WINDSHIELD PROTECTION FENCE FOR BRIDGES PANACOR WB
The wind barrier is designed to cut the wind speed in extreme wind areas such as bridges and highways, to prevent the vehicle from crashing and to provide comfortable driving.
The viaducts on roads and highways are designed to cut the speed of the wind in extreme winds, such as bridges, to prevent the vehicle from crashing and to provide comfortable driving. These wind hielding, also called wind barriers or wind fences, aim to reduce the effect by dividing the incoming wind. In the meantime, it takes over most of the wind load. Design, manufacturing, installation and maintenance processes should be managed very well. Static calculation is important in the design phase.
A truck overturns when it receives the pressure of the wind when entering a viaduct near Barcelona
Figure 1: Wind barrier exterior view
Figure 2: Wind barrier interior view
A wind barrier or wind protection fence usually is required to ensure uninterrupted traffic in practically all weather conditions up to wind speeds of 180 km/h (50 m/s) over the bridge.
Figure 3: Interior view of the wind barrier in a bridge with guard rail
Figure 4: General view of the wind barrier model
Figure 5: Detail of the conection between the wind barrier and the bridge deck
DESIGN THROUGH COMPUTATIONAL FLUID ANALYSIS
To assess the efficiency of windshield protection and facilitate the analysis in terms of traffic safety, a characteristic cross section of each particular bridge is analyzed. In windscreen protection efficiency analyzes, the wind speed of 180 km/h (50m/s) is taken, which is considered to be the upper limit of speed at which the reduced traffic of personal vehicles on the open trajectory of the fast road can still be maintained.
Figure 6: Pressure on te Wind barrier. Exterior view
Pressure on the wind barrier. Interior view
The simulation is done on the condition of an unprotected object and on a protected with windshield. The next step was to analyze the impact of the wind on the vehicle, which is located on different traffic lanes. An analysis is made – a comparison between a protected and unprotected bridge. On the basis of the results of the analysis – the reduction of the pressures on the vehicles, is concluded that as an optimal solution to be adopted with the windshield height and the quantity of lamellas of corrugated shape and the height of those lamellas, which are of armored UV resistant acrylic glass. The distance between lamellas is also defined.
Figures 8 and 9: Wind pressure on the wind barrier
CFD analysis – bridge with/without windshield
On the basis of the CFD (Computational Fluid Dynamics analysis) for wind direction 0 ° and ± 6 ° and the observation of European norms (EN 1794 -1 / 1794-2) we design, construct and supply any type of wind barrier. For example, the one with the following characteristics:
- The protective wind fence is 3.20 m high and it has 7 convex (half-barrel shaped) acrylic elements. The gap between the glass elements is 125 to 175 mm.
- Steel columns can have 3.0 m longitudinal spacing and are rectangular with dimensions 250/150/8 mm.
- Acrylic glass elements are of a corrugated shape, 140 mm wide and 300 mm in height. The thickness of the acrylic glass is 15 mm. The glass is reinforced with polyamide threads or stinless steel rods or wires, which prevent the fragile fracture in the case of shock loads.
- Acrylic glass elements are fixed on steel columns by special bearings in which 4 mm thick EPDM (rubber) bands are installed which allow temperature stretching and prevent rigid fixation of glass elements (allow the rotation of glass elements on the bearing with simultaneous dampening of vibrations.
- The installation of acrylic glass elements is planned so that simple assembly, disassembly (replacement of elements in the case of damage) and cleaning is enabled.
- Wind barriers also serves as safety fence (inspection passages with a width of 0.75m).
Figure 10: Pressure on the wind barrier. Cross section
DURABILITY AND FATIGUE TEST
Acrylic elements are made of PMMA reinforced with polyamide threads, stainles steel rods or with polycarbonate. Real scale fatigue test for 30 years durability were done to verify long term durability.
Picture 1: Acrylic panel thermoformed ready to be tested
Pictures 2, 3 and 4: Acrylic elements on the testing bench during the fatigue test
Wind barriers utilizes thermoformed parts for maximum stiffness, minimum stress, and proper wind deflection:
Figure 11: Acrylic element deflection
Figure 12a: Acrylic element stress. Exterior view
Figure 12b: Acrylic element stress. Interior view
Figure 13: Cross section with acrylic element reinforcements stress
Figure 14: Acrylic element reinforcements stress. Rods in red color with bigger stress than blue ones
Our acrylic elements for wind barriers has outstanding weather resistance, high transparency and lightweight.
The wind barrier structure is made of steel grade S355 according to EN 10025-2. Anti-corrosion protection of hot-dip galvanised protection is determined for the corrosion category and the expected durability of the protection (long) over 15 years according to ISO 12944-5.
Class corrosivity of the environment at the site of the bridge determine the anti-corrosion protection system. For example, for a C5M Class corrosivity, a double anti-corrosion protection system of 85 micrometers hot dip galvanized and an additional coloring in three layers (base coat, middle- coat and finishing coat, an individual film thickness of 80 µm , total 320 µm ) can be adopted. Base and middle coatings are based on epoxy resins and a finishing coat is based on polyurethane.
Corrosion protection must be chosen so as to enable repair and maintenance without any noticeable effect on the quality of care. Take into account the effect on the environment, avoiding the use of hazardous substances.
Our services include all labor, equipment and materials necessary for the production of wind barriers, including all necessary steel anchor plate for anchoring the wind barrier construction in steels and rubber seals on the joints enclosure and corrosion protection. Execution, quality control and calculation according to the Program of control and quality assurance.
Bridge cross sections with different wind velocity:
Figure 15: Detail of the cross section obtained from computational fluid dynamics
Figure 16: View from the interior side of the viaduct obtained from computational fluid dynamics
Figure 17: View from the exterior side of the viaduct obtained from computational fluid dynamics
Figure 18: Bridge and wind barrier general view. It can be seen the shadow area generated by the wind barrier
Figure 19: View from inside the viaduct of wind behavior obtained from computational fluid dynamics
Figure 20: Viaduct cross section of wind behavior obtained from computational fluid dynamics