Staged-construction shrinkage in high-rise reinforced concrete buildings

Shrinkage-induced vertical shortening in reinforced concrete (RC) columns and shear walls of high-rise buildings was investigated through staged-construction analyses using the fib Model Code 1990 implemented in two structural analysis programs. As a baseline reference, representative shortening under typical conditions (relative humidity (RH) of about 70%) for a 50-storey building is about 33 mm in columns and 30 mm in shear walls. In this study, parameter variations included RH (40–90%), building height (30, 40 and 50 storeys), concrete strength (C70/85, C60/75 and C50/60) and slab thickness (250, 300 and 350 mm). Lowering the RH from 90% to 40% increased the maximum shortening by ≈44% in columns and ≈49% in shear walls, while increasing the number of storeys from 30 to 50 increased mid-height column shortening by roughly 30%. The use of higher strength concrete (C70/85) reduced the maximum shortening by up to 18% and thicker slabs reduce it by ≈12% in columns and ≈9% in shear walls through enhanced diaphragm stiffness. Shortening was found to be concentrated in the upper–middle floors, and evolves rapidly during the early years, underscoring the need for staged analysis. Unlike previous studies, this work provides quantified parametric relationships that can support design applications. The findings offer practical guidance for serviceability assessment, façade alignment and construction-tolerance planning in tall RC buildings.