Analysis method of internal force distribution on composite section for arch bridge strengthening

It's a common method to strengthen arch bridges by enlarging the section of main arch ring. The composite section mechanically belongs to two-stage loading composite structure, which creates difficulties for easy evaluation of bearing capacity of the new structure. Based on assumption of plane section, an internal force distribution formula on the composite section was deduced. In terms of different stages, the internal force was superimposed for both the old and the new section separately. Meanwhile, the new structure load-bearing capacity was checked. The analysis method has been applied in the strengthening design of arch bridges.