Study On Some Issues In T-Girder Bridge Widening

According to the prestressed concrete T-Girder bridge in the reconstruction and extension projects of Beijing-Tianjin expressway,this paper researches on three issues in T-Girder bridge widening by grillage method:1)The additional force produced by difference of shrinkage and creep of old and new concrete is analyzed among new and old bridge connection main girders.The different effect by difference of shrinkage and creep is comparatively analyzed when old and new bridge girders are joint with girder or without.2)The effect of the superstructure by the difference of old and new bridge foundation subside is analyzed.3)The effect of the joint construction improving the performance of the concrete and the influence by different connection way is analyzed.The rusults show:the difference of concrete shrinkage and creep effects has great influence on the joint and boundary girders near joint.With the reduction of lateral rigiditi,The additional force produced by difference of shrinkage and creep of old and new concrete decreases.The rate of reduction is different,and the additional axial and transverse force by the difference of shrinkage is smaller and the additional vertical force is larger.It shows that the additional vertical force becomes larger with the increasing of lateral.The difference of old and new bridge foundation subside has great influence on the internal force and the deformation of the joint and boundary girders near joint.It shows that the additional force by the difference of old and new bridge foundation subside is undertaken by boundary girders near joint of old and new structure.Comparing with concrete joint poured with ordinary concrete,when concrete joint is poured with special properties,the largest stress is smaller.If from the view of force,the stress is larger when old and new structure is joint with rigid connection.But from the view of long perspective,if the old and new structure is connected with rigid connection,the lateral rigidity of the structure is larger and the structure is beneficial to undertake exterior load.