Preliminary guidelines on the design of cable-net stabilized high-rise towers

Abstract

The starting point of the thesis relates to the “Rotterdam Mountain” Project, envisioned by the Rotterdam Dreamers, which proposes an artificial mountain in the otherwise flat landscape of the Netherlands, supported by a cable network that is spanning between multiple high-rise towers. This network has the double function of supporting the weight of the mountain and connecting and stabilizing the towers. With the “Rotterdam Mountain” Project as a starting point, the thesis aims to investigate the structural feasibility and performance of a new typology for the design of high-rise towers, where a cable network interconnects and stabilizes them. The goal of the thesis is to investigate the design of such a system with respect to relevant parameters, as the relative position of the cable-net (RPC) or the spacing between towers (SBT). Such, a core system to which the cable-net is connected is used throughout the thesis. To understand the relative influence of different parameters, a parametric approach (in Grasshopper) is used, that allows for a rapid change of the initial properties of the system. The Grasshopper script is linked to the Robot Structural Analysis (RSA) software, where a non-linear analysis is performed. The outputs of the RSA analysis refer to both the serviceability limit state and ultimate limit state, as both the core and cable-net are designed to meet the stability and strength requirements imposed by the Eurocode. Based on the Eurocode checks, conclusions are drawn on the preliminary design of the system, by identifying multiple design zones with respect to the two relevant parameters: a zone where the stability of the core is governing (for a SBT of up to 90 meters, and an RPC of up to ~0.6), a zone where the strength of the core is governing (for a SBT higher than 90 meters or an RPC higher than ~0.6), or a zone where the influence of the cable-net is negligible (for an RPC lower than ~0.1). Conclusions are further drawn on the performance of the system, by comparing it to the simple core and outrigger systems. It is observed that the proposed core + cable-net system performs (at least) as good in terms of stability and strength with less material usage. A concrete weight reduction of the core of up to 50% is observed when compared to the simple core and a steel weight reduction of up to 20% is observed when compared to the outrigger. From an economic point of view, preliminary calculations have shown a reduction of the total weight of the structure of up to 14%, due to the increase in slenderness when the cable-net is placed. This is equivalent to a number of up to 5 extra floors that can be constructed with the same amount of material. With these remarks in mind, it is concluded that, based on this preliminary study, the cable-net stabilized towers can pose a feasible alternative to the design of high-rise towers, and they can be efficiently used for the ambitious “Rotterdam Mountain” project.