Effect of the diaphragm conditions on the structural response of tunnel-form buildings

Tunnel-Form Buildings (TFBs) offer a rapid and cost-effective construction method for mass housing projects, particularly in low- to medium-rise structures. Despite their widespread use and favorable seismic performance, a lack of specific seismic design standards for TFBs persists. Moreover, the impact of diaphragm flexibility on their seismic behavior remains under-investigated, leading to uncertainties in structural design. The structural engineers often rely on general methods for reinforced concrete structures, which have proven inadequate. Given the substantial computation costs of TFBs, engineers are often tempted to consider the slabs as rigid diaphragms, whether rightly or wrongly. This study investigates the influence of diaphragm flexibility on the seismic response of two typical six-story TFB configurations employed in a large-scale housing project in Algeria. Utilizing validated finite element models, the structural behavior of these configurations under seismic loading was compared, taking into account both rigid and realistically modeled diaphragms. Linear and non-linear analyses are conducted to assess the impact of diaphragm flexibility on key performance parameters, including displacements, member forces, and energy dissipation mechanisms. The findings of this study contribute valuable insights for the seismic design and analysis of TFBs, providing a more accurate representation of their structural behavior and informing the development of improved design guidelines.