Response Analysis Of Long-Span Bridge Under Vehicle Load Based On Micro-Simulation Of Three-Lane Traffic Flow

The long-span bridge is an important part of the highway transportation network, whose safety and applicability is directly related to the traffic circulation of road network. In the normal operating condition, long-span bridges are not only subjected to the dead load, such as the self-weight of structure and pavement, but also bear all kinds of variable load. Among all the variable loads, the vehicle load is the most characteristic one of the road industry, and also the most complex one. Besides, it is the main factor influencing the safety of long-span bridge.So it has very vital significance to assess vehicle load effect accurately. Therefore, it is the key of the study to accurately obtain the vehicle load data for the discussion of whether the actual operational characteristics of the vehicle load effect or the existing design vehicle load. In this paper, the microscopic traffic flow simulation system is firstly established, and then the vehicle load response of a two-way six-lane long-span cable-stayed bridge is analyzed and assessed in detail.The specific process is as follows:Firstly, the simulation system of the long-span bridge under random traffic flow based on the three-lane cellular automata traffic flow model is established and refined, and the vehicle-bridge system analysis framework based on microscopic traffic flow is built through combination with the BDANS analysis system.Secondly, seven typical conditions of the cable-stayed bridgeis selected, and a detailed analysis on the response under static loading is carred out. The equivalent dynamic wheel load method is adopted to calculate the dynamic response of the cable-stayed bridge.Through the response calculation of long-span cable-stayed bridge under 24 h random traffic loads, the fatigue performance of the cable is evaluated.Thirdly, the concept of the design CA traffic flow density is put forward, and the response of cable-stayed bridge design under the design density of traffic flow is calculated and compared with codes of China and other countries. Then, the brief analysis of the characteristics of each code and the transcendental probability of bridge response to standard value is conducted. The load effect of the design reference period is extrapolated by the principle of extreme statistics, and some factors are calculated based on the load effect, especially the uniformly distributed force and longitudinal reduction factor in the code are detailedly studied.