A Correlation between Theoretical and Actual Column Shortening and Lateral Sway in a Vertically Asymmetric High-Rise Concrete Building

Thumbnail Image
Journal Title
Journal ISSN
Volume Title
The British University in Dubai (BUiD)
The consideration of columns shortening in high-rise buildings becomes more complex and needs more attention when the building is vertically asymmetric. The inherent complexity is attributed to the dramatically unequally loaded vertical members due to mass shifting after the separation floor (the floor after which the plan is significantly reduced), which consequently leads to building rotation toward the higher side causing more lateral and vertical displacements. The gravity loads induced sway and settlement of a 360m height vertically asymmetric building in Dubai are investigated in this research. The columns and core walls elastic and time-dependent shortenings are predicted using the ACI 209R-92 model considering all the compensation measures taken, the construction method adopted, and the site conditions revealed during the construction of the tower. Sophisticated calculations including all the influencing factors of this model were performed using an Excel sheet to provide a simple interface for calculating the elastic and time-dependent columns shortening. The building was also analyzed by finite element method software, Etabs where the columns shortening and settlement were predicted using CEB-FIB 90 model for time-dependent effects which was built-in the software. The results of the two models were evaluated by comparing them to site survey readings conducted each five floors during the tower construction. It was found that both methods overestimated settlements in all floors compared to actual ones. Whilst the average overestimation of the developed Excel sheet based on the ACI 209R-92 model was 630%, Etabs analysis based on the CEB-FIB 90 model had more accurate results with average overestimation of 258%. The lateral sway induce by gravity load was predicted by the same Etabs model using two different analyses, linear and nonlinear staged construction analysis. The sway results of the two models where compared to each other to get a comprehensive overview of this behavior. Further investigation was done on a modified building model where the vertical asymmetry was removed and the building was re-analyzed by the two analyses again. The advantages and disadvantages of each analysis were provided. It was found that the linear analysis significantly overestimated the lateral sway for the original model, whereas the two analysis had close results for the modified model. The analyses results clearly evidenced that nonlinear staged construction analysis is essential to capture the real behavior of vertically asymmetric buildings.
high-rise concrete building, United Arab Emirates (UAE), asymmetric buildings