RoTao elevated track is a concrete bridge construction offers two lanes for designated rubber-tyred vehicles.
There is an ongoing need to improve the structural design of bridges so that they can be built with better weather resistance, greater spanning distance, higher structural quality, affordable pricing, reduced construction difficulty, and faster construction speed. Bridges come in many structural forms, which are characterized by how they distribute forces such as bending, tension, compression, shear, and torsion. The most common structural forms include, but are not limited to, beam, cantilever, arch, truss, suspension, and cable-stayed bridges. Due to shorter construction time and lower manufacturing and maintenance costs, both concrete and reinforced concrete became the world’s most common building materials for bridges.
Regardless of the variation in design, the existing girder bridge structure faces multiple challenges.
(1) Each girder of the bridge is heavy, so there is a need for structural supports integrated with the girder design to stabilize and support the bridge. The structural supports normally require additional vertical space, leading to a higher vertical height of the bridge structure. Higher bridges are generally less safe and require even higher clearance if another bridge is built over existing bridges.
(2) The heavy girders require more supporting substructures (primarily piers) within a certain length. In other words, it ultimately limits how far apart the two adjacent piers can be. Therefore, more piers and shorter girder spans are needed to cover a great distance.
(3) Heavier girders require increased construction materials, longer construction time, and more maintenance.
(4) The issue with existing bridges is their tolerance to strong wind forces, particularly if the bridge has a long span. In such a case, the vibration of the structure becomes strong enough to cause damage to the bridge structure and may ultimately tear down the bridge if resonance occurs.
(5) Wind may also create traffic and safety issues on the elevated height of the bridge. In case the traffic is subject to wind force, the vehicles are at risk of tipping over, spinning out, or being blown off the bridge deck. This is especially true if one of the vehicles is tall, narrow, and light; its driving ability is ultimately reduced due to the loss of traction.
(6) Rain, hail, and snow create difficult driving conditions on bridges and also affect their structures. Under freezing conditions, water on the deck surface (e.g. standing water) could freeze and turn into ice, which creates a driving hazard. Moreover, snow plowing is hard due to the confined deck space.
(7) The aerodynamic forces on the vehicles as they meet have a significant effect on the vehicle handling stability, particularly the vehicles are tall, narrow, light, speeding, and close to each other. When two vehicles pass each other in opposite directions, it causes strong turbulence in the narrow space between them. The turbulence shakes the vehicles and causes the tires to lose their grip on the ground surface.
(8) The needs to separate opposite direction traffics which prevents head-on and side collisions. The most common physical barrier, Jersey barrier, is approximately 80 centimeters tall. It is sufficient for protecting smaller vehicles. However, it is not as suitable for larger vehicles such as buses and trucks; these vehicles might still tip over the barrier onto the other lane.
(9) It is also important to consider the emerging use of auto-driving vehicles on the bridge structure. auto-driving vehicles (AV), typically use cameras, as well as many other sensors, to continuously sense their surroundings and drive accordingly. AC functions work best when there are remarkable landmarks such as buildings, road curbs, signs, etc. During poor weather conditions, the camera is not able to view its surroundings as readily due to the reduced visibility. Thus, the camera and the internal system of AV are confused by the parameters of the surrounding area.
Due to the issues noted above, a lot of maintenance is required to ensure that the structural integrity and the stability of the bridge structure are up to standards. A significant modification to the bridge structure is needed to reduce the maintenance needed for its structure and safety.
The RoTao elevated track provides a design for a modified girder bridge structure that comprises a tall and narrow central-wall-beam that separates two lanes of traffic in opposing directions, lower parapets on each side of the girder, open bridge decks with optional heated wheel paths, auto-driving reference guides, and electric live rails. The design comprises the following components: (1) a girder that sits on top of reinforced piers; (2) a central wall-like beam comparable to traffic height located at the median of the bridge, which separates the two lanes for traffic. The wall beam is tall, hollow, and narrow; it serves to suspend and support most of the girder’s weight and load; (3) the open deck of each lane is hollow and contains two runways that match a vehicle’s two-wheel paths: the near-wall runway is situated close to the central-wall-beam, and the near-parapet runway is close to the parapet; (4) the two wheel-path runways are equipped with AV (autonomous-driving vehicle) reference driving guides to ensure that the wheels are on their respective runways. (5) the whole girder has holes that hold prestressed cables or rebars to support the beams and decks.
The purpose of the design is to mitigate the issues with existing girder bridge designs using the improvements noted above, which include: (1) maximizing the structural efficiency of the strength-mass and stiffness-mass ratios with the tall and narrow central-wall-beam; (2) making the girder bridge lighter in weight with hollow decks; (3) increasing wind-resistance capability and reducing eddies from strong winds by modifying the deck and girder structure to allow wind to flow through the open decks; (4) providing a safer ride to vehicles on both of the windward side and leeward side of the tall central-wall-beam; (5) providing a safer ride to vehicles on hollow and heated decks, which remove water quickly from rain, hail, and snow; (6) lowering the deck height of the bridge with the central-wall structure to improve space utilization; (7) providing reliable auto-driving reference guides and the ability to install sensors, wireless signal adapters, and traffic signs/signals on the central-wall-beam and parapets, so they can provide self-driving vehicles with a better reference to perform reliably; (8) reducing interference to traffic at ground level with a long span capability; (9) reducing maintenance of the bridge structure with the combined improvements; (10) improving the aesthetic look of the structure, unblocking obstructions to scenic views, and making it more remarkable.