Topology Optimisation of Reinforced Concrete Transfer Structures in Tall Buildings: Original Frameworks for Nigerian Urban High-Rise Context

Transfer structures in tall mixed-use buildings must redistribute large gravity and lateral loads across irregular column arrangements, and their design represents one of the most structurally consequential and materially intensive decisions in high-rise structural engineering. Conventional design approaches for transfer structures rely on engineer experience and iterative manual methods that rarely achieve structural efficiency, motivating the application of topology optimisation to identify optimal material distributions within transfer zone volume envelopes. This study develops original frameworks for applying topology optimisation to the design of reinforced concrete transfer structures in tall buildings, calibrated to the construction and material constraints of Nigerian urban high-rise development in Lagos and Abuja in the South West and North Central geopolitical zones. A multi-objective topology optimisation formulation is developed that simultaneously minimises strain energy and reinforcement volume while enforcing constructability constraints including minimum member dimensions, reinforcement placement feasibility for Nigerian construction practice, and formwork geometry realisability. The optimisation framework is implemented in a MATLAB-based finite element environment incorporating solid isotropic material with penalisation and bi-directional evolutionary structural optimisation methods. Four building configurations representing different column offset ratios and storey height-to-transfer depth ratios are investigated, generating optimised transfer structure topologies for each. Results demonstrate that topology-optimised transfer walls achieve material savings of 28 to 39 percent relative to conventional flat transfer plate designs of equivalent structural performance, without increasing storey height. A design procedure translating continuous topology density fields into discrete reinforced concrete member layouts compatible with Nigerian construction practice is proposed as the original practitioner-facing output. Keywords: topology optimisation, transfer structures, tall buildings, reinforced concrete, structural efficiency.