Chief Research Engineer
Daewoo E&C, Seoul
Deformation is fundamental and inevitable phenomenon in building structures, but it can be safely neglected in most buildings' structural analysis and design, thanks to the so-called Small Deformation Theory or Infinitesimal Strain Theory. For tall buildings, however, deformations accumulate due to the movements of all or part of the building, to the point that they sometimes pose critical issues during construction and service life. This presentation concerns a case study of the long-term movement of a 68-story office building currently under construction in Hanoi, Vietnam.
The building design is unique - a triangular hollow prism with three cores at its apexes - making the transfer of gravity load quite complicated. On each of two sides of the prism, three modules of 20-story mass are transferred to steel and reinforced concrete cores via massive steel transfer trusses. The complex construction sequence made predicting the building's movement formidable. Specially developed software for advanced construction-stage analysis was utilized to its full extent, so as to simulate the progressive accumulation of movement in the building structure. Differential axial shortening, lateral deviation from plumb, and large deflection of the transfer trusses were predicted for the construction and service life periods, and reasonable compensation measures were established to revert the movements and facilitate construction. Material tests on concrete elasticity, creep and shrinkage were also carried out to precisely capture the material’s long-term properties. A monitoring program using strain gauges and automatic data acquisition system is currently deployed.