| With the rapid development of our national transportation enterprise and the urgent needs of the construction of the national economy, the traffic flow of highway bridges is increasing, and the overloading transportation phenomenon of all kinds of vehicle is increasingly serious, the requirements of load and traffic capacity for highway bridges is higher, It also makes that part of highway bridges have some potential safety hazard problems. Therefore, it has aroused widespread attention for the safety assessment and identification of highway bridges, and load test is the main method for evaluation of the overall carrying capacity of bridge structure.Long-span continuous rigid-frame bridge is a bridge type of strong spanning capacity, very economic and comfortable driving, it will be as the preferred bridge type across the deep groove and canyon in Shaanxi province and even in the western mountainous areas, it is dominant in the number of the grand bridge. However, there are significant differences about the distribution characteristics of traffic flow between on highway bridges, especially on long-span continuous rigid-frame bridge and on the general road(such as the car-following, light and heavy traffic lane channelization,heavy vehicles overtaking is beyond the scope of the bridge span, etc.). Therefore,when determining the related parameters values of vehicle load on the bridge, we should focus on combining the special vehicles operating of the using phase long-span continuous rigid-frame bridge to consider the joint probability distribution, that is the new traffic flow characteristics on the bridge. Furthermore, based on the new features of random traffic flow on highway bridge, this paper carried out the test load study of long-span continuous rigid-frame bridge.At present, static load test is the most widely used and most important method to evaluate the performance of bridge structure, so the static load test of the bridge structure is the main research object. We know that the core content of the bridge static test is the design control calculation and test load. And the control load and the test load are based on the vehicle as the main live load, therefore, the key of bridge test load is the study of vehicle loads.In this paper, it carried out the investigation and statistical analysis of the actual traffic flow of vehicle load typical section of Xi Yu highway in Shaanxi province, and with the help of Monte Carlo simulation method, MATLAB language programming and the method for generating joint random variables sampled sequence, it established the random vehicle load model of continuous rigid-frame bridge based on the joint distribution of weight and headway parameters. Selecting four long-span continuous rigid-frame bridges, considering the established model of vehicle load and calculating the most unfavorable effects of each control section, according to the loading efficiency of static load test(JTG/T J21-2011), it is concluded that the adjustment coefficient of the test vehicle load on the control section of each bridge, and it had the results of comparative analysis in various conditions.According to the vehicle load model considering the joint distribution of random traffic flow parameters in long-span continuous rigid-frame bridge, it provides some preference for the design load, the evaluation and detection of load test in long-span concrete beam bridges. In addition, the research results of the effect adjustment coefficient of the control section test load, which is helpful to the reasonable adjustment of the test vehicle load, then it carries on the load test of bridge structure,which more conforms to the actual traffic flow characteristic. Therefore,we can obtain a more objective and credible security identification results, which is beneficial to the maintenance, repair or reinforcement of the bridge structure in the later period of the targeted measures to ensure the safety operation of the bridge. |
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