Axial Shortening Compensation Strategies in Tall Buildings. A Case Study: The New Piedmont Government Office Tower

Axial shortening of columns and walls is inevitable in any reinforced concrete or hybrid steel–concrete structure. As the building increases in height, vertical members are subjected to large axial displacements, as they are cumulative over the height of the structure. The consequent differential length changes in the adjacent vertical members represent the so-called differential axial shortening phenomena and produce a distortion of the geometry of the structure that can seriously affect the horizontal elements, such as beams and slabs. In order to avoid the problems related to differential shortenings of the vertical members, the elastic and inelastic shortenings should be predicted and mitigated accurately and properly compensated for. The compensation can be obtained by adopting a compensation programme during the construction which adjusts the lengths of the vertical members with respect to the nominal values. The present work discusses a compensation procedure which applies a detailed modelling and incorporates the influence of construction sequences and stiffness changes in relation to time-dependent properties. The study refers to an interesting hybrid steel–concrete high-rise building which is to be built in Italy.