Analysis Of Stiffness And Strength Of Continuous Rigid Frame Bridge Based On Long-term Monitoring Information

Continuous rigid frame bridge keeps both the advantages of continuous beam bridge such as lack of joints and comfortable drive and T-rigid frame bridge such as no bearing and no system conversion. Continuous rigid frame bridge also has its unique advantage in economic indicators.However, continuous rigid frame bridge can be damaged because of material and structure natural aging, the increase of traffic, the creep and shrinkage, and the overload in the operation period. The phenomenon is part of bridges middle span deflect seriously and box girder webs crack easily because bridge permanent deformation increased. It affects the safety and durability of the bridge.Stiffness and strength of bridge are two indicators to assess its security performance.However,the strength index and stiffness index of the bridge are not easily acquired at the same time in daily detection and monitoring.If the relationship between strain and deflection of bridge can be found.The unknown factor can be calculated by the one which is known. So that the load capacity safety situation of the bridge structure can be assessed systematically from both aspects of strength and stiffness.This paper mainly carried out the following research work:① Starting from the basic definition of displacement and strain and the elastic principle of beam and flat section assumption, this paper found the inner link of displacement and strain, formed the deformation measurement method of beam bridge based on strain gauge. To calculate the deflection equation of the bridge, the method only need the strain data collected by strain monitoring points installed on the bridge instead of displacement measuring instrument and the deflection monitoring points.Then the real-time deflection of whole bridge can be obtained and the dynamic response of displacement can be formed.② In order to make the monitoring data and the theoretical calculation values analyzed under the same condition. Therefore, the change caused by each effect need to be separated from monitoring data. Based on the analysis of the composition and the influence factors of the long-term monitoring information of continuous rigid bridge.This paper achieve to separate creep effect, load effect and degradation effect effectively.③ Used a large number of long-term monitoring data and Pearson correlation coefficient means to analyze the swapping relation between bridge strength and stiffnessbased on studying the relevance of continuous rigid frame bridge’s strain data and deflection data during the monitoring period.Improved the envelope evaluation method of bridge calibration coefficient.④ Based on Longhe Bridge, to monitor the Security status parameters in the construction and operation period, strain sensors, deflection sensors and temperature sensors need to be installed in the initial construction period. Load test should be taken after the construction period.By using a large number of long-term monitoring data and load test data. The feasibility of the stiffness and strength reflection index mutual conversion method and the creep effect separation method of continuous rigid frame bridge are verified. The security assessment system based on envelope theory of Longhe Bridge is established at last.