In order to facilitate the possibility of air rights development, a suitable type of structural form is needed to build over certain existing infrastructure or township.
The structural challenges of the mega-truss structure including the choice of an appropriate structural system, the appropriate practice of peripheral post-tensioning to simplify the stack-up staged structure and vibration mitigation required for structural response to exterior loadings including construction and expressway-induced vibration and wind are carefully studied.
Natural frequencies in the lateral transverse and vertical directions need to be raised to meet Eurocode specifications. Vibration study is important to the project because the vertical fundamental frequency of the functional bridging building is around 2Hz, which falls below the requirement of 5Hz stated in British Standard European Norm 1990. This implies that further comfort criteria verification due to potential vibration is required. Using validated finite element models using a theoretical solution from a simplified case, vibration analyses were performed on the whole mega truss including the stack-up building. The current research to date has focused on the basic structural form of the mega-truss. Future research will focus on resolving the above two major challenges.
This research delivers distinct academic originality and practical engineering value for sky-bridging mega-truss structures serving air-rights development above existing urban infrastructure. The primary novelty lies in the innovative Warren truss configuration integrated with internal bottom-chord post-tensioned cables, specially proposed to resolve the mid-span deflection bottleneck that dominates the design of long-span bridging mega-trusses—a critical limitation rarely systematically targeted in prior comparative studies of long-span structural systems. Differing from conventional internal prestressing or isolated external tendon reinforcement schemes, this work establishes a holistic design methodology combining peripheral external post-tensioning, which efficiently mitigates deflection, streamlines staged assembly construction sequences, and suppresses multi-source dynamic excitations including construction vibration, highway traffic vibration and wind loads simultaneously, filling the research gap of multi-performance coordinated control for overhead mega-truss skybridges. Additionally, the preliminary modal and frequency analysis of the post-tensioned mega-truss provides original dynamic characteristic data for vibration mitigation design of air-rights crossing structures. Practically, the proposed integrated external post-tensioning framework offers a replicable design reference for architects and structural engineers to implement horizontal connectivity above operational roads and urban zones, reducing material consumption, simplifying segmented construction, and improving structural robustness under combined static and dynamic actions, which carries tangible application value for high-density urban air-right exploitation and long-span overhead bridge structural optimisation.
