:
PB
= Base Wind Pressure (ksf)
VDZ
= Design wind velocity at design elevation Z (mph)
Where:
V0
= Friction velocity for various upwind surface characteristics (mph)
V30
= Wind velocity at 30.0ft above low ground (mph)
VB
= Base wind velocity of 100 mph at 30.0ft height (mph)
Z = Height of structure at which wind loads are being calculated (ft)
Z0
= Friction length of upstream fetch (ft)

5. DERIVATION OF THE AASHTO VELOCITY EQUATION
Wind velocity (u) depends on elevation (Z),
atmospheric conditions, air density, etc.
Derived relationship:
k empirically found = 2.5 for stable conditions

6. Derivation of the AASHTO Pressure Equation
The theoretical equation for pressure is
proportional to density and velocity (U) squared
The theoretical drag force equation is
found by multiplying by surface area (A)
Equations Used in Our Model:

7. OUR WIND MODEL

8. CONTRIBUTION OF
WIND TO:
1. SHEAR ABOUT CENTER
SPAN DUE TO LATERAL
WIND LOAD (DRAG)
2. MOMENT ABOUT
CENTER SPAN DUE TO
VERTICAL WIND LOAD
(LIFT)

9. MODEL ASSUMPTION

10. ❖ Wind Pressure
○ Deck Height
○ Surface Conditions
❖ Deck Type
❖ Angle of Attack
❖ Deck Thickness
❖ Span Length
VARIABLES
Where:
PB
= Base Wind Pressure (ksf)
VDZ
= Design wind velocity at design elevation Z (mph)
Where:
V0
= Friction velocity for various upwind surface characteristics (mph)
V30
= Wind velocity at 30.0ft above low ground (mph)
VB
= Base wind velocity of 100 mph at 30.0ft height (mph)
Z = Height of structure at which wind loads are being calculated (ft)
Z0
= Friction length of upstream fetch (ft)

11. ❖ Wind Pressure
○ Deck Height
○ Surface Conditions
❖ Deck Type
❖ Angle of Attack
❖ Deck Thickness
❖ Span Length
VARIABLES

12. VARIABLES
❖ Wind Pressure
○ Deck Height
○ Surface Conditions
❖ Deck Type
❖ Angle of Attack
❖ Deck Thickness
❖ Span Length
SLAB

13. VARIABLES
❖ Wind Pressure
○ Deck Height
○ Surface Conditions
❖ Deck Type
❖ Angle of Attack
❖ Deck Thickness
❖ Span Length
GIRDER

14. VARIABLES
❖ Wind Pressure
○ Deck Height
○ Surface Conditions
❖ Deck Type
❖ Angle of Attack
❖ Deck Thickness
❖ Span Length

15. VARIABLES
❖ Wind Pressure
○ Deck Height
○ Surface Conditions
❖ Deck Type
❖ Angle of Attack
❖ Deck Thickness
❖ Span Length
(t)

16. VARIABLES
❖ Wind Pressure
○ Deck Height
○ Surface Conditions
❖ Deck Type
❖ Angle of Attack
❖ Deck Thickness
❖ Span Length
(L)

17. SENSITIVITY ANALYSIS
SLAB GIRDER
Deck Thickness: 56.8in
Deck Height: 30ft
Angle of Attack: 45°
Span Length: 60ft
Deck Thickness: 16in
Deck Height: 30ft
Angle of Attack: 45°
Span Length: 30ft
TYPICAL SLAB TYPICAL GIRDER

18. SENSITIVITY ANALYSIS
SLAB GIRDER
Deck Thickness: 39-72in
Deck Height: 15-60ft
Angle of Attack: 0-180°
Span Length: 50-125ft
Deck Thickness: 10-24in
Deck Height: 15-60ft
Angle of Attack: 0-180°
Span Length: 28-40ft
VARIABLE RANGES VARIABLE RANGES

21. RESULTS SYNTHESIZED

22. LOCATION
FINDINGS
SUMMARY
IN OPEN COUNTRY AND COASTAL ENVIRONMENTS, THE
CONTRIBUTION OF WIND IS NON-NEGLIGIBLE
LATERAL WIND FORCES COMPRISE A SUBSTANTIAL PORTION
OF THE TOTAL LATERAL FORCES
MOMENT: ANGLE OF ATTACK
SHEAR: SPAN LENGTH
LATERAL LOADS