Parametric Studies on Differential Shortening Of Vertical Members in High-Rise R.C Building

At present, there is a growing demand for residential units and office suites in India, resulting in the construction of large number of high rise buildings. By far, reinforced concrete is the most widely accepted and used material in high rise structures. In addition to the gravity loads, lateral loads due to earthquake and wind are other loads that should be considered in such high-rise buildings. These lateral loads cause horizontal displacement (lateral drift) of these buildings. To control this lateral drift, it is necessary to provide very large column sizes. However, providing such large column sizes leads to uneconomical sections. Therefore, the trend followed these days is to provide a central core, with shear wall. These shear walls, in addition to lateral loads also resist larger axial loads. Due to the fact that shear walls are of larger size in comparison to the column, they undergo less compression in comparison to column under axial loads. This leads to differential shortening between the two adjacent vertical members. The conventional analysis method for tall buildings consider all loads being applied in a single step (one step), but in practice self-weight and part of live load are released on the building gradually as the construction progresses and therefore construction stage analysis using software E-TABS needs to be carried out.

In the present work, a parametric study is done on differential shortening of vertical members in tall R.C buildings. The parameters considered are varying the columns sizes, increasing storey height and grade of concrete. Comparison of various parameters such as beam moments and differential shortening and effect of spans using one step analysis and construction stage analysis is studied