With the rapid development of society and the economy, the transportation pressure in cities is increasing day by day. The construction of urban road bridges and their projects is also increasing. At the same time, with the development of modern technology and the standardized requirements of modern engineering construction, the traditional construction method of on-site casting for highway bridge projects can no longer meet the development needs of modern urban road bridges. This is because it has problems such as high noise pollution during construction, long construction period, and high consumption of resources, energy, manpower and materials. The extensive adoption of prefabrication and assembly technology in urban road bridges can not only ensure the project quality, but also reduce the labor intensity of construction, thereby improving the work efficiency and quality of the project. At the same time, it can also ensure the environmental protection, durability and safety of the bridges. 

 Concept of Prefabrication and Assembly Technology 

The segment prefabrication and assembly technology of bridges refers to the construction technology in which the girder is divided into several parts along the longitudinal direction of the bridge, assembled in a factory or a nearby girder manufacturing plant, and then transported to the bridge deck for further assembly to form a bridge. A fully prefabricated concrete bridge is a bridge in which the main components of the upper and lower structures of the bridge are assembled in a factory, prefabrication plant or on-site. According to different structural characteristics such as the cross-section form of the bridge deck and the span size, the main girders of the upper part of the bridge are segmented by longitudinal vertical joints to divide the bridge width, and the girders are prefabricated segment by segment across the entire span; or the bridge span is divided by transverse vertical joints, and the full-width segments are prefabricated, and the bridge deck railings are prefabricated in sections. For the lower structure of the bridge, parts such as the cap beams, piers, abutment bodies and retaining walls of the bridge piers are prefabricated as a whole or in sections according to their respective sizes. Among them, the non-prefabricated parts are mostly the connection structures of the upper structure of the bridge, the bridge deck pavement layer and the bearings at the bottom of the bridge piers of the lower components. Since the assembled segments are manufactured in a prefabricated component factory, they are transported to the construction site by transport vehicles, and then assembled in a specific order and prestressed to form a complete load-bearing bridge structure. Therefore, this method has higher requirements for deformation control during the prefabrication stage, and has a great impact on many issues such as the vibration generated during the transportation of the segments, the safety during the system transformation process, and the health monitoring of the bridge after completion. 

 Advantages and Disadvantages of Prefabrication  Assembly Technology 

The key components of the prefabrication and assembly technology are centrally manufactured in the factory, adopting an industrialized and mass production model. At the construction site, only machines are needed to assemble the components, which is of great significance for promoting the standardization of bridge construction. Compared with the conventional bridge engineering technology, the prefabrication and assembly technology has obvious advantages in many fields such as environmental protection, quality control and progress control. Firstly, in terms of the environment, the conventional construction process occupies a large amount of space, and the construction site is relatively messy, causing certain negative effects on the surrounding traffic and environment. In contrast, the prefabrication and assembly technology occupies less space, and can save energy and protect the environment throughout the construction process, greatly reducing the impact on the surrounding transportation. Secondly, in terms of project quality, the traditional engineering technology has many problems, while in the prefabrication and assembly technology, due to the adoption of standardized operation methods, the project quality is better guaranteed. From the perspective of workers, the traditional construction technology has a low level of mechanization and a large amount of manual work. However, the prefabrication and assembly technology mainly relies on mechanization, with relatively small investment in labor and costs, and higher work efficiency. Because the prefabrication and assembly technology is operated in an industrialized factory, it is easier to construct than cast-in-place concrete, and has a better appearance. It can be decorated without the need for a repainting process, reducing the materials and labor required for painting, and minimizing the construction waste, dust, etc. In addition, the segments of this technology are lighter in weight and smaller in size, making them easy to transport. The assembly and construction speed is relatively fast. Moreover, since the prefabricated components are manufactured using industrialized methods to make different structural components, the processing of steel molds can be used to achieve the manufacturing of composite components, and the manufacturing process cost is relatively low. The exterior wall panels of prefabricated and assembled buildings can undergo a variety of decorative processing, such as designing and inlaying tiles, stones, fair-faced concrete, etc. 

 The prefabrication and assembly technology of prefabricated segments requires a large amount of investment in the early stage of construction, mainly including the construction of the prefabrication site, the preparation of transportation equipment, the beam erection equipment, etc. In addition, since the segments are connected by dry joints, if not properly handled, it is impossible to effectively prevent the penetration of moisture and acid solutions in the air, resulting in a decrease in the durability of the building, especially in coastal areas such as Xiamen. However, due to the material of the structure, especially the prestressed tendons, their tensile resistance is not strong, and their material index is relatively high, and the economic benefits are relatively high. The construction process of the prefabrication and assembly technology of prefabricated segments is cumbersome, with a high technical content, and the overall organization and coordination work is relatively difficult.