Eight steps of bridge construction

1.

2. Identify an ideal place to build the bridge. A lot of legwork goes into determining the ideal site to build anything, and when you’re talking about something as expensive as a bridge, engineers are even more careful. The engineering team will send out surveyors, people who use electronic measuring devices to make a map of the general area. From this map, they will make calculations and determine the length and placement of the bridge.

3. Design the bridge. The engineer will take into account the potential traffic load of the bridge and use steel design manual and computer programmes to aid in the bridge designing process. The materials chosen should also take into consideration the inspection and upkeep costs after the bridge is built.

4. Break ground. Once the design has been finalized and stamped with approval, the actual building can begin. This will involve excavation or filling the banks on either side, stabilizing the ground where the supports will be placed and, depending on what type of bridge is going to be built, pouring concrete.

5. Assemble the steel. Some bridges are built on site and some are put together in pieces small enough to ship to the location and then assembled. Using the anchors placed in the concrete, the steel units are put together like tinker toys using nuts and bolts.

6.

7. Pave the new bridge. This is done with paving machines. The government agency sponsoring the project might also include a repaving of the surrounding roadway as well.

8. Have the ribbon cutting ceremony. Building a bridge is a tremendous accomplishment. After months or possibly years of building this bridge the dust can settle and the public can finally use it.

History of tunnels

A tunnel is an underground or underwater passage that is primarily horizontal. A tunnel may be for foot or vehicle traffic, for rail traffic, or for a canal. Some tunnels are aqueducts to supply water for consumption or for hydroelectric stations or are sewers. A tunnel is relatively long and narrow; the length is often much greater than twice the diameter.

Greeks and Romans took all the knowledge of Babylon and Ancient Egypt, and improved it. With tunnels they were able to transform marches, transport water through mountains, and create pedestrian tunnels trough very harsh terrains. To this day historians wonder how much workforce was involved in the construction tunnel between Naples and Pozzuoli that was created around 36 BC. This incredible structure was 4800 foot long, 25 foot wide and 30 foot high, and it even had ventilation shafts. Less than 100 years later in 41 AD, Romans used around 30,000 workers to build even larger tunnel that was 5.6 km long.

In European Middle Ages, tunnels were almost exclusively used for mining or for military. After public transportation they finally started to grow under the influence of Renaissance and trading with distant lands. Hundreds of smaller tunnels were created between mid-1600s and 19th century, but by then new driving force of tunnel construction came – railroads. This new form of transport soon enabled spreading of tunnels across entire world.

Choice of tunnels vs. bridges

Bridges usually require a larger footprint on each shore than tunnels. In areas with expensive real estate, such as Manhattan and urban Hong Kong, this is a strong factor in tunnels’ favor. Boston’s Big Dig project replaced elevated roadways with a tunnel system to increase traffic capacity, hide traffic, redecorate.

Other reasons for choosing a tunnel instead of a bridge include avoiding difficulties with tides, weather and shipping during construction, aesthetic reasons (preserving landscape and scenery).

However, there are particular hazards with tunnels, especially from vehicle fires when combustion gases can asphyxiate users, as happened at the Gotthard Road Tunnel in Switzerland in 2001.