Linked buildings (LBs) are joined by structural connections such as sky bridges, sky pools, or sky gardens. The two buildings of an LB system are usually not far from each other. As a result, the wind forces on each building of an LB system differ from those on a standalone building. Their wind loadings are affected by aerodynamic interference and need to be thoroughly examined. In addition, the two buildings vibrate in response to wind excitation when the buildings are joined by a link. The wind resistance aspect of the structural design of an LB system is complicated because of the structural and aerodynamic couplings.

First, this study investigates the aerodynamic characteristics of LBs. Wind pressure data on typical LBs with different gap distances between two buildings was...[ Read more ]

Linked buildings (LBs) are joined by structural connections such as sky bridges, sky pools, or sky gardens. The two buildings of an LB system are usually not far from each other. As a result, the wind forces on each building of an LB system differ from those on a standalone building. Their wind loadings are affected by aerodynamic interference and need to be thoroughly examined. In addition, the two buildings vibrate in response to wind excitation when the buildings are joined by a link. The wind resistance aspect of the structural design of an LB system is complicated because of the structural and aerodynamic couplings.

First, this study investigates the aerodynamic characteristics of LBs. Wind pressure data on typical LBs with different gap distances between two buildings was measured in a series of wind tunnel tests, and proper orthogonal decomposition (POD) analysis was then applied to identify pressure patterns and the associated excitation mechanisms. For wind direction α = 0^? (i.e., two buildings in a side-by-side arrangement and normal to wind direction), channeling in the first mode and vortex shedding in the second mode are correlated with different aerodynamic characteristics. For the wind direction α = 90^? (i.e., two buildings in a tandem arrangement in the wind direction), when gap distance is large, the pressure on the windward surface of the downstream building is positive because separated flows from the upstream building are reattached on the downstream building. Due to the reattachment, the gap distance is important for aerodynamic characteristics.

Furthermore, this study investigates the aerodynamic correlations between the wind forces on the individual buildings of an LB system. A positive aerodynamic correlation of the along-wind force with a large gap distance is smaller than those with a small gap distance. Conversely, the cross-wind forces do not show a similar relationship with gap distance; in fact, its correlation is further complicated by interference. When the aerodynamic correlation is negative, the link of the LB system contributes to a significant reduction in the responses. However, with the positive correlation, the link has no effect on the responses.

This study also investigates flow patterns around an LB, using velocity- and vorticity-based POD analysis on particle image velocimetry data. Results show that for α = 0^?, a single vortex street exists in the wake of the two buildings in the first mode and a biased flow exists in the gap when gap distance is small in the second mode. For a large gap distance, in contrast, two independent bluff bodies are observed in the first mode and a gap flow parallel to the wind is noted in the second mode. Vorticity-based POD shows a jet-like accelerated gap flow with small gap distance in the first mode and vortex shedding on both the inner and outside surfaces with large gap distance in the second mode. For α = 90^?, stagnant flow in the gap with small gap distance and shear layer reattachment to the downstream building with large gap distance are observed in most modes. Vorticity-based POD analysis identifies either small or large vortices, depending on gap distance, in the wake of the two buildings in different modes.

Finally, this study presents the optimal location and properties (e.g., mass and stiffness) of a link for an LB system. The objective of this study is to minimize not only the lateral wind-induced displacement responses but also the lateral wind-induced acceleration responses of LB systems. A genetic algorithm and a 3-dimensional analytical model were then used to determine the optimal link location and the properties that would minimize the two wind-induced responses. The results show that adding mass in the link tends to increase the LBs’ displacement responses but decrease their acceleration responses, and it is optimal to place the link between 70% and 100% (i.e., top) of the buildings’ height. As the link moves from 70% of the buildings’ height to 100%, the acceleration response decreases in general, but the displacement response increases. Additional link stiffness, on the other hand, generally decreases both responses, but this additional stiffness does not need to be very large. The optimal gap distance should be half of the breadth of the building.