Development of a vibration based method to update axial shortening of vertical load bearing elements in reinforced concrete buildings

Axial shortening in reinforced concrete members in a building is usually predicted at design stage and updated during construction in order to mitigate adverse effects of differential axial shortening between members. This paper presents a novel procedure which uses vibration characteristics to update the elastic shortening of members at any stage of construction or service of the building. Towards this end, a relationship between the vibration characteristics using the dynamic stiffness and the elastic shortening using the static stiffness is first established. An approximate method to add the effects of creep and shrinkage, at that stage, is also proposed in the paper. The capability of the proposed procedure is demonstrated through its application to a 64 storey building having out riggers and belt systems.