Research On Designing Method Of The Medium And Small Span Prestressed Concrete Highway Bridge Based On Driving Comfort

Prestressed concrete simply supported plate beam bridge with its simple structure, easy construction design and construction technology and so many more mature characteristics, which has been widely adopted in our small and medium-span highway bridge construction. However, too much creep generally appeared in prestressed concrete simply supported beam bridge in use. Excessive the arch caused by the creep of the bridge deck, especially for multi-span and equal span bridges, forming a regular periodic wave-shaped linear, producing a cyclical waveform disturbance to the high-speed vehicles, leading to greater abnormal vibration to the vehicles, which seriously affect the high-speed driving comfort. Nowadays with the accelerating speed and the increasing carrying capacity of the vehicles, more and more people pay attention to driving comfort, and urgent demand it, therefore, in order to solve this problem, it is necessary to explore the design-based method of driving comfort for small and medium-span highway bridges. But China's current road bridge criterion doesn't have relevant provisions to design for driving comfort. Chongqing-Guizhou Expressway, PingTanZi bridge as the example, this paper undertake the following tasks:â‘ comparing and analyzing of several commonly used international evaluation indicators of driving comfort, as well as train ride comfort evaluation index of China's railway department, reference to China's auto industry, China's highway sector in assessing the vehicle ride comfort and comfort evaluation methods in the study of road surface roughness. This paper discusses for highway driving comfort evaluation system.â‘¡Driving comfort index can be reflected by bridge camber in this design specifications. To facilitate the design of driving comfort factor,this paper explores the mathematical relationship between driving comfort index and bridge camber. The impacting factors of the mathematical relationship such as the bridge's span,span number and driving speed.â‘¢According to uncomfortable, this paper put forwards design concept based on driving comfort, making comfort as safety, aesthetics, economy, durability and so on as the same considered design principles. And this paper exploratory proposes new design methods to small and medium span prestressed concrete bridges of freeway based on driving comfort, in accordance characteristics of present design methods.â‘£Proposing a design method that for the partially prestressed concrete structures, using the lower limit of requirements of crack resistance (in the effect of short-term load combinations, the tensile stress in the edge of tension of cross-section is not more than 0.7 times of the axis of the tensile strength standard data of concrete) to control the amount of prestressed reinforcement in order to reduce the degree of pre-stressed. And giving a example of new-designing to show that, it not only suffices the safety, durability, etc., but also reduces the big deflection upwards caused by the creep.