Study On The Bearing Capacity Of Existing Bridge Piers With Scouring Of The River

Scouring of the river is one of the main factors of bridge disasters. Long-term scouring will cause damage to the existing bridge piers, and reduce the material properties and the effective bearing capacity. Bridge pier scour can also lead to empty basis, falling sharply on the bearing capacity of bridge foundation, and resulting in pile tilt or bridge collapse in severe cases. Therefore, the study on the bearing capacity of existing bridge piers with scouring of the river and the establishment of the bearing capacity analysis model of damaged piers have important theoretical significance and practical value on the bridge safety assessmentTaking the Hunan Xiangtan Zhubugang Xiangjiang River Bridge (XZXRB) which had been seriously scoured and hit by a ship loaded with sands as engineering background, with the aid of finite element software ANSYS, the effects of pier damage and the decline of embedded depth of foundation caused by the surrounding rivers on the bearing capacity of existing bridge piers were studied in this paper. The main work and conclusion are as follows:1. The scour mechanism of the bridge pier and research methods of scour depth was summarized. The evaluation theories and related systems of existing bridge bearing capacity were introduced, and the damage assessment method of bearing capacity of scoured piers was discussed.2. The XZXRB right pier10#which was most serious scoured was taken as the research object, and the space finite element analysis model of the pier10#was set up. According to the underwater detection data, the scour damage was simulated, and nonlinear analysis on the vertical ultimate bearing capacity was carried out. The calculation results indicated that, compared with the intact condition, the erosion damage caused by scour lead a loss of20%on the vertical bearing capacity of the pier10#.3. Based on the design materials and related testing reports, the space finite element analysis model of the whole bridge of the XZXRB was bulit to analyze the dynamic responses under different scour conditions and with ship-bridge collision. The change curves of the displacement and the stress of the top of the pier with different scour situations were obtained. On this basis, the effects of scour on the horizontal bearing capacity of existing bridge piers were studied.4. The calculation results of the whole bridge model showed that, when the scouring depth reached20%of the design buried depth, the impact stress of piers reached the tensile strength; when the scouring depth reached50%and in the case of a ship collision, the largest displacement of pier crown was close to the maximum allowed value. If the scouring situation continues to deteriorate, the horizontal bearing capacity of the bridge piers would be insufficient to resist the ship-bridge collision force, and it would pose a serious threat to the safety and stability of the whole bridge.