Effects of Axial Shortening of Columns on Design and Construction of Tall Reinforced Concrete Buildings

Axial shortening of columns due to long term creep and shrinkage is inevitable in tall reinforced concrete buildings. However, calculation of exact values of axial shortening is not a straight forward task since it depends on a number of parameters such as the type of concrete, reinforcement ratio, and the rate and sequence of construction. All these parameters may or may not be available to the design engineer at the preliminary design stage of construction. Furthermore, long term shortening of columns could affect the horizontal structural members such as beams and floors and hence could affect the finishes and partitions. Therefore, a reasonable idea about the probable axial shortening could be important for construction engineers and project managers as well. In this study, the effects of construction sequence, rate of construction, and grade of concrete on axial shortening are determined based on a number of case studies covering 10–40 story range. These are presented as a set of guidelines so that the effect could be taken into account approximately, especially at the preliminary design stage and also during the construction phase.