Structural and aerodynamic couplings of wind-excited linked tall buildings

Abstract

There is a growing trend to link tall buildings in close proximity by connecting through horizontal structural links such as skybridges, skygardens, and even skypools. They are usually built to great heights in order to achieve a grand appearance, so wind-resistance is one of the primary concerns in design practice, particularly in typhoon-prone areas such as Hong Kong and Tokyo. Compared to wind-resistant design for a single isolated building, wind-resistant design for a linked building system (LBS) is much more complicated because of the link-induced structural coupling and the aerodynamic coupling. Therefore, this study investigates these two types of coupling systematically and how they affect the performance of LBSs subjected to wind loads. First, a simplified continuum beam model of the LBS is developed by modelling each building as a cantilever beam and the link as a spring-mass system, to investigate the link-induced structural coupling. The analytical solutions for the modal properties of the model are then derived. The effects of the linked-induced structural coupling on the modal properties of the LBSs are preliminarily examined by using these analytical solutions. A more advanced three-dimensional (3D) evaluation model is then developed for the LBS, to consider more structural details and wind-excited 3D vibrations of the LBS. Six types of mode shape are derived from the model and the effects of the link-induced structural coupling on the modal properties are examined comprehensively. Subsequently, the effects of the link properties (i.e., mass, location, axial stiffness, and bending stiffness) on the wind-induced responses of LBSs are examined comprehensively through the model. How the link properties affect the performance of wind-excited LBSs is investigated in detail and summarized. The aerodynamic coupling is investigated in terms of the inter-building and intra-building aerodynamic correlations of LBSs. Spatiotemporal wind pressure data measured from the wind tunnel tests are used to examine the two types of correlation. Results show that the wind-induced response of the LBS is related positively to the inter-building correlation coefficient between the generalized force components of the two buildings. Furthermore, because of the aerodynamic coupling, the intra-building aerodynamic correlation for LBSs differs considerably from that for the single building, especially for the correlation between along-wind and torsional force components. Finally, the combined effects of both structural and aerodynamic couplings on the performance of wind-excited LBSs are investigated comprehensively. It has been shown that for the same link, the wind-induced response of an LBS under different aerodynamic couplings shows significant differences. In general, the response is relatively small when gap distance ratio (S/B, where Sis the gap distance and B is width of the building) = 0.5 and 1.5, whereas the response is relatively considerable when S/B = 1. Additionally, two critical wind directions (i.e., 0° and 90°) are identified. Results show that in design of LBSs, both link-induced structural coupling and aerodynamic coupling can affect the performance of wind-excited LBSs significantly and should be carefully taken into account. To facilitate design of LBSs for wind-resistance, a set of design procedures and charts are provided. According to these procedures and charts, design of the link can be easily and fast achieved.

Date of Award	2015
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology