Bridge has a long history in human societies, so that the first and oldest form of bridges is probably the time when mankind, using the trunk of trees and stone, was able to cross the rivers, valleys, and ravines Provided. Later, putting a piece of stone or a piece of wood on two or more bridges was a little more meaningful.
It was built of the oldest bridges in Pasargad, which the English archaeologists have identified and excavated from under the soil. The bridge is 16 meters in width and the wooden surface is constructed on 3 rows of the base and each row contains 5 stone columns.
But with the passage of time and technology advances bridges have undergone tremendous changes, and several methods have been developed for their construction. These methods include:
1- Span-by-Span span:
Open span method is one of the main methods for constructing multi-span bridges, as the name implies, in this way, the shaftur is completely installed in a bridge span, and then the installation is started at the next span they do. Similarly, they will continue to install bridge bridges. This build method allows the entire span to be installed at one time. This method is divided into the following subcategories according to the type of method used in the implementation and construction of the bridge and the means used in the execution:
• Full Span Method (FSM)
• Moveable Scaffolding Method
• The method of slipping sideways
2- Run by Balanced Cantilever Method
Another method of building a bridge is a balanced method. This construction method is suitable for both on-site and prefabricated implementations. In prefabricated state, single individual pieces are symmetrically mounted to a base. As the shafts are gradually mounted on the sides of the base, the bending anchors to the sides of the base balance each other on the sides of the base. When the trough reaches the middle of the span, the final piece (the final piece) is connected at a distance between the spigots installed on the adjacent base. This process continues until all of the bridge spans are completed.
3- Run in an incremental Launching Method
Other methods of constructing a bridge are an advanced method. This method is essentially a sophisticated method. In years when this method was not yet invented, in every large plasticization project, the cost to workers was the largest share of the cost of bridging.
Therefore, any innovation and innovation that could reduce worker monitoring of the project and increase the share of workshop equipment and machinery in the project administration was a very influential way in the project economy. One part of this way, it could be that the parts after production at the factory, run quickly. Consequently, designers and contractors of various bridges also paid attention to this aspect of the construction of the bridge.
4. Run by Progressive Placement Method
This method is, in comparison with other methods of building the bridge described, a method with construction operations in one direction. All consoles are placed at the tip of the previous pieces, respectively. Both precast and cast-in-place can be used for bridge components. A common method for constructing bridges is through the use of temporary towers as an extension to the bridge. According to Mathivat (1983), this method is suitable for openings 50-30m. (The source of the mentioned methods: Bridge construction methods by Majid Baraghian (Tabriz University of Technology))
Also, for better performance of bridges against their loads such as compressive and tensile loads, as well as fatigue, they went to products that have better behavior and properties when faced with these loads, the most important of which can be pointed to composite products. With special features, these products have been instrumental in building bridges with good behavior versus loads, which include:
Resistant to rust
Resistant to corrosion (resistant to acidic and playful environment)
Resistant to impact
Tensile strength of at least double steel
The compressive strength is at least equal to steel
Resistant to bending
High shelf life
Do not distract
Reduce project costs
Low specific weight
High ductility and production at arbitrary sizeComposite bridges, due to reduced maintenance costs and high durability, no need to paint because of the prevention of rust or beauty, the high speed of construction, as well as low weight and comfortable placement are highly appreciated by European engineers and Americans.
In these bridges, surfaces are also made of composite panels in portable porcelain and porcelain in continuous joints, which have a much higher strength than steel. Composite surfaces can have a bearing capacity of about 6 to 7 times the value of reinforced concrete columns, and they perform better than bridges made by old products, such as concrete columns, while only 20% of their weight On the other hand, unlike steel, it has a long shelf life, and the lack of corrosion can easily be used to build bridges on rivers, seas and lakes, and for years, without maintenance and maintenance Best used.Composites, because of their high cylinder strength, can fill the entire mold and complete the shape of the desired component without any waste. This composite feature produces pieces with impressive exterior effects. On the other hand, this feature designs structures with eye-catching and stunning architectures, which leads to visual beauty and attraction of tourism to the region..
Easy installation and high speed installation There is no need for a lot of workforce as well as heavy machinery from the cases that have been significantly reduced by the cost of installation and construction of projects, and have led to the construction of many bridges at different locations, such as Icelandic National Park and Chandigarh Is.
The first bridges built in this way in one of the West Virginia villages of the United States and later extended to countries such as Denmark, experiments on these bridges showed that the use of composites in the construction of these bridges was very useful and caused Increased strength and durability.Easy installation and high speed installation There is no need for a lot of workforce as well as heavy machinery from the cases that have been significantly reduced by the cost of installation and construction of projects, and have led to the construction of many bridges at different locations, such as Icelandic National Park and Chandigarh Is.
The first bridges built in this way in one of the West Virginia villages of the United States and later extended to countries such as Denmark, experiments on these bridges showed that the use of composites in the construction of these bridges was very useful and caused Increased strength and durability