Study On Causes And Stability Safety Of The Pier Deviation Of Continuous Beam Bridge

In recent years,the construction of highways in China is booming.However,when conducting researches on the operation status of highway bridges,it is often found that there is a large longitudinal deviation on the handover pier top of the continuous beam bridge.It is also accompanied by damages such as the excess bearing slippage and circular cracks at the pier bottom,which greatly reduce the stability and bearing capacity of the pier structure,and can not fundamentally guarantee the security of the structure.Therefore,the study on causes and stability safety of the pier deviation of the continuous beam bridge provides an important reference value for the structural design,operation and maintenance of the bridge.This paper takes the Lijiapuzi Bridge located in the Huinan-Baishan Highway as the engineering background,and establishes a two-unit bridge model using the ABAQUS finite element analysis software.The causes of the handover pier top’s deviation are analyzed for both the bridge as a whole and the pier locally.At the same time,the stability and safety performances of the deviated pier are also analyzed from three aspects of pier stability,stress performance and damage performance.Firstly,the classification of the stability problems of the bridge structure,the finite element method of the stability analysis,and the stimulation method of the initial geometrical imperfections are introduced.The nonlinear stability analysis of the deviated pier is clarified.It is necessary to take the first-order buckling mode obtained by the eigenvalue buckling analysis as the pier structural form with initial geometrical imperfections,then the pier stability limit load is solved using ABAQUS based on the arc length method.Secondly,the basic principles of the finite element are introduced.The material constitutive relations of the ABAQUS bridge model is clarified.The deduction of important parameters of the concrete plastic damage model is stressed,and the contact properties of the sliding surfaces of the pot rubber bearings are analyzed in detail including contact interactions among the sliding surfaces,and the element types,etc.,to build the ABAQUS Lijiapuzi Bridge two-unit model.The above model is used to analyze the causes of the pier deviation.Using the ABAQUS two-unit model to analyze the pier top’s displacement of the bridge under the circumstances where the design effect exists and the bearing sliding surface is not horizontal,the result shows: the design effect will not do harm to the pier;also,when the bearing sliding surface is not horizontal,and considering the long-term temperature changes of the main beam during the actual operation phase,the pier top’s longitudinal displacement and the pier bottom’s tensile stress will increase rapidly at first,and will gradually stabilize after several cycles of increase and decrease of the temperature.Using ABAQUS pier model to analyze the effects of the pier body’s sunshine temperature difference load,initial geometrical imperfections,pier body’s stiffness,and bearing friction coefficient on the pier top’s longitudinal displacement,the result shows: the pier body’s sunshine temperature difference load has a great impact on the pier deviation;also,the initial geometrical imperfections will cause the pier top’s deviation during the operation phase,thus the construction process must be strictly controlled to avoid the occurrence of the initial geometrical imperfections;besides,both the pier body’s stiffness and the friction coefficient of the bearing sliding surface will have certain influences on the pier top’s longitudinal displacement.This means when designing the bridge,the degree of the pier deviation damage can be controlled by reducing the pier height,increasing the pier body’s section size,and selecting the bearings reasonably.Finally,using the ABAQUS pier model to analyze the stability and safety performance of the deviated pier from three aspects of pier stability,stress performance and damage performance.The result shows: with the gradual increase of the pier top’s longitudinal deviation,the ultimate bearing capacity and the stability safety factor of the pier will gradually decrease accordingly.When the pier top’s longitudinal deviation reaches 38 cm,the stability safety factor of the pier decreases by 37.6%.Although the stresses of the pier body are less than the allowed values as required,serious concrete tensile and compressive damages occur,in which the tensile damage factor has reached 0.94.It can be seen that the stability and safety performance of the deviated pier is poor.Effective control measures must be taken in a timely manner;besides,maintenance and reinforcement should be carried out.