A Correlation between Theoretical and Actual Column Shortening and Lateral Sway in a Vertically Asymmetric High-Rise Concrete Building
Loading...
Date
2016-11
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
The British University in Dubai (BUiD)
Abstract
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.
Description
Keywords
high-rise concrete building, United Arab Emirates (UAE), asymmetric buildings