The global construction industry stands at a critical juncture, caught between the urgent demands of rapid urbanisation and the existential necessity of sustainable development. To address these demanding complexities of the twenty first century, engineers must think beyond traditional practices. This issue of Structures and Buildings highlights an increasing interest in additive manufacturing, material circularity and seismic resilience. The featured research emphasises that the future of our built environment depends on our ability to master interfaces – whether between printed layers of mortar, steel and recycled concrete, or adjacent vibrating structures.
Additive manufacturing (also known as three-dimensional (3D) printing) is a primary frontier in the current construction evolution. While 3D concrete printing offers unparalleled design flexibility and formwork-free construction, the resulting structures are inherently anisotropic. Seepim et al. (2026) address a ‘weak link’ of this technology: the interlayer bond strength. Their investigation reveals that the printing interval relative to the initial setting time is the primary governing factor for interface quality. Crucially, they demonstrate that while elevated temperatures accelerate early-age hydration, they also increase surface moisture loss, which can degrade bond performance at longer intervals. By proposing predictive models for interface normal and shear strengths, this work contributes to a necessary design-oriented framework to move three-dimensionally printed mortar from experimental investigations to real-life structural members.
The integration of recycled aggregate concrete (RAC) into composite systems is essential for managing construction and demolition waste. Oliveira et al. (2026) explore this in the context of partially encased composite beams. They found that a 50% replacement of natural coarse aggregate resulted in a peak load approximately 5% higher than that of the natural aggregate concrete specimen. This synergy between steel encasement and recycled materials mitigates the inherent stiffness reductions of RAC, proving that sustainability and performance are not mutually exclusive.
The efficacy of many composite construction systems rests on the integrity of shear connectors. Mao et al. (2026) provide deep insights into the flexural behaviour of profiled steel–concrete composite beams, demonstrating that stud spacing significantly impacts crack resistance and flexural strength. Their findings show that reducing the stud spacing can increase the cracking and ultimate loads by 31% and 17.5%, respectively.
Beyond material and sectional integrity, this issue addresses the broader requirement for seismic resilience. As building codes are updated, designers must simultaneously optimise strength and ductility. Chowdhury and Bhanja (2026) provide a timely evaluation of the second generation of Eurocode 2, developing axial load–moment interaction charts that span the entire stress range from pure compression to pure tension. Their work emphasises that utilising the strain hardening of steel reinforcement allows for more economical designs, improving moment capacity by roughly 10% with only marginal reductions in curvature ductility.
Resilience also requires innovation in prefabricated beam–column joints for high-rise buildings. Zhang et al. (2026) investigated concrete-filled circular steel tubular T-shaped column–composite beam frame joints, which are vital for maximising space in dense urban office buildings. Their study demonstrates that specimens loaded along the flange direction are significantly more resilient, resulting in higher energy dissipation and displacement ductility than those loaded along the web. This emphasises the need for meticulous orientation and joint design in assembled frame systems.
Finally, the interaction between structures during extreme events must be considered. Jiang et al. (2026) tackle the problem of seismic pounding in adjacent buildings through overload-protected viscous dampers. By integrating a friction-based mechanism that caps force transfer at an optimal friction force limit ratio, these devices prevent structural overloading while providing essential energy dissipation during moderate earthquakes. This performance-oriented approach ensures both serviceability and safety in complex architectural configurations.
Collectively, these six papers map out a sophisticated path for advanced structural engineering. They remind us that our task is not merely to build, but to design systems that are technically advanced, materially responsible and dynamically resilient. By mastering the interfaces – between layers, materials and buildings – we can construct a world that is both durable and sustainable. I invite you to delve into the technical depth of these contributions and join us in this vital discourse.
Dirar Samir
