Study On Influence Of Bearing Capacity And Its Permissible Limits Of Simply Supported Girder Bridge Pier With Axis Deviation

The prestressed concrete simply supported girder bridge has many advantages,such as low self-weight,being suitable for factory prefabrication,mature technology,so it is widely used in small and medium span bridges.As an important part of bridge,bridge piers,in the construction process,often happen the axis deviation(verticality deviation)which exceeds the limit value of construction specification and acceptance standard due to misplaced or improper control,but in most cases,the bearing capacity of bridge pier can meet the requirements of design specification.The main reason for this situation is that the relevant norms and standards for bridge pier verticality restricitons are not differentiated between the bridge force,pier height and pier section size.To this end,this paper focuses on the influence of bridge pier axis deviation on its bearing capacity and the allowable deviation limit value.The main research contents are as follows:(1)For the factors affecting the verticality of bridge piers,based on the elastic stability analysis method,this paper proposes the representing method of displacement shape function of bridge piers with initial bending defects and initial eccentric defects.Based on the energy method,this paper deduces the elastic buckling load of bridge piers with construction defects caused by insufficient strength of bridge pier sections.The influence of defects on the bearing capacity of bridge piers is analyzed.(2)For the limiting value of bridge piers initial offset,this paper,taking the circular bridge pier of equal cross-section as the research object,explores the internal force and deformation law of bridge piers under the joint action of multiple loads with initial offset,second-order analysis method based on the elastic stability method and considering geometric nonlinearity.The equation of the permissible limit of bridge piers initial offset in satisfying the stable bearing capacity is derived;based on the current code,an algorithm for the permissible limit for bridge piers initial offset in meeting the compressive load bearing capacity of the normal section is proposed.(3)Through a large number of calculations and algorithm verification of the permissible limit for bridge piers initial offset,the relationship between the span diameter,pier cross-section size,pier height and the permissible limit for bridge piers initial offset is established,and the dividing height corresponding to the permissible limit for bridge piers initial offset meeting the stable bearing capacity and satisfying the compressive bearing capacity of normal section is given.